Recent studies have shown that Au_xAg_1-x alloys and derived nanostructures of different geometry, composition and size can exhibit a range of new optical phenomena [1-3]. Electrodeposition of Au and Au_xAg_1-x alloys is commonly based on cyanide baths. In this work, Au_xAg_1-x alloys were electrodeposited from thiosulphate solutions on Au and indium-tin-oxide (ITO) substrates. Alloys of different compositions were electrodeposited at the constant potential from solutions with different 𝐴𝑢⁺:𝐴𝑔⁺ ion ratios at the constant potential. The XPS analysis of films of different thicknesses (range 20 nm-100nm) showed that the composition of electrodeposited films was homogenous and consistent during growth. In addition to that, the design of nanopatterned alloy structures on transparent substrates for potential plasmonic applications has been demonstrated.

The electrodeposited Au_xAg_1-x alloys were used to obtain nanoporous gold (NPG) by selective electrochemical Ag dissolution. The resulting NPG films were characterised electrochemically by surface area measurements using Pb underpotential deposition (UPD). It was observed that repeated cycling of Pb UPD on the NPG led to changes in the surface porosity. Repeated potential cycling of Pb UPD on NPG resulted in 'coarsening' of the porous structure. The study showed changes in porosity size depending on the number of potential scans, scan rate, and Au ligaments' initial size (i.e. initial alloy composition). Electrochemical and surface characterisation techniques were used to monitor the evolution of the NPG structures with UPD cycling

References

[1] G. Guisbiers, R. Mendoza-Cruz, L. Bazan-Diaz, J. J. Velazquez-Salazar, R. Mendoza-Perez, J. A. Robledo-Torres, J. L. Rodriguez-Lopez, J. M. Montejano-Carrizales, R. L. Whetten, Jose-Yacaman, M. ACS Nano, 10, 1 (2016) 188-198.

[2] C. Gong, M. S. Leite, ACS Photonics, 3, 4 (2016) 507-513.

[3] G. Wang, X. Chen, S. Liu, C. Wong, S. Chu, ACS Nano, 10, 2 (2016) 1788–1794.