Graphene/CdS Nanocomposite Enhanced Interface For Construction Of Electrochemical Sensor And Its Application To The Detection Of Pharmaceuticals And Pollutants

In this paper, a low-temperature water-phase method was proposed to synthesisgraphene/CdS （GR-CdS） nanocomposite. FSEM, XRD, UV-Vis, FTIR, EIS were used toanalysis their morphology, composition, structure, functional groups and electrochemicalproperties. As GR-CdS nanocomposite enhanced interface can significantly improved thevoltammetric responses of the modified glassy carbon electrode, we prepared a novelelectrochemical sensor for the sensitive determination of pharmaceuticals and pollutants.The main contents include the following three parts:1. Comparing with different modifiers, GR-CdS nanocomposite can effectivelyenhance the electrochemical response of the sensor due to the synergistic effect ofgraphene and cadmium sulfide, which improves the fixed amount of DNA on theelectrode surface and promotes the electron transfer. The fabricated sensor was used todetect kanamycin sulfate in phosphate buffer solution at pH7.0. In the range of0.10to1.0mg mL^-1, the decrease ratio for the oxidation peak current of guanine （R%） wasproportional to the concentration of kanamycin. The linear equation is expressed as: R%=0.1389+27.76c （correlation coefficient r=0.994）. The proposed sensor was also usedto monitor the degradation of kanamycin and the results were in agreement with that ofUV-Visible spectrophotometry.2. Based on the interaction of phenformin with DNA, we realized the sensitivedetermination of phenformin hydrochloride by electrochemical method. A linearrelationship between the decrease ratio for the oxidation peak current of guanine （R%）and the concentration of phenformin was found in the concentration range of1.0×10^-6to1.0×10^-3mol L^-1. The linear equation is expressed as: R%=1.604+46.10c (mmolL^-1)（correlation coefficient r=0.996）. By UV-Visible spectrophotometry studies, wefound that there is an electrostatic interaction between phenformin and DNA. In addition,we measured the content of phenformin in commercial phenformin tablets and the result is close to that of HPLC method with the mean relative deviation of0.553%.3. The highly sensitive determination of hydroquinone was performed on GR-CdSmodified GCE by detecting its direct electrochemical responses. Electrolytes andmodifiers had affect on the electrochemical responses of hydroquinone. And the redoxpeak current and peak potential of hydroquinone varied with pH and scan rate. Theelectrochemical response of hydroquinone with different DNA concentration wasmeasured by electrochemical method, from which we found that the peak current of HQdecreased linearly with the concentration of DNA in the range of5-500μg mL^-1. Thelinear equation is expressed as: Ip（μA）=101.8–0.1184c (μg mL^-1), r=0.994. Inaddition, the GR-CdS modified electrode realized the selective and simultaneousdetection of catechol, hydroquinone and resorcinol, as well as the degradation monitoringof hydroquinone with catechol and resorcinol coexisting.