Dissertations / Theses on the topic 'Graphene-based detector'

This study reports the synthesis of graphene by oxidizing graphite to graphite oxide using H2SO4 and KMnO4 and reducing graphene oxide to graphene by using NaBH4. Graphene was then characterized using FT-IR, TEM, AFM, XRD, Raman spectroscopy and solid state NMR. Nafion-Graphene in combination with a mercury film electrode, bismuth film electrode and antimony film electrode was used as a sensing platform for trace metal analysis in 0.1 M acetate buffer (pH 4.6) at 120 s deposition time, using square-wave anodic stripping voltammetry (SWASV). Detection limits were calculated using 3σblank/slope. For practical applications recovery studies was done by spiking test samples with known concentrations of metal ions and comparing the results to inductively coupled plasma mass spectrometry (ICPMS). This was then followed by real sample analyses.

Terahertz (THz) radiation has become increasingly important in many scientific and commercial fields in recent years. It possesses many remarkable features resulting in an increased use of THz radiation for various applications, like biomedical imaging, security screening, and industrial quality control. The capability of these applications depends directly on the availability of powerful THz sources and high-responsivity, fast THz detectors. Current commercial products used to detect THz radiation, like Golay cells and pyroelectric detectors, have only slow detection rates and poor sensitivities. Other commercial THz detectors, like bolometers, are more sensitive but require liquid helium cooling. In this thesis, two types of room-temperature high-responsivity graphene-based THz detectors are presented, relying on the unique properties of graphene and the function of plasmonic antenna arrays which boost the interaction between THz waves and graphene. Graphene has been demonstrated as a promising material for THz detection. However, the challenge is its insufficient light absorption that largely limits the responsivity. The first design is based on an array of planar antennas arranged in series and shorted by graphene squares. Highly efficient photodetection can be achieved by using the metallic antenna to simultaneously improve both light absorption, as resonant elements, and photocarrier collection, as electrodes. The device has been characterized with quantum cascade lasers, yielding a maximum responsivity of ~2 mA/W at 2 THz. The second detector is based on an array of interdigitated bow-tie antennas connected in parallel and shunted by graphene squares. The arms of the bow-tie antennas were made of two metals with different work functions to create a built-in electric field and improve the responsivity. The device has been characterized and yields a maximum responsivity of ∼34 μA/W at 2 THz. Efficient THz imaging is presented by integrating the detector in a QCL-based THz imaging system.

Obiettivo della tesi è la ricerca di un metodo volto a migliorare le attuali prestazioni dei sensori di gas realizzati in grafene. Negli ultimi anni il grafene ha attirato particolare attenzione nel campo dei sensori di gas. Tuttavia, l’utilizzo del grafene presenta limitazioni che rendono difficile lo sviluppo di sensori utilizzabili commercialmente. Tra queste, la mancanza di selettività, nonché la difficoltà del segnale a raggiungere la saturazione e a ritornare al livello iniziale durante la fase di ripristino, rappresentano i maggiori ostacoli. La funzionalizzazione del grafene risulta essere tra i metodi più promettenti per rimediare alle predette limitazioni. Nella tesi, l’oggetto della ricerca è un resistore chimico, il cui materiale sensibile è costituito da grafene multi-strato realizzato tramite deposizione chimica da fase vapore. Il processo di funzionalizzazione scelto si basa sulla deposizione di nanoparticelle di oro sulla superficie del grafene multi-strato. Le caratteristiche fisiche ed elettriche del materiale e le prestazioni del sensore vengono analizzate e confrontate prima e dopo il processo di funzionalizzazione. In particolare, la tesi sviluppa i seguenti punti: Nel Capitolo 1 vengono introdotte le caratteristiche fisiche ed elettriche del grafene, e le sue potenzialità nelle applicazioni di tipo "gas-sensing". Nel Capitolo 2 viene presentato lo stato dell’arte sul processo di funzionalizzazione. Il Capitolo 3 contiene le analisi delle caratteristiche fisiche ed elettriche del materiale, esaminando le differenze riscontrate dopo la funzionalizzazione. I risultati dei test su gas, prima e dopo la funzionalizzazione, sono presentati nel Capitolo 4. SI usa NO2 come "target gas", N2 come gas portante. Per alcuni test, una percentuale di umidità relativa viene aggiunta al flusso di gas. Infine, i risultati vengono confrontati e discussi in dettaglio.

Ce travail nous a permis de réaliser une étude de capteurs de gaz et d’humidité à base de graphène. Cette étude pourrait être utile non seulement pour améliorer les performances des capteurs à base de graphène mais aussi pour mieux comprendre l’interaction entre le graphène et les molécules de gaz. Ceci semble indispensable pour faire avancer les applications du graphène comme un matériau prometteur pour la détection des gaz. Des avancées significatives ont été présentées au niveau de la fabrication de ces capteurs, leurs différentes caractérisations électriques ainsi que d’autres techniques employées pour analyser le mécanisme contrôlant la détection des molécules de gaz/vapeur. Ces outils ont été mis en place pour concevoir et fabriquer plusieurs structures de capteur en utilisant différents substrats support du graphène d’une part et en modifiant les propriétés du graphène par utilisation des produits chimiques d’autres part. La caractérisation de ces capteurs sous différents environnements a permis de comparer les différentes réponses des capteurs et d’en tirer plusieurs conclusions sur le fonctionnement de ces dispositifs. En effet, le Mica, un substrat lisse et transparent, a été utilisé comme substrat pour le graphène. Le dopage induit par le mica a été étudié ainsi que son impact sur la sensibilité du graphène au gaz d’ammoniac. Ceci a permis de mettre en évidence le fait que le substrat joue un rôle important pour la détection de l’ammoniac. De plus, ces capteurs fabriques sur mica et SiO2 ont été testés sous différentes conditions de températures et d’oxygène. Dans une autre approche, un polymère a été utilisé pour doper le graphène. Une étude détaillée a été menée pour analyser le comportement de ce graphène fonctionnalisé par rapport aux molécules d’eau. Ces nouveaux résultats expérimentaux obtenus pendant cette thèse constituent un bon support à plusieurs résultats théoriques établis et permettent d’optimiser la conception des capteurs de gaz à base de graphène pour des meilleures performances<br>In this research, we report on a study of graphene based gas and humidity sensors. This study could be useful not only to improve the performance of graphene based sensors but also to better understand the interaction between graphene and gas molecules. This seems necessary to promote the applications of graphene as a promising material for gas sensing. Significant advances have been made to design and fabricate these sensors: the different electrical characterizations as well as other techniques used to analyze the mechanism controlling the detection of gas/vapor molecules. These tools have been set up to design and manufacture various sensor structures using different underlying substrates for graphene on one hand and chemical modification of graphene properties on the other hand. The characterization of these sensors under different environments was used to compare the different responses of the sensors and draw several conclusions about gas sensing mechanism. Indeed, Mica, a smooth and transparent substrate, was used as a supporting substrate for graphene. Doping induced to graphene by mica and its impact on graphene sensitivity to ammonia gas were studied. This has made it possible to highlight the fact that the substrate plays an important role for the detection of ammonia. In addition, these sensors made on mica and SiO2 were tested under a variety of temperatures and oxygen. In another approach, a polymer was used to dope graphene. A detailed study was realized about the behavior of water molecules on functionalized graphene. The obtained experimental results, reported for the first time, represent a good support for several theoretical studies already made and could be used to optimize the design of graphene based gas sensors

Les attaques bioterroristes sont devenues plus fréquentes ces dernières années et le large éventail d’agents bioterroristes en fait un problème important à résoudre. La ricine appartient à la famille des protéines inactivant les ribosomes (RIP). Les RIP sont des toxines biologiques, solubles dans l’eau, qui peuvent être facilement extraites de plantes (ricine de Ricinus communis et abrine d’Abrus precatorius) ou de bactéries (toxine de Shiga). La ricine est composée de deux chaînes: la chaîne A de la ricine, une N-glycosidase induisant la toxicité par élimination de l’adénine (action de dépurination) de l’ARNr 28S des sous-unités ribosomales 60S, inhibant la synthèse protéique, et la chaîne B, une lectine qui se lie aux fragments de sucre spécifiques sur la membrane extracellulaire, assurant l'absorption de la toxine. Comme ils inhibent la synthèse des protéines, en fonction de la voie d'absorption et de la dose reçue, la mort peut survenir. En l'absence de contre-mesures efficaces, les méthodes de détection de ces toxines doivent être rapides, fiables, sélectives et sans aucune ambiguïté. Les méthodes actuelles qui sont principalement basées sur des méthodes comme le SERS, l’ELISA, la Colorimétrie et la SPR ne répondent pas à toutes ces exigences. Même si la spectrométrie de masse a été utilisée pour la détection de la ricine, elle ne peut pas être réalisée sans une longue et fastidieuse préparation d'échantillon. Dans ce travail, nous avons montré comment les matériaux à base de carbone (nanomurs de carbone) pourraient être appliqués comme matériaux nanostructurés pour la détection spécifique, rapide et simple de la ricine par désorption/ionisation laser de surface pour la détection par spectrométrie de masse (SALDI-MS). Tout d'abord, l'adéquation des nanoparticules de carbone en tant que bonne surface SALDI a été initialement étudiée pour des biomolécules plus petites. En ce qui concerne les protéines, la littérature a montré qu'elles sont difficiles à ioniser et à détecter avec la méthode SALD-MS, en raison de leur grand poids moléculaire. La capacité des CNWs à désorber et à ioniser les protéines a nécessité de nombreuses étapes d’optimisation. Pour ce faire, le cytochrome C a été utilisé comme protéine modèle. Enfin, des nanomurs de carbone alignés verticalement ont ensuite été modifiés à l'aide de sucres à lectine spécifiques (galactosamine), pour la détection spécifique de la chaîne B de la ricine dans des échantillons réels, tels que des boissons sans alcool et du sérum sanguin. Nous avons obtenu une limite de détection (80 ng/0.5 μL) soit trois fois inférieure à la dose létale médiane la plus faible (DL50 = 10 μg/kg). Cette détection peut être réalisée dans les 10 min. Dans la dernière partie, des résultats préliminaires concernant la mise au point d'outils analytiques bimodaux seront présentés. Il s'agit de combinaisons telles que: SPR (résonance plasmonique de surface)-MS, SERS (Spectroscopie Raman Exaltée de Surface)-MS et EC(Électrochimie)-MS. Une attention particulière a été portée sur la SPR-MS car elle permet d’obtenir des interactions quantitatives et moléculaires en temps réel (SPR) et une identification structurelle des analytes (MS). Les méthodes de dépôt suivantes (de matériaux de type graphène) sont avérées appropriées pour la détection des protéines: la méthode de surfactant à bulle d'oxyde de graphène, le transfert par voie humide de graphène CVD et le dépôt électrophorétique de graphène.Cette thèse décrit pour la première fois le développement d'un capteur de type SALDI-MS, capable de détecter la ricine à une dose inférieure à la dose mortelle chez l'homme et d'apporter ainsi une contribution importante à la lutte contre d'éventuelles attaques terroristes. L'étude systématique de différents paramètres qui influencent ce processus LDI-MS est également présenté. Les techniques bimodales présentent des alternatives intéressantes permettant de créer des outils analytiques plus puissants<br>Bio-terroristic attacks have become more frequent in the past years and the wide range of bio-terroristic agents makes this an important issue to overcome. Ricin is part of the ribosome-inactivating proteins (RIP). RIPs are vegetable toxins, water soluble, which can be easily extracted from plants (ricin from castor beams, abrin from rosary pea) or from bacteria (Shiga toxin). These proteins are composed of two chains: ricin A chain, a glycosidase that insures the toxicity by removal of adenine (depurination) from the RNAr 28S from the 60S ribosomal subunits, followed by the inhibition of protein synthesis, and ricin B chain, a lectin that binds to specific sugar moieties on the surface of the cells, assuring transportation the cell uptake. As they inhibit protein synthesis, depending of the administration take-up (oral, inhalation, intravenously) and the dose received, cell death also occurs. In the absence of efficient counter measurements, detection methods of these toxins have to be fast, reliable, selective and suitable, especially pre-assimilation analysis. The current methods (based on SERS, ELISA, Colorimetric, SPR and MS) do not overcome all these requirements. Even though mass spectrometry was used for ricin detection, it cannot be performed without long and tedious sample preparation. In this work, we describe how carbon-based materials (carbon nanowalls and others) can be used as nanostructured materials for specific, rapid and straightforward ricin-like proteins detection, using surface assisted laser/desorption ionization mass spectrometry (SALDI-MS). The suitability of the carbon nanowalls (CNWS) was proven initially for other smaller bio-molecules.When it comes to proteins, they are hard to ionize and detect using SALD-MS, due in part to their big molecular weight. The ability of CNWs to desorb and ionize proteins required a lot of optimization steps of the SALDI-MS method. A systematic optimization was done using a model protein, the cytochrome C. From this, we were able, for the first time, to detect Ricin B chain without the use of organic matrix. To go further in improving Ricin detection performances, carbon nanowalls were then covalently modified using specific lectin sugars (galactosamine) and the ability to detect Ricin B chain in real samples such as soft drinks and blood serum was demonstrated within10 minutes. We obtained a limit of detection (80 ng/0.5 μL) that is 3 times lower than the lowest median lethal dose (LD50 = 10 μg/kg) Multifunctional surfaces are described as perspectives for more powerful bimodal analytical tools, by combining two techniques, such as: SPR(Surface Plasmon Resonance)/SALDI-MS, SERS(Surface Enhanced Raman Spectroscopy)/SALDI-MS and EC(Electrochemistry)/SALDI-MS. Special attention was focused on SPR/SALDI-MS as it can achieve both quantitative and molecular interactions in real-time (SPR) and precise identification of the analytes (MS). Different depositions methods of graphene-like materials were studied to ensure a good surface coverage of the substrate and the followings methods were suitable for protein detection: bubble surfactant method of graphene oxide, wet transfer of CVD pristine graphene, electrophoretic deposition of graphene.In this thesis, we described the first world wide ricin-like proteins SALDI-MS sensor, which is able to detect below the lethal dose in humans and bring an important contribution to the fight against eventual terroristic attacks. The systematic study of different parameters that influence this LDI-MS process is also presented. The dual surfaces studied, in particular the SPR/MS bimodal techniques, presented reliable consistency for further approaches in creating more powerful analytical tools

The large-scale abuse and addiction of narcotics such as amphetamine and cocaine have become a global problem. In this project, we innovatively use graphene quantum dots (GQDs) as a fluorescent sensor to detect and quantify amphetamine and cocaine. This technology will have broad forensic application prospects. Compared with metallic quantum dots, graphene quantum dots are green and safe, with excellent bio-compatibility and low toxicity. We used undoped and N-doped GQDs as fluorescent sensing probes for the detection of amphetamine and cocaine, respectively. Using FTIR and FL as characterization methods, the fluorescence luminescence of GQDs under multiple excitation wavelength bands was studied and compared with the fluorescence after adding drugs. The experimental results show that the N-doped GQDs has a higher response to the binding substance. The detection concentration of amphetamine ranges from 5 µM to 5 mM, and the detection concentration of cocaine ranges from 10 µM-10 mM. Within this range, the fluorescence peak intensity ratio and the drug concentration have a two-stage linear negative correlation.<br>Storskaligt missbruk och missbruk av narkotika som amfetamin och kokain har blivit ett globalt problem. I detta projekt använder vi innovativt grafenkvantprickar (GQDs) som en fluorescerande sensor för att detektera och kvantifiera amfetamin och kokain. Denna teknik kommer att ha breda rättsmedicinska applikationsmöjligheter. Jämfört med traditionella kvantprickar är grafenkvantprickar gröna och säkra, med utmärkt biokompatibilitet och låg toxicitet. Vi använde odopade och N-dopade GQD: er som fluorescerande avkännande sonder för detektion av amfetamin respektive kokain. Med användning av FTIR och FL som karakteriseringsmetoder studerades fluorescens luminiscens hos GQD under flera exciteringsvåglängdsband och jämfördes med fluorescensen efter tillsats av läkemedel. De experimentella resultaten visar att den N-dopade GQD har ett högre svar på den bindande substansen. Detekteringskoncentrationen av amfetamin sträcker sig från 5 µM till 5 mM, och detektionskoncentrationen av kokain varierar från 10 µM-10 mM. Inom detta område har fluorescens toppintensitetsförhållandet och läkemedelskoncentrationen en tvåstegs linjär negativ korrelation.

A specific double-stranded DNA sensing system is of great interest for diagnostic and other biomedical applications. Zinc finger domains, which recognize double-stranded DNA, can be engineered to form custom DNA-binding proteins for recognition of specific DNA sequences. As a proof of concept, a sequence-enabled reassembly of TEM-1 β- lactamase system (SEER-LAC) was previously demonstrated to develop zinc finger protein (ZFP) arrays for the detection of a double-stranded bacterial DNA sequence. Here, we implemented the SEER-LAC system to demonstrate the direct detection of pathogenspecific DNA sequences present in E. coli O157:H7 on the lab-on-a chip. ZFPs customdesigned to detect shiga toxin in E. coli O157:H7 were immobilized on the cyclic olefin copolymer (COC) chip, which can function as a non-PCR based molecular diagnostic. Pathogen-specific double-stranded DNA was directly detected by engineered ZFPs immobilized on the COC chip, providing a detection limit of 10 fmole of target DNA in colorimetric assay. Therefore, in this study, we demonstrated a great potential of ZFP arrays on the COC chip for further development of a simple and novel lab-on-a chip technology for detection of pathogens. Antibiotic resistance is a serious, and rapidly growing global threat. Here, we designed a novel screening method to detect antibiotic resistance genes (ARGs) in bacteria using a graphene oxide-based biosensor utilizing engineered ZFPs. Two-dimensional graphene oxide (GO) sheet possesses unique electronic, thermal, and mechanical properties. The quenching ability of GO can create novel methods for detection of biomolecules. Our approach utilizes quenching of fluorescence signal by GO in the absence of target ARGs, but restoring the signal in the presence of target ARGs. Quantum dot (QD)- labeled ZFP can bind to GO via stacking interactions of aromatic and hydrophobic residues in conjunction with hydrogen bonding interaction between hydroxyl or carboxyl groups of GO and hydroxyl or amine groups of the protein. Due to fluorescence resonance energy transfer (FRET) between QD and GO when they are in close proximity, fluorescence signal of QD-labeled ZFP is expected to be quenched. In the presence of target DNA, the bound DNA-protein complex is released from GO, restoring the fluorescence signal.

Philosophiae Doctor - PhD<br>The need for clean, non-toxic drinking water supplies, free of pollutants and metal contamination is vital in impoverished areas and the developing world alike. With this in mind, the development of accurate, inexpensive, portable and simple devices for remote sensing applications is therefore pivotal for early detection and the prevention of illnesses. Over the last two decades, adsorptive stripping voltammetry (AdSV) has emerged as a superior detection method over common analytical techniques due to its low-cost instrumentation, unskilled labour and ability to detect a wide range of analytes.<br>2020-08-31

La nanotechnologie est un domaine en voie d'expansion qui a attiré l'attention de la recherche en raison de ses applications potentielles illimitées. La technologie des ondes millimétriques est un autre domaine intéressant qui joue un rôle de premier plan dans le développement des systèmes de communications sans fil. La combinaison de ces deux champs de recherche avancée, donne naissance à l'innovation du Dispositif Ratchet qui est une nouvelle application qui représente un vrai défi. Ce dispositif est de taille nanométrique et son concept d'opération consiste à générer une tension DC lorsque le dispositif, basé sur le gaz d'électron bidimensionnel, est rayonné par l'énergie des micro-ondes. L'objectif de cette thèse est d'essayer d'améliorer la réponse du dispositif, ce qui ouvre de nouvelles perspectives dans la fabrication des détecteurs de champ à haute fréquence et à l'échelle nanométrique. Malheureusement, les Dispositifs Ratchet actuels, basés sur des hétérostructures de semiconducteurs, réalisés jusqu'à présent fonctionnent à basse température pour assurer une grande mobilité électronique. Cette condition nécessite l'utilisation d'un setup expérimental complexe qui a un grand impact sur la tension induite et sur la reproductibilité du phénomène Ratchet observé. Dans ce contexte, le travail effectué dans le cadre de cette thèse a abordé ce problème en deux parties. La première partie concerne l'analyse électromagnétique du setup expérimental. Ceci a été réalisé par la mise en oeuvre des simulations électromagnétiques intenses. D'autre part, différentes solutions ont été proposées afin d'optimiser le setup et ainsi améliorer la tension Ratchet produite. Outre l'étude électromagnétique, certaines mesures de modulation ont été réalisées pour tester la faisabilité du Dispositif Ratchet comme un démodulateur d'amplitude. La deuxième partie de cette thèse traite l'étude de la matière qui compose le Dispositif Ratchet. Récemment, le graphène commence à envahir le monde scientifique et technologique avec ses fascinantes propriétés électroniques, tels que sa mobilité d'électrons élevée à température ambiante, où les matériaux conventionnels sont en train de confronter des obstacles. En conséquence, l'idée de fabriquer un Dispositif Ratchet à base de graphène au lieu des hétérojonctions de semiconducteurs, a été introduite. Plusieurs modèles de conception, caractérisation et mesures RF ont été accomplis en vue d'obtenir un Dispositif Ratchet fiable approprié pour de nombreuses applications pratiques à la température ambiante, dans la gamme de fréquences micro-ondes et pourraient s'étendre à la bande térahertz<br>Nanotechnology is a growing field that has attracted significant research attention due to its unlimited potential applications. Millimeter wave technology is another interesting field that plays a leading role in the development of wireless communications systems. Combining these two advanced research fields together, has given rise to the innovation of the Ratchet Device which is now a new challenging application. This device has a nanoscale size and its concept of operation consists of generating a DC voltage when radiating a two-dimensional electron gas based device with microwave energy. The aim of this thesis is in trying to improve the device response and hence opening new perspectives in the fabrication of high frequency field detectors on the nanoscale level. Unfortunately, the current Ratchet Devices, based on semiconductor heterostructures, realized till now, operate at low temperatures to ensure high electron mobility. This condition necessitates the use of a complex experimental setup that has a great impact on the induced voltage and on the reproducibility of the observed Ratchet phenomenon. In this context, the work performed within the framework of this thesis has addressed this problem in two parts. The first part concerns the electromagnetic analysis of the experimental setup behavior. This has been achieved by implementing intensive full wave electromagnetic simulations. Different solutions have been proposed to optimize the setup and thus enhance the Ratchet voltage produced. In addition to the electromagnetic study, some modulation measurements have been performed to test the feasibility of the Ratchet Device as an amplitude demodulator. The second part of this thesis deals with the study of the material composing the Ratchet Device. Recently, graphene has started to invade the scientific and the technological world with its fascinating electronic properties, such as its high electron mobility at room temperature, which distinguishes it from conventional materials that typically collide with obstacles. As a result, the idea of fabricating a Ratchet Device based on graphene instead of semiconductor heterojunctions has been introduced. Several design models, characterizations and RF measurements have been performed in order to obtain a reliable Ratchet Device suitable for many practical applications at room temperature. This has been done in the microwave frequency range and can also extend to the terahertz band

Technologies laser pour l’élaboration de matériaux carbonés pour microsystèmes analytiques environnementaux. Pas de résumé en français fourni<br>Amorphous carbon nitride (a-CzN) material has attractor much attention in research and development. Recently, it has become a more promising electrode material than conventional carbon based electrodes in electrochemical and biosensor applications. Nitrogen containing amorphous carbon (a-C:N) thin films have been synthesized by femtosecond pulsed laser deposition (fs-PLD) coupled with plasma assistance through Direct Current (DC) bias power supply. During the deposition process, various nitrogen pressures (0 to 50 Pa) and DC bias (0 to -350 V) were used in order to explore a wide range of nitrogen content into the film. The structure and chemical composition of the films have been studied by using Multi-wavelength (MW) Roman spectroscopy, electron energy-loss spectroscopy (EELS), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTBM). The surface morphology has been studied by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Increasing the nitrogen pressure or adding a DC bias induced an increase of the N content, up to 28 at.%. Nitrogen content increase induces a higher sp2 character of the film. However DC bias has been found to increase the film structmal disorder, which was detrimental to the electrochemical properties. Indeed the electrochemical measurern-ts, investigated by cyclic voltammetry (CV), demonstrated that the a-CzNfilms show better electron transfer kinetics, reversibility and excellent reproducibility than the pure a-C films. Electrochemical grafting from diazoniurn salts was successfully achieved on this film, with a surface coverage of covalently bonded molecules close to the dense packed monolayer of ferrocene

碩士<br>國立臺南大學<br>材料科學系碩士班<br>104<br>There are many ways to produce ultraviolet detectors with zinc oxide. Since zinc oxide nanoparticles have high photon sensitivity, they are highly valued in the production of sensing elements. Normally, the process of manufacturing UV detector with zinc oxide nanoparticles is simple. However, its high contact resistance, high working voltage, and large time constant during photon detecting may limit its applicability. Studies have shown that graphene has the property of high electron mobility, large current, but little response to light. Combined the advantages of both materials, this study aims to produce a high efficiency UV detecting element by spreading zinc oxide nanoparticles on low resistance graphene nanoribbon and study changes in its optical and electrical properties. The current of the hybrid detector decreases significantly in responding to UV light by up to 50 percent.

碩士<br>國立臺南大學<br>材料科學系碩士班<br>107<br>This study successfully combines the electrical conductivity of graphene with the photoelectric properties of zinc oxide to fabricate a novel heterostructure for ultraviolet (UV) detection. Zinc oxide nanoparticles (ZnO NPs) with high ultraviolet (UV) sensitivity were grown on graphene across two electrodes to modulate the electron behavior in the graphene. A UV detector built in this way need only a voltage bias 0.01V. Due to the extremely thin characteristics of graphene, when UV is irradiated on the electrically insulated ZnO NPs above the graphene, the photogenerated electrons form a localized electrostatic field on the surface of the particles, which significantly suppressing the graphene current. This method is different from the conventional light detection mechanism of semiconductor, which as the light is illuminated, the photo current rises. The research result can provide an alternative for the light sensing technology.

Dissertação de mestrado em Biofísica e Bionanossistemas<br>Ischemic stroke is one of the leading causes of dead and morbidity in the world. The only FDA (U.S. Food and Drug Administration) approved therapy for ischemic stroke victims is the thrombolytic therapy, which increases the risk of hemorrhagic transformation, i. e., the transformation of an ischemic stroke into a hemorrhagic one. A large number of proteins have been identified as predictive biomarkers of this event. Therefore, biosensing applications are at development to achieve fast, sensitive and specific detection of the identified blood biomarkers. Recently a new approach to graphene field effect transistors was proposed by Vieira et al., with polarization via electrolyte/solution, Electrolyte-Gated Graphene Field Effect Transistors (EG-GFETs). The developed architecture holds a concentric, in plane circular gate, allowing easy fabrication upscaling of the complete devices, and the transistor channel is exposed which is only possible due to the use of graphene as the channel material, since it is chemically very stable. The high sensitivity of graphene to electric charges and fields can thus be explored for biosensing applications, since changes in the electrolyte near graphene will translate into changes in the transistors electrical characteristics, in particular in the transfer curves. However, the problem for graphene is the lack of specificity, since the EG-GFETs will respond to any charged molecule present in the graphene neighbourhood, irrespectively of the chemical structure that contains it. This way, the proposed project aimed to functionalize graphene to create a specific detection interface for biosensing applications, in particular for the detection of ischemic stroke related biomarkers. The graphene functionalization was studied for the detection of one of the biomarkers that help predict hemorrhagic transformation, MMP-9 (Matrix Metalloproteinase 9). In a first phase of the project, it was used graphene on top of Si/SiO2 wafers. The functionalization strategy was studied, and a non-covalent functionalization of graphene was achieved by using a pyrene derivative. It was obtained a specific detection of MMP-9, with efficient blocking of the areas without antibodies. The studied strategy was then applied to EG-GFETs and the influence of the functionalization agents (buffer, biomolecules, …) on the transistors characteristics was studied. We found that the functionalization had no significant effect on the devices electrical characteristics. MMP-9 at different concentrations was then added to functionalized devices and the transfer curves showed an evident shift of the Dirac point to lower gate voltages, related with the MMP-9 detection by graphene. The successful functionalization of graphene with a target specific detection showed promising results from the electrical detection platform to future biosensing applications.<br>O AVC (acidente vascular cerebral) isquémico é uma das maiores causas de morte e incapacidade a longo prazo no mundo. No entanto, o tratamento dos pacientes com AVC isquémico é muito restrito, existindo apenas um tratamento clinicamente aprovado, a terapia trombolítica. No entanto, a aplicação desta terapia em pacientes com AVC isquémico aumenta o risco de transformação hemorrágica, ou seja, o AVC isquémico transforma-se num AVC hemorrágico. Nos últimos anos, um grande número de proteínas tem sido associado com o desenvolvimento da transformação hemorrágica, permitindo prever este acontecimento. Mas para que essas proteínas, biomarcadores, possam funcionar para a prevenção deste efeito é necessário desenvolver sistemas de deteção rápidos, sensíveis e específicos. Uma nova configuração de transístores de efeito de campo de grafeno polarizados via eletrólito/solução, os EGGFETs, foi desenvolvida recentemente. Esta nova arquitetura de transístores é completamente integrada no mesmo plano, com uma porta concêntrica e no plano do restante dispositivo, permitindo a produção em grande escala, e com o canal de grafeno exposto ao ambiente, o que só é possível devido à sua estabilidade química. Com o grafeno exposto, a sua elevada sensibilidade a cargas elétricas pode então ser explorada para aplicações em biossensores, uma vez que mudanças na composição do eletrólito junto do grafeno, serão traduzidas em alterações nas características elétricas dos transístores, nomeadamente nas curvas de transferência. No entanto, o grafeno apresenta falta de especificidade, provocando alterações no sinal dos EGGFETs na presença de qualquer carga elétrica, independentemente da sua estrutura química. Assim sendo, o que foi proposto neste projeto foi a funcionalização do grafeno para a criação de uma interface de deteção específica para aplicação a biossensores, em particular para a deteção de biomarcadores relacionados com o AVC isquémico/Transformação Hemorrágica. Foi então estudada a funcionalização de grafeno para a deteção de um dos biomarcadores preditores da transformação hemorrágica, MMP-9. Na primeira fase do projeto foram estudados substratos de grafeno. A estratégia de funcionalização foi estudada e conseguiu-se alcançar a funcionalização não-covalente do grafeno através do uso de um derivativo de pireno. Também se obteve a deteção específica de MMP-9, com um bloqueio eficiente das áreas sem anticorpos específicos. Esta estratégia foi então aplicada aos EG-GFETs e verificou-se que os agentes de funcionalização (buffer, biomoléculas, …) não afetava significativamente as suas características elétricas, mas que quando expostos ao biomarcador, MMP-9, em diferentes concentrações, havia um evidente desvio do ponto de Dirac para voltagens de gate mais baixas, desvio relacionado com a interação entre a MMP-9 e o grafeno. Foi alcançada a funcionalização do grafeno, com deteção especifica do biomarcador, e com resultados muito promissores relativamente aos EG-GFETs como uma futura plataforma deteção para biossensores.

碩士<br>明志科技大學<br>材料工程系碩士班<br>105<br>In this study, we propose a novel biosensor using O/H low-damage plasma treatment to modify stacking double-layer CVD-graphene. Only the top layer of graphene was oxidized, while the bottom layer graphene was maintained as a transmission layer. The sample was referred to as top-oxide double layer graphene (TODLG). Chemically synthesized probe DNA was immobilized on the TODLG electrode by chemical covalent bond-amide bonding to facilitate hybridization with miRNA-21. Current-voltage measurements revealed the relative change in resistance at different concentrations of miRNA-21 (10 pM–100 nM). The relative change in resistance increased as miRNA-21 concentration increased. However, TODLG was not perfectly stacked, and the prepared sensing element showed poor detection capability (linearity of 0.9492 and detection limit of 0.496 nM). Thus, the detection capacity was not sufficient (linearity of 0.9492 and detection limit 0.423 nM). To improve the interaction between layers, we applied the rapid thermal annealing process and confirmed the results by Raman detection and sensing ability. We confirmed that rapid thermal annealing can improve coupling between the layers and enhance the sensitivity of sensing (linearity of 0.9958, detection limit of 60.22 pM). Examination of electrode size revealed that shortened electrode spacing and increased electrode width effectively improved sensor sensitivity (linearity of 0.996 and detection limit of less than 10 pM) and showed high reproducibility. Furthermore, the TODLG electrode not only showed good biocompatibility, but also can clinically be used for the early detection of the cancer by directly detecting plasma miR-21 in clinical samples without the need for sample preparation. Based on these positive results for the TODLG platform, it is possible to detect specific microRNA fragments by altering the probe design.

碩士<br>國立清華大學<br>奈米工程與微系統研究所<br>102<br>Food poisoning is an obstinate global issue. The rapid detection of pathogens before food intake can be a good strategy to avoid being infected. However, conventional methods usually take more than two days for pathogens incubation and detection. Vancomycin can capture the bacteria using the linkage of five hydrogen bonds between the heptapetide backbone and the D-alanyl-D-alanine dipeptide extending from the cell wall of bacteria. In this study, we develop a rapid bacteria detection device based on the vancomycin modified large graphene oxide (VLGO) transistor. At first, a single-layered graphene was prepared by chemical vapored deposition method3 and transferred onto PET as the substrate. Second, we modified the surface by oxygen plasma treatment. Further, the surface of graphene was functionalized with vancomycin. Finally, the pads of source and drain were deposited onto the VLGO surface. The device is demonstrated to be simple, rapid and reusable bydropping a 10µL solution onto surface of VLGO followed by applying a voltage bias between source/drain. As a p-type transistor, the density of the holes on VLGO surface increases once the bacteria were captured by vancomycin. The detection readout is obtained by comparing the conductance before and after the applying the sample solution onto the VLGO transistor. The results demonstrated that the detection limit is 16 cfu/ml, 11cfu/ml for S.auresus and E.coli, respectively. The response time is 15 minutes. The device is often rapid detecting bacteria and a promising candidate to overcome the hurdles encountered by conventional methods care of food poisoning.

碩士<br>國立中興大學<br>環境工程學系所<br>105<br>Continuous accumulation of consumed human and veterinary antibiotics in the recipient environment has drawn increasing attention. A great percentage of the excreted antibiotics remains intact forms and enters the natural aquatic systems via the effluent and sludge from wastewater treatment plants, hospitals, and livestock farms. These released antibiotics may lead to bacterial resistance proliferation, contamination or adverse impacts on non-target organisms and microbial ecosystems. Therefore, it is essential to develop sensitive on-site detection techniques for monitoring these antibiotics in the environment. However, delicate instrumentation and complex sample pretreatment requirement of conventional analytical techniques such as spectrophotometry, electrophoresis, and chromatography have hindered their practical applications of real time and in situ sensing task. On the other hand, electrochemical techniques has been served as a sensitive method for on-site monitoring with low cost, high efficiency, and minimum sample pretreatment necessity. In the present study, an electrochemical sensor for rapid determination of sulfamethoxazole (SMZ), one of the most widely used antibiotics, has been developed. Reduced graphene oxide was used to modify the electrodes owing to its high charge mobility, low background noise, and high surface area. The response was optimized in terms of pH, scan mode, and applied potential. Under the optimized experimental conditions, the detection linear range is 0.5 μM-50 μM, the detection limit is 0.04 μM. Recovery in environmental media ranges from 101.9 to 108.4%. Further, addition of cetyltrimethylammonium bromide (CTAB) enhanced the electrochemical response of sulfamethoxazole detection. In the presence of trimethoprim (TMP), a common coexisting antibiotics with sulfamethoxazole, stable responses of SMZ detection makes simultaneous SMZ and TMP determination possible. Collectively, the modified electrodes exhibit great selectivity, sensitivity, and stability, and thus renders it a promising sensor toward detecting sulfamethoxazole in the aquatic system.

碩士<br>國立成功大學<br>化學工程學系<br>104<br>Firstly, three-dimensional (3D) reduced graphene oxide-carbon nanotube (rGO-CNT) nanocomposite was fabricated via the electrochemical reduction of graphene oxide-carbon nanotube (GO-CNT) on the screen printed carbon electrode (SPCE) to yield the rGO-CNT/SPCE for the electrochemical detection of phoxim. The presence of carbon nanotubes (CNTs) could lead to the formation of 3D structure, making the surface area of rGO can be utilized more efficiently to improve the sensitivity. It was demonstrated that CNTs were uniformly dispersed on GO, and GO has been electrochemically reduced to rGO. The electrochemical detection of phoxim on rGO-CNT/SPCE was performed in 0.1 M phosphate buffer at pH 7.0 by differential pulse voltammetry. A linear concentration range of 0.005~5 μM with a limit of detection (LOD) of 0.002 μM was obtained. For the detection of real samples and interference test, rGO-CNT/SPCE also exhibited an excellent performance. This revealed that it indeed could be used for the electrochemical detection and environmental monitoring of organophosphate pesticides. Secondly, β-cyclodextrin-modified graphene quantum dots (βCD-GQD) of about 9 nm were synthesized by the direct heating of citric acid and βCD at 200oC for the fluorescent detection of p-nitrophenol. The modification with βCD could significantly enhance the fluorescence intensity of GQD. Furthermore, for the fluorescent detection of by βCD-GQD, two linear concentration ranges of 0.1~7.5 μM and 7.5~100 μM with a LOD of 0.093 μM were obtained. The performance was significantly better than the un-modified GQD, revealing the resulting βCD-GQD indeed could be utilized in the fluorescent detection of toxic organic contaminants.

碩士<br>國立清華大學<br>化學系<br>101<br>Conventional analytical techniques employed for bacteria detection are time consuming (several hours to days). There is an increasing need for the development of rapid and sensitive methods for bacterial detection in clinical diagnosis. In this work, efforts were taken to synthesize graphene based biosensor vancomycin-magnetic graphene oxide (MGOVan) with silica nanoparticles (SiNPs) as biosensors for rapid detection of bacteria. Vancomycin has the capacity of capturing bacteria from aqueous solution. SiNPs were prepared by the Stöber method and then calcining which led to fluorescent. Using fluorescence resonance energy transfer (FRET) from SiNPs to MGOVan, the change in fluorescent intensity offered a novel method for bacteria detection. The lowest detectable bacteria concentration for both S. aureus and E. coli in aqueous solution was about 20 cfu/mL. Further, with unique magnetic feature, MGOVan-bacteria conjugates were aggregated under the external magnet quickly and subjected to matrix assisted laser desorption ionization-time of flight mass spectrometer (MALDI-TOFMS) to distinguish bacteria species. The detectable bacteria concentration for both S. aureus and E. coli by MALDI-TOFMS was about 108 cfu/mL. We also prepared vancomycin and sinapinic acid-magnetic graphene oxide (MGOVanSA). MGOVanSA can enhance bacteria desorption and ionization efficiencies by larger SA ratio in MALDI sample and sample’s sandwich composition. The change in fluorescent intensity and mass spectrometry results demonstrated that MGOVan is an ideal candidate for rapid detection of food and waterborn pathogens.

碩士<br>國立臺灣科技大學<br>材料科學與工程系<br>107<br>The nanohybrids of surface-enhanced Raman scattering (SERS) detection papers were successfully fabricated by gold nanoparticles (AuNPs) immobilized on the graphene oxide (GO) nanosheets-cellulose nanofibers (TOCNs) substrates. TOCNs were extracted from the recycling cellulose fibers from the food wastes, and then modified by a 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) to exfoliate it. GO and TOCNs were further blended together to fabricate papers by the paper machine. Furthermore, AuNPs were (ca. 10 nm) in-situ grown on the GO@TOCNs paper as SERS substrate for biomolecules and water pollutants detection. [2] The result show that the tensile strength of AuNPs@GO@TOCNs composites is 7-8 times higher than the pristine TOCNs papers, showing the great mechanical properties after the addition of GO and AuNPs. X-ray diffraction patterns show that TOCNs still maintain great crystallinity, even though diameters of cellulose fibers decrease from micro- to nano-scale. The biomolecules of rhodamine 6G and direct blue can be detected by Raman spectroscopy and chromatographic separation. The limit of detection (LOD) on AuNPs@GO@TOCNs SERS paper is lower than 10-7 M. The reason is that GO can doubly enhance the SERS intensity by the surface plasmon resonance in the symmetrical benzene structure. Finally, the nanohybrids paper can be used as a chromatographic paper to separate the samples by modulated the ratios of GO and TOCNs. Thus, AuNPs@GO@TOCNs papers are potential to apply in the platform of the chromatographic separation and rapid SERS detection of biomolecules.

碩士<br>中原大學<br>機械工程研究所<br>106<br>In this study, a paper-based chip with modified graphene oxide was proposed and a self-made electrochemical cyclic voltammetric scanning circuit was used to detect nitrite. Self-made circuit verification results are comparable to commercial electrochemical instruments. Experiments based on disposable paper-based screen printing electrodes. A layer of modified Hummers graphene oxide was coated on the working electrode. Then, 5-amino-1,3,4-thiadiazole-2-thiol (ATT) was electropolymerized on graphene oxide by cyclic voltammetry. Measurement using the self-made cyclic scan voltampere circuit. Results have a good linear distribution in concentrations of 0 mM to 4 mM and 4 mM to 8 mM. Graphene oxide provides a large surface area and numerous anchor sites for ATT adsorption. This chip has good specificity for nitrite.

碩士<br>國立臺北科技大學<br>機械工程系機電整合碩士班<br>107<br>Cancer,also known as malignancy, refers to abnormal cell proliferation. Millions of people die of cancer every year, so early diagnosis of cancer is important. The carcinoembryonic antigen (CEA) detected in this study is a tumor marker for colorectal, gastric, pancreatic and lung cancer. The most common test for colorectal cancer is that the normal level of CEA in human blood should be less than 5 ng/mL. If the result is higher than this concentration, it may be due to the problem of malignant tumors. In addition, CEA detection also helps patients with postoperative follow-up and observation of chemotherapy effects. The current method for detecting CEA mainly adopts Enzyme-linked immunosorbent assay (ELISA); the detection method is a highly specific binding reaction between antigen and antibody, which can be used to quantify the concentration of antigen or antibody, and is currently the most commonly used diagnosis technique. However, the shortcomings of current immunoassays are that the results are not easy to interpret, and the operation is complicated and time-consuming. Therefore, this study will use electrochemical impedance analysis, which has the advantages include being as relatively more convenient inspection process, no need for professional personnel to operate and portable small equipment to carry with. In recent years, with the miniaturization of medical diagnostic equipment and the improvement of communicative technology, the point of care (POC) has become a new trend in the future diagnosis, and electrochemical detection is quite in line with the future application of POC. In this study, Whatman's qualitative filter paper was used as the substrate of the working electrode to replace the conventional metal and glass carbon electrode. The paper-based electrode has a softer structure, easy process modification and lower cost. Graphene (Graphene) and conductive polymer (PEDOT) are modified on the surface of the paper-based electrode to form a composite electrode, thereby improving conductivity and increasing sensitivity. In the bio-binding part, we used the specific immunoreactivity of the antibody and the antigen and the specific affinity reaction of the aptamer. The concentrations of 0.76 ng / ml ~ 84.4 ng / ml and 0.76 ng / ml ~ 21.5 ng / ml CEA were successfully determined by the two methods, and the standard concentration range of CEA is within the measurement concentration range, the paper-based electrochemical impedance analysis method of this study has excellent potential and has the ability of quantitative analysis.

碩士<br>國立中興大學<br>生醫工程研究所<br>104<br>Since graphene was successfully isolated in 2004, it has received much attention and proceed with many research application owing to its high charge mobility, low background noise, high surface area, and biocompatibility property. In this study, the patterned-circuit silicon chips was first modified with by (3-aminopropyl) trimethoxysilane (APTMS), forming self-assembled monolayer which containing with amine groups. Then, the inherited oxygenated functional groups on solution-based graphene oxide (GO) were activated by 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-Hydroxysuccinimide (EDC/NHS) and further covalently conjugated with amine-functionalized silicon chips through amide bonds (-CONH-). After that, chemical reduction using hydrazine was implemented to remove a variety of oxygenated groups from immobilized GO surface gaining reduced GO (RGO). Electron spectroscopy for chemical analysis (ESCA), contact angle, Raman spectroscopy, biocompatibility test and I-V curve measurement were used to characterize the chemical components, hydrophilic/hydrophobic properties, lattice structure, biological toxicity and electrical characteristics of different reduced time of RGO. Analysis of results indicated 60-min RGO featured of optimal material properties which was suitable for the base material of the biosensors. Further, using 60-min RGO-based biosensor in the detection of the concentration gradient of dopamine. Making use of phosphate buffered saline to prepare dopamine solution, simulating physiological environment in human body. The medium frequency range of electrical impedance were measured by using LCR meter (E4980A, Agilent Technologies). Since the dopamine concentration in our cerebrospinal is around 1.89~16.65 nM, our 60-min RGO-based biosensor could discriminate 1 fM~100 nM which proved that 60-min RGO biosensor could be as the effective sensing dopamine platform. Furthermore, through the change in the impedance value could observe proliferation condition of rat adrenal pheochromocytoma (PC12) cells, proved 60-min RGO biosensor also could be non-invasive monitoring of living cells platform. By adding nerve growth factor (NGF) to stimulate PC12 cells differentiation, along with synapses growth and exhibited neuron characteristics. With 100μM KCl stimulation, neurotransmitters would be released from synaptic vesicle in differentiated PC12 cells. Through 60-min RGO biosensor could measure the impedance change which resulted from attachment of differentiated PC12 cells or emancipation of dopamine. In this research, through LCR meter imposing a sinusoidal AC voltage to trigger disturbances of frequency, avoiding hydrazine-reduced 60-min RGO biosensor to be interfered by Debye length. According to impedance response of dopamine and cell physiology, 60-min RGO biosensor could be used to detect early symptoms of imbalance dopamine concentration which related to Parkinson''s disease or schizophrenia, showing promising application in detection and tracking of the lesion.

碩士<br>國立交通大學<br>環境工程系所<br>107<br>In recent years, the groundwater pollution was more and more serious. Actually, the Fe(III) and As(V) was the common heavy metal ions in ground water. Simple, inexpensive and rapid sensing systems are highly essential for a myriad of uses. Intrinsic properties of emerging paper-based analytical devices have been demonstrated to have a considerable potential to fulfill such demand. This work reports an easy-to-use, low cost, and disposable paper-based sensor in which the functionalized graphene quantum dots (GQDs) embedded cellulose matrix acts as a fluorescence probe for selective and sensitive determination of Fe(III) and As(V). After functionalization, the 3,4-dihydroxyaniline (DHA-GQDs) and poly dimethyl diallyl ammonium chloride (PDADMAC-GQDs) were used for detecting Fe(III) and As(V), respectively. The cellulose of fluorescent paper was extracted from rice straw through TEMPO oxidation. The fluorescent paper was applied to detect Fe(III) and As(V) in ground water successfully. It opens a new avenue for simple and fast screening of HMIs and offers numerous possibilities for versatile applications.

碩士<br>國立臺灣大學<br>化學研究所<br>105<br>Alzheimer’s disease (AD) is the most common neurodegenerative disease and is characterized by neurofibrillary tangles and amyloid plaques. As the main component of the amyloid plagues, amyloid beta (Aβ), a peptide consisting of 40-42 amino acids, are crucially involved in Alzheimer’s disease. However, the knowledge around the disease pathogenesis is poorly understood and there is no effective cure for AD. Hence, a great deal of attention has focused on the study of Aβ. This research uses a lipid-modified graphene-based field-effect transistor (G-FET) as a biosensor to study the aggregation of Aβ on the supported lipid bilayer. Graphene has shown a great potential for research and applications because of its high chemical stability, high carrier mobility, high thermal conduction, high conductivity, flexibility, and high transmittance. Due to its two-dimensional (2D) nature, graphene possesses a large and stable interface with lipid membranes. We fabricated G-FET on a transparent quartz substrate, then modified a supported lipid bilayer containing GM1 on the G-FET by the vesicle fusion method. The as-fabricated G-FET biosensor is able to detect the aggregation of Aβ on the GM1 containing SLB. This aggregation is also verified by using Thioflavin T as a fluorescence indicator. With the capability of sensitively detecting the Aβ aggregation, this lipid-modified G-FET can be employed as a highly sensitive biosensing platform for further investigation of the mechanism of Aβ aggregation.

Submitted in fulfillment of the requirements of the Degree in Chemistry, Durban University of Technology, 2017.<br>High prevalence and mortality cases of prostate cancer (PCa) have increased around the world, particularly in developing countries. Several forthcoming factors have been revealed nowadays, one of them is due to the incapability of the diagnostic methods to produce reliable results, which impacts negatively on cancer-treatment. However, a sensitive diagnosis of PCa cells remains a challenge in the field of biosensors. Emerging whole-cell detection as biosensing targets has opened up avenues for successful cancer diagnostics, due to high selectivity among other cells. A switchable and flexible surface-based graphene material is one of the techniques that revolutionized smart biodevice platforms in biosensor technology. In this present study, a covalently linked poly-(N-isopropylacrylamide) (PNIPAM) to graphene oxide surface has been employed as “on/off”-switchable aptamer-based sensor for the detection of PC3 whole-cancer cell. The constructed surface has benefitted from PNIPAM, as the thermal-stimulus agent, which allows the coil-to-globule transitions by triggering temperature changes. When the system is above its lower critical solution temperature (LCST) of 32oC, PNIPAM will exist as hydrophobic -globular state providing an “on” binding region for the whole-cell, reaching the interactions on the biosurface. The “off” binding systems is only possibly when the PNIPAM turns into extended-state by lowering its temperature below LCST. The first principle studies have successfully characterized the electronic behavior with particular emphasis of PNIPAM monomer functions along with the description of the structural energetics of complex through density functional theory (DFT). Docking studies have further been performed to predict a plausible binding aptamer toward the protein-representative PCa cell. To better understand the prospect of an aptamer-based tunable biosensor, molecular dynamics (MD) highlighted the behavior of PNIPAM-grafted GO in exhibiting a globular and extended conformations at above and below LCST, permitting the biomolecules to interact with each other as well as to avoid interactions, respectively. Experimental studies have been included to validate the theoretical predictions by fabricating real-biosensor systems using electrochemical impedance technique, resulting a low-detection limit down to 14 cells/mL. Engagement between theoretical and experimental studies delivered an enhanced tunable-biosensor performance for the detection of whole cell prostate cancer.<br>M

碩士<br>國立臺灣大學<br>應用物理研究所<br>105<br>A highly sensitive glucose biosensor based on graphene/ZnO/p-Si heterojunctions is demonstrated. Its sensing mechanism makes use of the large variation in the Fermi energy of graphene upon direct electron transfer of glucose oxidase at the presence of glucose molecules, with a film of ZnO acting as a sieve layer to block the carriers from transferring into the underlying semiconductor layer, resulting in a superb detection sensitivity. Through measurements of the current-voltage characteristics and time dependence of the changed current, this unique structure responds to glucose concentrations from as low as 0.1 pM to 100 μM range, which outperforms the best value ever reported by more than three orders of magnitude. Furthermore, we demonstrate the self-powered capability of this newly designed biosensor at room light illumination level, without compromising its sensitivity and dynamic range of detection. Altogether, this device presents with an excellent performance that surpasses all current glucose detection devices used in medical control, representing a novel possibility for easy and painless monitoring of blood glucose for patients with diabetes mellitus.

碩士<br>國立中興大學<br>化學工程學系所<br>106<br>In this study, we designed a simple and sensitive sandwich-type electrochemiluminescence (ECL) immunosensor based on GQDs labelled secondary antibody (GQDs-Ab2) as a bioprobe to detect the concentration of the tumor marker carcinoembryonic antigen (CEA) on a GQD-Au NPs modified glassy carbon electrode (GQD-Au NPs/GCE). GQDs with excellent light stability and high specific surface area provided an efficient biointerface to control the loading amount of Ab2. First, the primary antibody, anti-CEA (Ab1) was immobilized on the GQD-AuNPs modified electrode by covalent binding, then the antigen and GQDs-Ab2 were successfully immobilized by specific interactions to form a sandwich-type immunocomplex. The principle of ECL detection was that the ECL intensity will be increase by the ECL reaction between GQDs and K2S2O8 after binding GQDs-Ab2 to CEA. The prepared ECL immunosensor showed high sensitivity and wide liner for detection CEA in the range of 0.005 - 50 ng/mL and the limit detection was 2 pg/mL.

碩士<br>國立成功大學<br>工程科學系<br>107<br>Heavy metals emitted into the environment through human activities, causes environmental pollution and threats to living things. Once the heavy metal is released, whether it is eroded into the sea or accumulated in the aquifer, it may interact with the organic matter between the organism, Therefore, many human diseases for example cardiovascular, blood, lung, digestive system, kidney system, immune system, nervous system, endocrine system, reproductive system and fetus may be due to suffering from the toxic heavy metals in our environment. In this study, we design a microfluidic device to detect the concentration of Hg2+ in liquids. The microchannel is fabricated by using Polydimethylsiloxane, which can accelerate the reaction and enhance the mixing efficiency. We use Aptamer together with graphene oxide mixed inside the microchannels, when in the presence of Hg2+, thymine selectively combined with Hg2+ to form T–Hg2+–T complex. This could get rid of the adsorption of Aptamer by graphene oxide, and thus can recovered the fluorescence. This study indicates the detection range is from 2 nM to 100 nM in microchannel (R2=0.98114), and according to the International World Health Organization (WHO), the maximum allowable mercury ion is 6 ppb in drinking water, and the minimum detection of limit (LOD) is 2 nM, which is equivalent to 0.39 ppb. From the result, the detection of limit is obvious lower than the regulations.

碩士<br>國立臺灣大學<br>化學研究所<br>106<br>Dopamine is an important neurotransmitter, which is responsible for the transmission of nerve cells and is also associated with many diseases of nervous system. However, the existing electrochemical sensors are not sensitive enough to detect the trace amount of dopamine in human blood or urine. Hence, an ultra-sensitive biosensor to detect dopamine-related neurologic diseases at an early stage is needed. Field-effect transistors have been studied with its sensitive biosensing applications over a decade. Besides, graphene has represented great potential in scientific research with its high carrier mobility, high chemical stability, high thermal conductivity, high conductivity, flexibility, high mechanical strength, and high light transmittance. Therefore, in this study, we fabricated graphene-based field-effect transistors (G-FETs) with single-layered graphene on the quartz substrate and modified DNA-aptamer on the G-FET surface to detect low concentrations of dopamine. One major challenge of FET-based biosensors is to detect analyte in a high salt buffer. In term of Debye-Hückel screening effect, the electric-field of analyte is attenuated by ions and results in reduced signals. To overcome this problem, we modified polyethylene glycol (PEG) on the surface of a G-FET to decrease Debye-Hückel screening. With the capability of detecting 1 nM dopamine in 3× PBS solution, we proved that G-FETs can be employed as a highly sensitive biosensing platform for dopamine detection.

碩士<br>國立臺灣師範大學<br>光電科技研究所<br>105<br>In this work we present a facile processes amine modified graphene oxide (GO-NH2) as an ultra-sensitive surface plasmon resonance (SPR) probe grafting layer for non-immunization sensing. The GO-NH2 based SPR biosensor was applied in detection of human Chorionic Gonadotropin (hCG), relevant to pregnant disease. Such as premature birth, ectopic pregnancy, and Down's syndrome. It’s also relevant to some cancer about gonad, like ovarian cancer, breast cancer, or testicular cancer. The concentration of hCG in blood plasma of healthy and non-pregnant is around 0.45 nM. Replacing antibody by non-immunization peptide got an opportunity of preserve the probe in relative higher temperature and much lower cost than antibodies. In order to diagnose the patient in the early state and benefit for commercial situation, the characteristic of high resolution GO-NH2 modified bio-chip is a novel and advantage technique. The first part of two-step modified approach is substitute the hydroxyl with chloride on GO. The chloride functional graphene oxide (GO-Cl) is obtained through the reaction of GO and thionyl chloride (SOCl2). After that, we utilize ammonia water as nitrogen precursor, and the chloride groups are replaced by amino groups. The primary of facial amine group is identified by X-ray photoelectron spectroscopy (XPS). The ratio of nitrogen and carbon in our experimental parameter is increase to 5.7%, and the ratio of oxygen is changed from 27% to 17%. In the Fourier transform infrared spectroscopy (FTIR) experiment. The absorbed peak of 1064 〖cm〗^(-1), 1579 〖cm〗^(-1), and 3361 〖cm〗^(-1) that absorbed by N are found. The simulation of complex refractive index and the impedance of GO-NH2 is 1.55 + C_1 λ/n i and 89.16 Ω. The recombinant protein experiment shows that GO-NH2 sensor-chip is 2.45 times about the affinity of peptide. Comparing in non-immunization diagnostic, the response at 2 nM is 2.68 times greater, and the slope of GO-NH2 linear regression is 1.5 times higher than commercial chip. Last, the clinical blood serum experiment shows high linear regression coefficients.

abstract: Obtaining local electrochemical (EC) information is extremely important for understanding basic surface reactions, and for many applications. Scanning electrochemical microscopy (SECM) can obtain local EC information by scanning a microelectrode across the surface. Although powerful, SECM is slow, the scanning microelectrode may perturb reaction and the measured signal decreases with the size of microelectrode. This thesis demonstrates a new imaging technique based on a principle that is completely different from the conventional EC detection technologies. The technique, referred to as plasmonic-based electrochemical imaging (PECI), images local EC current (both faradaic and non-faradaic) without using a scanning microelectrode. Because PECI response is an optical signal originated from surface plasmon resonance (SPR), PECI is fast and non-invasive and its signal is proportional to incident light intensity, thus does not decrease with the area of interest. A complete theory is developed in this thesis work to describe the relationship between EC current and PECI signal. EC current imaging at various fixed potentials and local cyclic voltammetry methods are developed and demonstrated with real samples. Fast imaging rate (up to 100,000 frames per second) with 0.2×3µm spatial resolution and 0.3 pA detection limit have been achieved. Several PECI applications have been developed to demonstrate the unique strengths of the new imaging technology. For example, trace particles in fingerprint is detected by PECI, a capability that cannot be achieved with the conventional EC technologies. Another example is PECI imaging of EC reaction and interfacial impedance of graphene of different thicknesses. In addition, local square wave voltammetry capability is demonstrated and applied to study local catalytic current of platinum nanoparticle microarray. This thesis also describes a related but different research project that develops a new method to measure surface charge densities of SPR sensor chips, and micro- and nano-particles. A third project of this thesis is to develop a method to expand the conventional SPR detection and imaging technology by including a waveguide mode. This innovation creates a sensitive detection of bulk index of refraction, which overcomes the limitation that the conventional SPR can probe only changes near the sensor surface within ~200 nm.<br>Dissertation/Thesis<br>Video for Figure 3.2 C to H<br>Video for Figure 3.5<br>Video for Figure 5.5<br>Video for Figure 6.7<br>Video for Figure 6.11<br>Ph.D. Electrical Engineering 2011