Glassy carbon electrodes (GCEs) modified with Lcysteine (L-cys)/gold nanoparticles (AuNPs)/nitrogen-doped graphene (NG) composite were prepared to fabricate a novel electrochemical sensor for lead. AuNPs were uniformly dispersed into NG and L-cys was successfully decorated on AuNPs through the S-Au bond. The L-cys/AuNPs/NG exhibited a well-distributed nanostructure and high responsivity toward Pb(II). The results indicated that L-cys/AuNPs/NG/ GCE exhibited the highest peak current, reflecting that the Lcys/AuNPs/NG composites showed the best response signal toward Pb 2+ . Under optimized conditions, a linear relationship between the current intensity and Pb 2+ concentration was obtained in a range of 0.5-80 μg L −1 with a detection limit of 0.056 μg L −1 (S/N = 3). The analytical interference procedure and practical application were investigated using the prepared electrode, which exhibited an acceptable result.

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A novel sensitive and elective electrochemical sensor was developed to detect methyl parathion (MP) based on a glassy carbon electrode (GCE) modi¯ed with gold nanoparticles (AuNPs)/ graphene nanocomposites¯lm. The AuNPs were modi¯ed onto graphene sheets using NaBH 4 as a reductant. The obtained AuNPs/graphene nanocomposites were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical behavior of MP and interference studies were then investigated. Compared with metal ions and nitroaromatic compounds, which exist in environmental samples, the AuNPs/graphene/GCE exhibited high adsorption and strong a±nity toward MP. Under optimized conditions, the oxidation peak current of MP was linear to its concentration within the range of 4:0 Â 10 À7 -8:0 Â 10 À5 M, with a detection limit (S=N ¼ 3) of 8:5 Â 10 À8 M. These results indicated that the AuNPs/ graphene nanocomposites displayed a synergic e®ect involving the catalytic characteristics of graphene and AuNPs nanocomposites, which can e®ectively improve the electrochemical properties of MP. Furthermore, the AuNPs also enhanced sensor sensitivity to MP. Therefore, the AuNPs/graphene/GCE could be a promising sensor for the fast, sensitive and selective detection of MP in real samples.