Highly-sensitive Electrochemical Methods For The Detection Of Oxytetracycline And Amaranth Based On The Signal Enhancement Of Solvent-exfoliated Graphene

Graphene possesses many excellent properties, such as large surface area, high catalytic activity, and strong accumulation ability, which has been widely used in electrochemical sensing, but they were mainly prepared by chemical oxidation-reduction method. With the rapid progress in the research on the preparation of graphene, solvent exfoliation is considered to be a simple and efficient method for preparation of high quality graphene. However, the electrochemical sensing studies based on the solvent exfoliation graphene are still in its infancy. In this thesis, graphene nanosheets was easily obtained via one-step ultrasonic exfoliation of graphite powder by selecting N-methyl-2-pyrrolidone(NMP) as the solvent, and then it was used to pareapre graphene nanosheets modified electrodes. Based on its remarkably electrochemical enhancement effects, highly sensitive electrochemical methods for the detection of oxytetracycline(OTC) and amaranth were individually developed. The research work of this thesis contains the following two parts:(1) Graphene nanosheets(GS) was easily obtained via one-step ultrasonic exfoliation of graphite powder in N-methyl-2-pyrrolidone(NMP). After centrifugation, the obtained GS was re-dispersed into N,N-dimethylformamide(DMF), a kind of volatile solvent with lower boiling point, and GS modified glassy carbon electrode(GS/GCE) was then prepared by solvent evaporation. Based on the strong oxidation signal enhancement on the surface of GS, the electrochemical behavior of OTC was investigated. Experiment parameters were further optimized, we chose pH 7.0 phosphate buffer solutions, 4 ?L of GS suspension, open circuit potential and 3 min accumulation for detection, a highly sensitive electrochemical method for the detection of oxytetracycline(OTC) was developed. The linear range was from 0.05 to 1 ?M, and the limit of detection was as low as 15 nM.(2) The electrochemical behavior of amaranth has been examined. Compared with the unmodified electrode, GS/GCE significantly increases the oxidation signal of amaranth, showing remarkably signal enhancement effects. Experiment parameters were further optimized, we chose pH 4.6 acetate buffer solution, 5 ?L of GS suspension, initial potentials of 0.4 V and 3 min accumulation for detection, a novel electrochemical method was proposed for the determination of amaranth. The linear range was from 5 to 200 nM, and the limit of detection was as low as 1.5 nM. Finally, this new method was successfully used to detect amaranth in soft drinks samples.