Highly Sensitive and Selective Dopamine Biosensor Fabricated with Silanized Graphene

A new type of chemically modified graphene, EDTA-modified reduced graphene (EDTA-RG), was synthesized by silanization of graphene with N-(trimethoxysilylpropyl) ethylenediamine triacetic acid (EDTA-silane). It was found that the presence of EDTA on the graphene surface enables the formation of a very stable suspension of EDTA-RG in Nafion/ethanol solution. When deposited onto a glass carbon electrode surface, a very stable, uniform thin film of EDTA-RG-Nafion composite was successfully obtained. The electrochemical behavior of this EDTA-RG-Nafion modified electrode, electrochemical catalysis, ionic selectivity, and biocompatibility, have been investigated using a variety of electrochemical techniques. The ion selectivity was investigated by using a negatively charged probe [Fe(CN)(6)](3-/4-), a positively charged probe, Ru(bpy)(3)(2+), and two biomolecules, dopamine and ascorbic acid. The thin film of EDTA-RG-Nafion composite exhibits high ion selectivity. Performances of EDTA-graphene-Nafion modified electrodes toward dopamine were then evaluated. It was found that the chemical modification process introduces carboxylic groups on the edges of graphene and these functional groups, combined with Nafion, provide an appropriate environment for oxidation of dopamine. The oxidation behavior of dopamine shows excellent reversibility in cyclic voltammetry, which was significantly better than that observed at bare GC, Nafion, and Nafion-graphene coated electrodes. In addition, through the combination of the ionic selectivity of sulfuric from Nafion and EDTA groups in graphene, the EDTA-RG-Nafion film can entirely eliminate the interference from the presence of 1000 times ascorbic acid. The new device is an ideal candidate device for the detection of dopamine.