Surface acoustic wave (SAW) sensors detect chemical and biological species by monitoring the shifts in frequency of surface acoustic waves generated on piezoelectric substrates. Incorporation of nanomaterials having increased surface area as sensing layer have been effective in improving the sensitivity as well as miniaturization of SAW sensors. Selectivity, sensitivity and speed of response are the three primary aspects for any type of sensor. This dissertation focuses on design and development of SAW devices with novel transducer configurations employing nanomaterial sensing layers for enhanced sensing, improved selectivity, and speed of response. The sensing mechanism in these SAW sensors is a complex phenomenon involving interactions across several different length and time scales. Surface acoustic wave propagation at the macro-scale is influenced by several kinetic phenomena occurring at the molecular scale such as adsorption, diffusion, reaction, and desorption which in turn depend on the properties of nanomaterials. This suggests the requirement of a multi-scale model to effectively understand and manipulate the interactions occurring at different length scales, thereby improving sensor design. Sensor response modeling at multiple time and length scales forms part of this research, which includes perturbation theories, and simulation techniques from finite element methods to molecular-level simulations for interpreting the response of these surface acoustic wave chemical and biosensors utilizing alloy nanostructures as sensing layers. Molecular modeling of sensing layers such as transition metal alloy nanoclusters and nanowires is carried out to gain insights into their thermodynamic, structural, mechanical and dynamic properties. Finite element technique is used to understand the acoustic wave propagation at the macroscale for sensing devices operating at MHz frequencies and with novel transducer designs. The findings of this research provide insights into the design of efficient surface acoustic wave sensors. It is expected that this work will lead to a better understanding of surface acoustic wave devices with novel transducer configurations and employing nanomaterial sensing layers.

This research focuses on the microwave properties of nanoparticles for use as contrast and hyperthermia agents. Currently, visible light is used for irradiation of nanoparticles as hyperthermia agents. Additionally, visible/Near-infrared light is used for photoacoustic tomography (PAT) imaging. Compared to optical wavelengths, frequencies in microwave range transmit through tissue with high penetration depth . Thus, deep cancerous cells and malignant tissue may be treated and imaged. These nanoparticles could enable the use of a hybrid microwave/acoustic technique known as thermoacoustic tomography. Here, quantitative measurements of the heat generation in super paramagnetic iron oxide nanoparticle (SPIONs), gold nanoparticles (AuNPs), and gold nanoclusters (AuNCs) induced by microwave energy at 3 GHz, are presented and compared. Based on our experiments, SPIONs are the most efficient nanoparticles for microwave heating. Very high concentrations of SPIONs are able to convert microwave energy into heat about 22° C more than DI-water. AuNPs, which support plasmon resonances, do not provide heat under microwave irradiation as predicted by our computational analysis based on Mie Theory. AuNCs are a new form of ultra-small (<2.5 nm) AuNPs which do not support plasmonic resonances and have supra-molecular properties such as sub-conduction band transitions. Interestingly, AuNCs have the potential to absorb microwave energy and may provide an alternative to SPIONs. These nanoparticles had not yet been studied before in this frequency region. In addition, the absorption coefficient of nanoparticles were calculated using complex permittivity data from a dip probe kit and a Vector Network Analyzer (VNA) in a broad band range from 500 MHZ to 10 GHz. This method allows identification of best frequency region with highest penetration depth. In the last step, the nanoparticles with different concentrations were tested as exogenous contrast agents in a Thermoacoustic Tomography (TAT) system. TAT utilizes the penetration depth of microwave energy while producing high resolution images through acoustic waves. The addition of an exogenous contrast agent improves image quality by more effectively converting microwave energy to heat. The experiment reveals that the time resolved thermoacoustic signal (TA) from SPIONs is stronger than AuNPs and AuNCs and thus, the image contrast produced by SPIONs is stronger than the two other aforementioned nanoparticles.

Novel Studies on the Formation and Chemical Reactivity of Compound Clusters and Their Precursors in the Gas and Liquid Phase James A. Bradshaw 139 Pages Directed by Dr. Robert L. Whetten Presented are four separate and unique studies on molecular and nanoscale systems: Atmospheric hydration and aggregation of NaCl clusters, highly water-soluble aurous-thiolate oligomers, water-soluble gold clusters from aurous-thiolate oligomer precursors, and gold iodide clusters. Adsorption of water on cationic and anionic sodium chloride clusters is investigated to elucidate active sites of molecular interaction as well as primary aggregate formation kinetics. Considered an exceptionally abundant atmospheric species, experiments are conducted to further quantify gas phase chemistry and hydration/solvation of alkali halides. Currently the most soluble of all known gold-thiolates, para-mercaptobenzoic acid-based (pMBA) aurous-thiolate oligomers are investigated and physical and chemical properties quantified. Solubility, structural conformation, and poly-dispersity of higher homologs are observed with the goal of further applications in clusters research, medical and biomedical, and industry. Gold thiolate clusters, synthesized using pMBA-based oligomers, are investigated through reductive formation in solution. UV-VIS and UV-VIS-NIR spectroscopy is undertaken to assign structures based on predictions of the HOMO-LUMO gap and other electronic transitions. Gold iodide is investigated in relation to the common thiolate-halide analogy. Synthesis and characterization of a solid precursor as well as anion and cation cluster formation is presented as part of an ongoing collaboration.

Ce travail aborde le sujet des d efauts charg es dans le silicium. Jusqu' a pr esent, les d efauts charg es ont principalement et e etudi es en conditions p eriodiques (PBC). En e et, l'approche PBC est parfaite pour simuler unsolide in ni. Mais, comme je le montre dans ce chapitre, elle apporte aussi des artefacts. En particulier dans le traitement de l' electrostatique, o u des traitements math ematiques important doivent ^etre utilis es pour supprimer les interactions non d esir ees entre r epliques. Notre approche vise a simuler correctement un d efaut charg e, tout en conservant de bonne propri et es pourle mat eriau massif. Elle consiste a simuler le d efaut dans un nano-agr egat. Le traitement de l' electrostatique est correct dans un nano-agr egat et les r esultats obtenus peuvent ^etre extrapol es au mat eriau massif, comme il est montr e dans ce chapitre. Les perspectives de cette m ethode sont aussi abord ees ici. / In this work we have studied Si clusters with point defects in various charged states. Point defects in semiconductors affects the electronic structure of the material introducing new energy levels and consequently new modes of transport.Detailed study of the point defects have been undertaken in various approaches. The most common practice is to usesuper-cell calculations under the framework of Density Functional Theory with Periodic Boundary Conditions (PBC). Inthis formalism there are a lot of factors like defect-defect interactions, image charge interactions, that are to be correctedfor to achieve the " artefact-free" results. In this study we have used Free Boundary Conditions with nano-clusters of Sipassivated with Hydrogen at the surface. Previous works have undertaken in detail the geometrical effects in the nanoclusters. But a complete picture of the electrostatics and its effect on the energy states demand a complete study. Hence inour calculations we take another approach, devoid of the correction factors for cases with PBC, and produce an alternativeway to calculate the formation energy of the defects. We have described the formation and stability of the defects invarious charged states and provided with a detailed analysis of the properties pertaining to the nano-scale size. Finallymigration parameters are provided with respect to the charge states of the defects. Our results are also compared with thePBC calculations with critical discussions.

Les alliages ODS (Oxides Dispersion Strengthened), sont principalement étudiés pour leur capacité à répondre favorablement au cahier des charges de la fonction de gainage combustible pour les réacteurs nucléaire de type RNR-Na (Réacteur à Neutrons Rapides à caloporteur sodium). Elaborés par métallurgie des poudres, mécanosynthèse puis extrusion, ils affichent des propriétés mécaniques, et notamment en fluage, extrêmement intéressantes. Néanmoins, la voie élaboration utilisée induit une forte anisotropie microstructurale. Cette anisotropie se retrouve au niveau de leurs propriétés mécaniques et conduit à une fragilité dans le sens de sollicitation transverse. Le but de cette thèse est d'étudier l'évolution microstructurale de ces matériaux. Les aciers ODS présentent des microstructures ultra fines en termes de grains, de précipités, et de formation d'amas qui conduisent à de grandes difficultés pour en obtenir la recristallisation. De plus, les microstructures obtenues présentent souvent une recristallisation avec croissance anormale. De telles évolutions demandent des investigations à très fine échelle et ont été relativement peu examinées dans le domaine des alliages ODS. Il faut en effet être capable d'une étude structurale la plus quantitative possible de la microstructure des nanograins, ainsi que de la précipitation afin d'étudier les mécanismes d'interaction précipitation / joints de grain. Ceci n'est possible que par un couplage de différentes méthodes : la microscopie électronique en transmission (en particulier avec l'utilisation des outils récemment développés pour l'étude de la nanotexturation, i.e. ACOM-TEM); la diffusion centrale des neutrons ou des rayons X; et enfin la sonde atomique tomographique, à la fois pour apporter les informations sur la morphologie et la chimie des amas et nanoprécipités mais surtout sur la composition chimique aux joints de grains. A partir de l'identification des mécanismes contrôlant la croissance anormale, une modélisation permettant de prédire son apparition dans la microstructure est confrontée à cette caractérisation microstructurale poussée. Cette modélisation prête une attention particulière à la migration des joints de grains couplée à la diffusion et effets d'ancrage préférentiel des joints triples par les précipités ainsi qu'à l'énergie motrice stockée sous forme de densité de dislocation. / Oxide Dispersion Steels (ODS) alloys are mainly studied for their ability to fulfil the technical specifications required for Sodium Fast Reactor (SFR) fuel cladding application. Their processing involves powder metallurgy, mechanical alloying and extrusion. Therefore, despite their interesting mechanical creep properties, the extrusion processing involves a high microstructural anisotropy. These particular feature leads to poor mechanical properties in the transverse direction which are worsen by the occurrence of abnormal grain growth. Unfortunately, since internal pressure increases in the tube with the accumulation of gas fission products, the major stress component is precisely applied in the transverse direction. As a result, the material faces a critical risk of failure and control of the microstructure is a key issue. The aim of this thesis is to study the microstructural evolution of ODS ferritic steels. ODS ferritic steels show ultrafine microstructures in terms both grains and precipitates which made the recrystallization very difficult and allow for abnormal grain growth. To observe such evolutions, fine scale microstructure characterization are necessary. This is only possible by coupling different characterization methods: transmission electronic microscopy (in particular with the new developed tools for nanotexturation studies, i.e. ACOM-TEM); neutron and X-ray small angle scattering; and atomic probe tomography. Based on the mechanisms that lead to and control the abnormal grain growth, a model to predict the occurrence of abnormal grain growth is confronted to the experimental results. This model that takes a particular attention to the dislocation stored energy effect to adequately reproduce the observed characterization results.

As propriedades ópticas de nanocristais de silício (Si-ncs) têm sido extensivamente estudadas após a primeira demonstração em 1990 de fotoluminescência altamente eficiente em silício poroso. Apesar dos progressos no entendimento da natureza da alta eficiência da luminescência dos Si-ncs e da enorme versatilidade para aplicações optoeletrônicas, este campo ainda é um tema de controvérsia devido à complexidade destes materiais. Além disso, as condições de preparação ainda afetam as propriedades de emissão destes materiais que são de fundamental importância para as aplicações tecnológicas. O presente trabalho teve como objetivo o estudo das propriedades óticas dos Si-ncs e entender os processos fotofisicos envolvidos na recombinação radiativa de éxcitons altamente confinados nesse sistema. Si-ncs embebidos em matriz amorfa de SiO2 foram preparados a partir de filmes de oxido de silício SiyO1-y subestequiométricos (y&ge;1/3) depositados em substratos de quartzo utilizando um sistema deposição CVD na fase estimulada por plasma (electron cyclotron resonance-plasma enhanced chemical vapor deposition ou ECR-PECVD). Esta técnica oferece boa passivação e estabilidade interfacial Si/SiO2. O tratamento térmico a altas temperaturas (900°C&le;Ta&le;1100°C) promove a precipitação do silício dentro da matriz, favorecendo um processo de nucleação e crescimento dos Si-ncs. Foram realizados tratamentos térmicos nos filmes sob atmosferas de Argônio (Ar) ou (Ar+5%H2) por duas horas. As distintas atmosferas promoveram a passivação de defeitos superficiais, principalmente de ligações pendentes pelo Hidrogênio. As propriedades associadas diretamente à fabricação, tais como estrutura cristalina, morfologia, tamanho e química da superfície dos Si-ncs foram correlacionadas com os processos de emissão envolvendo éxcitons. A caracterização estrutural foi realizada por Raio-x (XRD), Microscopia de Transmissão de Alta Resolução (HRTEM), Retroespalhamento de Rutherford e Espectroscopia Raman. As medidas óticas foram basicamente Absorção, Excitação Seletiva, Fotoluminescência CW (PL) e Fotoluminescência Resolvida no Tempo. Os resultados da caracterização indicaram que efeitos de confinamento quântico e de estados de superfície dominam o processo de recombinação no Si-nc/SiO2. Em conclusão, os resultados obtidos neste trabalho mostram uma interessante e uma nova correlação entre as condições de fabricação da amostra e os processos de recombinação de éxcitons em Si-nc/SiO2. Todos estes resultados desafiam modelos anteriores propostos para explicar as propriedades ópticas do sistema de Si-nc/SiO2 e prevê ajudar na futura aplicação tecnológica dos mesmos. / The optical properties of silicon nanocrystals (Si-nc) have been extensively studied after the first demonstration in 1990 of highly efficient photoluminescence in porous silicon. Despite progress in understanding the nature of high luminescence efficiency of Si-ncs and versatility for optoelectronic applications, this field is still a subject of controversy due to its complexity. Furthermore, the preparation conditions still affect the emission properties of these materials that are of fundamental importance for technological applications. This work aimed to study the optical properties of Si-ncs and to understand the photophysical processes involved in the radiative recombination of excitons strongly confined in this system. Si-ncs embedded in amorphous SiO2 were prepared from silicon oxide films of substoichiometric SiyO1-y (y&ge;1/3) deposited on quartz substrates using a CVD deposition system in phase stimulated by plasma (electron cyclotron resonance-plasma enhanced chemical vapor deposition ou ECR-PECVD). This technique provides good passivation and Si/SiO2 interfacial stability. The thermal treatment at high temperatures (900°C&le;Ta&le;1100°C) promotes the precipitation of silicon within the matrix, favoring a process of nucleation and growth of Si-ncs. The thermal treatments were performed in the films under Argon atmosphere (Ar) or (Ar+5%H2) for two hours. The use of different atmospheres allowed the understand of the passivation process of surface defects, particularly of dangling bonds by Hydrogen. The properties directly related to fabrication such as crystalline structure, morphology, size and surface chemistry of Si-ncs were correlated with emission processes involving excitons. The structural characterization was performed by X-Ray Diffraction (XRD), High resolution transmission electron microscopy (HRTEM), Rutherford Backscattering and Raman spectroscopy. The optical measurements were basically Absorption, Selective excitation, CW photoluminescence (PL) and Time Resolved Photoluminescence. The characterization results indicate that both quantum confinement and surface states effects dominate the recombination process in Si-ncs/SiO2. In conclusion, the results obtained in this work show an interesting and a novel correlation between the sample fabrication conditions and the exciton recombination process in Si-ncs/SiO2. All these results challenges previous models proposed to explain the optical properties of Si-nc systems and are expected to help further technological applications of this system.

Doctor of Philosophy / Department of Chemistry / Duy H. Hua / The discovery of new methodologies to advance the fields of synthetic organic, nanoclusters, and polymer chemistry is critical in the asymmetric synthesis of organic compounds. Particularly, catalytic asymmetric oxidation reactions are economic. The oxidation reactions provide chiral molecules and additional functionality onto the molecules for functional group manipulation. New kinds of polymers, namely chiral-substituted poly-N-vinylpyrrolidinones (CSPVPs), stabilize the bimetallic nanoclusters such as Pd/Au or Cu/Au and induce chirality. These chiral polymers wrap around the nanometer-sized (~3 nm) bimetallic nanoclusters and catalyze a number of enantioselective oxidation reactions using oxygen or hydrogen peroxide as the oxidant. Cycloalkanediols were asymmetrically oxidized by 1 atm of oxygen gas to yield the corresponding hydroxyl ketone under the catalysis of Pd/Au (3:1) – CSPVP nanoclusters. Alkenes were oxidized by Pd/Au (3:1)-CSPVP nanoclusters under 2 atmospheric of oxygen in water to give the syn-dihydroxylated products in high chemical and excellent optical yields. Various cycloalkanes underwent regio- and enantio-selective C-H oxidation with Cu/Au (3:1)-CSPVP and 30% hydrogen peroxide to produce the corresponding chiral oxo-molecules in very good to excellent chemical and optical yields. We further discovered an enantioselective desymmetrization of , -dialkenyl-alkanols and , -dialkenyl-amino acid ethyl esters to give chiral disubstituted lactones and lactams, respectively. A number of medium-sized natural products and drugs were also oxidized regioselectively to give the corresponding mono-oxygenated products. A broad-spectrum predictive C-H oxidation of complex molecules is possible. Chapter 1 mainly discussed the synthesis and characterization of the new classes of chiral substituted PVP and bimetallic nanoclusters. Chapter 2 focus on various kind of oxidation reactions by the catalysis of CSPVP stabilized bimetallic nanoclusters. Among various bioluminescence assays, firefly luciferase based bioluminescence assays are popular due to their high specific activity, low background noise and ease of use. However, it has been found that some aromatic carboxylic acid substantially inhibited the firefly luciferase reporter enzyme’s activity. In order to study firefly luciferase inhibition and the proteins associated with inhibition mechanism, we designed two 6-(dimethylamino)-2-phenylisoindolin-1-one derivatives as probe molecules. The synthesis of one probe molecule is discussed in Chapter 3 and the further investigation of its inhibitory activity on firefly luciferase is being conducted by our collaborate.

Ligand-protected metal nanoclusters (NCs), which are ultra-small nanoparticles marked by their atomic precision, are distinctly importance for contemporary nanomaterials. NCs have attracted significant research attention for utilizing their novel optical and physicochemical properties in various applications, including fluorescence sensing, catalysis, and biomedical applications. This dissertation deals with ligand-protected atomically precise silver NCs and is divided into two main parts. The first part is focused on the exploration and design of well-defined silver NCs through surface co-ligand engineering. The second part is related to the development of silver NC-based frameworks (NCFs). In the first part, we designed a synthetic strategy based on engineering the structure of the phosphine co-ligands with thiols to generate the large box-shaped [Ag67(SPhMe2)32(PPh3)8]3+ (referred to as Ag67) NC. The strategy demonstrates that the combined use of judiciously chosen thiol and phosphine co-ligands can result in stable highly anisotropic box-like shapes. The optical absorption spectrum of the Ag67 NC displays highly structured multiple sharp peaks. The crystal structure shows a Ag23 core formed of a centered cuboctahedron (an unprecedented core geometry in silver clusters), which is encased by a layer with a composition of Ag44S32P8 arranged in the shape of a box. The electronic structure of this box-shaped cluster resembles a jellium box model with 32 free electrons. In the second part, a novel approach is developed for the assembly and linkage of atomically precise Ag NCs into one-dimensional (1D) and two-dimensional (2D) NC-based frameworks (NCFs) with atomic-level control over cluster size and dimensionality. With this approach three novel, but related, crystal structures (one silver NC and two NCFs) were synthesized. These structures have the same protecting ligands, and also the same organic linker. The three structures exhibit a similar square gyrobicupola geometry of the building NC unit with only a single Ag atom difference. The critical role of using a chloride template in controlling the NC’s nuclearity was demonstrated, as well as the effect of a single Ag atom difference in the NC’s size on the NCF’s dimensionality, optical properties, and thermal stability.

Title: Preparation of Nanocomposites of Metal Oxides in Plasma Polymer and Study of Their Properties Author: Oleksandr Polonskyi Department: Department of Macromolecular Physics, MFF UK Supervisor of the doctoral thesis: Prof. RNDr. Hynek Biederman, DrSc. Department of Macromolecular Physics, Faculty of Mathematics and Physics, Charles University in Prague Abstract: This thesis is devoted to a study of nanocomposite films Al (Al oxide)/plasma polymer prepared by various techniques using magnetron sputtering, plasma polymerization and cluster beam deposition. The formation and deposition of metal/metal oxide nanoclusters using a gas aggregation cluster source (GAS) was also considered. The role of low concentration of oxygen in the aggregation gas on the process of Al and Ti cluster deposition was studied. Properties of the nanoclusters and nanocomposite films were characterized by various techniques. Morphology of the nanocomposites was examined by AFM, TEM or HRTEM and SEM. Elemental analysis and chemical composition of the films were studied by XPS and FTIR. Optical characterization of the prepared films was done by UV-Vis spectroscopy and spectroscopic ellipsometry. It has been shown that using GAS nanocomposite Al(AlxOy)/C:H may be prepared. Keywords: nanocomposite thin film, plasma polymer, metal...

During the past few years, gold nanoparticles (AuNPs) have received considerable attention in many fields due to their optical properties, photothermal effect and biocompatibility. AuNPs, particularly AuNCs and AuNRs, exhibit great potential in diagnostics and imaging. In the present study, AuNCs were used to selectively image and quantify intracellular antioxidants. It was reported by Chen et al. that the strong fluorescence of AuNCs is quenched by highly reactive oxygen species (hROS). Most of applications depend on fluorescence quenching, however, for our project we designed turn-on fluorescent sensors using AuNCs that sense antioxidants. In the presence of antioxidants, AuNCs fluorescence switch on, while in the absence of antioxidants their fluorescence immediately turn off due to hROS effect. AuNRs were also used for cellular imaging in which AuNRs were conjugated to Cy3-labelled molecular beacon (MB) DNA. Next, the previous complex was loaded in two different strains of magnetotactic bacteria (MTB). MTB were used as a targeted delivery vehicle in which magnetosomes direct the movement of bacteria. The DNA sequence was specific to a certain sequence in mitochondria. The exposure of MTB to an alternating magnetic field (AMF) leads to the increase of temperature inside the bacteria, which destruct the cell wall, and hence, bacterial payload is released. When MD-DNA hybrid with the target sequence, AuNR and Cy3 separate from each other, the fluorescence of the Cy3 is restored.