High performance formaldehyde detection based on a novel copper (II) complex functionalized QCM gas sensor

In order to construct highly sensitive and stable QCM gas sensor, we present an innovative strategy. Firstly, we employ a physical vapor deposition (PVD) method to coat a thin layer of copper on the surface of QCM silver electrode. Then, a novel metal complex as sensing material, [Cu(DDS)2(Cl)2(MeOH)2], is grown in-situ on the copper layer to ensure a strong coupling between metal complex sensing materials and QCM electrode. The sensing material is characterized through following instruments: elemental analysis, single crystal XRD, SEM, PXRD, IR spectra and TGA. The sensing test results indicate that the QCM sensor exhibit high sensitivity and selectivity toward gaseous formaldehyde because of a reversible interaction between amino group and HCHO molecule. The detection limit reaches down to 50 ppb. This implies the facile-fabricated sensor has a great potential in the area of rapid, stable, sensitive, and selective formaldehyde on-site detection. Based on the temperature-varying micro-gravimetric experiment, enthalpy change is quantitatively obtained, which indicates that the interaction between the complex and HCHO molecules belongs to chemical adsorption. The values of ΔH calculated by Gaussian 09 indicate that chemical adsorption between NH2 group and aldehyde group play a leading role in detecting selectively formaldehyde gas.