Nanoscopic hygrometry: Exploiting porous nature zinc-doped tin oxide nanoparticles for enhanced humidity sensing at ambient temperature

Abstract

This study focuses on zinc-doped tin oxide nanoparticles (Zn-SnO2 NPs) as promising humidity sensors. Through a chemical coprecipitation method, we synthesized Zn-SnO2 NPs and explored the influence of calcination temperature on their properties. X-ray diffraction confirmed the tetragonal rutile structure, and morphological analysis revealed a cauliflower-like morphology with enhanced porosity after calcination. UV-Visible absorption spectroscopy and photoluminescence measurements demonstrated a blue shift in the absorption peak and significant emission peaks related to oxygen vacancies, indicating improved humidity sensing potential as increasing the calcination temperature. The controlled calcination process led to successful outcomes, precisely tuning the NPs structure and optical behavior for enhanced humidity sensing capabilities. Conductivity studies have highlighted the semiconducting behavior of the NPs and observed that an increase in calcination temperature reduces their conductivity. Notably, humidity sensing experiments revealed a remarkable response of 93% and an exceptional response time of 30 seconds for the calcined NPs, surpassing the uncalcined sample. The sensing mechanism involving physisorption, chemisorption, and capillary condensation of water molecules on the NPs surface was validated. Moreover, the stability test over two month demonstrated consistent and highly stable humidity sensing response, reaffirming the NPs potential as effective and reliable humidity sensors.