Preparation and application of metal oxide and metal nano particles modified carbon based composite electrodes for simultaneous determination of adenine and guanine

In recent years, sensor studies that provide information on physic, chemistry and biology were increased with the progress on nanoscience and nanotechnology. The insufficient behaviour of conventional electrodes in some applications, cause the necessity of different active surfaces which were more selective and catalytically active towards analytes. The combination of metal nano particles with conductive polymers and carbon nanotubes which have high conductivity and wide active surface area was used as important new electrode materials. In the first part of this thesis which consisted of two different sections, metal nano particles modified acid treated carbon nanotube covered electrodes were prepared and their effect on adenine and guanine oxidation was investigated. The best catalytic activity towards adenine and guanine oxidation was obtained for coexistence of Cu and CeO2 nanoparticles on the carbon nanotube surface. The peak currents of A and G at metal nano particles modified carbon nanotube electrodes were found to be 15-20 times higher than bare GCE.The peak current of adenine on Cu-CeO2/MWCNT/GCE was linearity range from 1x10-7 to 8x10-6 mol L-1 with LOD value of 6.2x10-8 mol L-1 (S/N=3). The peak current of guanine on Cu-CeO2/MWCNT/GCE was linearity range from 2x10-7 to 6x10-6 mol L-1 with LOD values of 1.28x10-7 mol L-1 (S/N=3). In another part of this thesis, copper(II)hexacyanoferrate and graphene oxide modified electrodes were utilized for investigation of alone and simultaneous electrochemical behavior of adenine and guanine. It was observed that increasing catalytic activity for modified electrodes comparing bare GCE. The alone and simultaneous determination of adenine and guanine were studied by DPV. Under the optimal conditions, the oxidation peak currents were linearly regarding adenine and guanine concentrations in the range from 6x10-7 to 6x10-6 M and from 4x10-7 to 6x10-6 M , respectively. LOD values were 2x10-7 M for A and 1.33x10-7 M for G. All graphene oxide and multi-walled carbon nanotube modified electrode surfaces and their covered metal nano particles forms were characterized by Energy Dispersive X-Ray Spectroscopy (EDX), X-Ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM) and Electrochemical Impedance Spectroscopy (EIS).