Uniform SnO2 nanorod arrays have been deposited at low temperature by plasma‐enhanced chemical vapor deposition (PECVD). ZnO surface modification is used to improve the selectivity of the SnO2 nanorod sensor to H2 gas. The ZnO‐modified SnO2 nanorod sensor shows a normal n‐type response to 100 ppm CO, NH3, and CH4 reducing gas whereas it exhibits concentration‐dependent n–p–n transitions for its sensing response to H2 gas. This abnormal sensing behavior can be explained by the formation of n‐ZnO/p‐Zn‐O‐Sn/n‐SnO2 heterojunction structures. The gas sensors can be used in highly selective H2 sensing and this study also opens up a general approach for tailoring the selectivity of gas sensors by surface modification.

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SnO 2 thin films were deposited by radio-frequency inductively coupled plasma-enhanced chemical vapor deposition. Postplasma treatments were used to modify the microstructure of the as-deposited SnO2 thin films. Uniform nanorods with dimension of ∅7×100nm were observed in the plasma-treated films. After plasma treatments, the optimal operating temperature of the plasma-treated SnO2 thin films decreased by 80 °C, while the gas sensitivity increased eightfold. The enhanced gas sensing properties of the plasma-treated SnO2 thin film were believed to result from the large surface-to-volume ratio of the nanorods’ tiny grain size in the scale comparable to the space-charge length and its unique microstructure of SnO2 nanorods rooted in SnO2 thin films.

TiO2 nanorod (NR) and nanotube (NT) arrays grown on transparent conductive substrates are attractive electrode for solar cells. In this paper, TiO2 NR arrays are hydrothermally grown on FTO substrate, and are in situ converted into NT arrays by hydrothermally etching. The TiO2 NR arrays are reported as single crystalline, but the TiO2 NR arrays are demonstrated to be polycrystalline with a bundle of 2-5 nm single crystalline nanocolumns grown along [001] throughout the whole NR from bottom to top. TiO2 NRs can be converted to NTs by hydrothermal selective etching of the (001) core and remaining the inert sidewall of (110) face. A growth mechanism of the NR and NT arrays is proposed. Quantum dot-sensitized solar cells (QDSCs) are fabricated by coating CdSe QDs on to the TiO2 arrays. After conversion from NRs to NTs, more QDs can be filled in the NTs and the energy conversion efficiency of the QDSCs almost double.