Abstract
A three-dimensional L-cysteine (L-cys) monolayer assembled on gold nanoparticles (GNP) providing simultaneous detection of uric acid (UA) and ascorbic acid (AA) was studied in this work. The cyclic voltammetry demonstrated that, at a bare glassy carbon electrode (GCE) or planar gold electrode, the mixture of UA and AA showed one overlapped oxidation peak; whereas when the electrode was modified with GNP, the oxidation peaks for UA and AA were separated. While a GNP modified electrode was further modified with L-cys monolayer (L-cys/GNP/GCE), namely, three-dimensional L-cys monolayer, a better separation for UA and AA response was obtained. Interestingly, the L-cys monolayer-modified planar gold electrode presented a block effect on the oxidation of AA, which was facilitated by the three-dimensional L-cys monolayer attributed to its distinct structure. The pH of solution presented a noticeable effect on the separation of UA and AA at GNP modified electrodes with or without L-cys monolayer. Wide concentration ranges from 2 × 10−6−1 × 10−3 M to UA and 2 × 10−6−8 × 10−4 M to AA could be obtained at L-cys/GNP/GCE.
Acknowledgments
This work was supported by the Research Foundation for Outstanding Young Teachers, China University of Geosciences (Wuhan) (No. CUGQNL0902).
Notes
EUA and EAA mean the oxidation potentials of UA and AA at the modified electrode.
iUA and iAA mean the oxidation currents of UA and AA at the modified electrode.
ΔE = EUA−EAA.