Exfoliation of graphite rods via pulses of current for graphene synthesis: Sensitive detection of 8-hydroxy-2'-deoxyguanosine.

In this paper we present for the first time a novel method for graphene-based materials synthesis, by exfoliation of graphite rods via pulses of current (pulse duration of 2.5 s; pause between two pulses of 0.8 s). The method has several advantages over the classical one (d.c. current exfoliation) such as the prevention of the electrolyte over-heating, the generation of less amount of graphitic material into the final sample, the increase of the synthesis yield, and the excellent reproducibility in sample quality when the synthesis parameters are preserved. The first material (EGr-A) was obtained in strong acidic solution made by a mixture of H2SO4 and HNO3 (3:1 ratio; 1 M each; pH 1). The second material (EGr-S) was prepared in a salt solution of 0.2 M ammonium sulphate (pH 5). Both materials were morphologically and structurally characterized by SEM, XRD and XPS. The XRD investigation proved that the EGr-A sample contains graphene oxide (GO- 39%) along with few-layer graphene (FLG- 44%) and multi-layer graphene (MLG- 17%). In contrast, the EGr-S sample consists of two-layer graphene (89%) and multi-layer graphene (11%). The performances of two glassy carbon (GC) electrodes modified with the graphene based materials (GC/EGr-A and GC/EGr-S) were investigated towards 8-Hydroxy-2'-deoxyguanosine (8-OHdG) detection and compared with those of bare GC. As expected, the graphene-modified electrodes have a high sensitivity (0.67 A M-1 cm-2 for GC/EGr-S and 0.53 A M-1 cm-2 for GC/EGr-A), a wide linear range (3 × 10-7-10-4 M) and low detection limit (LOD = 9.09 × 10-8 M). In contrast, the bare electrode has higher detection limit (LOD = 3 × 10-7 M) and considerably lower sensitivity towards 8-OHdG (0.22 A M-1 cm-2).