Nickel oxide(NiO) thin films, nanorods, and carbon nanotube(CNT)/NiO core-shell nanorod structures are fabricated by sputtering Nickel at different deposition time on alumina substrates or single wall carbon nanotube templates followed by oxidation treatments at different temperatures, 400 and 700 oC. Structural analyses are carried out by scanning electron microscopy and x-ray diffraction. NiO thinfilm, nanorod and CNT/NiO core-shell nanorod structurals of the gas sensor structures are tested for detection of H2S gas. The NiO structures exhibit the highest response at 200 oC and high selectivity to H2S among other gases of NO, NH3, H2, CO, etc. The nanorod structures have a higher sensing performance than the thin films and carbon nanotube/NiO core-shell structures. The gold catalyst deposited on NiO nanorods further improve the sensing performance, particularly the recovery kinetics.

Hydrothermal synthesis of highly crystalline TiO2 nanorods is a well-developed technique and the nanorods have been widely used as the template for growth of various core-shell nanorod structures. Magneli/CdS core-shell nanorod structures are fabricated for the photoelectrochemical cell (PEC) electrode to achieve enhanced carrier transport along the metallic magneli phase nanorod template. However, the long and thin TiO2 nanorods may form a high resistance path to the electrons transferred from the CdS layer. TiO2 nanorods synthesized are reduced to magneli phases, TixO2x-1, by heat treatment in a hydrogen environment. Two types of magneli phase nanorods of Ti4O7 and Ti3O5 are synthesized. Structural morphology and X-ray diffraction analyses are carried out. CdS nano-films are deposited on the magneli nanorods for the main light absorption layer to form a photoanode, and the PEC performance is measured under simulated sunlight irradiation and compared with the conventional TiO2/CdS core-shell nanorod electrode. A higher photocurrent is observed from the stand-alone Ti3O5/CdS coreshell nanorod structure in which the nanorods are grown on both sides of the seed layer.