Permselective properties of graphene oxide and reduced graphene oxide electrodes

Although graphene-based materials have a number of excellent properties, their permselective properties have not yet been reported. In this work, graphene oxide (GO) and its reduced form (rGO) with the C:O ratios of 2.3:1 and 10.5:1, respectively were coated on glassy carbon electrodes (GCES) and subsequently evaluated by cyclic voltammetry and an adsorption method assuming a Langmuir isotherm behavior. The GO and rGO films allow the permeation of neutral ferrocenemethanol (FcOH) and cationic Ru(NH3)63+ but restrict the permeation of anionic Fe(CN)64- across their layers. The adsorption of FcOH and Ru(NH3)63+ within the GO and rGO films leads to the preconcentration at the electrode surface and subsequently enhances redox currents of FcOH (Fe(II)/Fe(III)) and Ru(NH3)63+ (Ru(III)/Ru(II)). Gibbs free energy changes of FcOH and Ru(NH3)63+ adsorbed within GO and rGO films are −21 to −26 kJ mol−1. The electrooxidation of hydrazine at the modified electrodes was also studied to demonstrate the potential application of the modified electrodes. The linear ranges of hydrazine detection with R2 of 0.999 are 0.004-1.8 mM and 0.02-1.8 mM for rGO/GCE and GO/GCE, respectively. Limits of detection at a signal-to-noise ratio of 3 are 0.4 and 0.9 μM for rGO/GCE and GO/GCE, respectively.