Preparation of SERS‐active substrates with large surface area for Raman spectral mapping and testing of their surface nanostructure

Abstract

Surface-enhanced Raman scattering (SERS) is a powerful technique of Raman signal detection of substances at a low concentration level. It allows observation of structural details of films with very small thicknesses. It is possible to achieve the enhancement of Raman signal of species located on the surface of properly prepared SERS-active substrates of up to ca 10 6 . One of the main requirements for the substrate to be SERS-active is the proper roughness of the surface. In this work different SERS-active Au and Ag substrates suitable for spectral mapping were prepared using procedures which consisted of electrochemical deposition of metal layer and further roughening with oxidation-reduction cycles (ORC) treatment. The nanostructures of the metal surfaces were tested using atomic force microscopy (AFM). Monolayers formed both by covalent and noncovalent linkages to the metal surface were detected and Raman spectral maps were then measured. Roughening procedure of the substrates was optimized and its effect on the SERS enhancement was discussed. The relations among the surface nanostructure, optimal roughening, type of linkage of the analyte to the surface of the substrate and the Raman signal enhancement for the experimental conditions were studied.

Surface-enhanced vibrational spectroscopy of B vitamins: what is the effect of SERS-active metals used?

“…After the pretreatment of platinum targets, described in the previous study [32], the electrochemical procedure of either gold or silver deposition followed. All procedures were performed in an electrochemical cell in which a gold wire or a flat silver electrode was used as the anode and the platinum target as the cathode.…”

“…After electrodeposition, oxidation-reduction cycles (ORC) were applied as described previously [32]. Afterwards, elimination of cyanides adsorbed on the surface from the gilding bath was performed: the target was immersed in a boiling solution of ammonium persulfate for 5 h. Finally, substrates were thoroughly rinsed with redistilled water.…”

“…The silvering bath was prepared according to the procedure described elsewhere [32]. After cathodic electrodeposition, the silver substrate was thoroughly rinsed with redistilled water.…”

“…After cathodic electrodeposition, the silver substrate was thoroughly rinsed with redistilled water. All substrates were characterized by atomic force microscopy and scanning electron microscopy as described elsewhere [32].…”

Comparison of SERS effectiveness of copper substrates prepared by different methods: what are the values of enhancement factors?

“…Colloidal systems can be prepared by chemical reduction of a cupric salt using borohydride as the reduction agent. [28,29] In our previous studies, we compared large substrates of different metals, namely, silver [30] , gold [31] and copper [24] . It was observed that the SERS spectra measured on copper substrates were comparable with those obtained on silver or gold substrates, but the values of the EFs were not estimated.…”