Facile Fabrication of Multifunctional Three-Dimensional Hierarchical Porous Gold Films via Surface Rebuilding

We report here a novel one-step electrochemical method to fabricate three-dimensional (3D) micro-nano hierarchical porous gold films (PGFs) by the surface rebuilding of smooth gold substrates in a blank solution of NaOH with square wave potential pulse. The potential is controlled such that it involves repeated gold oxidation-reduction and intensive hydrogen evolution, where the hydrogen gas bubbles function as a dynamic template to shape the assembly of the gold nanoparticles from the oxidation-reduction. Particularly, this method is green, convenient, and economical, which enables us to fabricate the 3D porous structure from the metal itself requiring neither Au(III) species and additives in solution nor post-treatment of template removal. The pore formation and evolution have been characterized by scanning electron microscopy. The as-prepared 3D PGF is multifunctional, for example, (i) high electrocatalytic activity toward the oxidation of some fuel/biomolecules like ethanol, glucose, and ascorbic acid; (h) strong surface-enhanced Raman scattering effect with the merits of being stable and easily renewed; and (iii) interesting transition from superhydrophilicity to superhydrophobicity by decorating with a self-assembled thiol monolayer.