Fluorescence Quenching Effect of Rhodanmine 6G on Two-Dimensional Bi2Se3Crystals

Abstract

As a novel quantum material, two-dimensional crystal of Bi2Se3 is a typical topological insulator with an insulat- ing 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 fluores- cence-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 charac- terization. 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 spectros- copy 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. Keywords topological insulators; two-dimensional crystals; fluorescence quenching; Bi2Se3