Preparation Of Graphene-based Nanocomposites And Its Application In Electrochemical Sensing

The graphene oxide was used as the original material to prepare several graphene-based nanocomposites. The scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) etc. methods were used to characterize the modified materials, and then the nanocomposites were modified onto the electrode surface in order to construct several different electrochemical sensors, and their applications were studied in the determination of daily food additives. The main contents of this paper have been described as follows:The magnetic nanoparticles Fe3O4 and SDS functionalized graphene (GR) were doped into carbon paste to prepare a novel electrochemical sensor Fe3O4/GR/CPE. The CV, EIS were used to characterize the electrochemical properties of the sensor. The relationship between the concentration of Amaranth (AM) and its oxidation peak current was using LSV to study, and a new electrochemical determine method was established for determining AM in local red wine, and the determination results in line with the requirements of quantitative determination. Meanwhile, a new type of electrochemical quantitative means for determining the actual content of AM in real samples was established.Using the constant potential deposition (-0.2V) method to make nano-gold (AuNPs) was deposited onto the carbon paste electrode surface which was doped GR before. Under optimal experimental conditions (supporting electrolyte, pH value, scanning rate), by using CV, EIS, SEM to characterize the properties of different sensors and the electrochemical behavior of Melamine (Mel) on different sensors were studied. The results showed that, AuNPs/GR-CPE sensor had a good response for electrochemical behavior of Mel, it was founded that the reducing amount of Mel peak current (AI) and its concentration in 2.0x10-10～8.0x10-7 mol·L-1 and 8.0×10-7～8.0×10-3 mol·L-1 had a good linear relationship by differential pulse voltammetry (DPV). This method has been successfully applied to the electrochemical quantitative determination of Mel in commercial milk and milk powder.The Mel monomers were polymerized onto GR electrode surface to form a layer (poly) melamine film (PMA/GR-CPE) by electropolymerization method, the sensor can be used to simultaneous determination of bisphenol A (BPA) and hydroquinone (HQ). Using SEM, EIS, CV methods to characterize the prepared electrochemical sensors. It was founded that PMA/GR-CPE had a significant effect on separation of BPA and HQ by CV studied, the oxidation peak potential difference of both (AEp) was 301mV approximately. The PMA/GR-CPE kinetic parameters of BPA and HQ electrode reaction were determined using chronoamperometry (CA) and chronocoulometry (CC). The relationship of oxidation peak current and their concentration were studied using DPV, while using standard addition method to detect BPA and HQ in real wastewater and tap water samples, the measurement results were satisfactory.The AuNPs were modified onto the surface of nano-ceria (CeO2) carbon paste electrode by electrochemical deposition methods; a novel nitrite (NO2) electrochemical sensor (AuNPs/CeO2-CPE) was established. Using SEM, EIS to characterize the properties of modify materials and using CV to study the influence of the sensor on nitrite (NO2-) electro-catalytic oxidation behavior. Experimental results showed that the sensor had good effect on electrical catalytic oxidation of NO2-. The NO2-electrode kinetic parameters on different electrodes were measured using CA and CC. Using LSV to study the relationship between oxidation peak current of NO2- and its concentration. The results showed that they had a good linear relationship in the concentration range of 8.0×10-7～8.0×10-3 mol·L-1, and limit of detection (LOD) of 3.2×10-8 mol·L-1. The sensor was applied to the determination of NO2- in local wolfberry; results meet the quantitative determination of requirements.