Facile synthesis of nano-casted mesoporous WO3 derived from KIT-5 for fabrication of highly sensitive NH3 gas and humidity sensor

Ordered mesoporous tungsten trioxide (WO3) was synthesized through the nano-casting method, utilizing 3-D cubic KIT-5 as a rigid template. The synthesized materials underwent thorough characterization employing a range of material analysis techniques. Subsequently, their gas sensing capabilities towards different gases were assessed. The obtained ordered mesoporous structure materials demonstrated exceptional pore arrangement, with an average pore size of approximately 7-9 nm and exceptional surface area of 534.4m2g(-1) by BET analysis. Further, mesoporous WO3's characteristics as a humidity sensor were investigated at ambient room temperature (27 degrees C) in relative humidity (RH%) range from 11 to 98%. The response/recovery time of mesoporous WO3 as a humidity sensor comes out to be 5 s/8 s respectively with minimal hysteresis (1.2%), and high sensitivity of 95.9K ohm/RH%. Additionally, the NH3 sensing capabilities of the sensors based on nano-casted mesoporous WO3 were evaluated using a dynamic gas sensing test system. The sensor employing nano-casted mesoporous WO3 exhibited significantly higher response, shorter response and recovery times, and exceptional selectivity towards NH3. The mesoporous structure facilitated the creation of organized channels, facilitating easy diffusion of gas molecules, while the high surface area provided extensive active sites essential for improving gas sensor performance. The sensor based on mesoporous tungsten dioxide presented high gas response (R-a/R-g) of 94.06 towards NH3 at an optimising temperature of 150 degrees C, it showcased an excellent response-recovery of 31 s/6 s, excellent repeatability and selectivity over other gases present in the environment.