Enhanced performance of graphene-based tin oxide hybrid nanostructures for ammonia gas detection

Abstract

Ammonia gas detection has garnered widespread attention in various fields, including food, environmental industries, and medical diagnostics. In this article, we present the synthesis of graphene-based tin oxide (graphene–SnO₂) hybrid nanostructures using the hydrothermal method. Pristine tin oxide nanostructures and a series of graphene-based tin oxide hybrids containing 5 wt.%, 10 wt. %, 15 wt. %, and 20 wt. % graphene concentrations were fabricated to investigate their response as ammonia gas sensors. The X-ray diffraction and high-resolution transmission electron microscopy analysis revealed the tetragonal rutile crystal structure of both pristine SnO₂ and graphene–SnO₂ hybrid structures. The morphology of the synthesized structures was examined using scanning electron microscopy. Fourier transform infrared spectroscopy was employed to validate the functional groups present in the hybrid structures, while the band gap of the graphene–SnO₂ nanohybrid structures was determined using diffuse reflectance spectroscopy. X-ray photoelectron spectroscopy was utilized to investigate the chemical composition, electronic state, and bonding of the materials. Four probe current–voltage (I–V) measurements were conducted to investigate conductivity and ammonia-sensing behavior. Upon exposure to ammonia gas fumes, the pristine SnO₂ exhibited changes in current and resistance, ranging from 0.063 mA to 3.75 mA and 15.87 kΩ to 266.67 Ω, respectively. Similarly, the ammonia sensing behavior of hybrid structures containing 20 wt. % graphene showed changes in current and resistance, ranging from 5.42 mA to 37.8 mA and 0.18 kΩ to 26.45 Ω, respectively. These findings suggest that graphene–SnO₂ hybrid structures exhibit excellent conductivity when exposed to NH₃ gas, unlike their ammonia-absence counterparts.