Pore-size tuning and optical performances of nanoporous gold films

• Nanoporous gold films with pore sizes of 4–140 nm are fabricated.
• The pore size is tuned by the pulse electrochemical and chemical methods.
• The coarsening of pores is controlled by the surface diffusivity of Au.
• The porous film with a pore size of 8 nm exhibits the strongest SERS effect.

Through pulse electrochemical dealloying (PED) and chemical dealloying (CD), a variety of nanoporous gold (NPG) films of 100 nm thickness with a wide range of pore size (4–140 nm) were prepared. The coarsening mechanism of pore and the effect of residual Ag on optical performances were investigated. The pore size was tuned by controlling the dissolution rate of active Ag atoms and surface diffusion rate of noble Au atoms along the alloy/solution interfaces. The maximum pore size of 140 nm was obtained by surfactant-assisted chemical dealloying (SA-CD) and the minimum pore size of 4 nm was achieved by PED. It is found that the surface diffusivity of gold in PED is about 0.4–2 × 10−20 m2 s−1, four orders of magnitude smaller than that in SA-CD (2.4 × 10−16 m2 s−1). Finally, optical performances of the NPG films were investigated by UV–vis and surface-enhanced Raman scattering (SERS) spectra. The results reveal that the NPG film with a pore size of 8 nm fabricated by PED exhibits higher surface-plasmon absorption and the strongest SERS effect.

The size-dependence of nanoporous gold (NPG) films on optical performance is investigated, where a diversification of UV–vis absorption band is observed. The NPG film with a pore size of 8 nm presents an obvious enhancement of surface-enhanced Raman scattering.Figure optionsDownload as PowerPoint slide