Controlled growth of multi-morphology hexagonal t-Se microcrystals: tubes, wires, and flowers by a convenient Lewis acid-assisted solvothermal method

This paper reports on the controlled growth of multi-morphology hexagonal t-Se microcrystals by a convenient Lewis acid-assisted solvothermal method using the mixture of ethanol and H2O as solvent. The tubes and wires with a well-defined crystallographical structure and the flowers with chrysanthemum-, sisal-, and urchin-like shapes were obtained by changing Lewis acids and adjusting some other synthesis parameters, in particular the volume ratio of ethanol to H2O. Lewis acids were found to be crucial for the formation of the tubes and wires by not only acting as the PH regulator but also as the shape controller, owing to their hydrolysis in the solvent to in situ form H+ and hydrates. The mixture of ethanol and H2O was responsible for the formation of various followers when NH4Cl was used instead of the Lewis acids with metallic ions. The findings suggested that this should be an effective approach to the controlled growth of t-Se crystals with interesting multiple morphologies, which are of interest for both theoretical investigations and practical applications.