Two-dimensional non-layered selenium nanoflakes: facile fabrications and applications for self-powered photo-detector.

Two-dimensional (2D) materials exhibit many interesting properties, but most 2D materials are exfoliated from layered bulk materials, limiting the development of the 2D material group. Recently, non-layered 2D materials have aroused great attention due to their excellent catalysis performance, favored compatibility with silicon substrates and high chemical activity. With high photoconductivity, high responsivity and fast response time, non-layered selenium (Se) exhibits important applications in the field of optoelectronics. In this work, we use a simple liquid phase exfoliation method to fabricate 2D Se nanoflakes from bulk Se which possesses a unique chain structure. The thickness of 2D Se nanoflakes was measured to be in the range of 5-10 nm. As-fabricated Se nanoflakes were used in a photodetector by the photoelectrochemical method, showing a high photocurrent density (1.28 μA cm-2) and photoresponsivity (10.45 μA W-1). In addition, the long-term photoelectric measurements indicate that the 2D Se-based photodetector has good time and cycle stability. Our results show that 2D Se has promising potential in liquid-based photo-detectors.