Study on a micro-gas sensor with SnO2–NiO sensitive film for indoor formaldehyde detection

A micro-gas sensor is fabricated based on a micro-hotplate (MHP) with micromachining technology. The SnO2–NiO nanometer polycrystalline composite synthesized by a chemical co-precipitation method is coated onto a micro-hotplate as a sensitive film. The response and recovery time of the micro-gas sensor decrease rapidly with increasing the formaldehyde (HCHO) concentration at relatively low concentrations. The micro-gas sensor shows good stability, low power consumption of 180 mW at the MHP operation temperature of 300 °C, and high selectivity in the presence of interference gases such as alcohol, toluene, α-pinene and acetone. The micro-gas sensor can detect 0.06 ppm HCHO, which is the indoor exposure limit for HCHO referring to Chinese environmental protection agency (EPA).