Fabrication and electrochemical determination of l-cysteine of a composite film based on V-substituted polyoxometalates and Au@2Ag core-shell nanoparticles

In this work, a novel composite film containing H7P2Mo17V1O62 (P2Mo17V) and Au-Ag bimetallic core-shell nanoparticles (Au@Ag NPs) has been fabricated on quartz slides, silicon wafers and ITO electrodes by the layer-by-layer self-assembly technique. The composite film was characterized by UV-vis spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) measurements. Due to the synergistic effect between Au and Ag, the composite film modified electrode showed excellent electrocatalytic activity toward the oxidation of l-cysteine with a broad linear range of 2.5 × 10−8-7.625 × 10−6 M, a low detection limit of 2.76 × 10−8 M (S/N = 3), a high sensitivity of 1.7946 μA/μM and fast response time (<2 s). In addition, the electrode exhibited excellent reproducibility and long-term stability as well as negligible interference from l-tryptophan, l(+)-glutamic acid, citric acid, lactic acid and glucose. Furthermore, the applicability of this sensor was successfully employed to detect l-cysteine in milk samples.