Electrochemical Sensors Based On Core-Shell Nanomaterials

Electrochemical detection technology is a integration of multidisciplinary approach. As the electrochemical detection method has high sensitivity, low detection limit, wide linear range and good selectivity, electrochemical detection method can be used to detect specific substances in complex system. Electrode material is particularly important for electrochemical sensors. The novel nanomaterials can be used to fabricate electrochemical sensors, which have characteristic of simple preparation and high sensitivity. The specific works are as follows:（1） Graphene oxide was electrochemically reduced on the surface of glassy carbon electrodes （GCE） to prepare a sensor for fast simultaneous detection of Pb2 +and Hg²⁺ in water. The electrochemically reduced graphene oxide （ERGO） modified GCE exhibited enhanced analytical performance toward Pb²⁺ and Hg²⁺ due to the strong adsorptive capability, huge specific surface area and good conductivity of ERGO. The peak currents at about -0.544 V for Pb²⁺ and 0.076 V for Hg²⁺ were measured. The concentration of graphene oxide, deposition potential and deposition time were investigated. Under optimum conditions, a linear range of 1～1000 ng/mL and a low detection limit of 0.2 ng/mL were obtained for Pb²⁺, and a linear range of 1～1000 ng/mL and a low detection limit of 1 ng/mL were obtained for Hg²⁺. The ERGO modified electrode displayed good reproducibility and repeatability, which suitable for the simultaneous determination of Hg（Ⅱ） and Pb（II） in real samples.（2） Silver nanoparticles was synthesized firstly. Seed growth method was used to synthesis silver/copper oxide core-shell nanoparticles with PVP as protective agent, ascorbic acid as reducing agent. An electrochemical sensor for the determination of hydrogen peroxide was constructed by Ag/Cu₂O core-shell nanocrystals. The Ag/Cu₂O core-shell nanocrystals can significantly enhance the detection signal of H₂O₂ Under the optimized experimental conditions, the response current with the concentration of hydrogen peroxide is in a linear range of 0.0005 to 8mM and the detection limit is 0.1μM. The reproducibility and repeatability was investigated with RSD of 1.22% and 3.26% for six measurements. The developed hydrogen peroxide electrochemical sensor based on Ag/Cu₂O core-shell nanocrystals possesses advantages such as simple fabrication, fast response, low detection limit, and good reproducibility.（3） Graphene oxide was synthesized firstly. Graphene oxide was used as a reducing agent to synthesis siver nanoparticle. Then gold/siver core-shell nanoparticles was synthesized by galvanic replacement. Finally, graphene oxide was reduced by ascorbic acid as green reducing agent. An electrochemical sensor for determing hydrogen peroxide was constructed with graphene/Au-Ag core-shell nanoparticles. Under the optimized experimental conditions, the response current with the concentration of hydrogen peroxide is in a linear range of 0.01 to 10mM and the detection limit is 8μM. The reproducibility and repeatability was investigated with RSD of 2.46% and 3.37% for six measurements. The developed hydrogen peroxide sensor based on graphene/Au-Ag core-shell nanoparticles possesses advantages such as simple fabriction, low detection limit and good reproducibility.