Electrochemical Behaviour of HOPG and CVD-Grown Graphene Electrodes Modified with Thick Anthraquinone Films by Diazonium Reduction

Tailoring the performance of electrochemical biosensors based on carbon nanomaterials via aryldiazonium electrografting

Carbon nanomaterials (CNs) offer some of the most valuable properties for electrochemical biosensing applications, such as good electrical conductivity, wide electrochemical stability, high specific surface area, and biocompatibility. Regardless the envisioned sensing application, endowing CNs with specific functions through controlled chemical functionalization is fundamental for promoting the specific binding of the analyte. As a versatile and straightforward method of surface functionalization, aryldiazonium chemistry have been successfully used to accommodate in a stable and reproducible way different functionalities, while the electrochemical route has become the favourite choice since the deposition conditions can be readily controlled and adapted to the substrate. In particular, the modification of CNs by electrochemical reduction of aryl diazonium salts is established as a powerful tool which allows tailoring the chemical and electronic properties of the sensing platform. By outlining the stimulating results disclosed in the last years, this article provides not only a comprehensively review, but also a rational assessment on contribution of aryldiazonium electrografting in developing CNs-based electrochemical biosensors. Furthermore, some of the emerging challenges to be surpassed to effectively implement this methodology for in vivo and point of care analysis are also highlighted.

High-Throughput 2D Heteroatom Graphene Bioelectronic Nanosculpture: A Combined Experimental and Theoretical Study

In this study, chemical vapor deposition-synthesized heteroatom graphene (HGr) bioelectronic interfaces have been developed for ultrafast, all-electronic detection and analysis of molecules by driving them through tiny holes-or atompores-in a thin lattice of the graphene sheet, including the efforts toward facilitating enhanced electrocatalytic and mapping electron transport activities. The presence of chlorine, nitrogen, and oxygen in the crystalline graphitic layers (<7) has been confirmed using Raman spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. We report a swift bioelectrocatalytic response to step-by-step additions of the substrate with the achievement of a steady current within a few seconds. The response limit was 2.07 μM with a dynamic range of sensing from 2.07 μM to 2.97 mM. The electronic properties and adsorption energies of hydroquinone and p-benzophenone molecule adsorption on pristine, O-, N-, and Cl-doped graphene nanosheet surfaces were systematically investigated using first-principles calculations. The results revealed that the adsorption capacity was improved upon doping graphene nanosheets with O, N, and Cl atoms. Hence, Cl-doped graphene nanosheets were shown as a promising adsorbent toward hydroquinone and p-benzophenone detection.

Acetylene-sourced CVD-synthesised catalytically active graphene for electrochemical biosensing

In this study, we have demonstrated the use of chemical vapour deposition (CVD) grown-graphene to develop a highly-ordered graphene-enzyme electrode for electrochemical biosensing. The graphene sheets were deposited on 1.00mm thick copper sheet at 850°C using acetylene (C₂H₂) as carbon source in an argon (Ar) and nitrogen (N₂) atmosphere. An anionic surfactant was used to increase wettability and hydrophilicity of graphene; thereby facilitating the assembly of biomolecules on the electrode surface. Meanwhile, the theoretical calculations confirmed the successful modification of hydrophobic nature of graphene through the anionic surface assembly, which allowed high-ordered immobilisation of glucose oxidase (GOx) on the graphene. The electrochemical sensing activities of the graphene-electrode was explored as a model for bioelectrocatalysis. The bioelectrode exhibited a linear response to glucose concentration ranging from 0.2 to 9.8mM, with sensitivity of 0.087µA/µM/cm² and a detection limit of 0.12µM (S/N=3). This work sets the stage for the use of acetylene-sourced CVD-grown graphene as a fundamental building block in the fabrication of electrochemical biosensors and other bioelectronic devices.

Development and Characterization of Carbon Based Electrodes from Pyrolyzed Paper for Biosensing Applications

This article details the study of electrochemical behavior of new carbon electrodes based on pyrolysis of different paper sources to be used in biosensor applications. The resistivity of the pyrolyzed papers was initially used as screening parameters to select the best three paper samples (imaging card paper, multipurpose printing paper, and 3MM chromatography paper) and assemble working electrodes that were further characterized by a combination of microscopy, electrochemistry, and spectroscopy. Although slight differences in performance were observed, all carbon substrates fabricated from pyrolysis of paper allowed the development of competitive biosensors for uric acid. The presented results demonstrate the potential of these electrodes for sensing applications and highlight the potential advantages of 3MM chromatography paper as a substrate to fabricate electrodes by pyrolysis.

Electrochemical properties of gold and glassy carbon electrodes electrografted with an anthraquinone diazonium compound using the rotating disc electrode method

The RDE method was combined with the electrografting procedure to prepare thick AQ films on Au and glassy carbon electrodes.

Electrochemistry at highly oriented pyrolytic graphite (HOPG): lower limit for the kinetics of outer-sphere redox processes and general implications for electron transfer models

Electron transfer kinetics for outer-sphere redox couples is fast on the basal surface of highly oriented pyrolytic graphite (HOPG).