A novel low-concentration isopropanol gas sensor based on Fe-doped ZnO nanoneedles and its gas sensing mechanism

The detection of lung cancer via the analysis of volatile organic compounds (VOCs) in exhaled breath has attracted a lot of attention as it is simple and non-invasive for the patients. Among the numerous VOCs exist in the breath, isopropanol is believed to be an important biomarker that can help to discriminate between healthy and unhealthy people. In this work, a highly sensitive Fe-doped ZnO nanoneedles-based gas sensor was studied for the detection of isopropanol at low concentrations (below 10 ppm). The pure and Fe-doped ZnO were synthesized via a hydrothermal method and spray-coated onto an alumina substrates equipped with a pair of gold interdigitated electrodes. The morphologies of the sensing layers were characterized by SEM, while the phase structure and composition were determined by XRD. The sensing properties of pure and Fe-doped ZnO were investigated under different temperatures and concentrations. It is found that Fe doping significantly increased the sensing performance of ZnO nanoneedles. The optimal doping concentration of Fe is 5 at% for isopropanol detection, and the optimal working temperature is 275 °C. The sensor showed a high response to 250 ppb isopropanol, together with high stability under different humidity levels.