Improved selectivity of borophene sensor towards NO2 gas with PEI-ZIF-8 overlayer

Stable and selective gas sensing is essential to detect toxic gases and avoid gas leak accidents. Two-dimensional (2D) materials are potential sensing materials for making gas sensors because of their high surface-to-volume ratios, broad surface activity, and defect sites. In this work, a recent 2D material, borophene, is used as the NO2 gas-sensing material. Polyetherimide (PEI) incorporated with the Zeolitic imidazole framework (ZIF-8) with different loading (mixed matrix membrane, MMM) is used as a selective gas separation membrane for its solubility (imide, isopropylidene and ether groups on PEI) and diffusion (porosity) properties. The MMM was selective to NO2 gas as ZIF-8 is selective towards NO2 gas, and PEI is resistant to substances like hydrocarbons, alcohols, and halogenated solvents. A slight variation in borophene's gas sensing response (0.6%) was observed for 25 ppm NO2 at 25 °C and 35% relative humidity (RH) with and without the PEI-ZIF-8 filter, showing the MMM filter is not affecting the sensing response highly. As ZIF-8 is hydrophobic, the borophene sensor showed higher stability at higher RH conditions. These findings suggest that fabricated sensors can detect NO2 gas at varying concentrations for environmental and human safety.