Hydrophobic PTFE@Au@In2O3 Hollow Sphere Films Enabling Ultrasensitive HCHO Detection in Humid Atmospheres

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Abstract
Highly sensitive detection of formaldehyde (HCHO) under high relative humidity (RH) conditions is of great significance for the analysis of human exhaled breath and the monitoring of indoor air pollutants. In this study, a PTFE@Au@In2O3 hollow sphere film sensor for HCHO detection was successfully fabricated via a polystyrene (PS) template-assisted magnetron sputtering technique. Comprehensive material characterizations, including XRD, SEM and XPS, confirmed the formation of the PTFE@Au@In2O3 heterostructure with its unique microstructure. The gas-sensing performance of the sensor was found to be critically dependent on the PTFE sputtering time. At an operating temperature of 325 ℃ and 90% RH, the optimal sensor exhibited a response of 13.6 toward 100 ppm HCHO, along with a limit of detection of 10 ppb (corresponding to a response of 1.6). Notably, at an operating temperature of 325 ℃, this sensor demonstrated superior moisture resistance, retaining 93.3% of its initial response to 1 ppm HCHO when the RH increased from 10% to 90%, whereas the pure In2O3 sensor retained only 47.4%. This work provides a novel and feasible strategy for constructing high-performance HCHO sensors.