Selective Detection of Cysteine at a Mesoporous Silica Film Electrode Functionalized with Ferrocene in the Presence of Glutathione

Abstract

Abstract Unmodified and ferrocene‐functionalized mesoporous silica layers exhibiting vertical nanochannels have been grown through electrochemically assisted self‐assembly onto indium‐tin oxide (ITO), and the resulting film electrodes have been applied for the electrochemical detection of cysteine. When using the unmodified film electrode and ferrocenedimethanol (Fc(MeOH) 2 ) as a mediator in solution, both cysteine and glutathione can be oxidized by the Fc(MeOH) 2 + generated at the electrode surface, 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‐functionalized mesoporous silica film on an ITO electrode, based on a combination of charge transfer kinetic and mass transport limitations through the oriented nanochannels. This has been demonstrated here by using cyclic voltammetry and amperometry in flow‐injection analysis mode. A sensitivity of 1.28 mA M −1 was measured for the cysteine concentration range of 3–20 μM with a repeatability of the signal between 3 and 12 %. The lowest concentration of cysteine experimentally detected was 3 μM.