Ultrafast electron transfer at the zero-dimensional/two-dimensional nanosheet interface for highly selective ammonia sensing

Metal oxides exhibit remarkable gas sensing effect and adjustable physicochemical properties, making them widely utilized in chemiresistive gas sensors. The aggregation of metal oxide nanostructures, however, results in a reduction of specific surface area and porosity, thereby affecting the gas sensing properties. The primary challenge involves effectively addressing the deficiencies in surface adsorption and electron transfer capabilities. In this study, we developed a solvothermal template approach for the synthesis of zero-dimensional/two-dimensional nanosheets, enabling highly sensitive detection of ammonia at low operating temperatures. The findings illustrate that the synergistic interaction between Fe₃O₄ nanoparticles and Ti₃C₂T_x MXene nanosheets establishes an interface characterized by chemical and electronic coupling, facilitating an additional pathway for charge transfer. Simultaneously, the adsorption and sensing of ammonia molecules on Fe₃O₄/Ti₃C₂T_x MXene are thermodynamically and kinetically more favorable compared to Fe₃O₄ alone. The Fe₃O₄/Ti₃C₂T_x MXene sensor exhibits excellent sensing performance for ammonia, with high sensitivity (Ra/Rg = 5.3 at 500 ppb, where Ra represents the sensor resistance in air and Rg represents the sensor resistance in the target gas) and ultra-fast response time, while maintaining high selectivity and long-term stability. This work proposes an innovative approach for the integration of nanoparticles and MXenes, which holds great potential for advancing the development of high-performance gas sensors.