Direct deposition of gold nanoplates and porous platinum on substrates through solvent-free chemical reduction of metal precursors with ethylene glycol vapor

Abstract

Deposition of nanostructured metals on substrates is important for the fundamental study and practical application, such as in optics and catalysis. In this paper, we report the deposition of gold (Au) nanoplates and porous platinum (Pt) structures on substrates through solvent-free chemical reductions of chloroauric acid (HAuCl₄) and chloroplatinic acid (H₂PtCl₆) with ethylene glycol (EG) vapor at temperatures below 200 °C. The process includes two steps. The first step is the formation of a thin layer of a metal precursor on substrates by coating solution of a metal precursor. The thin metal precursor layer is subsequently dried by annealing. The second step is the chemical reduction of the metal precursor with EG vapor at 160 or 180 °C in the absence of solvent. Both the Au and Pt nanostructures deposited by this method have good adhesion to substrates, but they have different morphologies. The Au nanostructures appear as separate two-dimensional islands on the substrates, and up to 70% of them can be triangular nanoplates with the (111) crystal plane as the basal plane. In contrast, the reduction of H₂PtCl₆ gives rise to a 3-dimensional porous Pt structure on substrates. The different morphologies of nanostructured Au and Pt are tentatively related to the different surface energies of Au and Pt.