Abstract
Grafting thin polymer layers on graphene enables coupling target biomolecules to graphene surfaces, especially through amide and aldehyde linkages with carboxylic acid and primary amine derivatives, respectively. However, functionalizing monolayer graphene with thin polymer layers without affecting their exceptional electrical properties remains challenging. Herein, we demonstrate the controlled modification of chemical vapor deposition (CVD) grown single layer graphene with ultrathin polymer 1,5-diaminonaphthalene (DAN) layers using the electropolymerization technique. It is observed that the controlled electropolymerization of DAN monomer offers continuous polymer layers with thickness ranging between 5–25 nm. The surface characteristics of pure and polymer modified graphene was examined. As anticipated, the number of surface amine groups increases with increases in the layer thickness. The effects of polymer thickness on the electron transfer rates were studied in detail and a simple route for the estimation of surface coverage of amine groups was demonstrated using the electrochemical analysis. The implications of grafting ultrathin polymer layers on graphene towards horseradish peroxidase (HRP) enzyme immobilization and enzymatic electrochemical sensing of H2O2 were discussed elaborately.
Highlights
Rapid detection of low concentration of specific analytes in small sample volumes is critical in the early point-of-care diagnosis
The polymer films were deposited from 10 mM DAN in 0.25 M H2 SO4 in a three-electrode system, where, monolayer chemical vapor deposition (CVD) graphene was used as the working electrode, Pt wire as counter electrode and Ag/AgCl served as the reference electrode
The increase in current density evidences the formation of polymeric film on monolayer CVD graphene surface
Summary
Rapid detection of low concentration of specific analytes in small sample volumes is critical in the early point-of-care diagnosis. The graphene field effect transistor (G-FETs) based biosensors are gaining momentum due to its extremely high carrier mobility and capacitance [14,15], where graphene surface is interfaced with various biomolecules and cells. In all these sensors, surface modification is an indispensable step to interface the graphene with biomolecules such as antibodies, cells, enzymes, or single strand DNA probes that can selectively bind/interact to the target biomolecules in solution during biosensor operation
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