Room Temperature Humidity Tolerant Xylene Sensor Using a Sn-SnO2 Nanocomposite

Abstract

Xylene is one of the representative indoor pollutants, even in ppb levels, that affect human health directly. Due to the non-polar and less reactive nature of xylene, its room temperature detection is challenging. This work demonstrates a metallic tin-doped Sn-SnO2 nanocomposite under controlled pH conditions via a simple solvothermal route. The Sn nanoparticles are uniformly distributed inside the SnO2 nanospheres of ∼70 nm with a high specific surface area of 118.8 m2/g. The surface of the Sn-SnO2 nanocomposite exhibits strong affinity toward benzene, toluene, ethylbenzene, and xylene (BTEX) compared to other polar volatile organic compounds (VOCs) such as ethanol, acetone, isopropyl alcohol, formaldehyde, and chloroform tested in this study. The sensor's response is highest for xylene among BTEX molecules. Under ambient room temperature conditions, the sensor exhibits a linear response to xylene in the 1-100 ppm range with a sensitivity of ∼255% at 60 ppm within ∼1.5 s and recovers in ∼40 s. The sensor is hardly affected by humidity variations (40-70%), leading to enhanced reliability and repeatability under dynamic environmental conditions. The meso and microporous nanosphere morphology act as a nanocontainer for non-polar VOCs to diffuse inside the nanostructures, providing easy accessibility. The metallic Sn increases the affinity for less reactive xylene at room temperature. Thus, the nanocatalytic Sn-SnO2 nanocomposite is an active gas/VOC sensing material and provides an effective solution for sensing major indoor pollutants under humid conditions.