Fangquan Xia

Simple and signal-off electrochemiluminescence immunosensor for alpha fetoprotein based on gold nanoparticle-modified graphite-like carbon nitride nanosheet nanohybrids

A simple, signal-off electrochemiluminescence (ECL) immunosensor for sensitive and selective detection of alpha fetoprotein (AFP) was developed based on gold nanoparticle (AuNPs) modified graphite-like carbon nitride nanosheet (g-C3N4 NSs) nanohybrids (Au-g-C3N4 NHs). Compared to the g-C3N4 NS modified glassy carbon electrode (GCE), the ECL intensity is more obvious at the Au-g-C3N4 NH modified GCE due to the fact that AuNPs can promote electron transfer and electrocatalytic reduction of S2O82− to produce large amounts of hole donor (SO4˙−). Results demonstrated that the ECL signal of the g-C3N4 NSs decreased due to the interaction between antibody and antigen on the modified electrode. Thus, an ECL immunosensor for the detection of AFP was realized by monitoring the ECL intensity change of g-C3N4 NSs. The factors influencing the performance of the immunosensor were investigated in detail. Under optimal conditions, the proposed biosensor achieved a wide line from 0.001 to 5.0 ng mL−1 with a detection limit of 0.0005 ng mL−1. Furthermore, the ECL immunosensor was successfully applied to the determination of AFP in serum samples, providing a promising effective strategy for AFP detection.

Sensitive and simultaneous method for the determination of naphthol isomers by an amino-functionalized, SBA-15-modified carbon paste electrode

The amino-functionalized, SBA-15-modified carbon paste electrode (NH2-SBA15/CPE) was prepared and successfully developed for the sensitive and simultaneous electrochemical determination of naphthol isomers. The electrochemical behaviors of 1-naphthol (1-NAP) and 2-naphthol (2-NAP) on different electrodes were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in Britton–Robinson buffer solutions (pH 2.5). The results demonstrated that the NH2-SBA15/CPE exhibited better electrocatalytic performance and higher sensitivity toward naphthol isomers than those at the SBA15/CPE and bare CPE, and it could well separate their oxidation peaks by CV and DPV. Under the optimized conditions, the oxidation peak currents showed good linearity in the ranges of 1.0 × 10−8–1.0 × 10−6 M for 1-NAP and 2-NAP, with a low detection limit of 1.0 × 10−9 M (S/N = 3). More importantly, the developed method was applied to the quantitative determination of 1-NAP and 2-NAP in wastewater samples from a chemical plant and displayed satisfactory sensitivity and selectivity.

Electrochemical determination of phenanthrene based on anthraquinone sulfonate and poly diallyldimethylammonium chloride modified indium–tin oxide electrode

In this paper, specific electrochemical interaction between phenanthrene (Phe) and anthraquinone sulfonate (AQS) was first investigated by Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV). Poly diallyldimethylammonium chloride (PDDA) and AQS were modified onto indium–tin oxide (AQS/PDDA/ITO) by self-assembling. Owing to the specific interaction between AQS and Phe, the amount of Phe could be quantified by the electrochemical oxidation peak current difference of AQS at AQS/PDDA/ITO in the range from 1.0 × 10−12 to 1.0 × 10−9 mol L−1 with a linearity (r = 0.9942) and a low detection limit of 5.0 × 10−13 mol L−1 (S/N = 3). As an example of its practical application, the new sensor was used for quantitative determination of Phe in a standard sample and cloud-rain water samples of Mount Taishan with satisfactory results.

An ultrasensitive electrochemical immunosensor based on C60-modified polyamidoamine dendrimers and Au NPs for co-catalytic silver deposition

A convenient, highly efficient and ultrasensitive electrochemical immunosensor was developed using in situ deposited silver nanoparticles (Ag NPs) as tracing tags for fetoprotein (AFP) detection. The function of the immunosensor was achieved by a co-catalytic effect on the surface of nanocomposites containing polyamidoamine (PAMAM) dendrimers coated with C60 (PAMAM-C60 NPs) and gold nanoparticles (Au NPs). On the surface of Au@PAMAM-C60 NPs labeled with an antibody (Ab2), via a sandwich-type immunoreaction, silver ions in solution were reduced to metallic Ag NPs. The electrochemical signal of the in situ deposited Ag NPs could be utilized to monitor the immunoreaction. Under optimum conditions, the peak current of the Ag NPs increased with increasing AFP concentration in the range from 0.1 pg mL−1 to 10 ng mL−1, with a detection limit of 0.03 pg mL−1. Importantly, the designed electrochemical immunoassay strategy exhibited excellent sensitivity, stability, selectivity, and reproducibility.