Surface Plasmon Resonance of Au Thin Films Modified By Catalyst Monolayer

Abstract

In this talk, we present the results and modeling o the catalyst monolayer modification effects on plasmon resonance of Au thin films. The experiments are conducted using an attenuated total reflection arrangement in which p-polarized light is incident through a prism onto a thin (-400 A) Au film deposited on the mica substrate. (Kretschmann configuration [[1]]). The angle of incidence on the base of the prism is greater than the critical angle for the prism: electrolyte interface and SPs are excited by the evanescent wave generated under these conditions of total internal reflection. The excitation is manifested by a decrease in the intensity of reflected light. The Pd monolayer on Au were electrodeposited using procedure reported by Kolbe et al [[2],[3]], while the Pt submonolayer/monolayers were deposited on Au using Surface Limited Redox Replacement (SLRR) of Pb UPD monolayer [[4]]. The plasmon resonance frequency of Au(hkl), PdML/Au(hkl) and PtML/Au(hkl) and PtSML/Au(hkl) were investigated as a function of the applied potential in the range between -0.24 V to 0.4 V vs. SCE. The comparative analysis, between Au and catalyst monolayer modified Au(hkl) samples indicate that SP resonant frequency change is induced by both; surface charge and dipole moment of the surface as well as he adsorption of H on the catalyst monolayer surface in the UPD region. The latter effect is quantified using subtractive analysis between the Au and catalyst modified Au surface and solutions with different pH. In conclusion, we present a simple model describing the catalyst monolayer effect on plasmon resonance of Au films. [1] E. Kretschmann and H. Raether, Z. Natutforsch. 23a (1968) 2135. [2] L.A. Kibler, M. Kleinert, R. Randler, D.M. Kolb, Surface Science, 443 (1999) 19. [3] J. Tang, M. Petri, L.A. Kibler, D.M. Kolb, Electrochimica Acta, 51, (2005) 125 [4] K. Sasaki et al, Electrochim. Acta, 55, (2010) 2645.