Exfoliation of Layered Topological Insulators Bi₂Se₃ and Bi₂Te₃ via Electrochemistry

Among layered materials, topological insulators such as Bi₂Se₃ and Bi₂Te₃ are lately attracting much attention due to particular electronic properties and, especially with Bi₂Te₃, excellent thermoelectric properties. Methods of preparation of few-layered nanosheets of Bi₂Se₃ and Bi₂Te₃ range from the bottom-up chemical vapor deposition or hydrothermal synthesis from oxide precursors to the top-down mechanical exfoliation and liquid-based exfoliation supported by sonication from the natural bulk crystals. Here, we propose a simple and rapid electrochemical approach to exfoliate natural Bi₂Se₃ and Bi₂Te₃ crystals in aqueous media to single/few-layer sheets. The exfoliated materials have been characterized by scanning transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction, high-resolution transmission electron microscopy, and Raman spectroscopy in addition to evaluation of their electrochemical properties. This electrochemical procedure represents a simple, reagent-free, and scalable method for the fabrication of single/few-layer sheets of these materials.