SnO₂ Nanowire Sensors for Sensitive and Reliable Ozone Detection

The manipulation of atoms and molecules, commonly referred to as nanotechnology, is today one of the main tools for developing smaller, faster, and cheaper devices.Among them are sensors based on nanomaterials-especially semiconductor nanowires-which have gained prominence in recent years due to their high sensitivity, selectivity, and rapid response in gas detection.The effectiveness of these nanowires in sensors is related to the variation in the material's conductivity according to the surface charge state, which is strongly influenced by adsorbed chemical species.This allows their use both as an active element and to improve the efficiency of existing sensors [1][2][3][4].In this context, ozone (O3) stands out as one of the gases of greatest interest for detection, as it is a strong oxidizing agent used for sterilizing hospital rooms and disinfecting restricted areas due to the COVID-19 pandemic, but it is also harmful in large quantities in the environment.According to international resolutions (2002/3/EG) [5], the maximum permitted concentration of this gas in the environment is 240 g/m 3 (~ 120 ppb) and in the workplace it should not exceed 200 g/m 3 (~ 100 ppb).Based on this scenario, the development of devices that can monitor low ozone concentrations (ppb) at room temperature is of fundamental importance.Therefore, this work encompasses the production, characterization, and optimization of electronic devices based on a network of SnO2 nanowires with the aim of studying the gas (ozone) transport and detection properties at room temperature of these materials.SnO2 nanowires were produced in a controlled manner using a chemical vapor deposition (CVD)-based growth process and integrated into metal-semiconductor-metal devices.Transport experiments were conducted to analyze the conduction mechanisms and their alterations that lead to ozone detection, exploring the influence of the presence of vacancies and the properties of the metal-semiconductor interfaces that define the electrical contacts.Regarding sensing, the detection mechanism in gas sensors based on these structures can be understood by adsorption and desorption processes between chemical species and the surface of the SnO2 nanowires.Based on the results, thermal activation (high temperatures) and variable-range hopping (low temperatures) mechanisms were observed in relation to the transport mechanisms [6][7][8].The results regarding ozone detection showed that the sensor demonstrated high detection sensitivity, with a fast response time ( < 4 min) to ozone exposure at room temperature.Detection performance was analyzed under exposure to different ozone concentrations (0.4 to 1.2 ppm), both in the dark and under ultraviolet (UV) illumination.Irradiation of the devices with ultraviolet light proved highly effective in "cleaning" the sensors after each ozone exposure cycle, contributing to optimized device performance.Compared with literature data [9-12], the devices developed in this work showed excellent performance at room temperature, with significant responses and high reproducibility for ozone concentrations in the hundreds of ppb range.The experiments showed promising and reliable results for ozone detection using tin oxide (SnO2) devices.In summary, the experiments indicated promising and consistent behavior in ozone detection using tin oxide (SnO2) devices.