Sol-gel derived Ni-doped SnO2 nanoparticles enabling room-temperature NO2 detection

For metal oxide semiconductor (MOS) gas sensors, achieving rapid and highly sensitive responses at room temperature (RT) remains a significant challenge. In this study, Ni-doped SnO 2 nanoparticles (NPs) were synthesized via a sol-gel method. The incorporation of nickel ions substantially enhanced the RT NO 2 sensing performance of SnO 2 . At an optimal doping concentration (5 at%), the SnO 2 NPs exhibited high sensitivity, excellent selectivity, and good stability, with a nearly 120-fold enhancement in sensor response. The excellent sensor performance can be attributed to the fact that when Ni 2 + enters the SnO 2 lattice and replaces Sn 4+ , it disrupts the defect balance in the SnO 2 lattice. The presence of Ni 2+ in the SnO 2 crystal captures free electrons in the sensitive material, forming oxygen ions and oxygen vacancies, which alters the defect balance of the gas-sensitive element and promotes the adsorption of NO 2 on the SnO 2 surface. This doping strategy effectively lowered the operating temperature of SnO 2 , enabling reliable NO 2 detection under RT conditions. Additionally, the experimental detection limit of the sensor reached as low as 100 ppb, far below the threshold of 200 ppb recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). This work provides an effective sensitization strategy for developing RT gas sensors.