Surface-Enhanced Raman Spectroscopy of Thionine-modified Gold Electrodes

H R Virdee,R E Hester

doi:10.1155/lc.9.401

Abstract

Surface enhanced Raman (SER) and resonance Raman (SERR) techniques have been used in situ to investigate thionine-modified gold electrodes. New surface roughening procedures for gold electrodes have resulted in an order of magnitude increase in the Raman signals. As a result of this, Raman spectra from leucothionine have been observed for the first time. The surface Raman spectra of both thionine and leucothionine are essentially unchanged over the pH range from 1.3 to 7 but both show major changes at pH 10. This behaviour has been rèlated to changes in the absorption spectrum of thionine at pH 1.0 where the compound is believed to exist as thionine hydroxide. At pH 1.3 and 7 the Raman signals from thionine arise from a combination of surface enhancement and resonance enhancement processes, whereas signals from leucothionine arise solely from surface enhancement. At pH 10 surface enhancement processes give rise to Raman intensity for both thionine and leucothionine.

Highlights

Electrode surfaces modified by the immobilization of electrochemically active species have attracted considerable research interest in recent years,t mainly because of their promise in applications to such processes as electrocatalysis[2] and solar energy conversion. 3 One suchH
In this work we present further surface enhanced resonance Raman spectroscopy (SERRS) and SERS results from thionine and leucothionine on gold electrodes at various pH values
Raman spectra of thionine-coated gold electrodes in contact with electrolyte solutions at pH 1.3, 7 and 10 have been measured at various applied potentials. For these measurements the gold electrode was activated for surface enhanced Raman scattering prior to coating with thionine

Summary

Introduction

Raman spectra of coated thionine were recorded in 0.05 mol dm-3 H2SO4 solution at open circuit potential 0.33 V (SCE) using 647.1 nm excitation. Raman spectra of coated thionine were recorded at various applied potentials in the range -0.20 to +0.40 V. Raman spectra of thionine-coated gold electrodes in contact with electrolyte solutions at pH 1.3, 7 and 10 have been measured at various applied potentials.

Results

Conclusion