One Dimensional Oxides, Sulfides Nanomaterials: Synthesis, Functionalization And Applications

One-dimesional nanomaterial exhibits unique physical and chemical properties because of its spatial dimension. Therefore, it plays important role in a wide range of fields such as catalysis, biochemical sensor, lithium battery and et al. Meanwhile, it also shows broad prospect of apllication in nanoelectronics and functional devices. In recent years, related research on one-dimentional nanomaterial has become frontier field and research hotspot. So far, a large number of one-dimetional nanomaterials have been created with a high degree of control over the compositions, properties and practical applications. However, how to rationally design and controllably synthesize novel functional one-dimetional and related compound nanomaterials and to explore new application areas is still a great challenge.Through rational consideration of the research frontiers and possible requirements in practical applications of one-dimesional nanomaterials, this thesis mainly focuses on several aspects, including the rational design, controllable synthesis, structure manipulation, function regulation, formation mechanism and their applications in photoelectronics, electrochemical energy storage and biomedical areas. In addition, fabrication of large area of microvessel network in microfluidic device has been achieved in vitro and could be applied for tissue engineering and biodetection.In Chapter 2, we report for the first time the synthesis of two unconventional metal sulfide nanostrucutures by the chemical vapor deposition method. The key factor in our experiment for fine morphology and structure control of a variety of metal sulfide products is the tuning of growth conditions. For PbS, the formation of one-dimetional struture demands a VLS growth process while the pine tree structure has a simultaneous dislocation driven growth. For CuxS, the deposition and growth temperature is fitted for the surface energy barriers promoting growth directions that would not be allowed by conventional experimental methods. At a high growth temperature (480℃) that provides enough thermal energy, a 0-D octahedral Cu1.96S crystals with a cubic single crystal structure was firstly discovered. At a medium growth temperature (460℃), another new 1-D single crystal Cu1.96S nanorod structure with [111] growth direction was obtained. At a lower growth temperature (150℃),2-D CuS nanoflakes with a single crystal hexagonal structure were obtained. These novel structural varieties of metal sulfides may lead to discovering more unconventional material structures and growth mechanisms of other complex transitional metal chalcogenides, and can allow for new copper sulfide based devices for optoelectronic applications.In Chapter 3, we devise the synthesis of a highly uniform, hierarchically porous silica film structure, and its application in drug loading and release for antibacterial surface coating. Templated by both sub-micron poly-styrene (PS) particles and a triblock copolymer (F127), this hierarchically porous film has two distinct pore sizes of 7 nm and 200 nm. The 7-nm mesopores provide high surface area and thus high adsorption capacity for drug molecules, and the 200-nm macropores facilitate the adsorption rate of drug molecules, especially for molecules with comparable sizes to mesopores. Fluorescence measurement of rhodamine release demonstrates that this hierarchically porous film has higher adsorption capacity, efficiency and much longer molecule releasing time window than both the inverse opal film and the mesoporous film. When loaded with Ampicillin, this hierarchically porous film shows over 8 times longer of inhibition of E. coli growth than both the inverse opal film and the mesoporous film. This simple and versatile process allows for fabrication of a variety of surface-coated, hierarchical nanoporous films with different chemical compositions and applications.In Chapter 4, we demonstrate the synthesis of mesoporous carbon-coated molybdenum oxide nanocomposites, using a hydrothermal growth of MoO3 nanobelts, followed by an evaporation induced self-assembly process to coat mesoporous carbon layers. The obtained MoOx/mesoporous carbon nanocomposites provided a high surface area for electrochemical reaction, large mesopore channel for lithium ion transport, improved electrical conductivity, and structural flexibility for electrode volume change. Lithium-ion battery anode made of this nanocomposite showed substantial enhancement in lithium storage capacity, comparing to the anodes made of pristine MoO3 nanobelts or pure mesoporous carbons. In addition, since the second cycle, the Coulombic efficiency for MoOx/mesoporous carbon nanocomposite was almost maintained as> 95% which indicating an excellent cycling stability. Furthermore, this approach does not require any specific sample pre-treatment and can be applied in a large pH range of the precursor solutions, and thus may serve as a general method of interfacing with a variety of transitional method oxide nanostructures for energy conversion and storage.In Chapter 5, we report a simple method for the synthesis of controlled Sn-doping in TiO2 nanowire (NW) arrays for photoelectrochemical (PEC) water splitting. Due to the low lattice mismatch between SnO2 and TiO2, Sn dopants are incorporated into TiO2 NWs by a one-pot hydrothermal reaction with different ratios of SnCl4 and tetrabutyl titanate, and a high acidity of the reactant solution is critical to control the SnCl4 hydrolysis rate. The obtained Sn-doped TiO2 (Sn:TiO2) NWs are single crystalline with a rutile structure, and the incorporation of Sn in TiO2 NWs is well controlled in a low level, i.e.1-2% of Sn/Ti ratio, to avoid phase separation or interface scattering. PEC measurement on Sn:TiO2 NW photoanodes with different Sn doping ratios shows that the photocurrent increases first with increased Sn doping level to> 2.0 mA/cm2 at 0 V vs Ag/AgCl under 100 mW/cm2 simulated sunlight illumination, up to ～100% enhancement compared to our best pristine TiO2 NW photoanodes, and then decreases at higher Sn doping levels. Subsequent annealing of Sn:TiO2 NWs in H2 further improves their photoactivity, with an optimized photoconversion efficiency of～1.2%. The incident-photon-to-current conversion efficiency (IPCE) shows that the photocurrent increase is mainly contributed from the enhancement of photoactivity in the UV region, and the electrochemical impedance measurement reveals that the density of n-type charge carrier can be significantly increased by the Sn doping. These Sn:TiO2 NW photoanodes are highly stable in PEC conversion, and thus can serve as a potential candidate for pure TiO2 materials in a variety of solar energy driven applications.In Chapter 6, we develop a highly promising approach to achieve the generation of large-scale, perfusable micro-vessel networks using a microfludic network. The approach exploits a repeated seeding process that facilitates the formation of large-area, defect-free, interconnected, perfusable networks of endothelialized microvessels. Further characterization (e.g., cell-cell junction staining, shear-induced alignment, vWF secretion, and NO production) confirms the micro-vessels are structurally correct and biologically functional. To our best knowledge, this is the first report of de novo fabrication of large-scale, perfusable functional microvessel networks in a gel-free microfluidic system. The approach is highly repeatable, robust, and represents a significant advance in the field of micro-vascular tissue engineering and related-disease study.