Fabrication of poly- and single-crystalline platinum nanostructures using hole-mask colloidal lithography, electrodeposition and annealing.

Colloidal lithography (CL) is a generic name for a collection of nanolithographic techniques, based on using colloidal nanoparticles as pattern (mask)-defining entities to produce various nanostructures. A key step in CL processes is the deposition, usually by evaporation or sputtering, of the material that makes up the final nanostructures. We have for the first time combined a special version of CL, called hole-mask colloidal lithography (HCL), with electrodeposition. We demonstrate how electrodeposition of Pt onto Au and carbon substrates, through a lithographic mask, can be used to prepare well-defined nanostructured surfaces. The results are compared with evaporated structures and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cyclic voltammetry. Specific results are: (i) electrodeposition generates structures with very good adhesion, (ii) due to differences in the deposition mechanism, structures with much larger aspect (height/width) ratio can be made with electrodeposition than with evaporation and (iii) the originally deposited polycrystalline nanoparticles can be annealed into single crystals, as demonstrated by electron diffraction, SEM and TEM, before and after annealing, which is of great value for fundamental (electro)catalysis studies.