Abstract: One-dimensional nanostructures are a promising class of basic building blocks for future optoelectronic, mechanical and energy conversion devices. Many of the most exciting device applications for inorganic nanowires, which capitalize on their shape and ability to guide electrons and photons, have heretofore not been explored, either experimentally or theoretically. This thesis describes several proof-of-concept studies that establish the feasibility of using nanowires as the central elements of four broad emerging technologies. For the first time, single ZnO and SnO₂ nanowires have been fabricated into photodetectors and chemical sensors for gases such as the smog-forming pollutant NO₂. Initial experiments to characterize their photoconducting behavior and understand their interaction with ambient gases have been performed with the aim of optimizing their performance. In a separate set of experiments, SnO₂ nanowires with rectangular cross-sections have been used as templates to create bilayer structures that function as nanoscale temperature sensors. Their thermomechanical behavior has been analyzed with in situ transmission electron microscopy techniques. These bilayer nanoribbons are among the first examples of a functional inorganic element engineered for use in nanoelectromechanical systems (NEMS). Recent work in this laboratory has focused on the fundamental optical physics of nanowire lasers. Here, for the first time, nanowires thinner than the wavelength of light are shown to act as versatile subwavelength waveguides that are suitable for signal routing and frequency filtering in integrated nanoscale optical circuitry. Again, SnO₂ nanoribbons have been chosen to showcase the nature of optical confinement in high-aspect-ratio subwavelength cavities. The length, flexibility and strength of oxide and nitride nanowires are leveraged to build nanowire source-waveguide-detector junctions and other prototype structures. Furthermore, the evanescent electromagnetic field surrounding the nanoribbons has been utilized to detect molecules in solution by absorbance and fluorescence. This is the first example of optical sensing with nanowires, and highlights their potential for the highly sensitive and specific sensing of biomolecules in microfluidic assays and in living tissue. The fourth major topic of this thesis work is the demonstration, for the first time, of nanowire-based photovoltaic devices. ZnO nanowire arrays have been synthesized by a low-temperature aqueous process that is sufficiently versatile to produce high-density arrays of single crystals with tunable aspect ratios and controllable orientation on various substrates. (Abstract shortened by UMI.)