Hierarchical Shape Evolution of Cuprous Oxide Micro- and Nanocrystals by Surfactant-Assisted Electrochemical Deposition

Cu2O microcrystals (MCs) and nanocrystals (NCs) of various shapes were potentiostatically deposited on Ti substrates by exploiting the capping effects of differently charged surfactants on certain surfaces. Positively charged hexamethylenetetramine was adsorbed onto the {111} and {100} planes of the Cu2O crystals (copper- and oxygen-terminated surface) while negatively charged poly(vinylpyrrolidone) was adsorbed onto the 11111 planes (Cu-terminated surface due to Coulombic interaction). The difference in the adsorption behaviors of the two surfactants resulted in the synthesis of differently shaped Cu2O MCs. We were also able to systematically control the shape evolution of Cu2O NCs synthesized as cubes, truncated cubes, truncated octahedrons, and stepped octahedrons into perfect octahedrons by adding or removing surfactants successively during the electrochemical deposition process. This method is a simple, flexible, and cost-effective one and should aid in the elucidation of the shape-transformation phenomenon in other semiconductors as well as their facet-dependent properties.