The Exploration Of Biosensor Application Based On The Unique Electronic Properties Of Graphene

Homogeneous aqueous suspensions of graphene have been prepared by chemical reduction of graphene oxide in the presence of poly（3-aminophenylboronic acid）（PABA） in alkale solution. The graphene sheets in thus prepared suspensions can stable several months and can be switch to aggregated state with lower pH values.Graphene/mono-（6-amino-6-deoxy）-β-cyclodextrin multilayer films composed of graphene sheet（GS） and mono-（6-amino-6-deoxy）-β-cyclodextrin（NH₂-β-CD） were fabricated easily by two steps. First, negatively charged graphene oxide（GO） and positively charged mono-（6-amino-6-deoxy）-β-cyclodextrin（NH₂-β-CD） were layer-by-layer（LBL） self-assembled on glassy carbon electrode（GCE） modified with a layer of poly（diallyldimethylammonium chloride）（PDDA）. Then graphene/ mono-（6-amino-6-deoxy）-β-cyclodextrin（GS/NH₂-β-CD） multilayer films were built up by electrochemical reduction of graphene oxide/mo no-（6-amino-6-deoxy）-β-cyclodextrin（GO/NH₂-β-CD）. Combining the high surface area of GS and the active recognition sites on β-cyclodextrin（β-CD）, the GS/NH₂-β-CD multilayer films show excellent electrochemical sensing performance for the detection of dopa mine（DA） with an extraordinary broad linear range from 2.53 to 980.05 μmol·L^-1. This study offers a simple route to the controllable formation of graphene based electrochemical sensor for the detection of DA.Nanocomposite of β-cyclodextrin and graphene sheet（β-CD/GS） was successfully prepared, which exhibited high stability in aqueous solution. When used in electrochemical detection of dopamine, the β-CD/GS modified carbon electrode showed low detection limit, broad linear range, along with good ability to suppress the background current from large excess ascorbic acid. The electrochemical reaction of dopamine on the β-CD/GS showed a mass diffusion controlled process, which was different from the adsorptioncontrolled process on the unmodified graphene sheet.