La doped AlPO-5: Enhenced NH3 sensing properties, thermodynamic investigation and humidity-enhanced effect

Highlights: • Solid La doped AlPO-5 is modified on the surface of QCM as mass-type NH₃ sensing material. • The limit of detection reaches ppb level. • The solid La doped AlPO-5 detects NH₃ gas by physical adsorption. • The humidity-enhanced effect in the NH₃ sensing process has been discussed. -- Abstract: Solid AlPO-5 and La doped AlPO-5 (La/AlPO-5) were synthesized by a hydrothermal treatment followed by crystallization and calcination. The ammonia (NH₃) sensing properties of AlPO-5 and La/AlPO-5 were evaluated by using quartz crystal microbalance (QCM) platform to work out the enhanced effect of La doping treatment. La/AlPO-5 possessed a higher response to NH₃ than that of AlPO-5 with same concentration. In addition to the favorable sensitivity, La/AlPO-5 based sensor also showed prominent repeatability and selectivity. We also explored the thermodynamics and humidity-enhanced effect in the NH₃ sensing process.