Composite 2D Nanointerfaces for Electrochemical Biosensing: An Experimental and Theoretical Study.

In this study, composite two-dimensional (2D) materials consisting of graphene (Gr) and tungsten disulfide (WS2) were coalesced with gold nanoparticles (AuNPs) through a self-assembly process to boost the conductivity of the resulting graphene-tungsten disulfide-gold nanoparticles (Gr-WS2-AuNPs) nanointerface structure. Structural and morphological characterization of the nanohybrid structure reveals crystalline thin flakelike agglomerates. Electrochemical characterization reveals an excellent electron transfer process for all the modified electrodes at the interface. The Gr/WS2/AuNPs/HRP/GCE modified bioelectrode exhibited a rapid electrobiocatalytic response in detecting H2O2 and a linear response from 0.40 to 23 mM, while 11.07 µA/mM/cm2 is the sensitivity value. This shows that the fabricated Gr/WS2/AuNPs/HRP interface structure is an excellent material for future developments in electrochemical biosensing and bioelectronics applications. The interactions, geometry, and energetic and electronic properties of H2O2 adsorption onto Gr/WS2/Au using the density functional theory (DFT) method have also been investigated along with the Grimme's DFT-D3 dispersion method. Different adsorption modes of the H2O2 molecule onto the Gr/WS2/Au surface were considered. In almost all the cases, the adsorption was found to be energetically favorable and chemisorbed, with energies ranging from -2.198 to -3.782 eV. It was found that the W 5d, S 3p, and Au 6s orbitals play a vital role in the adsorption process. The H2O2 adsorption on Gr/WS2/Au remarkably decreases its work function, thereby increasing the field electron emission from the H2O2 molecule to Gr/WS2/Au.

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.