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ZnO nanorods were prepared via a hydrothermal reaction in a solution containing Zn(NO 3 ) 2 ·6H 2 O, NaOH, cyclohexylamine, ethanol and water, and their NO 2 and CO sensing behaviors were investigated. The morphology and agglomeration of ZnO nanorods could be manipulated by controlling the amount of water in the solution, which was explained by the variation in the [OH − ] due to an interaction between the water and cyclohexylamine. Sea-urchin-like and well-dispersed ZnO nanorods were prepared at low and high water content, respectively. Well-dispersed ZnO nanorods showed 1.8 fold change in resistance at 1 ppm NO 2 while there was no significant change in resistance at 50 ppm CO. The present ZnO nanorods can be used in automated car ventilation systems to detect NO 2 in the presence of CO.

A new method for preparing SnO 2 whiskers by the decomposition of SnC 2 O 4 is suggested. A Whisker-like morphology of a SnC 2 O 4 precipitate was attained via the gradual addition of an oxalic acid solution to a hot SnCl 2 aqueous solution (T > 50 • C). In comparison, when the solution temperature was either lower than 50 • C or when ethanol was used as the solvent, the SnC 2 O 4 precipitate showed an angular and relatively isotropic morphology. The morphology of the SnC 2 O 4 precipitate remained even after its thermal decomposition into SnO 2 at 400 • C indicating that SnC 2 O 4 precipitation is a key step in preparing the whiskers. The formation mechanism of SnO 2 whiskers was explained by the supersaturation during the precipitation of SnC 2 O 4 .

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