Zn2SnO4/SnO2 heterojunctions regulated by the mineralizer sodium hydroxide promotes highly sensitive detection of formaldehyde vapor at room temperature

Achieving highly selective, highly responsive detection of formaldehyde gas at ppb level at room temperature is highly challenging for air monitoring and life health observation. Therefore, in this paper, low-cost, easy-to-fabricate, highly responsive as well as highly selective Zn2SnO4/SnO2 (ZTO/SnO2) metal-oxide semiconductor gas sensors have been successfully prepared by using one-pot hydrothermal method. The results showed that the synergistic effect of the n-n heterojunction formed between ZTO/SnO2 prepared by this method led to a substantial increase in the sensitivity to the target gases, and ZTO/SnO2-3 a higher response (291) to 100 ppm formaldehyde compared to the response values of pure samples of Zn2SnO4 (20.4) and pure SnO2 (6.99) at room temperature. In addition, the response value for formaldehyde reached about 16.5 to 295 times higher than that for other common hazardous gases (100 ppm) in our lives. The ZTO/SnO2-3 sample with 1 mol/L NaOH was homogeneous and small, exposing as much surface as possible, and the theoretical minimum detection limit was calculated to be 50 ppb. Therefore, the large specific surface area and active adsorption/interaction sites are favorable for gas sensing. This work provides an excellent way to prepare gas-sensitive characteristic sensors using NaOH to improve the surface structure.