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A special electrochemical sensor was developed based on molecularly imprinted polymer (MIP), which was formed by the dopamine (DA) self-polymerization on the surface of Pd-Cu bimetallic alloy functionalized poly (diallyldimethylammonium chloride) -dispersed graphene (PDDA-Gr). This sensor takes advantages of molecularly imprinted technique and nanocomposite to realize the application of amaranth determination with high selectivity and sensitivity. In this study, the nanocomposite PDDA-Gr-(Pd-Cu) characterized by various techniques provides large surface area and accelerates the electron transfer process. The imprinted composite deposited on the surface of PDDA-Gr-(Pd-Cu), not only provides abundant specific cavities to amaranth, but also decreases the thickness of molecularly imprinted polymer leading to high conductivity. The electrochemical behavior of amaranth on the modified electrode was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). After optimization, the anodic peak current showed a linear relationship with the concentration of amaranth in the range of 0.006–10 μM, and the limit of detection (LOD) was 2 nM. The proposed sensor distinguished amaranth from other structurally similar substances such as sunset yellow and tartrazine with good results. In addition, the molecularly imprinted sensor proposed in this study was successfully applied to determine amaranth in the soft drink with satisfactory recoveries.

An electrochemical sensing platform was fabricated based on composition of poly(sodium 4-styrenesulfonate) (PSS), graphene (GN) and WO3 nanorods on glassy carbon electrode (GCE). The PSS-GN/WO3 nanocomposite significantly increased the oxidative activity of puerarin due to the individual merit and mutual effect of PSS-GN and WO3 nanorods which improved the performance of the electrochemical sensor with high sensitivity. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) measurements were used for the detection of puerarin. Under the optimal conditions, the oxidation peak currents of puerarin increased proportionally to the concentration within the range of 0.06-0.6μmolL-1 and 0.6-6.0μmolL-1, and the limit of detection was 0.04μmolL-1. The proposed modified electrode was highly sensitive and was successfully applied to determine puerarin in the pharmaceutical sample and human plasma with satisfactory recoveries. The as-prepared PSS-GN/WO3/GCE electrochemical sensor offers a feasible way for designing simpler, low-cost, no toxic and environment-friendly sensors based on WO3 nanorods.

In this work, PtCu bimetallic nanoparticle was deposited on poly (styrene sulfonate) (PSS) functionalized graphene (Gr) to form a nanocomposite PtCu/PSS-Gr and its enzyme-like activity was investigated. Benefiting from the synergistic effect from Pt and Cu monometal as well as the superior properties of PSS-Gr, such as large surface area, good dispersity, strong adsorption of substrate and additional peroxidase-like activity, the PtCu/PSS-Gr nanocomposite was demonstrated as an excellent peroxidase mimic to catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2. Combined with molecularly imprinted polymer (MIP), a new colorimetric approach for puerarin detection was proposed with the linear range of 2 × 10−5-6 × 10−4 mol L−1 and LOD of 1 × 10−5 mol L−1. The combination of MIP with PtCu/PSS-Gr nanocomposite not only endowed the determination of puerarin with high selectivity, but also realized the detection of small molecules which are neither substrate of the nanozyme nor substances with strong oxidizing or reducing activity by using peroxidase-like catalytic activity of nanozyme, expanding the application of nanozyme.

An electrochemical sensing platform was fabricated based on composition of poly(sodium 4-styrenesulfonate) (PSS), graphene (GN) and WO