Graphene-based materials produced by graphite electrochemical exfoliation in acidic solutions: Application to Sunset Yellow voltammetric detection

Abstract

Two graphene-based materials were prepared by exfoliation of graphite rod with pulses of current. The first material (denoted EGr-1) was exfoliated in a mixture of sulphuric and nitric acid (3:1 ratio; 0.5 M each; pH 1) giving a material composed of graphene (40% few-layer; 32% multi-layer) and graphene oxide (28%). The second material (denoted EGr-2) was prepared by exfoliation of the graphite rod in 0.05 M boric acid (pH 5.1) in which 0.05 M NaCl was added to increase the electrolyte conductivity. After preparation, the materials were used for the modification of two glassy carbon (GC) electrodes, denoted GC/EGr-1 and GC/EGr-2, respectively. The performances of each electrode toward Sunset Yellow (SY) detection were tested in laboratory solutions (pH 6 PBS) containing increasing concentrations of SY (3 × 10−7–1 × 10−4 M). It is important to emphasize that the sensitivities, linear ranges and the limits of detection of the two electrodes were different. Hence, in the case of the electrode covered with graphene prepared in strong acidic solution (GC/EGr-1) the sensitivity was 0.017 A·M−1, the linear range between 6 × 10−6 and 1 × 10−4 M, the LOD was 1.8 × 10−6 M. In contrast, the electrode covered with the material prepared in weak acidic solution (GC/EGr-2) has higher sensitivity (0.021 A·M−1) wider linear range (1 × 10−6–1 × 10−4 M) and lower LOD (3 × 10−7 M).