Unveiling superior NH₃ sensing performance: ultrafast response and enhanced recovery kinetics in Ti₃C₂T_<i>x</i>/ZnO nano-hybrid sensors with UV-induced Schottky junctions

Achieving high sensitivity and rapid response/recovery times at ambient temperatures remains a significant challenge in gas sensing. Ti₃C₂T_<i>x</i> MXenes have gained attention for their gas-sensing potential due to their high conductivity and active surface functional groups, but challenges such as limited sensitivity and slow response/recovery persist. In this study, we present an ultrafast, reversible Ti₃C₂T_<i>x</i>/ZnO hybrid composite sensor for NH₃ detection at room temperature. We evaluated the sensor's performance under both ambient and UV illumination conditions. Under ambient conditions, the Ti₃C₂T_<i>x</i>/ZnO sensor exhibited a 50-fold enhancement in sensitivity compared to pristine ZnO, with response and recovery times of 49 s and 39 s, respectively, at 10 ppm NH₃. Under UV illumination, the optimized Ti₃C₂T_<i>x</i>/ZnO configuration achieved a sensor response of 88 at 50 ppm NH₃, with ultrafast response and recovery times of 10 s and 13 s, respectively, at 10 ppm NH₃, and a limit of detection (LOD) of 0.1 ppm. These improvements are attributed to charge perturbation at the sensor surface facilitated by Ti₃C₂T_<i>x</i>/ZnO interactions and the formation of a Schottky barrier at their interface, accelerating adsorption-desorption kinetics. The sensor also demonstrated excellent selectivity for NH₃ and high long-term stability and repeatability, making it highly suitable for environmental monitoring, industrial safety, and medical diagnostics.