We have investigated the conductance, g, of 1,4-butanedithiol linked Au nanoparticle films as a function of temperature, T, bias potential, V, and applied magnetic field, B. An interesting temperature dependence is observed for non-metallic films with thicknesses just below a critical film thickness: g ~ exp [-(T_0/T)^(1/2)] for 20 K < T < 300 K. We show that this temperature dependence is incompatible with an Efros-Shklovskii "variable range hopping" model, since "hopping distances" are too large to be consistent with tunneling processes, and tend to scale with size of super-clusters of molecularly-linked nanoparticles. We propose a "quasilocalized hopping" model based on competition between single-electron charging of super-clusters and electron backscattering within super-clusters to explain the observed temperature dependence. Various electron scattering time scales are extracted from magnetoconductance data using a modified "weak localization" model. Elastic scattering time scales are comparable to those required for an electron to traverse a nanoparticle, while inelastic and spin-orbit scattering time scales are consistent with those found in studies of conventionally-prepared granular Au films. At interfaces between metallic 1,4-butanedithiol-linked Au nanoparticle films and conventional superconductors, we find that g consistently exhibits peaks, as well as oscillations, that depend simultaneously on both V and B. Such peaks and correlated conductance oscillations are predicted by an enhanced Andreev reflection process due to disorder-driven elastic scattering and electron-hole interference in the nanoparticle film. While oscillations have been predicted by a so-called "reflectionless tunneling" model, they have not been observed at other normal-superconductor interfaces. We speculate that oscillations are observable in this system due to synthetically controlled uniformity of elastic scattering length (i.e., nanoparticle diameter) and a reduced number of current-carrying pathways, especially near the interface. Contrary to predictions of existing "reflectionless tunneling" models, we find that the periods of oscillation in B decrease as T increases. This suggests that the area of interfering pathways increases with T. We propose that this increasing area can be attributed to magnetic field penetration into the superconductor. Conductance data agrees remarkably well with known temperature dependence of penetration depth predicted by BCS theory. Our study shows that this additional region of flux must be considered in experimental and theoretical studies of "reflectionless tunneling", and underscores the utility of molecularly-linked nano\-particle films as a platform for studying charge transport.

Applied cancer research is heavily focused on the development of diagnostic tools with high sensitivity and specificity that are able to accurately detect the presence and anatomical location of neoplastic cells, as well as therapeutic strategies that are effective at curing or controlling the disease while being minimally invasive and having negligible side effects. Recently, much effort has been placed on the development of nanoparticles as diagnostic imaging and therapeutic agents, and several of these nanoplatforms have been successfully adopted in both the research and clinical arenas. This thesis describes the development of a nanoparticulate liposome system for use in a number of applications including multimodality imaging with computed tomography (CT) and magnetic resonance (MR), longitudinal vascular imaging, image-based biodistribution assessment, and CT detection of neoplastic and inflammatory lesions. Extensive in vitro and in vivo characterization was performed to determine the physico-chemical properties of the liposome agent, including its size, morphology, stability and agent loading, as well as its pharmacokinetics, biodistribution, tumor targeting and imaging performance. Emphasis was placed on the in vivo CT-based quantification of liposome accumulation and clearance from healthy and tumor tissues in a VX2 carcinoma rabbit model, gaining insight not only on the spatial but also the temporal biodistribution of the agent. The thesis concludes with a report that describes the performance of liposomes and CT imaging to detect and localize tumor and inflammatory lesions as compared to that of 18F-fluorodeoxyglucose (FDG) – positron emission tomography (PET). The outcome of the study suggests that liposome-CT could be employed as a competitive method for whole body image-based disease detection and localization. Overall, this work demonstrated that this liposome agent along with quantitative imaging systems and analysis tools, has the potential to positively impact cancer treatment outcome through improved diagnosis and staging, as well as enable personalization of treatment delivery via target delineation. However, in order to prove clinical benefit, steps must be taken to advance this agent through the regulatory stages and obtain approval for its use in humans. Ultimately, the clinical adoption of this multifunctional agent may offer improvements for disease detection, spatial delineation and therapy guidance.

Research on self-assembling gemini surfactants and other amphiphiles for potential gene delivery applications in research as well as in clinical practice, and as alternatives to viral gene delivery vectors, is beginning to focus more on structureactivity relationships to address the current low gene delivery efficiencies of amphiphiles. Some underlying structureactivity relations are beginning to emerge. But, as a better understanding of the factors that govern the transfection abilities of amphiphile molecules emerges, development of improved non-viral vectors with clinical potential may also emerge.<p> The research conducted for this thesis was aimed at the design, synthesis and in vitro investigation of gemini surfactants as one of a family of novel amphiphiles being investigated for gene therapeutic applications. The properties of these compounds can be controlled as well as allowed to vary naturally. Gemini surfactant-based gene delivery systems were prepared and characterized for transfer of Luciferase plasmid (pMASIA.Luc) to both COS-7 and PAM 212 cells. Characterization was accomplished using microscopy, dynamic light scattering (DLS) and zeta (ζ) potential analysis. In vitro gene expression and toxicities were evaluated in COS-7 cell and PAM 212 keratinocyte cultures.<p> The level of in vitro transfection in general was found to correlate strongly with the structure of the gemini surfactants. Among the 12-spacer-12 surfactants, incorporation of a pH-sensitive aza (N-CH3) group, which is also steric hindrance-imposing, in the spacer chain yielded increased transfection, particularly for the 12-7N-12 surfactant. In comparison, the incorporation of the more pH-sensitive imino (N-H) group in the 12-7NH-12 surfactant yielded the highest increase in transfection among the 12-spacer-12 surfactants. The deleterious effect of steric hindrance due to the aza group is more evident when comparing the transfection efficiency of 12-5N-12 (1 × aza, higher) vs. 12-8N-12 (2 × aza, lower transfection). Another highlighted structural feature is provided by the fact that both the 12-7NH-12 and 12-7N-12 surfactants had higher transfection efficiencies than 12-5N-12 and 12-8N-12 surfactants; the first pair has trimethylene spacing, which constitutes an optimal separation between nitrogen centres, while the second pair has shorter dimethylene spacings.<p> After expanding the structure of surfactants, transfection efficiencies were found to increase in response to increase in hydrocarbon tail length, but were much lower for surfactants with no amino functional groups, those that lacked the optimal trimethylene spacing, or those having both of these limitations in the gemini surfactant spacer. The 18-7NH-18 surfactant had the highest overall transfection in both COS-7 and PAM 212 cells. Gemini surfactant-based gene delivery systems capable of adopting both polymorphic structural phases and which could undergo pH-induced structural transition demonstrated high transfection efficiencies. Gemini surfactants with both characteristics (e.g., 12-7NH-12-based complexes are both polymorphic and pH-sensitive) had higher transfection than gemini surfactants with only one (e.g., 12-3-12-based complexes are only polymorphic).<p> Overall, the m-7NH-m surfactants, the most efficient surfactants studied, had transfection efficiencies similar to that of the commercial Lipofectamine Plus reagent and imposed no higher toxicity on cells relative to the less efficient surfactants. Thus, the design of the m-7NH-m surfactants to enhance their transfection abilities also ensured that their toxicity to cells were kept minimal. Overall, the design, synthesis and in vitro transfection screening of gemini surfactant candidates has revealed that the m-7NH-m surfactants have the highest transfection efficiencies; they have emerged as suitable candidates for non-viral gene delivery in vivo or at higher levels. Gene delivery investigations for six of the gemini surfactant candidates are being reported for the first time.

Citrate-coated gadolinium trifluoride (Cit-GdF3) and poly(acrylic acid)-coated nanoparticles (PAA-GdF3 NPs) were synthesized, the former reproduced from literature (though using more refined conditions), the latter through a new, two-step, ligand exchange method. Diamagnetic nanoparticle analogs (Cit-YF3 NPs) were prepared to investigate citrate interactions with the nanoparticle surface using NMR. Citrate was found to bind in numerous conformations, with a total of between 29 – 46 % bound at 0 ºC. Exchange studies revealed short residence lifetimes of one and twelve seconds respectively for bound and free forms of citrate (0 ºC), perhaps explaining the colloidal instability of these nanoparticles. PAA-GdF3 NPs were synthesized by first producing their Cit-GdF3 counterparts, and then exchanging citrate for PAA. The impetus behind this latter synthesis was the relative enhancement in stability and relaxivity attainable by these nanoparticles. The displacement of citrate by PAA was verified using diffusion NMR studies.

Citrate-coated gadolinium trifluoride (Cit-GdF3) and poly(acrylic acid)-coated nanoparticles (PAA-GdF3 NPs) were synthesized, the former reproduced from literature (though using more refined conditions), the latter through a new, two-step, ligand exchange method. Diamagnetic nanoparticle analogs (Cit-YF3 NPs) were prepared to investigate citrate interactions with the nanoparticle surface using NMR. Citrate was found to bind in numerous conformations, with a total of between 29 – 46 % bound at 0 ºC. Exchange studies revealed short residence lifetimes of one and twelve seconds respectively for bound and free forms of citrate (0 ºC), perhaps explaining the colloidal instability of these nanoparticles. PAA-GdF3 NPs were synthesized by first producing their Cit-GdF3 counterparts, and then exchanging citrate for PAA. The impetus behind this latter synthesis was the relative enhancement in stability and relaxivity attainable by these nanoparticles. The displacement of citrate by PAA was verified using diffusion NMR studies.

Carbon nanotubes are made into films or bulks, their surface or junction morphology in the networks can be modified to obtain desired electrical transport properties by various surface modification methods. The methods include incorporation of organic molecules or inorganic nanoparticles, debundling of nanotubes by dispersing agents, and microwave irradiation. Because carbon nanotubes have unique carrier transport characteristics along a sheet of graphite in a cylindrical shape, the properties can be dramatically changed by the modification. This is ideal for developing high-performance materials for thermoelectric and photovoltaic energy conversion applications. In this research, decoration of various organic/inorganic nanomaterials on carbon nanotubes was employed to enhance their electrical conductivity, to improve thermoelectric power factor by modulating their electrical conductance and thermopower, or to obtain n-type converted carbon nanotube. The electrical conductivity of double-wall nanotubes (DWNTs) decorated with tetrafluoro-tetracyanoquinodimethane (F4TCNQ) was increased up to 5.9 × 10^5 S/m. The sheet resistances were measured to be 42 Ω/sq at 75% of transmittance for HNO3/SOCl2-treated DWNT films, making their electrical conductivities 200~300% better than those of the pristine DWNT films. A series of experiments at different ion concentrations and reaction time periods were systematically performed in order to find optimum nanomaterial formation conditions and corresponding electronic transport changes for better thermoelectric power factor. For example, the thermoelectric power factors were improved by ~180% with F4TCNQ on DWNTs, ~200% with Cu on SWNTs, and ~140% with Fe on single-walled nanotubes (SWNTs). Also SWNTs was converted from p-type to n-type with a large thermopower (58 μV/K) by using polyethyleneimine (PEI) without vacuum or controlled environment. This transport behavior is believed to be from charge interactions resulted from the difference between the work functions/reduction potentials of nanotubes and nanomaterials. In addition, different dispersing agents were utilized with DWNT and SWNTs to see a debundling effect in a film network. The highest electrical conductivity of ~1.72×10^6 S/m was obtained from DWNT film which was fabricated with a nanotube solution dispersed by chlorosulfonic acid. Debundling of nanotubes in the film network has been demonstrated to be a critical parameter in order to get such high electrical property. In the last experiment, Au nanoparticle decoration on carbon nanotube bundle was performed and a measurement of themophysical properties has done before and after modifying carbon nanotube surface. Carbon nanotube bundle, herein, was bridged on microdevice to enable the measurement work. This study demonstrates a first step toward a breakthrough in order to extract the potential of carbon nanotubes regarding electron transport properties.

In this study, conjugated monomers containing fluorene units / 2-(9,9-dihexyl-2-(thiophen-2-yl)-9H-fluoren-7-yl)thiophene (TFT) and 5-(9,9-dihexyl-2-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9H-fluoren-7-yl)-2,3dihydrothieno[3,4b ][1,4] dioxine (EFE) were synthesized on the basis of donor-acceptor-donor approach and their electrochemical polymerization were achieved via potential cycling. Optical and electrochemical properties of their corresponding polymers, poly(2-(9,9-dihexyl-2-(thiophen-2-yl)-9H-fluoren-7-yl)thiophene) PTFT, and poly(5-(9,9-dihexyl-2-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9H-fluoren-7-yl)-2,3dihydrothieno[3,4b ][1,4] dioxine) PEFE, were investigated and it was found that polymer films exhibited quasi-reversible redox behavior (Epox= 1.10 V for PTFT, Epox = 0.70 V and 1.00 V for PEFE) accompanied with a reversible electrochromic behavior, yellow to dark green for PTFT, yellow to parliament blue for PEFE. Their band gap values (Eg) were found to be 2.36 eV and 2.26 eV for PTFT and PEFE, respectively. Furthermore, gold nanoparticles (AuNP) were prepared and their interaction with polymer films, PTFT and PEFE, were investigated using spectroscopic techniques. The fluorescence properties of the polymers and their composites, prepared by the interaction of AuNP with polymers, were also investigated.

We have investigated the conductance, g, of 1,4-butanedithiol linked Au nanoparticle films as a function of temperature, T, bias potential, V, and applied magnetic field, B. An interesting temperature dependence is observed for non-metallic films with thicknesses just below a critical film thickness: g ~ exp [-(T_0/T)^(1/2)] for 20 K < T < 300 K. We show that this temperature dependence is incompatible with an Efros-Shklovskii "variable range hopping" model, since "hopping distances" are too large to be consistent with tunneling processes, and tend to scale with size of super-clusters of molecularly-linked nanoparticles. We propose a "quasilocalized hopping" model based on competition between single-electron charging of super-clusters and electron backscattering within super-clusters to explain the observed temperature dependence. Various electron scattering time scales are extracted from magnetoconductance data using a modified "weak localization" model. Elastic scattering time scales are comparable to those required for an electron to traverse a nanoparticle, while inelastic and spin-orbit scattering time scales are consistent with those found in studies of conventionally-prepared granular Au films. At interfaces between metallic 1,4-butanedithiol-linked Au nanoparticle films and conventional superconductors, we find that g consistently exhibits peaks, as well as oscillations, that depend simultaneously on both V and B. Such peaks and correlated conductance oscillations are predicted by an enhanced Andreev reflection process due to disorder-driven elastic scattering and electron-hole interference in the nanoparticle film. While oscillations have been predicted by a so-called "reflectionless tunneling" model, they have not been observed at other normal-superconductor interfaces. We speculate that oscillations are observable in this system due to synthetically controlled uniformity of elastic scattering length (i.e., nanoparticle diameter) and a reduced number of current-carrying pathways, especially near the interface. Contrary to predictions of existing "reflectionless tunneling" models, we find that the periods of oscillation in B decrease as T increases. This suggests that the area of interfering pathways increases with T. We propose that this increasing area can be attributed to magnetic field penetration into the superconductor. Conductance data agrees remarkably well with known temperature dependence of penetration depth predicted by BCS theory. Our study shows that this additional region of flux must be considered in experimental and theoretical studies of "reflectionless tunneling", and underscores the utility of molecularly-linked nano\-particle films as a platform for studying charge transport.

Applied cancer research is heavily focused on the development of diagnostic tools with high sensitivity and specificity that are able to accurately detect the presence and anatomical location of neoplastic cells, as well as therapeutic strategies that are effective at curing or controlling the disease while being minimally invasive and having negligible side effects. Recently, much effort has been placed on the development of nanoparticles as diagnostic imaging and therapeutic agents, and several of these nanoplatforms have been successfully adopted in both the research and clinical arenas. This thesis describes the development of a nanoparticulate liposome system for use in a number of applications including multimodality imaging with computed tomography (CT) and magnetic resonance (MR), longitudinal vascular imaging, image-based biodistribution assessment, and CT detection of neoplastic and inflammatory lesions. Extensive in vitro and in vivo characterization was performed to determine the physico-chemical properties of the liposome agent, including its size, morphology, stability and agent loading, as well as its pharmacokinetics, biodistribution, tumor targeting and imaging performance. Emphasis was placed on the in vivo CT-based quantification of liposome accumulation and clearance from healthy and tumor tissues in a VX2 carcinoma rabbit model, gaining insight not only on the spatial but also the temporal biodistribution of the agent. The thesis concludes with a report that describes the performance of liposomes and CT imaging to detect and localize tumor and inflammatory lesions as compared to that of 18F-fluorodeoxyglucose (FDG) – positron emission tomography (PET). The outcome of the study suggests that liposome-CT could be employed as a competitive method for whole body image-based disease detection and localization. Overall, this work demonstrated that this liposome agent along with quantitative imaging systems and analysis tools, has the potential to positively impact cancer treatment outcome through improved diagnosis and staging, as well as enable personalization of treatment delivery via target delineation. However, in order to prove clinical benefit, steps must be taken to advance this agent through the regulatory stages and obtain approval for its use in humans. Ultimately, the clinical adoption of this multifunctional agent may offer improvements for disease detection, spatial delineation and therapy guidance.

The feasibility of highly dispersed gold nanocatalyst supported on yttria-stabilized zirconia (YSZ) for the model reactions of C2H4 and CO oxidation is demonstrated for the first time. Gold nanoparticles are synthesized on YSZ powder by chemical reduction of the precursor salt in the mixture of ethanol, water and polyvinylpyrrolidone (PVP). Resulting metal loading of the catalysts are 1 wt.% with average particle sizes ranging from 6 to 9 nm. Results of CO and C2H4 oxidation display catalytic activity at 65 0C and 25 0C for CO and C2H4 oxidation, respectively. The catalytic properties of the catalysts are different due to their average particle size. Electrochemical Promotion of Catalysis (EPOC) of C2H4 oxidation is demonstrated. Application of constant potential difference between two electrodes in the bipolar electrochemical cell led to increase in C2H4 conversion. A proposed mechanism explains the bipolar EPOC phenomenon through formation of O2- flux across the electrochemical cell, resulting in the change of Work Function of gold nanoparticles placed in between the electrodes and is electronically isolated.