This research is focused on the synthesis of CNTs using thermal chemical vapor deposition (CVD) at atmospheric pressure with Pd, Ni, and Co as catalysts, and characterization of the CNTs for field emission applications. In this work, a systematic study was performed on the catalyst processing parameters and morphologies of as-grown CNT arrays. By controlling catalyst pretreatment parameters, high-density catalyst nanoparticles with uniform size have been produced. The result indicates that Pd is a more effective catalyst than conventional catalysts such as Co and Ni, and the corresponding CNT cathodes demonstrated comparable field emission behavior (turn-on field of 2.5V/um and field enhancement factor of 7800). <p> Secondly, synthesis of vertically aligned CNT arrays under atmospheric pressure has been achieved by thermal CVD using cobalt (Co) and nickel (Ni) as catalysts. These well-aligned nanotubes demonstrate lower turn-on field (~ 1.2V/um) than randomly oriented CNTs. <p> Finally, an innovative approach has been developed to fabricate CNT/transition-metal-oxide (TMO) nanocomposite thin film for supercapacitor electrodes. Particular effort has been invested into manganese dioxide (MnO2) due to its excellent pseudocapacitance, low cost, non-toxicity and readily availability. This novel approach of using nano-structured CNTs architectures provides a high surface area of attachment for MnO2 nano-particles to maximize the charge efficiency and the power density and to reduce the series resistance. In this newly developed system, the charge transfer between CNTs and MnO2 nanoparticles is very efficient due to the exceptional electronic conductivity of CNTs. The direct growth of CNTs on conductive Si substrate helps to reduce contact resistance and ESR is significantly reduced and power is enhanced. A high capacitance of 30000uF (270F/g) has been observed on CNT/ MnO2 composite electrode which is over 400 times that of MnO2-free CNT sample. And a record-breaking charging/discharging current of 1.92mA, or 17.32 A/g, has been achieved.

Ultra-dispersed Diamond (UDD) is synthetically produced by the detonation of carbon-containing explosives in an oxygen-deficient atmosphere. UDD, comprised of 5-nm diamond particles, is an attractive nanomaterial because of diamonds outstanding thermal, chemical, and mechanical properties. Application of UDD additives in fluid and polymer materials has been limited by the strong tendency for the primary diamond nanoparticles to aggregate into structures with sizes ranging from hundreds of nanometers to microns. In this work, a method to separate the UDD aggregates into primary nanodiamond (ND) nanoparticles is demonstrated. De-aggregation processing techniques are coupled with surface functionalization strategies to disperse ND into fluids and polymeric materials. Nanofluids containing ND exhibit excellent nanoparticle stability and enhanced thermal conductivity. Multiple functionalization strategies are explored to achieve particle dispersion in polar and non-polar solvents as well as to elucidate how different surface functional groups may affect the thermal conductivity enhancement of nanofluid systems. Functionalized ND is incorporated into both thermoplastic and thermosetting polymer matrices for enhancement of mechanical properties. An assortment of surface functionalization strategies is employed to achieve high-quality dispersions and to examine how various interfacial phenomenon can affect macroscopic material properties.

Carbon nanotubes (CNTs) are modeled using the Tersoff-Brenner potential and thermal conductivities were estimated using non-equilibrium molecular dynamics. Thermal conductivity for single-wall carbon nanotubes (SWNTs) and double-wall carbon nanotubes (DWNTs) were studied for lengths from 25 nm to 1 μm. Thermal conductivity increases with length from the inclusion of additional phonon modes. To investigate influences of individual modes on thermal conductivity, DWNTs are used to model vibrational mode confinement in SWNTs. Also, various concentrations of phenyl united atom models and values for the Lennard-Jones parameter σ are used to model functionalization and the influence of bond strength. Thermal conductivity is largely influenced by longitudinal and flexural modes. Due to scattering from phonon-phonon interactions, the combination of the longitudinal and flexural modes results in a lower thermal conductivity than other phonon mode combinations. The influence of suppressing the flexural mode is also observed in the thermal conductivity behavior of functionalized CNTs. When using the united atom model, larger percentages of functionalization result in decreasing flexural modes and, consequently, higher thermal conductivity. Similarly, smaller values of σ, which indicate a stronger bond, showed better thermal conductivity. Overall the best performance resulted from functionalized DWNTs, which have the additional wall to transport energy.

Properties such as high electrical conductivity; chemical and electrochemical stability over a wide range of conditions; rapid electron transfer kinetics for different redox systems; and reproducible electrical, microstructural and chemical properties are essential pre-requisites for electrochemical electrodes. Nanodiamond is one such electrode material which has been shown to be suitable for electroanalytical applications. In this dissertation, MPECVD (Microwave Plasma Enhanced Chemical Vapor Deposition) process and conventional silicon microfabrication technology has been used for synthesis and fabrication of nanodiamond thin-film macroelectrodes and ultramicroelectrode arrays (UMEAs) with different geometries- pyramidal, planar and columnar. This work combines the excellent material properties of nanodiamond with the benefits of using UMEAs- higher analyte flux density, reduced ohmic losses and higher temporal resolution. Scanning electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy were used for material characterization. Electrochemical performance was analyzed using ferri/ferrocyanide redox couple and essential bio-analytes such as Dopamine, Ascorbic Acid (AA) and Uric Acid (UA) in phosphate buffered saline (PBS). To simulate true physiological conditions, detection and quantification of dopamine in presence of interferants such as AA and UA was also examined, in-vitro. In addition, effects of the input gas mixture, i.e., hydrogen, methane and nitrogen, on nanodiamond macroelectrode properties were evaluated and optimized. Increase in nitrogen gas flow produced distinct changes in the nanodiamond microstructure and electrochemical response. The fabrication processes and electroanalytical performance, under steady state conditions, of the UMEAs with different geometries were compared to identify their respective drawbacks and new fabrication processes were developed to overcome them in order to consistently produce more reliable bio-sensors. The sensitivity of the UMEAs varied inversely with their dimensions. Neurotransmitter concentrations vary at sub-second time-scale and can only be monitored and quantified by using an electrode with high temporal resolution and fast electron transfer kinetics. Hence, background subtracted fast scan cyclic voltammetry for Dopamine detection using planar nanodiamond UMEA was implemented. All the results from electrochemical characterization were achieved without any surface functionalization and/or modification.

In the ongoing struggle to resolve our current energy crisis, many agencies and researchers have spearheaded the application of direct energy conversion materials, such as thermoelectric and thermionic devices for waste heat recovery and power generation. However, the current state-of-the-art direct energy conversion materials are plagued by extremely low efficiencies that prevent a widespread solution. Recent effort to improve the efficiencies of these direct energy conversion materials has demonstrated a drastic increase through the inclusion of nanoscale features. With new advances in nanoscale materials comes the need for new models that can capture the underlying physics. Thus, this research has developed a necessary tool and a unique modeling approach (based on NEGF quantum simulations) that couples both the electrical and thermal response of nanoscale transport accounting for both the dissipative interactions of electron-phonon and phonon-phonon scattering. Through the aid of high performance computing techniques, the models developed in this research are able to explore the large design space of nano-structured thermoelectrics and thermionic materials. The models allow computational predictions to drive innovation for new, optimized, direct energy conversion materials. A specific device innovation that has come from this research is the development of variably spaced superlattice (VSSL) devices, which are the next progression in band engineering thermoelectric materials. Computational findings of VSSL materials predict a seven times increase in ZT at room temperature when compared to traditional superlattice devices. Other thermoelectric materials studied include nanocrystalline composites (NCC) which were predicted to outperform equivalent superlattice structures as a results of decreases electron filtering. In addition to thermoelectric materials, this research has developed a quantum modeling technique to investigate and optimize nano-tipped thermionic and thermal-field devices. Results have provided incite into the applicability of Richardson's theory in characterizing the emission from wide-band gap thermionic materials. Ultimately, the quantum models developed in this research are a necessary tool for understanding nanoscale transport and innovating new nanostructured materials.

Colloidal nanoparticles in an assortment of shapes (e.g., spherical, rod-like, tube-like, sheet-like) have been the focus of far-reaching research pursuits due to their attractive material-dependent and size-dependent electronic, optical, and magnetic properties. One approach to deploy these materials in devices is to fabricate them into multilayered thin films. Fabricating thin films over macroscopic dimensions requires controlling the assembly behavior of a very large number of nanoparticles. In addition to understanding the assembly behavior, we were interested in whether this many-particle assembly could exist as a free-standing object. To determine the stability of the nanoparticle assemblies, we used the principles of DLVO theory to calculate the potential energy of the interaction between two particles. <P> Nanoparticle films were assembled using electrophoretic deposition. To fabricate free-standing films, we proposed a technique in which particles would be deposited atop a thin sacrificial layer. This technique of sacrificial layer electrophoretic deposition (SLED) was demonstrated by producing macroscopic, free-standing films of hexane-dispersed CdSe and iron oxide nanoparticles and of water-dispersed sheets of exfoliated graphene oxide (eGO). By tuning the pH of the aqueous eGO suspensions, we also demonstrated the fabrication of films with different microstructures, which exhibited both hydrophilic and hydrophobic surface wetting properties.

The materials, optical and electrical properties of transparent conducting tin oxide-based thin films are investigated, with particular emphasis on their application to photovoltaics. Thin films of transparent conducting oxides are used as transparent electrodes in all thin film solar cells. However, the films contribute optical and electrical losses of their own. In this work, the fundamental aspects of increasing permittivity in transparent conductors are investigated by adding ZrO2 (a high permittivity material) to SnO2 films (a transparent conductor). The experimental results are explained by expectations from the Drude model for free electrons. Details and results for the film synthesis by chemical vapor deposition are explored. Results for decreased optical absorptance are presented together with evidence for increased permittivity. Additionally, experiments indicate that increasing permittivity also has the benefit of increasing carrier mobility when in the limit of ionized impurity scattering.

A bottom up approach to functionalizing high quality porous silicon optical structures with nucleic acid bioreceptors is presented in this dissertation. The solid-phase synthesis method using phosphoramidite protected nucleic acids is applied for the first time in porous silicon waveguides to achieve DNA attachment within the pores. Biomolecule attachment is monitored by coupling light into the waveguide to probe changes in the effective refractive index of the optical structure. We show herein that the in situ DNA synthesis method achieves a higher surface coverage with bioreceptors than the traditional infiltration of pre-synthesized DNA strands into mesoporous silicon structures. With the in situ approach, DNA conformation, flexibility, and length play little role in DNA bioreceptor density within the substrate. The increased sensitivity resulting from in situ preparation of DNA functionalized porous silicon waveguide sensors has been demonstrated for 8-, 16-, and 24mer DNA oligo receptors and complementary nucleic acid targets, with the lowest detection limits in the nanomolar range. Functionalization of the porous silicon with a two-component silane monolayer, only one component of which is active for in situ DNA synthesis, allows for precise control of the synthesized DNA surface density. Tuning of the DNA density in the pores enables improved biosensor sensitivity by maximizing the number of bioreceptors that can capture target molecules without being impeded by steric crowding. Using synthesized DNA oligos in porous silicon as aptamers, highly selective detection of small molecule targets other than complementary DNA molecules is possible. This work demonstrates for the first time the optical measurement of DNA aptamer-based capture of small molecules in a porous silicon waveguide. Selective detection of the small molecules adenosine and ochratoxin A is described, providing evidence that DNA aptamers retain their functionality within the mesoporous substrate. This first demonstration of DNA aptamer-based sensing within porous silicon may be expanded to other small molecule targets of interest, combining the high selectivity of aptamer detection schemes with the sensitivity and filtering capabilities afforded by porous silicon waveguide sensors.

Congenital heart disease (CHD) is the most common type of birth defect affecting eight out of every 1,000 newborns, causing more deaths in the first year of life than any other birth defect. A significant fraction of CHD is associated with abnormal valve structure and function. A detailed understanding of the early signaling events that regulate and guide cardiac valve formation is required to identify new therapeutic targets. Here, I focus on the role of Type III Transforming Growth Factor β Receptor (TGFβR3) in Endocardial epithelial to mesenchymal transformation (EMT), a critical step in valvular development. Using an in vitro assay of endocardial EMT I used small molecule inhibitors to establish that ALK2 and ALK3 are both required for endocardial EMT. Specifically, I demonstrated that ALK2 and ALK3 are downstream of TGFβR3. Finally, I used small molecule inhibitors of the NF-κB pathway to implicate this signaling system in endocardial EMT. These studies identify and clarify the role of specific pathways endocardial EMT which furthers our understanding of TGFβR3 signaling and early valve formation.

Studying population isolates with large, complex pedigrees has many advantages for discovering genetic susceptibility loci; however, statistical analyses can be computationally challenging. Allelic association tests need to be corrected for relatedness among study participants, and linkage analyses require subdividing and simplifying the pedigree structures. In this thesis work I simulated SNP (single nucleotide polymorphism) data in complex pedigree structures based on an Amish pedigree. I evaluated type 1 error rates and power when performing two-point and multipoint linkage after dividing the pedigree into subpedigrees. I also ran MQLS (modified likelihood score test) to test for allelic association in the subpedigrees and in the unified pedigree.