Facile and Green Fabrication of Tin Aminoclay Nanoparticles with Embedded p–n Heterojunctions for High-Performance Ammonia Sensors Operating at Room Temperature

Tin dioxide (SnO₂)-based sensors have been widely used to monitor various gases in the environment. However, they suffer from several inherent drawbacks, such as high operating temperatures, low sensitivity and selectivity, and unreliable performance under high-humidity conditions, significantly limiting their practical applications. Additionally, current technologies for designing and fabricating SnO₂-based gas sensors typically involve organic solvents and additional steps for dispersion and deposition, leading to increased energy and time consumption, as well as concerns over solvent waste. To address these challenges, we present a simple one-step thermal annealing approach to develop a tin aminoclay (SnAC) nanoparticle-based chemical sensor with high performance for detecting NH₃ gas at room temperature. Through structural investigations and characterizations, p–n SnO/SnO₂ heterojunctions within the SnAC nanoparticles were achieved and optimized by varying annealing temperatures from 200 to 400 °C. The SnAC nanoparticles annealed at 350 °C demonstrated the highest sensing performance for NH₃ gas, attributed to the synergistic effects of morphological, structural, and electrical properties of the p–n SnO/SnO₂ heterojunction. The sensor exhibits high sensitivity (∼37.3%/ppm), selectivity, and good long-term stability at room temperature and under various relative humidity conditions. This study provides a facile, environmentally friendly, and cost-effective approach for developing and designing commercial tin oxide-based gas sensors that overcome many existing limitations.