Controlled Synthesis of Tungsten Oxide Nanomaterials with Different Morphologies and Their Gas-Sensing Properties for Formaldehyde in Vegetables

Formaldehyde is illegally applied to vegetables by vendors as a preservative to extend their shelf life, and it poses health risks to consumers. Herein, a series of WO₃ with different morphologies were synthesized and employed as the sensing material in gas sensors to detect formaldehyde in vegetables rapidly. Among all the samples, the WO₃ nanoplate sensor exhibited the best sensitivity (16.5@200 ppm), a rapid response/recovery time (10/12 s), superior selectivity, and a low limit of detection (500 ppb). This was mainly attributed to its abundant mesopores and large specific surface area, which enhanced the formaldehyde adsorption capacity and adsorption/desorption rates while providing more active sites, thereby improving the sensor's response speed and resistance variation range. The WO₃ nanoplate sensor also achieved reliable formaldehyde detection in actual vegetable samples (baby cabbage). This study provides systematic guidance for optimizing the gas-sensing performance of functional materials. It establishes a foundation for developing rapid, non-destructive formaldehyde detection technologies applicable for vegetable quality control.