Boosting 2D Black Phosphorus Ambient Stability: Noncovalent Functionalization Using Viologen Molecules

Black phosphorus nanosheets (BPNSs) have recently emerged as a valuable addition to the diverse family of 2D materials, holding promises for a wide range of applications. However, their practical use is limited by poor stability under ambient conditions, as they degrade quickly when exposed to light, air, or moisture. Noncovalent functionalization offers a promising approach to address these challenges. Herein, viologen derivatives are incorporated into a BPNS suspension in acetonitrile, resulting in the formation of two hybrid materials. These hybrids are subsequently stored under ambient conditions to track their degradation over time. The degradation behavior of these functionalized BPNSs is analyzed and compared to that of pristine BPNSs stored in both nitrogen and ambient environments, using X-ray photoelectron spectroscopy. Interestingly, the two viologen-based hybrid systems exhibited varying degrees of ambient protection efficiency, attributed to differences in their average adsorption energies and aggregation kinetics with BPNSs. Methyl viologen-functionalized BPNSs showed markedly reduced degradation in ambient conditions, with less pronounced differences for samples stored in a protected environment. This study introduces a promising strategy for enhancing the stability of BPNSs, making them more resistant to decomposition and potentially suitable for energy storage applications and optoelectronic devices.