Dissertations / Theses on the topic 'Hybrid-Nano System'

This work is generally aimed to synthesize POSS based BCPs via RAFT polymerization, to study their self-assembly behaviors, to research on the effect of POSS self-assembly structure on the bulk properties and to prepare nanostructured hybrid epoxy via self-assembly of POSS based copolymer. In Chapter1, We studied the RAFT polymerization of POSS macromers and capable to synthesize well defined POSS based BCPs with high POSS fraction and different topology such as AB，BAB and (BA)3. The vertex group and the morphology effect on thermo-mechanical properties of POSS based BCPs as well as the structure-property relationship was investigated. Dispersion RAFT polymerization in apolar solvent was applied and various aggregates with different morphology in Chapter2. Cooling induced reversible micelle formation and transition was found and the pathway selection in vesicle formation was investigated. Nano-construction of O/I hybrid epoxy materials based on POSS based copolymers was investigated in Chapter4. The effect of functional group content on miscibility of POSS based statistic copolymer and epoxy was investigated. A novel method to nanostructure epoxy hybrid involving self-assembly of POSS based BCPs in epoxy was presented. High homogeneity and well size/morphology control of core-corona structure containing rigid POSS core and soluble PMMA corona in networks were obtained.

In recent years, several groups have investigated the changes of chemical and physical properties of materials with size in the nanometer scale. These studies have highlighted a number of possible applications for nanostructures, which are now employed, for example, in biology and medicine for imaging, disease detection, diagnosis, sensing and therapy. In noble metals, the coherent collective oscillation of electrons in the conduction band (Surface Plasmon Resonance, SPR), induces large surface electric fields which greatly enhance the radiative properties of gold and silver NPs when they interact with resonant electromagnetic radiation. The coupling of SPR with the electromagnetic field may lead to a huge enhancement of both the absorption and scattering cross sections. The SPR, tunable in the visible (for spherical gold NPs) and near-infrared region (for anisotropic gold NPs) of the electromagnetic spectrum, can also interact, with the fluorescence emission of dyes and substantially modify their brightness and excited-state lifetime. One of the considerations that has inspired the present project is the expect that any change in the dielectric constant of the NP surface, induced, for example, by a biorecognition process that occurs on the surface itself, can produce a change in the emission properties of the fluorophores. SPR effect becomes also important when combined with two-photon excitation (TPE), which consists in the simultaneous absorption of two photons, each carrying about half the energy necessary to excite the molecule. In fact, the luminescence (TPL) induced by TPE is enhanced (when coupled with an appropriate plasmon resonance) by many orders of magnitude in gold nanorods respect to a standard fluorophore. These properties promise to improve the usefulness of these nanoparticles for in-vivo imaging in the NIR region of the electromagnetic spectrum and have inspired the second part of the project. The aim of the first part has been studied the interaction of gold nanoparticles a few nanometers in size with fluorophores and to exploit the changes of the dye excited-state lifetime and brightness induced by our interaction in solution under physiological conditions. I have investigated the system based on 5 and 10 nm gold NPs coupled (via a biotin-streptavidin linker) to a fluorophore (FITC) and to a specific protein antibody. The binding of protein to the gold NPs through antigen-antibody recognition modifies the dye excited-state lifetime, which change can then be used to measure the protein concentration. In particular, we have tested the nanodevice measuring the change of the fluorophore excited-state lifetime after the binding of the model protein bovine serum albumine (BSA) and p53 protein, a marker for early cancer diagnosis and prognosis (both in standard solution and in total cell extracts). These studies have been published in {J. Phys. Chem. C 2009 113(7) 2722-2730} and {J. Biom. Nanotech. 2009 5 683-691}. In the second part of the project I focused on the use of anisotropic gold nanoparticles as probe in cellular imaging. I have studied the optical properties of gold nanorods synthesized with standard surfactant CTAB (cetyl trimethylammonium bromide) and asymmetric branched gold nanoparticles synthesized with zwitterionic surfactant LSB (laurylsulphobetaine). The sample have been analyzed with a number of structural techniques to obtain a complete characterization: absortpion spectra, TEM images, Fluorescence Correlation Spectroscopy (FCS) and Dynamic Light Scattering (DLS) experiments in suspensions. From the analysis of the data, I have gained information on the nanoparticles shapes, dimension and aggregation numbers. In particular, three different populations have been found: nanospheres with diameter lower than 20 nm, nanostars characterized by large trapezoidal branches, and asymmetric branced nanoparticles with high aspect ratio (≈ 4-5) (published {Chem. Comm., 2011; 47; 1315-1317}). Moreover, TPL (two-photon luminescence) was finally exploited to study by optical microscopy the problems of internalization and toxicity of gold nanoparticles by different cell line (macrophages, HEK and A549). Presently, is in preparation a manuscript on TPL, cellular uptake and cytotoxicity of branched gold NPs. In the last year I have demonstrated the potential use of NPs, gold nanorods and magnetic nanoparticles (MNPs), as a novel contrast reagent for selective thermal therapy of cancer cells using a near-infrared low energy laser and an AC magnetic field, respectively. Photothermal therapy for cancer have been widely investigated as a minimally invasive treatment modality in comparison with other methods. The appeal of gold NRs as contrast agents is amplified by their additional capability to absorb photons and to convert into heat by nonradiative processes (phonon-phonon interaction). Magnetic nanoparticles heat inductively due to magnetic losses associated with three mechanisms: hysteresis, N\'eel relaxation and Brownian relaxation; moreover they are considered as a low toxicity material with gold and biological compatibility. These two kinds of NPs (gold and magnetic nanoparticles) are delivered to cancer cells and heated to induce apoptosis (programmed cell death). Within this last part of the project, I have first evaluated the increase in temperature of NR and MNP solutions, using a direct visualization by means of a sensitive thermocamera. Then I have developed a nano-sensor to measure the local temperature on the surface of the nanoparticles under excitation. The rationale is to bind an organic chromophore whose excited state lifetime (ESLT) is particularly sensitive to the temperature, and to refer to its lifetime which is an intensive parameter. Rhodamine B is such a fluorophore, with a temperature dependence of the excited state lifetime ≈ 0.029 ± 0.001 ns/°C, as we also measure here. Moreover this nanoconstruct can target tissues or single cells and used for imaging before the therapy. Part of these experimental results have been successfully composed to numerical simulations of light induced heating of gold nanorods, using the Two Temperature Model (TTM) in order to calculate raising in temperature due to laser irradiation. Finally, I have developed methods and knowledge in the field of the use of NPs made of gold or oxide ({Nanotoxicology, 2011; doi:10.3109/17435390}) in biological and medical research and applications. These studies have produced four publications and two additional manuscripts are under preparation on the cytotoxicity of these NPs and their use for imaging and phototherapy.

Le but de la Nano- Opto- Mécanique et Electronic à base de graphène est d'utiliser des membranes de graphène en suspension comme blocs de construction pour aborder le couplage entre l'optique, la mécanique et l'électronique dans ce nouveau matériau. Avec un module d'Young similaire à celui du diamant (1 TPA), le graphène est une membrane extrêmement rigide, légère et mince (epaaisseur de seulement un atome) qui peut supporter son propre poids sans effondrement ou la rupture lorsqu'il est suspendu. Ces membranes, intégrées dans des dispositifs mécaniques, peuvent être actionnés à partir de DC jusqu'à des fréquences de vibration mécaniques très élevées (GHz). En outre, le graphène est un gaz d'électrons 2D exposé pour lequel une porte électrostatique tunes considérablement la densité de porteurs de charge et ses propriétés optiques. Last but not least, il offre une architecture unique pour effectuer la fonctionnalisation physico-chimiques et obtenir des matériaux hybrides combinant les propriétés particulières des espèces chimisorbées avec ceux du graphène
The aim of the Graphene Nano- Opto- Mechanics and Electronics is to use suspended graphene membranes as building blocks to address the coupling of optics, mechanics and electronics in this novel material. With a Young modulus similar to that of diamond (1 TPa), graphene is an extremely stiff, light and atomically thin membrane that can withstand its own weight without collapsing or breaking when suspended. Such membranes, integrated as mechanical devices, can be actuated from DC up to very high mechanical vibration frequencies (GHz). Moreover, graphene is an exposed 2D electron gas for which an electrostatic gate dramatically tunes the charge carrier density and its optical properties. Last but not least, it provides a unique architecture to perform physico-chemical functionalization and obtain hybrid materials combining the peculiar properties of adsorbed and chemisorbed species with the graphene ones

Following the modern lines of development in theranostic field, this PhD research project focuses mainly on the field of oncological therapies where the primary purpose of the research is to increase the effectiveness of treatments and to decrease the undesirable toxic side effects of current therapies, which indiscriminately affect both sick and healthy cells, causing often serious collateral damages. The goal can be achieved by creating biocompatible smart systems that do not require carriers to function, but that are themselves able to "move" recognize and treat diseased tissues. The research project proposes the development of new organic/inorganic hybrid nanosystems having a core-shell-shell structure, consisting of nanoparticles (NPs) (Au and/or Fe3O4@Au) in which PEGylate porphyrin systems are bounded. The choice of synthesizing these hybrid systems, stems from the possibility of exploiting the different properties of the individual components, combined into a single complex system. The gold nanoparticles were chosen for the different properties in the theranostic field. AuNPs are considered to be relatively biologically non-reactive and therefore suitable for in vivo applications. Other advantageous qualities include the strong optical properties of AuNPs due to localized surface plasmon resonance (LSPR), easily controllable surface chemistry which enables versatility in adding surface functional groups, and lastly, the ease in control over particle size and shape during synthesis. Silver nanoparticles (AgNPs) are increasingly being investigated as tools for novel cancer therapeutics, capitalizing on their unique properties to enhance potential therapeutic efficacy. The AgNPs are a promising tool as anticancer agents in diagnostics and probing, with strong effects against different cancer cell lines offering many advantages. Their better penetration, and the possibility to track AgNPs in the body make them a more efficient tool in cancer treatment with less risk compared to standard therapeutic procedures. The unique AgNP properties, such as easy surface functionalization, optical properties, reproducible synthetic routes and high surface: volume ratio, makes them suitable for cancer treatment. The optical properties can be tuned to have an absorption at specific wavelengths that is useful for imaging and photothermal applications in tissue. The magnetite core will provide the paramagnetic properties necessary for use in the Targeted Drug Delivery (NPs tissues via magnetic field), in Magnetic Resonance Imaging and Magnetic Hyperthermia (the magnetic NPs may be subjected to an alternating magnetic field, overheating and thus determining cell death). The nanoscale dimensions of the complex system (40-100 nm) will allow the latter to perform passive targeting (EPR effect), while the external shell obtained by functionalization with the PEGylated porphyrins derivatives will induce the necessary water solubility and biocompatibility of the whole system. Given the excellent absorption spectroscopic properties, fluorescence (to monitor its presence inside the tissues) and photo-cytotoxicity (for the photodynamic therapy of tumors), it will be possible to strongly implement the field of application and efficiency of these nanohybrid systems. In synthesis, upon validation of the functioning of the system, the synthesis strategy can be adapted to functionalize and/or co-functionalize the nanoparticles also with active targeting agents to limit the accumulation exclusively in diseased tissues endowed with specific receptors, further implementing the targeting properties described above. Therefore, the results obtained during my PhD research work, could be a fundamental starting point in order to developing systems for theranostic applications, exploiting both the nanoparticles and the porphyrin derivatives properties, thus to obtain multifunctional platforms for biomedical applications.

This thesis describes the preparation and characterization of core-shell noble metal-magnetite hybrid hollow nanocomposites utilizing hierarchical architecture. The hollow magnetite (hFe3O4) nanoparticles were prepared by hydrothermal method, forming the cavity via Oswald ripening. Further surface modifications involved both inorganic and organic coatings, conferring the intracellular drug delivery ability and the catalytic enhancement. In the first part, a series of hierarchical core-shell nanostructures flower-like hFe3O4@AlOOH was synthesized through solvothermal method and sol-gel process. The formation of cavity accessible hFe3O4@γ-AlOOH was achieved using silica-templated solvothermal treatment where the Kirkendall effect was observed. The morphologies of the as-prepared nanocomposites were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR). Then, the nano-encapsulation of platinum drug using hollow magnetite and its derivatives, has been developed with improved loading efficiency via co-solvent system. A dimethylformamide/water co-solvent system was found to be the most efficient system to encapsulate water-insoluble cisplatin. The platinum content was further quantitatively and qualitatively analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and FTIR spectroscopy. The enhancement of loading efficiency could be driven by emulsification due to the diffusion of hydrophobic cisplatin into the hollow cavity of iron oxide nanoparticles. By incorporating water, the loading efficiency of hFe3O4 and hFe3O4@γ-AlOOH increased from 1-2% to 27% and from 6% to 54%, respectively. The grafting of cisplatin on AlOOH nanoflakes might account for the high loading efficiency of flower-like hFe3O4@AlOOH. As a complement to naked hFe3O4, a cell-penetrating poly(disulfide)s (CPD)-decorated hollow iron oxide nanoparticle was synthesized by immobilizing both cysteine and MPTMS as an initiator, followed by in situ polymerization to form hFe3O4-Cys-CPD-CONH2 and hFe3O4-MPS-CPD-CONH2. The morphologies were characterized by TEM/energy-dispersive X-ray spectroscopy (TEM/EDX) and the compositions of the as-prepared iron oxide nanocomposites were characterized by TGA, FTIR and X-ray photoelectron spectroscopy (XPS) and ICP-MS. The CPD coating not only serve as a protective layer, but also prevent the encapsulated cisplatin from a premature release. The hFe3O4-MPS-CPD-CONH2 exhibit promising features for the intracellular delivery of cisplatin, demonstrating a glutathione (GSH)-responsive drug release. Comparing with other hFe3O4 nanoparticles, an enhancement of cellular uptake of hFe3O4-MPS-CPD-CONH2 could be observed by optical microscope, showing rapid accumulation of the hFe3O4-MPS-CPD-CONH2 nanocomposites in the primary human renal proximal tubular epithelial cells (HRPTEpiCs) cell in 2 h. At 24 h, hFe3O4 (F), hFe3O4-MPS (FS) and hFe3O4-MPS-CPD-CONH2 (FSC) together with cisplatin treatment did not cause any significant cytotoxicity to the cells when the particle concentration is less than 10 µg/mL. Interestingly, FSCC showed a certain extent of toxicity with increasing Fe and Pt concentration along with the treated time. It may suggest that the hFe3O4-MPS-CPD-CONH2 nanoparticle, as a cisplatin carrier, could enhance the drug efficiency by increasing cellular uptake of the nanoparticles in HRPTEpiCs together with the boosted cytotoxicity. Based on these data, cisplatin- hFe3O4-MPS-CPD-CONH2 (FSCC) treatments with the concentration less than 20 µg/mL and duration no more than 24 h could maintain around 70% of the cell viability of the HRPTEpiCs. The hypothesis, at which CPD serves as an efficient carrier for intracellular cisplatin delivery, could be confirmed by both microscopic images and the cell viability test. In the second part, a series of Au/Fe3O4 hybrid nanocomposites was prepared to investigate their catalytic efficiencies using 4-nitrophenol reduction as a model system. The flower-like hFe3O4@γ-AlOOH@SiO2-NH2@Au was prepared by using protonated ammonium on hFe3O4@γ-AlOOH@SiO2-NH2 to entangle gold nanoparticles (AuNPs) via electrostatic attraction. In comparison to numerous of catalytic studies, the turnover frequency (TOF) of hFe3O4@γ-AlOOH@SiO2-NH2@Au shows a superior conversion rate up to 7.57 min-1 (4-nitrophenol per Au per min) for the 4-nitrophenol using sodium borohydride as a reductant. A rapid conversion of 4-nitrohpenol was observed using flower like composites that converted the 4-nitrophenol within 2 min. Our result suggests that silica residue hinders the reduction rate of the 4-nitrophenol. A significant deviation from pseudo first order was observed for densely AuNPs-functionalized nanoflower system, hFe3O4@γ-AlOOH@SiO2-NH2@Au2X, which is different from most of the 4-nitrophenol reductions reported in literature. The hFe3O4@γ-AlOOH@SiO2-NH2@Au also demonstrates catalytic activity when heated up to 800 °C before reduction. The recyclability was examined using magnetically recycled hFe3O4@γ-AlOOH@SiO2-NH2@Au, which showed insignificant decrease in the catalytic efficiency. To prove the concept, platinum nanoparticles (PtNPs) immobilized hFe3O4@γ-AlOOH@SiO2-NH2@Pt and hFe3O4@γ-AlOOH@SiO2-NH2@Pt/Au were also prepared via electrostatic attraction to verify the feasibility of endowing modular functionality via post modification.

El presente proyecto de investigación está enfocado al desarrollo de sensores químicos fluoro-cromogénicos, para la detección y determinación de especies químicas de interés biológico, industrial y medioambiental de forma selectiva y con alta sensibilidad. En forma general, se busca el diseñar nuevos sistemas sensores basados en compuestos (receptores) formados por dos unidades: una unidad coordinante que interacciona con el anión a determinar y una unidad generadora de señal que alerta del reconocimiento molecular efectuado. Durante este estudio se están preparando diversas moléculas receptoras funcionalizandas con grupos modificadores de estructura para evaluar su influencia sobre las capacidades de detección y selectividad como receptores de especies específicas en diferentes condiciones y medios. Las diferentes aproximaciones en prueba implican a su vez el diseño y síntesis molecular, así como el análisis de las diferentes señales ópticas producidas en el reconocimiento, con el fin de diseñar sistemas de alta eficacia y eficiencia, y con posibilidades reales de aplicación.
Santos Figueroa, LE. (2014). New approaches for the development of chromo-fluorogenic sensors for chemical species of biological, industrial and environmental interest [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/43216
TESIS
Premiado

碩士
國立清華大學
化學工程學系
92
Abstract A series of poly(4-vinyl pyridine)-b-poly(ε-caprolactone) diblock copolymers, P4VP-PCL, has been synthesized through sequential living ring-opening polymerization and atom transfer radical polymerization. In the P4VP-PCL diblock copolymers, a hybridization of inorganic and organic components can be achieved by coordination of P4VP block with inorganic elements whereas PCL block can be degraded by hydrolysis. Consequently, the self-assembly P4VP-PCL/inorganic materials hybrid system gives rise to a promising and convenient way for the manufacturing of mesoporous and nanoarrayed hybrid materials. A variety of self-assembly nanostructures including P4VP-rich cylinder, lamellae and PCL-rich cylinder has been obtained by simply varying the constituted volume fraction as evidenced by transmission electron microscopy and small-angle X-ray scattering. In-situ creation of gold (Au) nanoparticles in the phase-separated P4VP microdomains was formed by reduction of Au metal ions in the presence of N2H4 in dichloromethane as evidenced by Fourier transform infrared and ultraviolet experiments. Interesting phase-separated morphological evolution was observed by introducing various amounts of gold metal ions with P4VP-PCL. For instance, a significant phase transformation from cylindrical to lamellar nanostructure can be identified for diblock copolymer of VP32CL46 (fPVPv=40%) blended with Au metal ion at the molar ratio of nitrogen to gold around 5. By contrast, phase-separated nanostructure of P4VP-PCL might be destructed by strong coordination of P4VP block and Au metal ions. At the same gold content, the ratio of nitrogen to gold around 5, the lamellar nanostructure of VP146CL91 (fPVPv=61%) became disordered. As expected, the hybrid morphology is strongly dependent upon the content of Au metal ions and the original nanostructure of block copolymers. The observed morphological evolution for the hybrid system of P4VP-PCL/Au blends is consistent to the theoretical prediction on the basis of thermodynamics. Owing to the interaction of Au metal ion and the P4VP block, the introduction of Au nanoparticles having size below nanometer for the formed hybrid system is similar to the mixture of low molecular weight P4VP homopolymers and P4VP-PCL. As a result, the effected volume fraction of P4VP-rich phase is constantly increased with the added amount of reduction gold nanoparticles so as to induce phase transformation. On the other hand, the ordered self-assembly morphology might be destructed by the overdose of gold content due to overstretched P4VP chains within phase-separated microdomains. It is also interesting to find that the introduction of inorganic materials to block copolymers might promote the thermal properties of self-assembly system. As observed, the glass transition temperature of P4VP block can be significantly increased by coordinating reduction gold nanoparticles due to the crosslinking-like effect for the P4VP chains

碩士
龍華科技大學
機械工程系碩士班
102
This thesis focuses on the large-travel nano-scale positioning system, and developes a large-travel nano-scale position system driven by ball screw coupled with piezoelectricity based on the structural design concept of two-phase combination drive. According to the production and design cooperation program of Ministry of Science and Technology (MOST) - “Design and Motion Control Implementation of ARM-based Embedded Platform for Long Stroke Precision Servo System with High Speed”. The proposed system intends to satisfy demands for large-travel and high-precision positioning from fields such as ultra-precision processing and integrated circuit (IC) fabrication. The system uses a large-travel precision positioning platform driven by AC servo motor for large-travel high-speed nano-scale positioning, and a micro ultra-high precision positioning platform is added to realize nano-scale positioning compensation. This design can improve insufficient precision of the traditional ball screw positioning system. In addition to a large-travel nano-scale positioning platform driven by ball screw coupled with piezoelectricity, we build the mathematical models assoclated with the large-travel precision positioning platform and micro high-precision positioning platform, according to their working principles and basic features of the driving mechanism. In terms of system control, the system utilizes the embedded system for positioning control over the large-travel nano-scale positioning platform driven by ball screw coupled with piezoelectricity. Experiments and performance tests are conducted on the large-travel precision positioning platform and micro ultra-high precision positioning platform under different conditions. The experimental results show that the piezoelectric actuator can improve positioning precision of the large-travel precision positioning platform. The final position precision can quickly reach minimum resolution 40nm of optical scale, and maximum travel can reach 300mm, proving the proposed large travel and high precision of the positioning system developed in this thesis to be feasible.

Investigations on size dependent phase stability and transformations in isolated nanoparticles have gained momentum in recent times. Size dependent phase stability generates size specific particle microstructure which consequently yields size specific functionality. One important prerequisite for conducting studies on nanoparticles is their synthesis. A substantial amount of research effort has therefore been focused on devising methodologies for synthesizing nanoparticles with controlled shapes and sizes. The present thesis deals with both these two aspects: (a) synthesis of nanoparticles and (b) phase transformations in nanoparticles. The system chosen in this study is AuCu intermetallic nanoparticles. The choice of AuCu nanoparticle was due to the fact that the literature contains abundance of structural and thermodynamic data on Au–Cu system which makes it a model system for investigating size dependence of phase transformations. With respect to synthesis, the present thesis provides methodologies for synthesizing alloyed Au–Cu nanoparticles of different sizes, Au–Cu nano-chain network structures and uniform Au–Cu2S hybrid nanoparticles. For every type, results are obtained from a detailed investigation of their formation mechanisms which are also presented in the thesis. With respect to phase transformation, the thesis presents results on the size dependence of fcc to L10 transformation onset in Au–Cu nanoparticles under isothermal annealing conditions. The present thesis is divided into eight chapters. A summary of results and key conclusions of work presented in each chapter are as follows. The ‘introduction’ chapter (chapter I) describes the organization of the thesis. Chapter II (literature study) presents a review of the research work reported in the literature on the various methodologies used for synthesizing Au–Cu based nanoparticles of different shapes and sizes and on ordering transformation in AuCu nanoparticles. The chapter also presents a brief discussion on the reaction variables that control the process of nucleation and growth of the nanoparticles in solution. Chapter III titled ‘experimental details and instrumentation’ describes the synthesis procedures that were used for producing various nanoparticles in the present work. The chapter also briefly describes the various characterization techniques that were used to investigate the nanoparticles. The fourth chapter titled ‘synthesis and mechanistic study of different sizes of AuCu nanoparticles’ provides two different methodologies for synthesis, referred as ‘two-stage process’ and ‘two-step process’ that have been used for producing alloyed AuCu nanoparticles of different sizes (5, 7, 10, 14, 17, 25 nm). The ‘two-stage’ process involved sequential reduction of Au and Cu precursors in a one pot synthesis process. Whereas, the ‘two-step’ process involved a two-pot synthesis in which separately synthesized Au nanoparticles were coated with Cu to generate alloyed AuCu nanoparticles. In the two-stage synthesis process it was observed that by changing the total surfactant-to-metal precursor molar ratio, sizes of the alloyed AuCu nanoparticles can be varied. ‘Total surfactants’ here include equal molar amounts of oleic acid and oleylamine surfactants. Interestingly, it was observed that there exists a limitation with respect to the minimum nanoparticle size that can be achieved by using the two-stage process. The minimum AuCu nanoparticle size achieved using the two-stage synthesis process was 14 nm. Mechanism of formation of AuCu nanoparticles in the two-stage synthesis process was investigated to find out the reason for this size limitation and also to determine how the synthesis process can be engineered to synthesize alloyed AuCu nanoparticles with smaller (<14nm) sizes. Studies to evaluate mechanism of synthesis were conducted by investigating phase and size of nanoparticles present in the reaction mixture extracted at various stages of the synthesis process. Their studies revealed that (a) the nanoparticle formation mechanism in the two-stage synthesis process involves initial formation of Au nanoparticles followed by a heterogeneous nucleation and diffusion of Cu atoms into these Au rich seeds to form Au–Cu intermetallic nanoparticles and (b) by increasing the relative molar amount of the oleylamine surfactant, size of the initial Au seed nanoparticles can be further reduced from the minimum size that can be achieved in the case when equal molar amounts of oleylamine and oleic acid surfactants are used. The information obtained from the mechanistic study was then utilized to design the two-step synthesis process. In the two-step process, Au nanoparticles were synthesized in a reaction mixture containing only the oleylamine surfactant. Use of only oleylamine resulted in production of pure Au nanoparticles with sizes that were well below 10 nm. These Au nanoparticles were washed and dispersed in a solution containing Cu precursor. Introduction of a reducing agent into this reaction mixture led to the heterogeneous nucleation of Cu onto the Au seed particles and their subsequent diffusion into them to form alloyed AuCu nanoparticles with sizes of ~5, 7 and 10 nm. The study present in this chapter essentially signified that the surfactants used in the reaction mixture not only prevent nanoparticles from agglomerating in the final dispersion but also control their nucleation and growth and therefore can be used as a tool to tune nanoparticle sizes. The fifth chapter titled ‘size dependent onset of FCC-to-L10 transformations in AuCu alloy nanoparticles’ illustrates the effect of AuCu nanoparticle size on the onset of ordering under isothermal annealing conditions. Nanoparticles in this study were annealed in-situ in a transmission electron microscope. Samples were prepared by drop drying a highly dilute dispersion of as-synthesized nanoparticles onto an electron transparent TEM grid. Nanoparticles sitting on the TEM grid were well separated from each other to minimize particle sintering during the annealing operation. It was however observed that during the isothermal annealing, particle coarsening due to atomic diffusion was appreciable for 5 nm particles but negligible for 7 and 10 nm particles. Therefore for this study only 7 nm and 10 nm sized particles were considered. Onset of ordering was determined from the time when first sign of the diffraction spot, corresponding to the ordered phase, appears in the selected area electron diffraction pattern from a region containing large number of AuCu nanoparticles. Through a series of isothermal experiments it was observed that the time for onset of ordering increased with decrease in size of the nanoparticles. It is speculated that the delay in onset of ordering may be due to the fact that with a decrease in nanoparticle size the probability of a nanoparticle containing a fluctuation that shall generate a thermodynamically stable nuclei of the ordered phase decreases. A sharp interface between the ordered and the disordered phase inside the particle was also observed which suggested that the ordering transformation in as-synthesized fcc AuCu nanoparticles is a first order transformation. The sixth chapter titled ‘synthesis and characterization of Au1-xCux–Cu2S hybrid nanostructures: morphology control by reaction engineering’ provides a modified polyol method based synthesis strategy for producing uniform Au–Cu2S hybrid nanoparticles. Detailed compositional and structural characterization revealed that the hybrid nanoparticles are composed of cube shaped Au-rich, Au–Cu solid solution phase and hemispherical shaped Cu2S phase. Interestingly, the hemispherical Cu2S phase was attached to only one facet of the cube shaped phase. A study on the formation mechanism of hybrid nanoparticles was also conducted by characterizing specimens extracted from the reaction mixture at different stages of the synthesis process. The study revealed that the mechanism of formation of hybrid nanoparticles involved initial formation of isolated cube shaped pure Au nanoparticles and Cu–thiolate complex with a sheet morphology. With increase in time at 180°C, the Cu–thiolate complex decomposed and one part of the Cu atoms that were produced from the decomposition were utilized in forming the spherical Cu2S and other part diffused into the Au nanoparticles to form Au–Cu solid solution phase. The chapter also presents a study on the effect of dodecanethiol (DDT) on achieving the hemisphere-on-cube hybrid morphology. In this study it is illustrated that an optimum concentration of dodecanethiol is required both for achieving size and morphological uniformity of the participating phases and for their attachment to form a hybrid nanoparticle. The seventh chapter titled ‘synthesis of Au–Cu nano-chains network and effect of temperature on morphological evolution’ provides methodology for synthesizing fcc Au– Cu nano-chain network structures using polyvinylprrolidone (PVP) surfactant. It was observed that with increase in the molar amount of PVP in the reaction mixture, morphology of the as-synthesized product gradually changed from isolated nanoparticles to branched nano-chain like. The nano-chains contained twins which indicated an absence of continuous growth and possibility of growth by oriented attachment of initially formed Au–Cu nanoparticles. Both in-situ and ex-situ annealing of the nano-chains led to their decomposition into isolated nanoparticles of varying sizes. Annealing also caused fcc-to¬L10 phase transformation. Investigation of the wave length of perturbation leading to breaking of a nano-chain into particles indicated that the surface energy anisotropy affects the splitting of nano-chain network structure into nano-sized particles. The thesis ends with a last chapter where we have presented possible future extension of current work.

Nanoscale-computing fabrics based on novel materials such as semiconductor nanowires, carbon nanotubes, graphene, etc. have been proposed in recent years. These fabrics employ unconventional manufacturing techniques like Nano-imprint lithography or Super-lattice Nanowire Pattern Transfer to produce ultra-dense nano-structures. However, one key challenge that has received limited attention is the interfacing of unconventional/self-assembly based approaches with conventional CMOS manufacturing to build integrated systems. We propose a novel nanofabric approach that mixes unconventional nanomanufacturing with CMOS manufacturing flow and design rules to build a reliable nanowire-CMOS 3-D integrated fabric called N3ASICs with no new manufacturing constraints. In N3ASICs active devices are formed on a dense semiconductor nanowire array and standard area distributed pins/vias, metal interconnects route signals in 3D. The proposed N3ASICs fabric is fully described and thoroughly evaluated at all design levels. Novel nanowire based devices are envisioned and characterized based on 3D physics modeling. Overall N3ASICs fabric design, associated circuits, interconnection approach, and a layer-by-layer assembly sequence for the fabric are introduced. System level metrics such as power, performance, and density for a nanoprocessor design built using N3ASICs were evaluated and compared against a functionally equivalent CMOS design. We show that the N3ASICs version of the processor is 3X denser and 5X more power efficient for a comparable performance than the 16-nm scaled CMOS version without any new/unknown-manufacturing requirement. Systematic yield implications due to mask overlay misalignment have been evaluated. A partitioning approach to build complex circuits has been studied.