Role of stirring assist during solvothermal synthesis for preparing single-crystal bismuth telluride hexagonal nanoplates

Abstract

We investigated the role of stirring assist during solvothermal synthesis for preparing high quality bismuth telluride (Bi2Te3) hexagonal nanoplates. We performed a series of experiments that comprised solvothermal synthesis with stirring assist at 500 rpm and without stirring assist. As a result, high purity Bi2Te3 hexagonal nanoplates with uniform morphology and edge length of 400–800 nm were obtained by solvothermal synthesis using stirring assist, whereas intermediate products such as tellurium and tellurium oxide compounds were also produced besides the Bi2Te3 hexagonal nanoplates by solvothermal synthesis without stirring assist. To further study the nanostructure of the nanoplates with stirring assist, we performed high-resolution transmission electron microscopy and selected-area electron diffraction analysis. It was found that the Bi2Te3 hexagonal nanoplates were composed of rhombohedral phases and highly single-crystalline structures. Based on the experimental and analytical results, we propose a possible reaction process and growth mechanism of the Bi2Te3 hexagonal nanoplates. The reaction rate is the key factor to control the shapes of nanostructures. When the reaction rate was sufficient, it proceeded to the final stage, and then Bi2Te3 nanoplates were produced. However, when the reaction rate was insufficient, the entire morphology evolution process was terminated at the intermediate stage, and intermediate products besides Bi2Te3 nanoplates were also produced.