Electrochemical esterization of 2,4-dinitrophenol on



The effect of potential cycle and sonication time on the thicknesses of nanofilms prepared by diazonium salt reduction

Ayça Avseven, Ali Osman Solak, Zafer Üstündağ

Ankara University, Faculty of Science, Department of Chemistry, Ankara - Turkey

A nitrophenyl modified glassy carbon (NP-GC) surface was prepared by electrochemical reduction in non-aqueous media using cyclic voltammetry. The modifier, 4-nitrobenzenediazonium tetrafluoroborate, was synthesized from 4-nitroaniline as a precursor. Surface voltammogram of the NP-GC surface in 0.01 M HCl showed a well defined irreversible reduction of nitro groups to amine groups indicating the presence of nitrophenyl at the modified surface. The reduction process lead to an aminophenyl modified glassy carbon electrode was denoted as AP-GC. The structures of the modified surfaces are given in the following scheme.

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The electrochemical characterization of NP-GC and AP-GC surfaces was carried out with a 1×10-3 M ferricyanide solution as a redox probe. The main purpose of this work is to measure the film thickness depending on the sonication time and cycle number during the modification process. Film thicknesses were measured using EL X-02C high precision ellipsometer at a laser wave-length of 532 nm and an incidence angle of 70 degree. In the calculation of film thicknesses, fitting was performed for a four-phase model consisting of Graphite/glassy carbon substrate/organic film/air. Refractive indices are 3,0841 for graphite, 1.9000 for glassy carbon substrate, 1.4600 for organic layer and 1.0000 for air, assuming, thicknesses and refractive indices are reasonably correlated for the films. Extinction coefficients are -1.7820 for graphite, -0.8100 for glassy carbon substrate, 0.0000 for organic layer and 0.0000 for air. From data the thicknesses were measured as 5.9 nm and 4.9 nm (in three minute sonication time and four cycle derivatization) for NP-GC and AP-GC, respectively. It was also observed that the sonication of the sufaces after the modification process was necessary to remove the adsorbed species and to gain a compact structure. The sonication time of three minutes was observed to be enough to obtain a compact and stable surfaces.

References

1. A.A. İ-Turan, Z. Üstündağ, A.O. Solak, E. Kılıç, A. Avseven, Electroanalysis 20 (2008) 1665 – 1670

2. A.A. İ-Turan, Z. Üstündağ, A.O. Solak, E. Kılıç, A. Avseven, Thin Solid Films, in pres.

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