Preparation Of Graphene, Carbon Nanotubes, Gold Nanoparticles Modified Electrodes And Their Application In Analysis

The synthesis of nanomaterials and their applications in chemical modified electrodes are still the research hotspot of electroanalytical chemistry. In this paper, graphene was fabricated by electrochemical reduction, and gold nanoparticles was prepared by reducing chlorauric acid with lotus leaf extract; the graphene and gold nanoparticles were composited with carbon nanotube and modifed on glassy carbon electrodes respectively. The applications of the modified electrodes in the analysis of pharmaceutical ingredients were studied. The electrocatalytic reaction mechanisms of the drug molecules were discussed. The main contents are as follows.1. Graphene oxide (GO) was prepared and characterazied by transmission electron microscopy (TEM). The composites of GO and multi-wall carbon nanotubes (MWCNTs) was modified on the glassy carbon electrode(GCE) to form GO/MWCNTs/GCE. The electrode was turned to GR/MWCNTs/GCE by electrochemical reduction of GO with cyclic voltammetry. The GR/MWCNTs/GCE was characterazied by electrochemical impedance spectrum (EIS). The electrochemical behavior of clozapine at the modified electrode was studied. The modified electrode showed excellent electro-catalytic activity to clozapine reaction. In0.20mol·L-1Tris-hydrochloric acid (pH=8), the oxidation peak current had a good linear relationship with the concentration of clozapine in the range of0.40～4.0μmol·L-1and6.0-40μmol·L-1.The detection limit of clozapine (S/N=3) was2.5×10-7mol·L-1. The electrocatalytic mechanism of clozapine at GR/MWCNTs/GCE was investigated. It was showed that the reaction of clozapine involved two electron and two proton transfer. The GR/MWCNTs/GCE was applied to the determination of the clozapine in tablets, the recovery rate was88.3%～106%.2. Graphene was fabricated by electrochemical reduction and composited with MWCNTs. The composite was modifed on the bare glassy carbon electrode to form GR/MWCNTs/GCE. The electrochemical behavior of isoproterenol hydrochloride at GR/MWCNTs/GCE was studied. The functionalized electrode had good electrocatalytic property for the reaction of isoproterenol hydrochloride. In0.20mol·L-1citrate-Na2HPO4(pH=7), the oxidation peak current had a good linear relationship to the concentration of isoproterenol hydrochloride in the range of0.40～20μmol·L-1,the detection limit of isoproterenol hydrochloride (S/N=3) was9.4×10-8mol·L-1. The electrocatalytic mechanism of isoproterenol hydrochloride on GR/MWCNTs/GCE was investigated. It was showed that the electrocatalytic about isoproterenol hydrochloride refer to single electron and single proton transfer. The GR/MWCNTs/GCE can determine the isoproterenol hydrochloride in samples, the recovery rate was95.3%～108%.3. The Au/MWCNTs/L-cys composite electrode material was prepared by mixing MWCNTs and L-cysteine (L-cys) with gold nanoparticles which were synthesized by reduction of chlorauric acid with lotus leaf extract, the gold nanoparticles was characterazied by infrared spectroscopy (FT-IR), ultraviolet spectroscopy (UV-Vis), and TEM. The Au/MWCNTs/L-cys composite was dropped onto the GCE to form Au/MWCNTs/L-cys/GCE. The modified electrode was characterazied by EIS. The electrochemical reaction of levodopa at Au/MWCNTs/L-cys/GCE was investigated. In0.20mol·L-1HAc-NaAc (pH=2.6) buffer, Levodopa concentration was linear with the oxidation peak current in the range of0.60～40μmol·L-1and60～120μmol·L-1respectively, and the detection limit was5.2×10-8mol·L-1(S/N=3). The electrocatalytic mechanism of levodopa on Au/MWCNTs/L-cys/GCE was studied; it was showed that the electrocatalytic of levodopa involved both two electron and two proton transfer. The Au/MWCNTs/L-cys/GCE was applied to the determination of levodopa, the recovery rate was91.3 %～102%.4. Gold nanoparticles were synthesized by reducing chlorauric acid with lotus leaf extract. The gold nanoparticles were composited with MWCNTs to form an electrode modified material which was dropped to the surface of a glassy carbon electrode to prepare Au/MWCNTs/GCE. The modified electrode was characterazied by EIS. The electrochemical reaction of rutin at Au/MWCNTs/GCE was investigated. In0.20mol-L"1acetic acid-sodium acetate solution (pH=4), the oxidation peak current had a good linear relationship to the concentration of rutin in the range of0.20～8.0μmol·L-1, the detection limit of rutin (S/N=3) was7.2×10-8mol·L-1. The electrocatalytic mechanism of rutin on Au/MWCNTs/GCE was investigated. It was showed that the reaction of rutin involved two electron and two proton transfer. The Au/MWCNTs/GCE was applied to the determination of rutin, the recovery rate was84.7%-112%.