Templated synthesis and characterization for multi-segmented nanowires for sensor and optical device applications

Nanowires are one-dimensional, anisotropic nanocrystals with diameters generally ranging from 1--200 nm and lengths of up to several tens of microns. The most common methods of nanowire synthesis include chemical vapor deposition, solution phase synthesis, pressure injection, electrospinning, and electrodeposition. In this research, the electrodeposition method was utilized to synthesize both single and multi-segmented metal nanowires using anodized aluminum oxide (AAO) and polycarbonate (PC) membranes with varying pore diameters. Metal oxide nanowires were obtained through post-synthesis thermal annealing. Furthermore, the use of these nanowires in both sensing and optical applications is discussed.;Doping is an effective method that is utilized to change the properties of a material. In this research, different dopants, including indium, antimony, and nickel, were incorporated into the tin segment of the nanowires through the co-electrodeposition process. Thermal annealing of the doped tin nanowires resulted in doped tin oxide nanowires. One specific targeted application of the doped tin oxide nanowires is to increase the sensitivity and selectivity of the nanowire sensor devices. Characterization of the nanowires was conducted using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and x-ray photoelectron spectroscopy (XPS). Three- and five-segmented nanowires were fabricated, including Au-Sn/X-Au nanowires and Au-Pt-Sn/X-Pt-Au nanowires, in which X represents the dopant element. In the five- segmented nanowires, platinum is used as a barrier segment to prevent the inter-metallic diffusion between gold and tin. One segment pure tin nanowires with dopants were also fabricated. The doped nanowires were then used to fabricate sensor devices using either the top-down photolithography technique or bottom-up dielectrophoretic assembly.;In a separate project, electrodeposition was successfully utilized to fabricate cadmium sulfide (CdS) nanowires. Electrodeposition conditions were optimized to obtain good quality CdS nanowires using voltage control and deposition at elevated temperatures.;In the future, the doped tin oxide nanowires fabricated in this research will be implemented into sensor arrays for explosive and other gas or chemical detection. Doped metal oxide nanowire sensors or sensor arrays will be incorporated into a functional sensor system with data fusion, together with fluorescent polymer nanofiber sensors and surface acoustic wave (SAW) sensors that are being developed by other groups in an interdisciplinary team effort. For the CdS nanowire research, further experimentation is necessary to increase the yield of CdS nanowires and incorporate nanoscale lead-free solders onto these nanowires, which will be used as a nano-soldering technique for CdS nanowire assembly and integration.