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<p> A large focus of this thesis was developing the experimental procedures involved in imaging <i>VO₂</i> during the heating process. In order to study light interactions between an induced dipole and a sample surface to collect various data on its topography, amplitude and phase. Data is collected using a near-eld microscope (s-SNOM) and analyzed using various software that, normalize, lter and display the data in false color image. Specically, research behind this thesis, focuses on the phase transition of Vanadium Dioxide (<i>VO₂</i>) as it goes from an insulating to fully metallic phase. Using a wavelength of &lambda; = 10:7<i>&mu;m</i> to image the resonant behavior of the sample, the nucleation of <i>VO₂</i> was imaged as the temperature increased.</p>

<p> The development of cost-effective materials for effective utilization of solar energy is a major challenge for solving the energy problems that face the world. This thesis work relates to the development of mesoporous materials for solar energy applications in the areas of photocatalytic water splitting and the generation of electricity. Mesoporous materials were employed throughout the studies because of their favorable physico-chemical properties such as high surface areas and large porosities. The first project was related to the use of a cubic periodic mesoporous material, MCM-48. The studies showed that chromium loading directly affected the phase of mesoporous silica formed. Furthermore, within the cubic MCM-48 structure, the loading of polychromate species determined the concentration of solar hydrogen produced. In an effort to determine the potential of mesoporous materials, titanium dioxide was prepared using the Evaporation-Induced Self-Assembly (EISA) synthetic method. The aging period directly determined the amount of various phases of titanium dioxide. This method was extended for the preparation of cobalt doped titanium dioxide for solar simulated hydrogen evolution. In another study, metal doped systems were synthesized using the EISA procedure and rhodamine B (RhB) dye sensitized and metal doped titania mesoporous materials were evaluated for visible light hydrogen evolution. The final study employed various mesoporous titanium dioxide materials for N719 dye sensitized solar cell (DSSC) materials for photovoltaic applications. The materials were extensively characterized using powder X-ray diffraction (XRD), nitrogen physisorption, diffuse reflectance spectroscopy (DRS), UV-Vis spectroscopy, Fourier-Transform-Infrared Spectroscopy (FT-IR), Raman spectroscopy, chemisorption, photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). In addition, photoelectrochemical measurements were completed using current-voltage (I-V) curves, external quantum efficiency (EQE) curves, electrochemical impedance spectroscopy (EIS), and transient spectroscopy. The thesis work presented provides a better understanding of the role of mesoporous materials for solar hydrogen and solar electricity production.</p>

<p>Multifunctional polymer nanocomposites (PNCs) are attractive for the design of tunable RF and microwave components such as flexible electronics, attenuators, and antennas due to cost-effectiveness and durability of polymeric matrices. In this work, three separate PNCs were synthesized. Magnetite (Fe₃O₄) and cobalt ferrite (CFO) nanoparticles, synthesized by thermal decomposition, were used as PNC fillers. Polymers used in this work were a commercial polymer provided by the Rogers Corporation (RP) and polyvinylidene fluoride (PVDF). PNCs in this thesis consist of Fe₃O₄ in RP, CFO in RP, and Fe₃O₄ in PVDF. Characterization techniques for determining morphology of the nanoparticles, and their resulting PNCs, include x-ray diffraction, transmission electron microscopy and magnetometry. </p><p> All magnetometry measurements were taken using a Quantum Design Physical Property Measurement System with a superconducting magnet. Temperature and external magnetic field magnetization measurements revealed that all samples exhibit superparamagnetic behavior at room temperature. Blocking temperature, coercivity and reduced remnant magnetization do not vary with concentration. Tunable saturation magnetization, based on nanoparticle loading, was observed across all PNCs, regardless of polymer or nanoparticle choice, indicating that this is an inherent property in all similar PNC materials. </p><p> Tunability studies of the magneto-dielectric PNCs were carried out by adding the PNC to cavity and microstrip linear resonator devices, and passing frequencies of 1&ndash;6 GHz through them in the presence of transverse external magnetic fields of up to 4.5 kOe, provided by an electromagnet. Microwave characteristics were extracted from scattering parameters of the PNCs. In all cases, losses were reduced, quality factor was increased, and tunability of the resonance frequency was demonstrated. Strong magnetic field dependence was observed across all samples measured in this study. </p>

<p> The research presented herein exploits the terminal phosphate group on single stranded DNA molecules for direct immobilization to surfaces utilized in semiconductor device fabrication with the end goal of transistor based DNA sensors. As a demonstration of the feasibility of this immobilization strategy DNA immobilization to a variety of surfaces was evaluated for usefulness in biosensor applications. It was determined that DNA can be directly immobilized to a variety of semiconductor surfaces through the terminal phosphate group. Further, this immobilization allows for the hybridization of the immobilized DNA to complementary target in solution. The immobilization of DNA to hafnium dioxide was particularly of interest due to its use in modern nanoelectronics manufacturing. The interactions between DNA and various forms of hafnium dioxide were thoroughly studied in order to understand and optimize the immobilization of DNA to hafnium dioxide for field effect transistor (FET) based DNA sensors. A secondary immobilization route of DNA to a subset of hafnium dioxide surfaces was identified and we have shown that this mechanism is through the nitrogenous bases of the probe molecule. Finally, a novel FET sensor was designed and developed which incorporated III-V materials and hafnium dioxide. The development of the sensor was carried out with the long term goal of determining if FET DNA sensors would have increased sensitivity if fabricated with: 1) the direct immobilization of probe DNA; 2) hafnium dioxide gate dielectric; and/or 3) III-V FET structure. Here, we demonstrate a proof-of-concept device that incorporates these three features and is capable of detecting DNA in solution, DNA immobilized to the surface, and DNA hybridization events.</p>

<p> This dissertation reports the synthesis and characterization of nanoscale coordination polymers (NCPs) for anticancer drug delivery. Nanoparticles have been explored in order to address the limitations of small molecule chemotherapeutics. NCPs have been investigated as drug delivery vehicles as they can exhibit the same beneficial properties as the bulk metal-organic frameworks as well as interesting characteristics that are unique to nanomaterials. </p><p> Gd-MTX (MTX = methotrexate) NCPs with a MTX loading of 71.6 wt% were synthesized and stabilized by encapsulation within a lipid bilayer containing anisamide (AA), a small molecule that targets sigma receptors which are overexpressed in many cancer tissues. Functionalization with AA allows for targeted delivery and controlled release to cancer cells, as shown by enhanced efficacy against leukemia cells. The NCPs were doped with Ru(bpy)₃²⁺ (bpy = 2,2'-bipyridine), and this formulation was utilized as an optical imaging agent by confocal microscopy. </p><p> NCPs containing the chemotherapeutic pemetrexed (PMX) were synthesized using different binding metals. Zr-based materials could not be stabilized by encapsulation with a lipid bilayer, and Gd-based materials showed that PMX had degraded during synthesis. However, Hf-based NCPs containing 19.7 wt% PMX were stabilized by a lipid coating and showed in vitro efficacy against non-small cell lung cancer (NSCLC) cell lines. Enhanced efficacy was observed for formulations containing AA. </p><p> Additionally, NCP formulations containing the cisplatin prodrug disuccinatocisplatin were prepared; one of these formulations could be stabilized by encapsulation within a lipid layer. Coating with a lipid layer doped with AA rendered this formulation an active targeting agent. The resulting formulation proved more potent than free cisplatin in NSCLC cell lines. Improved NCP uptake was demonstrated by confocal microscopy and competitive binding assays. </p><p> Finally, a Pt(IV) oxaliplatin prodrug was synthesized and incorporated in different NCPs using various binding metals. A moderate drug loading of 44.9 wt% was determined for Zr-based NCPs. This drug loading, along with a diameter less than 200 nm, make these particles promising candidates for further stabilization via lipid encapsulation.</p>

<p> Nanoscopic pores in biological systems &ndash; cells, for example &ndash; are responsible for regulating the transport of ionic and molecular species between physiologically distinct compartments maintained by thin plasma membranes. These biological pores are proteinaceous structures: long, contorted chains of chemical building blocks called amino acids. Protein pores have evolved to span a staggering range of shapes, sizes and chemical properties, each crucial to a pore's unique functionality. </p><p> Protein pores have extremely well-defined jobs. For instance, pores called ion channels only transport ions. Within this family, there are pores designated to selectively transport specific ions, such as sodium channels for sodium, chloride channels for chloride and so on. Further subdivisions exist within each type of ion channel, resulting in a pantheon of specialized proteins pores. </p><p> Specificity and selectivity are bestowed upon a pore through its unique incorporation and arrangement of its amino acids, which in turn have their own unique chemical and physical properties. With hundreds of task-specific pores, deciphering the precise relationship between form and function in these protein channels is a critical, but daunting task. In this thesis, we examine an alternative for probing the fundamental mechanisms responsible for transport on the nanoscale. </p><p> Solid-state membranes offer well-defined structural surrogates to directly address the science underlying pore functionality. Numerous protein pores rely on electronic interactions, size exclusion principles and hydrophobic effects to fulfill their duties, regardless of their amino acid sequence. Substituting an engineered and well-characterized pore, we strive to achieve and, thus, understand the hallmarks of biological pore function: analyte recognition and selective transport. </p><p> While we restrict our study to only two readily available membrane materials &ndash; one a polymer and the other a ceramic &ndash; nanofabrication techniques give us access to a virtually limitless combination of pore shapes and sizes. Exploiting this, we investigate the role of pore geometry in mediating the electrostatic and steric interactions responsible for transport on the nanoscale. Through targeted chemical modifications of our homogenous pores, we easily tailor their surface properties to investigate the role of hydrophobic effects in confined environments. Unbound by the physiological limitations of protein structures (such as sensitivity to electrolyte composition and fragility to external forces), our report concludes with the fusion of fabrication and modification considerations to design robust components for nanofluidic circuitry and nanoscopic biosensors.</p>

<p> Magnetic nanostructures have widespread applications in many areas of physics and engineering, and nanosphere lithography has recently emerged as promising tool for the fabrication of such nanostructures. The goal of this research is to explore the magnetic properties of a thin film of ferromagnetic material deposited onto a hexagonally close-packed monolayer array of polystyrene nanospheres, and how they differ from the magnetic properties of a typical flat thin film. The first portion of this research focuses on determining the optimum conditions for depositing a monolayer of nanospheres onto chemically pretreated silicon substrates (via drop-coating) and the subsequent characterization of the deposited nanosphere layer with scanning electron microscopy. Single layers of permalloy (Ni80Fe20) are then deposited on top of the nanosphere array via DC magnetron sputtering, resulting in a thin film array of magnetic nanocaps. The coercivities of the thin films are measured using a home-built magneto-optical Kerr effect (MOKE) system in longitudinal arrangement. MOKE measurements show that for a single layer of permalloy (Py), the coercivity of a thin film deposited onto an array of nanospheres increases compared to that of a flat thin film. In addition, the coercivity increases as the nanosphere size decreases for the same deposited layer. It is postulated that magnetic exchange decoupling between neighboring nanocaps suppresses the propagation of magnetic domain walls, and this pinning of the domain walls is thought to be the primary source of the increase in coercivity.</p>

<p> Colloidally prepared nanocrystals of transparent conducting oxide (TCO) semiconductors have emerged in the past decade as an exciting new class of plasmonic materials. In recent years, there has been tremendous progress in developing synthetic methods for the growth of these nanocrystals, basic characterization of their properties, and their successful integration into optoelectronic and electrochemical devices. However, many fundamental questions remain about the physics of localized surface plasmon resonance (LSPR) in these materials, and how their optoelectronic properties derive from their underlying structural properties. In particular, the influence of the concentration and distribution of dopant ions and compensating defects on the optoelectronic properties of TCO nanocrystals has seen little investigation. </p><p> Indium tin oxide (ITO) is the most widely studied and commercially deployed TCO. Herein we investigate the role of the distribution of tin dopants on the optoelectronic properties of colloidally prepared ITO nanocrystals. Owing to a high free electron density, ITO nanocrystals display strong LSPR absorption in the near infrared. Depending on the particular organic ligands used, they are soluble in various solvents and can readily be integrated into densely packed nanocrystal films with high conductivities. Using a combination of spectroscopic techniques, modeling and simulation of the optical properties of the nanocrystals using the Drude model, and transport measurements, it is demonstrated herein that the radial distribution of tin dopants has a strong effect on the optoelectronic properties of ITO nanocrystals. </p><p> ITO nanocrystals were synthesized in both surface-segregated and uniformly distributed dopant profiles. Temperature dependent measurements of optical absorbance were first combined with Drude modeling to extract the internal electrical properties of the ITO nanocrystals, demonstrating that they are well-behaved degenerately doped semiconductors displaying finite conductivity at low temperature and room temperature conductivity reduced by one order of magnitude from that of high-quality thin film ITO. </p><p> Synchrotron based x-ray photoelectron spectroscopy (XPS) was then employed to perform detailed depth profiling of the elemental composition of ITO nanocrystals, confirming the degree of dopant surface-segregation. Based on free carrier concentrations extracted from Drude fitting of LSPR absorbance, an inverse correlation was found between surface segregation of tin and overall dopant activation. Furthermore, radial distribution of dopants was found to significantly affect the lineshape and quality factor of the LSPR absorbance. ITO nanocrystals with highly surface segregated dopants displayed symmetric LSPRs with high quality factors, while uniformly doped ITO nanocrystals displayed asymmetric LSPRs with reduced quality factors. These effects are attributed to damping of the plasmon by Coulombic scattering off ionized dopant impurities. </p><p> Finally, the distribution of dopants is also found to influence the conductivity of ITO nanocrystal films. Films made from nanocrystals with a high degree of surface segregation demonstrated one order of magnitude higher conductivity than those based on uniformly doped crystals. However, no evidence was found for differences in the surface electronic structure from one type of crystal to the other based on XPS and the exact mechanism for this difference is still not understood. </p><p> Several future studies to further illuminate the influence of dopant distribution on ITO nanocrystals are suggested. Using synchrotron radiation, detailed photoelectron spectroscopy on clean ITO nanocrystal surfaces, single-nanoparticle optical measurements, and hard x-ray structural studies will all be instructive in elucidating the interaction between oscillating free electrons and defect scattering centers when a plasmon is excited. In addition, measurements of temperature and surface treatment-dependent conductivity with carefully controlled atmosphere and surface chemistry will be needed in order to better understand the transport properties of ITO nanocrystal films. Each of these studies will enable better fundamental knowledge of the plasmonic properties of nanostructures and improve the development of nanocrystal based plasmonic devices.</p>

<p> Studies were performed on two seemingly different topics, molecular thin films on graphite/graphene and metal induced changes in various cuts of silicon (Si) surfaces. However, both projects share the underlying theme of self-assembly. Since nature can rely upon self-assembly at the nano-scale, all that is needed is to discover functional means to create components for integrated circuits as well as electronic and photonic devices. </p><p> Scanning Tunneling Microscopy and Spectroscopy (STM/STS) studies were carried out to characterize the morphology of thin porphyrin films on graphite and the effects of Zn-Phthalocyanine (Zn-Pc) adsorption on the electronic properties of graphene. It was found that the metal atom complex of porphyrin molecules can determine the morphology, intermolecular forces and ability to create thin films on a graphite surface. Zn-Pc adsorption onto graphene shifts the position of the Dirac point with respect to Fermi level which leads to localized p- and n-type doping effects in the graphene substrate. </p><p> STM, STS and Low-Energy Electron Diffraction (LEED) measurements were carried out on iridium (Ir) modified Si(111) and Si(100) surfaces. The Ir-modified Si(111) surface exhibited a &radic;7&times;&radic;7 <i>R </i>19.1&deg; domain formation that was composed of Ir-ring clusters. LEED measurements showed that on Ir-modified Si(100), a <i>p</i>(2&times;2) structure arose after annealing at ~700&deg;C. The proposed model for the Ir-silicide nanowires shows that an Ir atom replaces every other Si dimer along the Si dimer rows of Si(100)-2&times;1.</p>