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Metal oxide nanoparticles constitute an important class of nanomaterials which has have received tremendous attention due to their distinct, specific activities comparison to their bulk. Among these, cerium oxide nanoparticles (CeNPs) have displayed outstanding promise across a wide range of applications owing to their unique redox properties. Given that the physical and chemical characteristics of nanomaterials are significantly influenced by their morphologies and sizes, the development of well-controlled synthesis methods for CeNPs holds great importance in both scientific research and industrial applications. This dissertation seeks to peer into the formation of CeNPs in solution through wet chemical synthesis. Additionally, antioxidant properties of CeNPs were examined to explore the potential use of facet CeNPs in gene delivery and promoting wound healing for diabetic. The beginning of this work provides introduction and summary of some common concepts widely used in understanding of nanoparticles formation. In chapter two and three, the spontaneous hydrolysis behavior of tetravalent cerium salts in aqueous systems were studied in detail to understand the influence of synthesis condition on the nucleation kinetic and morphology evolution in the course of growth of nanoparticle. The results obtained from these studies offer constructive insights into designing a straightforward and controlled synthesis strategy for producing nanoclusters and faceted nanoparticles through wet chemical methods. Furthermore, in chapter five, we examine the impact of faceted CeNPs on biomolecule conjugation and their performance in gene delivery for the regulation of abnormal diabetic wound healing. Overall, by taking advantage of the intrinsic properties of tetravalence cerium salt, this work highlights how manipulation of spontaneous hydrolysis could lead to formation of particles with different nanostructure and physicochemical properties.

Hydroxyapatite (HAp) is an essential biomedical material. HAp’s shaping is an important topic in the area of implantology and scaffolding. This project took a novel and unique approach in attempting to to control the morphology of materials without varying parameters such as pH levels, types of solvents, pressure and reaction time. Present work studied the feasibility of controlling the morphology of hydroxyapatite (HAp), with micrometer scale molding and casting. Emphasis was placed on HAp cylinders and cubes of micrometer size. First, cylindrically shaped cavities were patterned and etched with photolithography methods and reactive ion etching techniques on a Si substrate. Cavities were filled with slurry of deionized water, commercially purchased HAp powder, and Darvan 811 dispersant. Samples were successfully sintered at 1250°C. The obtained samples resembled the cylindrical cavities they were caste in. Scanning electron microscopy (SEM) was used to characterize the size and shape of sintered samples. This technique demonstrates great potential in forming large amounts of homogeneously shaped samples of HAp or similar ceramics for prospective biomedical applications

Current state-of-the-art polymer solar cells adopt the bulk-heterojunction (BHJ) morphologies where the electron donors (i.e. conjugated polymer) and electron acceptors (i.e. fullerenes) as active layers are mixed in an intimate way. The phase separation that modulates the exciton diffusion and charge transport in the current BHJ morphology is an uncontrolled process and thus results in random domain sizes of the polymer/fullerene blend. In addition, the polymer and fullerenes in the blend are intrinsically two immiscible materials and they tend to undergo macrophase separation eventually, which leads to deteriorated device performance. One way to address the abovementioned issues is to attach fullerenes onto the polymers covalently or non-covalently, aiming at controlling the phase separations and suppressing the macrophase separation between the polymer and fullerenes. However, either the device performance or the morphology of the active layer is not satisfactory to meet our needs. In my dissertation, I combine block copolymer self-assembly and hydrogen bonding interactions to construct morphologies that are not only thermally stable, but also controllable on the nanoscale. The controllability of the blend morphologies is simply achieved by tuning the fullerene contents in the polymer/fullerene blend. Moreover, solar cells fabricated from such polymer/fullerene blends perform in a comparable way with the benchmark BHJ solar cell however with much enhanced device thermal stabilities. I believe this methodology will shed light on the polymer design and morphology control for the chemists and engineers in this field to obtain high-performing solar cells with better thermal stabilities. Specifically, I started this project by synthesizing the poly(3-hexylthiophene) (P3HT) based all-conjugated block copolymer (BCP) (P4) selectively functionalized with diaminopyrimidine moieties and a thymine tethered fullerene derivative (F1). Strong interactions between P4 and F1 through the 'three-point' complementary hydrogen bonding are studied by 1H NMR spectroscopy, fluorescent spectroscopy, differential scanning calorimetry (DSC) and atomic force microscopy (AFM). Solar cells employing P4 and F1 at different weight ratios as active layers are fabricated and tested. Although the photovoltaic performances of P4/F1 solar cells were not good, the morphology of the blend exhibited tunable nature simply by adjusting the F1 ratios in the blend. Secondly, I modified the synthesis of the BCP and obtained a polythiophene diblock copolymer selectively functionalized with 1-N-hexyl isoorotic acid (IOA) moieties (P8) with a longer P3HT block and a 2, 6-diaminopyridine tethered fullerene derivative (F2). Solar cells employing P8 blended with different weight ratios of F2 and phenyl-C61-butyric acid methyl ester (PCBM) were fabricated and tested. The best power conversion efficiencies (PCEs) were observed in devices made from P8/F2 blends (10/8 by wt.) and ternary blends of P8/F2/PCBM (10/4/4 by wt.) as active layers, which is much better than those from P4/F2 blends. Thermal stabilities of these solar cells were studied in detail by aging tests and corresponding morphological changes were closely monitored by absorption spectroscopy, optical microscopy, AFM and X-ray analyses. The 'three-point' complementary hydrogen bonding interactions between P8 and F2, in cooperation with block polymer self-assembly, were found to not only improve the thermal stability of solar cells significantly but also lead to tunable active layer morphologies. Nanostructures with long-range order were identified in blend films employing P8, which has never been observed before in conventional polymer/fullerene bulk heterojunction (BHJ) films. Thirdly, by employing the P8/PCBM blend, I further developed a novel methodology of constructing stable and controllable conjugated polymer (CP)/fullerene nanostructures. By building in non-covalent interactions between CP nanofibers (NFs) and fullerene derivatives, supramolecular polymer/fullerene composite NFs are obtained in solution for the first time. Specifically, self-assembly of P8 in mixed solvents leads to well-defined NFs decorated with IOA groups on the periphery, onto which PCBM molecules are subsequently attached non-covalently. Formation of such complex structures are studied in detail and confirmed by UV-Vis absorption spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), and X-ray scattering measurements. Application of these composite NFs (P8/PCBM 10/4, wt/wt) in organic photovoltaic (OPV) devices not only leads to superior performance but also much improved thermal stability and rarely observed long-range ordered morphology, when compared with conventional bulk heterojunction (BHJ) devices. Last but not least, I also investigated the P8/F2 composite nanofibers formation and found out that the width of the composite nanofibers not only depends on the type of the fullerenes added, but also the amount of fullerenes mixed in the blends. Besides, solar cells fabricated from the composite nanofibers blends outperformed their conventional BHJ devices under the same fabricating conditions. Through 1H NMR observations, I also proposed a formation mechanism of the P8 nanofibers that agrees well with our experimental results.

Abstract: As one of the most commonly applied semiconductors, nanostructured silicon has received considerable attention over the past several decades due to its suitable band gap for light harvesting (1.2 eV for bulk crystal and up to 1.9 eV for nanocrystals), unique tunable photoluminescence (PL) and high biocompatibility and low toxicity. Significant effort has been made to fabricate and optimize silicon nanocrystal (SiNC) based devices. However, numerous important fundamental questions still remain. Therefore, this thesis mainly focuses on the elucidation of several fundamental research topics in the SiNC area, including nanocrystalline morphology control and evolution, surface functionalization and corresponding optical response of SiNCs, as well as the synthesis of particle/polymer hybrid materials. The thesis starts with an introduction about physical and chemical properties of SiNCs, general synthetic approaches, the present strategies of morphology control, as well as numerous surface modification approaches. Then details of a convenient method for preparing alkyl-functionalized silicon nanocubes are provided in Chapter Two with discussions about the mechanism of the particle size and shape control. Chapter Three focuses on the “one-pot” synthesis of homogenous SiNC/polystyrene hybrid materials. Also, three prototype micro/nano structures were fabricated for the demonstration of the utility of material hybrid characteristics such as bright photoluminescence (PL), high solvent processability and chemical stability. In Chapter Four, surface functionalization of SiNCs via thermally induced hydrosilylation is reexamined. The successful ligand functionalization processed at various temperatures under air atmosphere and the formation of ligand oligomers on SiNCs were noticed. These strongly suggest that an alternative mechanism exists to promote low temperature thermal hydrosilyaltion as well as ligand oligomerization on SiNCs. The potential influence of surface oxide species on SiNC optical properties is further described in Chapter Five. Based on a systematic study, it is clear that the surface defects or traps created by suboxides are strongly relevant to the non-phonon assisted nanosecond PL lifetime decay found from yellow/orange emitting ligand-functionalized SiNCs. Finally, Chapter Six presents the conclusions of each chapter and some recommended future work relative to SiNC science.

Fumaric acid is an important specialty chemical with wide applications as a food acidulant and as the chemical feedstock for the production of resins, plasticizers, and miscellaneous industrial products. Currently, fumaric acid is produced through a petroleum-based chemical method. Fungal fermentation provides a promising alternative method due to its advantages in environmental friendliness and availability of widespread renewable biomass feedstock. However, conventional fumaric acid fermentation processes suffer from low product yield, low productivity, and high production cost, whereas the competing chemical production methods are currently more economical. Therefore, the goal of this research was to develop effective and economic fermentation and recovery methods for improved fumaric acid production by Rhizopus oryzae. One of the major technical challenges is to control the fungal morphology and physiology for the overproduction of fumaric acid in a sustainable and scalable way. First, an effective fermentation process with good morphology control was developed using soybean meal hydrolysate as the nitrogen source for cell growth and fumaric acid production by R. oryzae. Uniformly dispersed mycelial clumps with a diameter of ~0.1 mm were formed with enhanced subsequent fumaric acid production. The fermentation reached a product titer of 50.2 g/L with yield of 0.72 g/g glucose. SMH with a high protein content was demonstrated as a good nitrogen source and the formation of protein precipitate acted as the immobilization carriers for cells. The solid-phase protein also provided a novel method for slow/controlled release that allowed the utilization of the nitrogen source by cells for an extended period without losing cell activity. The fermentation was then studied in a 5-L stirred tank bioreactor (STB) and the results also showed that using SMH as the nitrogen source improved fumaric acid production with increased yield and productivity compared to urea. Aeration with air containing 16.7% CO2 increased the productivity by 76% and product titer by 13%. To improve the productivity, in situ product recovery by coupling the fermentation with an ion exchange column for fumaric acid adsorption was investigated. A strong-basic anion exchange resin IRA900 was selected due to its high adsorption capacity at fermentation-favored pH of 5.0, and high selectivity against byproducts. The adsorption isotherm and the mechanism involved were investigated. A preliminary study showed that fermentation with intermittent in situ recovery enhanced product yield by 25% and productivity by 59%. In order to recover the low-concentration fumaric acid (98%. Compared to the conventional recovery process using precipitation, although this new process require additional capital investment, with the reduced operational costs and enhanced the recovery yield it is economically and environmentally favorable with good potential for industrial application.

For advanced applications of porous materials, morphology control of porous materials is desired. Simultaneous dissolution and surfactant-induced re-assembly via micelle formation with dissolved species were performed to introduce mesoporosity in the amorphous silica spheres and zeolite crystals. Textural features of mesoporous silica spheres were controlled from corrugated to smooth. Mesoporous zeolite catalysts were synthesized via surfactant-induced re-assembly with dissolved crystal fragments of zeolite crystals. In addition, the concept of confined synthesis was used for control of morphologies of zeolite crystals. Using 3-D ordered macroporous (3DOM) carbon as a template, growth patterns and shape development of zeolite crystals were studied. Various shaped zeolite crystals, e.g., hollow interior (geode-like structure), corrugated/smooth surface of polycrystalline crystals, needle-shaped crystals and 3DOM imprinted single crystals, were produced by careful choice of reaction parameters during the confined synthesis. Polycrystalline aggregates produced by the confined synthesis were used as seed particles for zeolite membrane fabrication. Novel seeding techniques, rubbing and leveling methods, were applied to deposit the confinement product directly on the surface of porous alumina supports, and zeolite membranes were grown by secondary hydrothermal growth. Moreover, rapid thermal processing and conventional calcination were used to investigate the effect of thermal treatments on the overall membrane quality. To evaluate the membrane quality, permeation measurements to separate p-/o-xylene isomers based on the zeolite's intrinsic capability of size-selective molecular separations were conducted. A high separation factor and high permeance were observed.