Functionalized CVD monolayer graphene for label-free impedimetric biosensing

Abstract

Recent advances in large area graphene growth have led to many applications in different areas. In the present study, chemical vapor deposited (CVD) monolayer graphene supported on glass substrate was examined as electrode material for electrochemical biosensing applications. We report a facile strategy for covalent functionalization of CVD monolayer graphene by electrochemical reduction of carboxyphenyl diazonium salt prepared in situ in acidic aqueous solution. The carboxyphenyl-modified graphene is characterized using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM), as well as electrochemical impedance spectroscopy (EIS). We also show that the number of grafted carboxyphenyl groups on the graphene surface can be controlled by the number of cyclic voltammetry (CV) scans used for electrografting. We further present the fabrication and characterization of an immunosensor based on immobilization of ovalbumin antibody on the graphene surface after the activation of the grafted carboxylic groups via EDC/NHS chemistry. The binding between the surface-immobilized antibodies and ovalbumin was then monitored using Faradaic EIS in [Fe(CN) 6 ] 3-/4-solution. The percentage change of charge transfer resistance (R ct ) after binding exhibited a linear dependence for ovalbumin concentrations ranging from 1.0 pg·mL -1 to 100 ng·mL -1 , with a detection limit of 0.9 pg·mL -1 . Our results indicate good sensitivity of the developed functionalized CVD graphene platform, paving the way for using CVD monolayer graphene in a variety of electrochemical biosensing devices.

A Straightforward Approach to Multifunctional Graphene

“…The reactivity of graphene has shown to be strongly correlatedt ot he number of layers constituting each sheet, and it decreases dramatically with the increasing of the number of layers. [2][3][4] For this reason, an extensive varietyo fo rganic reactions has been reported in the literature for monolayered graphene, [4][5][6][7] but not all these reactions can be applied satisfactorily for as cale-upp roduction from bulk graphene. In this context, the reduction of graphite using alkaline metals yielding graphite intercalation compounds (GICs), followedb y the quenching of the intermediatelyg enerated graphenide [8] with electrophiles,i sa na ppropriate alternative to enhance the functionalization degree in bulk graphene dispersions.…”

Ultrasensitive Label‐free Electrochemical Immunosensors for Multiple Cell Surface Biomarkers on Liver Cancer Stem Cells

“…Z W represents the diffusion of the [Fe(CN) 6 ] 3−/4− redox couple from the bulk of the solution to the electrode interface and the CPE corresponds to the electrical double layer capacitance. In general, the charge transfer resistance (which corresponds to the diameter of the semicircle of the Nyquist plot), is the most changeable parameter in the circuit upon surface modification and therefore, it is the most suitable element to monitor the immobilization steps as well as the binding events . As shown in Figure B, the attachment of cysteamine to the Au electrode led to a decrease in the semicircle and only a straight line was seen indicating the decrease of the R ct from the bare gold electrode.…”

Electrochemical Sensing of Ovalbumin Based on the Interaction between Lysozyme Origin/Tyrosine‐rich Peptides Modified on Magnetic Beads and Oligothreonine/Ovalbumin‐origin Peptide

“…The calibration curve of OVA for that method ranged from 2.2×10 −14 to 1.1×10 −8 M with a detection limit of 1.8×10 −14 M. In another method, an electrochemical immunosensor for the monitoring of OVA used a screen‐printed platinum electrode and magnetic beads . With that method, the magnetic beads immobilized with anti‐OVA immunoglobulin G recognized OVA, the secondary anti‐OVA antibodies with horseradish peroxidase were combined with the target, and the sensing of OVA was achieved via electron transfer between thionine and a substrate that produced a calibration curve for OVA ranging from 1.1×10 −8 M to 2.2×10 −7 M with a detection limit of 5×10 −9 M. Electrochemical OVA biosensing has also used an electrode with a chemical vapor deposited monolayer of graphene where OVA was monitored using Faradaic EIS in [Fe (CN) 6 ] 3–−/4− . The response for OVA concentrations was linear in that system and ranged from 2.2×10 −14 to 2.2×10 −12 M, with a detection limit of 2.0×10 −14 M. Although the dynamic range of our procedure was one order, a concentration of 10 −14 –10 −13 M of OVA was detected without the use of antibodies and enzymes.…”