Preparation of high-aspect-ratio ZnO nanorod arrays for the detection of several organic solvents at room working temperature

• Published in: Applied surface science 2013-11, Vol.285, p.241-248
• Main Authors: Lee, Yi-Mu, Zheng, Min-Ren
• Format: Article
• Language: English
• Subjects: Chemical sensor; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Ethanol; Exact sciences and technology; High-aspect-ratio ZnO; Impedance measurement; Organic solvent detection; Physics
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2013.08.046

•High-quality and high-aspect-ratio (value ∼28) ZnO nanorod arrays have been prepared by CBD for the detection of organic solvents.•For sensing characteristics, electrical impedance spectroscopy (EIS) was employed to provide more insight into the charge transfer mechanism under low and high frequency range.•The ZnO sensor exhibits highest sensitivity and selectivity for the detection of methanol.•The sensing properties have been correlated to the dielectric properties and dipole moment of the solvent molecules adsorpted on the ZnO surface.•The ZnO nanorod arrays exhibit great stability for the detection of methanol and ethanol with low concentration (1%, v/v). Chemical sensors based on ZnO nanorod arrays were prepared using chemical bath deposition (CBD) to investigate the sensing performance for the detection of several organic solvents with low concentrations (0.1%, 0.5%, 1%, v/v) at room temperature. High quality and high aspect-ratio (value ∼28) ZnO nanorods have a diameter of about 74nm and average length of 2.1μm. Nyquist plots and Bode plots of the ZnO sensors under different organic solvents were obtained by electrical impedance spectroscopy (EIS). The sensing properties such as charge-transfer resistance, double-layer capacitance and dielectric parameters were determined from the impedance spectra to explore the charge transport in low-concentration aqueous solutions. The decreasing trend of the charge-transfer resistance (Rct) as decreasing solvent concentrations is observed, and a straight line at low frequency regime indicates adsorption of water molecules on the oxide surface. The sensitivity of the ZnO sensors was calculated from the resistance variation in target solvents and in deionized water. We demonstrated the use of ZnO nanorod arrays as a chemical sensor capable of generating a different response upon exposure to methanol, ethanol, isopropyl alcohol, acetone and water, wherein the methanol sensing exhibited highest sensitivity. In addition, the ZnO sensor also demonstrates good stability and reproducibility for detection of methanol and ethanol.