PROMOTER EFFECT OF POLY(4-VINYLPYRIDINE) ON THE DIRECT ELECTRON-TRANSFER BETWEEN CYTOCHROME-C AND GOLD ELECTRODE

The electrochemistry of cytochrome c was studied at the PVP-modified gold electrode. It was found that the promoter effect is related to the amount of PVP at the gold electrode. From our results, it can be seen that the nitrogen element in the polymer is important for accelerating the electron transfer of cytochrome c.

Carbon nanotube/gold nanoparticles/polyethylenimine-functionalized ionic liquid thin film composites for glucose biosensing

A novel glucose biosensor based on immobilization of glucose oxidase (GOD) in thin films of polyethylenimine-functionalized ionic liquid (PFIL), containing a mixture of carbon nanotubes (CNT) and gold nanoparticles (AuNPs) and deposited on glassy carbon electrodes, was developed. Direct electrochemistry of glucose oxidase in the film was observed, with linear glucose response up to 12 mM. The PFIL-stabilized gold nanoparticles had a diameter of 2.4 +/- 0.8 nm and exhibited favorable stability (stored even over one month with invisible change in UV-vis spectroscopic measurements).

Highly ordered mesoporous carbons-based glucose/O-2 biofuel cell

This study demonstrates a novel compartment-less glucose/O-2 biofuel cell (BFC) based on highly ordered mesoporous carbons (OMCs) with three-dimensionally (3D) interconnected and ordered pore structures. OMCs are used as supports for both stably confining the electrocatalyst (i.e., meldola's blue, MDB) for NADH oxidation and the anodic biocatalyst (i.e., NAD(+)-dependent glucose dehydrogenase, GDH) for glucose oxidation, and for facilitating direct electrochemistry of the cathodic biocatalyst (i.e., laccase, LAC) for O-2 electroreduction. In 0.10 M pH 6.0 PBS containing 20 mM NAD(+) and 60 mM glucose under the air-saturated atmosphere, the open circuit voltage (0.82 V) and the maximum power output (38.7 mu W cm(-2) (at 0.54V)) of the assembled compartment-less OMCs-based BFC are both higher than those of carbon nanotubes (CNTs)-based BFC (0.75 V and 2.1 mu W cm(-2) (at 0.46 V)).

Direct electron transfer between cytochrome c and a gold nanoparticles modified electrode

Quasi-reversible and direct electrochemistry of cytochrome c (cyt. c) has been obtained at a novel electrochemical interface constructed by self-assembling gold nanoparticles (GNPs) onto a three-dimensional silica gel network, without polishing or any modification of the surface. A cleaned gold electrode was first immersed in a hydrolyzed sol of the precursor (3-mercaptopropyl)-trimethoxysilane to assemble three-dimensional silica gel, then the GNPs were chemisorbed onto the thiol groups of the sol-gel network and modified the kinetic barrier of this self-assembled silicate film. Cyclic voltammetry and AC impendance spectroscopy were performed to evaluate electrochemical properties of the as prepared interface. These nanoparticle inhibits the adsorption of cyt. c onto bare electrode and acts as a bridge of electron transfer between protein and electrode.

Electrochemiluminescence sensor using tris(2,2 '-bipyridyl)ruthenium(II) immobilized in Eastman-AQ55D-silica composite thin-films

An electrochemiluminescence (ECL) sensor with good long-term stability and fast response time has been developed. The sensor was based on the immobilization of tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)(3)(2+)) into the Eastman-AQ55D-silica composite thin films on a glassy carbon electrode. The ECL and electrochemistry of Ru(bpy)(3)(2+) immobilized in the composite thin films have been investigated, and the modified electrode was used for the ECL detection of oxalate, tripropylamine (TPA) and chlorpromazine (CPZ) in a flow injection analysis system and showed high sensitivity. Because of the strong electrostatic interaction and low hydrophobicity of Eastman-AQ55D, the sensor showed no loss of response over 2 months of dry storage. In use, the electrode showed only a 5% decrease in response over 100 potential cycles. The detection limit was 1 mumol l(-1) for oxalate and 0.1 mumol l(-1) for both TPA and CPZ (S/N = 3), respectively. The linear range extended from 50 mumol l(-1) to 5 mmol l(-1) for oxalate, from 20 mumol l(-1) to 1 mmol l(-1) for TPA, and from 1 mumol l(-1) to 200 mumol l(-1) for CPZ.

Direct electron transfer between hemoglobin and a glassy carbon electrode facilitated by lipid-protected gold nanoparticles

We synthesized a kind of gold nanoparticle protected by a synthetic lipid (didodecyidimethylammonium bromide, DDAB). With the help of these gold nanoparticles, hemoglobin can exhibit a direct electron transfer (DET) reaction. The formal potential locates at -169 mV vs. Ag/AgCl. Spectral data indicated the hemoglobin on the electrode was not denatured. The lipid-protected gold nanoparticles were very stable (for at least 8 months). Their average diameter is 6.42 nm. It is the first time to use monolayer-protected nanoparticles to realize the direct electrochemistry of protein.

Electrochemistry and spectroscopy study on the interaction of microperoxidase-11 with lipid membrane

The interaction of microperoxidase-11 (MP11) with cationic lipid vesicles of didodecyldimethylammonium bromide (DDAB) induces an alpha -helical conformation from random coil conformations in solution and this change then makes heme macrocycle more distorted. DDAB-induced MP11 conformations were investigated by cyclic votammetry (CV), circular dichroism (CD) and UV-vis spectrometry. All results indicate that the binding of MP11 in solution to DDAB vesicles and the ordered structure formation are driven by mostly electrostatic interaction between negatively charged residues in the undecapeptide and positively charged lipid headgroups on the membrane surface. Upon binding to DDAB, its half-peak potential was also changed. The mechanism of the interaction between MP11 and DDAB was also discussed. (C) 2001 Elsevier Science B.V. All rights reserved.

STUDIES ON ELECTROGENERATION, INSITU ELECTROCHEMISTRY AND SPECTROELECTROCHEMISTRY OF ALKYL COBALT PORPHYRIN

Methyl-, ethyl-, propyl- and n-butyl cobalt porphyrins were electrochemically synthesized and studied byIn-situ cyclic voltammetry and UV-Visible spectro-el ectrochemistry. Rate constants for the alkylations were determined. It was found that the four alkyl saturated tetraphenylchlorin cobalt complexes were formed after electrochemical reduction of the alkyl cobalt porphyrins.

The synthesis and characterization of novel liquid crystalline, meso-tetra[4-(3,4,5-trialkoxybenzoate)phenyl]porphyrins

Five, novel, meso-tetra[4-(3,4,5-trialkoxybenzoate)phenyl]porphyrins and their metal complexes were synthesized and their molecular structures were confirmed by H-1 NMR, FTIR spectroscopy and elemental analysis. Mesomorphic studies using DSC, polarizing optical microscope and X-ray diffraction revealed that all compounds exhibited thermotropic columnar mesophases over a wide mesophase temperature range and low liquid crystalline-crystal line transition temperature. (c) 2007 Elsevier Ltd. All rights reserved

Direct Electrochemistry and Electrocatalysis of Hemoglobin in Lipid Film Incorporated with Room-Temperature Ionic Liquid

A facile phospholipid/room-temperature ionic liquid (RTIL) composite material based on dimyristoylphosphatidylcholine (DMPC) and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6) was exploited as a new matrix for immobilizing protein. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were adopted to characterize this composite film. Hemoglobin (Hb) was chosen as a model protein to investigate the composite system. UV-vis absorbance spectra showed that Hb still maintained its heme crevice integrity in this composite film.

The direct electrochemistry behavior of Cyt c on the modified glassy carbon electrode by SBA-15 with a high-redox potential

It is discovered that SBA-15 (santa barbara amorphous) can provide the favorable microenvironments and optimal direct electron-transfer tunnels (DETT) of immobilizing cytochrome c (Cyt c) by the preferred orientation on it. A high-redox potential (254 mV vs. Ag/AgCl) was obtained on glassy carbon (GC) electrode modified by immobilizing Cyt c on rod-like SBA-15. With ultraviolet-visible (UV-vis), circular dichroism (CD), FTIR and cyclic voltammetry, it was demonstrated that immobilization made Cyt c exhibits stable and ideal electrochemical characteristics while the biological activity of immobilized Cyt c is retained as usual.

Type I collagen-mediated synthesis of noble metallic nanoparticles networks and the applications in Surface-Enhanced Raman Scattering and electrochemistry

In this paper, we demonstrated an effective enviromentally friendly synthesis route to prepare noble metallic (Au, Ag, Pt and Pd) nanoparticles (NPs) networks mediated by type I collagen in the absence of any seeds or surfactants. In the reactions, type I collagen served as stabilizing agent and assembly template for the synthesized metallic NPs. The hydrophobic interaction between collagen and mica interface as well as the hydrogen bonds between inter- and intra-collagen molecules play important roles in the formation of collagen-metallic NPs networks. The noble metallic NPs networks have many advantages in the applications of Surface-Enhanced Raman Scattering (SERS) and electrochemistry detection. Typically, the as-prepared Ag NPs networks reveal great Raman enhancement activity for 4-ATP, and can even be used to detect low concentration of DNA base, adenine.