Selectivity of a QCM gas sensor modified by ZnSn(OH)6via analysis of adsorption thermodynamics and kinetics

Abstract

In this paper, a novel analysis approach was employed to achieve the selectivity of a quartz crystal microbalance (QCM) sensor. A QCM sensor chip modified by ZnSn(OH)₆ (ZSH) was used to identify gases (CO, CH₄ and O₂) with different volume fractions. The combination of adsorption thermodynamics and adsorption kinetics was firstly used to identify gas species. The relationship between the adsorption thermodynamic parameter (adsorbed mass amount in molar) and the adsorption dynamic parameter (adsorption rate constant, k) was used to characterize the selectivity and concentration of gases. It showed that the method is useful but it still has some limitations. Another approach was also proposed. The kinetic parameter t₉₀ and thermodynamic parameter Δm were employed as characteristic parameters to determine the species and concentration of a gas. The results showed that three kinds of gas with different volume fractions were located in different regions of the t₉₀-Δm two-dimensional graph. We can identify single gases with different volume fractions by enriching the t₉₀-Δm graph with additional data. It is believed that this new analysis method would be promising in gas species identification with QCM sensors.