Self-assembled photo-responsive black phosphorus-azobenzene composite Langmuir films with chemical gas sensor and photoelectric conversion applications

The reasonable design of various functionalized nanocomposites based on black phosphorus (BP) has sparked substantial attention from researchers. In this work, the bulk BP was successfully exfoliated into nanosheets (BPNS), the polyethyleneimine (PEI) was selected as the surface protective layer to modify the BPNS for strengthening its stability. We have designed and synthesized two kinds of BPNS-PEI Langmuir composite films containing azobenzene compounds (BPNS-PEI/N-Azo and BPNS-PEI/PAA-Azo) by Langmuir-Blodgett (LB) technology. The composite films were successfully assembled and analyzed the nanoscale structure and morphology using transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning electron microscopy (SEM) and other different characterization methods. In addition, the BPNS-PEI/N-Azo composite films were proven to demonstrate the photoisomerization stability and the acidalkali atmosphere gas responsiveness by ultraviolet-visible spectroscopy and Fourier transform infrared spectroscopy. Furthermore, the photoelectrochemistry performances of the acquired LB composite films were studied by transferring multilayer films on indium tin oxide (ITO) substrates. And the results demonstrated that the BPNS-PEI/N-Azo self-assembled LB film electrode showed higher photoelectric conversion efficiency. The self-assembled films based on BP, undertaking an appealing conception for gaining a wide range of nano-optical devices, gas sensors and optoelectronic devices.