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Although semiconducting metal oxide (SMOx) nanoparticles (NPs) have attracted attention as sensing materials, the methodologies available to synthesize them with desirable properties are quite limited and/or often require relatively high energy consumption. Thus, we report herein the processing of Zn-doped SnO2 NPs via a microwave-assisted nonaqueous route at a relatively low temperature (160 °C) and with a short treatment time (20 min). In addition, the effects of adding Zn in the structural, electronic, and gas-sensing properties of SnO2 NPs were investigated. X-ray diffraction and high-resolution transmission electron microscopy analyses revealed the single-phase of rutile SnO2, with an average crystal size of 7 nm. X-ray absorption near edge spectroscopy measurements revealed the homogenous incorporation of Zn ions into the SnO2 network. Gas sensing tests showed that Zn-doped SnO2 NPs were highly sensitive to sub-ppm levels of NO2 gas at 150 °C, with good recovery and stability even under ambient moisture. We observed an increase in the response of the Zn-doped sample of up to 100 times compared to the pristine one. This enhancement in the gas-sensing performance was linked to the Zn ions that provided more surface oxygen defects acting as active sites for the NO2 adsorption on the sensing material.

We report herein the efficiency of microwave-assisted synthesis for obtaining ZnO/SnO2 heterostructures for room-temperature gas-sensing applications. The sensing performances of the traditional oxide materials have been found for applications above 200 °C. However, these temperatures were here reduced to room temperature by considering sensing activity photoactivated by UV light, even for ppb ozone (O3) levels. The heterojunctions exhibited a fast response, total reversibility, and selectivity to oxidizing gases, especially O3 gas. This investigation provides an efficient way to obtain heterostructures exhibiting remarkable properties for practical applications as O3 gas sensor devices.