Li-substituted ZnO nanoparticles exhibiting room temperature optical gas sensing for NO2 with swift response and recovery

Abstract

This paper reports the results of NO₂ gas sensing performance through photoluminescence method. The pure and Li substituted (0.1%, 0.2%, and 0.3% w/w) zinc oxide nanoparticles were synthesized via simple aqueous solution growth technique.The structural, morphological and optical properties of the samples were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV–Vis spectroscopy, and photoluminescence (PL) spectroscopy. PL spectral studies indicated that the synthesized ZnO nanoparticles possess more vacancies or lattice defects compared to the well explored ZnO nanoparticles prepared using various other synthesis techniques. The presented work focuses on optical gas sensing at room temperature under normal atmospheric pressure to detect the presence of nitrogen dioxide. The optical NO₂ gas sensing studies revealed the substantial role of Li doping on the sensing properties of the synthesized samples, with gas concentrations ranging from 500 ppb to 30 ppm. Remarkably, 0.3% w/w Li-doped ZnO nanoparticles demonstrated an 70.25% response to 30 ppm NO₂ gas, with a quick response time (τ) of 16 s and a recovery time of approximately 21 s at room temperature and normal atmospheric pressure. The short response, recovery time, high sensing response, low detection limit and stability exhibited by 0.3% Li-ZnO nanoparticles make them promising candidate fordesigning efficient and reliable optical sensors for NO₂ gas.

Graphical abstract