Heterogeneous Electron Transfer Properties Research Articles

Electrochemical determination of hydrazine using a ZrO2 nanoparticles-modified carbon paste electrode.

In the present paper, the use of a carbon paste electrode modified by 3-(4'-amino-3'-hydroxy-biphenyl-4-yl)-acrylic acid (3,4'AA) and ZrO2 nanoparticles prepared by a simple and rapid method was described. The heterogeneous electron transfer properties of (3,4'AA) coupled to ZrO2 nanoparticles at the carbon paste electrode were investigated using cyclic voltammetry, chronoamperometry, and square wave voltammetry in aqueous buffer solutions. Under the optimized conditions, the square wave voltammetric peak currents of hydrazine increased linearly with hydrazine concentrations in the range of 2.5 × 10(-8) to 5.0 × 10(-5)M, and detection limit of 14nM was obtained for hydrazine. Finally, this modified electrode was used for the determination of hydrazine in water samples, using standard addition method.

Engineered 2D Materials for Efficient Biosensors

ABSTRACTThe emergence of 2-dimensional (2D) materials could herald numerous advanced scientific methodologies for both fundamental and applied research. These ultrathin materials can be functionalized and, thus, have the potential to make new devices and sensors that are both highly efficient and sensitive. In addition to being mechanically robust, the 2D materials can be engineered to provide sensor architectures that further increase their inherent high surface area by creating 3D geometries using layer by layer assembly to make stacked devices that could potentially be transparent. The increased sensor surface area would deliver increased signal-to-noise and sensitivity. Here highly sensitive and selective electrochemical detection of bio-analytes using some of engineered 2D materials such as graphene nano-ribbons, fluorinated graphene, and molybdenum disulfide is presented. It is found that surface moieties, defects and surface charges in these ultra-thin layers result in enhanced electron transfer kinetics between the electrodes and biomolecules. This in turn results in an oxidation or reduction of biomolecules with a high peak current, indicating the possible uses of 2D materials for various point-of-care devices. A novel stable 3D electrode geometry has been found to have enhanced heterogeneous electron transfer properties compared to 2D electrodes and provides evidence that electrode geometry and surface area could significantly impact the performance of biosensors.

Heteroatom modified graphenes: electronic and electrochemical applications

Graphene exhibits zero band gap, very small electrical resistivity, fast heat dissipation, and fast heterogeneous electron transfer properties. These features, coupled with affordable preparation cost and high surface area, predetermine graphene materials for application in electronic and electrochemical devices. Doping graphene with electron-withdrawing or -donating heteroatoms leads to tailoring of graphene electronic and electrochemical properties. Here, we discuss doping of graphene-based materials with main group heteroatoms (s and p blocks). We will also discuss the application of such doped graphenes in electronic, sensing, and energy storage/generation devices.

Electrochemistry at CVD Grown Multilayer Graphene Transferred onto Flexible Substrates

The application of graphene and graphene-related materials for the fabrication of improved electrochemical devices is a very active research field. Because of the need of bulk quantities of graphene for such applications, chemical vapor deposition (CVD) represents one of the most promising fabrication processes to obtain large area and good quality graphene films with controlled thickness. Here we investigated the electrochemical properties of a multilayer graphene film grown by CVD and transferred to an insulating flexible poly(ethylene terephthalate) (PET) sheet. After a careful characterization with optical microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy of the transferred graphene film, we tested its heterogeneous electron transfer properties with Fe(CN)63–/4– and Ru(NH3)62+/3+ redox mediators and its sensing capability toward dopamine (DA), ascorbic acid (AA), and the reduced form of β-nicotinamide adenine dinucleotide (NADH) as biological relevant molecules. The CVD grown multil...

Effect of peptide orientation on electron transfer

We have developed a methodology for the in situ derivatisation of histidine residues in self-assembled monolayers of peptides with redox-active groups, and have shown by electrochemical methods that the average dipole of peptide films on gold affects the heterogeneous electron transfer properties.

Self-assembly and heterogeneous electron transfer properties of metallo-octacarboxyphthalocyanine complexes on gold electrode

Electrochemical properties of redox-active self-assembled molecular films of novel metallo-octacarboxyphthalocyanine (MOCPc, M = Fe, Co and Mn) complexes integrated with cysteamine (Cys) monolayer on gold electrodes via amide bonds were investigated. X-Ray photoelectron spectroscopy confirmed the appearance of the various elements in their expected chemical environment upon immobilization of these species. The heterogeneous electron transfer properties of the Au-Cys-MOCPc molecular films using an outer-sphere ([Fe(CN)(6)](4-)/[Fe(CN)(6)](3-)) redox probe were studied using cyclic voltammetry and electrochemical impedance spectroscopy. The electron transfer rate constant (k(app)) depends markedly on the central metal of the metallophthalocyanine cores (k(app): Co > Mn > Fe). A strong pH dependence of the electron transport of the Au-Cys-MOCPc molecular films was found. The surface pK(a) values of the MOCPc complexes were essentially the same (ca. 7.5). The differences in the electron transports and ionization constants are discussed. The electrodes are sensitive to the electrooxidation of epinephrine in physiological pH conditions, peak potential (E(p)/V vs. Ag|AgCl, saturated KCl) decreasing as FeOCPc (0.20 V) < MnOCPc (0.26 V) < CoOCPc (0.34 V).