With their simple fabrication, narrow light spectrum, and color tunability, a class of materials known as perovskites are emerging as promising candidates for light emission applications. These materials, when exposed to normal atmospheric conditions show significant degradation. Improved protection has been demonstrated by embedding perovskites in polymers. Furthermore, the addition of a surfactant into the precursor solution has been shown to increase stability and allow for color tuning by exploiting quantum confinement effects. However, the effects of surfactants typically used to stabilize perovskites in solution have not been explored in this polymer embedding strategy. Here we determine the physical and optical emission changes produced by modifying the concentration of octylamine, butylamine, and oleylamine in the perovskite precursor solution prior to embedding into a polystyrene substrate. Using optical emission spectroscopy, we measure emission spectra of perovskite nanocrystals embedded in the polymer. Changes in morphology and dispersion of the perovskite particles within the polymer are observed using UV illuminated optical microscopy. XRD data suggests increased crystallinity with the addition of short chain surfactant. Our measurements in emission show that the location of the emission peak and overall shape of the emission spectra change when longer chain surfactant is added while short chain surfactant reduces nanorod formation without a significant change in particle dispersion or emission. The work suggests that increased long chain surfactant concentration prohibits perovskite crystal growth within the polymer leading to increased optical transparency and quantum confinement effects observable through photo luminescent emission.

The rapid advancement of portable and wearable technologies has challenged research to improve upon current renewable battery energy storage systems. By using nanotechnology, it is now possible to access more of the energy storage theoretical values that have been unattainable thus far. We have developed a method to create freestanding holey thin films through combinations of electrochemical and chemical vapor deposition (CVD) techniques to be used in renewable energy storage systems. Freestanding thin films promote excellent contact between the residual conductive framework and any functionalized active component specific to the designed material. Without requiring any other additives, the as-prepared freestanding thin films can be mechanically and chemically tuned to allow for use in a wide range of applications. Incorporation of micro- and nano-sized holey structures dramatically enhances the electrochemically active surface area, which is essential for facilitating appropriate reactions in conversion type energy storage systems. Combining the freestanding and holey components with an active layer effectively enhances conductivity and reduces the electron transfer distance at the electrode-electrolyte interface. Herein, two separately designed freestanding holey thin films were successfully used as cathode materials for lithium-sulfur battery (Li-S) and magnesium-ion battery (MIB) energy storage systems.

Quantum Cascade Lasers have recently gained considerable attention for their capability to emit infrared radiation in a broad infrared spectral region, very compact dimensions, and high optical power/efficiency. Increasing continuous wave optical power is one of the main research directions in the field. A straightforward approach to increasing optical power in the pulsed regime is to increase number of stages in the cascade structure. However, due to a low active region thermal conductivity, the increase in number of stages leads to active region overheating in continuous wave operation. In this work, an alternative approach to power scaling with device dimensions is explored: number of stages is reduced to reduce active region thermal resistance, while active region lateral size is increased for reaching high optical power level. Using this approach, power scaling for active region width increase from 10µm to 20µm is demonstrated for the first time. An analysis based on a simple semi-empirical model suggests that laser power can be significantly improved by increasing characteristic temperature T0 that describes temperature dependence of laser threshold current density.

Thesis (M.S.)--Rowan University, 2009. / Typescript. Includes bibliographical references.

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

<p> The electron microscope is an ideal tool to prepare an electron into a specified quantum state, entangle that state with states in a specimen of interest, and measure the electron final state to indirectly gain information about the specimen. There currently exist excellent technologies to prepare both momentum eigenstates (transmission electron microscopy) and position eigenstates (scanning transmission electron microscopy) in a narrow band of energy eigenstates. Similarly, measurement of the momentum and position final states is straightforward with post-specimen lenses and pixelated detectors. Measurement of final energy eigenstates is possible with magnetic electron energy loss spectrometers. In 2010 and 2011, several groups independently showed that it was straightforward to prepare electrons into orbital angular momentum eigenstates. This disseratation represents my contributions to the toolset we have to control these eigenstates: preparation, application (interaction with specimen states), and measurement. My collaborators and I showed that phase diffraction gratings efficiently produce electron orbital angular momentum eigenstates; that control of orbital angular momentum can be used to probe chirality and local magnetic fields; and that there are several routes toward efficient measurement.</p><p>

In this work we study three systems of biological interest: the translocation of a heterogeneously charged polymer through an infinitely thin pore, the wrapped of a rigid particle by a soft vesicle and the modification of the dynamical properties of a gel due to the presence of rigid inclusions. We study the kinetics of translocation for a heterogeneously charged polyelectrolyte through an infinitely narrow pore using the Fokker-Planck formalism to compute mean first passage times, the probability of successful translocation, and the mean successful translocation time for a diblock copolymer. We find, in contrast to the homopolymer result, that details of the boundary conditions lead to qualitatively different behavior. Under experimentally relevant conditions for a diblock copolymer we find that there is a threshold length of the charged block, beyond which the probability of successful translocation is independent of charge fraction. Additionally, we find that mean successful translocation time exhibits non-monotonic behavior with increasing length of the charged fraction; there is an optimum length of the charged block where the mean successful translocation time is slowest and there can be a substantial range of charge fraction where it is slower than a minimally charged chain. For a fixed total charge on the chain, we find that finer distributions of the charge along the chain leads to a significant reduction in mean translocation time compared to the diblock distribution. Endocytosis is modeled using a simple geometrical model from the literature. We map the process of wrapping a rigid spherical bead onto a one-dimensional stochastic process described by the Fokker-Planck equation to compute uptake rates as a function of membrane properties and system geometry. We find that simple geometrical considerations pick an optimal particle size for uptake and a corresponding maximal uptake rate, which can be controlled by altering the material properties of the membrane. Finally, we use a mean field approximation, neglecting correlations among the embedded particles, to examine the effect of inclusions in a viscoelastic medium on the effective macroscopic properties of the gel. We find an essentially linear dependence of both components of the complex shear modulus up to arbitrary volume fractions of the inclusions, in contradiction to experimental observations. We conclude that the incorporation of correlations among the particles is needed in order to explain experiments, in analogy with the elastic case.

No description available.

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

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