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Abstract
L-Cysteine is combined onto gold electrode to form a self-assembled monolayers modified electrode (L-Cys/Au SAMs) by taking advantage of strong sulfur-gold interaction. ATR-FTIR, SEM, cyclic voltammetry (CV) and impedance were used for the characterization of the film. It shows excellent stability upon voltametric scanning and a good voltametric response towards hydroquinone with the potential ranged from 0.8 to –0.2 V (vs.SCE) in 0.5M HAc-NaAc buffer solution (pH 4.8). The oxidation potential of hydroquinone on the modified electrode shifted negatively about 330 mV as compared with the bare gold electrode. The plot of catalytic current vs.its concentration has a good linear relation in the range of 2.0×10-6~2.0×10-4M with the correlation coefficient of 0.9986 and the detection limit of 4.0×10-7M by different pulse voltammetry (DPV). Mechanism for the electrocatalytical process has been studied.
Highlights
Self-assembled monolayers (SAMs) are ordered molecular assemblies formed by the adsorption of an active surfactant on a solid surface [1]
We employed L-cysteine (HSCH2CH(NH2)COOH) to modify the gold surface for the determination of hydroquinone in photographic imagine effluents because XPS[17] and FT-IR[18] spectroscopic studies had shown that cysteine could bind onto the gold surface through the strong sulfer-gold interaction and the surface was functionalized with amino acid[19]
Electrochemical measurements were preformed with a three-electrode system comprising a bare gold electrode or L-cysteine self-assembled monolayers modified gold electrode (i.e. L-Cys/Au SAMs) as the working electrode, a saturated calomel electrode (SCE) as the reference electrode and a platinum sheet as the counter electrode
Summary
Self-assembled monolayers (SAMs) are ordered molecular assemblies formed by the adsorption of an active surfactant on a solid surface [1]. Electrochemical measurements were preformed with a three-electrode system comprising a bare gold electrode or L-cysteine self-assembled monolayers modified gold electrode (i.e. L-Cys/Au SAMs) as the working electrode, a saturated calomel electrode (SCE) as the reference electrode and a platinum sheet as the counter electrode. The bare gold electrode was polished to a mirror-like surface with 0.05μm α-Al2O3 and immersed in Piranha solution (a hot mixed solution of 30% H2O2 and concentrated H2SO4, volume ratio 1:3), rinsed ultrasonically with water and absolute ethanol and sonicated in twice-distilled water. This electrode was voltammetrically cycled and characterized in 0.5 M H2SO4 until a stable cyclic voltammogram was obtained. L-Cys/Au SAMs was prepared by soaking the clean gold electrode in 0.05 M L-cysteine solution for 24h
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