Palladium-catalyzed carbon-carbon cross-coupling reactions have emerged a broadly useful, selective and widely applicable method to synthesize pharmaceutical active ingredients. As currently practiced in the pharmaceutical industry, homogeneous Pd catalysts are typically used in cross-coupling reactions. The rational development of heterogeneous catalysts for cross-coupling reactions is critical for overcoming the major drawbacks of homogeneous catalysis including difficulties in the separation, purification, and quality control process in drug production. In order to apply heterogeneous catalysis to flow reactors that may overcome this limitation, the catalyst must be strongly bound to a support, highly stable with respect to leaching, and highly active. While the primary role of supports in catalysis has been to anchor metal particles to prevent sintering and leaching, supports can also activate catalytic processes. In this study, by using a xi combined theoretical and experimental method, we probed the effect of graphene as support in the complex reaction cycle of Suzuki reactions. The density functional theory study provides a fundamental understanding of how a graphene support strongly binds the Pd nanoparticles and act as both an efficient charge donor and acceptor in oxidation and reduction reaction steps. Theoretical investigations prove that the Pd-graphene interaction promotes electron flow between the metal cluster and the defected graphene to reduce reaction barrier. The ability for graphene to both accept and donate charge makes graphene an unusually suitable support for multi-step catalytic processes that involve both oxidation and reduction steps. The computer-aided catalyst design with the atomic precise accuracy demonstrates the Pd/graphene catalyst can be further optimized and the first-row transition metal nanoparticles have great potential to replace Pd to catalyze the Suzuki reaction. The corresponding experimental study shows that the method to immobilize the Pd nanoparticles on the graphene is crucial to increasing the reactivity and stability of the resulted catalyst. A comparison of the activation energy and turn over frequency for a series of supported and homogeneous catalysts indicates that exposing palladium-graphene to defect inducing microwave radiation results in dramatically lower activation energies and higher turnover frequencies. Furthermore, the heterogeneity tests demonstrate the Suzuki reactions are carried out on the surface of the immobilized Pd nanoparticle agreeing with the theoretical results. A method to engineer the 2-D graphene support to a 3-D structure to minimize the re-stacking and agglomeration of the graphene lattice will also be introduced in this study.

Two-dimensional materials such as graphene, boron nitride and transition metal dichalcogenides have attracted significant research interest due to their unique optoelectronic properties. Transition metal dichalcogenides (TMDCs) are a family of two-dimensional semiconductors which exhibit strong light-matter interaction and show great promise for applications ranging from more efficient LEDs to quantum computing. One of the most intriguing qualities of TMDCs is their ability to be stacked on top of one another to tailor devices with specific properties and exploit interlayer phenomena to develop new characteristics. One such interlayer interaction is the generation of charge transfer excitons which span the interface between two different TMDC monolayers. This work aims to study the intrinsic optical properties of charge transfer excitons in TMDC heterostructures. We must first start by investigating methods to protect and isolate our sample of interest from its chemical and electrostatic environment. We demonstrate that near intrinsic photoluminescence (PL) linewidth and exciton emission homogeneity from monolayer TMDCs can be achieved using a combination of BN encapsulation and passivation of substrate hydroxyl groups. Next, we develop clean stacking techniques and incorporate low defect density source crystals to maintain intrinsic properties and ensure a sufficiently high quality heterostructure interface to study characteristics of charge transfer excitons in 2D TDMCs. Strong photoluminescence emission from charge transfer excitons is realized and is shown to persist to room temperature. Charge transfer exciton lifetime is measured to be two orders of magnitude longer than previously reported. Using these high quality heterostructures, we study the behavior of charge transfer excitons under high excitation density. We observe the dissociation of charge transfer excitons into spatially separated electron-hole plasmas under optical excitation. We then probe properties of charge transfer exciton emission enhancement due resonant coupling to surface plasmon modes of gold nanorods.

Respiratory Syncytial Virus (RSV) is a potentially life-threatening respiratory pathogen that infects approximately 64 million children and immunocompromised adults globally per year. Currently, there is a need for prophylactic and therapeutic approaches effective against primary and secondary RSV infections. This project focuses on the development of a simple, smart, and scalable anti-RSV nanotherapeutic that combines novel cellular antiviral defense mechanisms targeting the inhibition of viral fusion and replication. An ICAM-1 targeted liposomal nanocarrier will be synthesized and coated with a layer of chitosan containing the anti-fusion HR2-D peptide as an extracellular defense mechanism. Additionally, chitosan complexed to dual expressing short hairpin RNA (shRNA) recombinant plasmids will be encapsulated within the nanocarrier, and provide an intracellular defense mechanism that will interfere with the expression of the NS1 and P proteins. In combination, both defense mechanisms are expected to induce a synergistic anti-RSV effect that will surpass those of conventional therapeutics. Through this research, the NS1 and P containing plasmid (pSH-NS1-P) was cloned, and the nanotherapeutic was successfully synthesized. Based on the acquired results, pSH-NS1-P was shown to express anti-RSV effects, and it was also concluded that both inserts were producing active shRNA. Additionally, the anti-RSV efficiency of HR2-D was confirmed. Overall, this research will lead to development of a dual-mechanistic anti-viral nanotherapeutic.

The discovery of ferroelectricity at the nanoscale has incited a lot of interest in perovskite ferroelectrics not only for their potential in device application but also for their potential to expand fundamental understanding of complex phenomena at very small size scales. Unfortunately, not much is known about the dynamics of ferroelectrics at this scale. Many of the widely held theories for ferroelectric materials are based on bulk dynamics which break down when applied to smaller scales. In an effort to increase understanding of nanoscale ferroelectric materials we use atomistic resolution computational simulations to investigate the dynamics of polar perovskites. Within the framework of a well validated effective Hamiltonian model we are able to accurately predict many of the properties of ferroelectric materials at the nanoscale including the response of the soft mode to mechanical boundary conditions and the polarization reversal dynamics of ferroelectric nanowires. Given that the focus of our study is the dynamics of ferroelectric perovskites we begin by developing an effective Hamiltonian based model that could simultaneously describe both static and dynamic properties of such materials. Our study reveals that for ferroelectric perovskites that undergo a sequence of phase transitions, such as BaTiO3. for example, the minimal parameter effective Hamiltonian model is unable to reproduce both static and dynamical properties simultaneously. Nevertheless we developed two sets of parameters that accurately describes the static properties and dynamic properties of BaTiO3 independently. By creating a tool that accurately models the dynamical properties of perovskite ferroelectrics we are able to investigate the frequencies of the soft modes in the perovskite crystal. The lowest energy transverse optical soft modes in perovskite ferroelectrics are known to be cause of the ferroelectric phase transition in these materials and affect a number of electrical properties. The performance of a ferroelectric device is therefore directly influenced by the dynamics of the soft mode. Interestingly, however, little study has been done on the effect of mechanical boundary conditions on the soft modes of perovskites. Understanding the effect of mechanical forces on the soft modes is critical to device applications as complicated growth structures often are the cause of pressures, stresses and strains. Using classical molecular dynamics we study the effect of hydrostatic pressure, uniaxial stress, biaxial stress and biaxial strain on the soft modes of the ferroelectric PbTiO3. The results of this study indicate the existence of Curie-Weiss laws for not only hydrostatic pressure, which is well known, but also for uniaxial stress, biaxial stress and biaxial strain. The mode frequencies are also seen to respond very differently to these mechanical forces and lead to a more complete picture of the behavior of nanoscale ferroelectrics. One nanoscale geometry of perovskite ferroelectrics is the pseudo one-dimensional nanowire. These structures have very unique properties that are highly attractive for use as interconnects, nanoscale sensors or more directly in computer memory devices. Perovskite nanowires have only recently been synthesized and the techniques are not well developed. While progress has been made towards consistently fabricating uniform, high quality nanowires experimental investigation of their properties is prohibitively difficult. Of immediate interest is the polarization reversal dynamics of ferroelectric nanowires. The reading and writing of bits of information stored in a wire's polarization state is done by switching the polarization. Again using classical molecular dynamics we study the polarization reversal dynamics in ferroelectric nanowires made of Pb(Ti1-xZrx)O3 disordered alloy. We find that there are two competing mechanisms for polarization reversal and that the interplay of these mechanisms is dependent on electric field strength. The dynamics in nanowires also sheds light on long standing theories about polarization reversal mechanisms in thin film and bulk geometries.

Hydrophilic silicon and germanium quantum dots were synthesized by a "bottom-up" method utilizing micelles to control particle size. Liquid phase deposition of silica on these quantum dots was successful with and without DTAB (dodecyltrimethylammonium bromide) as a surfactant to yield uniform spheres. Coating the quantum dots in the presence of DTAB allowed for better size control. The silica coated quantum dots were then arrayed in three dimensions using a vertical deposition technique on quartz slides or ITO glass. UV-vis absorbance, AFM, SEM, and TEM images were used to analyze the particles at every stage. The photoconductivity of the arrays was tested, and the cells were found to be conductive in areas.

Here, we present a novel approach to visualize propagating surface plasmon polaritons through plasmon-exciton interactions between single gold nanowires and a thin film of a fluorescent polymer. A plasmon polariton was launched by exciting one end of a single gold nanowire with a 532 nm laser. The local near-field of the propagating plasmon modes caused bleaching of the polymer emission. The degree of photobleaching along the nanowire could be correlated with the propagation distance of the surface plasmon polaritons. Using this method of bleach-imaged plasmon propagation (BIIPP), we determined a plasmon propagation distance of 1.8 ± 0.4 μm at 532 nm for chemically grown gold nanowires. Our results are supported by finite difference time domain electromagnetic simulations.

In this thesis an in depth analysis of nanoparticle synthesis utilizing carbon monoxide as a reducing agent is presented. Synthesized nanoparticle mono and polydispersity was examined via particle distribution profiles, statistical, and spectral analysis and compared against other reduction methods. The size and monodispersity of the gold nanoparticles produced with carbon monoxide were tunable by altering the concentration of HAuCl 4 and gas injection flow rates. The carbon monoxide based reduction method offered excellent tunability over a broad range of sizes while maintaining a high level of monodispersity when compared to the other reduction methods. The mechanisms involved in the size dependent optical response of the synthesized nanoparticles were identified. It was also found that speciation of aqueous HAuCl 4 influences the size, structure, and properties of Au colloids. Ensemble extinction spectra and TEM images provide clear evidence that CO reduction offers a high level of tunability compared to other synthesis methods.

Nanocatalysis, catalysis using particles on the nanoscale, is an emerging field that has tremendous potential. Nanoparticles have different properties than bulk material and can be used in different roles. Macro sized precious metals, for example, are inert, but nanoparticles of them are becoming more widely used as catalysts. Understanding the manner in which these particles work is vital to improving their efficacy. This thesis focuses on two aspects of nanocatalysis. Chapter 1 begins with a brief introduction into nanotechnology and some of the areas in which nanoparticles are different than bulk particles. It then proceeds into an overview of catalysis and nanocatalysis more specifically. Focus is brought to the definitions of the different types of catalysis and how those definitions differ when applied to nanoparticles. Chapter 2 is in finding an inert support structure to more easily assist in recycling the nanoparticles. Polystyrene microspheres were studied and found to prevent platinum nanoparticles from aggregating in solution and possibly aid in recycling of the nanoparticles. These nanoparticles were used in catalysis, aiding in the reduction of 4-nitrophenol in the presence of sodium borohydride. While the rate decreased by a factor of ~ 7 when using the polystyrene, the activation energy of the reaction was unaltered, thus confirming the inactivity of the polystyrene in the reaction. In Chapter 3, nanocatalysis was studied by examining bimetallic hollow nanoparticles with specific attention to the effect of altering the ratios of the two metals. Ten different bimetallic nanocages were tested in an electron transfer reaction between hexacyanoferrate and thiosulfate. Five PtAg nanocages and five PdAg with varying metal ratios were prepared and studied. It was found that while silver cubes immediately precipitate out of solution when combined with thiosulfate, a small amount of either platinum or palladium allows the particles to remain in solution and function as a substantially more effective catalyst. However, as additional Pt was added the activation energy increased. To obtain a better understanding of the catalysis using bimetallic cages, the evolution of these cages was studied as the 2nd metal was added. Initially the particle edge length increased and then slowly decreased back to the size of the template cubes. The increase in edge length suggests of addition of material to the nanoparticles. This indicated the 2nd metal is on the outside of the cage, which was confirmed using UV-Vis spectroscopy and EDS mapping. By understanding how these bimetallic particles evolve, we may be able to manipulate these synthetic methods to more precisely design nanoparticles for catalysis.

A systematic investigation into the growth of one-dimensional nanostructures of select II-VI compounds with the wurtzite crystal structure. Two process parameters are systematically altered to observe how each affects deposition. The results of which give a further understanding into the formation of one nanostructure over another, as well as experimental parameters for optimizing the growth of particular CdSe nanomaterials. A statistical analysis is conducted on the experimental data to quantitatively determine the variability and robustness of the experimental setup and process. The information complied from this extensive study will yield a more complete understanding of the experimental setup and how improvements can be made to reduce variability, increase yield, and gain insight into the mechanisms controlling this class of materials.

Thesis (Ph. D.)--UCLA, 2009. / Vita. Description based on print version record. Includes bibliographical references (leaves 347-368).