关键词: 拓扑绝缘体, 二维晶体, 荧光猝灭, Bi₂Se₃

As a novel quantum material, two-dimensional crystal of Bi₂Se₃ is a typical topological insulator with an insulating bulk gap and gapless edges or surface states, which has created new opportunities for spintronics and low-dissipation electric transport. For the first time, we studied the fluorescence quenching effect of Rhodanmine 6G molecules on two-dimensional crystals of Bi₂Se₃ with the thickness ranged from 1 layer to 8 layers. Atomically-thin, high-quality two-dimensional crystals of Bi₂Se₃ with different thicknesses down to monolayer were firstly grown on mica substrates via van der Waals epitaxy. Typically, its domain size is about tens or several tens micrometers, providing a good platform for studying the thickness-dependent chemical and physical properties of two-dimensional Bi₂Se₃ crystals. Besides, as fluorescence-probe molecules with high fluorescence quantum yield, a uniform and continuous film of Rhodamine 6G molecules were deposited onto the surface of mica substrate and two-dimensional Bi₂Se₃ crystals by vacuum evaporation, on which adsorption of almost equal number of Rhodamine 6G molecules was achieved revealed by atomic force microscopy characterization. Subsequently, the measurements of fluorescence spectroscopy were conducted on the Horiba-Jobin Yvon Labram HR800 micro Raman spectrometer with a spatial resolution about 1 μm. Excited by 514.5 nm Ar⁺ laser, the fluorescence signal from 520 nm to 640 nm of Rhodanmine 6G molecules on different surfaces was collected under the same condition. It was found that the atomically-thin Bi₂Se₃ crystals can quench the fluorescence of adsorbed Rhodamine 6G molecules. Meanwhile, the thicker Bi₂Se₃ crystals show more obvious quenching ability to Rhodanmine 6G molecules. In the end, a possible quenching mechanism of fluorescence resonance energy transfer was suggested. According to the UV-Vis spectroscopy of two-dimensional crystals of Bi₂Se₃, the absorption spectroscopy of Bi₂Se₃ showed a large spectral overlap with the emission fluorescent of Rhodanmine 6G, which is the key to fluorescence resonance energy transfer.

Key words: topological insulators, two-dimensional crystals, fluorescence quenching, Bi₂Se₃