Multishell SnO2 Hollow Microspheres Loaded with Bimetal PdPt Nanoparticles for Ultrasensitive and Rapid Formaldehyde MEMSSensors

Low-cost and real-time formaldehyde (HCHO) monitoring is of greatimportance due to its volatility, extreme toxicity, and ready accessibility. In this work, alow-cost and integrated microelectromechanical system (MEMS) HCHO sensor isdeveloped based on SnO2multishell hollow microspheres loaded with a bimetallicPdPt (PdPt/SnO2-M) sensitizer. The MEMS sensor exhibits a high sensitivity toHCHO ((Ra/Rg-1) % = 83.7 @ 1 ppm), ultralow detection limit of 50 ppb, andultrashort response/recovery time (5.0/7.0 s @ 1 ppm). These excellent HCHOsensing properties are attributed to its unique multishell hollow structure with a largeand accessible surface, abundant interfaces, suitable mesoporous structure, andsynergistic catalytic effects of bimetal PdPt. The well-defined multishell hollowstructure also shows fascinating capacities as good hosts for noble metal loading.Therefore, PdPt bimetallic nanoparticles can be employed to construct a synergisticsensitizer with a high content and good dispersity on this multishell hollow structure,further exhibiting a reduced working temperature and ultrasensitive detection of HCHO. This PdPt/SnO2-M-based MEMS sensorpresents a unique and highly sensitive means to detect HCHO, establishing its great promise for potential application in environmental monitoring