Application of electrochemically deposited nanostructured ZnO layers on quartz crystal microbalance for NO₂ detection

The research was fixed on sensing behavior of ZnO nanostructured (NS) films to NO₂ concentrations in the environment. The ZnO NS layers are deposited by electrochemical method on quartz resonators with Au electrodes. The sorption properties of ZnO layers were defined by measuring the resonant frequency shift (Δf) of the QCM-ZnO structure for different NO₂ concentrations. The measurements were based on the correlation between the frequency shift of the QCM and additional mass loading (Δm) on the resonator calculated using Sauerbrey equation for the AT-cut quartz plate. Frequency – Time Characteristics (FTCs) of the samples were measured as a function of different NO₂ concentrations in order to define the sorption abilities of ZnO layers. The experiments were carried out on a special set up in a dynamical regime. From FTCs the response and the recovery times of the QCM-ZnO structure were measured with varying NO₂. Frequency shift changed from 23 Hz to 58Hz when NO₂ was varied in the range of 250ppm – 5000ppm. The process of sorption was estimated as reversible and the sorption as physical. The obtained results demonstrated that QCM covered with the electrochemically deposited nanostructured ZnO films can be used as application in NO₂ sensors