Wireless Hand-Held Device Based on Polylactic Acid-Protected, Highly Stable, CTAB-Functionalized Phosphorene for CO₂ Gas Sensing

Phosphorene is a novel two-dimensional (2D) material with exceptional properties and is connecting the gaps between graphene and transition-metal chalcogenides but having environmental instability. In this study, we present effective liquid exfoliation of few-layer phosphorene (FLP) from bulk black phosphorous (BP) in the presence of cetyltrimethylammonium bromide (CTAB), a cationic surfactant that is highly stable. It successfully stabilizes FLP in deionized water, which is consistent with obtained characterization and gas-sensing studies. Our investigation shows that the dynamic sensing response of the CTAB-grafted phosphorene (P-CTAB) sensor increases by ∼1.5 times as the relative humidity (RH) varies from 33 to 75%, which is the first published result for CO2 gas detection. The sensitivity values of the P-CTAB and P-CTAB/polylactic acid (PLA) are found to be 0.0356 and 0.0329 ppm–1, respectively, toward CO2 gas. It is notable that when a polylactic acid (PLA) membrane is introduced as a barrier layer in our fabricated Arduino-based Bluetooth-enabled hand-held device, it obstructs the environmental effect with a trace-level detection capability and negligible change over time (up to 30 days). Herein, for the first time, we discover the gas-sensing characteristics of CTAB-grafted phosphorene and witness an ultrasensitive and selective response toward CO2 gas detection.