A correlation study between the conformation of the 1,4-dithiane SAM on gold and its performance to assess the heterogeneous electron-transfer reactions

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Vol. 566; no. 2; pp. 443 - 449
• Main Authors: de Sousa, Jackson Rodrigues, Parente, Marcelo Monteiro Valente, Diógenes, Izaura Cirino Nogueira, Lopes, Luiz Gonzaga França, Neto, Pedro de Lima, Temperini, Márcia Laudelina Arruda, Batista, Alzir Azevedo, Moreira, Ícaro de Sousa
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-05-2004; Elsevier Science
• Subjects: 1,4-Dithiane; ac impedance; Adsorption; Chemically modified gold electrode; Chemistry; Cyt c; Electrochemistry; Exact sciences and technology; General and physical chemistry; Study of interfaces; Surface-enhanced Raman scattering; 1,4-Dithiane; Cyt c; Surface-enhanced Raman scattering; Chemically modified gold electrode; ac impedance; Electrode adsorption; Electrode impedance; Gold; Nitrogen heterocycle; Electrode electrolyte interface; Solid electrode; Transition metal; Experimental study; Cyclic voltammetry; Molecular orientation; Six membered ring; Surface Enhanced Raman Spectrometry; Adsorption structure; Charge transfer
• ISSN: 1572-6657; 1873-2569
• DOI: 10.1016/j.jelechem.2003.12.010

A gold electrode spontaneously modified by 1,4-dithiane (1,4-dt) organosulfur species has been characterized by cyclic voltammetry of [Fe(CN)
6]
3−/4− and cytochrome
c (cyt
c) probe molecules, SERS (surface-enhanced Raman scattering), and EIS (electrochemical impedance spectroscopy), using [Fe(CN)
6]
3−/4− as the redox-active molecule in solution. The cyclic voltammograms showed a decrease in the faradaic current response with an increase of the immersion time of the gold substrate into the 1,4-dt modifier solution, suggesting that the heterogeneous electron-transfer (hET) process of the [Fe(CN)
6]
3−/4− probe molecule occurs through the surface pinholes. This observation is an indication that the 1,4-dt chemisorption mechanism must involve a slow step that is responsible for the final configuration of the modifier molecules on the surface. The SERS spectra acquired for the surface as a function of immersion time of the gold electrode in the modifier solution presented an intensity enhancement of the bands assigned to the
trans and
gauche conformation of the 1,4-dt on the surface. The apparent rate constant,
k
app, estimated by the EIS results, decreases with increase of the immersion time indicating that the pinholes on the surface act as a microarray. This result is consistent with those observed by cyclic voltammetry of the probe molecules, i.e., the pinhole density decreases with increase of the immersion time of the gold electrode in the 1,4-dt modifier solution, and a strong attenuation of the probe molecules interfacial electron-transfer response is observed.