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Bollani, Monica. "Self-assembled monolayer (SAM) sensors realisation on Si (001) : surface modification, film growth, SAM and sensor characterisation." Aix-Marseille 3, 2000. http://www.theses.fr/2000AIX30072.
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The aim of this thesis is to report the results of an investigation aimed at exploiting synthetic methods to graft organic molecules onto (001) Si as well as at evaluating the applicability of SAM docking in the development of nanodevices. The target of this dissertation is to study a new nucleophylic reaction to bond directly the organic molecules at the surface. In the first part of this work we have focused onto silicon surface preparation. We have pointed out how the RCA cleaning method results in a modification of the structure of the first atomic layers of Si. We have demonstrated by HRTEM and EELS studies that the change of the lattice spacing is related to the subsequent Si oxidation that is known to occur by inward diffusion and insertion of oxygen in bond-centred positions in crystalline silicon. Such a process is favoured by the strain field due to the surface roughening which is characteristic of alkaline etches. To activate the surface toward chemical grafting reactions we have developed a method leading to bromine termination of the surface. This allowed to form an array of aromatic rings bonded through a covalent Si-C bond (i. E. Not implying oxygen bridges) by nucleophilic addition onto the Si-Br surface bond. We have evaluated the bromine termination and the surface reconstruction by Auger, FTIR and LEED analyses. .Ce travail porte sur l'investigation et la recherche des methodes du syntesis pour lier à la surface du Si (001) des monocouches organiques. Nous avons évalué l'applicabilité de ces systèmes pour le développement du nano-dispositif dans le domaine du détecteurs. La première partie de cette thèse regarde la préparation de la surface : on a évalué comment la methode du nettoyage (RCA) utilisée pour éliminer la contamination à la surface détermine une modification sur la structure des premières couches du silicone. Par HRTEM et EELS on a demostré que la variation de la distance des paramètres réticulaires des première couches, c'est dû au passage d'oxidation nommé APM qui permit la diffusion et l'insertion du 0 dans le volume du Si. .
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Wu, Jun. "Surface Modified Electrodes and Their Reactivity." Case Western Reserve University School of Graduate Studies / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=case1144448160.
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Ticha, Lawrence Awa. "Development of amperometric biosensor with cyclopentadienylruthenium (II) thiolato schiff base self-assembled monolayer (SAM) on gold." Thesis, University of the Western Cape, 2007. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_5394_1341319478.
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A novel cyclopentadienylruthenium(II) thiolato Schiff base, [Ru(SC6H4NC(H)C6H4OCH2CH2SMe)(&eta5-C2H5]2 was synthesized and deposited as a selfassembled monolayer (SAM) on a gold electrode. Effective electronic communication between the Ru(II) centers and the gold electrode was established by electrostatically cycling the Shiff base-doped gold electrode in 0.1 M NaOH from -200 mV to +600 mV. The SAMmodified gold electrode (Au/SAM) exhibited quasi-reversible electrochemistry. The integrity of this electro-catalytic SAM, with respect to its ability to block and electro-catalyze certain Faradaic processes, was interrogated using Cyclic and Osteryoung Square Wave voltammetric experiments. The formal potential, E0', varied with pH to give a slope of about - 34 mV pH-1. The surface concentration, &Gamma
, of the ruthenium redox centers was found to be 1.591 x 10-11 mol cm-2. By electrostatically doping the Au/SAM/Horseradish peroxidase at an applied potential of +700 mV vs Ag/AgCl, a biosensor was produced for the amperometric analysis of hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide. The electrocatalytic-type biosensors displayed typical Michaelis-Menten kinetics with their limits of detection of 6.45 &mu
M, 6.92 &mu
M and 7.01 &mu
M for hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide respectively.
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Gül, Semra Okur Salih. "Development of nanopatterns on self assembled monolayer (sam) organic films using scanning probe microscope (spm) nanolithography techique/." [s.l.]: [s.n.], 2006. http://library.iyte.edu.tr/tezler/master/malzemebilimivemuh/T000541.pdf.
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Thesis (Master)--İzmir Institute Of Technology, İzmir, 2006Keywords: Atomic force microscope, self assembled monolayer organic films, nanolithografy Includes bibliographical references (leaves. 109-112).
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Cheng, Nan. "The Development of Photosensitive Surfaces to Control Cell Adhesion and Form Cell Patterns." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23248.
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Cell adhesion is the first step of cell response to materials and the extracellular matrix (ECM), and is essential to all cell behaviours such as cell proliferation, differentiation, migration and apoptosis for anchor-dependent cells. Therefore, studies of cell attachment have important implications to control and study cell behaviours. During many developed techniques for cell attachment, the manipulation of surface chemistry is a very important method to control initial cell attachment. To control cell adhesion on a two-dimensional surface is a simple model to study cell behaviours, and is a fundamental topic for cell biology, tissue engineering, and the development of biosensors. From the engineering point of view, the preparation of a material with controllable surface chemistry can help studies of cell behaviours and help scientists understand how surface features and chemistry influence cell behaviours. During the fabrication, the challenge is to create a surface with heterogeneous surface properties in the micro scale and subsequently to guide cell initial adhesion. In order to control cell adhesion in a spatial and temporal manner, a photochemical method to control surface chemistry was employed to control the surface property for cell adhesion in this project. Two photocleavable derivatives of the nitrobenzyl group were tried on two types of surfaces: a model self-assembled monolayer (SAM) with alkanethiol-gold surface and biodegradable chitosan. Reactive functional groups on two different surfaces can be inactivated by covalent binding with these photocleavable molecules, and light can be further introduced into the system as a stimulus to recover their reactivity. By simply applying a photomask with diffe
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Rapisarda, Alessandro. "Novel self-assembled monolayer (SAM) based on calix[n]arenes for application as chemical sensors and optical devices: synthesis, studies and applications." Doctoral thesis, Università di Catania, 2013. http://hdl.handle.net/10761/1281.
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The vast majority of chemical sensors contain a chemically sensitive layer for analytes detection coupled with a transducer which transforms this interaction in a readable signal. It is well-known that calixarenes are used for the molecular recognition of ions, amino acids, hormones, sugars, peptides, nucleic acids, and proteins, which are fundamental substrates in biological and artificial processes. We developed new calix[n]arene based systems that are not only stable but are also capable of molecular recognition towards amino acids once assembled on the gold surface. By suitable modification, the system could become a potential receptor for biologically important amines and proteins.
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Gambarin, Alessandro. "Studio del clustering del monostrato di molecole organiche passivanti nanoparticelle d'oro." Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423778.
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The development of nanosystems or so-called "molecular machines" is a great challenge for modern chemistry. This acute scientific effort stems from the multiplicity and significance of the potential application fields, which could range from analytes sensing and biomedicine, to the design of "artificial enzymes", rationally designed supramolecules which possess intrinsic catalytic activity. A top-down approach implies the complete understanding of the mechanisms that govern the processes of formation, assembly and rearrangement of these supramolecules, in order to control and steer them in the desired direction.
Metal nanoclusters stabilized by an organic monolayer (SAM, Self-Assembled Monolayers) stand out into the varied review of nanomaterials, because of their particular features, which address them as one of the main platforms on which to shape the concept of molecular machine. The SAM which stabilize the metallic nucleus is nothing more than a supramolecular structure formed by molecules displaying special functional groups, which self-assemble upon the metallic surface, potentially reaching an high spatial organization. The possibility to change at will the chemical structure of adsorbates implies a considerable flexibility in modulating the physicochemical properties of these nanomaterials: to date gold nanoparticles (AuNPs) stabilized by alkyl and functionalized thiols, such as nucleic acids, oligopeptides, polysaccharides have been synthesized. Moreover, mixed SAM AuNPs synthesis has been reported in literature: in this case the properties of different types of adsorbates could be mediated, or possess synergistic activity.
In this Ph.D. Thesis several research projects have been developed, each one relating to specific properties and applications of omoligand and mixed monolayer AuNPs. Several experimental evidences reported in literature suggest that in mixed monolayer AuNPs, adsorbates could undergo phase segregation processes: in the first part, mixed monolayer gold nanoparticles stabilized by photoresponsive groups containing derivatives (azobenzene and pyrene) have been synthesized and characterized, in order to correlate the optical properties of the samples with the topological arrangement of adsorbates into the monolayer.
In the second part, the exposition focus upon nanoparticle gold core packing and monolayer’s self-assembly mechanisms in Peng-Scrimin synthetic process, the one commonly used in our laboratory. This study has been considered useful in order to increase accuracy of mixed monolayers synthesis and to explain the occurrence of "sorting" phenomena (asymmetric distribution of adsorbates onto metallic nuclei into the sample). The properties of some functionalized monolayers have also been investigated through exchange experiments, initially monitored by means of fluorescence emission spectroscopy and then by 1H- NMR, in order to justify experimental evidences of phase segregation recently published by the research group in which I spent the Doctorate .
In the third part, supramolecular interaction between mixed monolayer AuNPs (stabilized by a pyrene derivative co-adsorbed with a phosphorylcholine one) and single-walled carbon nanotubes (SWNTs), pristine (non-functionalized) and PEG-ylated (conjugated with polyoxyethylene chains), has been investigated, and a protocol for their complexation to the obtaining of nanocomposites has been developedLa costruzione di nanosistemi o cosiddette “macchine molecolari” rappresenta una grande sfida per la chimica moderna. L’intenso sforzo scientifico per il raggiungimento di questo obiettivo deriva dalla molteplicità e rilevanza dei potenziali campi applicativi, che potrebbero spaziare dal sensing di analiti, alla biomedicina, alla progettazione di “enzimi artificiali”, supramolecole progettate razionalmente in modo da possedere attività catalitica intrinseca. Un design a tavolino implica tuttavia la totale comprensione dei meccanismi che governano i processi di formazione, assemblaggio e riarrangiamento di queste supramolecole, in modo da poterli controllare e indirizzare nella direzione voluta. I nanoclusters metallici passivati da monolayers organici (SAM, Self Assembled Monolayers) presentano peculiari caratteristiche che li individuano, nel variegato panorama dei nanomateriali, come una delle principali piattaforme sulle quali plasmare il concetto di macchina molecolare. I SAM che stabilizzano i nuclei metallici non sono altro che strutture supramolecolari costituite da molecole dotate di particolari gruppi funzionali affini alla superficie del nanocluster, che si autoassemblano raggiungendo potenzialmente un'elevata organizzazione spaziale. La possibilità di modificare a piacimento la struttura chimica degli adsorbati comporta una notevole elasticità nel modulare le proprietà fisico chimiche di questi nanomateriali: sono ad oggi state sintetizzate nanoparticelle d’oro (AuNPs) stabilizzate da tiolati alchilici e funzionalizzati, acidi nucleici, oligopeptidi, polisaccaridi. E’ stata inoltre ampiamente riportata in letteratura la sintesi di AuNPs con SAM a composizione mista, in cui le proprietà dei differenti tipi di adsorbati vengono tra loro mediate, o possiedono attività sinergica. In questa Tesi di Dottorato vengono sviluppati diversi progetti di ricerca che riguardano specifiche proprietà e applicazioni di AuNPs stabilizzate da monostrati a composizione unitaria e mista. Numerose evidenze sperimentali riportate in letteratura inducono a supporre che in SAM a composizione mista siano possibili processi di segregazione di fase degli adsorbati. Nella prima parte sono state perciò sintetizzate e caratterizzate AuNPs stabilizzate da derivati tiolici contenenti gruppi fotoresponsivi (azobenzenico e pirenilico) in monostrati a composizione mista, nel tentativo di correlare le proprietà ottiche dei campioni con le modalità di impaccamento del monostrato. Nella seconda parte sono state approfondite le modalità di formazione del SAM nel processo sintetico Peng-Scrimin, al fine di aumentare il livello di accuratezza nella sintesi di monostrati misti e di spiegare l’occorrenza dei fenomeni di “sorting” (distribuzione asimmetrica degli adsorbati sui nuclei metallici in fase di sintesi). Sono state inoltre investigare le proprietà di alcuni monostrati funzionalizzati, tramite esperimenti di scambio monitorati tramite spettroscopia di emissione di Fluorescenza e 1H-NMR, al fine di giustificare alcune evidenze sperimentali di segregazione di fase recentemente pubblicate dal gruppo di ricerca nel quale ho svolto il Dottorato. Nella terza parte è stata investigata l’interazione supramolecolare che si verifica tra AuNPs a monostrato misto stabilizzate da un derivato tiolico del pirene co-adsorbito con un derivato tiolico della fosforilcolina, e nanotubi di carbonio a parete singola (SWNTs) pristini (non funzionalizzati) e PEGilati (coniugati con catene poliossietilenglicole), ed è stato messo a punto un protocollo per la loro complessazione e l’ottenimento di nanocompositi
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Besharat, Zahra. "Adsorption of molecular thin films on metal and metal oxide surfaces." Doctoral thesis, KTH, Materialfysik, MF, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-195613.
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Metal and metal oxides are widely used in industry, and to optimize their performance their surfaces are commonly functionalized by the formation of thin films. Self-assembled monolayers (SAMs) are deposited on metals or metal oxides either from solution or by gas deposition. Thiols with polar terminal groups are utilized for creating the responsive surfaces which can interact electrostatically with other adsorbates. Surface charge effects wetting and adhesion, and many other surface properties. Polar terminal groups in thiols could be used to modify these factors. Mixed SAMs can provide more flexible surfaces, and could change the resulting surface properties under the influence of factors such as pH, temperature, and photo-illumination. Therefore, in order to control these phenomena by mixed polar-terminated thiols, it is necessary to understand the composition and conformation of the mixed SAMs and their response to these factors. In this work, mixtures of thiols with carboxylic and amino terminal groups were studied. Carboxylic and amino terminal groups of thiol interact with each other via hydrogen bonding in solution and form a complex. Complexes adsorb to the surface in non-conventional orientations. Unmixed SAMs from each type, either carboxylic terminated thiols or amino terminated thiols are in standing up orientation while SAMs from complexes are in an axially in-plane orientation. Selenol is an alternative to replace thiols for particular applications such as contact with biological matter which has a better compatibility with selenol than sulfur. However, the Se-C bond is weaker than the S-C bond which limits the application of selenol. Understanding the selenol adsorption mechanism on gold surfaces could shed some light on Se-C cleavage and so is investigated in this work. Se-C cleavage happens in the low coverage areas on the step since atoms at steps have lower coordination making them more reactive than atoms on the terraces. Another area where the self-assembly of molecules is of importance is for dye sensitized solar cells, which are based on the adsorption of the dye onto metal oxides surfaces such as TiO2.The interface between the SAM of dye and the substrate is an important factor to consider when designing dyes and surfaces in dye sensitized solar cells (DSSCs). The quality of the self-assembled monolayers of the dye on the TiO2 surface has a critical influence on the efficiency of the DSSCs. Creation of just a monolayer of dye on the surface could lead to an efficient current of photo-excited electrons to the TiO2 and degeneration of the dye by redox. This work, T-PAC dye showed island growth with some ad-layer that is not in contact with the surface, whereas the MP13 dye adsorption is laminar growth. Cuprite (Cu2O) is the initial and most common corrosion product for copper under atmospheric conditions. Copper could be a good replacement for noble metal as catalysts for methanol dehydrogenation. Knowledge about the structure of Cu2O(100) and Cu2O(111) surfaces could be used to obtain a deeper understanding of methanol dehydrogenation mechanisms with respect to adsorption sites on the surfaces. In this work, a detailed study was done of Cu2O(100) surface which revealed the possible surface structures as the result of different preparation conditions. Studies of the structure of Cu2O(100) and Cu2O(111) surfaces show that Cu2O(100) has a comparatively stable surface and reduces surface reactivity. As a consequence, dehydrogenation of methanol is more efficient on the Cu2O(111) surface. The hydrogen produced from methanol dehydrogenation is stored in oxygen adatom sites on both surfaces.QC 20161107
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Eder, Katja Daniela. "Surfaces and interfaces in nano-scale and nano-structured materials." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17217.
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In this thesis, advanced characterisation methods, including atom probe tomography (APT) and transmission Kikuchi diffraction (TKD) were employed to study surface and interfaces in a range of nano-scale and nano-structured materials. These techniques were used to measure solute segregation towards grain boundaries and to explore the relationship between grain boundary segregation and grain boundary mobility. APT was also used to characterise the structure of nanoparticles used as catalysts, and the adsorption behaviour of sulphur on catalytic surfaces, to gain more information about the structure-activity relationships, and deactivation processes. This research included the development and improvement of new and existing APT sample preparation techniques, conducting the experiments, and data analysis. The first part of this thesis is concerned with nanocrystalline alloys processed by severe plastic deformation. In the second part the exceptional hardening of an 316L austenitic steel during annealing was also investigated using APT. This thesis also concentrated on the study of nanoparticles for catalysis via APT. Systematic investigations of different APT sample preparation techniques were performed in order to find a way of producing reproducible and reliable specimens. Different acquisition parameters, substrates and coatings were tested to improve the APT data quality. Experiments were conducted in which needles were dipped in thiophene. Here the aim was to investigate the phenomenon of sulphur poisoning by using APT to investigate how thiophene bonds with different metal substrates. A glovebag setup was designed for the transfer of APT samples in a controlled environment, to avoid oxidation of the samples. This allowed the comparison of oxidised and un-oxidised specimen states. In the last part of this thesis, the accuracy of crystallographic information contained within APT datasets was verified for the first time by comparing the datasets to TKD measurements.
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Belgardt, Christian. "Herstellung mikrostrukturierter OTS-Monolagen auf Siliziumoxidoberflächen." Master's thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-86379.
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Die Oberflächeneigenschaften eines Festkörpers können mit Hilfe dünner, durch Selbstorganisation gebildeter Molekülschichten aus Alkoxysilan-Molekülen gezielt verändert werden. Mikrostrukturierte selbstangeordnete Monolagen (SAM) können für die Anwendung in Bauelementen aus organischen Halbleitern von großem Interesse sein. Mikrokontaktdruck und Photolithographie sind zwei etablierte Verfahren, die jedoch Vorlagen und Masken zur Strukturierung benötigen. Dadurch entstehen bei häufig wechselnden Strukturen nicht zu vernachlässigende Rüstzeiten und Kosten. In der vorliegenden Arbeit wird die Erzeugung lateral strukturierter Schichten von Octadecyltrichlorsilan (OTS) auf Siliziumoxidoberflächen am konkreten Beispiel zweier alternativer, sowohl maskenloser als auch kontaktloser Methoden demonstriert: (i) Tintenstrahlverfahren als rein additive Strukturierung, und (ii) laserinduzierte, photothermische Desorption als subtraktive Strukturierung einer OTS-SAM . Für das Tintenstrahldruckverfahren wird an einem Kontaktwinkelmessgerät eine Methode zur Beobachtung und Auswertung der Tropfenverdampfung implementiert und ein Modell für kleine Tropfen entwickelt. Für die subtraktive Strukturierung werden an einem selbst entwickelten Versuchsaufbau die leistungs- und geschwindigkeitsabhängige Strukturbreite untersucht. Die Ergebnisse der beiden Technologieansätze werden verglichenWith help of thin layers of alkoxysilane molecules formed by self-assembly, the surface properties of solids can be controlled. Microstructured self-assembled monolayers (SAMs) are interesting for applications in components based on organic semiconductors. Two established technologies for the structuring of molecular monolayers are microcontact printing and photolithography, for which templates and masks need to be structured. In this way, setting times and costs are high if variable patterns have to be structured. In this work, the fabrication of laterally structured monolayers from octadecyltrichlorosilane (OTS) is demonstrated for two examples of alternative, both template-free and maskless technologies: (i) inkjet as a purely additive method, and (ii) photothermal laser desorption as a subtractive structuring of an OTS-SAM. For the inkjet technology, a method for the observation and analysis of the evaporation of a droplet is implemented at a goniometer and a mathematical model for small inkjet droplets is extrapolated, For the subtractive laser structuring, the achievable patterning resolution is investigated as a function of laser intensity and scanning speed. The results of both technological approaches are compared
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Rundqvist, Jonas. "Nanometer Scale Protein Templates for Bionanotechnology Applications." Doctoral thesis, KTH, Physics, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-530.
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Nanofabrication techniques were used to manufacture nanometer scale protein templates. The fabrication approach employs electron beam lithography (EBL) patterning on poly(ethylene glycol) (PEG) thiol (CH3O(CH2CH2O)17NHCO(CH2)2SH) self-assembled monolayers (SAM) on Au. The PEG SAM prevented protein surface adhesion and binding sites for protein were created in the SAM by EBL. Subsequent to EBL, the patterns in the PEG SAM were backfilled with 40-nm NeutrAvidin-coated fluorescent spheres (FluoSpheres). The spontaneous and directed immobilization of the spheres from a solution to the patterns resulted in high resolution protein patterns. The FluoSpheres could be arranged in any arbitrary pattern with ultimately only one or a few FluoSpheres at each binding site.
Growth dynamics and SAM morphology of PEG on Au were studied by atomic force microscopy (AFM). PEG SAMs on three types of Au with different microstructure were examined: thermally evaporated granular Au and two types of Au films produced by hydrogen flame annealing of granular Au, Au(111) and "terraced" Au (crystal orientation unknown). The different Au surfaces' substructure affected the morphology and mechanical properties of the PEG SAM. On Au(111), AFM imaging revealed monolayer formation through three distinct steps: island nucleation, island growth, and coalescence. The fine-structure of the SAM revealed dendritic island formation - an observation which can be explained by attractive intermolecular interactions and diffusion-limited aggregation. Island growth was not observed on the "terraced" Au.
AFM studies of EBL patterned PEG SAMs on Au(111) revealed two different patterning mechanisms. At low doses, the pattern formation occurs by SAM ablation in a self-developing process where the feature depth is directly dose dependent. At higher doses electron beam induced deposition of material, so-called contamination writing, is seen in the ablated areas of the SAM. The balance between these two mechanisms is shown to depend on the geometry of the pattern.
In addition to PEG SAMs, fibronectin monolayers on SiO2 surfaces were patterned by EBL. The areas exposed with EBL lose their functionality and do not bind anti-fibronectin. With this approach we constructed fibronectin templates and used them for cell studies demonstrating pattern dependent cell geometries and cell adhesion.
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Ericsson, Emma. "Biosensor surface chemistry for oriented protein immobilization and biochip patterning." Licentiate thesis, Linköpings universitet, Sensorvetenskap och Molekylfysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-88102.
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This licentiate thesis is focused on two methods for protein immobilization to biosensor surfaces for future applications in protein microarray formats. The common denominator is a surface chemistry based on a gold substrate with a self-assembled monolayer (SAM) of functionalized alkanethiolates. Both methods involve photochemistry, in the first case for direct immobilization of proteins to the surface, in the other for grafting a hydrogel, which is then used for protein immobilization. Paper I describes the development and characterization of Chelation Assisted Photoimmobilization (CAP), a three-component surface chemistry that allows for covalent attachment and controlled orientation of the immobilized recognition molecule (ligand) and thereby provides a robust sensor surface for detection of analyte in solution. The concept was demonstrated using His-tagged IgG-Fc as the ligand and protein A as the analyte. Surprisingly, as concluded from IR spectroscopy and surface plasmon resonance (SPR) analysis, the binding ability of this bivalent ligand was found to be more than two times higher with random orientation obtained by amine coupling than with homogeneous orientation obtained by CAP. It is suggested that a multivalent ligand is less sensitive to orientation effects than a monovalent ligand and that island formation of the alkanethiolates used for CAP results in a locally high ligand density and steric hindrance. Paper II describes the development of nanoscale hydrogel structures. These were photografted on a SAM pattern obtained by dip-pen nanolithography (DPN) and subsequent backfilling. The hydrogel grew fast on the hydrophilic patterns and slower on the hydrophobic background, which contained a buried oligo(ethylene glycol) (OEG) chain. Using IR spectroscopy, it was found that the OEG part was degraded during UV light irradiation and acted as a sacrificial layer. In this process other OEG residues were exposed and acted as new starting points for the self-initiated photografting and photopolymerization (SIPGP). A biotin derivative was immobilized to the hydrogel density pattern and interaction with streptavidin was demonstrated by epifluorescence microscopy.
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Cheadle, Edward Martin. "Characterisation of self-assembled monolayers." Thesis, University of Leeds, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250878.
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Delafosse, Gregory. "Auto-assemblage de fullerènes C60 sur surfaces d'oxyde de silicium et d'or fonctionnalisées NH2." Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10221/document.
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Au cours de ce travail nous avons étudié la réalisation de couches moléculaires d’accroche terminées amine. Sur l’oxyde de silicium l’aminopropyletriméthoxysilane (APTMS) a été déposé à partir d’une solution, et via une méthode originale par voie sèche qui nous a permis de mettre en évidence les temps caractéristiques de greffage et d’organisation de la couche d’APTMS. Sur l’or, les monocouches d’aminoéthanethiol (AET) et d’aminothiophénol (ATP) ont été réalisées à partir d’une solution. Nous avons ensuite étudié les aspects structuraux et cinétiques du greffage des fullerènes C60 sur de telles couches d’accroche, constituées de terminaisons amines soit sur toute la surface soit en des zones isolées (couches binaires). Les techniques de spectroscopie UV-Visible, IRTF, Raman, et XPS ont permis d’observer le greffage des C60 sur les couches aminées. La spectroscopie Raman en mode exalté (SERS) a mis en lumière que les molécules d’ATP étaient plus inclinées après le greffage à reflux des C60. Les analyses des diverses couches à l’échelle moléculaire ont été menées par microscopie à sondes locales (AFM, STM), et les mesures électriques réalisées sur or à l’aide de la pointe STM ont montré le caractère isolant de la couche d’accroche seule et un gap proche de celui du C60 après greffage des fullerènes. Elles ont également mis en évidence que le C60 était greffé sélectivement sur les zones terminées amines des couches d’accroche binaires. Enfin, une application potentielle des couches de C60 étant les mémoires moléculaires, les propriétés électriques des diverses couches réalisées ont été mesurées à l’aide de contacts électriques évaporésIn this work we studied the preparation of sticking amine- terminated molecular layers. On silicon dioxide, 3-aminopropyltrimethoxysilane (APTMS) was de- posited from a solution, and using an original dry method that allowed us to determine time constants of APTMS layer grafting and organization. On gold surfaces, monolayers of aminoethanethiol (AET) and aminothiophenol (ATP) molecules were prepared from a solution. Then, we studied structural and kinetic aspects of ullerene C60 grafting on such sticking layers, terminated by amines either all over the surface or on isolated areas (binary layers). UV-visible, FTIR, Raman and XPS spectroscopy techniques enabled to observe that C60 was grafted on the amine-terminated layers. Exalted Raman spec- troscopy (SERS) revealed ATP molecules were more tilted after C60 grafting under reflux. Analyses of all the layers were made at a molecular level by local probe microscopy (AFM, STM), and electrical measurements performed on gold using the STM tip showed the in- sulating nature of the sticking layer whereas a gap close to that of C60 appeared after grafting of fullerenes. They also highlighted that C60 was selectively grafted on amine- terminated zones within binary sticking layers. At last, one of potential applications of C60 layers being molecular memory cells, electrical properties of the various studied layers were measured through evaporated electrical contact pads
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Lu, Kexin. "Organic semiconductors for self-assembled monolayer field effect transistors." Thesis, University of Manchester, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.559330.
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Molecular self-assembly has recently attracted significant attention for possible application in organic electronic and optoelectronic devices, such as self-assembled monolayer field-effect transistors (SAMFETs) and functional self-assembled integrated circuits. Self-assembly combines the advantages of low temperature solution processability, regio-selective monolayer adsorption and nano-scale control of film thickness. Much progress has been made in improving device performance using self-assembled monolayers (SAMs). However, most SAMFET devices reported to date showed current modulation only with submicrometre channels, with low device yields and poor reproducibility as a result of limited lateral interconnection of the semiconducting layer.In an attempt to address these issues, this thesis presents an investigation of the synthesis and properties of conjugated SAM molecules for use as the charge transporting layer in SAMFETs. Chapter 1 gives a comprehensive introduction to SAM-based surface systems, organic semiconductors and their use in OFETs and SAMFETs. Chapter 2 discusses attempts to design and synthesise p-type conjugated molecules capable of self-assembly on oxide surfaces based on a phenylene-bithiophene semiconducting core. The optical and electrochemical properties, as well as the thermal behaviour of these molecules are studied in detail. This theme is carried over to Chapter 3, which describes the synthesis, chemical and physical characterisation of two families of n-type SAM molecules. These molecules consist of NTCDI cores with hexyl or cyclohexyl chains as end-capping groups. Incorporation of a selection of materials as the active layer in OFETs or SAMFETs to evaluate the charge transport is demonstrated in Chapter 4. Monolayer films based on p-type monochlorosilane-terminated SAM molecules are made using the solution assembly technique and characterised by contact angle and AFM. OFETs made from DH-PTTP by both thermal evaporation and spin coating show high mobilities comparable to the best values reported in the literature. Top-contact SAMFETs show a hole mobility of 1.1 × 10-3 cm2V-1s-1 in air, consistent with those of solution processed DH-PTTP based OFETs. Finally, an overview of the project and some suggestions for future work are presented in Chapter 5.
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Matcheswala, Akil Mannan. "GOLD NANOSPHERES AND GOLD NANORODS AS LOCALIZED SURFACE PLASMON RESONANCE SENSORS." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_theses/60.
Full textAbstract:
A novel localized surface plasmon resonance (LSPR) sensor that differentiates between background refractive index changes and surface-binding of a target analyte (e.g. a target molecule, protein, or bacterium) is presented. Standard, single channel LSPR sensors cannot differentiate these two effects as their design allows only one mode to be coupled. This novel technique uses two surface plasmon modes to simultaneously measure surface binding and solution refractive index changes. This increases the sensitivity of the sensor.
Different channels or modes can be created in sensors with the introduction of gold nanospheres or gold nanorods that act as receptor mechanisms. Once immobilization was achieved on gold nanospheres, the technique was optimized to achieve the same immobilization for gold nanorods to get the expected dual mode spectrum. Intricate fabrication methods are illustrated with using chemically terminated self assembled monolayers. Then the fabrication process advances from chemically silanized nanoparticles, on to specific and systematic patterns generated with the use of Electron Beam Lithography.
Comparisons are made within the different methods used, and guidelines are set to create possible room for improvement. Some methods implemented failed, but there was a lot to learn from these unsuccessful outcomes. Finally, the applications of the dual mode sensor are introduced, and current venues where the sensors can be used in chemical and biological settings are discussed.
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Leonardi, Francesca <1986>. "Self-Assembled Monolayers (SAMs) in Organic Field-Effect Transistors." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6461/1/Leonardi__dottorato.pdf.
Full textAbstract:
Organic printed electronics is attracting an ever-growing interest in the last decades because of its impressive breakthroughs concerning the chemical design of π-conjugated materials and their processing. This has an impact on novel applications, such as flexible-large-area displays, low- cost printable circuits, plastic solar cells and lab-on-a-chip devices.
The organic field-effect transistor (OFET) relies on a thin film of organic semiconductor that bridges source and drain electrodes. Since its first discovery in the 80s, intensive research activities were deployed in order to control the chemico-physical properties of these electronic devices and consequently their charge. Self-assembled monolayers (SAMs) are a versatile tool for tuning the properties of metallic, semi-conducting, and insulating surfaces. Within this context, OFETs represent reliable instruments for measuring the electrical properties of the SAMs in a Metal/SAM/OS junction.
Our experimental approach, named Charge Injection Organic-Gauge (CIOG), uses OTFT in a charge-injection controlled regime. The CIOG sensitivity has been extensively demonstrated on different homologous self-assembling molecules that differ in either chain length or in anchor/terminal group.
One of the latest applications of organic electronics is the so-called “bio-electronics” that makes use of electronic devices to encompass interests of the medical science, such as biosensors, biotransducers etc…
As a result, thee second part of this thesis deals with the realization of an electronic transducer based on an Organic Field-Effect Transistor operating in aqueous media. Here, the conventional bottom gate/bottom contact configuration is replaced by top gate architecture with the electrolyte that ensures electrical contact between the top gold electrode and the semiconductor layer. This configuration is named Electrolyte-Gated Field-Effect Transistor (EGOFET).
The functionalization of the top electrode is the sensing core of the device allowing the detection of dopamine as well as of protein biomarkers with ultra-low sensitivity.
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Leonardi, Francesca <1986>. "Self-Assembled Monolayers (SAMs) in Organic Field-Effect Transistors." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6461/.
Full textAbstract:
Organic printed electronics is attracting an ever-growing interest in the last decades because of its impressive breakthroughs concerning the chemical design of π-conjugated materials and their processing. This has an impact on novel applications, such as flexible-large-area displays, low- cost printable circuits, plastic solar cells and lab-on-a-chip devices.
The organic field-effect transistor (OFET) relies on a thin film of organic semiconductor that bridges source and drain electrodes. Since its first discovery in the 80s, intensive research activities were deployed in order to control the chemico-physical properties of these electronic devices and consequently their charge. Self-assembled monolayers (SAMs) are a versatile tool for tuning the properties of metallic, semi-conducting, and insulating surfaces. Within this context, OFETs represent reliable instruments for measuring the electrical properties of the SAMs in a Metal/SAM/OS junction.
Our experimental approach, named Charge Injection Organic-Gauge (CIOG), uses OTFT in a charge-injection controlled regime. The CIOG sensitivity has been extensively demonstrated on different homologous self-assembling molecules that differ in either chain length or in anchor/terminal group.
One of the latest applications of organic electronics is the so-called “bio-electronics” that makes use of electronic devices to encompass interests of the medical science, such as biosensors, biotransducers etc…
As a result, thee second part of this thesis deals with the realization of an electronic transducer based on an Organic Field-Effect Transistor operating in aqueous media. Here, the conventional bottom gate/bottom contact configuration is replaced by top gate architecture with the electrolyte that ensures electrical contact between the top gold electrode and the semiconductor layer. This configuration is named Electrolyte-Gated Field-Effect Transistor (EGOFET).
The functionalization of the top electrode is the sensing core of the device allowing the detection of dopamine as well as of protein biomarkers with ultra-low sensitivity.
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Singla, Saranshu. "Consequences of Interfacial Interactions on Adsorption and Adhesion." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1541714540493631.
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Kick, Alfred. "Oberflächenplasmonenresonanz-basierte DNA-Chips und Nucleobasen-Sequenzentwurf." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-126339.
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Die vorliegende Dissertation beschreibt die Erarbeitung anwendbarer Methoden zum Aufbau Oberflächenplasmonenresonanz (SPR)-basierter DNA-Mikroarrays. Es werden die Beziehungen zwischen allen Teilschritten der Entwicklung eines DNA-Biosensors aufgezeigt. Die Sondendichte auf der Sensoroberfläche ist entscheidend für die Leistungsfähigkeit eines DNA-Chips. In dieser Arbeit werden thiolmodifizierte Sonden und solche mit Phosphorothioatgruppen verwendet und verglichen.
Der Aufbau selbstorganisierender Monoschichten, bestehend aus Mercaptoalkoholen und thiolmodifizierten DNA-Einzelsträngen, wird mittels Röntgenphotoelektronenspektroskopie untersucht. Es werden bis zu 180 Spots auf einem SPR-Chip aufgetragen. Eine weitere Erhöhung der Anzahl an Sondenorten pro Chip wird mit einer hydrophil/hydrophoben Strukturierung der Arrayoberfläche erreicht. Dies erfolgt durch das Mikrokontaktdrucken mit Alkanthiolen.
Die selektiven Hybridisierungen der Produkte der Polymerase-Kettenreaktion (PCR) werden bei SPR-Messungen auf DNA-Mikroarrays detektiert. Eine schnelle markierungsfreie Echtzeitanalyse wird bei Hybridisierungen im mikrofluidischen Kanal innerhalb weniger Minuten erzielt. Die Anwendbarkeit dieser Methoden wurde anhand der Mutationsanalyse der Fusionsgene AML1-ETO und CBFB-MYH11 bei der akuten myeloischen Leukämie bestätigt.
Die Hybridisierungseffizienz auf DNA-Mikroarrays hängt stark von der Sodensequenz ab. SPR-Experimente zeigen, dass die Ausbildung der Haarnadelstrukturen die Ursache dafür ist. Ein Computerprogramm (EGNAS) auf Grundlage eines neu entwickelten Nucleobasen-Sequenzentwurf-Algorithmus, ermöglicht die Generierung vollständiger Sequenzsätze. Die Intra- und Interstrangeigenschaften dieser Sequenzen können kontrolliert werden, um Haarnadelstrukturen und Kreuzhybridisierungen zu vermeiden. Dadurch können optimierte Sequenzen für Anwendungen auf DNA-Chips oder in der DNA-Nanobiotechnologie entworfen werden.
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Adamkiewicz, Malgorzata. "Self-assembled monolayers on silicon : deposition and surface chemistry." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/3938.
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Fabrication of surfaces with versatile functional groups is an important research area. Hence, it is essential to control and tune the surface properties in a reliable manner. Vinyl-terminated self-assembled monolayers (SAMs) offer significant flexibility for further chemical modification and can serve as a versatile starting point for tailoring of surface properties. Here a synthetic route for the preparation of vinyl-terminated trichlorosilane self-assembling molecules: 9-decenyltrichlorosilane (CH₂=CH-(CH₂)₈-SiCl₃), 10-undecenyltrichlorosilane (CH₂=CH-(CH₂)₉-SiCl₃), and 14-pentadecenyltrichlorosilane (CH₂=CH-(CH₂)₁₃-SiCl₃) is presented. These molecules were used for the preparation of SAMs in either liquid or vapour phase processes. Commercially available methyl-terminated self-assembling molecules: decyltrichlorosilane (CH₃-(CH₂)₉-SiCl₃) and octadecanetrichlorosilane (CH₃-(CH₂)₁₇-SiCl₃) were used as controls. The resultant films were characterised by X-ray photoelectron spectroscopy (XPS), contact angle analysis, ellipsometry, and atomic force microscopy (AFM). Well defined, vinyl-terminated SAMs were further chemically modified with carbenes (:CCl₂, :CBr₂, :CF₂) and hexafluoroacetone azine (HFAA). The reactions were performed in the liquid or the vapour phase. The resulting SAMs were characterised using the same methods as for the vinyl-terminated monolayers. Successful modification was confirmed by the appearance of new signals in the XPS spectrum, with simultaneous changes in water contact angle values and unchanged thickness values. Methyl-terminated SAMs were also exposed to carbenes and HFAA as a control system. These are the first examples of C-C bond formation on SAMs in the vapour phase.
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Celesin, Michael Enoch. "Application and Characterization of Self-Assembled Monolayers In Hybrid Electronic Systems." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4875.
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In this study, we explore ultra-thin insulators of organic and inorganic composition and their potential role as high-speed rectifiers. Typical applications for these structures include IR sensing, chemical detection, high speed logic circuits, and MEMS enhancements. While there are many elements in the functional group required to create a rectifying antenna (rectenna), the primary thrust of this work is on the rectifier element itself.
To achieve these research goals, a very good understanding of quantum tunneling was required to model the underlying phenomenon of charge conduction. The development of a multi-variable optimization routine for tunneling prediction was required. MATLAB was selected as the programming language for this application because of its flexibility and relative ease of use for simulation purposes. Modeling of physical processes, control of electromechanical systems, and simulation of ion implantation were also to be undertaken.
To advance the process science, a lithographic mask set was made which utilized the information gleaned from the theoretical simulations and initial basic experiments to create a number of diode test structures. This came to include the creation of generations of mask sets--each optimizing various parameters including testability, alignment, contact area, device density, and process ease. Following this work, a complete toolset for the creation of "soft" contact top metals was required and needed to be developed. Ultra-flat substrates were needed to improve device reliability and measurement consistency.
The final phase of research included measurement and characterization of the resultant structures. Basic DC electrical characterization of the organic monolayers would be accomplished using metal probes. Statistical studies of reliability and process yield could then easily be carried out. The rectification ratio (ratio of forward over reverse current at a given voltage magnitude) was found to be a reliable indicator of diode performance in the low frequency ranges. This would mean writing additional code in MATLAB to assist in the automatic analysis for the acquired IV curves. Progression to AC / RF measurements of tunneling performance was to be accomplished using relatively low frequencies (below 100 MHz). Finally, the organic films themselves would be studied for consistency, impedance characteristics, incidence of defects, and thickness by a variety of metrology techniques.
This project resulted in a number of advances to the state-of-the-art in nanofabrication using organic monolayers. A very detailed review of the state of alkanethiol research was presented and submitted for publication. A single pot technique was developed to softly deposit metal nanoparticles onto a charged surface with a high degree of control. A temporary contact method using pure, sub-cooled gallium liquid metal was used to probe organic monolayers and plot IV curves with better understanding of surface states than before. An inkjet printer solution was devised for top contact printing which involved the development and production of a work-up free insulator ink which is water soluble and printable to resolutions of about 25 um. Localized selective chemical crosslinking was found to reduce printed ink solubility following deposition. Future work will likely include additional exploration of crosslinkable Langmuir-Blodgett films as MIM insulators. Stability and testing will hinge on the fabrication of enclosures or packages for environmental isolation.
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Uzarski, Joshua Robert. "Investigations of Bacteria Viability on Surfaces Using ω-functionalized Alkanethiol Self-Assembled Monolayers." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/33685.
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The structure/function relationship between bacteria and biocidal molecules in the vapor or solution phase is well-understood. However, the fundamental structure/function relationship between covalently-bound biocidal surface molecules and bacteria is not. While a number of antibacterial surfaces have been reported, detailed analysis of the molecular scale surface structure has not been performed. The lack of structural knowledge makes it difficult to determine how alterations to the surface affect the viability of the bacteria. Most of the antibacterial surfaces reported to date are composed of polymer systems. Controlling the properties of large surface-bound molecules like polymers is difficult.
Self-assembled monolayers, or SAMs, of alkanethiols on gold have been used extensively in the past 20 years as model surfaces for investigation of a large breadth of surface phenomena. SAMs allow for control of the molecular scale surface structure and are amenable to a great number of characterization techniques. The primary objective of the work in this study is to establish the use of SAMs as a tool to investigate the fundamental relationship between surface structure and bacteria viability.
The surfaces were characterized before interaction with bacteria by reflection-absorption infrared spectroscopy (RAIRS) and X-ray photoelectron spectroscopy (XPS). Determination of the viability of Escherichia coli on the surfaces was performed via the antibacterial assay. In the assay, a culture of E. coli was sprayed onto the surfaces using a chromatography sprayer. After addition of growth agar and overnight incubation, the number of colony forming units on the surface were counted. Statistical analyses were performed to compare the number of colony forming units on different surfaces. Surfaces were characterized after the assay by RAIRS. The RAIR spectra indicated that no significant change to the well-ordered alkane chain configuration was evident. The structural stability shown by the SAMs will allow for their use in future studies to determine fundamental relationship between surface structure and bacteria viability.Master of Science
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Marchante, Rodríguez Elena. "Self-assembled monolayers of electroactive molecules for the preparation of memory devices." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/406091.
Full textAbstract:
El objetivo fundamental de los circuitos eléctricos es la miniaturización utilizando moléculas, de manera individual o el conjunto de ellas, como bloques de construcción electrónicos. Se espera que el pequeño tamaño de los componentes electrónicos reduzca el consumo de energía a la vez que aumente la sensibilidad y el rendimiento del dispositivo.
Los esfuerzos que se hacen en investigación están orientados en dos direcciones: la primera está enfocada en el estudio, a nivel fundamental, de nuevas moléculas con propiedades o funcionalidades específicas, que proporcionan un conocimiento más profundo de la estructura molecular, dinámica y reactividad. El segundo se dedica al desarrollo de nuevas técnicas para la implementación de estas moléculas in dispositivos electrónicos.
A menudo, para fabricar un dispositivo molecular se necesita depositar las moléculas o materiales en un sustrato adecuado. Es importante controlar cómo afecta el disolvente, el sustrato o la funcionalización molecular en el ensamblaje molecular final y las interacciones moleculares, ya que el ordenamiento y el empaquetamiento de las moléculas son aspectos clave para el funcionamiento de los dispositivos.
Esta Tesis Doctoral está enfocada en el desarrollo de nuevos dispositivos moleculares electrónicos basados en monocapas auto-ensambladas de moléculas electroactivas, y en el estudio electroquímico de los procesos de transferencia electrónica asociados a ellos. En la primera parte de la Tesis, se describe el uso de diferentes moléculas redox inmovilizadas en sustratos de oro como interruptores moleculares. El estado de los compuestos electroactivos se puede modular aplicando un potencial específico sobre el sustrato, y se ha implementado satisfactoriamente la respuesta en capacitancia como señal de salida del interruptor. Es importante destacar que se han obtenido estos interruptores moleculares eléctricos usando también geles iónicos como electrolitos sólidos, demostrando la viabilidad de integrar estos sistemas en futuros dispositivos electrónicos y/o flexibles.
En la segunda parte de la Tesis, se presenta el estudio del mecanismo de transferencia electrónica, por medios electroquímicos, en una familia de compuestos derivados de radicales de policlorotrifenilmetilos (PTM), enlazados a sustratos de oro. La familia de moléculas de PTM contiene un grupo tiol en el extremo conectado al PTM a través de una cadena alquílica de distintas longitudes. Se ha estudiado el proceso de transferencia electrónica a través de SAMs de PTM en distintos medios electrolíticos y en función del grado de recubrimiento de la superficie del sustrato de oro modificado. Por lo tanto, se ha demostrado que la interacción de los disolventes juega un papel importante en el carácter adiabático del proceso redox. Además, el acoplamiento electrónico entre centros de moléculas de PTM adyacentes favorece la disminución de la constante de transferencia electrónica.
Finalmente, en la última parte de la Tesis, se han fabricado transistores orgánicos de efecto campo (OFETs) utilizando un gel iónico como material dieléctrico, y se han estudiado sus propiedades. Los OFET se fabricaron con geometrías tipo “top-gate” y “side-gate”, donde el gel iónico se colocó encima del sustrato con el canal semiconductor. Las propiedades de estos transistores con gel iónico se compararon con estructuras similares como referencia, las cuales están basadas en oxido de silicio convencional, resultando ser bastante interesantes para aplicarlos en transistores orgánicos flexibles y económicos.The ultimate goal of electrical circuits is miniaturization by using single molecules or collections of single molecules as electronic building blocks. It is expected that the smaller size of the electronic components will decrease the power consumption while increasing the sensitivity and the performance of the device. Research efforts are concentrated in two directions. The first one is focused in the study, at a fundamental level, of new molecules with specific properties or functionalities, which provides a deeper understanding of molecular structure, dynamics and reactivity. The second one is dedicated to develop new techniques for the implementation of these molecules in electronic devices. Often, to construct a molecular device it is necessary to deposit molecules or material on a suitable substrate. Since the ordering and packing of the molecules are crucial aspects for the operation of the devices, it is important to have a good control of how solvent, substrate or molecular functionalization influences on the resulting molecular assemblies and the intermolecular interactions. The present Doctoral Thesis is focused on the development of new molecular electronic devices based on electroactive self-assembled monolayers (SAMs), and on the electrochemical study of the electron transfer phenomena associated to them. In the first part of the Thesis, it is described the use of different redox molecules immobilized on gold substrates as molecular switches. The state of the electroactive compounds can be tuned when a specific potential is applied to the substrate, and the capacitance response has been successfully implemented as the read-out of the switch. It is important to highlight that these electrical molecular switches have been also obtained using ion gels as solid electrolytes, demonstrating the feasibility to integrate these systems in future electronic and/or flexible devices. In the second part of the Thesis, it is reported the electron transfer (ET) mechanism study, by electrochemical means, in a family of polychlorothriphenylmethyl radical (PTM) derivative compounds attached to gold substrates. The family of PTM molecules contains a thiol terminal group connected to the PTM through an alkyl chain with different lengths. It has been studied the ET process through PTM-SAMs in different organic electrolytic media and as a function of the surface coverage of the modified gold substrate. Hence, it was demonstrated that the interaction with the solvent plays an important role in the adiabaticity character of the redox process. Further, with neighbouring molecules, the intermolecular electronic coupling between PTM centers promotes a reduction of the ET constant rate. Finally, in the last part of the thesis, it has been fabricated a functioning OFET using an ion gel as gate dielectric, and its properties has been examined. The OFETs were prepared with top-gate and side-gate geometries, where the ion gel was placed on top of the substrate with the semiconductor channel. The ion gel gated OFET properties were compared with a reference OFET structure, which had a conventional SiO2 gate dielectric, demonstrating that the ion gels are highly attractive to be applied in low cost and flexible organic transistors.
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Nilebäck, Erik. "A novel biotinylated surface designed for QCM-D applications." Thesis, Linköping University, Department of Physics, Chemistry and Biology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-19250.
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Control of protein immobilization at sensor surfaces is of great interest within various scientific fields, since it enables studies of specific biomolecular interactions. To achieve this, one must be able to immobilize proteins with retained native structure, while minimizing non-specific protein binding. The high affinity interaction between streptavidin (SA) and biotin is extensively used as a linker between a surface, where SA is immobilized, and the (biotinylated) molecule of interest. Self- assembled monolayers (SAMs) of poly- and oligo ethylene glycol (PEG and OEG) derivatives have been proven in literature to minimize non-specific protein binding, and biotin-exposing SAMs have been shown efficient for immobilization of SA.
The aim of this master's thesis project was to develop biotinylated gold surfaces for quartz crystal microbalance with dissipation monitoring (QCM-D) applications through the self-assembly of mixed monolayers of thiolated OEG (or PEG) derivatives with or without a terminal biotin head group. For this, different thiol compounds were to be compared and evaluated. For the systems under study, the required biotin density for maximum specific SA immobilization was to be established, while keeping the non-specific serum adsorption at a minimum. Model experiments with biotinylated proteins immobilized to the SA-functionalized surfaces were to be performed to evaluate the possibilities for commercialization.
A protocol for the preparation of a novel biotinylated surface was developed based on the immersion of gold substrates in an ethanolic incubation solution of dithiols with OEG chains (SS-OEG and SS-OEG-biotin, 99:1) and found to give reproducible results with respect to low non-specific protein binding and immobilization of a monolayer of SA. The modified surfaces allowed for subsequent immobilization of biotinylated bovine serum albumin (bBSA) and biotinylated plasminogen (bPLG). PLG was the subject of a challenging case study, using a combination of QCM-D and surface plasmon resonance (SPR), where the immobilized protein was subjected to low molecular weight ligands that were believed to induce conformational changes. The high control of the surface chemistry allowed for the interpretation of the increased dissipation shift upon ligand binding in terms of conformational changes.
An obstacle before commercialization of the described biotinylated surfaces is that they do not seem stable for storage > 7 days. The reasons for this have to be investigated further.
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Coelho, Dyovani. "Caracterização eletroquímica de uma monocamada auto-organizada mista composta por ácido 3-mercaptopropiônico e ácido 11-mercaptoundecanóico." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/75/75132/tde-20062011-150712/.
Full textAbstract:
Monocamadas auto-organizadas formadas pela quimissorção de alcanotióis sobre ouro apresentam estruturas bem definidas, organizadas e reprodutíveis. As propriedades de SAMs, aliadas à facilidade de síntese, têm atraído o interesse da comunidade cientifica o que ocasionou um grande avanço na área de nanotecnologia, especialmente em engenharia de superfícies. Neste trabalho, avaliou-se a modificação de um substrato de ouro com uma mistura dos ácidos 3-mercaptopropiônico e 11-mercaptoundecanóico. Com isso procurou-se controlar a configuração da superfície da SAM a fim de se obter um arranjo com ilhas de 3amp circundadas por 11amu, similar a um conjunto de ultramicroeletrodos. A SAM mista foi produzida por incubação de um substrato de ouro em solução etanólica contendo ambos os tiois. O estudo do processo redox do par [Fe(CN)6]4-/[Fe(CN)6]3- demonstrou que monocamadas de 3amp se comportam como a superfície de ouro não modificado, apresentando os mesmos valores de corrente de pico (Ip), potencial de pico (Ep) e resistência de transferência de carga (Rtc), pois permitem que ocorra a transferência eletrônica por efeito de tunelamento quântico dos elétrons através da monocamada. Entretanto monocamadas de 11amu demonstram comportamento isolante, apresentando uma Rtc 250 vezes maior e Ip significativamente menores que a observada para a SAM-3amp. As cargas de dessorção redutiva e variação de massa obtidas com a MECQ para a SAM mista evidenciaram alto recobrimento da superfície e um mecanismo de adsorção que varia com o tempo de incubação do substrato em solução contendo os tiois. Assim, a configuração da superfície com domínios de 3amp bem estabelecidos é alcançada com 20 horas de incubação do substrato. O perfil observado com a voltametria cíclica, aliado aos dados obtidos com a EIE comprova a existência de segregação de fases na SAM mista contendo regiões recobertas pelo 3amp (raio médio de 4,3 µm) circundadas por 11amu (com separação média de 75,42 µm). O estudo do comportamento eletroquímico do fisetin confirma o surgimento de propriedades diferenciadas com a SAM mista, onde observou-se apenas um processo redox sem que o analito permanecesse adsorvido na superfície da SAM. Todavia para a SAM-3amp e ouro não modificado foi observado dois processos redoxes seguido de adsorção irreversível do produto da reação na superfície eletródica. Utilizando a SAM mista como sensor eletroquímico para determinação de fisetin em água alcançou-se um limite de detecção de 1,67 x10-8 mol L-1.Self-assembled monolayers obtained by chemiosorption of alkanethiols on gold present well-defined, organized and reproducible structures. The unique properties exhibited by such surfaces, allied to the great facility to obtain, have attracted the interest of the scientific community and caused a significant advance in the nanotechnology research, especially in the surface engineering one. In this work, the modification of gold substrate with a mixture of 3-mercaptopropionic acid and 11-mercaptoundecanoic acid was evaluated. The aim was control the surface of the SAMs in order to obtain an island arrangement of 3mpa isolated by 11mua, similar to an array of ultramicroelectrodes. The mixed-SAM was built by the incubation of Au substrate in an ethanolic solution containing both thiols. The redox couple [Fe(CN)6]4-/[Fe(CN)6]3- study demonstrated that pure 3mpa monolayers behaves like the bare gold surface, presenting barely the same parameters of peak current (Ip), peak potential (Ep) and charge transfer resistance (Rct), since it allows the electronic transference to occurs by quantum tunneling effect through the monolayer. On the other hand the 11mua monolayers showed an insulating behavior and a Rct value nearly 250 times greater and, consequently, Ip values significantly less than that for 3mpa. The reductive desorption charges and mass changes obtained with an EQCM for the mixed-SAM indicated the high coverage of gold surface and a adsorption mechanism that depends on the incubation time of the substrate in the thiols solution. The surface configuration with 3mpa domains is reached after 20 hours of immersion. The cyclic voltammetric profile, together with the data from electrochemical impedance spectroscopy , proved the existence of phases segregation in the mixed-SAM with surface regions covered solely by 3mpa (with mean radius of 4.3 µm) surrounded by 11mua with a mean separation of 75.42 µm. The electrochemical behavior of the flavonoid fisetin confirms the rising of differentiated properties with the mixed-SAM, where only one electrochemical process was able to be observed, without irreversible adsorption of the analyte. For 3mpa and bare gold surfaces, two (or more) electrochemical processes were observed together with the blocking of the electrode surface by irreversible adsorption of the reaction product. The utilization of the mixed-SAM with electrochemical sensor for fisetin determination in pure water yielded a detection limit of 1.67 x10-8 mol L-1.
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Aydogmus, Turkan. "Thermodynamic and transport properties of self-assembled monolayers from molecular simulations." Texas A&M University, 2004. http://hdl.handle.net/1969.1/3080.
Full textAbstract:
The purpose of the work is to employ molecular simulation to further extend the understanding of Self-Assembled Monolayers (SAMs), especially as it relates to three particular applications: organic-inorganic composite membranes, surface treatments in Micro-Electro-Mechanical Systems (MEMS) and organic-surface-modified Ordered Mesoporous Materials (OMMs).
The first focus area for the work is the use of SAMS in organic-inorganic composite membranes for gas separations. These composite membranes, recently proposed in the literature, are based on the chemical derivatization of porous inorganic surfaces with organic oligomers. Our simulations achieve good qualitative agreement with experiment in several respects, including the improvement in the overall selectivity of the membrane and decrease in the permeance when increasing the chain length. The best improvement in the overall solubility selectivity is reached when the chains span throughout the pore.
The second application focus is on the use of SAMs as coatings in MEMS devices. The work focuses on the modeling of adhesion issues for SAM coatings at the
molecular level. It is shown that as the chain length is increased from 4 to 18 carbon atoms, the adhesion forces between two monolayers at the same separations decreases.
The third application focus is on the use of SAMs for tailoring surface and structural properties of OMMs, in particular, porous silicas. A molecular study of structural and surface properties of a silica material with a 5 nm pore size, modified via chemical bonding of organosilanes with a range of sizes (C4, C8 and C18) is presented. Grand canonical MC simulations are employed to obtain nitrogen adsorption isotherms for unmodified and modified MCM-41 material models. Furthermore, the density profiles of alkyl chains and nitrogen molecules are analyzed to clarify the differences in the adsorption mechanisms in unmodified and modified materials. The position of the capillary condensation steps gradually shifted to lower pressure values with the increase in size of the bonded ligands, and this shift was accompanied by a gradual disappearance of the hysteresis loop. As the length of the bonded ligands is increased, a systematic decrease in the pore diameter is observed and the multi-layer adsorption mechanism in modified model materials diminishes.
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Cavadas, Francisco Troitino. "Spectroscopic and electrochemical investigation of phenyl, phenoxy, and hydroxyphenyl-terminated alkanethiol monolayers." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/28611.
Full textAbstract:
4-(12-mercaptododecyloxy)phenol (1), 3-(12-mercaptododecyloxy)phenol (2), 4-(12-mercaptododecyl)phenol (3), 4-(12-mercapto-dodecyl)phenol (4), 12-phenyldodecyl-mercaptan (5), 12-phenylundecyoxymercaptan (6), 4-(6-mercapto-hexyl)phenol (7), and 4-(12-mercaptododecyloxy)phenol (8) were synthesized. The thiol products were characterized by NMR, HRMS, and elemental analysis. Self-assembled monolayers (SAMs) on gold substrates were prepared from thiols 1-8, and the resulting monolayer surfaces were analyzed using Reflectance Absorbance Infrared Spectroscopy (RAIRS), contact angle goniometry, ellipsometry, reductive desorption cyclic voltametry, and impedance spectroscopy.
Several aromatic C-C vibrational frequencies in the RAIRS spectra, for SAMs of 1-8, reveal a dependence of peak intensity on substitution regiochemistry of the aromatic ring. This result suggests that the orientation of the aromatic ring changes with substitution. Peak intensity, and peak widths of alkyl C-H vibrational features in the RAIRS spectra also reveal a dependence of the environment of the alkyl chain on structure of thiols 1-8. Meta-substitution seems to significantly alter the projection of the terminal -OH group relative to para-substitution.
Contact angles were obtained for each SAM surface using water, glycerol, and ethylene glycol. From the contact angle data, Zisman and Fowkes analyses were performed in order to determine surface free energy values and also to determine the dispersive contribution to the surface energy. The energy values obtained from the Zisman plots as well as the dispersive contributions obtained from the Fowkes plots suggest a dependence of surface energy on substitution regiochemistry of the aromatic ring. The results are consistent with the interpretation of the RAIRS spectra as they relate to the effect substitution regiochemistry has on SAM structure and interfacial properties.
The results of the reductive desorption measurements performed on each monolayer surface, indicate that changes in substitution regiochemistry do not seem to affect the surface coverage of SAMs 1-8. Desorption potentials however, are affected by the structure of the thiols composing the SAM, which suggests that the lateral stability resulting from interactions of the terminal groups and alkyl chains, is different for each monolayer surface. Specifically SAMs of 12-phenyldodecylmercaptan (5) and SAMs of 4-(12-mercaptododecyloxy)phenol (1) seem to be more stable due to interactions of the terminal aromatic ring in SAMs of (5) and due to an increase in van der Waals interactions in SAMs of (1).
Film thicknesses, as determined by ellipsometry, also suggest that meta-substitution of the aromatic ring results in lower thicknesses for SAMs of (4), which is consistent with the interpretation of the structural changes resulting from meta-substitution, suggested by the interpretation of the RAIRS spectrum of SAMs of (4). Thickness measurements also indicate that most of the functionalized SAMs (1-4, 7, 8) react with OTS, which suggests the terminal -OH group is not shielded at the interface and is available for reaction. Following reaction with OTS the RAIRS spectra of the reacted surfaces reveal structural changes to the underlying SAM.
Impedance spectroscopic measurements performed on SAMs of 1-8 reveal what seems to be a correlation between the orientation of the aromatic ring and the resistance properties of the SAM. It appears meta-substitution of the ring lowers the monolayers ability to resist electron transfer.
These data suggest that meta-substitution of the aromatic ring has a significant impact upon the structure of the resulting monolayer relative to monolayers composed of para-substituted molecules. The data also suggests that there is a correlation between molecular structure and interfacial properties particularly as it relates to surface energy and reactivity. Small atomic changes in the molecules composing the SAM result in measurable differences in macroscopic properties of the interface. It is important to recognize the need for understanding structure-property relationships in self-assembled monolayers particularly if logical design of surfaces is to be achieved and applied towards solving problems associated with corrosion and adhesion of metal surfaces.Ph. D.
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Liličenko, Nadežda [Verfasser]. "Adsorption kinetic investigations of phthalocyanine derivatives self assembled monolayers (SAMs) on gold: Temperature influence on the SAM formation process and quality / Nadežda Liličenko." Kassel : Universitätsbibliothek Kassel, 2015. http://d-nb.info/1075466954/34.
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Shuler, Shelby. "Investigation of Gas-Surface Dynamics Using an Ar Atomic Beam and Functionalized Self-Assembled Monolayers." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/32686.
Full textAbstract:
Interactions of gas-phase molecules with surfaces are important in many ordinary
events, such as ozone depletion, corrison of metals, and heterogeneous catalysis. These
processes are controlled by the bonding, diffusion, and reactivity of the impinging gas
species. Our research employs molecular beam techniques and well-characterized
surfaces to study these processes.
The goal of this study is to better understand how the physical and chemical
nature of the surface interface influences energy transfer dynamics in gas-surface
collisions. An atomic beam is used to probe the energy transfer dynamics in collisions of
Argon with model surfaces of functionalized self-assembled monolayers (SAMs)
(1-dodecanethiol and 11-mercapto-1-undecanol) on gold. The beam is directed towards the surface
at an incident angle of 30 degrees and the scattered Ar atoms are detected at the specular angle
of 30 degrees. Time-of-flight scans measure the velocity distributions of atoms leaving the surface,
which correlate with the energy transfer dynamics of the impinging gas atoms.
Gas-surface energy transfer experiments are accomplished by directing an 80 kJ/mol
Ar atomic beam at a clean Au(111) surface and surfaces composed of hydroxyl-terminated
or methyl-terminated SAMs on Au(111). The fractional energy transferred to
the bare gold surface is 69 %, while it is grater than 77 % for the monolayer-covered
surfaces. The extent of thermalization on the surface during the collision is significantly
greater for the methyl-terminated surface than for the hydroxyl-terminated surface. Since the two
monolayers are similar in structure, packing density, and mass, the differences in
scattering dynamics are likely due to a combination of factors that may include
differences in the available energy modes between the two terminal groups and the
hydrogen-bonding nature of the hydroxyl-terminated SAM.Master of Science
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Hou, Lin, Jaber Derakhshandeh, Silvia Armini, Carine Gerets, Preter Inge De, Rebibis Kenneth June, Andy Miller, wolf Ingrid De, and Eric Beyne. "SAMs (self-assembled monolayers) passivation of cobalt microbumps for 3D stacking of Si chips." Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-207172.
Full textAbstract:
In this paper SAM (self-assembled monolayers) is used to passivate cobalt microbumps for 3D-stacking of Si chips. The SAM deposition process is optimized, using input from characterization techniques such as water contact angle measurement, ATR, AFM and XPS analysis in order to form a monolayer of Thiols-SAM on cobalt microbumps. A 3D stacked Si chips test vehicle was used to demonstrate the effectiveness of the SAM coating on cobalt bumps by measuring the electrical continuity of daisy chains.
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Lenfant, Stéphane. "Contribution à l'électronique moléculaire : de la jonction au composant." Habilitation à diriger des recherches, Université des Sciences et Technologie de Lille - Lille I, 2013. http://tel.archives-ouvertes.fr/tel-00918954.
Full textAbstract:
La croissance du nombre d'études en électronique moléculaire depuis plusieurs décennies repose sur la perpective fascinante d'utiliser des " briques " moléculaires nanométriques pour la fabrication de composants électroniques. Le travail présenté ici s'inscrit dans cette perspective avec comme particularité d'utiliser les monocouches auto-assemblées (les SAMs) pour former le système moléculaire à étudier. La synthèse de ces travaux de recherche en électronique moléculaire durant ces 10 dernières années à l'IEMN sera présentée en se focalisant plus particulièrement sur quatre aspects de ces activités. Tout d'abord, nous aborderons la problématique de la formation expérimentale de la jonction moléculaire (métal ou semi-conducteur/molécules/métal). Dans ce cadre, nous décrirons la réalisation expérimentale de nombreux types de jonctions moléculaires par: électrodes coplanaires (espacées de 50 µm à 16 nm), masque mécanique, micro-nanopore, contact avec une électrode liquide (eGaIn et Hg) et Conducting AFM. Dans un second temps, nous discuterons des mécanismes de transport électronique au sein de la jonction. Pour cela nous étudierons une technique très utilisée depuis quelques années appelée Transition Voltage Spectrocopy (ou TVS), qui permet théoriquement de remonter au niveau d'énergie de l'orbitale moléculaire impliquée dans le transport électronique au sein de la molécule. Notre approche dans cette partie repose sur l'analyse par TVS d'un grand nombre de jonctions moléculaires formées par différentes techniques, et différentes molécules déposées en SAM (en fait 3 familles de molécules). Les résultats obtenus seront comparés à ceux obtenus par UPS et IPES afin d'estimer la pertinence de la technique TVS. Nous verrons que ce travail met en lumière l'importance de l'interface sur l'interprétation des résultats obtenus par TVS. Le troisième aspect traitera de la réalisation d'un composant moléculaire : le transistor à effet de champ, dont le canal conducteur est constitué d'une SAM. La fabrication à l'aide d'électrodes coplanaires de ce type de composant, nommé Self Assembled Monolayer Field Effect Transistor ou SAMFET, sera décrite. Nous verrons que ce transistor donne des valeurs de mobilités comparables à celles obtenues sur des transistors organiques avec un canal conducteur plus épais. De plus, les tensions nécessaires au fonctionnement de ce SAMFET sont très faibles (inférieures à 2V). C'est la première démonstration de SAMFET avec des tensions de fonctionnement proches du volt. Le quatrième et dernier volet portera sur la réalisation de jonctions moléculaires stimulables, c'est-à-dire des molécules dont la conductance change sous l'effet d'une excitation extérieure. Trois aspects seront détaillés : tout d'abord, nous comparerons les conditions de greffage sur substrat d'or pour des SAMs constituées de molécules dérivées quaterthiophène avec une ou deux fonctions thiol ; puis nous étudierons une molécule déposée en SAM capable de réagir avec des cations Pb2+ et modifier ses propriétés électroniques ; et enfin, nous examinerons des jonctions excitables optiquement nommées commutateurs électro-optiques. Pour ce dernier exemple, la jonction est constituée d'une molécule avec un groupement azobenzène. Ce groupement peut basculer optiquement et réversiblement entre deux isomères. Ces deux isomères ont des conductances différentes, le rapport des conductances moyen a été mesuré à environ 1,5.103 et avec une valeur maximum de 7.103. Ce ratio de conductance entre les deux isomères demeure à ce jour le plus élevé mesuré pour des jonctions moléculaires à base de molécules dérivées azobenzène.
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R, Kyvik Adriana. "Self-assembled monolayers for biological applications: design, processing, characterization and biological studies." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/666882.
Full textAbstract:
Self-assembled monolayers (SAMs) on gold surfaces have been designed, processed,
characterized and used for specific biological studies. The studies performed include
the control of lipid bilayer diffusion, cell adhesion and vascularization studies and
also the creation of antimicrobial surfaces.
More specifically, dynamic SAMs on surfaces whose properties can be modified
with an electrochemical external stimulus have been developed and used to interrogate
biological systems. The developed platform has been applied to two different
applications to overcome present challenges when performing biological studies.
Firstly, in Chapter 2, the design and synthesis of all the molecules needed to
develop an electroactive platform, its processing as SAMs and the optimization of
the surface confined redox process between a non-reactive Hydroquinone (HQ)
termination and its corresponding reactive Benzoquinone (BQ) is reported. Two
different interfacial reactions taking place on the electroactivated surfaces were
studied in detail; the Diels-Alder (DA) and the Michael Addition (MA) interfacial
reactions, with cyclopentadiene (Cp) or thiol tagged molecules, respectively. The
comparative study between DA and MA as surface functionalization strategies with a
temporal control reveal that even though MA is not commonly used for this purpose
it offers an attractive strategy for stimulus activated functionalization for biological
applications.
In Chapter 3, the developed platform has been used to achieve a temporal control
of cell adhesion and in this way mimic in vivo conditions more accurately. Cell
adhesion plays fundamental roles in biological functions and as such, it is important
to control cell adhesion on materials used for biomedical applications. Towards this
aim, the dynamic interface developed has been used to immobilize cell adhesion promoting
peptides through the two different interfacial reactions, namely the DA and
the MA reaction, and a comparative study has been carried out. Moreover, a study
involving immobilized VEGF-mimicking peptide Qk has been conducted demonstrating
the possibility of using the novel peptide for directing cell differentiation into
tubular networks for in vitro platforms, by attaching them on a surface.
In Chapter 4, we have used the developed electroactive interface to control the
dynamics of lipid bilayers as cell membrane models, designed for transmembrane
protein characterization in a more in vivo like environment. Specifically, electroactive
SAMs have been used to control the moment in which tethering of lipid bilayer
deposited on them occurs and consequently decrease its diffusion. In this way,
proteins and lipids can maintain their fluidity until tethering is desired, a useful
platform for transmembrane protein characterization.
iii
Finally, in Chapter 5, a surface biofunctionalization strategy also based on SAMs
has been used to produce a bactericidal surface by successfully immobilizing novel
antimicrobial proteins produced by recombinant DNA technology. This is relevant in
view of the verge of an imminent antibiotics crisis. To confirm the antimicrobial activity
and biofilm growth prevention of these surfaces, a biofilm assay was performed
demonstrating that proteins retain their antimicrobial effect when immobilized.
All these strategies open new possibilities for controlled biomolecule immobilization
for fundamental biological studies and for applications in biotechnology, in the
interface of materials science and biology.
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Graham, Amy L. "Characterization of Heterojunctions via X-Ray and UV Photoemission Spectroscopy: Energy Level Implications for Single and Mixed Monolayer SAMs, CdSe Nanoparticle Films, and Organic Semiconductor Depositions." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/195913.
Full textAbstract:
This work has centered on the interface dipoles arising at heterojunctions between metals, semiconductor nanoparticles, self-assembled monolayers, and organic semiconductor materials. Alkanethiol self-assembled monolayers, CdSe nanocrystals, and the organic semiconductors zinc phthalocyanine (ZnPc) and Buckminster fullerene (C60) were the basis of these investigations. UV photoemission spectroscopy has proven to be an invaluable tool to observe the vacuum level shifts for these analyses while using XPS to corroborate surface structure. With a full evaluation of these surfaces, the shifts in the vacuum level, valence ionizations, and core ionizations, the impact of these interfaces, as well as their influence on the subsequent deposition of organic semiconductor layers is established.Alkanethiols possessing varying dipole moments were examined on gold and silver substrates. The viability of these alkanethiols was demonstrated to predictively adjust the work function of these metals as a function of their intrinsic dipole moments projected to surface normal, and established differences between Ag--S and Au--S bonds. The capability of the SAMs to modify the work function of gold provided an opportunity for mixed monolayers of the alkanethiols to produce a precise range of work functions by minimal adjustments of solution concentration, which were examined with a simple point dipole model.Photoemission spectroscopy offers a thorough analysis of CdSe nanoparticle films. Despite a plethora of research on these nanocrystals, there still is controversy on the magnitude of the shift in the valence band with diameter. In our research we found the majority of the valence band shift could be attributed to the interface dipole, ignored previously. Meanwhile, the valence band tethered films was obscured by the sulfur of the thiol tether.Finally, organic semiconductor layers deposited on SAMs on gold exhibited various interface dipole effects at these heterojunctions. Charge transfer states of ZnPc did not favor energy level alignment on the SAM/Au substrates used; C60 demonstrated vacuum level shifts on C15 and C12ph alkanethiol monolayers consistent with the interface charge transfer (ICT) model. These results provide credibility to models recently demonstrated in the literature for other passivated metal surfaces, and include the viability of SAMs in these discussions.
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Bennett, Megan. "Energy Transfer Dynamics in Collisions of Polar and Non-polar Gases with Functionalized Self-Assembled Monolayers." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/33229.
Full textAbstract:
Molecular beam scattering experiments are used to investigate the extent of thermal accommodation of Ne, CD4, ND3, and D2O in collisions with long chain CH3, NH2, and OH terminated self-assembled monolayers (SAMs) on gold. Surface rigidity, internal degrees of freedom of the impinging gas, and potential energy surface well depths have been explored as a way to predict the outcome of a gas-surface collision. Ne is used to assess the mechanical rigidity of the SAMs. The order of rigidity is CH3 < NH2 ~ OH. The NH2 and OH terminated SAMs are more rigid due to the intermolecular hydrogen bonding structure at the gas-surface interface. Despite the hydrogen bonding nature of the NH2 and OH terminated SAMs CD4, ND3, and D2O are extensively thermally accommodated on the surfaces, therefore surface rigidity is no solely responsible for energy transfer dynamics. It was found that the number of degrees of freedom do not predict how extensively a gas will thermally accommodate on a surface capable of hydrogen bonding. A qualitative correlation between increasing potential energy well depths and the extent of thermal accommodation has been established as a result of these scattering experiments.Master of Science
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Madaan, Nitesh. "Synthesis and Characterization of Complex Molecular Assemblies on Surfaces." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/5748.
Full textAbstract:
The research presented in this dissertation is focused on the construction of complex molecular structures on planar gold and silicon dioxide surfaces using a variety of surface modification techniques, along with thorough surface characterization at each modification step. The dissertation is structured into six separate chapters. In Chapter 1, an introduction to the importance and implications of molecular level surface modification, commonly employed surface modification methods, and available surface characterization techniques is presented. Chapter 2 shows applications of novel methodologies for the functionalization of gold surfaces using alkane dithiol self-assembled monolayers and thiol-ene click chemistry. The resulting functionalized gold substrates demonstrate higher chemical stability than alkanethiol self-assembled monolayers alone and allow spatially controlled functionalization of gold surfaces with light. In Chapter 3, work on tunable hydrophobic surfaces is presented. These surfaces are prepared using a combination of organosilane chemistry, layer-by-layer polyelectrolyte deposition, and thiol-ene chemistry. These hydrophobic surfaces demonstrate high mechanical and chemical stability, even at low pH (1.68). The pinning of water droplets could be tuned on them by the extent of their thermal treatment. Comprehensive surface characterization using X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), spectroscopic ellipsometry, atomic force microscopy, and water contact angles was carried out on the molecular assemblies prepared on gold and silicon dioxide surfaces. Chapters 4 and 5 are focused on the application, data interpretation, and enhancement in sensitivity of different surface characterization methods. In Chapter 4, XPS, ToF-SIMS, and principal components analysis are used to probe a real world corrosion-type problem. This systemic study showed the destruction of a protective coating composed of a nitrilotris(methylene)triphosphonic acid by a low-intensity fluorine plasma. In Chapter 5, enhancement in ToF-SIMS signals is shown via bismuth metal deposition. These surfaces are also probed by spectroscopic ellipsometry using the interference enhancement method. Finally, Chapter 6 concludes this dissertation by describing possible future work.
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Watcharinyanon, Somsakul. "Structure of Self-Assembled Monolayers on Gold Studied by NEXAFS and Photoelectron Spectroscopy." Doctoral thesis, Karlstad : Faculty of Technology and Science, Physics, Karlstads universitet, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-2723.
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Wang, Lian. "Synthesis and Characterization of Functionalized Bio-Molecular Surfaces with Self-Assembled Monolayers and Bioreactive Ligands for Nano/Biotechnological Applications." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/195096.
Full textAbstract:
In this work, the synthesis and characterization of functionalized biosurfaces that can be used for bioseparations and bio-nanotechnology are reported. A novel protein purification technique that incorporates chelating ligands and polymers onto the same chromatographic matrix is explored. A polysaccharide based gel, agarose, was modified systematically with hybrid ligands of the chelator iminodiacetic acid (IDA) and the polymer polyethylene glycol (PEG). The PEG molecule acts as a blocking polymer that can allow only small proteins to permeate onto the matrix surfaces and form conventional immobilized metal ion affinity chromatographic (IMAC) interactions with the chelators. Kinetic studies of chelator and polymer attachment were performed in order to effectively control the chelator and polymer densities on the matrix. Studies with different PEG surface densities and their effects on the adsorption of several proteins (e.g. myoglobin, lysozyme and bovine serum albumin (BSA)) were evaluated to characterize these new hybrid size exclusion IMAC (SEIMAC) matrices. An exclusion effect was observed while adsorption as observed in IMAC systems took place.Functionalization schemes and procedures were extended in the activation and incorporation of affinity ligands on inorganic surfaces such as gold surfaces. Functional gold platforms were explored for development of nano-interconnects via functionalized self assembled monolayers (FSAMs) on gold to attach specific affinity ligands as linkers to immobilize biomolecules, such as microtubules (MTs). MTs eventually could be utilized as self assembling structures and templates for fabrication of nano-scale bio-interconnect arrays and networks. In this work, different organothiols were used to form FSAMs and anti-glutathione S-transferase was attached as a linker to utilize the attachment of MT cap proteins, gamma-tubulin. The gamma-tubulin could recognize specifically a heterodimer of the MTs and can provide a nucleation center for MT growth. Several methodologies were employed including photolithographic methods and the use of photoreactive compounds for proper micro/nano scale dual protein functionalization of surfaces with homogeneous affinity ligands and with heterogeneous ligands as well.
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Khanduyeva, Natalya. "Conjugated Polymer Brushes (Poly(3-hexylthiophene) brushes): new electro- and photo-active molecular architectures." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1232556562686-70575.
Full textAbstract:
The aim of the present work was to screen the main methods for the synthesis of conjugated polymers for their suitability in the preparation of conductive polymer brushes. The main focus was put on the grafting of intrinsically soluble substituted regioregular polyalkylthiophenes because of their excellent optoelectronic properties. The resulting polymer films were characterized and their optoelectrical properties studied. For the first time, a synthesis of conductive polymer brushes on solid substrates using “grafting-from” method was performed. The most important, from my opinion, finding of this work is that regioregular head-to-tail poly-3-alkylthiophenes – benchmark materials for organic electronics - can be now selectively grafted from appropriately-terminated surfaces to produce polymer brushes of otherwise soluble polymers - the architecture earlier accessible only in the case of non-conductive polymers. In particular, we developed a new method to grow P3ATs via Kumada Catalyst Transfer Polymerization (KCTP) of 2-bromo-5-chloromagnesio-3-alkylthiophene. Exposure of the initiator layers to monomer solutions leads to selective chain-growth polycondensation of the monomers from the surface, resulting into P3AT brushes in a very economical way. The grafting process was investigated in detail and the structure of the resulting composite films was elucidated using several methods. The obtained data suggests that the grafting process occurs not only at the poly(4-bromstyrene) (PS-Br)/polymerization solution interface, but also deeply inside the swollen PS-Br films, penetrable for the catalyst and for the monomer The grafting process was investigated in detail and the structure of the resulting composite film was elucidated using ellipsometry, X-ray Photoelectron Spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS), and Conductive atomic force microscopy (C-AFM). The obtained data suggests that the grafting process occurs not only at the poly(4-bromostyrene), PS-Br/polymerization solution interface, but also deeply inside the swollen PS-Br film, which is penetrable for the catalyst and the monomer. The process results in an interpenetrated PS-Br/P3HT network, in which relatively short poly(3-hexylthiophene), P3HT grafts emanate from long, cross-linked PS-Br chains. A further method investigated during our work was to covalently graft regioirregular P3HT to substrates modified by macromolecular anchors using oxidative polymerization of 3HT with FeCl3. P3HT layers with variable thicknesses from 30 nm up to 200 nm were produced using two steps of polymerization reaction. The P3HT obtained by oxidative polymerization had always an irregular structure, which was a result of the starting monomer being asymmetric, which is undesired for electronic applications. The third method for the production of conductive polymer brushes was to graft regioregular poly(3,3''-dioctyl-[2,2';5',2'']terthiophene) (PDOTT) by electrochemical oxidative polycondensation of symmetrically substituted 3,3''-dioctyl-[2,2';5',2'']terthiophene (DOTT). A modification of the supporting ITO electrode by the self-assembled monolayers (SAMs) of compounds having polymerizable head-groups with properly adjusted oxidative potentials was found to be essential to achieve a covalent attachment of PDOTT chains. The polymer films produced show solvatochromism and electrochromism, as well as the previous two methods. After polymerization, the next step towards building organic electronic devices is applying the methods obtained in nano- and microscale production. Block copolymers constitute an attractive option for such surface-engineering, due to their ability to form a variety of nanoscale ordered phase-separated structures. However, block copolymers containing conjugated blocks are less abundant compared to their non-conjugated counterparts. Additionally, their phase behaviour at surfaces is not always predictable. We demonstrated in this work, how surface structures of non-conductive block copolymers, such as P4VP-b-PS-I, can be converted into (semi)conductive P4VP-b-PS-graft-P3HT chains via a surface-initiated polymerization of P3HT (Kumada Catalyst Transfer Polymerization (KCTP) from reactive surface-grafted block copolymers. This proves that our method is applicable to develop structured brushes of conductive polymers. We believe that it can be further exploited for novel, stimuli-responsive materials, for the construction of sensors, or for building various opto-electronic devices. The methods developed here can in principle be adapted for the preparation of any conductive block copolymers and conductive polymers, including other interesting architectures of conductive polymers, such as block copolymers, cylindrical brushes, star-like polymers, etc. To this end, one needs to synthesize properly-designed and multi-functional Ni-initiators before performing the polycondensation.
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Khanduyeva, Natalya. "Conjugated Polymer Brushes (Poly(3-hexylthiophene) brushes): new electro- and photo-active molecular architectures." Doctoral thesis, Technische Universität Dresden, 2008. https://tud.qucosa.de/id/qucosa%3A23635.
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The aim of the present work was to screen the main methods for the synthesis of conjugated polymers for their suitability in the preparation of conductive polymer brushes. The main focus was put on the grafting of intrinsically soluble substituted regioregular polyalkylthiophenes because of their excellent optoelectronic properties. The resulting polymer films were characterized and their optoelectrical properties studied. For the first time, a synthesis of conductive polymer brushes on solid substrates using “grafting-from” method was performed. The most important, from my opinion, finding of this work is that regioregular head-to-tail poly-3-alkylthiophenes – benchmark materials for organic electronics - can be now selectively grafted from appropriately-terminated surfaces to produce polymer brushes of otherwise soluble polymers - the architecture earlier accessible only in the case of non-conductive polymers. In particular, we developed a new method to grow P3ATs via Kumada Catalyst Transfer Polymerization (KCTP) of 2-bromo-5-chloromagnesio-3-alkylthiophene. Exposure of the initiator layers to monomer solutions leads to selective chain-growth polycondensation of the monomers from the surface, resulting into P3AT brushes in a very economical way. The grafting process was investigated in detail and the structure of the resulting composite films was elucidated using several methods. The obtained data suggests that the grafting process occurs not only at the poly(4-bromstyrene) (PS-Br)/polymerization solution interface, but also deeply inside the swollen PS-Br films, penetrable for the catalyst and for the monomer The grafting process was investigated in detail and the structure of the resulting composite film was elucidated using ellipsometry, X-ray Photoelectron Spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS), and Conductive atomic force microscopy (C-AFM). The obtained data suggests that the grafting process occurs not only at the poly(4-bromostyrene), PS-Br/polymerization solution interface, but also deeply inside the swollen PS-Br film, which is penetrable for the catalyst and the monomer. The process results in an interpenetrated PS-Br/P3HT network, in which relatively short poly(3-hexylthiophene), P3HT grafts emanate from long, cross-linked PS-Br chains. A further method investigated during our work was to covalently graft regioirregular P3HT to substrates modified by macromolecular anchors using oxidative polymerization of 3HT with FeCl3. P3HT layers with variable thicknesses from 30 nm up to 200 nm were produced using two steps of polymerization reaction. The P3HT obtained by oxidative polymerization had always an irregular structure, which was a result of the starting monomer being asymmetric, which is undesired for electronic applications. The third method for the production of conductive polymer brushes was to graft regioregular poly(3,3''-dioctyl-[2,2';5',2'']terthiophene) (PDOTT) by electrochemical oxidative polycondensation of symmetrically substituted 3,3''-dioctyl-[2,2';5',2'']terthiophene (DOTT). A modification of the supporting ITO electrode by the self-assembled monolayers (SAMs) of compounds having polymerizable head-groups with properly adjusted oxidative potentials was found to be essential to achieve a covalent attachment of PDOTT chains. The polymer films produced show solvatochromism and electrochromism, as well as the previous two methods. After polymerization, the next step towards building organic electronic devices is applying the methods obtained in nano- and microscale production. Block copolymers constitute an attractive option for such surface-engineering, due to their ability to form a variety of nanoscale ordered phase-separated structures. However, block copolymers containing conjugated blocks are less abundant compared to their non-conjugated counterparts. Additionally, their phase behaviour at surfaces is not always predictable. We demonstrated in this work, how surface structures of non-conductive block copolymers, such as P4VP-b-PS-I, can be converted into (semi)conductive P4VP-b-PS-graft-P3HT chains via a surface-initiated polymerization of P3HT (Kumada Catalyst Transfer Polymerization (KCTP) from reactive surface-grafted block copolymers. This proves that our method is applicable to develop structured brushes of conductive polymers. We believe that it can be further exploited for novel, stimuli-responsive materials, for the construction of sensors, or for building various opto-electronic devices. The methods developed here can in principle be adapted for the preparation of any conductive block copolymers and conductive polymers, including other interesting architectures of conductive polymers, such as block copolymers, cylindrical brushes, star-like polymers, etc. To this end, one needs to synthesize properly-designed and multi-functional Ni-initiators before performing the polycondensation.
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PIPAN, GIULIO. "Inkjet printing of solutions as precursors of: i) organic semiconducting single crystals on self-assembled monolayers modified substrates and ii) nanoscale-thin dielectric layers." Doctoral thesis, Università degli Studi di Trieste, 2017. http://hdl.handle.net/11368/2908112.
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In the last years inkjet Printing (IJP) has become a very important technology for creating flexible devices for electronics, due to its simplicity, low cost and high precision. In this frame, the European Project i-FLEXIS sought for realizing novel ionizing radiation detectors based on Organic Semiconducting Single Crystals (OSSCs) on flexible substrates, capable of low power operation, flexibility, optical transparency, all at low fabrication costs and high throughput.
Chapter 1 – Introduction – the main characteristics of the organic semi-conductors, on which the organic electronics is based, will be indicated and described. In addition, the production methodologies will be illustrated, focusing on Inkjet printing, which will be described in detail. The surface on which the crystals grow has an important role since its chemical and physical characteristics influence two fundamental aspects: i)crystal type; ii)electrical conduction inside an electronic device. The characteristics of the surface can be modified using a chemical approach. This work has been focused on Self Assembled Monolayers (SAMs), used to cover the surface, and optimize its characteristics; these organic molecules have been studied and their properties, functions and applications will be described. At the end the growth via low temperature combustion reaction of a nanolayer of AlOx, used as a dielectric inside of a TFT, will be illustrated. The solution containing the precursors is deposited using ink jet printing.
Chapter 2 – Results, Discussions, Materials and Methods – will concern one of the currently main prospected applications of IJP, which is the fabrication of organic electronics devices based on organic semiconductors crystals. The organic molecule involved in this PhD research is the TIPS-pentacene, due to its excellent semiconducting behavior and its capability to detect X-rays. The defects and the heterogeneity of the substrates, in addition to the high evaporation rate (caused by the spreading of the printed drop), promote the formation of little crystals and poly-crystalline domains. This problem can be solved using the printing of a solvo-phobic corral based on fluorinate SAMs, which keeps the drop compact reducing the evaporation rate and creating TIPS single crystals in the range of 1 to 2,5 mm length. The increase of the electrical conduction between the electrodes and the TIPS crystals is made possible by their orientation. The method used to orientate these crystals is geometrical: a corral with a high length versus width ratio is printed, this promotes their growth along the major axe of the corral. The verification of the electrical conduction between the electrodes and the TIPS crystals has been carried out by preliminary tests at the University of Trieste and, subsequently, by tests on the X-ray detection at the University of Bologna, a collaborating group in the frame of the i-FLEXIS project. The printed TIPS single crystals are able to collect charge carriers created by the absorption of ionizing radiation.
Chapter 3 – Ink jet printed nano-thin dielectric layers – will be about the development of a printed dielectric layer made by AlOx at the New University of Lisbon, in order to obtain a complete printed device. The dielectric layer has been grown through the chemical reaction of combustion at low temperature, after its printing on a silicon substrate. The ink formulation has been limited by the precursors type and concentration, in addition to the limitations provided by the printer itself. The solution has consisted of a mix of solvents that respect all the required parameters. All the inks have been printed and tested. The best ink obtained from the tests has been adopted as a dielectric layer inside the TFTs, which subsequently have been electrically tested successfully.
Chapter 4 – Summary of the Conclusion
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Guo, Chuan. "Biosensitive Functionalised Silicon Surfaces: towards Biosensitive Field-Effect-Transistors." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/9476.
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Electrical impedance spectroscopy (EIS) is a method that characterizes the electrical properties of a system of interest and provides a non destructive method for studying its structure and function. In this study, EIS was used to determine the electrical properties and physical structure of the formation of Self-assembled monolayers (SAMs) of biological materials on silicon surfaces. The electrical properties and physical structures of the interaction of human antibodies with carboxylic acid groups attached to highly and low doped n-type silicon (111) are presented. The specific binding test of anti-human antibodies with human antibody modified silicon surfaces were analysed by EIS and confirmed by X-ray photoelectron spectroscopy (XPS). Plasma polymers were the second major topic in this research. They were used as alternative linkers to attach biomolecules to the silicon substrate. Compared to the self-assembled monolayers technology, plasma polymers provided higher protein coverage and required simpler preparative processes. EIS results revealed the changes in the electric properties after each step of the attachment process and binding of ligands. XPS measurements and wetting tests confirmed the EIS results. The results in this thesis show that EIS is a fast and reliable detection method and sensitive enough to detect small changes on the molecular monolayer level. Measurements can be performed directly without requiring any special treatment. The SAMs or plasma coated polymers immobilized directly on the silicon surfaces provides a platform for antibody immobilization in biosensor development that can be tailored to detect antigen-antibody binding. The coupling of the biomolecules on low doped silicon surface induced a field effect inside the silicon. This field effect was dependent on the charge of the biomolecules. This would therefore allow the construction of an actual experimental BioFET that could detect the antigen-antibody interactions.
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Lassoued, Karima. "Etude théorique des mécanismes mis en jeu lors de la formation de monocouches auto-assemblées de molécules éléctroactives sur la surface de l'or Au(111)." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066429.
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Dans le but de développer des matériaux et des dispositifs avec de nouvelles propriétés, l’élaboration de monocouches auto-assemblées (SAM) est un sujet d'intérêt croissant dans le domaine des nanosciences. Les SAM sont des agrégats bidimensionnels formés par des molécules régulièrement espacées sur une surface et liées entre elles par des forces non covalentes. Le domaine des biocapteurs électrochimiques pour la reconnaissance des brins d'ADN est parmi les applications les plus récentes des SAM. Dans ce cadre, nous avons mené une étude théorique des mécanismes fondamentaux engagés lors de l’adsorption de la molécule quinone Jug-C4-thiol sur la surface Au (111). Les résultats ont été confrontés aux mesures expérimentales accessibles réalisées par l’équipe « nano 2D » au laboratoire ITODYS (Université Paris7). Tout d’abord, la théorie de la fonctionnelle de la densité PBE et PBE-D2 a été utilisée pour étudier les mécanismes mis en jeu (physisorption ou chimisorption) lors de l’adsorption de la molécule isolée à la surface de Au (111) et déterminer le site le plus favorable pour chaque mécanisme. La nature de la liaison entre la molécule et la surface de a été finement analysée à l’aide de calculs de densité d’états (DOS) et de différences de densités de charge. Ensuite, l'assemblage de la molécule quinone Jug-C4-thiol sur la surface Au (111) a été étudié. Cet assemblage des molécules a été initié par la formation de configurations de dimère à travers la formation de liaisons intermoléculaires (liaison hydrogène et π-stacking, …). Les spectres infrarouges des configurations les plus stables ont été simulés et confrontés à l’expérience. Et enfin, le mécanisme d’échange entre des molécules « hôtes » (alcanethiols C12H25SH préalablement assemblés sur la surface) et « invitées » (Jug-C4-thiols) a été exploré avec les outils théoriques. L’analyse des résultats a mis en évidence des informations structurales et énergétiques importantes sur la formation de la monocouche moléculaire mixteIn order to develop materials and devices with new properties, the development of self- In order to develop materials and devices with new properties, the development of self-assembled monolayers (SAM) is a topic of growing interest in the field of nanoscience. SAM are two-dimensional aggregates formed by molecules regularly spaced on a surface and bonded together by non-covalent forces. The field of electrochemical biosensors for DNA strand recognition is among the most recent applications of SAM. In this context, we conducted a theoretical study of the fundamental mechanisms involved in the adsorption of the quinone Jug-C4-thiol molecule on the Au (111) surface. The results were compared to the accessible experimental measurements from the "nano 2D" team at the ITODYS laboratory (Paris 7 University). First, the density functional theory at PBE and PBE-D2 levels was used to study the mechanisms involved (physisorption or chemisorption) during the adsorption of the isolated molecule on the surface of Au (111) and access to the most favorable site for each mechanism. The nature of the binding between the molecule and the surface was finely analyzed using density of states (DOS) calculations and differences in charge densities.Then, the assembly of the quinone Jug-C4-thiol molecule on the Au (111) surface was studied. This assembly of molecules was initiated by the formation of dimer configurations through the formation of intermolecular bonds (hydrogen bonding and π-stacking, etc.). The infrared spectra of the most stable configurations were simulated and compared with the experiment. And finally, the mechanism of exchange between "host" molecules (C12H25SH alkanethiols previously assembled on the surface) and "invited" molecules (Jug-C4-thiols) was explored with the theoretical tools. The analysis of the results revealed important structural and energetic informations on the formation of the mixed molecular monolayer
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Meillan, Matthieu. "Immobilisation de biomolécules sur des monocouches auto-assemblées et élaboration de sondes AFM à nanotubes de carbonne fonctionnalisés pour des mesures d'interactions ligrand-récepteur." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0109/document.
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Lors de la mise au point de biocapteurs, le contrôle de l'état de surface sur laquelle sontimmobilisées les biomolécules est un paramètre crucial pour la fiabilité et la reproductibilité desmesures. Pour ce travail de Thèse, deux objectifs principaux ont été fixés :- obtenir de façon reproductible des films organiques fonctionnels capables de rendre lessurfaces inorganiques biocompatibles afin d'immobiliser des biomolécules sans les dénaturer.- se doter d'outils innovants afin d'analyser la distribution de biomolécules sur la surface etd'évaluer leur activité biologique à l'échelle de la molécule unique.L'immobilisation a été réalisée sur des SAMs terminées par une fonction acide carboxylique.Pour imager les surfaces nous avons choisi la Microscopie Atomique de Force (AFM) qui permetd'obtenir des informations à l'échelle nanométrique et de mesurer des interactions moléculaires del'ordre du piconewton (10-12 N).Des CNTs, générés par dépôt chimique en phase vapeur, sont fixés sur une pointe AFM. Puis Ilssont biofonctionnalisés selon un protocole de trempage original afin d'obtenir une modificationchimique sélective de leur apex. Les interactions entre un récepteur, immobilisé sur la surface, et sonligand, lié de façon covalente au CNT, sont mesurées à l'échelle de la molécule uniqueDuring the development of biosensors, control of the surface on which the biomolecules areimmobilized is a crucial parameter for the reliability and reproducibility of the measurements. For thisPhD work, two main objectives were set:- obtain in a reproducible way functional organic films able to make inorganic surfacebiocompatible for the immobilization of biomolecules without any denaturation.- develop innovative tools in order to analyze the distribution of biomolecules on the surface etevaluate their biological activity at single molecule scaleThe immobilization step was done on SAMs terminated by a carboxylic acid function.In order to image surfaces, Atomic Force Microscopy (AFM) was chosen. This technique permits toobtain information at nanometric scale and to measure molecular interactions in the range ofpiconewton forces (10-12 N).MWCNTs were linked to a commercial AFM tip by micro-welding under optical microscopy. CNTswere biofunctionalized at the nanotube apex by an original dipping procedure.The interactions between a ligand, immobilized on the surface, and a receptor covalently linked to aCNT have been characterized
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Briand, Elisabeth. "Fonctionnalisation de surfaces d'or et greffage de protéines pour l'élaboration d'un immunocapteur." Paris 6, 2007. http://www.theses.fr/2007PA066013.
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Un immunocapteur consiste à utiliser les propriété de reconnaissance d'un anticorps pour détecter spécifiquement un analyte cible dans un milieu complexe. L'immobilisation de des anticorps (IgG) est cruciale et doit aboutir à un nombre optimal d'IgG accessibles. Ce travail a porté sur l'étude de l'interface biomolécules/surface d'or par quatre techniques d'analyse (PM-IRRAS, QCM, XPS et AFM). Trois modes d'immobilisation des IgG ont été testés, et leur liaison orientée par la protéine A (PrA) répond le mieux aux critères définis. Puis, l'influence de la première couche de thiols (ou SAM) sur l'activité des PrA a été étudiée. Trois SAM ont été comparées (une SAM pure et deux SAM mixtes). La nature chimique du thiol diluant influence l'adsorption des protéines et leur activité. Une couche hydrophile hétérogène favorise l'espacement des PrA, avec une couverture en anticorps optimale. Enfin, ce capteur a été testé pour détecter une toxine marine, l'acide okadaïque.
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Yousefalhaj, Nisreen. "Molecular engineering of azidoorganosilane-based SAMs for bioapplications." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0317.
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La capacité à contrôler les propriétés de surface et à réaliser l’ingénierie moléculaire de SAMs est déterminant pour permettre une immobilisation contrôlée des biomolécules, ce qui est d'une importance majeure pour le développement de nombreuses applications dans le domaine de la biologie. Dans ce travail, nous présentons d'abord la synthèse de différents types d'agents de couplage utilisés pour fournir deux types de SAM à terminaison azoture : portant un espaceur alkyle ou un espaceur urée de différentes longueurs. Ensuite, nous présentons en détail le dépôt des SAMs en utilisant différentes méthodes et stratégies dans différents solvants. Chaque changement a été étudié en profondeur pour étudier son effet sur la matière organique dans les SAMs et l'orientation des azotures, ainsi que la réactivité du groupe azido vis-à-vis de la réaction de clic CuAAC. Les modifications chimiques des surfaces ont été étudiées par les mesures PM-IRRAS, XPS, AFM et d'angle de contact. Ainsi, ce travail se termine par une liste relativement longue de SAMs bien définies à terminaison azoture, ce qui en fait de bons candidats pour diverses applications dans le domaine de la biologie. Certains des SAMs à terminaison azoture ont été utilisées avec succès pour immobiliser les GNL. La quantité de GNL varie à la surface en fonction de la nature des SAMs et de la quantité de groupes azotures. Cette plateforme montre des résultats prometteurs lorsqu'elle est testée pour la culture de cellules souchesThe ability to control surface properties and produce molecularly engineered SAMs is the key aspect for a precise biomolecules immobilisation in a preferred manner, which is of major importance for the development of many bioapplications. In this work, we provide first the novel synthesis of different types of coupling agents used to provide two types of azide-terminated SAMs: bearing an alkyl spacer or a urea spacer of different lengths. Then, we present in details the deposition of SAMs by using different methods and strategies in different solvents. Each change has been deeply studied to investigate its effect on the organic matter within the SAMs and the azide orientation, as well as the reactivity of the azido group towards the click reactions (CuAAC). The chemical modifications of the surfaces have been investigated by the PM-IRRAS, XPS, AFM and the contact angle measurements. Thus, this work ends up with a relatively big list of well-defined azide-terminated SAMs, as good candidates for various bioapplications. Some of azide-terminated SAMs have been successfully used to immobilise GNLs, resulting in differences of immobilised GNLs quantity on the surface depending on the nature of SAMs and the quantity of azide groups. This platform shows promising results when tested for stem cells culture
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Sojoudi, Hossein. "The synthesis, doping, and characterization of graphene films." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50125.
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Graphene, a two-dimensional counterpart of three-dimensional graphite, has attracted significant interest, due to its distinctive electrical and mechanical properties, for developing electronic, optoelectronic, and sensor technologies. In general, doping of graphene is important, as it gives rise to p-type and n-type materials, and it adjusts the work function of the graphene. This adjustment is necessary in order to control charge injection and collection in devices such as solar cells and light emitting devices. Current methods for graphene doping involve high temperature process or interactions with chemicals that are not stable. Moreover, the process of transferring graphene from its growth substrate and its exposure to the environment results in a host of chemical groups that can become attached to the film and alter its electronic properties by accepting or donating electrons/holes. Intentional and controllable doping of the graphene, however, requires a deeper understanding of the impact of these groups. The proposed research will attempt to clarify the unintentional doping mechanism in graphene through adsorption or desorption of gas/vapor molecules found in standard environments. A low temperature, controllable and defect-free method for doping graphene layers will also be studied through modifying the interface of graphene and its support substrate with self-assembled monolayers (SAMs) which changes the work function and charge carriers in the graphene layer. Furthermore, current methods of chemical vapor deposition synthesis of graphene requires the film to be transferred onto a second substrate when the metal layer used for growth is not compatible with device fabrication or operation. To address this issue, the proposed work will investigate a new method for wafer scale, transfer-free synthesis of graphene on dielectric substrates using new carbon sources. This technique allows patterned synthesis on the target substrate and is compatible with standard device fabrication technologies; hence, it opens a new pathway for low cost, large area synthesis of graphene films.
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Mesquita, Vincent. "Nanolithographie catalytique par microscopie à force atomique : étude des paramètres physico-chimiques." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4344/document.
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Les procédés lithographiques sont de nos jours très utilisés au sein de l’industrie de la microélectronique pour réaliser des matériaux fonctionnels de taille nanométrique. L’obtention de composants de taille de plus en petite (<100 nm) nécessite la mise en œuvre de nouveaux procédés de fabrication. Les travaux de recherches réalisés dans cette thèse portent sur l’étude d’un nouveau concept de lithographie par microcopie à force atomique (AFM). L'objectif principal est d'utiliser la pointe d’un AFM comme outil pour promouvoir des réactions catalysées sur une zone bien définie d’une surface greffée. De cette manière, diverses molécules ont pu être greffées sélectivement et spatialement pour conduire à des objets finis en 3 dimensions. Afin de mieux comprendre le mécanisme réactionnel, différents paramètres physico-chimiques ont été étudiés dans la première partie : vitesse de balayage de la pointe, force appliquée, distance interligne lors de la gravure du motif, largeur de lignes limites, durée de vie de la pointe catalytique et influence de la flexibilité du catalyseur présent sur la pointe. La deuxième partie consiste à la réalisation de nanostructures avec des molécules aux propriétés physico-chimiques particulières (optique, électrique, catalytique) ainsi qu’à la construction de nanostructures tridimensionnelles. Quelques résultats marquants sont l’obtention d’une largeur de ligne limite de 25 nm, d’une surface de greffage minimum de 480 µm² et d’une structure de forme pyramidale composée de trois niveaux moléculaires distinctsLithography processes are widely used in the microelectronics industry for the realization of functional materials of nanometric size. To obtain components increasingly small (<100 nm) the development of new manufacturing processes is requires. The research presented in this thesis concerns the study of a new concept of lithography by Atomic Force Microscopy (AFM). The main objective is to use the tip of an AFM as a tool to promote catalysed reactions on a well defined zone of a grafted surface. In this way, diverse molecules could be grafted selectively and spatially to form three dimensioned objects. To better understand the reaction mechanism, different physico-chemical parameters were studied in the first part: the scanning speed of the tip, the strength applied, the interline spacing during the engraving pattern, the width lines limits, the life time of the catalytic tip and the influence of the catalyst flexibility coated to the tip. The second part consists in the realization of nanostructures with molecules that have particular physico-chemical properties (optical, electric, catalytic) and the construction of three-dimensional nanostructures. Some pertinent results are the achievement of line width of 25 nm, a minimum grafted surface of 480 µm² and the formation of a structure of pyramidal shape constituted of three different molecular levels
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Wang, Qiuming. "Structure, Aggregation, and Inhibition of Alzheimer's B-Amyloid Peptide." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1370282744.
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Mousli, Yannick. "Synthès de nano-films bio-fonctionnels pour l'immobilisation spécifique d'espèces biologiques." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0840/document.
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Le contrôle des propriétés physicochimiques et de l’état de surface des solides constituent un enjeu majeur pour le développement des biotechnologies, et notamment des bio-capteurs. Pour des applications en analyse et diagnostic biologique, la fonctionnalisation des surfaces à base de silicium peut être réalisée grâce à la formation d’un nano-film organique appelé SAM (Self-Assembled Monolayer). L'objectif de ce travail de thèse est ainsi de synthétiser des monocouches sur des substrats de silice afin de les rendre biofonctionnels en vue de développer une plateforme de biodétection polyvalente.Pour ce faire, deux types d'agents de couplages ont été envisagés : l'un possédant un motif azoture et l'autre une biotine. L’obtention de ces deux types de molécules a fait l’objet d’un travail de synthèse permettant d’aboutir à de nouveaux organosilanes fonctionnels directement greffables sur des surfaces de SiO2. La biofonctionnalité est introduite sur le substrat par la biotine, soit directement lors de la formation de la SAM, soit par chimie click sur les monocouches fonctionnalisées par des azotures.Les différentes surfaces obtenues ont ensuite été caractérisées par Spectroscopie Infrarouge de Réflexion–Absorption par Modulation de Polarisation (PM-IRRAS) et par Microscopie de Force Atomique (AFM). La bioactivité des SAMs biotinylées a enfin été évaluée par un protocole mettant en jeu une streptavidine modifiée par une enzyme (la HRP) capable de catalyser des réactions d’oxydoréduction de molécules chromogènesControl of surface physicochemical properties is a key aspect for the development of many biotechnological tools, such as biosensors. For analysis and diagnostic, the functionalization of silica-based surfaces may be carried out through the creation of an organic nano-film named a Self-Assembled Monolayer (SAM). The main goal of this PhD work is thus to synthesize monolayer on SiO2 substrates in order give them biofunctionality, aiming at developing a versatile biodetection platform.In order to do so, we focused on the synthesis of two types of coupling agents, either bearing an azide moiety or a biotin. This organic synthesis work led to two new sorts of functional organosilanes which can be directly grafted onto silica surfaces. Biofunctionality itself is introduced by the biotin, either through the formation of the monolayer or through click chemistry on azide-functionalized SAMs.Said surfaces were then fully characterized using Polarization Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRRAS) an Atomic Force Microscopy (AFM). Bioactivity of biotinylated surfaces was then monitored using streptavidin conjugated with HRP in order to catalyze the redox reaction of chromogenic substrates