Detection of NH3 by quartz crystal microbalance with SnxNiy coating

In this paper, the gas-sensing properties of bimetallic structures of Sn and Ni to NH3 are investigated using Quartz Crystal Microbalance (QCM). The 16 MHz QCM are created on AT-cut quartz with gold electrodes (4mm diameter). The bimetallic layers are prepared by cathode electro-deposition on QCM. Special electro-chemical cells are constructed to investigate the electro deposition process. Nickel is used as anode and the optimal current density is 3 A/dm(2). After electro deposition the coatings are treated at 200 degrees C for one hour in air environment. The coatings are investigated by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) methods. SEM micrographs of the coatings show that they consist of a highly branching layer of bimetallic needles. The structure investigation of coatings indicate dendrite ones consisting of different SnxNiy crystalline phases and Sn. The sorption properties of SnxNiy coatings to NH3 are studied in dynamic regime. The frequency-time characteristics (FTCs) of the system QCM-SnxNiy are measured. The changes of the frequency from 5Hz to 77Hz are defined for 10ppm and 1000ppm respectively. The maximum frequency shift and mass-loading are determineded. It is obtained that SnxNiy coatings possess sorption ability to NH3 and can be successful used as sensor element for NH3.