Electrochemical performance of l-cysteine–goldparticle nanocomposite electrode interface as applied to preparation of mediator-free enzymatic biosensors

An l-cysteine–goldparticle nanocomposite (CGN) was prepared by a self-assembly process to involving l-cysteine on gold nanoparticles. The results of scanning electron microscopy (SEM) showed the aggregation of CGN in the absence of Nafion and the uniform dispersion of CGN in the presence of Nafion. A new electrode interface was constructed by using CGN to be immobilized in the network of a Nafion membrane on a glassy carbon (GC) electrode. The electrochemical characteristics of such new electrode interface were compared with those of a GC electrode using PBS (pH 7) and a potassium ferricyanide solution (K3Fe(CN)6) by cyclic voltammetry. The new electrode interface had low background current, and it could accelerate the electron-transfer and improve electrochemical activity of the electrode. Through comparison with the cyclic voltammograms of different electrode interfaces (GC/Nafion, GC/Nafion–goldparticle, GC/CGN, GC/Nafion–CGN) for the Fe(CN)63− solution, it was found that on GC/Nafion–CGN (GC/NCGN), the electrochemical redox reaction of Fe(CN)63− was the best reversible one, that is, GC/NCGN had the highest electron-transfer ability. Based on the good electrochemical properties, GC/NCGN was utilized to fabricate the third-generation horseradish peroxidase (HRP) biosensor. The HRP biosensor exhibited good response to H2O2, and displayed the remarkable sensitivity and repeatability.