Control of shape and surface crystallography of gold nanocrystals for electrochemical applications

Colloidal gold particles can be easily produced by the reaction between HAuCl4 and N,N-dimethylformamide (DMF) without the presence of any capping agent. Depending on the amount of H2O in the reaction mixture (0-98 vol%), the shape of the produced Au particles resemble a rhombic dodecahedron (3-5 vol% H2O), a horned rhombic dodecahedron (i.e. a rhombic dodecahedron with horn-like features over every second corner, 5-7 vol% H2O), a wire or a thin plate(>20 vol% H2O). The crystallographic orientation of the particle was studied by X-ray diffraction, surface crystallography was determined by a study of the Au oxidation. Particles in which {1 1 0} surfaces dominate can be prepared, as well as particles where the lowest energy {1 1 1} surface dominates. The function of water in the reaction is discussed. The method used here presents a versatile way for the preparation of gold particles with many different shapes with minor alteration of the procedure. (C) 2013 Elsevier Ltd. All rights reserved.