Functionalization of black phosphorus nanosheets via self-polymerization of dopamine and subsequent secondary reactions for gas sensing investigation

Abstract

Black phosphorus nanosheet (BPNS) is considered as a promising gas sensing material due to its unique puckered layer structure and excellent physical/chemical properties. However, previously reported BPNS based gas sensors mostly suffered from low selectivity and/or poor stability. Herein, we propose to modify BPNS through surface chemistry and regulate its gas sensing properties based on surface terminations/decorated nanoparticles. A two-step functionalization was utilized including self-polymerization of dopamine, and secondary reactions to anchor self-assembly monolayers or metal catalysts via the polydopamine (PDA) medium. The modified PDA layer could offer hydrogen bonding interactions with gas analytes, which leads to a 9-fold increase in NO2 sensitivity compared with bare BPNS (4000% for PDA@BPNS versus 426% for bare BPNS at 1 ppm). Further surface functionalization through secondary reactions yields a variety of modified PDA@BPNS composites with extended sensing properties (e.g., better stability and selectivity). We finally fabricated a sensor array system containing these modified PDA@BPNS composites and successfully identified a variety of gas molecules with good separation efficiency.