Fabrication of Nanosized Island-Like CdO Crystallites-Decorated TiO(2) Rod Nanocomposites via a Combinational Methodology and Their Low-Concentration NO(2) Gas-Sensing Behavior

TiO(2)–CdO composite rods were synthesized through a hydrothermal method and sputtering thin-film deposition. The hydrothermally derived TiO(2) rods exhibited a rectangular cross-sectional crystal feature with a smooth surface, and the as-synthesized CdO thin film exhibited a rounded granular surface feature. Structural analyses revealed that the CdO thin film sputtered onto the surfaces of the TiO(2) rods formed a discontinuous shell layer comprising many island-like CdO crystallites. The TiO(2)–CdO composite rods were highly crystalline, and their surfaces were rugged. A comparison of the NO(2) gas-sensing properties of the CdO thin film, TiO(2) rods, and TiO(2)–CdO composite rods revealed that the composite rods exhibited superior gas-sensing responses to NO(2) gas than did the CdO thin film and TiO(2) rods, which can be attributed to the microstructural differences and the formation of heterojunctions between the TiO(2) core and CdO crystallites.