Self-Transformation of 2D SnSe Nanosheets into SnO₂/Se Nanocomposites for Efficient Photodetection

The rapid development of liquid exfoliation technology has boosted fundamental research and applications of ultrathin two-dimensional (2D) materials. However, the small-sized exfoliated 2D materials with a high specific surface area may exhibit poor chemical stability. Understanding the stability of 2D crystals will be significant for their preservation and service and for the development of new stable phases via the spontaneous transition from unstable structures. Here, we synthesized SnSe/SnO2/Se and SnO2/Se nanocomposites (NCPs) via an ingenious self-transformation process of 2D SnSe slowly reacting with OH- ions in water. The structure, carrier dynamics, and photodetection performances of the SnSe/SnO2/Se and SnO2/Se NCPs were thoroughly investigated. Owing to the favorable band alignment, fast recombination time, and excellent electron-transport layer of SnO2, the SnO2/Se NCPs exhibited superior photoresponse performance (400 times that of pure SnSe nanosheets). Our findings provide a new basis for the study of the stability of low-dimensional materials in water and will allow the development of water-based applications such as high-performance photoelectrochemical photodetectors, catalysts, and energy-storage devices.