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.