Facile and environmentally friendly fabrication of few-layer bismuthene by electrochemical exfoliation method for ultrafast photonic applications

Bismuthene, an unique kind of two-dimensional material beyond graphene, has attracted considerable attention recently for its unique electronic and photonic properties. These unique properties render of Bismuthene as an excellent candidate for various applications, e.g., nonlinear optical limiters, optical switchers, and optical photonic devices. Toward this goal, we report herein an easy and quick alternative method to exfoliate a semi-metal Bi crystal to obtain few layer nanosheets in two different sizes based on electrochemical exfoliation approaches. At the different wavelengths and intensity, the resulting nonlinear optical activity is studied. The nonlinear absorption coefficient was calculated using Z-scan measurements. The exfoliated materials have been well characterized using various techniques, e.g., UV-Vis-NIR absorption, photoluminescence (PL), X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman spectroscopy, transmission electron microscopy (TEM), and, XPS. The influence of different experimental conditions, such as the voltage on linear/nonlinear optical properties has been well examined. In addition, the mechanism of electrochemical cathodic exfoliation under different applied voltage in aqueous solution is described. This finding suggests that the bismuthene-based reverse saturable absorber RSA is a promising new material for broadband ultrafast optical limiters that protect against Vis-IR ultrashort pulse laser damage.