Formaldehyde gas sensor with extremely high response employing cobalt-doped SnO 2 ultrafine nanoparticles.

Formaldehyde is a common carcinogen in daily life and harmful to health. The detection of formaldehyde by a metal oxide semiconductor gas sensor is an important research direction. In this work, cobalt-doped SnO 2 nanoparticles (Co-SnO 2 NPs) with typical zero-dimensional structure were synthesized by a simple hydrothermal method. At the optimal temperature, the selectivity and response of 0.5% Co-doped SnO 2 to formaldehyde are excellent (for 30 ppm formaldehyde, R a / R g = 163 437). Furthermore, the actual minimum detectable concentration of 0.5%Co-SnO 2 NPs is as low as 40 ppb, which exceeds the requirements for formaldehyde detection in the World Health Organization (WHO) guidelines. The significant improvement of 0.5%Co-SnO 2 NPs gas performance can be attributed to the following aspects: firstly, cobalt doping effectively improves the resistance of SnO 2 NPs in the air; moreover, doping creates more defects and oxygen vacancies, which is conducive to the adsorption and desorption of gases. In addition, the crystal size of SnO 2 NPs is vastly small and has unique physical and chemical properties of zero-dimensional materials. At the same time, compared with other gases tested, formaldehyde has a strong reducibility, so that it can be selectively detected at a lower temperature.