Synthesis of nanostructured cubic phase SnO2 thin film and its trace-level sensing of CO gas

In this study, we report the fabrication of a cubic phase SnO2-based thin film gas sensor with excellent sensitivity and selectivity for carbon monoxide (CO) gas at room temperature, with a high response of 25606% achieved at 2 ppm CO gas concentration, and a detection limit down to 1 ppb. Cubic phase SnO2 thin films are synthesized using a simple sol-gel process, followed by spin coating. Our synthesis technique allows for stabilizing the cubic phase of SnO2, confirmed through XRD and TEM studies, which is otherwise reported at high pressures and temperatures. Further, our DFT simulations show that the cubic phase of SnO2 nanoparticles has a lower energy barrier for CO adsorption and desorption than the more common tetragonal phase. The low-voltage and ambient operating conditions of the sensor reported in this study make it highly practical for widespread use, thus offering a promising solution to the growing need for efficient and affordable gas sensing applications, including environmental monitoring, industrial safety, and medical diagnosis. This study presents a cubic phase SnO2 thin film gas sensor with ultra-high CO sensitivity and 1 ppb detection limit, enabled by sol-gel synthesis and DFT insights, offering practical low-voltage sensing for diverse applications.