Application Of Electrochemical Sensor Based On Graphene Composites

The emergence of nanomaterial with special properties, which provided good basis forthe development of novelty and sensitive electrochemical biosensor. The developedbiosensors based on nanomaterial exhibited high sensitivity, good selectivity, low cost andeasy miniaturization, thus providing a new promising tool for drug and pesticide detection. Inrecent years, the intrinsic characteristics of graphene （GR） and graphene nanocomposites havecreated enormous interests. The research work aims at combining with different advantage ofgraphene composites. By using GR-Au, GR-ZnO and IL-functionalized graphene （IL-GR）nanocomposite as modified electrode materials, a series of electrochemical biosensors withgood performance were fabricated for the rapid detection of drugs and organophosphoruspesticide. The main contents of the paper is as follows:1. A glassy carbon electrode modified with Au/GR nanocomposites, was prepared forsimultaneous determination of isoniazid （INZ） and ascorbic acid （AA）. In0.1mol/L PBS（pH=3.5） buffer solution, using cyclic voltammetry （CV） to investigate the electrochemicalbehavior of INZ and AA. Under the optimal experimental conditions, the linear relationshipbetween the peak current and the concentration in the range of3.0×10-6to1.5×10-4mol/L forINZ and3.0×10-5to1.0×10-3mol/L for AA, with the detection limits of8.0×10-7mol/L and6.0×10-6mol/L （S/N=3）, respectively.2. A highly sensitive electrochemical biosensor for phoxim determination wasconstructed by immobilizing acetylcholinesterase （AChE） onto the surface of a glass carbonelectrode modified by graphene-ZnO （GR-ZnO） nanocomposite film. The nanocomposite notonly provide a biocompatible microenviroment to keep the bioactivity of AChE, but alsoexhibited a strong synergetic effect on improving the sensing properties of phoxim. In0.1mol/L phosphate buffer solution （pH=7.5） containing1.0mmol/L acetylthiochoine chloride（ATCl）, the response current changes of the fabricated biosensor was studied in the presenceof phoxim. Based on this, a novel electrochemical method for phoxim determination wasconstructed. Under the optimum experimental conditions, the inhition rate of phoxim wasproportional to the logarithmic value of phoxim from1.0×10-11to1.0×10-6mol/L, with the detection limit of3.4×10-12mol/L （S/N=3）.3. A novel electrochemical acetylcholinesterase （AChE） biosensor was successfullyfabricated based on IL-GR nanocomposite modified glassy carbon electrode via the filmforming of chitosan （CHIT）. The obtained biosensor was denoted as AChE/IL-GR-CHIT/GCE. The results showed that in the presence of1.2mmol/L ATCl, the oxidation peakcurrent was increased at the AChE/IL-GR-CHIT/GCE in0.1mol/L PBS （pH=7.5）, butobvious lowering of the peak current was also observed when phoxim was added. Thus, anovel method was studied for pesticide determination. The immobilized AChE showedfavorable affinity to ATCl and the apparent Michaelis-Menten constant is1.11mmol/L.Under the optimum conditions, a good linear relationship between the rate of decrease inoxidative peak current （I%） and logarithm of phoxim concentration was found in the range of2.0×10^-10to1.0×10^-6mol/L. The detection limit of the biosensor was6.0×10-11mol/L（S/N=3）.