SnO₂ Nanoparticles Derived from Metal–Organic Precursors as an Acetaldehyde Gas Sensor with ppb-Level Detection Limit

Acetaldehyde gas sensors are highly important for protecting human health. However, it is challenging to achieve rapid acetaldehyde detection at low concentrations and low operating temperatures. In this work, SnO₂ nanoparticles were synthesized by the calcination of amorphous metal–organic precursors prepared by hydrothermal treatment. The effects of different molar ratios of pure terephthalic acid (PTA)/SnCl₂·2H₂O on the microstructures and gas-sensing properties of the synthesized particles were thoroughly investigated. The results showed that the obtained SnO₂ particles were crystalline with sizes between 8 and 20 nm. Although the specific surface area of the SnO₂ particles increased slightly from 57.65 to 65.19 m²/g as the molar ratio of PTA/SnCl₂·2H₂O increased, prominent chemisorbed oxygen species and oxygen vacancies were only present in the SnO₂-3 sample with a molar ratio of 1:1. Meanwhile, the sensor fabricated with SnO₂-3 exhibited a high response value (10.69), an extremely fast response (3 s), and a good recovery (4 s) time when exposed to 40 ppm of acetaldehyde at 100 °C. More interestingly, it also exhibited a low limit of detection of 50 ppb for acetaldehyde gas, as well as good selectivity and long-term stability. A promising sensor for low-temperature and low-concentration acetaldehyde gas detection was developed, and the mechanism behind its sensing performance was thoroughly explored.