Dr. Oğuz Bayındır

FIG. 1. Schematic illustration of the preparation procedure of Gr/MB composite modified Au(111) electrode.

Graphene (Gr)/methylene blue (MB) composites were successfully prepared and amperometric detection of nicotinamide adenine dinucleotide (NADH) was studied on the Gr/MB composite thin films modified Au(111) electrode. Gr sheets were fabricated by using two-step electrochemical approaches: intercalation of sodium dodecyl sulfate (SDS) into graphite working electrode by electrooxidation and exfoliation of SDS-intercalated graphite electrode by electrochemical reduction to obtain Gr/SDS suspension. In order to prepare Gr/MB composite structure, first SDS was removed from Gr/SDS suspension and then MB was added into Gr suspension. Gr/MB dispersion was ultrasonicated, vacuum-filtered through a membrane, and then re-dispersed into water. Gr/MB nanocomposite was supported on Au(111) substrates by drop-casting of this composite dispersion. Characterization of Gr/MB composites was carried out by using scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS), uV-Visible absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), and cyclic voltammetry techniques. Gr-MB/Au(111) electrode, having an excellent electrocatalytic activity, was used for amperometric determination of NADH. The oxidation current density was linearly proportional to NADH concentration in the range between 1.0 to 264 ıM . The sensitivity of the sensor was calculated as 0.316 mA mM-1 cm-2 with a detection limit of 0.3 mM at a signal-to-noise ratio of 3.0.

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