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

Gallium oxide (Ga 2 O 3 ) is a promising material for sensing applications due to its ultrawide band gap and distinctive physical and chemical properties. This study proposes synthesizing Ga 2 O 3 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. Ga 2 O 3 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-Ga 2 O 3 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-Ga 2 O 3 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.