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In this work, the use of a ZnO-nanowire (NW)-based heterojunction array structure for application to UV sensors is proposed. Nano-heterojunction arrays (NHAs) were formed via the oblique-angle sputtering deposition of p-type tin monoxide onto vertically aligned ZnO-NWs grown by hydrothermal growth (HTG). The current density-voltage (J-V ) curve in darkness shows that the prepared SnO/ZnO-NW NHAs have rectifying current-voltage characteristics. They also exhibit a superior response to UV (254 nm) light illumination. The optoelectronic properties of the SnO/ ZnO-NW NHAs with different SnO thicknesses (50-1000 nm) under different UV light intensities (2-6 mW/cm 2 ) were investigated and discussed. UV sensitivity (I UV =I dark ) as high as 8.5 was obtained. #

The use of a TiO2 nanowire (NW) hydrothermally grown on an fluorine-doped tin oxide (FTO) substrate as a separated sensing electrode of an extended-gate field-effect-transistor (SE-EGFET) pH sensor is demonstrated. Sensing responses to the prepared samples in a wide pH range (2–12) are presented and compared with responses of a film-type TiO2 electrode. The pH sensors with the NW-type and film-type electrodes show a sensitivity of 62 and 50 mV/pH, respectively, and a comparably good linearity in the pH range of 2–12. The superiority of the NW-type TiO2 electrode (24% improvement in sensitivity compared with that of the film-type electrode) is attributed mainly to the higher surface-to-volume (SV) ratio and higher conductivity of the hydrogen thermal growth (HTG) nanowires.

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A new two-step hydrothermal growth (HTG) process with a shorter processing time and better growth control is proposed for the synthesis of ZnO nanotapers (NTs). The application of HTG ZnO NTs as surface roughening nanostructures to improve the light output power (L op) of GaN-based LEDs is demonstrated. Compared with that of ZnO nanowires, the use of ZnO NTs leads to an improvement in L op by 24.5% at 350 mA, which could be attributed to the fact that tapered ends of ZnO NTs offer more constructive photon scattering to maximize light extraction.