Gold nanoparticle (AuNP) is used for the detection of biomolecules and study of the interaction between bio-molecules with the aid of dark field microscopy (DFM). AuNP exhibits unique optical properties and ability to conjugate with different biomolecules either by covalent binding or physical absorption, which allow the AuNP possessing a variety of biological application. We reported a sensitive detection system for measuring DNA–protein interaction at single plasmonic metal nanoparticles level by Localized Scattering Plasmon Resonance (LSPR) spectroscopy. As a proof of concept, DNA molecules were conjugated to gold nanoparticles (AuNPs) through gold–thiol chemistry and the resulted complex was served as single-particle probes of human topoisomerase I (TOPO). By recording the changes in Rayleigh light scattering signal of the individual nanoparticles upon protein binding, DNA–protein interaction was monitored and measured. The .max shifts in LSPR spectrum of individual AuNP was found to be highly correlated with the amount of TOPO that bound onto. We presented an immunosensing platform to detect cancer biomarkers by collecting the LSPR signal of immune-target conjugated gold nanoparticle (AuNP). Prostate specific antigen (PSA), which is a FDA-approved biomarker for prostate cancer, was chosen as an example. Herein, the immunoreaction of PSA, capturing PSA antibody (CHYH1) (Ab1), and detecting PSA antibody (CHYH2) (Ab2) was studied with a spectrometer coupled-dark field microscope. LSPR of immunotarget conjugated AuNP was directly measured. In brief, Ab1 and Ab2 were covalently conjugated with AuNPs separately, followed by addition of PSA for the formation of sandwiched immuno-complex in PBS solution. Then, the complex was immobilized on surface of glass slide for capturing dark-field images and LSPR spectra. Besides, to study the ligand-receptor interaction, we prospect a detection system at single plasmonic metal nanoparticle level by LSPR spectroscopy. Glucocorticoid receptor protein (GR) was chosen as example with two ligands ginsenoside-Rg1 (Rg1) and dexamethasone (DEX). Herein, dsDNA molecules were covalently conjugated with AuNPs and the resulted complex was used as single particle probes of GR. The binding of GR to the dsDNA could be promoted by the agonistic ligands. DNA-GR interaction in the presence of ligands was monitored and measured by recording the changes of LSPR upon protein binding. This technique provides a sensitive and high-throughput platform to screen and monitor accurately the speci.c biomolecular interactions. It is capable of revealing information such as particle–particle variations that might be buried in conventional bulk measurement.

<p> III-nitride based photocathodes have been the subject of much research in photoemissive devices for ultraviolet (UV) detection in astronomy and defense applications. In order to achieve high quantum efficiency (QE), negative electron affinity (NEA) is necessary to allow for carriers that have relaxed to the conduction band minimum to escape. NEA in III-nitride UV photocathodes is conventionally reached via cesium-based surface treatment of p-type GaN. However, this treatment is highly reactive in air and photocathodes using this technology have been reported to suffer from chemical instability and QE degradation over time. </p><p> Recent work has shown the potential to take advantage of the spontaneous and piezoelectric polarization exhibited by III-nitride materials in order to achieve permanent NEA in AlGaN-based photocathode structures without the need for cesiation. The N-polar orientation has potential for improved and expanded device design space due to the reversal of the built-in and stress-induced polarization fields. However, achieving smooth high-quality N-polar material has traditionally been a challenge due to the formation of large hexagonal hillock structures on a typical N-polar surface. Furthermore, achieving high-conductivity p-type material is crucial for high efficiency photocathodes (among other devices), but has been a long-standing challenge in III-nitrides due to the high ionization energy of the Mg dopant and tendancy for self-compensation. </p><p> Rapid development and optimization of device design requires accurate modeling of the photoemission process to shorten the feedback loop, but the complexity of the photoemission process makes development of accurate models difficult. Traditionally, it has been assumed that photo-excited hot-carriers are thermalized to the conduction band minimum during transport, which allows for simplified modeling. This assumption breaks down for high-energy excitation or reflection-mode photocathodes, and more accurate treatments are needed. The development in recent years of accurate Monte Carlo modeling of III-nitrides enables simulation of hot-carrier transport. Application of Monte Carlo transport for photoemission modeling has recently been studied in Cs-treated NEA GaAs photocathodes with close agreement to experimental results. </p><p> This work outlines development of Cs-free III-nitride photocathodes via use of surface treatments and materials optimization resulting in peak quantum efficiencies of 23\% for N-polar devices. This high QE is comparable to results from cesiated devices. Physics-based device simulations show the promise of N-polar orientation, with the ability to obtain a similar band profile as Ga-polar with 2 orders of magnitude lower p-doping in addition to the potential for substantial narrowing of surface band bending region. Materials development and optimization focused on two aspects: surface morphology and doping efficiency. These optimizations have resulted in a decrease in undesirable surface features by over 3 orders of magnitude via the use of indium surfactant and buffer optimization. For Ga-polar photocathode structures, free hole concentrations in excess of 1 x 10¹⁸ cm^&ndash;3 was achieved in AlGaN absorber of 28% Al composition, via the use of a pulsed deposition technique, representing over a 3 times increase from traditional epitaxy method. Application of the same technique to N-polar films showed reduced doping effectiveness as compared to Ga-polar films due to differences in surface configuration. As part of this study, Monte Carlo simulator based on the open-sourced GNU Archimedes was developed. The Monte Carlo simulation was developed to support III-nitrides and photoexcitation and emission processes in devices based on this material system. Simulated results showed close agreement with experimentally measured values, validating the technique. Results point towards several important factors affecting emission behavior and suggest future research focus. Additionally, photoemission simulation gives evidence towards proper satellite valley band parameters which are subject to much uncertainty.</p><p>

<p> We have developed a high density lipoprotein (HDL)-based platform for transport and delivery of hydrophobic gold nanoparticles (AuNP). The ability of apolipoprotein E3 (apoE3) to act as a ligand for the low-density lipoprotein receptor (LDLr) was exploited to gain entry of HDL with AuNP into glioblastoma cells. AuNP of 3, 10 and 17 nm diameter, the latter two synthesized by phase transfer process, were solubilized by integration into reconstituted HDL (rHDL). Absorption spectroscopy indicated the presence of stable particles with signature surface plasmon bands, while electron microscopy revealed AuNP embedded in rHDL core. The rHDL-AuNP complexes displayed robust binding to the LDLr, were internalized by the glioblastoma cells, and appeared as aggregated AuNP in the endosomal-lysosomal compartments. The rHDL-AuNP generated little cytotoxicity and were able to cross the blood brain barrier. The findings bear significance since they offer an effective means of delivering AuNP across tumor cell membrane.</p><p>

The discovery of carbon nanotubes has stimulated intensive research on the synthesis, modification and physical properties of these novel carbon materials due to their unique and one dimensional pore structure, rolled graphitic layers as well as their potential application in sensors, separations, electronic devices, gas storage and quantum dots. Research has suggested that the role of nitrogen in the synthesis of carbon nanotubes could be either to enhance the formation of graphitic layers on the catalyst or to increase the separation of the graphitic layers from the catalyst. The studies further suggested that if nitrogen is incorporated into the structure then the presence of nitrogen in the pentagonal defects would induce the bending and distortion of the carbon nanotubes, whilst nitrogen in substitutional sites would not produce major distortion of the nanotubes. Well-aligned carbon nanotubes were grown from the pyrolysis of ferrocene, toluene and small fractions of various amines, aromatic amines, diamines and amides by nebulized spray pyrolysis at temperature of 8500C. Transmission electron microscopy and scanning electron microscopy reveal that the carbon nanotubes possess bamboo-like-structures and that the nanotubes are well-aligned. The nanotubes ranged from 36 nm to 121 nm in diameter and 65 μm to 625 μm in length depending on the specific growth conditions such as concentration of various nitrogen containing hydrocarbons, growth time and flow rates of the carrier gasses. Raman spectra show the characteristics bands at 1336 cm-1 (D-band) and 1583 cm-1 (G-band). The G-band modes are larger than the D-band modes, suggesting that the carbon nanotubes synthesized In the presence of nitrogen additives are more graphitic than those synthesized without nitrogen addition. TGA analysis under static air environment, showed that the carbon nanotubes are stable within a temperature range of 40 – 5600C and in the at temperature range of 590 – 8000C, the mass loss of carbon nanotubes is constant. The residual metal content in the carbon nanotubes was found to be approximately 20%, when nanotubes were synthesized by the pyrolysis of toluene and ferrocene and about 7% after addition of nitrogen containing hydrocarbons to the catalyst. Selected carbon nanotubes were purified using a microwave purification method. The mass loss between unpurified carbon nanotubes and purified nanotubes were found to be insignificant. The diameters of the carbon nanotubes were found to have been reduced drastically, which suggest that defects were removed during the purification process. The data generated in this study revealed that nitrogen containing hydrocarbons acted as co-promoters of CNTs during the synthesis of carbon nanotubes. / Mr. L.M. Cele Prof. N. Coville

Intelligent morphing structures will revolutionize micro-robotics, wearable technology, and tiny electro-mechanical systems. The ideal morphing structure is thin and flexible with the ability to deform and sense its surroundings. Biological organisms provide the inspiration for this kind of technology. By developing a low-profile film that changes shape and detects ambient conditions, it will provide leeway to mimicking the way organisms move throughout various mediums and terrains, while deliberating their next actions according to the current environment and the actions that they have previously attempted. This dissertation will introduce carbon nanotube buckypaper as a key material in facilitating intelligent morphing schemes. In this research, a scalable manufacturing process for producing buckypaper composite actuators is introduced. The process can produce large batches of actuators at a time; this is critical for designing complex morphing structures in the future. The research also includes the electro-chemical modelling of the buckypaper composite actuator. Many researchers have introduced their own designs for actuators; however, most actuators lack the sensing component needed to be considered in morphing structures. This research will introduce a scalable method for buckypaper strain sensors as well. The sensors can detect micro-strains with higher sensitivity than commercial strain gauges. They can also detect finger movements and micro-strains in carbon composite materials. The overall objective is to synchronize the two devices so that a closed-loop system can provide corrections to the actuators movements. This research is essential to progressing low-profile morphing structures. / A Dissertation submitted to the Department of Industrial and Manufacturing Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester 2018. / May 15, 2018. / Carbon Nanotubes, Morphing Structures, Nanotechnology, Scalable Manufacturing, Structural Health Monitoring, Wearable Sensors / Includes bibliographical references. / Zhiyong (Richard) Liang, Professor Directing Dissertation; Simone Peterson Hruda, University Representative; Pierre-Jean Cottinet, Committee Member; Changchun (Chad) Zeng, Committee Member; Arda Vanli, Committee Member.

Electrical signaling in the olfactory bulb (OB) is modulated by changes in metabolic state. The voltage-gated potassium channel, Kv1.3, makes up 60 - 80% of the outward current flow in mitral cells (MCs), the primary projection neurons of the OB. The metabolic molecules GLP-1, insulin, and glucose are present in the OB and modulate MC signaling by reducing the activity of Kv1.3. In obesity and diabetes, modulation of MC signaling and Kv1.3 current flow by these molecules is absent. Gene-targeted deletion of Kv1.3 (Kv1.3 -/-) produces a phenotype that encompasses changes in olfactory ability and metabolism. Kv1.3 -/- mice are “supersmellers”, with an enhanced ability to detect and discriminate odors, are leaner than their wild-type counterparts and resistant to diet-induced obesity. These observations suggest metabolism, the OB and Kv1.3 are intimately linked, providing opportunity for therapeutic intervention at the level of the voltage-gated potassium channel. Strategies towards targeting Kv1.3 in the OB, but not other regions of the brain or periphery, are desired. There are several natural modulators of Kv1.3 that can be utilized for therapeutic targeting of the channel. Nedd4-2 is an ubiquitin ligase that mediates ubiquination and degradation of target proteins and can act to regulate Kv1.3 channel density, while the adaptor protein Grb10 can mediate Nedd4-2 activity. Patch-clamp electrophysiology in HEK293 cells, SDS-PAGE, immunoprecipitation, and mutagenesis strategies demonstrated a channel/adaptor/ ligase signalplex. Mutation of the C-terminal, SH3-recognition or ubiquitination sites on Kv1.3 retained the observed co-immunoprecipitation between Nedd4-2/Kv1.3, while the latter prevented a reduction in channel density. A model based on these data is presented for which an atypical interaction may permit Nedd4-2/Kv1.3 interactions that lead to protein degradation and reduced current density, and can be disrupted by Nedd4-2/Grb10 interactions. Venom-derived ion channel inhibitors are a strong alternative to natively expressed Kv1.3 modulators. These inhibitors have strong channel selectivity, potency, and stability; however, tracking delivery to their target can be challenging. Margatoxin (MgTx) is a potent Kv1.3 inhibitor and conjugation to luminescent quantum dots (QDs) can provide a means to track its delivery. Towards this, two approaches were taken. Covalent conjugation of MgTx to QDs produced QD-MgTx, which exhibited a retention of known biophysical properties associated with block of the vestibule of Kv1.3. Towards a more efficient and controlled conjugation, a polyhistidine tagged MgTx (HisMgTxFSU) was produced and conjugated to QDs via polyhistidine-mediated self assembly (QDHisMgTxFSU). Similar to QD-MgTx, QDHisMgTxFSU had a strong ability to inhibit Kv1.3 in HEK293 cells, excite mitral cells of the OB, and label Kv1.3 expressing HEK293 cells. When delivered to the OB via cannula guided delivery, QDHisMgTxFSU failed to label Kv1.3 expressing mitral cells. Therapeutic effects due to delivery of QDHisMgTxFSU, however, were observed. To better understand the role of Kv1.3 in the OB and metabolism, HisMgTxFSU and QDHisMgTxFSU were delivered to the OB of obese mice via cannula-guided delivery and changes in metabolism were measured. Compared to control animals, targeted inhibition of Kv1.3 was found to prevent weight gain and reduce the respiratory quotient (RER). These data provide evidence for the first time that the OB plays a key role in energy regulation and the pathways involved in this regulation are proposed. / A Dissertation submitted to the Institute of Molecular Biophysics in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester 2018. / July 16, 2018. / Electrophysiology, Ion Channel, Metabolism, Olfactory Bulb, Pharmacology, Quantum Dots / Includes bibliographical references. / Debra Ann Fadool, Professor Directing Dissertation; Thomas Houpt, University Representative; Timothy Cross, Committee Member; Richard Bertram, Committee Member; Yi Zhou, Committee Member.

Exploring phenomena occurring at the molecular level is critical to deepen our understanding of the living world. However conventional analytical tools are often limited in both spatial resolution and sensitivity. In this work we evaluate how fractal plasmonic structures can be developed for Surface Enhanced InfraRed Absorption (SEIRA) substrates to boost the infrared fingerprint signal of unknown single entities such as nanomaterials, virus or other biological systems. In this thesis, we present an overview of developments using light-matter interaction to push the limit of spatial resolution and sensitivity (Chapter 1). We discuss technological advances that allow nanoscale infrared spectroscopy despite inherent diffraction limit and remaining limitations in the field. In Chapter 2, we delve into the principles of techniques used in our work and compare them with other state-of-the-art in the field. We expand on the principle of nanoscale infrared spectroscopy and introduce how existing capabilities are uniquely suited to explore the near-field behavior of plasmonic structures at the nanoscale. In Chapter 3, we describe the design and fabrication of fractal Cesaro geometries we selected to evaluate broadband signal enhancement. The approaches used for far-field and near-field characterization of the plasmonic behavior are presented. In Chapter 4, we present our experimental results describing the behavior of Cesaro fractals with increasing levels of complexity. After confirming the far-field infrared resonances in the mid-infrared range in higher order structures, we coat the structures with a thin polymer film to map the regions with the highest photothermal enhancements, as an indirect indication of the near-field behavior of the plasmonic structures. We show that different film thicknesses of the polymer deposited on the plasmonic substrates provide some insight on the effect of photothermal propagation, which influences the signal level and spatial resolution of nanoscale infrared (nanoIR) spectroscopy and microscopy measurements. Signal enhancement performance of our structures is evaluated as a function of excitation frequency, laser power, laser pulse width, and sample orientation. Finally, we provide a summary of our work in Chapter 5. We also discuss types of samples for which our structures might be beneficial and consider outlooks on future work of this project.

The thesis reports the investigation of producing copper nanoparticle composites with graphene oxides (GO) using poly (sodium 4-styrenesulfonate) (PSS) and copper nanowires through the reduction of copper oxide nanowires using hydrazine. It was discovered that PSS improved the dispersity of GO and increased the absorption of copper ions on GO. An electrochemical reduction of GO/PSS/copper ion dispersion produced copper nanoparticles on GO surfaces. Reducing copper oxide nanowires on copper foils using hydrazine was achieved at a temperature where copper nanowires maintained their nanoscale structures.

Vertically oriented graphene nanosheets (VOGN) synthesized by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) have been fabricated as electrical double layer capacitors (EDLCs). The relatively open morphology of the films provided good frequency response, but had limited capacitance compared to present day activated carbon EDLCs. The objective of this research was to improve the capacitance of these films to a commercially viable level while maintaining sufficient frequency response for AC filtering. The growth of VOGN on Ni and Al substrates has been studied in this work. The native oxide on Ni was thinned at temperatures above ~600ºC with the oxygen from the surface oxide dissolving into the bulk, thus creating a low resistance ohmic contact that reduced the overall equivalent series resistance (ESR). Aluminum was studied because it is the primary substrate material used in electrolytic capacitors. However, it was much more difficult to work with because of its tenacious surface oxide. The maximum capacitance for a 10-minute VOGN/Ni growth observed was ~260µF/cm2, at temperature 850ºC, at 120 Hz, but the morphology was not very ordered. The best combination of capacitance (~160 µF/cm2) and frequency response (phase angle near -85º up to ~3000 Hz) was grown at 750ºC. The capacitance of VOGN/NI was further improved by using coatings of carbon black by an aerosol spray method. A capacitance of 2.3 mF/cm2 and frequency response phase angle near -90º at 120 Hz was achieved. It is the highest specific capacitance for an EDLC, reported in the literature, to date, suitable for AC filtering. Employing Al as a substrate required a novel method of plasma sputter cleaning of the oxide near the Al melting point (660ºC) and superimposing VOGN growth to prevent further oxidation. Initial results were ~80 µF/cm2 at a temperature of 620ºC with frequency response phase angle near -90º. Modeling of a uniform coating of carbon black (100 nm thick) on this underlying VOGN/Al architecture suggests that a capacitance of near 50 mF/cm2 can be achieved thus making this a potentially viable replacement for electrolytic capacitors. Another approach to commercialization of VOGN/Ni EDLCs has been studied by using a single substrate sheet interdigitated pattern design to create a low volume capacitor. A YAG laser was used to ablate resistance lines in the film resulting in a sinuous, square pattern on a VOGN/Ni coated alumina substrate and utilizing a gel electrolyte to create the EDLC.

Motivated by the need for inexpensive, simple, and portable devices for aqueous chemical analysis, we developed a nanoplasmonic colorimetric sensor capable of direct detection of wide range of chemicals. This novel sensor exploits the plasmonic resonance of metallic nanostructures with natural light to transduce changes in the chemical environment to changes in color, thus offering a simple route for real-time, in-situ, and low-cost analysis of aqueous chemical species. Due to its environmental and medical relevance, we chose aqueous ammonia to analyze and determine the efficacy and limit of detection of this sensing platform. For the metallic nanostructures we selected aluminium for its well stablished high reactivity with ammonia. However, the nanoparticle's metal can be chosen based on its reactivity with any given target analyte, therefore creating a tailorable sensor. The work here sets the foundations for a comprehensive analysis which aims to establish how various nanoparticle materials can be used to make a selective biosensor for chemical analysis in aqueous matrices such as environmental water samples, urine, blood serum, and saliva. In this thesis, we discuss the physics behind the sensors structural color, and the analytical techniques developed for ammonia quantification from aqueous solutions.