ZnO nanorods were successfully fabricated on Zn foil by chemical bath deposition (CBD) method. The ZnO precursor concentration and immersion time affected the surface morphologies, structure, and electrical properties of the ZnO nanorods. As the precursor concentration increased, the diameter of the ZnO nanorods increased from ca. 50 nm to ca. 150 nm. The thicknesses of the ZnO nanorods were from ca. 1.98 µm to ca. 2.08 µm. ZnO crystalline phases of (100), (002), and (101) planes of hexagonal wurtzite structure were confirmed by XRD measurement. The fabricated ZnO nanorods showed a photoluminescene property at 380 nm. Especially, the ZnO nanorods deposited for 6 h in solution with a concentration of 0.005 M showed a stronger (101) peak than they did (100) or (002) peaks. In addition, these ZnO nanorods showed a good electrical property, with the lowest resistance among the four samples, because the nanorods were densely in contact and relatively without pores. Therefore, a ZnO nanorod substrate is useful as a highly sensitive biochip substrate to detect biomolecules using an electrochemical method.

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Quartz crystal microbalance (QCM) gas sensor to detect methyl mercaptan (CH 3 SH) gas was fabricated by depositing TiO 2 nanoparticles and polyelectrolyte on the electrode of QCM. The TiO 2 /poly(sodium 4-styrenesulfonate) (PSS) thin film fabricated by a layer-by-layer self-assembly (LBL-SA) method showed a high surface area and increased the sensitivity of gas sensor. When the QCM sensors coated with triethanolamine (TEA) or (TiO 2 /PSS) were exposed to methyl mercaptan gas (1.0 ppm), the frequency shifts of QCM with TEA casting film and TiO 2 /PSS thin film were ca. 9 Hz and ca. 24 Hz, respectively. As the bilayer number of (TiO 2 /PSS) increased, the frequency shift of QCM sensor with (TiO 2 /PSS) thin film was gradually increased. In addition, the frequency shift of QCM sensor was gradually increased as the concentration of methyl mercaptan gas increased from 0.5 ppm to 2.0 ppm. In this study, the surface morphology and sensor property of QCM sensor coated with (TiO 2 /PSS) thin film were measured.