Selective Detection of Cysteine at a Mesoporous Silica Film Electrode Functionalized with Ferrocene in the Presence of Glutathione
Résumé
Unmodified and ferrocene-functionalised mesoporous silica layers exhibiting vertical nanochannels have been grown by electrochemically assisted self-assembly onto indium-tin oxide (ITO) and the resulting film electrodes have been applied to the electrochemical detection of cysteine. When using the unmodified film electrode and ferrocenedimethanol (Fc(MeOH)2) as mediator in solution, both cysteine and glutathione can be oxidised by Fc(MeOH)2 + generated at the electrode surface, following an EC' mechanism, but the electron transfer rates were three times faster with cysteine than with glutathione. This can be exploited for the reagent-free selective detection of cysteine over glutathione by using a ferrocene-functionalised mesoporous silica film on ITO electrode, based on a combination of charge transfer kinetic and mass transport limitations through the oriented nanochannels. This has been demonstrated here by cyclic voltammetry and amperometry in a flow injection analysis mode.
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