Surface modification of Au and Ag plasmonic thin films via diazonium chemistry: Evaluation of structure and properties

Plasmon-active noble metals nanostructures based on Ag and Au thin films become widely applied in the field of plasmonics and related sensing technologies. For improvement of the metal interaction with different media, metals surface can be functionalized in order to increase/decrease hydrophilicity, lipophilicity or introduce/change the surface charge. In this paper, the surface functionalization of plasmon-active Au and Ag films using arenediazonium tosylates was described. The surface functionalization was performed in the aqueous medium by the spontaneous and electrically induced mechanisms. Functionalized surfaces were characterized by the Raman and UV–vis spectroscopies, AFM nanomechanical mapping, SEM (EDX), XPS, CVA, zeta- potential, and water contact angle measurement techniques. It was founded that the key difference between reactivity of gold and silver films is distributional behavior of grafted organic functional groups: silver has higher tendency to form clustered, island-like structure while gold is covered more homogeneously. Spontaneous modification forms approximately monomolecular thick films of organic compounds and can be used in the field of SPR or SERS sensors. Electrochemically induced activation produces thick polyphenylene layer on the metal surface and can find application in the field of tunable plasmonic devices or plasmon-based lasers.