β-Ga2O3 Nanostructure-Based Chemiresistive Sensor for Selective Detection of Formaldehyde

Gallium oxide (Ga2O3) is a promising material for sensing applications due to its ultrawide band gap and distinctive physical and chemical properties. This study proposes synthesizing Ga2O3 nanostructures by the sol–gel technique, using them as sensing materials for volatile organic compounds (VOCs) such as formaldehyde (HCHO), ethanol, acetone, 2-propanol, and toluene and investigating the kinetic parameters using the Eley–Rideal model. Ga2O3 nanostructures with desirable morphologies were obtained by controlling the synthesis parameters such as solution temperature and precursors. Compared to other nanostructures, such as nanoparticles, cocoon-like structures, nanoplates, and high aspect ratios of nanorods, a sensor based on β-Ga2O3 nanorods, with an average diameter of 60 nm, showed outstanding selectivity and sensitivity toward HCHO even in the presence of other VOCs. The response for formaldehyde at 300 °C at a concentration of 300 ppm was found to be 30.25%. The Eley–Rideal model considers the direct interaction of gas molecules adsorbed on the β-Ga2O3 sensor surface having various types of preadsorbed oxygen acceptor species. By fitting experimental data to theoretical response transient curves, key kinetic parameters such as sensitivity, gas-phase mass transfer coefficient, reaction rates, and activation energy were determined.