Oxygen-plasma-assisted formaldehyde adsorption mechanism of SnO2 electrospun fibers

Abstract: Chemisorbed oxygen acts a crucial role in the redox reaction of semiconductor gas sensors, and which is of great significance for improving gas sensing performance. In this study, an oxygen-plasma-assisted technology is presented to enhance the chemisorbed oxygen for improving the formaldehyde sensing performance of SnO2 electropun fiber. An inductively coupled plasma device was used for oxygen plasma treatment of SnO2 electrospun fibers. The surface of SnO2 electrospun fibers was bombarded with high-energy oxygen plasma for facilitating the chemisorption of electronegative oxygen molecules on the SnO2 (110) surface to obtain an oxygen-rich structure. Oxygen-plasma-assisted SnO2 electrospun fibers exhibited excellent formaldehyde sensing performance. The formaldehyde adsorption mechanism of oxygen-rich SnO2 was investigated using density functional theory. After oxygen plasma modification, the adsorption energy and the charge transfer number of formaldehyde to SnO2 were increased significantly. And an unoccupied electronic state appeared in the SnO2 band structure, which could enhance the formaldehyde adsorption ability of SnO2. The gas sensing test revealed that plasma-treated SnO2 electrospun fibers exhibited excellent gas sensing properties to formaldehyde, low operating temperature, high response sensitivity, and considerable cross-selectivity. Thus, plasma modification is a simple and effective method to improve the gas sensing performance of sensors.

A Formaldehyde Indoor Gas Sensor Based on Hierarchical α-Molybdenum Trioxide

The detection of indoor formaldehyde gas is important because of its highly toxic nature. Herein, the two-dimensional α-MoO3 nanosheets and three-dimensional α-MoO3 hierarchical flowers have been prepared by simple hydrothermal strategy and used as the formaldehyde sensing materials. Their microstructures, morphologies and gas sensing characteristics towards formaldehyde were studied. The test results exhibited that, at the optimal temperature of 250 °C, the sensor performances were enhanced due to the assembly of 2D nanosheets into 3D hierarchical structure. The improved properties were contributed to the formation of the hierarchical microstructure constructed by nanosheets. The hierarchical microstructure based gas sensor has significant potential in indoor air sensing application.