Preparation of graphene composite paper electrodes doped with different dyes and their amperometric sensor applications

In this study, free-standing and flexible composite paper electrodes were prepared by doping graphene oxide (GO) with different dye molecules; neutral red and safranin from phenazine group, methylene blue and thionine from phenothiazine group, nil blue A and brilliant cresyl blue from phenoxazine group, pyronin Y and rhodamine B from xanthene group, acriflavine from acridine group, thioflavine T from thiazole group. For this purpose, composite paper electrodes were prepared by vacuum filtration of suspensions containing GO and dye through a membrane. Then, GO was chemically reduced to reduced graphene oxide (rGO) in the GO/dye papers structure with HI treatment procedure to prepare rGO/dye papers. Characterization of these composite papers was carried out by using scanning tunneling microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, powder X-ray diffraction spectroscopy, UV-visible absorption spectroscopy, fourier transform infrared spectroscopy, Raman spectroscopy, electrochemical impedans spectroscopy, four point probe conductivity measurements, cyclic voltammetry, and chronoamperometry techniques. All composite papers were tested for electrocatalytic oxidation of nitrite (NO2-) and it was determined that the acriflavine doped graphene paper electrode exhibited the best electrocatalytic effect. The rGO/acriflavine paper exhibited wide linear range and relatively good detection limit as an amperometric nitrite sensor. The most important advantage of this sensor is to have a high flexibility and stability, which makes it suitable for modular applications.