| Chemically modified electrodes(CMEs) and the corresponding electrochemicalsensing techniques are one of the most active research areas in modern electroanalyticalchemistry and electrochemistry. Because of the unique performance and structure, graphenedraw great interest and attention of investigators in many different fields since2004. As a newtype of carbon nanomaterials, graphene has separate flat structure of two-dimensional orderedhoneycomb, its thickness is only a two-dimensional crystal of an atom. Graphene has a largerspecific surface area and strong electrical conductivity, in addition to it, graphene showsexcellent thermodynamic and mechanical properties, which has been widely concerned in theelectroanalytical chemistry field. This paper mainly prepared graphene through improvedHummer method, and has carried on the characterization and analysis. The prepared grapheneand its composites were used to modify carbon paste electrode, and their electrochemicalresponses to the part of the ion and drug were studied, the main contents are summarized asfollows:(1) Graphene has been prepared by modified Hummers method and the oxidation-reduction process, the obtained sample are characterized by Raman spectroscopy, XRD andScanning electron microscope. It is found that the D (near1343.01cm-1) peak appears inRaman spectroscopy, which indicates the C=C is ruptured during the oxidation reaction. Thevery strong200peak at11.12°shows that crystal structure is changed and graphene oxide isgenerated. After restored, the disappearance of the characteristic peak at11.12°certified thegraphene is prepared. Besides, results of Raman spectroscopy and scanning electronmicroscope(SEM) characterization also proved that.(2) With the prepared graphene modified carbon paste electrode, the electrochemical responses of the modified electrode to Cu2+were studied by cyclic voltammetry (CV). Asshown by the experimental results, when the proportions of graphite and graphene is8:1andthe pH of B-R buffer solution is3.53, a better shape characteristic absorption peak isobserved at about0.136V using cyclic voltammetry at100mV·s-1scanning speed and-1.2～1.2V scanning range; There is a linear relationship between the peak current and theCu2+concentration in the range of5.0×10-8～1.0×10-5mol·L-1, the linear regression equationis ipa=-2.0638-0.0839C(Cu2+), and the correlation coefficient R=0.9989, the detection limitreached4.6×10-8mol·L-1.(3) RGO/DB18C6modified electrode was prepared successfully. A new electro-chemistry system of Pb2+and NO2-detection were developed. It was found that RGO/DB18C6modified electrode has the obvious catalysis to redox process of Pb2+and NO2-. Andthe detection limit reached8.8×10-9mol·L-1and3.4×10-8mol·L-1respectively. Under theoptimum conditions, there is a linear relationship between the peak current and the Pb2+concentration in the range of1.0×10-8～1.0×10-5mol·L-1, the linear regression equation isipc=2.0955+0.4377C(Pb2+), the correlation coefficient R=0.9973. However, there is a linearrelationship between the peak current and the NO2-concentration in the range of7.0×10-7～1.0×10-4mol·L-1, the linear regression equation is ipc=0.5132+0.0192C(NO2-), and thecorrelation coefficient R=0.9987. The modified electrode is used in the detection of actualsamples, the satisfactory result is obtained.(4) The prepared RGO/DB18C6modified electrode has strong electrochemistryresponse to Vc, a high selectivity and sensitivity method to detect Vc is built. Aftergathering25s in Vc solution, modified electrode scan solution by cyclic voltammetry at-1.2～1.2V scanning range with different scanning speed, the results showed that there is alinear relationship between the redox peak current and υ1/2, the linear regression equation is ipa=-10.8876υ1/2-1.0314, ipc=14.6499υ1/2+0.8565respectively, and the correlation coefficient isRpa=0.9942, Rpc=0.9955respectively, it could be used in the practical detection. |
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