Improved surfaced-enhanced Raman scattering based on electrochemically roughened silver substrates modified through argon plasma treatment

A new surface-enhanced Raman scattering (SERS)-active silver substrate has been developed by using a combination of electrochemical triangular-wave oxidation/reduction cycles (ORCs) and argon plasma treatment to roughen the substrate, increasing its SERS effect. In the first step, a mechanically polished Ag substrate was roughened through triangular-wave ORCs in an aqueous solution containing 0.1 M KCl. Next, the electrochemically roughened Ag substrate was treated with radio frequency-excited Ar plasma. 2,2′-Bipyridine (Bipy) was used as a Raman probe to evaluate the SERS enhancement provided by the new Ag substrate. Encouragingly, we found that the SERS intensity of Bipy increased up to sevenfold, with the SERS spectrum of Bipy exhibiting better resolution, when using the fully treated Ag substrate, relative to the use of an electrochemically ORCs-treated Ag substrate that had not been subjected to plasma treatment. The improved SERS effects were related to the coalescence of grains and hills as well as to the formation of dells and pits during the electrochemical ORCs and Ar plasma roughening processes.