Preparation Of Graphene/electropolymerization And Electrochemical Pretreatment Modified Electrodes And Their Electrocatelysis

In this paper, we studied the electrocatalysis behavior of uranium and several biological molecules on the poly(brilliant cresyl blue), graphene and Electrochemical pretreatment(ECP)-based composites modified glassy carbon electrodes and established and electroanalysis of corresponding target analyte. The major contents including: PBCB/graphene/GCE, ECP/GCE, PBCB/ECP/GCE were synthesis through drop-casting, electropolymerization, and “two-step” ECP; The composites structure and these synthesis optimization were conducted by scanning electron microscopy(SEM), electrochemical impedance spectroscopy(EIS), and cyclic voltammetry(CV). What’s more,the prepared modified electrodes were used to investigate the electrode response behavior, the analytical condition, the interference studies and the sample analysis of uranium and several biological molecules. The specific contents as follows: 1 Preparation of graphene/poly(brilliant cresyl blue) and its ElectrocatelysisA graphene modified with poly(brilliant cresyl blue)(PBCB) glassy carbon electrode was fabricated by a simple method of drop-casting and electropolymerization for facilitating electrocatalytic detection of epinephrine(EP) and uranium(U(Ⅵ)). Firstly, the effect of volume and sequence of graphene modification were investigated by SEM, EIS, and CV. The results showed that the nanocomposite prepared by drop-casting 10 μL graphene then electropolymerization BCB exhibit best electrochemical performance, such as better electrocatalytic behavior and faster charge transfer rate. And then surface characterization of PBCB/graphene/GCE was conducted by electrochemical impedance spectroscopy(EIS), whose results showed that the electron transfer process at PBCB/graphene is faster than at bare GCE, graphene/GCE and PBCB/GCE. And the scanning electron microscopy(SEM) image confirmed the graphene dispersion incorporated with PBCB on the GCE. A noticeable enhancement in the microscopic area of the electrode resulted in an appreciable increase of the peak current of EP and U(Ⅵ)(~9.4 and 16.9 times). The catalytic oxidation peak currents obtained from cyclic voltammetry(CV) increased linearly with EP and U(Ⅵ) concentrations in the range of 1 μM to 1000 μM and 0.05 μg/mL to 100 μg/mL, with the limit of detection 0.24 μM and 0.016 μg/mL(0.016 mg/L), respectively(S/N=3). Furthermore, the fabricated PBCB/graphene/GCE nanocomposite can determine EP in the presence of a large excess of ascorbic acid(AA) and uric acid(UA) by differential pulse voltammetry(DPV). The modified electrode can be used for the determination of EP in practical pharmaceutical formulation. 2 The study based on electrochemical pretreatment glassy carbon electrode by “two-step” methodThe ECP GCE gives reproducible surface, improved electron transfer as well as well-defined electrochemical behavior. While different pretreated procedures might result in different structure of GCE surface and could bring different effects to GCE. In this paper, the pretreatment process was divided into four types: “one-step”, “interval”, “two-step”, and “three-step”, the optimization of ECP was conducted by SEM, EIS, and CV. The results suggested that “two-step” of ECP(a potential of +1.75 V was applied to the electrode in 0.1 M PBS for 300 s. The electrode was then cycled between-1.2 V and 1.0 V at a scan rate of 100 mV s-1 for 10 scans) showed the best electrochemical behavior. Under this experimental condition, the electrochemical behaviors of UA and DA at the modified electrode were investigated by CV, and showed that the modified electrode exhibited excellent electrocatalytic activity towards the oxidation of UA and DA. The LOD for UA and DA is 0.086 μM and 0.093 μM(S/N=3), and the calibration curves for UA and DA were obtained over the range of 0.28~600 μM and 0.31~100 μM by CV. 3 Preparation of poly(brilliant cresyl blue)/ECP and its ElectrocatelysisPBCB/ECP/GCE was fabricated via “two-step” ECP and two-step electropolymerization BCB and used for determination U( Ⅵ). Electrochemical measurement indicates that PBCB/ECP/GCE composites modified electrode shows an excellent electrochemical activity of U(Ⅵ) in 1 M H2SO4. Under the optimal condition, the reduction peak currents were proportional to U(Ⅵ) concentration in the range of 0.03 ~300 μg/mL. The limit of detection is calculated as 0.011 μg/mL(0.011 mg/L)(S/N=3), lower that the amount of the National Emission Standards of uranium(0.05 mg/L).Considering that preparing the electrode is very simple, low-cost, sensitivity and stability, the present electrode is believed to be of great utility in making a voltammetric sensor for monitoring U(Ⅵ) in the environment waste.