The objective of this research was to evaluate the treatment efficiency of a nitrate-contaminated soil by combined technologies of the injection of palladized nanoiron slurry and electrokinetic remediation process. First, nanoiron was prepared by two synthesis processes based on the same chemical reduction principle yielding products of NZVI-A and NZVI-B, respectively. Then they were characterized by various methods. Micrographs of scanning electron microscopy have shown that a majority of these nanoparticles were in the range of 50-80 nm and 30-40 nm, respectively. Results of nitrogen gas adsorption-desorption show that NZVI-A and NZVI-B are mesorporous (ca. 30-40 Å) with BET surface areas of 128 m2/g and 77 m2/g, respectively. Results of X-ray diffractometry have shown that both types of nanoiron were poor in crystallinity. Results of zeta-potential measurements indicated that NZVI-A and NZVI-B had the same isoelectric point at pH 6.0. Although NZVI-A and NZVI-B were found to be superparamagnetic, their magnetization values were low. Poly acrylic acid (PAA), an anionic dispersant, was employed for stabilizing various types of nanoiron. Then Palladium¡]ca. 1 wt% of iron¡^ was selected as catalysis to form palladized nanoiron¡]Pd/Fe¡^. Results have demonstrated that an addition of 1 vol. % of PAA during the nanoiron preparation process would result in a good stabilization of nanoiron and nanoscale Pd/Fe slurry. Batch tests were carried out to investigate the effects of pH variation on degradation of nitrate aqueous solutions. Experimental results have indicated that palladized nanoiron outperformed nanoiron in treatment of nitrate in this study. Apparently, an employment of catalyst would enhance the treatment efficiency. Further, an exponential increase of the reaction rate was found for the systems at low pH. The final stage of this study was to evaluate the treatment efficiency of combined technologies of the injection of palladized nanoiron¡]Pd/Fe¡^ slurry and electrokinetic remediation process in treating a nitrate-contaminated soil. Test conditions used were given as follows: (1) slurry injection to four different positions in the soil matrix; (2) electric potential gradient: 1 V/cm; (3) daily addition of 20 mL of palladized nanoiron (4 g/L) slurry to the injection position; and (4) reaction time: 6 days. Test results have shown that addition of palladized nanoiron slurry to the anode reservoir yielded the lowest residual nitrate concentration in soil. Namely, about 99.5% removal of nitrate from soil. On the other hand, the acidic condition of soil matrix around the anode reservoir would enhance the degradation of nitrate therein. Based on the above findings, the treatment method employed in this work was proven to be a novel and efficient one in treating nitrate contaminated soil.

En esta tesis se han desarrollado modelos compactos de corriente de fuga por túnel de puerta en SOI MOSFET (de simple y doble puerta) avanzados basados en una aproximación WKB de la probabilidad de túnel. Se han estudiado los materiales dieléctricos high-k más prometedores para los diferentes requisitos de nodos tecnológicos de acuerdo ala hoja de ruta ITRS de miniaturización de dispositivos electrónicos. Hemos presentado un modelo compacto de particionamiento de la corriente de fuga de puerta para un MOSFET nanométrico de doble puerta (DG MOSFET), utilizando modelos analíticos de la corriente de fuga por el túnel directo de puerta. Se desarrollaron también Los modelos analíticos dependientes de la temperatura de la corriente de túnel en la región de inversión y de la corriente túnel asistido por trampas en régimen subumbral. Finalmente, se desarrolló una técnica de extracción automática de parámetros de nuestro modelo compacto en DG MOSFET incluyendo efectos de canal corto. La corriente de la puerta por túnel directo y asistido por trampas modelada mediante los parámetros extraídos se verificó exitosamente mediante comparación con medidas experimentales.

<p>Nanoscale devices offer the technological advances to enable a new era in computing. Device sizes at the molecular-scale have the potential to expand the domain of conventional computer systems to reach into environments and application domains that are otherwise impractical, such as single-cell sensing or micro-environmental monitoring.</p><p>New potential application domains, like biological scale computing, require processing elements that can function inside nanoscale volumes (e.g. single biological cells) and are thus subject to extreme size and resource constraints. In this thesis we address these critical new domain challenges through a synergistic approach that matches manufacturing techniques, circuit technology, and architectural design with application requirements. We explore and vertically integrate these three fronts: a) assembly methods that can cost-effectively provide nanometer feature sizes, b) device technologies for molecular-scale computing and sensing, and c) architectural design techniques for nanoscale processors, with the goal of mapping a potential path toward achieving molecular-scale computing.</p><p>We make four primary contributions in this thesis. First, we develop and experimentally demonstrate a scalable, cost-effective DNA self-assembly-based fabrication technique for molecular circuits. Second, we propose and evaluate Resonance Energy Transfer (RET) logic, a novel nanoscale technology for computing based on single-molecule optical devices. Third, we design and experimentally demonstrate selective sensing of several biomolecules using RET-logic elements. Fourth, we explore the architectural implications of integrating computation and molecular sensors to form nanoscale sensor processors (nSP), nanoscale-sized systems that can sense, process, store and communicate molecular information. Through the use of self-assembly manufacturing, RET molecular logic, and novel architectural techniques, the smallest nSP design is about the size of the largest known virus.</p> / Dissertation

Electron Beam Chemical Vapor Deposition (EBCVD) is a process by which an electron beam is used to decompose adsorbed reagent molecules to produce a deposit. The primary electrons from the beam, and especially the secondary electrons emitted from the substrate, dissociate the adsorbed molecules. Important factors for the deposition process include the beam parameters and reagent gas composition. Simple structures are fabricated through utilization of the various scanning modes of an SEM. Fibers (pillar-like structures) can be deposited, and lines (wall-like structures) can be deposited easily. This investigation focuses on the process parameters controlling deposition rate and geometry for platinum and carbon fibers and lines in a modified SEM. Platinum deposition was performed using a system with a small diameter needle that supplied a localized flow of gas from an organometallic platinum compound. Carbon deposition was performed in the Environmental mode, in which the microscope chamber is filled with a specified pressure of reagent gas. Statistically designed experiments were performed for platinum fiber and line deposition. Analysis indicated that the beam current and deposition time were dominant factors in determining the deposition rate. The voltage also had a significant effect on fiber deposition. For platinum line deposition, the effects of the dwell time and line time were also studied. The line time had a significant effect on line height deposited per scan. Optimization analysis was performed, and results indicated that high voltage and high beam current led to higher aspect ratios. Medium voltage and low beam current were preferable for depositing minimal width lines (less than 200 nm). Low voltage and high beam current were preferable for maximum deposition rates. EDS and EELS performed for platinum deposits in a TEM indicated amorphous structure with no carbon detected. This differs significantly from previously reported results. Statistically designed experiments were performed for carbon line deposition. The voltage, beam current, and dwell/line time were studied. Increasing line time led to a significant increase in line height/scan and appeared to be a dominant factor. Lower beam currents appeared to favor higher deposition rates. TEM analysis indicated that carbon deposits were mostly amorphous.

Common to molecular electronics studies, nanoscale break junctions created through electromigration also naturally produce electroluminescent arrays of individual gold nanoclusters spanning the electrodes. Due to inelastic electron tunneling into cluster electronic energy levels, these several-atom nanoclusters (Au~18-22) exhibit bright, field-dependent, antibunched emission in the near infrared (650800 nm), acting as room-temperature electrically driven single-photon sources. AC electrical excitation with time-stamping of photon arrival times enables fast and local tracking of electrode-nanocluster coupling dynamics demonstrating that charge injection to the clusters is directly modulated by dynamic coupling to individual electrodes. The electrode-nanocluster coupling rate fluctuates by nearly an order of magnitude and, due to the asymmetry of the electromigration process, exhibits preferential charge injection from the anode. Directly reporting on (and often facilitating) nanoscale charge transport, time-tagged single-molecule electroluminescence reveals a significant mechanism for nanoscale charge transport in nanoscale gold break junctions, and offers direct readout of the electrode-molecule interactions that can be correlated with current flow. Single-molecule electroluminescence techniques for characterization of electrode heterogeneity and dynamics as well as implications for future research are discussed.

The research presented in this dissertation pertains to the evaluation of stiffness of carbon nanotubes (CNTs) in a multiscale framework and modeling of the interfacial mechanical behavior in CNT-polymer nanocomposites. The goal is to study the mechanical behavior of CNTs and CNT-polymer interfaces at the atomic level, and utilize this information to develop predictive capabilities of material behavior at the macroscale. Stiffness of CNTs is analyzed through quantum mechanical (QM) calculations while the CNT-polymer interface is examined using molecular dynamics (MD) simulations. CNT-polymer-matrix composites exhibit promising properties as structural materials and constitutive models are sought to predict their macroscale behavior. The reliability of determining the homogenized response of such materials depends upon the ability to accurately capture the interfacial behavior between the nanotubes and the polymer matrix. In the proposed work, atomistic methods are be used to investigate the behavior of the interface by utilizing appropriately chosen atomistic representative volume elements (RVEs). Atomistic simulations are conducted on the RVEs to study mechanical separation with and without covalent functionalization between the polymeric matrix and two filler materials, namely graphite and a (12,0) Single Wall zig zag CNT. The information obtained from atomistic studies of separation is applicable for higher level length scale models as cohesive zone properties. The results of the present research have been correlated with available experimental data from characterization efforts.

The main objective of this study was to evaluate the feasibility of using nanoscale zero-valent iron (nZVI) as the source of hydrogen to enhance in situ anaerobic biodegradation of trichloroethylene (TCE). In the first part of this study, microcosms were constructed to evaluate the effects of different controlling factors [e.g., different redox conditions (aerobic and anaerobic conditions), different microorganisms (in situ microorganisms, activated sludge, and anaerobic sludge), and different sources of substrates and electron donors (phenol, cane molasses, hydrogen, and nZVI)] on TCE biodegradation. In the second part of this study, batch experiments were conducted to evaluate the feasibility of hydrogen production by nZVI and bimetallic particles. Results from the microcosm study indicate that in-situ microorganisms were capable of degrading TCE under aerobic and anaerobic conditions. Results also show that TCE removal was more effective by activated sludge and anaerobic sludge. Aerobic biodegradation of TCE was enhanced by the addition of phenol and cane molasses. Under anaerobic conditions, TCE removal could be improved when cane molasses and hydrogen were supplied. In addition, anaerobic TCE degradation was more effective with the presence of hydrogen. Results of microcosms conducted with the addition of nZVI reveal that TCE was degraded completely in both live and autoclaved microcosms. This indicates that chemical reductive dechlorination seemed to dominate the removal of TCE in microcosms. Therefore, further studies with higher TCE concentrations or lower nZVI doses need to be conducted to determine the effects of the produced hydrogen on TCE biodegradation. Results from the hydrogen production experiments indicate that efficiency of hydrogen production by nZVI ranged from 30% to 76%. Higher dose of nZVI addition resulted in higher amount of hydrogen production. The total amounts of hydrogen production were correlated with the doses of nZVI. In addition, rates and efficiency of hydrogen production by bimetallic particles were better than those of nZVI. Results of the batch experiments reveal that nZVI and bimetallic particles had good efficiency on hydrogen production. This indicates that nZVI and bimetallic particles have high potential to be used as hydrogen producers. In this study, a simple system consisted of only water and nZVI or bimetallic particles was applied to produce hydrogen. Although TCE in microcosms with nZVI addition was totally consumed by nZVI, results of microcosms with hydrogen addition demonstrated that hydrogen was able to improve the efficiency of anaerobic TCE biodegradation. Thus, it may be feasible to use nZVI as the source of hydrogen to enhance in situ anaerobic biodegradation of TCE. The advantages of using nZVI as the source of hydrogen include: (1) rapid removal of significant contaminant concentrations in the early stage of nZVI injection; (2) creation of a more reducing environment; (3) safer than liquid hydrogen, which is stored in steel containers; and (4) direct hydrogen supply without transfer of biological mechanisms compared to commercial hydrogen release compounds and other organic substrates. Results of this study suggest that biological reductive dechlorination of TCE can be enhanced if proper doses of nZVI are supplied in situ. Knowledge and comprehension obtained in this study will be helpful in designing an enhanced in situ anaerobic bioremediation system for a TCE-contaminated site.

Thanks to their extraordinary properties, carbon nanotubes reveal a promising potential for applications on the nanometre scale. When filled with metals or ferromagnets, nano-wires and magnets with a protecting carbon shell are realised. Different synthesis routes are described, such as laser ablation and chemical vapour deposition. Probes for magnetic force microscopy based on ironfilled carbon nanotubes are presented, and demonstrate a high spatial resolution, with the carbon shells at the same time providing effective wear resistance. We show also the potential of carbon nanotubes for biomedical applications, in particular their suitability as magnetic nano-heaters, drug-carrier systems or sensors for diagnostic and therapeutic usage on the cellular level. / Außergewöhnliche Materialeigenschaften machen Kohlenstoffnanoröhren zu einem vielseitigen nanoskaligen Werkstoff. Füllt man sie zum Beispiel mit metallischen oder ferromagnetischen Materialien, so ergeben sich durch eine Kohlenstoffhülle geschützte „Nano- Kabel“ oder Nano-Magnete. Neben verschiedenen Syntheseverfahren wie der Laserablation und der Chemischen Gasphasenabscheidung werden grundlegende physikalische Eigenschaften sowie Anwendungen in der Messtechnik und in der Medizin vorgestellt. In der Magnetkraftmikroskopie versprechen magnetisch gefüllte Kohlenstoffnanoröhren eine hohe laterale Auflösung bei gleichzeitigem Schutz des magnetischen Messsensors durch die Außenhülle. Im Bereich der biomedizinischen Anwendungen stellen Kohlenstoffnanoröhren ein nanoskaliges Transportmedium dar, das zum Transfer von Funktionsmaterialien in einzelne Zellen, zum Beispiel für magnetische Sensorik oder für Medikamententransporte, angewendet werden kann.

As silicon-based transistor technology continues to scale ever downward, anticipation of the fundamental limitations of ultimately-scaled devices has driven research into alternative device technologies as well as new materials for interconnects and packaging. Additionally, as power dissipation becomes an increasingly important challenge in highly miniaturized devices, both the implementation and verification of high mobility, high thermal conductivity materials, such as low dimensional carbon nanomaterials, and the experimental investigation of heat transfer in the nanoscale regime are requisite to continued progress. This work furthers the current understanding of structure-property relationships in low dimensional carbon nanomaterials, specifically carbon nanotubes (CNTs) and graphene, through use of combined thermal conductance and transmission electron microscopy (TEM) measurements on the same individual nanomaterials suspended between two micro-resistance thermometers. Through the development of a method to measure thermal contact resistance, the intrinsic thermal conductivity, [kappa], of multi-walled (MW) CNTs is found to correlate with TEM observed defect density, linking phonon-defect scattering to the low [kappa] in these chemical vapor deposition (CVD) synthesized nanomaterials. For single- (S) and double- (D) walled (W) CNTs, the [kappa] is found to be limited by thermal contact resistance for the as-grown samples but still four times higher than that for bulk Si. Additionally, through the use of a combined thermal transport-TEM study, the [kappa] of bi-layer graphene is correlated with both crystal structure and surface conditions. Theoretical modeling of the [kappa] temperature dependence allows for the determination that phonon scattering mechanisms in suspended bi-layer graphene with a thin polymeric coating are similar to those for the case of graphene supported on SiO₂. Furthermore, a method is developed to investigate heat transfer through a nanoscale point contact formed between a sharp silicon tip and a silicon substrate in an ultra high vacuum (UHV) atomic force microscope (AFM). A contact mechanics model of the interface, combined with a heat transport model considering solid-solid conduction and near-field thermal radiation leads to the conclusion that the thermal resistance of the nanoscale point contact is dominated by solid-solid conduction. / text

This dissertation focuses on characterizing the nanoscale and surface averaged electrical properties of transparent conducting oxide (TCO) electrodes such as indium tin oxide (ITO) and transparent metal-oxide (MO) electron selective interlayers (ESLs), such as zinc oxide (ZnO), the ability of these materials to rapidly extract photogenerated charges from organic semiconductors (OSCs) used in organic photovoltaic (OPV) cells, and evaluating their impact on the power conversion efficiency (PCE) of OPV devices. In Chapter 1, we will introduce the fundamental principles regarding the need for low cost power generation, the benefits of OPV technologies, as well as the key principles that govern the operation of OPV devices and the key innovations that have advanced this technology. In Chapter 2 of this dissertation, we demonstrate an innovative application of conductive probe atomic force microscopy (CAFM) to map the nanoscale electrical heterogeneity at the interface between an electrode, such as ITO, and an OSC such as the p-type OSC copper phthalocyanine (CuPc).(MacDonald et al. (2012) ACS Nano, 6, p. 9623) In this work we collected arrays of J-V curves, using a CAFM probe as the top contact of CuPc/ITO systems, to map the local J-V responses. By comparing J-V responses to known models for charge transport, we were able to determine if the local rate-limiting step for charge transport is through the OSC (ohmic) or the CuPc/ITO interface (nonohmic). These results strongly correlate with device PCE, as demonstrated through the controlled addition of insulating alkylphosphonic acid self-assembled monolayers (SAMs) at the ITO/CuPc interface. Subsequent chapters focus on the electrical property characterization of RF-magnetron sputtered ZnO (sp-ZnO) ESL films on ITO substrates. We have shown that the energetic alignment of ESLs and the organic semiconducting (OSC) active materials plays a critical role in determining the PCE of OPV devices and the appearance of, or lack thereof, UV light soaking sensitivity. For ZnO and fullerene interfaces, we have shown that either minimizing the oxygen partial pressure during ZnO deposition or exposure of ZnO to UV light minimizes the energetic offset at this interface and maximizes device PCE. We have used a combination of device testing, device modeling, and impedance spectroscopy to fully characterize the effects that energetic alignment has on the charge carrier transport and charge carrier distribution within the OPV device. This work can be found in Chapter 3 of this dissertation and is in preparation for publication. We have also shown that the local properties of sp-ZnO films varies as a function of the underlying ITO crystal face. We show that the local ITO crystal face determines the local nucleation and growth of the sp-ZnO films. We demonstrate that this effects the morphology, the chemical resistance to etching as well as the surface electrical properties of the sp-ZnO films. This is likely due to differences in the surface mobility of sputtered Zn and O atoms on these crystal faces during film nucleation. This affects the nanoscale distribution of electrical and chemical properties. As a result we demonstrate that the PCE, and UV sensitivity of the J-V response of OPVs using sp-ZnO ESLs are strongly impacted by the distribution of ITO crystal faces at the surface of the substrate. This work can be found in Chapter 4 of this dissertation and is in preparation for publication. These studies have contributed to a detailed understanding of the role that electrical heterogeneity, insulating barriers and energetic alignment at the MO/OSC interface play in OPV PCE.