Repeatability and sensitivity of quartz crystal microbalance (QCM) sensor array modified with four sensitive materials

With continuous expansion of livestock and poultry breeding industry, the emission of harmful gases has inevitably increased which has also prompted the rapid development of research on harmful gases detection, such as quartz crystal microbalance(QCM)sensors. In this research, a gas-sensing system based on QCM sensor array modified with ethyl cellulose (EC), polyethyleneimine (PEI), tetramethylammonium fluoride tetrahydrate (TMAF), and polypyrrole (PPy) was established to detect three standard harmful gases, namely CO2, NH3, and H2S. It has been observed that the QCM sensors modified with four materials had a good repeatability and a significant response to the three standard harmful gases. Furthermore, the suitable concentrations of the sensitive materials were 20 mg/ml for EC, 10 mg/ml for TMAF, 35 mg/ml for PEI, and 7 mg/ml for PPy. The frequency shift resulted by modified mass of the sensors for the four materials with the best concentrations were 21,343.1 Hz for EC, 21,065.5 Hz for TMAF, 2736.9 Hz for PEI, and 5292.4 Hz for PPy. Additionally, there was a linear relationship between the frequency shift and the concentration of three sample gases in different ranges with a high linear fit coefficient (R2>0.92), except TMAF versus CO2. Moreover, R2 with blank quartz wafer compensation was slightly smaller than which one without compensation. Therefore, the gas-sensing system based on QCM sensor array has an ideal repeatability and recovery response to the three standard gases, and the sensitivity performance was good. This work provides basic information for the research on QCM sensor array in gas detection.