To see the other types of publications on this topic, follow the link: Au nanoshells.
Dissertations / Theses on the topic 'Au nanoshells'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Au nanoshells.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Comi, Troy J. "Porous Phospholipid Nanoshells as Enzymes Delivery Agents." Thesis, The University of Arizona, 2012. http://hdl.handle.net/10150/243914.
Full textAbstract:
Diabetes is an epidemic in developed nations. Glucokinase (GK) is vital for glocose sensing, and is directly implicated in particular forms of diabetes. Studying pancreatic cells with altered GK activity would facilitate studies, but current methods for altering proteomes are lacking. Porous phospholipid nanoshells (PPNs) have traditionally been used as platforms for biologically derived nanosensors, though their biocompatibility and protease resistance well suits them as enzyme delivery agents. GK kinetics were investigated with an enzyme coupled reaction to determine the effect of encapsulation. It was determined that encapsulation increased the Hill coefficient by 5.8% and the S(0.5) by 1.8%. This small deviation may not be significant in physiological conditions. To observe a recovered function in cell lines upon reintroducing GK, constitutively expressed GK must first be knocked down with siRNA. As initial work toward an siRNA knockdown, immunoblotting conditions were optimized resulting in a detection limit below 10 ng of GK. Immunoblotting verified suspected constitutive expression of GK in INS-1 cell lines. While further investigation is necessary to demonstrate the utility of GK-containing PPNs for cell delivery, this thesis outlines the generation and characterization of this novel enzyme delivery platform.
2
San, San Maw. "Synthesis of Silver Nanoshells with Controlled Thickness and Morphology." Doctoral thesis, Kyoto University, 2020. http://hdl.handle.net/2433/245847.
Full textAbstract:
京都大学<br>0048<br>新制・課程博士<br>博士(工学)<br>甲第22162号<br>工博第4666号<br>新制||工||1728(附属図書館)<br>京都大学大学院工学研究科化学工学専攻<br>(主査)教授 宮原 稔, 教授 山本 量一, 教授 松坂 修二<br>学位規則第4条第1項該当<br>Doctor of Philosophy (Engineering)<br>Kyoto University<br>DGAM
3
Zeng, Jianbo. "Gold Nanoshells: Synthesis and Applications to In Situ SERS." Miami University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=miami1362843561.
Full text
4
Van, Nostrand Joseph E. "Detection and Destruction of Escherichia Coli Bacteria and Bacteriophage Using Biofunctionalized Nanoshells." Wright State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=wright1190897606.
Full text
5
Ng, Vanessa. "Gold nanoshells: designing a multifunctional molecular probe for photoacoustic imaging." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114594.
Full textAbstract:
Atherosclerosis is a cardiovascular disease that is known to be the primary cause of heart attacks and strokes. The hard plaque that forms within the arteries can be vulnerable to rupture, causing thrombosis which can effectively obstruct the flow of blood. The identification of vulnerable plaque is directly related to the composition of the plaque itself. Current imaging methodologies do not sufficiently address the issues of identifying early stages of atherosclerosis, plaque composition and thus, lesion vulnerability. Photoacoustic imaging techniques used in conjunction with contrast enhancing nanomaterials have offered a novel approach to address these problems. This thesis presents a platform by which synthesis of a strategically designed nanoprobe combining multiple functionalities can help address these issues. The chosen nanomaterial, in particular gold nanoshells, are optically and biologically relevant substrates that can be tuned to absorb within the biological window (650-900 nm) where biological absorption interference is the lowest. The synthesis of gold nanoshells using a sacrificial cobalt nanoparticle template procedure was optimized to obtain nanoshells of approximately 40 nm in diameter and 3 nm in thickness with plasmon absorption between 650-750 nm. To further enhance the utility of gold nanoshells, additional functionalities were incorporated onto them by exploiting the well known thiol-gold bond formation. The simplicity and adaptability of the synthetic process allows for coupling to any desired functionality or functionalities into these systems. Using this methodology, two monofunctional ligands and one multifunctional ligand, possessing therapeutic (lipoic acid), additional imaging (fluorescent dyes), solubilizing (PEG) functionalities and combinations thereof, were successfully synthesized. Each of these ligands were subsequently conjugated to the gold nanoshells, creating probes that possess the optical properties of the gold nanoshells in combination with the additional ligand properties. With in vitro and in vivo studies underway, the work in this thesis covering the optimization and fabrication of these novel multivalent probes has laid a solid foundation to achieve the goal of vulnerable plaque identification.<br>L'athérosclérose est connue pour être la cause primaire des crises cardiaques et des accidents cérébraux-vasculaires. Les plaques qui se forment sur les parois des artères sont susceptibles d'éclatées causant par la suite une thrombose qui peut obstruer l'influx sanguin. L'identification de plaques vulnérables est directement liée à la composition de ces plaques. Les méthodologies actuelles d'imagerie ne sont pas assez compétentes pour identifier les stades préliminaires d'athérosclérose, la composition des plaques et, conséquemment, la susceptibilité de ceux-ci de subir des lésions. Les techniques d'imagerie photoacoustique utilisées conjointement avec des nanomatériaux agissant comme agent de contraste offrent une stratégie inédite pour résoudre ces obstacles. Cette thèse présente un projet par laquelle la synthèse stratégique d'une nano-sonde incorporant plusieurs fonctionnalités peu adresser ces problèmes. Des nano-coquilles d'or, le nanomatériau choisi, sont des substrats pertinents du point de vue de l'optique et de la biologie qui peuvent être ajustés de sorte qu'elles absorbent dans la fenêtre biologique (650-900 nm), c'est-à-dire là où l'interférence dû à l'absorption biologique est à son plus bas. La procédure de synthèse des nano-coquilles d'or utilisant un modèle sacrificiel de nanoparticules de cobalt a été optimisée pour obtenir des nano-coquilles d'approximativement 40 nm de diamètre et 3 nm d'épaisseur, avec une absorption plasmonique entre 650 et 750 nm. Pour augmenter davantage l'utilité des nano-coquilles d'or, des fonctionnalités additionnelles ont été incorporées grâce à la formation du lien thiol-or. La simplicité et l'adaptabilité du processus synthétique permet le couplage de toutes fonctionnalités désirées. Utilisant cette méthodologie, deux ligands monofonctionnels et un ligand multifonctionnel, possédant des fonctionnalités thérapeutique (acide lipoïque), d'imagerie additionnel (fluorochrome), ainsi que de solubilisation (PEG), ont été synthétisés avec succès. Chacun de ces ligands ont été par la suite conjugués aux nano-coquilles d'or, créant ainsi des sondes possédant les propriétés optiques des nano-coquilles d'or en plus des propriétés des ligands. Présentement, des études in vitro et in vivo se déroulent; le travail présenté dans cette thèse couvrant l'optimisation et la fabrication de ces sondes multivalentes inédites a établi une base solide pour atteindre l'objectif de l'identification des plaques vulnérables.
6
Puvanakrishnan, Priyaveena. "Near-infrared narrow-band imaging of gold/silica nanoshells in tumors." Thesis, [Austin, Tex. : University of Texas, 2009. http://hdl.handle.net/2152/ETD-UT-2009-05-43.
Full text
7
Harankahage, Dulanjan Padmajith Dharmasena. "Quantum Confinement Beyond the Exciton Bhor Radius in Quantum Dot Nanoshells." Bowling Green State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1593955468720583.
Full text
8
Garcia, Soto Mariano de Jesús. "Synthesis of Gold Nanostructures with Optical Properties within the Near-Infrared Window for Biomedical Applications." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/321533.
Full textAbstract:
The work reported in this dissertation describes the design and synthesis of different gold nanoshells with strong absorption coefficients at the near-infrared region (NIR) of the spectrum, and includes preliminary studies of their use for the photo-induced heating of pancreatic cancer cells and ex vivo tissues. As the emphasis was on gold nanoshells with maximum extinctions located at 800 nm, the methods explored for their synthesis led us to the preparation of silica-core and hollow gold nanoshells of improved stability, with maximum extinctions at or beyond the targeted within the near-infrared window. The synthesis of silica-core gold nanoshells was investigated first given its relevance as one of the pioneering methods to produce gold nanostructures with strong absorption and scattering coefficients in the visible and the near-infrared regions of the spectrum. By using a classical method of synthesis, we explored the aging of the precursor materials and the effect of using higher concentrations than the customary for the reduction of gold during the shell growth. We found that the aging for one week of the as-prepared or purified precursors, namely, the gold cluster suspensions, and the seeded silica particles, along with higher concentrations of gold in the plating solution, produced fully coated nanoshells of 120 nm in size with smooth surfaces and maximum extinctions around 800 nm. Additional work carried out to reduce the time and steps in the synthesis of silica-core gold nanoshells, led us to improve the seeding step by increasing the ionic strength of the cluster suspension, and also to explore the growth of gold on tin-seeded silica nanoparticles. The synthesis of hollow gold nanoshells (HGS) of with maximum extinctions at the NIR via the galvanic replacement of silver nanoparticles for gold in solution was explored next. A first method explored led us to obtain HGS with maximum extinctions between 650 and 800 nm and sizes between 30 and 80 nm from silver nanoparticles, which were grown by the addition of silver nitrate and a mild reducer. We developed a second method that led us to obtain HGS with maximum extinctions between 750 and 950 nm by adjusting the pH of the precursor solution of the silver particles without much effort or additional steps. The last part of this work consisted in demonstrating the photo-induced heating of two biological systems containing HGS. Photothermal therapy studies of immobilized PANC1 pancreas cancer cells in well-plates were carried out with functionalized HGS. We found that cells exposed to HGS remained viable after incubation. Moreover, the cells incubated with HGS modified with mercaptoundecanoic acid and folic acid turned non-viable after being irradiated with a laser at 800 nm. The other study consisted in the laser-induced heating between 750 and 1000 nm of ex vivo tissues of chicken and pork with nanoshells injected. In comparison with non-injected tissues, it was found that the temperature at the irradiated areas with HGS increased more than 10 °C. Moreover, the extent of the heated area was broader when the laser was used at wavelengths beyond 900 nm, suggesting that the heating was due to the radiation absorbed and transformed into heat primarily by the HGS and at a lesser extent by the water in the tissue.
9
Peterson, Alisha D. "Synthesis and Characterization of Novel Nanomaterials: Gold Nanoshells with Organic- Inorganic Hybrid Cores." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3612.
Full textAbstract:
Gold nanoshells, a material generally composed of a core of silica surrounded by
a thin shell of gold, are of great interest due to their unique and tunable optical properties.
By varying the shell thickness and core size, the absorption and scattering properties are
greatly enhanced. The nanoshells can be made to absorb or scatter light at various
regions across the electromagnetic spectrum, from visible to the near infrared. The
ability to tune the optical properties of nanoshells allows for their potential use in many
different areas of research such as optical imaging, tumor ablation, drug delivery, and
solar energy conversion. The research in this thesis focused on the synthesis and
characterization of two novel gold nanoshell materials containing thermally-responsive,
organic-inorganic hybrid layers. One type of material was based on a two-layer particle
with a thermally responsive hybrid core of N-isopropylacrylamide (NIPAM)
copolymerized with 3-(trimethoxysilyl)propyl methacrylate (MPS) that was then coated
with a thin layer of gold. The second material was a three-layer particle with a silica
core, a thermally responsive copolymer of NIPAM and MPS middle layer and an outer
shell of gold. Various techniques were used to characterize both materials. Transmission
electron microscopy (TEM) was used to image the particles and dynamic light scattering
(DLS) was used to determine particle size and the temperature response. Additionally,
UV-Vis spectroscopy was used to characterize the optical properties as a function of
temperature.
10
Kearns, Hayleigh. "Hollow gold nanoshells as unique near infrared optical materials for surface enhanced Raman scattering." Thesis, University of Strathclyde, 2016. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=26531.
Full textAbstract:
Hollow gold nanoshells (HGNs) demonstrate a tunable localised surface plasmon resonance (LSPR) from the visible to the near infrared (NIR). The NIR region of the electromagnetic spectrum is of particular interest as it provides an uncongested spectral window for optical analysis due to many molecules having reduced absorption and scattering backgrounds. In addition, the superior depth of light penetration and reduced interference which is observed in this region when compared to the visible region means that there is a great need to design SERS nanotags which can provide a unique vibrational fingerprint in this uncongested optical region. The research described herein demonstrates three ways in which red-shifted nanotags can be engineered to provide effective SERS signals in the NIR region. Firstly, NIR active HGNs were synthesised and encapsulated with seven non-resonant commercial Raman reporters and shown to provide effective SERS when excited with a 1064 nm laser. The nanotags were then tested using a 1280 nm laser excitation however; they were unsuccessful at providing a SERS spectrum. Through a successful collaboration with Professor Michael Detty's group (University at Buffalo) newly synthesised Raman reporters where obtained. The chalcogenopyrylium dyes were resonant from 650 to 1000 nm and when combined with HGNs, demonstrated an unprecedented performance. Through the design of these nanotags, extreme red-shifted SERS was achieved with laser excitations from 1064 nm up to 1550 nm and detection limits in the picomolar to femtomolar range where obtained. Finally, this research demonstrates that when hollow gold nanotags are functionalised with a thermopolymer such as poly(N-isopropylacrylamide), the LSPR can be shifted into the NIR region and laser induced plasmonic heating of the nanoshells can be used to turn on and off the SERS enhancement. Overall, the development of NIR active nanotags could provide the basis for future advancements in bio-chemical, medical and optical applications.
11
Chowdhury, Mustafa Habib. "The use of Surface Enhanced Raman Spectroscopy (SERS) for biomedical applications." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4816.
Full textAbstract:
Recent advances in nanotechnology and the biotechnology revolution have
created an immense opportunity for the use of noble metal nanoparticles as Surface
Enhanced Raman Spectroscopy (SERS) substrates for biological sensing and diagnostics.
This is because SERS enhances the intensity of the Raman scattered signal from an
analyte by orders of 106 or more. This dissertation deals with the different aspects
involved in the application of SERS for biosensing. It discusses initial studies performed
using traditional chemically reduced silver colloidal nanoparticles for the SERS
detection of a myriad of proteins and nucleic acids. It examines ways to circumvent the
inherent aggregation problems associated with colloidal nanoparticles that frequently
lead to poor data reproducibility. The different methods examined to create robust SERS
substrates include the creation of thermally evaporated silver island films on microscope
glass slides, using the technique of Nanosphere Lithography (NSL) to create
hexagonally close packed periodic particle arrays of silver nanoparticles on glass
substrates as well as the use of optically tunable gold nanoshell films on glass substrates. The three different types of SERS surfaces are characterized using UV-Vis absorption
spectroscopy, Electron Microscopy (EM), Atomic Force Microscopy (AFM) as well as
SERS using the model Raman active molecule trans-1,2-bis(4-pyridyl)ethylene (BPE).
Also discussed is ongoing work in the initial stages of the development of a SERS based
biosensor using gold nanoshell films for the direct detection of b-amyloid, the causative
agent for Alzheimer's disease. Lastly, the use of gold nanoshells as SERS substrates for
the intracellular detection of various biomolecules within mouse fibroblast cells in cell
culture is discussed. The dissertation puts into perspective how this study can represent
the first steps in the development of a robust gold nanoshell based SERS biosensor that
can improve the ability to monitor biological processes in real time, thus providing new
avenues for designing systems for the early diagnosis of diseases.
12
Mann, Daniel Verfasser], Martin [Akademischer Betreuer] [Möller, and Regina [Akademischer Betreuer] Palkovits. "Design, synthesis and characterization of Au and Ag nanoshells and Au semishells with tunable localized surface plasmon resonance / Daniel Mann ; Martin Möller, Regina Palkovits." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1181193184/34.
Full text
13
Mann, Daniel [Verfasser], Martin [Akademischer Betreuer] Möller, and Regina [Akademischer Betreuer] Palkovits. "Design, synthesis and characterization of Au and Ag nanoshells and Au semishells with tunable localized surface plasmon resonance / Daniel Mann ; Martin Möller, Regina Palkovits." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1181193184/34.
Full text
14
SILVA, Renato Barbosa da. "Materiais Micro e Nanoestruturados para Aplicações Fotônicas." Universidade Federal de Pernambuco, 2015. https://repositorio.ufpe.br/handle/123456789/17328.
Full textAbstract:
Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2016-07-11T19:05:22Z
No. of bitstreams: 2
license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5)
TESE Renato Barbosa da Silva.pdf: 6315157 bytes, checksum: 2b3ac093113d303d28b902d531315c52 (MD5)<br>Made available in DSpace on 2016-07-11T19:05:22Z (GMT). No. of bitstreams: 2
license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5)
TESE Renato Barbosa da Silva.pdf: 6315157 bytes, checksum: 2b3ac093113d303d28b902d531315c52 (MD5)
Previous issue date: 2015-08-27<br>CAPES<br>Diferentes tipos de materiais foram abordados nesta tese visando sua possível aplicação na
fotônica. Por isso, o texto foi dividido em duas partes. A Parte 1 trata da preparação de materiais
para a aplicação em laser aleatório. O primeiro material sintetizado foram as nanocascas
metálicas, cuja estrutura é formada por um caroço de sílica com uma casca metálica ao seu redor.
Assim, foi descrito um procedimento experimental melhorado com o intuito de se obter
nanocascas de ouro e de prata de maneira mais reprodutível no menor tempo possível. Neste
experimento, foi demostrado que a taxa de agitação no final da síntese tem importante influência
na formação ou não das nanocascas metálicas. O crescimento de nanocascas de ouro e prata
ocorria para taxas de 190 rpm e 1500 rpm respectivamente.
O segundo material consistiu de partículas sub-micrométricas de sílica com corante
rodamina 640 encapsulado. O encapsulamento ocorreu pela simples adição de uma solução do
corante durante a síntese das partículas de sílica. Assim, para uma concentração de corante de
10-2 M, foi descrito um experimento de laser aleatório bicromático. Ao contrário de outros
trabalhos na literatura foi possível controlar a emissão do laser aleatório apenas mudando a
intensidade de excitação. Durante estes experimentos também foi verificada a existência de
frequency-pulling entre dímeros e monômeros nos experimentos.
Finalmente na Parte 2 é discutida a síntese e caracterização de nanocristais de silício
(ncSi). Os ncSi apresentam luminescência cujo comprimento de onda pode ser controlado
variando o tamanho dos nanocristais. A síntese foi baseada no processamento termal em altas
temperaturas do hidrossilicato HSiO1.5, derivado do triclorossilano (HSiCl3). Em seguida, os
vidros são finamente macerados num almofariz e pistilo de ágata antes dos ncSi serem extraídos
via extração ácida. Neste experimento o objetivo foi obter nanocristais de silício monodispersos
sem a utilização de etapas pós-síntese como a ultracentrifugação. O objetivo foi alcançado
adicionando cloreto de sódio (NaCl) durante a etapa maceração, com o intuito de diminuir o
tamanho dos grãos e garantir uma extração uniforme dos mesmos<br>Different materials were reported in this thesis aiming their possible photonic applications.
Therefore the content of this thesis was distributed in two parts. Part 1 is related to the synthesis
of materials for applications in random laser. The first material synthesized were the metallic
nanoshells, which structure is based in a silica core and a metallic shell around it. An improved
experimental method was reported for synthesize gold and silver nanoshells in order to guarantee
the reproducibility and decrease the time necessary for synthesis. It was shown that the stirring
rate at the end of synthesis plays an important role on the growth of metallic nanoshells. The
growth of gold nanoshells was performed using a stirring rate of 190 rpm, on the other hand, the
growth of silver nanoshells was performed using a stirring rate of 1500 rpm.
The second material consisted of sub-micrometer silica particles whith encapsulated
rhodamine 640. The encapsulation was made by the simple addition of a dye solution to do
during a Synthesis of silica particles. An bichromatic random laser was operated using a
concentration of 10-2 M of laser dye. Unlike other works in the literature it was possible to
control the emission of the random laser only changing the intensity of the excitation source.
These experiments were also revealed the possibility of frequency-pulling between dimers and
monomers of rhodamine through the shift of the laser emission.
Finally, in Part 2 it is discussed the synthesis and characterization of silicon nanocrystals
(ncSi). The ncSi present luminescence that can be tunable by changing the ncSi sizes The
synthesis was based on the thermal processing at high temperatures of HSiO1.5 hydrosilicate
derivative of trichlorosilane (HSiCl3). Then, the glasses are finely grounded in a agate mortar and
pestle before been extracted via an acid etching. In this experiment the objective was to obtain
monodisperse nanocrystals of silicon without the use of post-synthesis steps such as
ultracentrifugation. The objective was reached added sodium chloride (NaCl) during the ground
step in order to decrease the size of grain for to obtain a uniform etching.
15
Peterson, Sarah M. 1975. "Influence of scale, geometry, and microstructure on the electrical properties of chemically deposited thin silver films." Thesis, University of Oregon, 2007. http://hdl.handle.net/1794/8453.
Full textAbstract:
xv, 101 p. ; ill. (some col.) A print copy of this title is available through the UO Libraries under the call number: KNIGHT QC176.84.E5 P47 2007<br>Silver films with nanoscale to mesoscale thicknesses were produced by chemical reduction onto silica substrates and their physical and electrical properties were investigated and characterized. The method of silver deposition was developed in the context of this research and uses a single step reaction to produce consistent silver films on both flat silica coverslips and silica nanospheres of 250-1000 nm. Both the structure and the electrical properties of the silver films are found to differ significantly from those produced by vacuum deposition. Chemically deposited (CD) silver is not uniformly smooth, but rather is granular and porous with a network-like structure. By quantitatively accounting for the differences in scale, geometry, and microstructure of the CD films, it is found that the same models used to describe the resistivity of vacuum deposited films may be applied to CD films. A critical point in the analysis that allows this relation involves the definition of a geometric parameter, g, which replaces the thickness, t, as the critical length that influences the electrical properties of the film. The temperature dependent properties of electrical transport were also investigated and related to the microstructure of the CD films. A detailed characterization of CD silver as shells on silica spheres is also presented including physical and optical properties. In spite of the rough and porous morphology of the shells, the plasmon resonance of the core-shell structure is determined by the overall spherical shell structure and is tunable through variations in the shell thickness. Preliminary investigations into the electrical transport properties of aggregates of silver coated spheres suggest similarities in the influence scale, geometry, and microstructure to silver films on flat substrates. The aggregates of shells also exhibit pressure related resistance behavior due to the composite structure.<br>Adviser: Miriam Deutsch
16
Peterson, Alisha. "Understanding the Role of Colloidal Particles in Electroporation Mediated Delivery." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5823.
Full textAbstract:
Electroporation (EP) is a physical non-viral technique used to deliver therapeutic molecules across the cell membrane. During electroporation an external electric field is applied across a cell membrane and it causes pores to form. These pores then allow the surrounding media containing the therapeutics to diffuse across the membrane. This technique has been specifically studied as a promising gene and drug delivery system. Colloidal particles have also proven to be promising for a variety of biological applications including molecular delivery, imaging, and tumor ablation, due to their large surface area and tunable properties. In more recent years researchers have explored the use of both electroporation and particles simultaneously. In this research, the main objective was to investigate and determine the role of sub-micron particles in the electroporation process. Presented in this dissertation are results from the synthesis and characterization of colloidal particles of various sizes and different compositions. The use of these dielectric and metallic particles during in vitro electroporation were investigated along with various other electrical parameters associated with EP such as pulse length, number of pulses, and field strength. Computationally, aspects such as particle composition and particle concentration were explored in an attempt to predict experimental outcomes.
17
Mendes, Rafael Gregorio. "Synthesis, characterization and toxicological evaluation of carbon-based nanostructures." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-186839.
Full textAbstract:
The synthesis, characterization and biological evaluation of different graphene-based nanoparticles with potential biomedical applications are explored. The results presented within this work show that eukaryotic cells can respond differently not only to different types of nanoparticles, but also identify slight differences in the morphology of nanoparticles, such as size. This highlights the great importance of the synthesis and thorough characterization of nanoparticles in the design of effective nanoparticle platforms for biological applications. In order to test the influence of morphology of graphene-based nanoparticles on the cell response, nanoparticles with different sizes were synthesized and tested on different cells. The synthesis of spherical iron-oxide nanoparticles coated with graphene was accomplished using a colloidal chemistry route. This synthesis route was able to render nanoparticle samples with narrow size distributions, which can be taken as monodispersed. Four different samples varying in diameter from 10 to 20 nm were produced and the material was systematically characterized prior to the biological tests. The characterization of the material suggests that the iron oxide nanoparticles consist of a mix of both magnetite and maghemite phases and are coated with a thin graphitic layer. All samples presented functional groups and were similar in all aspects except in diameter. The results suggest that cells can respond differently even to small differences in the size of the nanoparticles. An in situ study of the coating of the iron-oxide nanoparticles using a transmission electron microscope revealed that it is possible to further graphitize the remaining oleic acid on the nanoparticles. The thickness of the graphitic coating was controlled by varying the amount of oleic acid on the nanoparticles. The in situ observations using an electron beam were reproduced by annealing the nanoparticles in a dynamic vacuum. This procedure showed that it is not only possible to coat large amounts of iron oxide nanoparticles with graphene using oleic acid, but also to improved their magnetic properties for other applications such as hyperthermia. This study therefore revealed a facile route to grow 2D graphene takes on substrates using oleic acid as a precursor. The synthesis of nanographene oxide nanoparticles of different sizes was in a second approach accomplished by using the Hummers method to oxidize and expand commercially available graphite. The size of the oxidized graphite was adjusted by sonicating the samples for different periods of time. The material was also thoroughly characterized and demonstrated to have two distinctive average size distributions and possess functional groups. The results suggest that different size flakes can trigger different cell response. The synthesis, characterization and biological evaluation of graphene nanoshells were performed. The graphene nanoshells were produced by using magnesia nanoparticles as a template to the graphene nanoshells. The coating of magnesia with graphene layers was accomplished using chemical vapor deposition. The nanoshells were obtained by removing the magnesia core. The size of the nanoshells was determined by the size of the magnesia nanoparticles and presented a broad size distribution since the diameter of the magnesia nanoparticles could not be controlled. The nanoshells were also characterized and the biological evaluation was performed in the Swiss Federal Laboratories for Materials Science and Technology (EMPA), in Switzerland. The results suggest that despite inducing the production of reactive oxygen species on cells, the nanoshells did not impede cell proliferation<br>Die Herstellung, Charakterisierung und biologische Auswertung von verschiedenen Graphen-basierten Nanopartikeln mit einer potenziellen biomedizinischen Anwendung wurden erforscht. Die vorgestellten Ergebnisse im Rahmen dieser Arbeit zeigen, dass eukaryotische Zellen unterschiedlich reagieren können, wenn sie mit Nanopartikeln unterschiedlicher Morphologie interagieren. Die Zellen können geringe Unterschiede in der Morphologie, insbesondere der Größe der Nanopartikeln, identifizieren. Dies unterstreicht den Einfluss der Herstellungsmethoden und die Notwendigkeit einer gründlichen Charakterisierung, um ein effektives Design von Nanopartikeln für biologische Anwendungen zu erreichen. Um den Einfluss der Größe von Graphen-basierten Nanopartikel auf das Zellverhalten zu erforschen, wurden verschiedene Graphen-beschichte Eisenoxid-Nanopartikelproben durch eine kolloidchemische Methode hergestellt. Dieses Herstellungsverfahren ermöglicht die Synthese von Nanopartikeln mit engen Größenverteilungen, die als monodispers gelten können. Vier Proben mit unterschiedlichen Durchmessern (von 10 bis 20 nm) wurden hergestellt und vor den biologischen Untersuchungen systematisch charakterisiert. Die Probencharakterisierung deutet auf eine Mischung aus Magnetit- und Maghemit-Kristallphasen hin, außerdem besitzen die Nanopartikel eine dünne Graphitschicht. Die spektroskopischen Ergebnisse auch zeigen außerdem, dass alle Proben funktionelle Gruppen auf ihrer Oberfläche besitzen, sodass sie in allen Aspekten, außer Morphologie (Durchmesser), ähnlich sind. Die biologischen Untersuchungen deuten darauf hin, dass Zellen unterschiedliche Größen von Eisenoxid-Nanopartikeln reagieren können. Ein in situ Untersuchung der Beschichtung der Eisenoxid-Nanopartikel wurde mit einem Transmissionelektronenmikroskop durchgeführt. Die Ergebnisse zeigen, dass eine dünne Schicht von Ölsäure aus dem Syntheseprozess auf den Nanopartikeln verbleibt. Diese Schicht kann mit einem Elektronstrahl in Graphen umgewandelt werden. Die Dicke der Graphitschicht auf den Nanopartikeln kann durch die Menge der eingesetzten Ölsäure kontrolliert werden. Die in situ Beobachtungen der Graphenumwandlung konnte durch erhitzen der Nanopartikeln in einem dynamischen Vakuum reproduziert werden. Das Brennen der Eisenoxid-Nanopartikel ermöglicht nicht nur die Graphitisierung der Ölsäure, sondern auch eine Verbesserung der magnetischen Eigenschaften der Nanopartikel für weitere Anwendungen, z. B. der Hyperthermie. Die Umwandlung der Ölsäure in Graphen konnte so als relativ einfaches Verfahren der Beschichtung von zweidimensionalen (2D) Substraten etabliert werden. Die Herstellung von Nanographenoxid mit unterschiedlichen Größen wurde mit der Hummers-Method durchgeführt. Die unterschiedlichen Größen der Nanographenoxidpartikel wurde durch eine Behandlung in Ultraschallbad erreicht. Zwei Proben mit deutlicher Verteilung wurden mit mehreren Verfahren charakterisiert. Beide Proben haben Nanographenoxid Nanoteilchen mit verschiedenen funktionellen Gruppen. Die biologische Charakterisierung deutet darauf hin, dass unterschiedliche Größen des Nanographens ein unterschiedliches Zellverhalten auslösen. Abschließend, wurde die Herstellung, Charakterisierung und biologische Auswertung von Graphen-Nanoschalen durchgeführt. Die Graphen-Nanoschalen wurden mit Magnesiumoxid-Nanopartikeln als Template hergestellt. Die Beschichtung des Magnesia mit Graphen erforgte durch die chemische Gasphasenabscheidung. Die Nanoschalen wurden durch Entfernen des Magnesia-Kerns erhalten. Die Größe der Nanohüllen ist durch die Größe der Magnesia-Kerns bestimmt und zeigt eine breite Verteilung, da der Durchmesser der Magnesiumoxid-Nanopartikel gegeben war. Die Nanoschalen wurden ebenfalls mit Infrarot- und Röntgen Photoemissionspektroskopie charakterisiert und die biologische Bewertung wurde im Eidgenössische Materialprüfungs- und Forschungsanstalt (EMPA) durchgeführt, in der Schweiz. Die Ergebnisse zeigen, dass zwar die Produktion von reaktiven Sauerstoffspezies in den Zellen ausgelöst wird, diese sich aber weiterhin vermehren können
18
Campos, Anderson Massahiro de. "Influência do tamanho de nanoesferas de carbono na eletroanálise de fármacos: detecção de paracetamol em amostras biológicas." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/75/75135/tde-28082018-163810/.
Full textAbstract:
Neste trabalho desenvolvemos um procedimento simples para a separação de nanoesferas ocas de carbono (do inglês Carbon Spherical Shells ou CSS) em diâmetros entre 400 e 500 nm utilizando centrifugação corroborado pelas análises realizadas na microscopia eletrônica de varredura e de transmissão. A análise de sua composição química, realizada através da técnica de fotoelétrons excitados por raios X, indicou que as CSS são constituídas de 79% de carbono e 21% de oxigênio em sua superfície, apresentando grupos funcionais carbonila e hidroxila. Plataformas sensoriais distintas foram obtidas formando filmes homogêneos das CSS sobre o eletrodo de carbonno vítreo GCE (do inglês glassy carbon electrode ou GCE). Como resultado dos experimentos eletroanalíticos, observou-se o aumento da sensitividade do eletrodo GCE/CSS de acordo com a diminuição do diâmetro (500 até 400 nm) das CSS. As plataformas sensoriais GCE/CSS com 400 nm de diâmetro apresentaram maior sensitividade (0.02 μA µmol L-1) com um limite detecção de 0.2 μmol L-1. Os eletrodos GCE/CSS foram estáveis, apresentando pequena interferência de espécies concomitantes presentes na amostra e seu desempenho na quantificação de paracetamol em suor mostrou-se estatisticamente equivalente ao método padrão baseado em cromatografia líquida.<br>We applied a simple strategy, based upon centrifugation, to separate carbon spherical shells (CSS), in sizes varying from 400 to 500 nm, which is shown by the micrographs obtained in the Scanning and Transmission Electron microscopy analysis. In their surface, carbonyl and hydroxyl groups were present, constituting a composition of 21% of oxygen and 79% of carbon. The CSS were casted on a glassy carbon electrode\'s (GCE) surface, forming a thin film, and the resulting platform was used as a sensor. A trend was observed in the results obtained by the electroanalytical experiments: as the size of the CSS were reduced, the sensibility of the GCE/CSS platform towards paracetamol detection increased. The best attained result, namely the platform with the GCE and the 400 nm diameter CSS, have shown promising results, achieving sensitivity\'s value of 0.02 μA μmol-1 L. The proposed sensors were stable, displaying little interference from another species coexisting in the samples, and its performance towards paracetamol detection were statistically identical to the standard method for paracetamol detection based upon liquid chromatography.
19
Dahl, Gregor Thomas [Verfasser]. "Zirconia microparticles and gold nanoshells: building blocks for novel functional materials in catalysis and high-temperature photonics : Zirkonia-Mikropartikel und Gold-Nanoschalen: Bausteine für neuartige funktionelle Materialen in Katalyse und Hochtemperatur-Photonik / Gregor Thomas Dahl." Hamburg : Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky, 2020. http://d-nb.info/122108416X/34.
Full text
20
Kisukuri, Camila de Menezes. "Mudanças na interface de nanopartículas de Au/Ag e lipases: seus efeitos na atividade enzimática." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-24032014-085448/.
Full textAbstract:
Nesta dissertação estão descritos os resultados obtidos sobre a preparação de nanocascas funcionalizadas (nanopartículas ocas) de ouro/prata de diâmetro de 50 nm e imobilização de diferentes lipases (Burkholderia cepacia (BCL) e pâncreas de porco (PPL)). [Obs.: A imagem do esquema pode ser visto no arquivo PDF] Inicialmente as nanocascas de ouro/prata (NSs AgAu) foram sintetizadas e caracterizadas, através de imagens de MEV e MET. Através destas imagens algumas características das NSs AgAu foram elucidadas, como seu tamanho e sua característica oca. Em seguida, a funcionalização das NSs AgAu com diferentes moléculas mercapto-alcanóicas e uma molécula mercapto-amina foi realizada. Depois de funcionalizadas as NSs-funcionalizadas foram ativadas, com glutaraldeído ou EDC, para que assim elas ficassem aptas à imobilização das lipases, via ligação covalente. Para a BCL foi possível imobilizar 0,155-0,282 mg de proteína/3 mg do suporte. No caso da PPL uma menor quantidade de enzima foi imobilizada (0,035-0,048 mg/3 mg do suporte). A atividade da enzima imobilizada foi testada frente à reação de acetilação enantiosseletiva do (R,S)-1-feniletanol com acetato de vinila (RCE, resolução cinética enzimática). Excelentes resultados de conversão (50%) e seletividade (E > 200) foram conseguidos com a BCL imobilizada em todos os suportes. A PPL livre não catalisava a acetilação deste substrato e quando esta enzima foi imobilizada nas diferentes NSs-funcionalizadas, os resultados apresentados para acetilação enantiosseletiva do (R,S)-1-feniletanol com acetato de vinila foram interessantes. Nesse caso conseguimos alcançar conversões de até 4% do substrato R à sua forma acetilada com excelente enantiosseletividade ( > 99% e.e. do produto). Como uma alternativa de demonstrar a atividade enzimática da BCL imobilizada em reação tradicional de hidrólise, o teste da hidrólise do palmitato de p-Nitrofenila pela BCL livre e imobilizada foi realizado. Este teste revelou que a BCL imobilizada nas NSs-funcionalizadas catalisavam a hidrólise do palmitato de p-Nitrofenila mais rápido que a enzima livre, comprovando os bons resultados obtidos na RCE, mostrando que os sistemas onde tínhamos a BCL imobilizada foram mais eficientes que a enzima livre. As NSs AgAu, NSs-funcionalizadas e até as nanocascas contendo as lipases imobilizadas foram caracterizadas por de imagens de MEV e MET, análises de FT-IR e método de Bradford. Outros estudos com os sistemas contendo a BCL imobilizada foram elucidados. Diferentes funcionalizadores de diferentes tamanhos foram utilizados e a influência de cada um deles sobre a atividade enzimática foi estudado. Por exemplo, quando as NSs AuAg foram funcionalizadas com moléculas mercapto-alcanóicas menores, como por exemplo, o ácido mercapto acético, melhores resultados para a RC do (R,S)-1-feniletanol foram conseguidos. As diferentes formas de ativação da NSs-funcionalizadas utilizando glutaraldeído ou EDC, para consequente imobilização da BCL não resultaram em alterações da atividade enzimática na RC, apresentando valores idênticos para RCE. Experimentos para testar a estabilidade dos sistemas contendo a BCL imobilizada também foram feitos. Descobrimos que é possível armazenar a BCL imobilizada nos diferentes sistemas à - 4 °C por até 28 dias. O estudo da reciclagem destes sistemas revelou que por até 3 ciclos os sistemas conseguiram manter 90% da atividade enzimática.<br>This dissertation presents the results achieved on the preparation of functionalized gold/silver nanoshells (hollow nanoparticles, 50 nm) and immobilization of different lipases (Burkholderia cepacia (BCL) and porcine pancreatic (PPL)). Initially Gold/Silver nanoshells (NSs Ag Au) were synthesized and characterized through SEM and TEM pictures. By these images some characteristics of NSs AgAu were elucidated, as its size and hollow feature. The functionalization NSs AgAu with different mercapto-alkanoic molecules and mercapto-amine molecule was next step performed. After the functionalized NSs-functionalized were activated with glutaraldehyde or EDC, after that they remained suitable for the immobilization of lipases via covalent bond. BCL was possible immobilized 0.155-0.282 mg protein/3 mg of support. And the PPL a smaller amount of enzyme was immobilized (from 0.035-0.048 mg / 3 mg of support). The activity of the immobilized enzyme was assayed by the reaction enantioselective acetylation of (R,S)-1-phenylethanol with vinyl acetate (KR, kinetic resolution). Excellent conversion results (50%) and selectivity (E > 200) were achieved with the immobilized BCL. The free PLP did not catalyzed acetylation of the substrate and when this enzyme was immobilized on NSs-functionalized the results for enantioselective acetylation of (R,S)-1-phenylethanol with vinyl acetate were interesting. In this case we achieve conversions of 4% of the substrate (R) to acetylated form with excellent enantioselectivity (> 99% e.e. of the product). As alternative to demonstrate the enzymatic activity of BCL immobilized on traditional hydrolysis reaction, the hydrolysis of p-nitrophenyl palmitate by free and immobilized BCL was performed. This test revealed BCL immobilized on NSs-functionalized catalyzed hydrolysis of p-nitrophenyl palmitate faster than free enzyme, confirming the good results obtained in KR, showing that systems which had immobilized BCL were more efficient than the enzyme free. The NSs AgAu, NSs-functionalized and Nanoshells containing the immobilized lipases were characterized by SEM and TEM images , FT-IR analysis , the Bradford method. Other studies with systems containing immobilized BCL were elucidated. Different spacers with different sizes were used for functionalized the nanoshells, and the influence of each of the enzymatic activity was studied. For example, when the NSs were functionalized with smaller molecules mercapto-alkanoic and cysteamine best results for the KR (R,S)-1-(phenyl)ethanol were obtained. The different forms of activation of NSs-functionalized using glutaraldehyde or EDC, for subsequent immobilization of BCL did not result in changes in enzyme activity in the KR . Experiments to test the stability of systems containing immobilized BCL were also made . We found it possible to store the BCL immobilized on different systems at - 4 ° C for 30 days. The study of the recycling of these systems was made and by 3 cycles systems maintain 90% of the enzyme activity.
21
Zimmermann, Nils E. R., Timm J. Zabel, and Frerich J. Keil. "Transport into zeolite nanosheets." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183170.
Full text
22
Haddow, Sarah Louise. "Perylene derivatives and silicon nanosheets." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/41873/.
Full textAbstract:
The work presented in this thesis explores two different topics of interest, firstly a synthetic project fabricating small building blocks for supramolecular arrays. The building blocks are a series of perylene monoimide monoahydride (PMIA) compounds, synthesised by a four step process. The PMIA compounds belong to a family of dyes called the rylenes which are known in literature for their optical properties and use in optoelectronic devices. Chapter 2 begins with the description of the synthesis and characterisation of these molecules, where Hirshfeld surface analysis is used to investigate the solid state intermolecular forces between adjacent molecules. This is followed by the details of connecting two PMIA through organic linkers and it explores the structural and physical properties of the so called dimer. The physical properties investigated include, optical and electronic properties utilizing spectroelectrochemistry, cyclic voltammetry and electron paramagnetic resonance techniques. The chapter also explores the asymmetric feature of the building blocks with the aid of X-ray crystallography. The second topic of interest is silicon nanosheets (SiNS). There are many types of these two dimensional (2D) materials published in literature, however one type which has had minimal attention is a buckled sheet structure known as layered polysilane. A synthetic and structural investigation into layered polysilane and closely related siloxene, are carried out in Chapter 3, identifying their bonding arrangement and topographic assembly through a range of analytical techniques. Like many other SiNS, it is proposed that this material can be used in nanotechnology devices in the future, and this thesis makes some way towards identifying the structure which is important in order to use them in such devices. Chapter 4 leads on to discuss the investigation into the modification of SiNS fabricated in Chapter 3, via a range of small organic molecules. This is another area in literature which has great scope for investigation and exciting potential for use in nanodevices. An important difference once the SiNS have been functionalised with small organic groups is their enhanced solubility, in comparison to being insoluble before functionalisation. This opens up a wealth of applications which require solution phase activity. A range of surface analytical techniques aid in identification of functionalised sheets and Chapter 4 details the challenges and successes.
23
Quinlan, Ronald A. "The functionalization of carbon nanosheets." W&M ScholarWorks, 2009. https://scholarworks.wm.edu/etd/1539623539.
Full textAbstract:
Carbon nanosheets are a novel two-dimensional nanostructure made up of 2-20 graphene atomic planes oriented with their in-plane axis perpendicular to the growth substrate. Previous efforts in developing nanosheet technology have focused on the characterization of the system and their development as an electron source due to the high atomic enhancement factor (beta) and low turn on field. Further investigation of nanosheets as high surface area electrodes revealed poor wetting by polymeric material and extreme hydrophobic behavior.;Because nanosheet technology has promise as a high surface area electrode material, this thesis research has focused on three areas of interest: the enhancement of nanosheets through chemical modification, the incorporation of the nanosheets into a polymeric composite and the delivery of a proof of concept measurement. We have successfully introduced defects into the graphene lattice of the nanosheet system via an acid treatment. Inspection of these defects by x-ray absorption near-edge spectroscopy (XANES) shows the introduction of two features in the spectra assigned to C=O pi* and C-O sigma* transitions. Thermal desorption spectroscopy (TDS) was used to identify the oxygen containing groups created during the functionalization as carboxylic and hydroxyl functional groups. These groups were identified through the combination of carboxylic, hydroxyl, anhydride and lactone peaks in the CO2, CO and H 2O TDS spectra. Deconvolution of the TDS spectra using 1st and 2nd order Polanyi-Wigner equations enables the calculation of desorption energy values for individual features and for the estimation of the number of atoms desorbing from the surface during a particular event. Identification of the exact nature of the functional groups was attempted through high resolution x-ray photoelectron spectroscopy (XPS) of the C(1s) and O(1s) peaks. Though the pairing of sub-peaks with specific functionalities of the system was not possible due to the complexities of the spectra, the trends observed in the data support the data gathered via the XANES and TDS experiments.;Also, a procedure for the classification of defect density and exact functionality was outlined. Deconvolution of the TDS spectra using 1 st and 2nd order Polanyi-Wigner equations enabled the calculation of desorption energy values for individual features and for the estimation of the number of atoms desorbing from the surface during a particular event. This information along with the changing sub-peak areas from dedicated and calibrated XPS system would allow for not only a more accurate estimation of defect density, but also for the identification of sub-peaks in the C(1s) and O(1s) spectra.;Finally, photoluminescence measurements of poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and MEH-PPV/nanosheet systems showed a quenching of three orders of magnitude for the MEH-PPV/nanosheet system suggesting that nanosheets are a viable option for excition separation in organic photovoltaics.
24
Rostamzadeh, Taha. "Engineering Nanoarchitectures from Nanosheets, Nanoscrolls, and Nanoparticles." ScholarWorks@UNO, 2016. http://scholarworks.uno.edu/td/2229.
Full textAbstract:
The ability to encapsulate/insert different kinds of nanoparticles (NPs) in scrolled nanosheets (NSs) may lead to the formation of new nanocomposite materials that yield novel properties. These nanostructures resemble “peapods” that consist of NPs chains (“peas”) located in a hollow space of desired nanoscrolls (“pods”). Depending on different combinations of “peas” and “pods” diverse families of nanopeapods (NPPs) can be synthesized which may exhibit interesting properties not accessible from the individual components. Though there exist various synthetic methods for the formation of NPPs, more development in terms of simplicity, flexibility, and productivity of synthetic approaches are needed so that different classes of NPPs with unique combinations/characteristics of “peas” and “pods” can be synthesized.
A simple solvothermal synthesis method for the encapsulation of spherical Fe3O4 NPs by the capture of preformed NPs in scrolled hexaniobate has previously been developed in our group. In the first part of this research, efforts were made to extend the “pod” materials to other inorganic NScs. Vanadate nanoscrolls (NScs) could rapidly (2h) be produced using a simple solvothermal treatment in the presence of V2O5 as vanadium source, and either dodecylamine (DDA) or octadecylamine (ODA) as the structure-directing agent. The synthesis parameters were successfully adjusted to obtain high yields vanadate NScs (~ 20 g of NScs per synthesis) with different average lengths as 383 nm, 816 nm to 3.3 µm. The effects of reaction time on the formation of NScs were also investigated.
Further efforts focused on the development of methods for making vanadate NPPs. Here, two novel approaches for the formation of these NPPs have been successfully developed. In the first, solvothermal methods utilizing preformed Ag NPs and vanadate NSs lead to the formation of Ag@vanadate NPPs where NPs could be encapsulated during the scrolling of NSs. High NP loadings were acquired with this approach. In the second method, an insertion strategy was developed where Ag NPs were drawn into the lumen of preformed vanadate NScs upon controlled solvent evaporation. This method was also quite effective, though much lower loadings of NPs were achieved with larger average NP-NP distances. Also noteworthy in the study of vanadate NScs and NPPs is the observation of an uncommon asymmetric scrolling behavior; this was realized for both vanadate NScs and solvothermally synthesized Ag@vanadate NPPs.
Novel solvothermal approaches for the effective construction of organic-MoOx hybrid structures and MoOx nanosheets (NSs) have also been developed. These NSs can be controlled so as to exist in different oxidation states as well as in different crystal structures. Layer spacing as a function of organic molecule lengths could also be controlled by changing the type of surfactants located between the NSs. Individual NSs or a few layers of stacked NSs, up to four micrometers in lateral size were successfully prepared upon sonication. The effect of time, temperature, as well as the type of structure-directing agents on the formation and crystal structure of MoOx intercalated compound/NSs were also explored.
Lastly, a modified solvothermal method previously used for the encapsulation of spherical Fe3O4 NPs inside hexaniobate NScs was applied for the construction of cubic-CeO2 NPPs. High yield encapsulations of preformed cubic ~5 nm ceria NPs within the lumen of hexaniobate NScs were readily accomplished. Size selective encapsulation and the formation mechanism of cubic-CeO2 NPPs were also studied. Pre-organization and attachment of ceria NPs to the surface/edges of hexaniobate crystals prior to the scrolling process were observed, which is in a good agreement with our previous studies on the formation mechanism of NPPs. Partially filled CeO2@hexaniobate NPPs were further used in the in-situ growth of gold NPs within the empty/hollow space of hexaniobate NScs. This led to the formation of high-quality Au-CeO2@hexaniobate NPPs. We believe that smart combinations of the methods for the formation of NPPs, encapsulation, in-situ growth and insertion, will allow one to acquire other classes of nanocomposite materials composed of different types, shapes, and arrangements of NPs in the hollow spaces of distinct NTs/NScs.
25
Li, Zhen. "POROUS PHOSPHOLIPID NANOSHELL PROTECTED APTAMER SENSOR FOR URINE MERCURY DETECTION." Thesis, The University of Arizona, 2010. http://hdl.handle.net/10150/193450.
Full textAbstract:
Mercury exposure has been related to neurological diseases and poisoning. Quantification of mercury in biological fluids, such as serum or urine is an important diagnostic method for mercury exposure. We have developed an aptamer-encapsulated porous phospholipid nanoshell (PPN) sensor for sensing mercury in urine using a modified 15-mer single strand DNA.1 The probe is protected from DNAse and other biofouling species by encapsulation within the porous liposomes composed of mixed phospholipids, allowing direct application of the aptamer in biological fluids containing DNAse and other biofouling materials. The encapsulated sensor was directly tested in urine samples at physiological pH. We were able to detect below 100 ppb (500 nM) Hg2+ in urine (urine mercury threshold set by Biologischer Arbeitstoff Toleranz Wert or BAT)1 with no sample preparation other than pH adjustment. These results suggest that porous phospholipid nanoshells (PPNs) can serve as a general-purpose protection scaffold for biological sensing.
26
Sayin, Ceren Sibel. "Density Functional Theory Investigation Of Tio2 Anatase Nanosheets." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12611075/index.pdf.
Full textAbstract:
In this thesis, the electronic properties of nanosheets derived from TiO2 anatase structure which acts as a photocatalyst, are investigated using the density functional theory. We examine bulk constrained properties of the nanosheets derived from the (001) surface and obtain their optimized geometries. We investigate properties of lepidocrocite-type TiO2 nanosheets and nanotubes of different sizes formed by rolling the lepidocrocite nanosheets. We show that the stability and the band gaps of the considered nanotubes increase with increasing diameter. We also study adsorption of
Aun clusters with (n=1,2,3,4) on the clean and oxygen depleted lepidocrocite surface. Through systematic investigation of various cases we conclude that Au preferres O
vacancy sites rather than clean surface in accordance with previous metal adsorption studies on TiO2 surfaces. For the clean surface, we observe that Au clusters with an odd number of atoms are weakly bonded and metallizes the system while even number of Au atoms results in small band gap semiconductors with relatively higher binding energies.
27
Zhu, Mingyao. "Carbon nanosheets and carbon nanotubes by RF PECVD." W&M ScholarWorks, 2006. https://scholarworks.wm.edu/etd/1539623509.
Full textAbstract:
A planar antenna RF plasma enhanced chemical vapor deposition apparatus was built for carbon nanostructure syntheses. When operated in inductive and capacitive plasma discharging modes, two carbon nanostructures, carbon nanotube (CNT) and carbon nanosheet (CNS), were synthesized, respectively.;A nanosphere lithography method was developed and used to prepare catalyst patterns for CNT growth. Using capacitively coupled C2H2/NH 3 plasma, randomly oriented CNT were synthesized on Ni dot patterned Si substrates. Aligned CNT arrays were grown on SiO2 coated Si substrates, using both C2H2/NH3 and CH 4/H2 capacitive plasmas.;When operated in inductive coupling mode, CNS were successfully deposited on a variety of substrates without any catalyst. Carbon nanosheets are a novel two-dimensional structure, have smooth surface morphologies and atomically thin edges, and are free-standing roughly vertical to substrate surfaces. CNS have a defective graphitic crystalline structure, and contain only C and H elements. Typical CNS growth parameters are 680??C substrate temperature, 40% CH4 in H2, 900 W RF power, and 100 mTorr total gas pressure. Morphology, growth rate, and structure of CNS change with the variations in the growth parameters. Increasing substrate temperature yields a less smooth morphology, a faster growth rate, and more defects in CNS; increasing CH 4 concentration causes a faster growth rate and more defects in CNS, but only slightly changes the morphology; increasing RF power results in a more smooth morphology, a faster growth rate, and less defects in CNS; and decreasing total gas pressure induces a less smooth morphology, a faster growth rate, and more defects in CNS.;In CNS growth mechanism, a base layer forms underneath the vertical sheets; the growth of CNS is through growth species surface diffusion; the electric field near substrate surfaces promotes and keeps the vertical orientation of the CNS, and the atomic hydrogen etching keeps the CNS atomically thin.;Carbon nanosheets have large surface areas, and can stabilize metal thin films into particles 3-5 nm in diameters. For field emission testing, typical CNS have turn-on fields of 5-10 V/mum, a maximum emission current of 28 mA, an emission current density of 2 mA/mm2, and a life-time of 200 hours.
28
Xu, Shiyu. "Characterisation of mesostructured films and single zeolite nanosheets." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/characterisation-of-mesostructured-films-and-single-zeolite-nanosheets(2a2a1047-bf17-49c1-b711-120e98ac4cf2).html.
Full textAbstract:
Thin nanoporous films are attractive for many potential uses for example gas separation, catalysis, filtration of viruses, ore flotation, or as low-dielectric-constant materials. Zeolite and mesoporous materials are the two important nanoporous material classes. In this thesis, we synthesized and characterized two different thin nanoporous films; (i) mesostructured films at the mica-solution interface; (ii) mechanical exfoliated zeolites. The mesoporous materials are well-defined pore shoe and size, and exhibit various morphologies, such as thin films, etc. In contrast, zeolites are a kind of perfect crystal and the morphologies are strongly related to their structures and are difficult to control. Therefore, first we synthesis mesostructured films at mica-solution interface in acidic solution. In-situ Atomic Force Microscopy (AFM) has been used to reveal the formation process of organic and inorganic mesophase films at the molecular level. Then, we synthesized two-dimensional zeolite structures via mechanical exfoliation process that does not involve any chemical intervention and can be applicable to a wide variety of structures with different chemical makeup. Three different zeolite structure nanosheets related to the structure code MWW, UTL, and MFI have been prepared. AFM and TEM have been used to characterized the exfoliated single nanosheet. In order to broaden the application of the single zeolite nanosheet, platinum nano-clusters are encapsulated within mechanical exfoliated zeolite MFI nanosheets by ion exchange from aqueous solution of [Pt(NH3)4](NO3)2. High-angle annular dark field scanning transmission electron microscopy has been used to indicate the Pt clusters in the zeolite MFI structures. Because of the property of the mechanically as-synthesised exfoliated MFI nanosheets that is the long hydrocarbon chains are essentially intact on both sides of the inorganic layer, and can prevent thickening of the zeolite MFI nanosheets along b-axis, we use the mechanically exfoliated MFI as seeds for further growth to form large scale MFI membrane with uniform nano-thickness. Encapsulating noble metals within the channels or cavities of zeolites has already drawn numerous attentions because the well-defined zeolite structure is able to constrain the metal nanoparticle (NPs) aggregation size and enhance the diversity and activity for catalysis. We use the organic surfactant (C22-6-6Br2) and [Pt(NH3)4](NO3)2 as the structure and metal precursor to form Pt-containing nanowires; and use F- to inhibit the premature precipitation of Pt precursors. After involving F-, the Pt-containing nanowire structures were generated.
29
Nepal, Arjun. "Graphene nanosheets produced via controlled detonation of hydrocarbons." Diss., Kansas State University, 2015. http://hdl.handle.net/2097/20523.
Full textAbstract:
Doctor of Philosophy<br>Physics<br>Christopher M. Sorensen<br>We demonstrated that gram quantities of pristine graphene nanosheets (GNs) can be produced via detonation of a hydrocarbon. This one-step and catalyst-free method is eco-friendly and economical for the production of GNs. The hydrocarbons detonated were C₂H₂, C₂H₄, C₃H₈ and CH₄ in the presence of O₂. The carbon products obtained from the detonation were analyzed by XRD, TEM, XPS and Raman spectroscopy. Depending upon the ratio of O₂ to C₂H₂, the GNs of size up to ~ 250 nm, SSA up to ~ 200 m²/g and yield up to 70% with 2-3 layers' stack have been obtained so far. N₂O was determined as a good alternative to O₂ as an oxidizer to produce GNs by detonating C₂H₂ with it.
A two-color pyrometer was designed and calibrated to measure the temperature of the detonation of hydrocarbons. The measured detonation temperatures were in between 2700 K and 4300 K. Along with the high detonation temperature, the composition of precursor hydrocarbon was observed to be crucial as well to determine its suitability to detonate with oxidizer to produce GNs. The hydrocarbons C₂H₂ and C₂H₄ were determined as the suitable precursors to produce GNs whereas detonation of C₃H₈ yields mere amorphous carbon soot and CH₄ gives no solid carbon while detonated with O₂. It has been proposed that the hydrocarbons with C/H≥0.5 are suitable for GNs production by detonation method.
Highly oxidized graphene nanosheets (OGNs) were produced by solution-based oxidation of GNs prepared via a controlled detonation of acetylene at O₂/C₂H₂=0.8. The produced OGNs were about 250 nm in size and hydrophilic in nature. The C/O ratio was dramatically reduced from 49:1 in the pristine GNs to about 1:1 in OGNs, as determined by X-ray photoelectron spectroscopy. This C/O in OGNs is the least ever found in all oxidized graphitic materials that have been reported. Thus, the OGNs produced from the detonated GNs with such high degree of oxidation herein yields a novel and promising material for future applications.
30
Khan, Simeen. "Colloidal PbS and PbS/CdS Core/Shell Nanosheets." Bowling Green State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1447955111.
Full text
31
Neupane, Chandra Prasad Neupane. "Time Resolved Optical Spectroscopy of Colloidal PbS Nanosheets." Bowling Green State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1530805332385177.
Full text
32
Premathilaka, Shashini M. "Synthesis and Optical Properties of Colloidal PbS Nanosheets." Bowling Green State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1561463157379607.
Full text
33
Mudd, Garry William. "III-VI metal chalcogenide semiconductor nanosheets and heterostructures." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33512/.
Full textAbstract:
This thesis presents an investigation into the properties of III-VI metal chalcogenide semiconductor nanosheets and demonstrates their capability to enhance graphene-based optoelectronics. Strong quantization effects and tunable near-infrared-to-visible (NIR-to-VIS) photoluminescence emission are reported in mechanically exfoliated crystals of gamma-rhombohedral semiconducting InSe at room temperature. The optical properties of InSe nanosheets differ qualitatively from those reported for transition metal dichalcogenides and indicate a crossover from a direct-to-indirect band gap semiconductor when the InSe nanosheet thickness, L, is reduced to a few nanometres, corresponding to the emergence of a ‘Mexican hat’ energy dispersion for the valence band. At low temperature, radiative recombination of photoexcited carriers bound at native donors and acceptors in nominally undoped InSe nanosheets is observed. A two-dimensional hydrogenic model for impurities is used to describe the increase in binding energy with decreasing L and reveals a strong sensitivity of the binding energy on the position of the impurities within the nanolayer. The application of a magnetic field, B, perpendicular to the plane of InSe nanosheets induces a marked change of the observed optical spectrum. A transfer of intensity from a low-to-high energy component at high B corresponds to an indirect-to-direct band gap crossover, which arises from the Landau quantisation of the in-plane carrier motion and crossover between hole cyclotron orbits centred on closed edges of the valence band. High broad-band (NIR-to-VIS) photoresponsivity is achieved in mechanically formed InSe–graphene van der Waals heterostructures, which exploit the broad-band transparency of graphene, the direct bandgap of InSe, and the favourable band line up of n-InSe with graphene. The photoresponse is dependent on the electron transit time through the InSe layer, as evaluated by a semiclassical model.
34
Zimmermann, Nils E. R., Timm J. Zabel, and Frerich J. Keil. "Transport into zeolite nanosheets: diffusion equations put to test." Diffusion fundamentals 20 (2013 ) 53, S. 1-2, 2013. https://ul.qucosa.de/id/qucosa%3A13629.
Full text
35
Bhandari, Ghadendra B. "Synthesis and AB-Initio Simulations of Colloidal PBS Nanosheets." Bowling Green State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1403519605.
Full text
36
Oldenburg, Steven Jay. "Light scattering from gold nanoshells." Thesis, 2000. http://hdl.handle.net/1911/19543.
Full textAbstract:
Gold nanoshells consist of a dielectric core surrounded by an ultra thin shell of gold. By adjusting the ratio between the radius of the core and the thickness of the shell the plasmon resonance of the nanoshell can be placed at any wavelength from 500 nm--2500 nm. As the dimensions of the nanoshell approaches the wavelength of incident light, the extinction spectrum becomes a superposition of the multipole plasmon resonances. Adjustments to the core:shell ratio centered either the dipole or quadrupole mode at 830 mn. The distinct far field scattering distribution from each multipolar mode agreed well with calculations. The plasmon resonance condition and the local surface roughness give rise to intense local fields at the surface of the particle. When mercaptoaniline was absorbed onto nanoshells that had a plasmon resonance in the near IR, enhancements of the Raman signal by more than five orders of magnitude were recorded.
37
Radloff, Corey J. "Concentric nanoshells and plasmon hybridization." Thesis, 2004. http://hdl.handle.net/1911/18684.
Full textAbstract:
The optical properties of metal nanostructures are related to their plasmon response, which is sensitively dependent on nanostructure geometry and environment. The metallodielectric, core-shell structure of nanoshells represents a unique geometry allowing for the systematic tunability of the plasmon resonance of the nanostructure. This is accomplished by varying the relative dimensions of the core and shell layers. Fabrication of a nanoshell particle with a strong plasmon resonance is dependent on shell quality, which is strongly dependent on the careful preparation of the metal shell. The resonant response of metal nanostructures can also be modified through plasmon-plasmon interactions. This work focuses on the fabrication of nanoparticles with a multilayer, concentric-shell structure consisting of a silica core, inner gold shell layer, silica spacer layer, and an outer gold shell layer. This concentric nanoshell particle is fabricated through the controlled growth of a nanometer-scale silica layer around a preformed nanoshell. The silica layer was found to increase the thermal and chemical stability of the nanoshell particles. A second gold shell could be grown on this layer to generate the concentric nanoshell particle. This layered nanoparticle geometry has a plasmon resonance dependent on the interaction between the inner and outer shell plasmons. This interaction can be explained in terms of a sphere-cavity model of plasmon hybridization derived from a semi-classical model of the plasmon resonance. Varying the dimensions of the concentric shell layers can independently and systematically control the plasmon resonance of the inner and outer shell, which effects the interaction between the two plasmons. The coupling between the inner and outer shell plasmons was investigated experimentally by varying the concentric nanoshell dimensions, specifically examining how the spectral detuning of the inner and outer shell resonances and spatial interaction between inner and outer shell plasmons determine the nanoparticle's optical properties. Calculations using Mie scattering theory to model the nanoshell plasmon response agree quantitatively with experimental measurements of the nanoshell plasmon resonance in both the single-layer and multi-layer regime.
38
Westcott, Sarah Linda. "Ultrafast electron dynamics in gold nanoshells." Thesis, 2001. http://hdl.handle.net/1911/18049.
Full textAbstract:
In metallic nanostructures, the interaction of excited electrons with the nanostructure surface may result in electron relaxation dynamics that are significantly different than those predicted by electron-lattice coupling. These ultrafast electron dynamics were monitored by pump-probe measurements of the time-resolved change in transmission. Using femtosecond pulses from a cavity-dumped titanium-doped sapphire laser, two types of nanoparticles with a core-shell geometry were studied.
Nanoshells are nanoparticles with a dielectric core surrounded by a continuous thin metal shell. For nanoshells, the plasmon resonance wavelength is tunable by changing the core and shell dimensions. For nanoshells with a gold sulfide core and a gold shell, two conditions were observed under which electron relaxation was different than predicted by electron-phonon coupling. First, electron relaxation occurred more rapidly for gold-gold sulfide nanoshells embedded in polymer films than for nanoshells dispersed in water, with lifetimes of 1.6 ps and 3 to 5 ps, respectively. Second, for nanoshells dispersed in water, the electron relaxation lifetime decreased with adsorption of p-aminobenzoic acid (to 1.7 ps) or aniline (to 1.9 ps) on the nanoshells. With adsorbed n-propylamine or p-mercaptobenzoic acid, electron relaxation transpired in 2.8 ps or 2.4 ps, respectively. Density functional theory calculations indicated that the molecules leading to the fastest electron relaxation possessed the largest induced dipole moments near a metal surface.
Semicontinuous gold films grown around a silica nanoparticle core exhibited spectral and dynamical optical signatures of the percolation threshold. Compared to continuous shells, the electron dynamics in the semicontinuous shell layer were dramatically different as additional induced bleaching was observed in the first 500 fs. The observed dynamics are consistent with a rate equation model in which the electrons are initially excited in localized surface plasmons or "hot spots" and subsequently achieve an equilibrium with electrons throughout the film on a timescale faster than electron-phonon thermalization.
39
Lee, Min-Ho. "Gold nanoshells for optical coherence tomography." Thesis, 2006. http://hdl.handle.net/1911/18935.
Full textAbstract:
Near infrared tuned gold nanoshells have been developed to enhance the contrast of optical coherence tomography (OCT) images, and we have completed a systematic study which quantifies and optimizes the specifications of nanoshells that provide improved efficacy of OCT imaging and photothermal ablation of cancer. The optical properties of gold nanoshells, such as scattering, absorption, and asymmetry values were calculated with Mie scattering theory. For comparison and experimental quantifications, scattering coefficients were extracted from OCT images using Extended Huygens-Fresnel (EHF) principle based algorithms.
With the addition of Her2 conjugated nanoshells, ex vivo OCT images of human breast cancer tissue, which express signatures of Her2/neu, provide significant contrast in comparison to the normal and malignant controls. As an extended study of dual NIR absorbing/scattering nanoshells for integrated cancer imaging and therapy in vitro, combined OCT imaging and photothermal tumor ablation was performed in vivo. Results showed that gold nanoshells selectively accumulated in the tumorous regions and enabled clear differentiation of tumor. Tumor regression by the photothermal ablation using NIR tuned nanoshells was also reported. Our studies have demonstrated that nanoshells can be designed specifically for diagnostic and therapeutic purposes.
40
Jiang, Chong-Yu, and 江崇煜. "Plasmonic Modes Analysis of Metallic Nanoshells." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/84903552682256550271.
Full textAbstract:
碩士<br>國立臺灣大學<br>應用力學研究所<br>99<br>The plasmonic modes of Au and Ag nanoparticles (NPs) and nanoshells (NSs) excited by plane waves and electric dipoles are studied by using Mie theory and dyadic Green’s functions; e.g. the dipole, quadrupole and sextupole modes. For the plane wave excitation, the absorption and scattering cross sections are analyzed. For the dipole excitation, the near-field and far-field responses (e.g. radiative and nonradiative powers) are analyzed. Furthermore, to study the enhanced FRET between a donor and acceptor by these modes, two types (symmetric and anti-symmetric) of bi-dipole are used for simulation.
Numerical results show that anti-symmetric bi-dipole can excite the dipole and sextupole modes, and the symmetric one the quadrupole and octupole modes. These modes are in agreement with those excited by a plane wave. For Au NP and NS, only the dipole and quadrupole modes are observed, while the other higher-order modes are not. In addition, there is a strong absorption band at 510-540 nm. For the Ag NS, the dipole, quadrupole, sextupole, and octupole modes are observed. Moreover, these modes are red-shifted as the ratio of the core radius to the shell thickness increases. In addition, the strong absorption band is at 330-355 nm. The quadrupole mode exhibits its superiority in the near and far fields. Therefore it can be utilized to form a resonant cavity for enhancing the FRET of a donor and acceptor. This is to say the quadrupole mode of Ag NS can be used to realize the spaser-based nanolaser.
Finally, the plasmonic modes of Ag/Au alloy NS are studied. These modes are in between those of Ag NS and Au NS, depending on the ratio of alloy.
41
Hirsch, Leon Robert. "Diagnostic and therapeutic applications of metal nanoshells." Thesis, 2004. http://hdl.handle.net/1911/18640.
Full textAbstract:
Metal nanoshells are a new class of optically tunable core/shell nanoparticles which are finding numerous applications in biomedicine due to their biocompatibility, chemical functionability, and optical tunability in the near infrared (a region of light where tissue is optically transmissive). The following work explores the design of near infrared resonant nanoshells for two new diagnostic and therapeutic biomedical applications. For diagnostic purposes, near infrared resonant nanoshells were found to be optically detectable in whole blood and proved capable of detecting sub-nanogram levels of analyte in whole blood in under 30 minutes. For therapeutic purposes, near infrared absorbing nanoshells were heated in tumors using higher laser powers. Excitation of near infrared resonant nanoshells promoted photothermal destruction of cancerous growths in vitro as well as in vivo. In vitro, nanoshell treated cells were photothermally ablated upon near infrared excitation with no detectable damage to cells receiving lasers only. Similar results were found in whole tissue. Using a live mouse model, a complete therapy system was demonstrated where systemically delivered nanoshells were found to preferentially accumulate into tumors. Near infrared excitation of these tumors provided complete recovery in 55% of the cases, while controls displayed a mean survival time of only 15--20 days.
42
Jackson, Joseph Bryan. "Surface enhanced Raman scattering with metal nanoshells." Thesis, 2004. http://hdl.handle.net/1911/18648.
Full textAbstract:
A systematic investigation of surface enhanced Raman scattering (SERS) was performed using metal nanoshells as the substrate. Nanoshells are a dielectric sphere coated with a thin metal shell, which have a well understood, geometrically tunable plasmon resonance. This tunability allows for the engineering of the optical near field for SERS. A simple model connecting the nanoshell electromagnetic near field at the incident frequency to that at the Raman shifted frequency is discussed. This theory is compared to the measured SERS response of the nonresonant molecule para-mercaptoaniline (pMA) adsorbed on silver and gold nanoshells.
Using a solution of silver nanoshells, at an excitation wavelength of 1064 nm enhancements on the order of 106 to 108 were observed. Accounting for reabsorption of the Raman scattered light as it traverses the solution suggests enhancements of 1012.
To mitigate the reabsorption, film geometries were investigated. For film measurements a 782 nm excitation laser was used. The SERS response of a dense film of silver nanoshells followed the calculated single nanoshell response of the nanoshells whose plasmon resonance was tuned near the excitation wavelength. In contrast, for nanoshells blue shifted from the excitation laser, the film Raman response followed an estimated dimer response.
The Raman response as a function of nanoshell density was studied using films of gold nanoshells dispersed on the surface of polyvinylpyridine (PVP) coated glass slides. A linear dependence of the Raman modes on the nanoshell density was observed confirming that the single nanoshell plasmon dominates the SERS response. The SERS enhancements for nanoshell films calculated by direct comparison to an unenhanced measurement were on the order of 10 10 to 1012.
The Raman response as a function of incident intensity was measured for dense silver nanoshell films. An optical pumping model allowing for stimulation of the Raman emission is proposed. Using this model, an effective unenhanced Raman cross section of the order of 10-27 cm2 is found. This is comparable to cross sections obtained in unenhanced Raman measurements. Evidence for two photon photoluminescence by nanoshells is presented. It is proposed the Raman emission is stimulated by the two photon photoluminescence.
43
Loo, Christopher Han-Yan. "Gold nanoshells: Contrast agents for molecular imaging." Thesis, 2006. http://hdl.handle.net/1911/18943.
Full textAbstract:
Cancer remains a significant health concern today. It is the 2 nd leading cause of death in the United States. Critical to controlling cancer-associated morbidity and mortality is early detection. Early detection strategies include detecting molecular-level changes prior to phenotypic changes, enabling a sufficient amount of time for effective therapies to be implemented. Not only is early detection critical, but issues such as patient safety and cost should be considered when implementing these strategies. This thesis examines work using nanoshell-based optical contrast agents for early cancer detection using scattering-based optical imaging systems.
Metal nanoshells are a novel class of optically-tunable nanoscale material that are composed of a dielectric core (usually silica) surrounded by a metallic shell (usually gold). By systematically varying the ratio between core diameter and shell thickness, the absorption and scattering maxima can be tuned to different wavelengths including those in the visible and near infrared (NIR).
Specific Aim 1 addresses the fabrication of NIR scattering nanoshells for use as optical contrast agents to enable scatter-based cellular imaging. Specific Aim 2 focuses on using dual NIR absorbing/scattering nanoshells for a nanoshell-based integrated cancer imaging and therapy application. Finally, Specific Aim 3 addresses the diagnostic capabilities of gold nanoshells ex vivo using reflectance confocal microscopy (RCM).
44
Oldenburg, Steven Jay. "The designer optical resonances of metal nanoshells." Thesis, 1998. http://hdl.handle.net/1911/17201.
Full textAbstract:
Metal nanoshells consist of a dielectric or semiconducting core coated with a metallic layer of nanometer scale dimensions. Gold nanoshells with silica cores were fabricated by first attaching gold colloid to the surface of the silica spheres and then developing the attached gold into a complete shell. This technique formed continuous gold shells approximately 10 nm thick. By varying the relative dimensions of the core and the shell, the optical resonance of these nanoparticles can be varied over hundreds of nanometers in wavelength, extending from the visible into the infrared region of the spectrum. For a gold nanoshell with a 340 nm core, at shell thicknesses exceeding 15 nm, additional peaks appeared in the UV-visible spectrum. Calculations based on a vector basis solution to Maxwell's equations matched both the position and relative magnitude of these secondary peaks.
45
Averitt, Richard Douglas. "Gold nanoshells: Optical properties and femtosecond electron dynamics." Thesis, 1998. http://hdl.handle.net/1911/19240.
Full textAbstract:
The chemistry, optical properties, and femtosecond electron dynamics of gold nanoshells are described. The gold nanoshells consist of Au-coated Au$\sb2$S nanoparticles prepared via aqueous phase chemistry using HAuCl$\sb4$ and Na$\sb2$S. During the course of the reaction, the plasmon-related absorption peak first shifts from $\sim$650 nm out to $\sim$900 nm, then shifts back to $\sim$650 nm. It is shown, using generalized Mie scattering theory, that this plasmon peak shift is determined by the relative thickness of the Au shell and the Au$\sb2$S core diameter. This understanding of the optical properties of these nanoparticles is used to elucidate the nanoparticle growth kinetics. The dynamics of the electrons in the Au shell are studied with femtosecond pump-probe spectroscopy using a cavity-dumped Ti:sapphire laser. The induced change in the transmission of the gold nanoshell films studied has a lifetime of $\sim$1.6 ps. The origin of the measured signal is shown to be due to the creation of a hot electron distribution that returns to equilibrium via electron-dissipative interactions with the nanoparticle core and the embedding medium.
46
YI-FANHSU and 許異凡. "Surface Plasmon Properties of Metal Nanoparticles and Nanoshells." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/86331713221193113153.
Full textAbstract:
碩士<br>國立成功大學<br>光電科學與工程研究所<br>98<br>In this thesis,we use the finite difference time domain method (FDTD) to simulate the surface plasmon resonance characteristics of nanoscale metallic nanoparticles,which are of different sizes and structure. The study results show that to change the incident angle of light can lead to different surface plasmon resonance mode for metallic nanoparticles placed on silicon substrate.
Besides, we also study multilayer of gold nanoparticles mixed with nanoshell structure, which provides a high degree of sensitivity in the resonant wavelength. The optical tunability can be regulated by controlling the size of core and shell to achieve the required resonance absorption wavelength,this allows the plasmon resonances into visible to near-infrared region. When the multilayer of gold nanoparticles mixed with nanoshell in defective cases, it was found that a larger offset correlates with red shifts in the resonance peaks , this phenomenon can be explained by plasmon hybridization theory.
When two multilayer of gold nanoparticles mixed with the shell adjacent to each other, we observe the relation between distance and resonance wavelength of absorption, and also discuss the effect of changing radius of core and shell on the resonance frequency mode.
47
Chung, Hung-Yi, and 鍾弘毅. "Study of surface plasmon resonance for metallic nanoshells." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/77533936851894216945.
Full textAbstract:
博士<br>臺灣大學<br>物理研究所<br>98<br>First of all, we present an approach alternative to the hybridization model for the treatment of the coupled interfacial plasmon modes in metallic nanoshells. Rather than formulating the problem form the Lagrangian dynamics of the free electronic fluid, we adopt an effective medium approach together with the uniqueness of the solutions to electromagnetic boundary value problem, from which the polarizability of the shells can then be systematically and efficiently derived; and the resonance frequencies for the coupled modes can be obtained from the poles in the polarizability.
Secondly, by using this effective medium theory we study the modified dipole-dipole interaction between the molecules in the vicinity of a spheroidal metallic nanoshell. From which huge enhancement of the energy transfer rate is obtained due to the resonant excitation of the bounding and anti-bounding plasmonic modes of the nanoshell.
Finally, we study the optical properties of a metallic nanoshell composite with particular focus on the effects of variation in temperature and particle clustering on these properties. One unique result from our modeling is the persistent manifestation of the single-particle resonances of the individual nanoshells which cannot be found in a composite of solid particles.
48
Tsai, Hsiao-Yen, and 蔡孝彥. "Optical Properties of Gold Nanorods and Nonconcentric Nanoshells." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/87984346176567711609.
Full textAbstract:
碩士<br>國立臺灣大學<br>應用力學研究所<br>99<br>In this thesis, we studied the interactions among fluorescent molecules, visible light and gold nanorods (GNRs) or silica-coated gold nanorods, nonconcentric gold nanoshell (GNSs). Based on Maxwell''s equations, the multiple-multipole (MMP) method was used to solve these problems. We studied the surface plasmon resonances (SPRs) of these nanoparticles irradiated by different incident plane waves with different polarizations. In additionally, the average effect was studied by considering all possible incident directions. Moreover, the electric dipole was used to simulate a fluorescent molecule for analyzing the plasmonic enhancement on fluorescence resulting from the coupling between these nanoparticles and the molecules.
The results indicate that the longitudinal SPR of GNR of larger aspect ratio and larger radius is more red-shifted, and the absorption and scattering cross sections become larger. The longitudinal SPR of silica-coated GNR is red-shifted from that of bare GNR. In addition, the enhancement factor of GNR on fluorescence is sensitive to the location and the orientation of molecule. When the molecule is placed at the end-cups of GNRs and oscillates along the long axis, a larger enhancement factor is obtained. A larger GNR can improve the enhancement factor. For the GNR dimer, the symmetry of this structure can induce a bonding-mode resonance at a longer wavelength. On the contrary, as the symmetry of GNR dimer is reduced, the antibonding-mode resonance of a shorter wavelength is induced.
The nonconcetric GNSs produces an enhanced electric field at the thinnest gold shell region. Hence, the electric field in the gap of a dimer can be enhanced, if the thinner gold shells of dimer are close to each other.
49
Chen, Zhi-Yuan, and 陳志源. "Coating of Ag Nanoshells on Iron Micro-powders." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/pecsxx.
Full textAbstract:
碩士<br>國立成功大學<br>化學工程學系碩博士班<br>92<br>In this thesis, Fe-core/Ag-shell composite micro-particles were prepared for large electric and magnetic losses. The thin Ag nanoshells not only increased the conductivity but also protect the iron powders from oxidation. Three methods were evaluated for the fabrication of Ag nanoshells on the iron powders：(1) microemulsion technique, (2) polyol process, (3) electroless plating method. From the analyses of TEM and XPS, it was found that the combination of polyol process and electroless plating method gave a better coating of Ag nanoparticles on the surface of iron powders. Using the combined method, two types of Fe@Ag composite micro-particles (R-2521&IF-029) were prepared. The repeated coating increased the surface coverage and the Ag amount coated. For R-2521 type, Ag nanorods with different lengths were formed on the particle surface when the coating number was above 5. It was noteworthy that, for IF-029 type, the oleic acid adsorbed on the powder surface facilitated the coating of Ag nanoshells. The thermogravietric analysis (TGA) revealed that the anti-oxidation property of iron powders was significantly enhanced by the complete coating of Ag nano-shells. For IF-029 type, the oxidation temperature of composite powders with 10.5wt% Ag was raised largely from 300 to 450℃. For R-2521 type, the shielding effectiveness (SE) was not significantly affected by the coating of Ag. But for IF-029, the SE seemed to be affected by the Ag amount coated. In addition, the complete coating of Ag nanoshells on the surface of hollow glass micro-spheres was also achieved using the conventional electroless plating method. Without sensitization and activation, ferrite@Ag composites powders were also prepared by electroless plating method.
50
"Nanoshells in vivo imaging using two-photon excitation microscopy." Thesis, 2010. http://hdl.handle.net/1911/62198.
Full textAbstract:
This thesis describes the development and optical characterization of near infrared (NIR) gold nanoshells for the use as luminescent contrast agents for applications in small animal blood vessel imaging. Two types of gold-silica nanoshells excitable by NIR lasers are investigated: Type 1 nanoshells can be excited with a sub-mum NW laser, whereas Type 2 nanoshells can be excited with a NW laser in the micrometer range. Using NIR microscopy as an imaging platform, ex vivo and in vivo experiments are conducted to determine the efficacy of these nanoshells as suitable contrast agents. Specifically, individual particles of Type 1 nanoshells are successfully imaged and shown to provide bright optical contrast for blood vessel imaging both ex vivo and in vivo, while the Type 2 nanoshells are clearly imaged within the blood vessels ex vivo. These positive results suggest a promising possibility of developing a new class of contrast agents for deep tissue imaging and improving the imaging depth of NIR imaging techniques.