Search

A nascent instrument called Synchrotron X-ray Scanning Tunneling Microscope(SXSTM), which challenges the limits of conventional X-ray absorption spectroscopy(XAS) methods by accessing elemental and chemical details of matter at the ultimate atomic limit, is employed in this dissertation to observe and investigate the magnetism at the ultimate atomic limit.First, a series of X-ray Magnetic Circular Dichroism (XMCD) signals deducedfrom near field XAS signatures in SXSTM tip channel are used to observe surfacemagnetism in Ni islands grown on Cu(111) while that of the sample channel is used to identify ensemble magnetism. We observe that the magnetic moments at the surface are enhanced compared to that of the sample. A comparative study also reveals that the magnetic moments of a magnetized sample are elevated compared to that of a nonmagnetized sample.In this work we establish the first ever detection of magnetism at the ultimateatomic limit by capturing the XMCD signature of an Eu atom caged in pcam ligandswhich are adsorbed on top of magnetized Ni islands on Cu(111), hence displayingmagnetism due to a Van-Vleck like effect while coupling ferromagnetically to the host Ni layers. Differential conductance (dI/dV) measurements backed with theory demonstrate that the Eu3+ becomes magnetic by transitioning into a non-zero total angular moment(J>0).Dimer molecules are formed with a mixture of two different precursors containingEu and Tb in this dissertation, using Ullmann reactions on Au(111) which exhibitdifferent chirality and various types of clustering upon dimer formation, while sequences of near field XAS point spectra provide evidence towards dimers with different as well as similar rare earth (RE) atoms caged in the same dimer. They further reveal that both Eu and Tb are preserving their original +3 oxidation state in the dimers. We also report the first-ever radiograph of a single atom by means of X-ray images carried out at M5 edges of Eu and Tb in near field synchronously with STM images. The findings are revolutionary themselves while possessing the potential to revolutionize research areas such as single-molecule magnets (SMM), by successfully investigating magnetism at the ultimate atomic scale.

Ultrasound (US) is safe and low-cost relative to other imaging technologies, making it an increasingly popular diagnostic modality. US contrast is often limited by relatively low differences in acoustic impedance in the body, necessitating the use of contrast agents like microbubbles (MBs; ~1-10 µm diameter) which are intravenously injected and used to compensate for low contrast in conventional B-mode US imaging. The large size of MBs, however, limits their applications to the blood pool. In many diseases, including cancer, information beyond the blood pool is needed for diagnosis and staging. For instance, in many cancers (e.g. prostate, mammary, ovarian etc.), tumors are characterized by high vascular permeability and low lymphatic drainage, which increases the potential for enhanced permeability and retention (EPR) of macromolecules (~200 nm). When present, EPR leads to the tumor-localized accumulation of nano-agents. Nanobubbles (NBs) are new-age submicron bubble agents (100-500 nm diameter) capable of extravasation beyond the vascular network while providing enhanced US contrast similar to MBs. Recently, our group showed that active targeting of NBs to prostate specific membrane antigen (PSMA) rapidly and selectively enhances tumor accumulation and retention. These processes were visualized in real-time with clinical US. This project established NBs as a sensitive detection tool in the diagnosis of PSMA-positive prostate cancer due to localized NB accumulation, reduced diameter and higher number density (NBs per volume) of NBs compared to MBs of similar composition. Together, these points enable: 1) contrast visualization of small capillaries with higher fidelity, and 2) imaging of extravascular cellular targets reached via extravasation of NBs in leaky blood vessels while employing 3) a safe and widely accessible imaging modality. Together, contrast enhanced ultrasound (CEUS) using NBs (NB-CEUS) is a detection method with high biocompatibility and high safety profile. Despite these benefits, NB use in US imaging has yet to reach its full potential. US systems are optimized for MB use leading to potentially limited contrast enhancement and elevated rates of NB destruction. Additionally, extravasation results in a time-dependent loss of vessel visibility as contrast increases beyond the vascular network. As such, review of such videos is time-consuming and requires close supervision to determine the presence of EPR. Suboptimal imaging parameters and extensive imaging and analysis periods are significant burdens that directly impede clinical implementation of NB US contrast agents. There is therefore a need to produce an imaging suite using appropriate US imaging parameters (pressure and frequency) and develop improved methods for assessing vascularization and perfusion of tissue without significant burdens on time and cost. Such a tool could be used not only for tumors, but for all diseases involving pathologically permeable vasculature. With this goal in mind, the objective of this thesis is to work toward development of an optimized, real-time method for evaluating vascular permeability over the entire tumor using novel NB-CEUS techniques.This work builds upon dynamic CEUS protocols used clinically with MBs. NBs, which are 100-500 nm in diameter, are approximately 10x smaller than MBs and have been shown to extravasate into the tumor interstitium. To reach the final objective of this work, NB enhancement under a fully characterized commercially available US system must be studied. To this aim, in vitro studies concerning NB backscatter and decay based on pressure and frequency US parameters were first performed. This involved evaluating changes in NB-CEUS intensity and frequency data for establishing high contrast, low decay signal from NBs. To the second aim, we proposed to develop NB-CEUS mapping to decouple localized agent accumulation which occurs in the presence of EPR. The method enabled accurate separation of extravasated NBs located in deep tumor tissue from intravascular NBs. Visualization of the vascular network and heterogeneity of the tumor core was achieved in tandem. Currently there is no clinical imaging method for distinguishing between tumor-accumulated (slow/stationary) NBs and intravascular (flowing) NBs with sufficient sensitivity. Using prostate cancer as a testcase, we improved the delineation of prostate tumors through the separation of stationary from moving NB agents when perfused from the vasculature of solid tumors. The work in this thesis represents a new approach for CEUS using NBs to characterize tumoral microenvironment characteristics like vascular permeability. Overall, the successful implementation of this work would directly address the need for a rapid and accurate assessment of the heterogeneous physiology of pathologically leaky tissue.

There is a continuous thrust for cleaner and more sustainable alternatives for energy conversion with the increasing global energy demand. Among them, photovoltaics, specifically thin film solar cells are highly promising and are one of the fastest growing clean energy technologies in the United States. This research presents the synthesis and characterization of a set of novel multinary copper chalcogenide semiconductor nanocrystals (NCs), CuZn2ASxSe4-x consisting primarily of earth-abundant elements for applications in photovoltaic devices. A modified hot-injection method was used to synthesize these semiconductor NCs containing both S and Se chalcogens. The novelty of the new semiconductor NCs lies in the incorporation of multiple cations as well as two different chalcogen anions within the crystal lattice, which is an achievement from the materials synthesis aspect. The composition-controlled optical and photoluminescence properties of the CuZn2ASxSe4-x NCs were investigated via multi-modal material characterization including x-ray diffraction (XRD), ultraviolet-visible (UV-vis) spectroscopy, and photoluminescence spectroscopy (PL). The crystal structure, as determined from the XRD primarily consisted of the metastable wurtzite (P63mc) phase. The NCs exhibited direct band gap in the visible range that could be tuned both by varying the group III cation within the composition as well as the ratio of S/Se, based on the Tauc plot obtained from the UV-vis characterization. This work lays the groundwork for future investigations into the practical applications of copper chalcogenide NCs in solar energy conversion.

For high capacitance density multilayer ceramic capacitors, high dielectric constant and lead-free ceramic nanoparticles are highly desired. Lead-free barium titanate (BaTiO3 or BTO) nanocrystals (NCs) represent an important class of such nanodielectrics. In Chapter 1, we have reported a systematic investigation into the crystal structure-dielectric property relationship of combustion-made BaTiO3 nanocrystals. Our results reals that the “size effect” of the nanoparticles seemed not that simple. Although the X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy could not identify the exact structural defects due to the technical difficulties of sample preparation, we resolved the contradictory phase assignment from XRD and Raman analysis and discussed the understanding that surface and bulk defects formed during synthesis affect the final crystal structures and thus dielectric properties of BTO nanocrystals with different sizes. The combustion-made BTO nanocrystals exhibited a low dielectric constant up to ~300, which is much lower than that (~1000) of the multi-domain BTO (001)-SC. In Chapter 2, we have introduced a theoretical deconvolution method for analyzing polarization-electric field (P-E) loops from the polymer/nanoparticle nanocomposites. We have prepared PVP/BTO nanocomposite films as PVP film with different volume fractions of BTO nanoparticles (20-40 vol%) at room temperature via spin-coating. Surprisingly, broad ferroelectric P-E loops for PVP/BTO60 nanocomposites were yielded when the volume fraction of BTO60 was above 30 vol%, even though neither the PVP matrix nor the BTO ceramic nanoparticle exhibits any intrinsic ferroelectricity. Using a theoretical deconvolution of the broad P-E loops based on the Langevin-type function, three contributions were identified. First, deformational polarization generated the linear dielectric constant of nanocomposites, from which the linear dielectric constant of BTO60 nanoparticles (80-100) was extracted using the Bruggeman mixing rule. Second, slim paraelectric P-E loops were obtained for the BTO60 nanoparticles. From the saturated polarization, the electric field-induced permanent dipole moment per unit cell was estimated to be 0.07-0.2 D at a poling field of 20-100 MV/m, which was significantly smaller than the dipole moment (5.3 D) of the tetragonal unit cell of BaTiO3, indicating the paraelectric nature of BTO60 nanoparticles. Third, strong particle-particle dipolar interactions induced transient ferroelectric domains among the high dielectric constant BTO60 nanoparticles, particularly when the poling electric field was high. The third contribution dominated the overall polarization process and thus accounted for the abnormal ferroelectric behavior for the linear dielectric polymer/paraelectric ceramic nanoparticle composites. In Chapter 3, we have further extended the deconvolution method to a robust route to extracting Pp-Ep loops of ferroelectric nanocrystals from the polymer/ceramic nanocomposites. To date, no quantitative P-E loops have been attained for a single ferroelectric nanocrystal using a direct measurement (e.g., piezoresponse force microscopy). Herein, we report on nonlinear ferroelectric characteristics for BTO NCs via a polymer nanocomposite approach. Using different mixing rules and nonlinear dielectric analysis, the overall dielectric constants of BTO NCs were obtained, from which the internal field in BTO nanoparticles (Ep) was estimated. Consequently, the Pp-Ep hysteresis loops were yielded for the BTO380 and BTO60 NCs. Interestingly, BTO380 exhibited square-shaped ferroelectric loops, whereas BTO60 displayed slim paraelectric loops. In addition, strong particle-particle interaction was identified for both nanocomposites at high packing fraction, which led to significant nonlinear dielectric loss.

Multispectral materials are of great need in advanced applications in electronics, camouflage, personal clothing, and space missions. Consequently, substantial effort has been made over the years to design materials of complex functionalities enabling them to perform within either one or both visible and infrared electromagnetic ranges. Nonetheless, many of these multispectral materials are limited by their scale and restricted tunability as well as challenges related to their functionalities in different wavelength ranges forcing a settlement on compromised properties. To address these challenges, we drew inspiration from cephalopods, the marine masters of light. Their astounding ability to dynamically tune their optical appearance is possible due to the complex skin structure composed of chromatophores and iridophores splotches providing pigmentary and structural coloration, respectively. From these, we first developed large-area chromatophore-inspired adaptive infrared and thermoregulatory materials featuring on-demand infrared transmittance modulation for over 20-fold accompanied by heat flux by over 30W m−2¬ when mechanically actuated. Next, we modified our chromatophore-inspired composite materials and broadened their wavelength functionality by enhancing them with visible wavelength-selective, splotch-inspired structures and obtaining hybrid multispectral composite materials of maintained infrared transmittance modulation of over 20-fold and additional visible reflectance modulation of over 9-fold upon the mechanical actuation. Altogether, our findings demonstrate a successful design and fabrication of multispectral thermoregulatory materials with tunable functionalities which can find application in advanced systems such as wearable electronics, thermal-management systems, smart windows, and multispectral camouflage.

Artificial spin ices (ASIs) are lithographically-patterned arrays of interacting magnetic nanoislands which have traditionally been designed such that each nanoisland possesses an Ising-like magnetic configuration (i.e., behaves as a bar magnet). These systems were originally introduced as an engineered analog of spin-ice crystals whose atomic-level magnetic ordering could be emulated and visualized with conventional magnetic microscopy techniques. Since this initial study, ASIs have served as a platform for designing and investigating phenomena including phase transitions between different global magnetic ordering states, magnetically-reconfigurable spin wave dynamics, and computation in nanomagnet-based devices.Many ASI studies have used Ni80Fe20-based nanoislands whose material and geometric properties enforce the formation of uniform, Ising-like magnetizations in each nanoisland. While these systems have facilitated the investigation of magnetic ordering phenomena in various array geometries, ASIs fabricated from ferromagnetic complex oxides offer opportunities to explore how the nanoisland material properties and magnetostatic interactions can influence the behavior of the individual nanoislands and ASI as a whole. Understanding how these magnetic parameters can tailor the nanoisland functionalities will be essential in the development of nanomagnet-based computing devices.This dissertation focuses on ASIs fabricated from the ferromagnetic perovskite oxide La0.7Sr0.3MnO3 (LSMO) to understand how the interaction between magnetostatically-coupled nanostructures can influence the formation of spin textures. Soft x-ray photoemission electron microscopy (X-PEEM) was used to perform magnetic domain imaging of LSMO-based ASIs. Through these imaging studies, these systems were observed to allow the formation of both Ising states, observed in traditional ASI systems, as well as complex spin textures (CSTs), comprised of single and double vortices. The formation of these different spin texture states were found to be sensitive to the ASI geometry as well as the magnetization of the neighboring nanoislands. Through the use of micromagnetic simulations, an energetic analysis of the system was performed which revealed how spin texture formation arises from a competition between effects intrinsic to each nanoisland as well as the magnetostatic interaction between adjacent nanoislands. This competition is facilitated by the unique combination of magnetic material properties of LSMO. The unusual domains stabilized in LSMO-based ASIs also raises the question of the relaxation kinetics of CST-bearing ASI systems. Insights into the thermal relaxation behavior of LSMO-based ASIs was provided using X-PEEM and an in-situ pulsed annealing protocol which allows for “snapshots” of the time-dependent relaxation to be acquired. By tracking the domain changes in each nanoisland as a function of the annealing time, several types of apparent domain conversion were observed whose relative transformation rates evolved over time. These results suggest that the domain formation kinetics of each individual nanoisland is sensitive to the evolving magnetizations of the neighboring nanoislands. These static and dynamic studies of LSMO-based ASIs demonstrate how magnetostatic interactions can be used to tailor spin texture formations in these systems. Moreover, this work highlights the potential for material-driven ASI studies to provide deeper insights into ASI and domain formation physics.

Beta-phase gallium oxide (β-Ga2O3), with its ultrawide band gap energy (~4.8 eV), high predicted breakdown field strength (6-8 MV/cm), controllable n-type doping and availability of large area, melt-grown, differently oriented native substrates, has spurred substantial interest for future applications in power electronics and ultraviolet optoelectronics. The ability to support bandgap engineering by alloying with Al2O3 also extends β-(AlxGa1-x)2O3 based electronic and optoelectronic applications into new regime with even higher critical field strength that is currently unachievable from SiC-, GaN- or AlxGa1-xN- (for a large range of alloy compositions) based devices. However, the integration of β-(AlxGa1-x)2O3 alloys into prospective applications will largely depend on the epitaxial growth of high quality materials with high Al composition. This is considerably important as higher Al composition in β-(AlxGa1-x)2O3/Ga2O3 heterojunctions can gain advantages of its large conduction band offsets in order to simultaneously achieve maximized mobility and high carrier density in lateral devices through modulation doping. However, due to the relative immaturity of β-(AlxGa1-x)2O3 alloy system, knowledge of the synthesis and fundamental material properties such as the solubility limits, band gaps, band offsets as well as the structural defects and their influence on electrical characteristics is still very limited. Hence, this research aims to pursue a comprehensive investigation of synthesis of β-(AlxGa1-x)2O3 thin films via metal organic chemical vapor deposition (MOCVD) growth methods, building from the growth on mostly investigated (010) β-Ga2O3 substrate to other orientations such as (100), (001) and (-201), as well as exploring other polymorphs, such as alpha (α) and kappa (κ) phases of Ga2O3 and (AlxGa1-x)2O3 to provide a pathway for bandgap engineering of Ga2O3 using Al for high performance device applications. Using a wide range of material characterization techniques, experiments have been undertaken to investigate the physical structure, electronic and optical properties of Ga2O3 and (AlxGa1-x)2O3 films, with the correlation to theoretical studies. Al compositions in (AlxGa1-x)2O3 films are varied for the whole range in order to understand the phase segregation at higher Al compositions as predicted by equilibrium phase diagram as well as theoretical studies. The Si doping in β-(AlxGa1-x)2O3 thin films is investigated as a function of Al compositions, with a goal to identify the major challenges associated with MOCVD epitaxy β-(AlxGa1-x)2O3 films, such as the formation of cracks, increase of the concentrations of planer defects, carbon and hydrogen densities, which are predicted to act as compensating acceptors in β-(AlxGa1-x)2O3. In addition, the band discontinuities at β-(AlxGa1-x)2O3/Ga2O3 heterojunctions with various Al compositions are also determined along different orientations to understand the influence of substrate orientations on the band offsets. The growth of in-situ MOCVD Al2O3 dielectric on differently oriented β-(AlxGa1-x)2O3 films have been investigated to gain insights into how varying orientations and Al compositions influence the interfacial quality and the band offsets at Al2O3 dielectric/β-(AlxGa1-x)2O3 heterojunctions. Apart from β-(AlxGa1-x)2O3 epitaxy, the crystalline structure and quality of MOCVD grown single phase α-(AlxGa1-x)2O3 and κ-Ga2O3 films are also investigated for potential applications in high-power and high-frequency electronics. Such findings will greatly assist in designing and fabricating future high power heterostructure based electronic and optoelectronic devices.

Over the past several decades, nanomaterials have undergone significant improvements and developments. Among these, infrared nanomaterials have potential applications in fiber optics communications, night vision, and sensing, with PbS nanomaterials standing out as a particularly promising option. In this work, we explored two distinct techniques to enhance the light-emitting efficiency of PbS nanosheets: organic ligand passivation and inorganic shell encapsulation. For the organic surface passivation, we utilized tributylphosphine as a ligand. Meanwhile, for inorganic passivation, we designed a core/shell structure using PbCl2. To achieve this inorganic core/shell structure, we pioneered a robust synthesis method capable of producing orange nanoplatelets. Notable, both strategies led to a substantial increase in the photoluminescence quantum yield. Such nanosheets with augmented quantum yield could be pivotal in the evolution of photonic devices, encompassing light-emitting diodes, solar cells, and lasers.

Nanostructured hybrid materials can be formed using self-assembling side chains grafted to a polymer backbone. Small-angle X-ray and neutron scattering (SAXS & SANS) measurements on polyisobutylene graft copolymers with side chains containing β-alanine trimer have revealed that crystalline nanodomains form by self-assembly. Modifying the side chain chemistry allows one to tailor the β-alanine nanocrystal length from over 300nm down to approximately 10nm. The degree of crowding at the nanodomain interfaces impacts the temperature dependence of the microphase separation. Chemical variations in the side chains, such as removing C18 tails and adding C11 spacers between the backbone and β-alanine trimers have dramatic effects on nanocrystal size, domain spacings, order-disorder transition temperature and width of transition, crystal melting temperature, and bulk mechanical properties.The last chapter describes progress in defining the interface morphologies in blends modified with Interfacial Supramolecular Coupling Agents (ISCAs) containing β-alanine. Polyethylene (PE) and polypropylene (PP) constitute the majority of mixed plastic waste produced globally. In the approach studied, it is envisioned that a pair of ISCAs will populate the interfaces between PE-rich and PP-rich phases and anchor the phases together. From SAXS, SANS, Wide Angle X-ray Scattering (WAXS) and Atomic Force Microscopy (AFM) analysis it is evident that the presence of ISCAs alters the crystalline structure of the overall blend.

The objective of this thesis is to create highly efective light emitters for LiDAR technology by utilizing gain materials that are based on semiconductor quantum dots (QDs). The primary component of LiDAR technology is the light source, which is typically a laser. In order to function efectively under various conditions and with optimal efciency, the laser must meet specifc criteria: it should be safe for the eyes, provide high output power, exhibit thermal stability, and be insensitive to back-refections. QD materials possess advantageous properties such as three-dimensional carrier confnement and atom-like gain, resulting in discrete density of states. These properties contribute to an ultralow linewidth enhancement factor ‘α’, leading to improved thermal stability, reduced sensitivity to back-refection, narrow spectral linewidth, and low-chirp characteristics under modulation.This study focuses on the development of a light source using diode lasers for two specific LiDAR wavelengths: 905 nm and 1.55 μm. The choice of these wavelengths is based on their respective advantages. The 905 nm wavelength has the lowest absorption in the atmosphere, making it an excellent option for topographic LiDARs used in navigation and environmental sensing. On the other hand, the 1.55 μm wavelength is considered eye-safe because it is blocked by retinal water and protects the cornea from potential damage. The 905 nm emitting QDs are based on the GaAs material platform, while the 1.55 μm wavelength utilizes InP-based materials. The work conducted in this thesis starts with material design and progresses to optimizinggrowth conditions to achieve high-density and uniform QD ensembles. Subsequently, these QDs are implemented into the epitaxial structure of diode lasers, which are then fabricated and characterized to ensure thermal stability and insensitivity to back-refection.The wavelength regime commonly referred to as the ‘Telecom band’ is centered at1.55 μm has well-established growth technology for QDs, exhibiting a remarkably low full-width at half maximum (FWHM) of 17 meV, which indicates a high level of uniformity. This research presents the development of QD laser diodes that achieves a moderately high output power exceeding 100 mW, demonstrating excellent thermal stability with wavelength coefficient of less than 0.4 nm/K in the temperature range of 0-80°C. Furthermore, the laser exhibits a high characteristic temperature (T0) of 100 K. A comprehensive comparison is conducted between the QD-based materials and similar materials based on quantum wells (QWs) in terms of their optoelectronic properties. The design and fabrication processes are optimized to produce diode lasers that operate in true single mode, making them suitable for practical applications.The wavelength of 905 nm is not widely explored in the QD research community. In this study, we investigated the growth of QDs on a novel InAlGaAs-based quaternary material system. Various growth conditions were employed to manipulate the morphology and composition of the QDs. Our research reveals a wide tuning range of 700 nm to 1.1 μm for the growth window of these QDs. The impact of ex-situ thermal annealing was extensively examined, and it was discovered that the material quality signifcantly improved with the application of annealing. Subsequently, the optimized materials were incorporated into the active region of diode lasers, and diagnostic lasers were fabricated and tested. The results from these experiments were used to further optimize and fine-tune the growth conditions of the materials to achieve the desired emission wavelength and superior optoelectronic performance. Additionally, new strategies were developed to create single-mode lasers. This work establishes a fundamental basis for selecting laser materials suitable for LiDAR technology applications.

This dissertation discusses several novel synthesis methods for epsilon-WO3 (ε-WO3) and hexagonal WO3 (h-WO3). The ε and h phases are important materials as they have variety of application in catalysis, gas sensing and battery. However, these two phases are metastable phase, which increases the difficulties to stabilize it at room temperature. The work in this dissertation will focus on exploring reliable synthesis methods for these two phases.Synthesizing the h-WO3 has been widely explored and the most common method to obtain h-WO3 is hydrothermal methods. However, a big problem of hydrothermal methods is that the alkaline ions or ammonia ions are needed to stabilize the hexagonal structure. In other words, it is almost impossible to obtain pure h-WO3 through hydrothermal methods. The purity of materials can affect the its properties. For example, the sodium doping in h-WO3 might affect the gas absorption, thereby influencing the gas sensing properties. Solvothermal synthesis can largely avoid the contamination of alkaline ions or ammonia ions. But the solvothermal synthesis is not well understood yet. The work in this dissertation focusses on solvothermal synthesis of h-WO3. The effect of synthesis parameter is explored and a reliable synthesis route has been put forward. Furthermore, the material has been suggested to be a promising isoprene sensor. As for ε-WO3, it is the only ferroelectric phase in WO3 polymorphs. However, it is believed to only be stabilized by rapid solidification processing. The phase stability of ε-WO3 is still not well-understood. This dissertation assesses the effect of surface energy and elemental doping toward the phase stability of ε-WO3. The result suggests the increase of surface energy will decrease the stability of ε-WO3. A size-temperature-stability diagram has been mapped out by conducting in-situ cryogenic Raman characterization. As for elemental doping, the Cr and Ti doping is found to be able to stabilized ε-WO3 and a reliable synthesis route involving Cr and Ti doping has been put forward. The maximum of ε fraction is ~69% for Cr doping and the ~87% for Ti doping. The XPS spectra has suggested that Cr and Ti doping decrease the amount of oxygen vacancies, suggesting that some Cr and Ti might go into the interstitial sites of WO3.Finally, a laser-based synthesis method for ε phase is proposed. The rapid melting and cooling process are believed to be the reason that stabilized the ε structure. After laser processing, the epsilon fraction further increases and even reach to 100%. These results clearly indicates that it is feasible to produce ε phase via additive manufacturing and 3D printing techniques.

Breakthroughs in nanotechnology and nanomedicine are driving researchers to create novel, precision-medicine based approaches. These advancements can be specifically tuned for various applications, such as treating peripheral nerve injury. Appropriate functioning of the nervous system is tremendously important to overall quality of life. The nerves within our body branch from the spinal column and can extend up to one meter away. Peripheral nerve injuries are a common occurrence and can readily heal in most cases. These injuries come in many flavors and can be targeted at various levels. Therapeutics can be developed to target the soma that can be in the spinal cord (motor neurons) or in the dorsal root ganglia (sensory neurons), intervene locally at the direct site of injury, or target the downstream aspects at the nerve terminals. The work described later will focus on aspects of treating the local injury through a sciatic nerve crush model, maintaining the downstream health of skeletal muscle, and developing strategies to provide immune protection to cellularized nerve allografts. The work discussed within utilizes the tissue nano-technology platform developed by Dr. Gallego-Perez and team to deliver plasmid DNA cargos to intact nerves, skeletal muscle, and nerves for transplantation. We hypothesized that 1) the local induction of endothelial cells in a crush model can lead to more rapid functional recovery through an earlier restoration of vascularization, 2) the delivery of neurogenic factors to skeletal muscle can locally induce neurons to re-innervate the motor endplates and extend the muscles window to remain functional once complete regeneration can occur, and 3) TNT delivery of Fas ligand can mitigate immune cell invasion to grafted nerve tissue to avoid apoptosis of the needed cell populations and to prevent host rejection. Goal one uses a plasmid cocktail containing Etv2, Fli1, and Foxc2 (EFF) that has previously been validated to reprogram fibroblasts into endothelial cells within one week. TNT has previously been demonstrated to work in mouse skin. The applications discussed within this work focused on the translation of this approach to nerve tissue. As such, in addition to evaluating the impact of endothelial cell reprogramming, the optimization of transfection parameters is a large focus in answering our first hypothesis. In looking at downstream impact of nerve denervation, we sought to develop strategies aimed at maintaining muscle health as axons regenerate across the great distance they cover. In humans, the terminal location of nerves can be up to one meter or three feet away from the cell body. Tissues and organs existing beyond ~18 inches away from the nerve body, are highly susceptible to poor reinnervation outcomes and long-term detriments. A contributing cause for these deficits is the slow growth rate of the axons (1-2mm/day or 1 inch/month). Literature has reported that human skeletal muscle can remain receptive to reinnervation for 18-24 months. Current intervention strategies are focused on addressing the injury along the nerve bundle and developing methods for more complete regeneration. A shortcoming of these approaches that we sought to address is extending the window that skeletal muscle is responsive to reinnervation once the process is completed. Thus, the primary goal discussed in Chapter 3 centers around an approach to locally induce neurons, through cell reprogramming, capable of synapsing on the motor endplates as a strategy to preserve the muscle in a healthy state. From the two hypotheses and goals of Chapters 2 & 3, there is a demonstrated need for new local and downstream interventions. Another plausible intervention strategy for injuries disrupting the integrity of the nerve, is the inclusion of nerve grafts. The gold standard, when available, is to source nerve segments from another region of the body. The use of nerves from the patient (autograft), is a great strategy as the cells, vasculature, and other components remain intact to support regeneration. When the gap defect is too larger (>5 cm), nerves can be taken from other sources (i.e., cadavers). The use of cellularized grafts from other than the patient includes the requirement for immunosuppressant drug usage from weeks up to two-years based on time for regeneration and function to be restored. Developing a strategy to eliminate the need for long-term drug use while allowing the use of cell-laden nerve segments from other donors can greatly improve outcomes and lower overall costs of transplants. The work to be discussed covers a variety of approaches for peripheral nerve injury. While focused on this one field of medicine, TNT has great potential beyond treating nerves. Additionally, when demonstrating efficacy in these various tissues, we can begin thinking of delivering other cargos and enhancing repair in other conditions. Specifically, the ability to locally deliver cargos to mitigate the immune response and limit host rejection has great implications for the transplant world. Enjoy!

For over several decades, research on plasmonics has been of great interest due to its applicability in many fields. The use of metallic nanoparticles to manipulate incident light allows the advancement of sensing, cloaking, heat transfer and chemical reactions. This dissertation presents the study of the light-matter interaction corresponding to a variety of nanostructures due to the excitation of plasmons. Included, is the computation of optical properties of single nanoparticles and periodic arrays of nanoparticles in the visible spectrum with the purpose of understanding and describing the different processes that occur due to the absorption of light. These processes include interband and intraband transitions and surface scattering, all of which occur from the absorption of light. The last process mentioned is of great interest in the generation of hot electrons, which could be capable of overcoming an energy barrier and get transferred to another materials. This transfer of hot electrons could be used to accelerate chemical processes like photocatalysis. Additionally, the optical properties of nanofluids containing nanobars are presented tomanipulate the response to light in the infrared. The main objective is to block specific ranges of wavelengths by combining nanobars of different lengths. We additionally studied multiple materials to find a cheaper alternative to gold. The combination of theoretical and computational methods were used throughout this study and in some cases, they are complemented by experimental results in the literature. The final objective of this dissertation is to describe and propose novel methods and approaches to further understand the plasmonic response of these nanostructures.

The persistent demand for flexible and wearable electronic components in healthcare, aerospace, media, and transit applications has led to a significant shift from traditional electronics processes to printed electronics. Printed electronics are anticipated to establish itself as the industry's dominant force due to their enhanced flexibility, rapid prototyping capabilities, and seamless integration with everyday objects. They are cost-effective and have the scalable option for large-scale production because additive manufacturing techniques are used. Among the various printing methods available, inkjet printing has recently gained popularity for printing electronics, especially capacitors that require precise and complex structures on different substrates. Inkjet printing relies on micro dispensing additive technology, where liquid phase materials are dispensed using the drop on demand (DOD) technique with conductive nanoparticle inks. Researchers have made several attempts to fabricate fully inkjet-printed composite capacitors and have discovered that the permittivity value of the composite increases compared to a polymer. This suggests that using composites as the dielectric material in a capacitor can potentially increase the capacitance value. However, despite the discussion on various composite dielectric materials, there is a scarcity of information on the use of BaTiO3/SU-8 dielectric materials for capacitor applications. To address this gap, the objective of this study is to formulate BaTiO3/SU-8 ink suitable for inkjet printing and develop a printing process for layered metal insulator metal (MIM) structures. The formulated BaTiO3/SU-8 ink is employed to print the dielectric material, while nano silver ink is used for the two electrodes, enabling the fabrication of the capacitor in a single step. The study takes into account volume and speed jetting parameters as well as waveform to achieve optimal and uniform liquid phase material inkjet printing on the substrates. The thickness of the printed layers is measured using a profilometer, and the sheet resistance of the inkjet printed nano silver conductive ink is evaluated using a four-point probe. Furthermore, the dielectric properties of the printed composite are characterized by measuring the capacitance value. The main goal of this paper is to provide insights into the formulation of BaTiO3/SU-8 dielectric materials and understand the processes involved in the fabrication of a full inkjet printed composite MIM capacitor. Additionally, the experimental results will be compared with theoretical models of BaTiO3/SU-8 dielectric developed by our research group. The successful development of inkjet printed composite MIM capacitors using BaTiO3/SU-8 dielectric materials has the potential to revolutionize the field of printed electronics. The ability to print capacitors with higher capacitance values and complex structures on flexible substrates opens up new possibilities for the integration of electronics into various applications. This research makes a valuable contribution to the expanding knowledge base in the field of inkjet printing for electronics, laying the foundation for future advancements in flexible and wearable electronic devices.

Microorganisms, particularly flagellated bacteria, have inspired the development of microswimmers, which are microscale robots designed for fluid environments. They can be self-propelled or externally controlled and find applications in biomedicine, including drug delivery, biosensing, and microsurgery. At the microscale, where inertial forces are negligible, viscous forces become dominant, requiring specialized simulation methods. Molecular Dynamics (MD) simulations offer a suitable approach by representing complex systems as particle interactions and have been extensively used for studying various systems. In our research, we employ a 3D model of a swimmer-channel system, departing from previous 2D representations, to analyze the intricate dynamics between microswimmers and their fluidic environment. Our analysis provides valuable insights into microswimmer behavior and enables us to recommend optimal design strategies. Additionally, we utilize interaction networks as a Machine Learning technique to predict microswimmer behavior based on MD simulation results. This work paves the way for further advancements in the study and application of microswimmers, contributing to scientific progress in this field.

In the future, well-engineered and optimized flexible electronic devices will be woven into everyday accessories such as clothes, furniture, safety, and healthcare monitoring devices. Dynamic polymer nanocomposites (DPNs) are an excellent class of materials that have a huge potential in the future of flexible electronics. DPNs are achieved through macromolecular engineering of dynamic polymers enhanced with electrically conductive nanofillers or nanocomposites with self-healing capabilities enabled via dynamic chemical linkages. Integration of multiple types of dynamic linkages into one polymer network is challenging and not well understood especially in the design and fabrication of DPNs. This dissertation presents facile methods for synthesizing flexible, healable, conductive, recyclable, and thermoresponsive DPNs using three dynamic chemistries playing distinct roles. Dynamic hydrogen bonds account for material flexibility and recycling character. Thiol-Michael exchange accounts for thermoresponsive properties. Diels-Alder reaction leads to covalent bonding between polymer matrix and nanocomposite. Overall, the presence of multiple types of orthogonal dynamic bonds provided a solution to the trade-off between enhanced mechanical performance and material elongation in DPNs. Efficient reinforcement was achieved using

Reactive oxygen species (ROS), which are principally responsible for cell damage under x-ray sources, are generated more abundantly in the presence of gold nanoparticles (AuNPs), enhancing the effect of radiation in biological models. The uncoated AuNPs exhibit a tendency to agglomerate in the presence of salt, ubiquitous in cell culture media, serum, and plasma. Thus, appropriate surface coatings are necessary for use in clinical applications. We hypothesize that biocompatible coating on AuNPs may augment ROS generation and ultimately cause more damage to the cancer cells. Here we examine the effectiveness of silica coating AuNPs surface (Au@SiO2), polyvinyl alcohol (PVA) coated AuNPs and bovine serum albumin (BSA) coated AuNPs, comparing the ROS production efficiency under MV x-ray irradiation in in vitro such as aqueous solutions of Au@SiO2 NPs, Au@PVA NPs, Au@BSA NPs, uncoated AuNPs, and water-only samples as well as using MCF-7 and BT-20 cell media loaded with Au@SiO2 NPs, Au@PVA NPs, Au@BSA NPs and uncoated AuNPs.

In many chronic inflammatory diseases, the vascular endothelium becomes pathologically permeable due to conditions like angiogenesis and production of growth factors and inflammatory cytokines (e.g., histamine, bradykinin, etc.). In cancer, this process can be exploited for delivery of nanoparticles to tumors via the enhanced permeability and retention (EPR) effect. However, nanoparticle-based therapeutics reliant on the EPR effect have led to inconsistent results in patients. This is due to many factors, with a significant one being heterogeneous tumor vascular architecture and morphology both between patients and within a single tumor. Transport of the nanoparticle to the tumor and into the parenchyma is complicated by uptake by the immune system, ineffective margination, and inefficient extravasation. Guidance is needed to inform clinicians on what therapies may be most effective for each patient. Effective guidance could reduce health-care costs and negative side effects of medication. An inexpensive, safe, non-invasive, and real-time imaging method that has high temporal and spatial resolution may be capable of categorizing the extent of vascular permeability in tumors and once validated, personalize therapeutic regimens for patients. Such a tool could be used not only for tumors, but for all diseases involving pathologically permeable vasculature. With this goal in mind, the objective of this thesis is to work toward development of a real-time method for evaluating vascular permeability over the entire tumor using novel nanobubble (NB)-based contrast-enhanced ultrasound (CEUS).This work builds upon dynamic CEUS protocols used clinically with microbubbles (MBs). NBs, which are 100-400 nm in diameter, are approximately 10x smaller than MBs and have been shown to extravasate into the tumor interstitium. To reach the final objective of this work, NB dynamics from intravenous injection to retention in the tumor must be studied. To this aim, in vitro studies concerning NB backscatter and kinetics based on their cellular environment were first performed. These include NB interactions with human whole blood (i.e., NB-red blood cell adsorption) and the difference in NB-CEUS generated data when comparing NBs flowing through a vessel versus those diffusing through an extracellular matrix. The results from the in vitro work were then applied to an in vivo mouse tumor model where time-intensity curve and decorrelation time parameters were used to differentiate tumors with high and low potential for nanoparticle extravasation. Decorrelation time was compared to the intratumoral distribution of a doxorubicinloaded liposome and found that it was a potential parameter to assess nanoparticle extravasation and retention. The work in this thesis represents a new strategy for companion nanoparticles using NB-CEUS to characterize tumoral microenvironment characteristics like vascular permeability and nanoparticle retention to predict the heterogeneous distribution of therapeutic nanoparticles. These findings could lead to the use of personalized medicine for all patients receiving a nanomedicine treatment and could be potentially applicable to other pathologies involving pathologically permeable vasculature.

The main purpose of this study is to assess the relationship between cannabis use and impulsive risk-taking in undergraduate binge-drinking students. These relationships were assessed on the basis of gender and severity of cannabis use disorder symptoms. These relationships were discussed through a psychological, biological, and sociological lens.

Bulk VO2 undergoes an insulator-to-metal transition (IMT) with up to five order of magnitude change its resistivity at 340 K. However, when VO2 is deposited as a film on a substrate, the strain from the substrate can alter the IMT temperature, resistivity ratio, and hysteresis. Here, we present single-phase VO2 ultrathin films (thick- ness less than 20 nm) grown using oxygen plasma molecular beam epitaxy (MBE) on TiO2(001) and Al2O3(0001) substrates. First, we modify existing recipes employing ozone MBE and reproduce the best reported films on TiO2(001); maintaining an almost three order of magnitude transition in a 12 nm thick film. We then extend our recipe to Al2O3(0001) substrates where we stabilize a 12 nm thin single-phase VO2 film and observe a two order of magnitude transition, expanding the possible growth methods for ultrathin VO2 films on Al2O3(0001). In a separate, approximately 10 nm thick VO2 film on TiO2(001), we use non-contact AFM (nc-AFM) to track electronic properties across the expected temperature range of transition. We first observe a change in the work function of VO2 at the expected bulk transition temperature. We then measure the frequency shift and dissipation at varying bias and tip-sample separation at seven stable temperatures, spanning the insulating to the metallic state. Using the frequency shift data, we ex- tract the tip-sample capacitance, then calculate the induced carrier doping within the sample as a result of the proximity of the tip. The work function, carrier density, and damping results above and below the IMT suggest that we observe the IMT; with the damping in particular showing consistent behavior with a decrease in resistance starting as low at 270 K and continuing to 300 K. Furthermore, we observe a change in work function at fixed temperature at close tip-sample separation as low as 240 K, along with elevated damping, suggesting the electric field from the tip itself may be initiating the transition, at least in the surface of the film, at temperatures as low as 240 K in the close tip-sample separation regime.

Macroions are unique charged species with a size of usually 1 – 6 nm. When dissolved in polar solvents their solution behavior cannot be explained by Debye-Hϋckel theory or DLVO theory which are used to describe solution behavior of simple ions and large colloids, respectively. Several charged nano-sized species can show macroionic solution behavior including polyoxometalates (POMs), metal-organic cages (MOCs), dendrimers, functionalized fullerenes and cyclodextrins, etc. In a dilute solution when macroions carry moderate charges, they can self-assemble into single-layered, hollow, spherical supramolecular structures, called blackberry structures, via counterion-mediated attraction. Chirality is an intriguing part of biological molecules such as amino acids and sugars. There is only one enantiomer of these basic biomolecules (e.g., L-amino acids or D-sugars) in nature that self-assemble into homochiral biomacromolecules. Homochirality is a mysterious part of the origin of life and a topic still under exploration. However, self-assembly of biomacromolecules is very complex due to interference of several intermolecular interactions and species; therefore, a simpler self-assembly model, such as that of macroions, can help us to gain deep insight into the mystery behind homochirality of biomolecules.In this dissertation, self-assembly of chiral Pd12L24 MOCs based on alanine into blackberry structures at the presence of alanine-based chiral counterions is studied. It is shown that D and L counterions have significantly different impact on the self-assembly behavior of D (or L)-Pd12L24 macroions due to their different binding behavior; i.e., chiral discrimination exists. Next, we use chiral Pd12L24 MOCs based on alanine, valine, and leucine in which hydrophobicity of the side group of the amino acid increases from alanine to leucine. In this case, chiral discrimination disappears when chiral counterion, based on amino acids, possesses a more hydrophobic side group then the amino acid in the structure of MOC. Then, self-assembly of functionalized gamma cyclodextrins to blackberry structures is studied when D- and L-alanine methyl ester (a chiral counterion based on amino acid) and D- and L-glucosamine (a sugar-based chiral counterion) is studied. Glucosamine possesses a stronger binding to the macroions and also a more intense chiral discrimination can be observed than alanine methyl ester. Lastly, we will study the self-assembly behavior of Pd12L24 MOCs in which a free central pyridine can accept up to 24 Ag+ ions leading to higher surface charge density of the macroion and smaller size of blackberry structures. Several instruments and methods are used to characterize macroions, their self-assembly, and also intermolecular interactions including laser light scattering (LLS), transmission electron microscopy (TEM), isothermal titration calorimetry (ITC).

Triggering receptor expressed on myeloid cells 2 (TREM2), a protein expressed on the surface of microglia, is genetically linked to, and a therapeutic target for Alzheimer’s disease (AD). As a myeloid cell receptor, TREM2 binds a variety of ligands, including AD-related proteins apolipoprotein E (ApoE) and β-amyloid. Upon stimulation, TREM2 activates various cell signaling pathways that drive microglial functions capable of ameliorating or accelerating AD progression and pathology (Ennerfelt et al., 2022; Gratuze et al., 2018; Leyns et al., 2017; Price et al., 2020; Takahashi et al., 2007; Takahashi et al., 2005; Wang et al., 2015; Wang et al., 2016; Wang et al., 2020; Zhao et al., 2018). Characterization of TREM2 signaling pathways mediating these functions, however, is incomplete. Further investigation of these signaling cascades is required to understand the function of TREM2 in AD beyond its genetic component. The goal of this research was to generate novel agonist monoclonal antibodies to activate cells in vitro in a TREM2-dependent manner, and to examine the phosphorylation state of potential downstream targets. We screened a library of rabbit host monoclonal antibodies that were raised against the ectodomain of human or mouse TREM2 by western blot to identify clones that were target specific. We then identified several clones that could activate cell signaling pathways downstream of TREM2 in vitro. These pathways include the activation of spleen tyrosine kinase (Syk), which is suggested to be downstream of TREM2/DAP12 microglial activation (Ennerfelt et al., 2022; Gratuze et al., 2018; Jay et al., 2017; McQuade et al., 2020; Schlepckow et al., 2020; Wang et al., 2020; Zhao et al., 2018). Syk activation was characterized using phospho-specific anti-Syk monoclonal antibodies. Having established tools to activate TREM2, we screened other downstream proteins related to Syk signaling that may also be engaged by TREM2 activation. Based on our findings, we suggest that Syk phosphorylation is indeed a reliable readout for TREM2-dependent microglia activation. We further suggest that the antibodies validated herein can be leveraged to further characterize signaling events and cellular responses (phagocytosis, inflammation, proliferation, etc.) downstream of TREM2. Full characterization of TREM2 signaling cascades can be applied to AD therapeutic research, targeting the benefits of upregulating or downregulating TREM2-dependent microglial activation to attenuate AD pathology.

Monolayer-protected clusters (MPCs) are a class of metal-organic compounds that typically contain dozens of metal atoms yet retain their molecularity. The MPCs have two main structural components, the inner metallic core, and the outer ligand shell. Therefore, the modifications of these MPCs can be done by altering either the metal core or the outer protecting ligand shell through metal/ligand exchange reactions. Significant progress has been made toward understanding the transformational chemistry of gold MPCs through metal and ligand exchange reactions. But comparatively, only a little information is known on the transformational chemistry of silver MPCs so far. In this study, we used the all-silver M4Ag44(p-MBA)30 MPC as a model system to study post-synthetic ligand exchange reactions, where M is a mono-cationic counterion and p-MBA is para-mercaptobenzoic acid. Different para-substituted aryl thiols were used as heteroligands, varying both electronically and sterically. The fundamental investigations were focused on revealing the nature of these reactions, reaction extent, exchange sites and kinetics to gain mechanistic insights into the ligand exchange reactions. The product distributions of the ligand exchange process were monitored by electrospray ionization mass spectrometry (ESI-MS) and UV-vis spectroscopy. Using these techniques, we identified a few trends in ligand exchange on silver MPCs concerning the electronic and steric nature of the heteroligand. Our investigations revealed that the ligand exchange on silver MPCs is electrophilic in nature and the electronic structure of the ligand plays a strong role in the exchange compared to the steric effects. Also, product distributions of ligand exchange on silver MPCs were found to be random with no evidence of site specificity. The stabilities of M4Ag44(p-MBA)30-x (SR)x (SR are thiol ligands such as 4-bromothiophenol (4-BTP), 4-fluorothiophenol (4-FTP), benzenethiol (BT), 4-methylbenzethiol (4-MBT), 4-mercaptophenol (4-MP) and 4-aminothiophenol (4-ATP)) clusters having the same structure but different ligand populations were systematically studied. It was clearly revealed that subtle compositional changes in the ligand shell could significantly alter the overall stability of M4Ag44(p-MBA)30 MPC although they all had an electronic structure of 18-electron superatom shell closure. Ligands like 4-BTP and 4-FTP were found to be better surface ligands than 4-MP or 4-ATP to stabilize M4Ag44(p-MBA)30 MPC. Furthermore, a detailed analysis of different input ratios revealed that the 1:6 ratio emerged as the optimal configuration, leading to enhanced stability for M4Ag44(p-MBA)30 across all ligands.ESI-MS analyses were conducted to investigate the product distributions resulting from ligand exchange reactions of M4Ag44(p-MBA)30 with heteroligands, namely 4-BPT, 4-FTP, and BT. The equilibrium product distributions observed in the study exhibited a remarkable adherence to the binomial distribution model, with all 30 ligand sites assumed to be identical and independent.Through this study, it became evident that various ligands exhibited distinct affinities to the MPC, and this trend was determined by the electronic effects of the ligands. These findings shed light on the intricate interactions between the M4Ag44(p-MBA)30 cluster and the different ligands, revealing how electronic properties play a crucial role in influencing ligand-MPC exchange dynamics.These findings are expected to be fundamental components of an MPC reaction library, which would include various formation and transformation reactions and provide a deeper understanding of how they can be carried out.

Surface modification of water filtration membrane materials has the potential to imbue attractive qualities, such as enhanced antifouling or solute rejection/selectivity capabilities. Development of next-generation membrane materials will therefore rely on design rules relating surface structure and functional properties. Heuristics exist for simple surfaces comprising homogeneous chemistries and have largely been discovered through trial-and-error synthesis and characterization. However, we lack a complete understanding of nanoscopic mechanisms governing the water-mediated interactions between contaminants/foulants and realistic surfaces with chemical and topological heterogeneity. Furthermore, trial-and-error methods are not able to efficiently explore the large design space offered by multifunctional surfaces. This dissertation develops relationships between surface chemistry and local water/solute behavior for model membrane materials, using computational inverse design approaches. By coupling molecular dynamics simulations with optimization algorithms, we identify non-intuitive chemistries showing enhanced functional properties. Genetic algorithm optimization of patterns of nonpolar and polar chemistries in a model nanopore suggests that arrangement of polar chemistry in rings along the nanopore wall will enhance selectivity of water over small, neutral solutes. Active-learning-based optimization of more complex patterns with both chemical and topological heterogeneity suggest that rings of large nonpolar groups create a rough surface that achieves similar effects. Importantly, these non-intuitive functionalities discovered by the inverse design approach suggest previously unexplored mechanisms governing water-mediated solute transport in model membrane materials.Sequence-specific polymers such as polypeptoids provide a synthetically accessible route to chemically precise surface modification. However, exploration of sequence-structure-function relationships for polypeptoids has been lacking, in part because computational workflows to simulate polypeptoids are not well established. In collaboration with detailed experimental characterization, we validate an enhanced sampling simulation workflow and atomistic model for polypeptoids. We then show that polypeptoid sequence modulates local water behavior in dilute solution and at peptoid brush surfaces, and that the changes in water structure can be related to trends in affinity of small-molecule solutes for peptoid brush surfaces. Finally, we apply the previously developed inverse design techniques to build sequence-structure relationships by identifying sequences with extremal conformational behaviors.

This work presents the efforts pursued to improve InGaAs/InP FET technologies for high frequency applications. Self-Aligned MOS-HEMTs were developed using a sacrificial InP layer and a diluted HCl sacrificial etch. The new process removes the previous issue of misalignment in MOS-HEMT technology. In addition, the self-aligned process results in a new “V-gate” as opposed to the tradition “T-gate”. This new gate technology no longer requires the bi-layer resist used in traditional HEMT technology and allowed for gate footprint scaling from 50 nm to 20 nm. To improve processability and high frequency performance, a theory on the effects of topside link thickness on resistance, capacitance, and cut off frequency was proposed. Traditionally, HEMTs have thick link regions to keep the donor ions far from the mobile charge in the channel. This keeps scattering and resistance in the source low; however, this places more material in between the source and the gate and increases capacitance. Simply, the theory states that as transistors continue to scale, the mobility of the link becomes less dominant than the extrinsic source gate capacitance when considering optimal link thickness. In the new process, CGS + CGD was reduced by a total of 40% compared to previous MOS-HEMTs. With these improvements, a Lg = 20 nm device, exhibiting fτ = 525 GHz, fmax = 709 GHz, and a Lg = 36 nm device, exhibiting fτ = 479 GHz, fmax > 1 THz were demonstrated.

Superparamagnetic nanoparticles represent an exciting area of research within the broader field of nanoscale materials. Synthetic control over physical properties, such as nanoparticle size, shape, and crystalline phase strongly impact the magnetic properties, ultimately dictating the functionality in potential applications.Chapter 1 provides a brief background of nanoscale magnetic materials. It discusses the high degree of control possible through colloidal nanoparticle synthesis techniques, as well as common challenges encountered. The chapter includes specific examples on the structure-property relationship, including implications for magnetism, concluding with a summary of superparamagnetism.Chapter 2 discusses the efforts to enhance the reproducibility in magnetic nanoparticle synthesis. The chapter introduces two novel forms of iron oleate precursor that offer long-term stability, well-defined stoichiometry, and large-scale availability, addressing issues with reproducibility. These advancements enable the synthesis of magnetite nanoparticles with tunable sizes ranging from 4 to 16 nm and low size dispersity, providing consistent results in the superparamagnetic size regime.Chapter 3 details the development of a new technique for the quantification and parametrization of superparamagnetic nanoparticle magnetization curves. The size-dependent magnetic properties were elucidated by fitting the data to a statistical model, leading to a better understanding of these materials' behavior and potential for applications. It emphasizes the challenges in interpreting magnetization data and the importance of simplified models in advancing the field.Chapter 4, in collaboration with Angelica Orlova, presents the extension of the statistical analysis of magnetization data to a molecular system. Three ErCOT2 compounds with varying structures, including the angle, and spacing between magnetic units, were analyzed. The temperature dependence and effect of dipolar coupling between ErCOT2 units on the magnetization curve were analyzed. Each curve was deconvoluted into its components, which were tracked and quantified across the parameter space.

Since their invention in 1958, Integrated Circuits (ICs) have become increasingly more complex, sophisticated, and useful. As a result, they have worked their way into every aspect of our lives, for example: personal electronic devices, wearable electronics, biomedical sensors, autonomous driving cars, military and defense applications, and artificial intelligence, to name some areas of applications. These examples represent both collectively, and sometimes individually, multi-trillion-dollar markets. However, further development of ICs has been predicted to encounter a performance bottleneck as the mainstream silicon industry, approaches its physical limits. The state-of-the-art of today’s ICs technology will be soon below 3nm. At such a scale, the short channel effect and power consumption become the dominant factors impeding further development. To tackle the challenge, projected by the ITRS (International Technology Roadmap for Semiconductors) a thinner channel layer seems to be the most viable solution. This dissertation will discuss the feasibility of using 2D (two-dimensional) materials as the channel layer. The success of this work will lead to revolutionary breakthroughs by pushing silicon technology to the extreme physical limit. Starting from graphene in 2004, 2D materials have received a lot of attention associated with their distinct optical, electrical, magnetic, thermal, and mechanical properties. In the year 2010, IBM demonstrated a graphene-based field effect transistor with a cut-off frequency above 100 GHz. The major challenge of applying graphene in large-scale digital circuits is its lack of energy bandgap. Other than carbon, a variety of graphene-like 2D materials have been found in various material systems, like silicene, germanene, phosphorene, MoS2, WS2, MoSe2, HfS2, HfSe2, GaS, and InS, etc. Among all the 2D materials, silicene appears to be the most favored option due to its excellent compatibility with standard silicon technology. Similar to its counterpart graphene, silicene does not exhibit an opened energy band gap, which prevents its immediate applications in the mainstream semiconductor industry. In-plane tensile strain leads to the formation of a bandgap in bilayer silicene with low buckling. This dissertation conducts a study on energy bandgap opening in silicene and ultra-thin silicon films by engineering the strain and stress. Density functional theory has been employed to optimize the atomic structures and to calculate the energy band diagrams. Bandgap opening up to 0.17 eV has been found in the AA-stacked bilayer silicon film under in-plane strain 10.7%~15.4%. A number of common semiconductor substrates have been investigated to examine the possibility of growing bilayer silicon with excessive in-plane strain i.e., CdSe, InAs, GaSb, and AlSb. In addition, by taking into the account of magnetic spin polarization, energy bandgap 0.25 eV in AB-stacked bilayer silicon films have been observed. Without applying strain, the spin up and down state are degenerated. By applying the strain 7.56 %, the spin degeneration has been removed both in the conduction band and valence band. This opens the opportunity to build spin-based field effect transistor.

A better understanding of dissipation is crucial for understanding real-world quantum systems. Indeed, all quantum systems experience interactions with an (often) uncontrollable outside environment that can lead to a decay of excited state populations and a loss of quantum coherences. The study of dissipation is timely as the development of next-generation nanoscale quantum technologies is on its way, and the existence of non-trivial quantum effects in biological systems is being seriously investigated. However, descriptions of dissipation in quantum systems are reduced (most of the time) to time-local approaches and (everywhere) to space-local independent environments. These simplifying assumptions do render analytic and numerical calculations possible, yet they get rid of a breadth of physical processes that can alter radically the quantum systems' dynamics. In this thesis, building on a numerically exact tensor networks method, we developed a technique able to handle spatio-temporal correlations between a quantum system and bosonic (i.e. vibrational, electromagnetic, magnons, etc.) environments. With this method we studied the signalling process - a form of information backflow - in quantum systems, and uncovered how it can induce non-trivial dynamics, and be leveraged to populate otherwise inaccessible excited states. We also evidenced the ability of 'non-local' environment reorganisation, induced by system-environment interactions, to radically change the nature of the thermodynamically favoured system ground state. The new phenomenology of physical processes, resulting from considering quantum systems interacting with a common environment, has important consequences for the design of nanodevices as it gives access to new control, sensing and cross-talk mechanisms. In another vein, these results might also give us a new framework to study and interpret (quantum?) effects in the biological realm.

High-precision neuromodulation with high efficacy poses great importance in neuroscience. Also, ultrasound frequency in sub-MHz gives greater penetration depth of neuromodulation in vivo, and has many different biomedical applications, such as ocular drug delivery, arte- rial hyperplasia reduction, etc. Here we fabricated a series of carbon-nanotube (CNT) and polydimethylsiloxane (PDMS) mixture films with different CNT concentration and thick- ness, which can generate highly efficient sub-MHz ultrasound. We discovered that 0.8% CNT concentration CNT/PDMS films gave approximately 1 MHz frequency, below which we achieved tunable frequency in sub-MHz area. Additionally, we adjusted the PDMS base to curing agent ratio and discovered that the 2:1 ratio’s optoacoustic conversion ef- ficiency is 1.6 times greater than the typical 10:1 ratio. Our work offers a potential way to increase photoacoustic conversion rate by optimizing CNT/PDMS films’ fabrication for further photoacoustic-related applications.

The unique size-dependent optical and physical properties of inorganic nanocrystals such as those made of metals and semiconductors have generated an enormous interest in exploiting them to develop a variety of applications. Due to their unique features, they have also been integrated into a variety of applications, including biological sensing, imaging, optoelectronic devices, and as fluorescent probes in biology. Growth of these materials using either hydrophilic or hydrophobic conditions yields nanocolloids that are not readily compatible with biological systems, due to either the hydrophobic nature of the ligands or the labile properties of the coatings. The main focus of this dissertation is to design and synthesis a series of molecular scale and multidentate N-heterocyclic carbene (NHC)-based ligands and apply them for the surface functionalization various inorganic nanocrystals and render them water soluble. We also summarize coordination interactions of NHC moieties with the gold surfaces to get better understanding about nature of NHC-Au bond. In Chapter 1, we summarize some of the basic optical and physical properties of inorganic nanomaterials including, quantum dots (QDs), gold nanoparticles (AuNPs), and gold nanoclusters (AuNCs). We briefly describe the history of growth strategies for preparing high quality QDs, AuNPs, and AuNCs. We then provide an overview of the surface functionalization methods to assemble colloidally stable and biocompatible nanoparticles followed by introducing the N-heterocyclic carbene (NHC)-based ligands as a novel metal anchoring group and their application in modern surface chemistry. In Chapter 2, we will focus on the synthesis of hydrophobic oleylamine-coated gold nanoparticles (OLA-AuNPs) and the surface coordination with N-Heterocyclic Carbenes (NHCs) relying on ligand substitution strategy. We detail the synthesis and characterization of three distinct water-compatible NHC-based ligands: an amine-modified small molecule, a monomeric NHC appended with a short poly(ethylene glycol) (PEG) block, and a modified poly(isobutylene-alt-maleic anhydride), PIMA, that simultaneously presents multiple NHC groups and several short PEG chains. We find that rapid competitive ligation onto the AuNPs (often requiring several minutes of mixing) takes place regardless of the exact structure of the ligand. Furthermore, the long-term colloidal stability of the NHC-stabilized AuNPs have been tested after phase transfer to water, a highly challenging chemical venue for such groups due to their moisture sensitive nature. Our experimental data show that the multidentate NHC polymer coating exhibits the highest affinity to AuNPs, which manifests in long-term colloidal stability in buffer media, absence of any aggregation or degradation build up for at least one year of storage. In addition, the NHC-polymer-coated AuNPs exhibit long term resistance to competition from reducing small molecules such as dithiothreitol, DTT. In Chapter 3, we introduce a top-down etching strategy using poly (ethylene glycol)-appended-NHC (PEG-NHC) ligands to promote surface digestion of gold nanoparticles (AuNPs). We find that under long term incubation conditions using excess molar ratios of PEG-NHC ligands, with respect to AuNPs, progressive etching of Au surfaces takes place. This progressively alters the plasmon absorption features, yielding the formation of NHC-Au complexes. This top-down etching method has provided us insights about the nature and strength of coordination interactions of NHC groups with Au surfaces; these interactions are inherent controlled by the σ-donating nature (soft Lewis base) of NHC which match the soft acidic nature of Au surfaces, resulting in very strong coordination interactions and binding. We use UV-vis absorption measurements to monitor the transformation process, where loss of plasmonic features of AuNPs with time takes place. We further characterize the digestion kinetics by extracting a characteristic time which is found to depend among others on the ligand to AuNP molar excess. We then combine these data with 2-D 1H, 13C NMR spectroscopy, matrix assisted laser desorption/ionization (MALDI), and transmission electron microscopy measurements to identify the structure and chemical nature of the resulting NHC-PEG-Au complexes. In Chapter 4, we describe the formation of fluorescent blue emitting ultrasmall gold nanoclusters (Au NCs), following the digestion process described in Chapter 3 above, achieved under thermal treatment. This route offers an elegant way to produce stable and homogeneously dispersed AuNCs. Specifically, we show that heating of Au-NHC complexes triggers the formation of ultra-small gold nanoclusters that are fluorescent in the blue region of the optical spectrum upon UV excitation. Here, the starting non-fluorescent NHC-Au(I) complexes undergo aurophilic interactions (as is the tendency for gold(I) compounds) and form blue fluorescent small size nanoclusters. We carry out a thorough characterization of the nanoclusters using analytical techniques such as UV-vis absorption, fluorescence spectroscopy and high-resolution transmission electron microscopy. Among others, we find that these nanoclusters show the excitation maximum at 380 nm and the emission maximum at 460 nm. Transmission electron microscopic analysis shows that most of these particles are

Diagnostic platforms are becoming increasingly sophisticated in their ability to monitor a variety of biomarkers across different biofluids. Current laboratory gold standard techniques including liquid chromatography/mass spectrometry (LC/MS), enzyme-linked immunosorbent assays (ELISA), and polymerase chain reaction (PCR) typically require costly instrumentation, complex protocols, and long time-to-results. Point-of-care (POC) devices seek to simplify sample processing and analysis using more compact and automated devices. Point-of-care approaches have already revolutionized the healthcare landscape by enabling more rapid and decentralized diagnosis while reducing costs and the requirement for trained personnel. Nonetheless, there is a significant push to take diagnostic devices beyond POC directly to the level of the individual. Wearable, or point-of-person (POP) devices, have made their way into the mainstream with products like the Apple Watch, Fitbit, and Oura Ring.While wearable devices have been met with commercial success and interest from the healthcare community and the public, they are mostly limited to monitoring physiological markers such as heart rate, temperature, and sleep activity. There is great interest in advancing wearable devices to monitor a variety biochemical species including metabolites, proteins, nucleic acids, neurotransmitters, and hormones. The ability to detect biochemical biomarkers in readily sampled biofluids like saliva, sweat, tears, and interstitial fluid has the potential to enable continuous and minimally invasive monitoring. Wearable devices can also facilitate personalized medicine, whereby there is an ever-increasing shift to provide feedback and therapies tailored to individuals based on their specific biometrics, as opposed to the long-standing one-size-fits-all approach to modern medicine. My dissertation details four projects I focused on during my doctoral research that seek to address four different primary challenges in the field of wearable monitoring. Specifically, I investigated strategies to reduce fabrication costs and improve lab-to-market commercialization, novel energy harvesting approaches to realize self-powered sensors, materials design strategies to improve the sensor-biology interface, and finally, new sensor architectures to enable highly sensitive and selective quantification of low-abundance analytes. The resulting technologies span the gamut from monitoring biophysical to biochemical signals including metabolites and hormones. Ultimately, I aim to demonstrate the breadth of physiological information that can be acquired using wearable devices.

Understanding the structure and diffusion properties in photovoltaic and battery materials is imperative to understanding the device stability and performance. In this work we investigate structure-diffusion relationships in two complementary energy technologies – lead halide perovskites (LHPs) solar cells and lithium–sulfur batteries (LSBs) – using ab initio calculations and machine learning inter atomic potentials (MLIAPs). LHP solar cells have seen a meteoric rise in their power conversion efficiency (>25%) in the last decade. However, halide ion migration induced instability and hysteresis is a major impediment to its commercialization. In the first project, we demonstrate the use of constrained nudged elastic band (NEB) calculations to quantitatively establish the correlated effects of A site cation motion, H bonding and octahedral rotation on halide ion migration in APbBr3 (A = Cs or methylammonium/MA) LHPs. LSBs are among the most promising energy storage solutions due to their high theoretical capacity (1672 mAh g-1) and the low cost of S but suffers from polysulfide shuttling induced capacity fading. Replacing traditional liquid electrolytes with solid-state electrolytes (SEs) is a potential solution to this problem. In the second project, we investigated the (electro)chemical stability of cathode/SE interfaces in LSB using a combination of DFT and ML-IAPs based on the moment tensor potential (MTP) formalism. Thermodynamic analysis predicts that among the major SE chemistries (oxides, sulfides, nitrides, and halides), sulfides are generally predicted to be the most stable against the S8 cathode. Molecular dynamics (MD) simulations on realistic large-scale (thousands of atoms) α-S8|β-Li3PS4 interfaces using the developed MTP reveal the formation of LixSy and Sx species at the interface. The reaction products were in general found to increase the activation energy (Ea) of Li-ion diffusion at the interface, but the type of β-Li3PS4 surface interfaced was found to predominant determine the interfacial Li-migration activation barriers.The other critical issues of LSBs are the low electronic conductivity of S which limits practical capacity and the high interfacial impedance induced by large volume change (>80%) during cycling. In the third part we report an electrically conducting low melting point (65°C) S9.3I cathode which is demonstrated to retain 87% capacity after 400 cycles with periodic reheating that facilitates interfacial contact healing. We use DFT calculations to elucidate the hitherto-unknown structure of this cathode and understand the origin of its high electrical conductivity.

The gustatory system in insects plays a significant role not only for sensing edible food sources but also as a first line of defense to prevent ingestion of harmful, toxic substances. Both internal factors like the previous dietary experience or external factors like presence of different cues in the diet or the specialization on a particular host affects the dietary preferences and in this study we examined some of those aspects. First, we studied how niche segregation affects the feeding preferences in different Drosophila species. We observed that Drosophila sechellia, due to their adaptation in a particular host plant showed gustatory preference to three noni fatty acids octanoic, hexanoic and decanoic are aversive for the generalist sister species to D sechellia. We also found that obp18a, Gr33a and Ir47a are necessary for the differential gustatory preferences between the generalists and specialists.The fatty acids can act as nutritive source but we observed a concentration dependent taste modality is present. At higher concentrations, the hexanoic acid is strongly aversive for the flies and it depends of bitter Gr33a mediated pathway. Our study also investigating is that of mechanisms underlying compensatory changes in food preference upon macro-nutrient deprivation of either carbohydrates or proteins. Using electrophysiological and behavioral analyses, we found that macronutrient deprivation alters both taste preference and peripheral taste sensitivity in flies. We discovered that neuropeptides like dopamine and Drosophila insulin like peptide underlie these compensatory changes. Our study also examined an alternative pathway for high concentrations of salt rejection. Salt is unique, since its behavioral valence varies with concentration – low salt is favored and high salt is rejected. Accordingly, salt broadly activates both appetitive and aversive classes of taste neurons, whose combined activities control behavioral response. Given that pure salt is known to activate sweet taste neurons, we wished to evaluate the effects of neuronal response to sucrose + salt mixture. We tested mixtures of sucrose with varying concentrations of salt and found that high salt inhibited sucrose response. Sugar neuron inhibition was independent of Ir76b function, as well as Gr66a function, as high salt detection is dependent on both.

The nonlinear magnetization dynamics in zero-dimensional magnets have received increasing attention in recent years due to their potential applications in high-density data storage and spintronic devices. It also shows parallels to AMO physics, nonlinear optics, quantum information systems, and even some astrophysical phenomena. Magnon scattering processes, which constitute a major dissipation channel in nanomagnets, play a major role in determining the energy efficiency of spintronic applications.In this work, first I report an experimental observation of different kinds of magnon- magnon interactions affecting the magnetic damping within the nanomagnet. I focus on predominant nonlinear magnon scattering processes in nanomagnets, including degenerate and non-degenerate three magnon scattering and degenerate four magnon scattering. To do the experiment, I implement magnetic tunnel junction (MTJ) nanodevices, consisting of a free layer and a synthetic antiferromagnet at their core. It is shown these nonlinear processes can redefine and invert the nanomagnet’s response to spin torques. A theory is established to explain this counter-intuitive effect, demonstrating the damping parameter of a spin wave stops being frequency-independent and becomes a resonant function of the excitation frequency.Controlling magnon processes and thus magnetic damping is the key to improving the performance of future computer systems. In this regard, I propose an approach for controlling magnon scattering by a nanoscale dipole switch. I demonstrate an experimental proof-of-concept in MTJ nanodevices. By triggering the spin-flop transition in the synthetic antiferromagnet and utilizing its dipole field, a three-magnon process in the free-layer is toggled. The switching of the synthetic antiferromagnet allows for controllably tuning the strength of the magnon interaction by at least one order of magnitude, leading to two distinct dissipative states.Additionally, I study the magnetic switching of a nanoscale synthetic antiferromagnet (SAF) with a perpendicular order parameter incorporated in a MTJ structure. I drive the MTJ with microwave pulses and observe spin-flip switching of the SAF by resonant ex- citation of an individual magnon mode of the SAF. The magnon spectrum of the nanoscale SAF is discrete. Evaluation of the switching probability distributions shows that various modes from this spectrum can facilitate the switching. Moreover, it suggests a substantial contribution of the thermal spin-torque.Finally, I investigate the electric noise in MTJs whose understanding is a prerequisite for employing them in next-generation applications. I observe random telegraph noise, which is frequently found in MTJs but not yet fully understood. By varying the temperature in the range of 80–300 K for an MTJ in the parallel state, we encounter anomalous device resistance (steps) attributed to magneto-structural phase transitions of iron oxide clusters at the CoFeB/MgO interface. At temperatures of these anomalies, telegraph noise shows a significant increase. This correlation suggests that the oxide clusters have a significant impact on MTJ noise characteristics.

Semiconductor nanoplatelets (NPLs) are nanocrystals with quantum confinement only in the thickness dimension and precise monolayer thicknesses. They have excellent monodispersity giving them narrow linewidths, high absorption cross-sections, and high photoluminescence quantum yields. In addition to their exceptional photophysical properties, they can have lateral extents that exceed 1000 nm, making them analogous to two-dimensional semiconductors such as transition metal dichalcogenides with the advantage of colloidal preparation. In this dissertation I explore how interesting photophysical properties can arise within these materials as a result of their anisotropic structure. Chapter 1 provides the foundation for understanding the electronic and physical structures of NPLs, briefly summarizes the current understandings in the field, and presents open questions that this dissertation aims to address.In Chapter 2, we develop a new type of heterostructure through cation exchange from CdTe to HgTe NPLs. HgTe NPLs are promising candidates for optoelectronic applications in the short-wave infrared (SWIR), but their absorption and photoluminescence has limited tunability. By taking advantage of their large, exposed surfaces following cation exchange, we grow HgTe quantum dots (QDs) on the lateral faces and establish a heterostructure capable of energy transfer from 2D NPL to 0D QD. We extend the tunability of photoluminescence through the energy transfer by controlling the confinement within the quantum dot, and observe high quantum yields across the SWIR.Chapter 3 builds on our understanding of the HgTe NPL/QD heterostructure by exploring the mechanism and efficiency of energy transfer in greater depth. We compare the in-situ grown QD on NPL system to a system of mixed QDs and NPLs and demonstrate that the near unity energy transfer is only achieved using the in-situ method. We quantify this efficiency and find that the mixed case follows a F�rster Resonance Energy Transfer while the in-situ case is likely a near field energy transfer. Using our estimates, we also model the exciton diffusion within HgTe NPLs and find that the magnitude of the diffusion constant is comparable to other extended 2D semiconductors.In Chapter 4 we turn our focus to synthetic procedures for CdTe NPLs to control lateral area. We develop a seeded growth mechanism that can be used to reproducibly extend NPLs from their small size after initial synthesis (100-500 nm) to mesoscale length scales (1-2 μm). We show that these methods can be applied to CdTe and CdSe, and cation exchange from these extended NPLs produces mesoscale HgTe and HgSe NPLs. Using in-situ monitoring, we examine how the seeded growth proceeds and show that the extension follows the understood mechanism of lateral ripening. Finally, we image the photoluminescence of the mesoscale NPLs using correlative microscopy and demonstrate that their large extents allow for spatial resolution of their photophysical properties.Chapter 5 develops another synthetic procedure for controlling lateral extent, but without the need for seeded growth. By closely examining the parameters used during a slow injection procedure, we are able to understand how the precursor, temperature, and ligands play a role in NPL area and directly synthesize mesoscale NPLs in one step. We systematically show how each parameter affects the lateral size and monolayer thickness of the final NPL product. Using the largest mesoscale NPLs, we use transmission electron and atomic force microscopy to examine their propensity for stacking, as well as Raman spectroscopy to observe strain with spatial resolution.Chapter 6 describes a handful of remaining experiments and projects that were not fully developed for publication. This also includes some techniques and lessons learned in sample handling which may be useful for future students.Finally, Chapter 7 describes our efforts in chemical education research within the general chemistry laboratory course for life science majors at UCLA. In this chapter we examine how the style of pre-lab affects student performance when tasked with learning a new technique. A cohort of students critically evaluate a series of videos demonstrating exemplary technique and poor technique before attending their lab sections, and these students are compared to a cohort who simply watched the exemplary technique before starting the experiment. Our goal is to reduce cognitive load during the experiment by establishing the proper steps before attempting to practice the technique. We show that although the majority of the class is unaffected by the intervention, we are able to reduce the percentage of students performing as outliers. We also demonstrate that the intervention reduces the dependence of students on instructor feedback during the lab sessions which is advantageous for large classrooms.

Thin film LiPON and LLTO are promising solid electrolyte candidates in the development of next generation batteries. These materials can be deposited via RF magnetron sputtering, which is a technique suitable for thin film mass production. In this work, the deposition conditions for LiPON and LLTO are optimized to improve film quality. The thickness of LiPON films is shown to be tunable with the approximation of deposition rate. LiPON films as thin as 325 nm are produced to exhibit sufficient ionic conductivity and low electronic conductivity. Strong electrochemical performance means LiPON can remain a cohesive film even at very thin scales. With this, LiPON has potential to improve volumetric energy density when implemented into thin film batteries. Bulk LLTO is characterized to relate ionic conductivity to Li amount, and the composition with highest ionic conductivity influences the choice of LLTO sputtering target. LLTO film deposition rate is studied as a function of both RF power and deposition pressure, and RF power is shown to have a much stronger effect on deposition rate. Film delamination issues are addressed by decreasing LLTO film thickness, and adhesion to the Si substrate is maintained during the post annealing process. EDS analysis yields the La/Ti ratios of LLTO films, illustrating changes in LLTO composition due to deposition pressure.

Gold nanoparticles (AuNPs) have gained popularity in the development of in vitro diagnostics for their distinct physical and optical properties. More specifically, the surface plasmon resonance (LSPR) can be exploited via aggregation to generate a significant absorption band shift in the visible region of the electromagnetic spectrum, resulting in a pronounced red-to-blue color change that is visible to the naked eye. Our group has developed an intuitive and accessible, label-free diagnostic platform that takes advantage of the key proteolysis step in viral replication by designing cleavable peptide intermediates to interface with gold nano colloids. Peptides are an effective probe due to their diverse and tunable functional groups found on amino acid side chains, which can interact with AuNPs through electrostatic, dithiol bridging, or amphiphilic interactions to promote aggregation. First, we determine the effects of modifying AuNPs with various surface ligands on aggregation propensity in the presence of charged, thiolate, or aromatic amino acids. The characterization study will then inform a final peptide design that encompasses all three molecular interactions which will be used to colorimetrically detect the coronavirus main protease. Second, we build on a well-established zwitterionic peptide design for electrostatically interfacing negatively charged AuNPs by providing additional optimizations of peptide design through the addition of lysine to arginine groups. An optimized peptide probe is then used to colorimetrically detect the norovirus main protease, additionally demonstrating the generalizability of this diagnostic platform.

X-ray is widely used in medical areas, typically for cancer treatment. Studies seek to enhance the X-ray effect using nanomaterials to increase energy deposition efficiency and a new discipline called X-ray nanochemistry was established based on these studies. While nanoparticles with high Z materials are proven to be able to deposit more X-ray energy to a system, nanoparticles are also found to be involved in the chemical reactions triggered by X-ray or biological response under radiation. These findings lead to discussions about other types of dose enhancement factors like chemical enhancement and biological enhancement are discussed. More studies were still needed to study the mechanisms and deconvolute these dose enhancement factors. The dissertation presents continuous work in the field of X-ray nanochemistry, focusing on type 2 physical enhancement and chemical enhancement. Direct quantification of type 2 physical enhancement (T2PE) was done by conjugating a 12-mer single-strand DNA onto surfaces of silica-coated gold nanoparticles (Au@SiO2). T2PE comes from energy deposited by secondary electrons emitted from nanoparticles in radiation which are low-energy electrons and will disappear a few nanometers from the surface of the nanoparticles. 3 reporters were linked to DNA strands respectively and the magnitude of T2PE was determined by comparing the number of reporters released from Au@SiO2 versus the same size of SiO2 when DNA strand breaks occurred. More than 9 times more reporters were released in the presence of 1wt% Au@SiO2. T2PE showed a much higher dose enhancement factor than T1PE and can help to develop X-ray-triggered releasing nanosystems by using single-strand DNA as linkers on the nanoparticle surface. An EPR study was performed using spin trap BMPO(5-tert-Butoxycarbonyl-5-methyl-1-pyrroline-N-oxide) to detect •OH produced by X-ray radiation in the presence of 3-nm THPC (Tetrakis(hydroxymethyl)phosphonium chloride) AuNPs. Similar amounts of •BMPO-OH, the intermediate, were detected compared to the solution irradiated without the presence of AuNPs. More •BMPO-H adduct was detected when AuNPs were in the solution during radiation. Such a result indicated that for low concentration of small AuNPs didn’t increase the production of •OH but catalyzed the conversion of a hydroxylation intermediate to another product. A triple jumps mechanism was then proposed based on this finding. The possible existence of catalyzed breakage of single-strand DNA on small AuNPs surfaces was explored. DNA strands with fluorophores and quenchers at each end were loaded on Au surfaces then irradiated. The FRET (Förster resonance energy transfer) effect on the DNA strand was interrupted when the strand is broken. Amounts of SSBs (single-strand breaks) were determined using increased fluorescence intensity after X-ray irradiation. Mass spectrometry was used to quantify DNA damage after irradiation using an internal standard in the samples. Nearly 9 times more SSBs with correction when DNA strands were on 5-nm citrate AuNPs. A higher SSBs to total DNA damage ratio was also found, indicating possible catalytic base damage conversion to strand breaks on Au surfaces. A nanoreactor for X-ray application was synthesized and tested. A •OH probe, 3CCA (coumarin-3-carboxylic acid) was encapsulated in hollow mesoporous silica shells. The shells were sealed with another layer of solid silica to prevent probes from escaping. A dose-dependent response was measured with fluorometry. A linear dose response was observed when the nanoreactors were in dry form or suspended in solutions with scavengers or with small AuNPs. Results showed that the synthesized structure can be used as a nanoreactor for X-ray application. The silica layer was not interacting with probes trapped inside and successfully isolated internal molecules.

The utilization of plasmonic nanomaterials has inspired scientists for decades due to their unique optical phenomenon, known as localized surface plasmon resonance (LSPR). This phenomenon is one of the driving forces behind the creation of new nanostructures due to their material, size-, and shape-dependent properties. Significant research, in the field of nanoplasmonics, has been done to create nanomaterials used for various applications in catalysis, surface enhanced Raman scattering (SERS), and LSPR-based sensors. Gold nanorod (AuNRs) are of exceptional interest due to their shape dependent properties which allow the longitudinal mode of the LSPR to be tuned from the visible to the near infrared region. Chapter 1 reviews the common synthetic methods for gold nanorods and the importance of surface modification.Chapter 2 provides an in-depth analysis of the theoretical simulations of the LSPR for gold nanostructures for both analytical and numerical methods. Insights on the shape, size, and refractive index dependence for the LSPR is addressed. Furthermore, in the subsequent chapters, the extinction efficiencies are calculated for all the synthesized nanomaterials presented in this dissertation using discrete dipole approximation (DDA) method, introduced in this chapter. The focus of Chapter 3 is on the controlled etching of silica coated gold nanorods into twelve different gold nanostructures. This chapter highlights how shape control is crucial to fine tune the optical properties of a nanostructure. Investigation into the mechanisms to synthesize each of these nanostructures was done via UV-Vis-NIR spectroscopy, NMR spectroscopy, and optical microscopy imaging. Chapter 4 introduces a unique nanomaterial called Agu, which has less than 2 nm layer of silver coating on spherical gold nanoparticles. For 100 nm gold nanoparticle with a silver coating between 0.5 and 2 nm, the shift in the surface plasmonic resonance (SPR) peak follows a sigmoidal function as a function of silver thickness on gold. This nanomaterial was used to detect X-ray irradiation etching of silver. The final chapter offers concluding remarks on the various nanostructures which have been synthesized throughout this dissertation. Description of the future work and applications are given.

Magnetic materials have played an enormous role in the advancement of technology over the past two centuries. Much of the current understanding of magnetism, however, is limited by the complexity of the interactions between particles from which collective behavior and interesting phenomena emerge. In the regime where the miniaturization of technologies combined with ultrafast responses are desired, these phenomena can become even more obscure. Probing these systems and interactions to gain insight into the origin of these phenomena is required for both fundamental understanding and for the engineering of novel materials and devices for application. In this dissertation, we study three magnetic systems exhibiting complex phenomena in confined geometries, mostly confining in one dimension as thin films. Elemental chromium is an antiferromagnetic metal with coupled spin density wave, charge density wave, and periodic lattice distortion. We track this ordering primarily through x-ray diffraction measurements statically, on ultrafast time scales following photoexcitation, and over longer time scales to follow the evolution and recovery to the static state. Certain antiperovskite manganese nitride compounds exhibit magnetovolume effects including negative thermal expansion tied to the transition in magnetic ordering between ferrimagnetic, antiferromagnetic, and paramagnetic phases. These magnetovolume effects are demonstrated for thin films through static x-ray diffraction measurements as well as dynamically following photoexcitation. And iron rhodium is an alloy with a room temperature transition between an antiferromagnetic phase and a ferromagnetic phase that also exhibits large magnetoresistance and magnetostructural effects. We conduct a study of its magnetic phase diagram through resistivity measurements and x-ray magnetic circular dichroism measurements at high field and with theoretical calculations. We also examine the effects of confinement in a film and in wires through polarized neutron reflectometry measurements. These experiments provide insight into the collective interactions in these materials and into the strong coupling of the charge, spin, and lattice degrees of freedom seen in each of them.

The ability to promote neural plasticity in the prefrontal cortex through the use of psychedelics and other psychoplastogens provides immense promise in the treatment of mental illnesses such as depression, post-traumatic stress disorder, and substance use disorder. With the advent of these new therapeutics, understanding the underlying mechanisms of action becomes critical to ensure they are used to their full potential and future psychoplastogen-based medicines can be rationally designed. We sought to determine some of the mechanisms through which psychoplastogens promote plasticity and produce therapeutic behavioral effects. Using molecular, cellular, and behavioral data we demonstrated the importance of 5-HT2A subcellular localization in relation to promoting neural plasticity, serotonin transporter-independent mechanisms of R-MDMA, and how the male sex hormone testosterone modulates the plasticity promoting properties of psychoplastogens. These findings further the understanding of psychoplastogen mechanisms of action, have implications in rational psychoplastogen drug design, how patient populations can be stratified for optimal therapeutic efficacy, and exploring how endogenously produced N-methyltryptamines may play a role in modulating consciousness.

Exploring the structural and electrical properties of DNA origami nanowires is an important endeavor for the advancement of DNA nanotechnology and DNA nanoelectronics. Highly conductive DNA origami nanowires are a desirable target for creating low-cost, self-assembled, nanoelectronic devices and circuits. In this work, the structure-dependent and moisture-dependent electrical conductance of DNA origami nanowires is systematically investigated. Silicon nitride (Si3N4) on silicon semiconductor chips with gold electrodes are used for collecting electrical conductance measurements of DNA origami nanowires, which are found to be more electrically conductive on Si3N4 substrates treated with a monolayer of hexamethyldisilazane (HMDS) (~1013 ohms) than on native Si3N4 substrates without HMDS (~1014 ohms). Atomic force microscopy (AFM) measurements of the height of DNA origami nanowires on mica and Si3N4 substrates reveal that DNA origami nanowires are ~1.6 nm taller on HMDS-treated substrates than on the untreated ones indicating that the DNA origami nanowires undergo increased structural deformation when deposited onto untreated substrates, causing a decrease in electrical conductivity. Another study indicates that the same DNA origami nanowires are more electrically conductive (~1012 ohms) in ambient/humid conditions. Finally, we demonstrate that DNA origami nanowires are more electrically conductive in aqueous conditions than under dry conditions in air. These studies highlight the importance of understanding and controlling the interface conditions and environmental factors that affect the electrical conductance of DNA origami nanowires, while also revealing the potential of DNA origami nanowires to be used as sensors and electronic devices.

While the exploitation of size effects on the mechanical performance of nanoarchitected materials is a well-established design paradigm, to date practical implementations have been limited to very selective topologies, material systems, processing techniques and size regimes. Widespread adoption of this approach will require substantial progress in topology optimization, multi-scale modeling and scalable nanomanufacturing. This thesis advances the field of optimal design of size-effect strengthened materials by developing three novel capabilities.Firstly, two-photon polymerization direct laser writing (TPP-DLW) and pyrolysis were used to fabricate plate-nanolattices for the first time. While architected materials are typically fabricated as polymeric structures via TPP-DLW, we found the viscoelastic properties of the polymer interfered with accurate comparisons against the upper bounds on stiffness and strength for an isotropic voided material. Thus, the polymeric structures were converted to pyrolytic carbon with strong linear elastic behavior for which the plate-lattice topology was confirmed to achieve the bounds in both stiffness and strength. Moreover, the combination of an optimal plate-lattice topology with size-effect strengthened pyrolytic carbon resulted in the highest specific strength architected material ever reported (at the time of publishing).Although the plate-nanolattices possessed exceptional mechanical properties, there is no suitable additive manufacturing process capable of fabricating larger material volumes for practical use. By contrast, syntactic foams, i.e., closed-cell foams composed of hollow particles that form spherical nonoverlapping voids, are amenable to self-assembly and may have comparable specific strengths and stiffnesses to state-of-the-art plate-nanolattices if fabricated with a ceramic constituent material and hollow microparticles. Unfortunately, there is no current scalable process to produce highly controlled hollow particles in the quantity, dispersity and sizes required to fabricate these foams. Therefore, a process to fabricate hollow template-free ceramic particles is introduced here to enable future self-assembled size-effect strengthened syntactic ceramic foams, wherein the hollow ceramic particles become the porogen allowing exceptional control over the final pore size distribution. In addition to demonstrating tunability of the particle size and wall thickness, the process also included special considerations for scalability and extensibility to other material systems.Lastly, a multi-scale computational procedure is developed to model the mechanical response and progressive failure mechanisms of size-effect strengthened ceramic syntactic foams, which may be produced in a scalable fashion using the particle porogens introduced previously. The computational approach includes a novel flaw field which may be generated for arbitrary porosity, and an accompanying material model which accounts for Weibull variability in the strength of brittle ceramics as well as increases in strength arising from reductions in the characteristic dimensions of geometric features. This model is developed in the framework of the material point method, constituting the first demonstration of a simulation incorporating large deformation, contact and fracture mechanics to investigate the strength and failure mechanisms of syntactic foams under uniaxial tension and compression. This thesis lays the groundwork for the design and scalable fabrication of size-effect strengthened materials for real-world applications requiring extreme strength and minimum weight. While the focus of this work is on ceramics, many of the results are general and applicable to nanoarchitected materials made of any constituent in which size-effects and topology influence strength.

Modern environmental and climate challenges call for accelerated electrification both at the industry level and at the consumer level. This clean energy transition heavily relies on innovations in electrochemical energy storage technologies. This work wants to shed more light on the incorporation of carbon nanodots into the likes of rechargeable ion batteries and supercapacitorsas one such contributing innovation. Rechargeable zinc batteries face challenges with anode reversibility, especially with lean electrolytes, impacting their cost-effectiveness for large-scale energy storage. In the first study, the involvement of zinc-coordinated carbon nanodots with histidine and carboxylates paved the way for an interphase that safeguards zinc anodes from dendrites and corrosion, while improving Zn2+ affinity and diffusion. In the second study, the use of sulfonyl-doped carbon nanodots as precursors for a laser-induced 3D carbon foam network manifested in a remarkably stable and conductive composite material for supercapacitor applications. The versatile and effective role carbon nanodots play in both works is on full display, as they show their potential for high-energy-density storage devices.

This dissertation will introduce a new synthetic method toward near-unity photoluminescence quantum yield CsPbBr3 nanocrystals. The synthesis of high quality CsPbBr3 was achieved through the exploitation of the delicate phase boundaries between the lead bromide phase stabilities. By stochiometrically exploring the complex and rich phase map associated with the lead bromide perovskites, deep suppression of non-radiative recombination of excitons generated upon photexcitation was achieved. In doing so, a critical ratio between bromide and lead in solution is established to reduce non-radiative recombination while maintaining phase purity. This dissertation provides additional evidence that halide vacancies are the primary contributor to non-radiative recombination in sub-stoichiometric synthesis of CsPbBr3 nanocrystals. Furthermore, it is proposed that lead vacancies are responsible for non-radiative recombination in when exceeding stoichiometric ratios. The various phase stabilities responsible for the lead deficient CsPbBr3 phase were identified via UV-VIS signatures. In the process, a new lead bromide magic-sized cluster was identified. Transformations of this magic-sized cluster were investigated. A ligand-mediated transformation from magic-sized cluster to an intermediate species was identified. Consequently, further comprehension of the formation of larger lead bromide perovskites was achieved. Exciton diffusion measurements of 2D arrays of the optically efficient CsPbBr3 suggest high inter-nanocrystal coupling. This was achieved through the investigation of the diffusivity of the charge transfer process as a function of temperature. Non-Arrhenius like behavior proves signatures of exciton delocalization over multiple quantum dots.

Lithium-ion batteries have been growing rapidly for the past few decades, finding applications in portable devices such as cell phones, and laptop computers. Recently, the surging demand for electric vehicles and grid storage necessitates the development of safer batteries that offer higher performance, longer life, and lower cost. Spinel-type LiNi0.5Mn1.5O4 (LNMO) stands out as a promising cathode material for 5 V-class Li-ion batteries enabling high energy density and low material costs. However, common carbonate-based liquid electrolytes suffer from oxidative decomposition under high voltage, resulting in continuous cell degradation. In contrast, certain solid-state electrolytes have a wide electrochemical stability range and can withstand the required oxidative potential. In this study, we test a thin-film battery comprising an LNMO cathode with a solid lithium phosphorus oxynitride (LiPON) electrolyte and characterized their interface before and after cycling. Utilizing Li metal as the anode, this system can deliver stable performance for 600 cycles with an average Coulombic efficiency exceeding 99%. Neutron depth profiling reveals a slight overlithiated layer at the interface prior to cycling, a result that is consistent with the excess charge capacity measured during the first cycle. Additionally, cryogenic electron microscopy indicates intimate contact between LNMO and LiPON without any noticeable structure or chemical composition evolution after extended cycling, underscoring the superior stability of LiPON against a high voltage cathode. These findings accelerate the commercialization of a high voltage cell with solid or liquid electrolytes.In addition to thin film batteries, the thin film platform of battery materials offers another potential application in the form of a resistive switching device for future computing. With conventional silicon-based memory devices approaching their quantum mechanical limits, it is imperative to seek new functional materials to replace them. Therefore, in this thesis, solid-state electrolyte lithium lanthanum titanate (LLTO) is explored as a resistive switching device, and its material properties are investigated through micro and macroscopic characterization. Electronic conductivity changes that provoke the LLTO switching are investigated experimentally and computationally through the comparison of LLTO with different oxygen compositions, under the hypothesis that oxygen vacancy plays a role in altering local LLTO conductivity. Based on those data, switching mechanisms are proposed as filament growth created by local conductivity change through the simplified model.

Colloidal copper phosphide (Cu3−xP) nanocrystals are attractive electronic materials due to their ability to support excess delocalized holes, with both synthesis and dynamic redox modulation allowing tuning of localized surface plasmon resonance (LSPR) absorption in the near-IR. This dissertation presents developments in the colloidal syntheses and post-synthetic redox chemistries of high-quality Cu3−xP nanoplatelets with the attainment of tunable nanocrystallite lateral sizes, LSPR energies, compositions, and optoelectronic properties. A one-pot, colloidal synthesis of Cu3−xP nanoplatelets with copper halide salt and aminophosphine in the presence of oleylamine is presented in Chapter 2. The reactivity of an in situ copper-phosphorus precursor is modulated by varying precursor composition and coordinating solvent ratio to tune nanocrystal lateral size. Oleylamine-to-aminophosphine molar ratio is found to alter particle nucleation activity and access atom-efficient size tuning. By modulating precursor reactivity, the syntheses presented in Chapter 2 are used to access nanocrystals with lateral sizes of 6.1–23 nm and LSPR energies of 709–861 meV. The low polydispersity, size- and LSPR-tunability and colloidal stability make aminophosphine-synthesized Cu3−xP nanocrystals promising candidates for investigations into factors governing their LSPR energy, around which the findings of the subsequent chapter are based. Three copper-coupled redox chemistries are presented in Chapter 3 which allow post-synthetic modulation of the delocalized hole concentrations and corresponding LSPR absorption in colloidal Cu3−xP nanocrystals. Changes in the structural, optical, and compositional properties are evaluated by powder X-ray diffraction, electronic absorption spectroscopy, 31P magic-angle spinning solid-state nuclear magnetic resonance spectroscopy and elemental analysis. The redox chemistries are shown to access nanocrystals with LSPR energies of 660–890 meV, a larger range than has been possible through synthetic tuning. The largest structural and LSPR modulation is achieved through the use of a divalent metal halide and trioctylphosphine, with the smallest reported unit-cell volume (295.2 Å3) and most downfield 31P chemical shift (+346 ppm) reported for P63cm Cu3−xP. In Chapter 4, the platform for systematic mechanistic investigations developed in Chapter 2 is extended to use copper phosphide as a model system for the study of aminopnictine precursor chemistry and the elucidation of metal pnictide nanocrystal formation mechanisms. Preliminary findings are presented for the investigation of the synthetic roles of copper salt counteranion and aminophosphine amide identity.

The interaction of light with a small metallic particle creates a strong local electromagnetic wave that can be exploited in the public health arena for photochemistry, biosensing, drug delivery and more. In this dissertation, I discuss the synthesis and application of two different nanoparticles for public health, zirconium nitride (ZrN) and yttria-stabilized zirconia (YSZ). ZrN is investigated as an alternative plasmonic material to efficiently convert the sun’s visible radiation into chemical energy to remove heavy metals from water. The photothermal and photelectric mechanisms of plasmonic ZrN particles are considered and characterized. YSZ is proposed as a ceramic cranial implant for the improvement of diagnostic and treatments of brain disorders. YSZ nanoparticles synthesized with an Aerosol Spray Pyrolysis system are densified with a Spark-Plasma Sintering process to obtain dense bulk nanostructure. I work to optimize the mechanical properties of 3YSZ with the optical properties of 8YSZ. Additionally, I comment on the potential for nanotechnology to contribute to public health.

Metallic nanocrystals have gained growing interest in photocatalysis applications due to their robust nature for multicycle operation, strong light absorption, and relatively new catalytic mechanisms. Historically, photocatalysis induced by localized surface plasmon resonance (plasmon resonance for short) of these particles has been studied widely for more than a decade, but photocatalysis originating from interband transitions is still underexplored. In order to build a comprehensive map from photon utilization to hot-carrier harvesting, and related photocatalysis, the systematic comparison between plasmon resonance and interband transition needs to be conducted in light of hot carriers-mediated reaction. The energy levels, population, dynamics, and heating effect of those hot carriers, and as followed, the charge transfer, reaction pathway, and kinetics are all necessary to be discussed. In this dissertation, the physical picture and related properties of interband transition and plasmon resonance are reviewed, then some systematic approaches to evaluate these two excitations are demonstrated. As follows, the porous Palladium nanoparticles as the model catalysts with dominant spectra features corresponding to the interband transitions were employed for mechanistic insights. We have demonstrated that under shorter wavelengths, deeper holes in the d-band can catalyze the oxidative addition of aryl halide R-X onto Pd0 at the nanoparticles’ surface to form R-PdII-X complex, thus accelerating the rate-determining step of the catalytic cycle, eventually increase the quantum yield of photocatalyzed Suzuki-Miyaura reactions. In the meantime, we have proved and quantified the effect of photocharging towards nanoparticle photocatalysis, as an underlying and often overlooked mechanism. We have built a proportional relation between accumulated charge and separate catalytic performance, which should deserve more attention in the future. Furthermore, we have been exploring the possibility of using earth-abundant metals for sustainable photocatalysis and utilizing the intrinsic interband transitions in these metals to search for new catalytic properties. Combined with the electronic and band structure of Au, Pd, and Co metals, we have rationalized the interband transitions in the metal-adsorbate hybridized states of those three metals and confirmed the contribution of both interaction strength between metal and adsorbates and energy states of hot carriers from interband transitions to photocatalysis. And the cobalt-based metallic nanoparticle photocatalysts were proved to be a good candidate for designing better energy alignment between the d-band structure and interband transition than Au and Pd nanoparticles, which leads us to shift from noble to non-noble metallic nanoparticle photocatalyst and a sustainable future. Eventually, we have provided some future perspectives towards the design for non-noble-metal-based nanoparticle photocatalysts and related mechanistic insights of the hot-carrier behavior from interband transitions.