Electrochemical functionalization strategy for chemical vapor deposited graphene on silicon substrates: grafting, electronic properties and biosensing

Abstract

Herein, we present an electrochemical functionalization strategy for high quality single-layer and multilayer chemical vapor deposited (CVD) graphene directly on a Si/SiO 2 chip facilitating electronic interfacing. This method avoids oxidation and tearing of graphene basal planes. We demonstrate effective functionalization by D-(+)-biotin (Bio), 4-(phenyldiazenyl)-aniline (Dz), and gallic acid (Gall) using cyclic voltammetry. Raman spectroscopy and XPS are used to demonstrate effective functionalization. In order to evaluate the effect of the electrochemical functionalization on graphene properties, DC electrical conductivity, XPS, mobility, and carrier density analysis are presented. We show that this functionalization strategy does not degrade graphene mobility (10 3 cm 2 V −1 s −1 ). After functionalization we observe a rise in Fermi level of ∼0.06 eV. In addition, we prove sensing capabilities with a CVD graphene monolayer on the biotin/avidin system by electrical resistance measurements and electrochemical impedance spectroscopy reaching a detection of 2.5 ng ml −1 . This paper demonstrates an effective strategy to functionalize high quality CVD graphene on a chip compatible with an electronic interface readout.

Direct Electrochemical Functionalization of Graphene Grown on Cu Including the Reaction Rate Dependence on the Cu Facet Type

“…Covalent functionalization of graphene allows for manipulation of its electronic structure such as the Fermi level and band gap opening − to initiate polymerization on the basal plane of graphene − or to immobilize catalysts or biomolecules. − Many strategies for the covalent functionalization of graphene have been reported, including diazo-coupling with highly reactive radical intermediates of diazonium salts, − photochemical reactions on defects of the graphene lattice with peroxide compounds activated by intense laser irradiation, ,− cycloaddition through the Diels–Alder reaction, , hydrogenation and halogenation, − reduction of graphene with organic halides by a reductive metal alloy catalyst to produce a negatively charged graphene called graphenide, − and electrochemical modification using diaryliodonium. − …”