Ultra-dense SnO2 QDs-decorated MXene nanosheets with high water dispersibility for rapid NH3 sensing at room temperature

The demand for sensitive and rapidly detecting gas sensors is increasing across various industries, ranging from environmental monitoring to medical diagnostics. Various harmful gases pose significant health risks, necessitating detection below permissible exposure limits where metal oxide semiconductor (MOS) gas sensors have garnered attention due to their sensitivity, rapid response, and cost-effectiveness. However, their high operating temperatures and limited portability have presented challenges. In this study, a novel gas sensing approach utilizing a hybrid material consisting of SnO2 quantum dot (QD) nanoparticles integrated with Ti3C2Tx MXene sheets has been developed. Originating from the abundance of nucleation sites on MXene for particle deposition, SnO2 QD nanoparticles of 2-3 nm size were densely decorated. In contrast with previous approaches, SnO2-Ti3C2Tx hybrids were in a water-dispersible form, allowing excellent solution processability. The resulting hybrid, water-dispersible SnO2-Ti3C2Tx MXene (WSM), exhibited remarkable improvements in gas response and response time at room temperature. Particularly, WSM demonstrated exceptional selectivity for ammonia gas, with a more than hundredfold increase in response compared to pristine MXene. Furthermore, the excellent dispersibility of WSM in water was also utilized to fabricate MXene-based sensors entirely through solution processes, demonstrating comparable performance to traditionally created WSM sensors.