Electrochemical characteristics of glucose oxidase adsorbed at carbon nanotubes modified electrode with ionic liquid as binder

Multiwall carbon nanotubes (CNTs)-modified electrode has been prepared by using ionic liquid (IL) as the binder. The as-prepared CNTs-IL composite modified electrode has good biocompatibility and is a suitable matrix to immobilize biomolecules. Glucose oxidase (GOx), containing flavin adenine dinucleotide as active site, stably adsorbed on modified electrode surface has resulted in the direct electron transfer. The electron transfer rate of 9.08 s(-1) obtained is much higher than that of GOx adsorbed on the CNTs papers (1.7 s(-1)), and the process is more reversible with small redox peak separation of 23 mV This may be due to the synergetic promotion of CNTs and IL to electron transfer of the protein, especially the IL as the binder, showing better electrochemical properties than that of chitosan and Nafion. Furthermore, GOx adsorbed at the modified electrode exhibits good stability and keeps good electrocatalytic activity to glucose with broad linear range up to 20 mM. Besides, the simple preparation procedure and easy renewability make the system a basis to investigate the electron transfer kinetics and biocatalytic performance of GOx and provide a promising platform for the development of biosensors.

In situ electrochemical SERS studies on electrodeposition of aniline on 4-ATP/Au surface

The electrochemical polymerization of 0.01 M aniline in 1 M H2SO4 aqueous solution on roughened Au surface modified with a self-assembled monolayer (SAM) of 4-aminothiophenol (4-ATP) has been investigated by in situ electrochemical surface-enhanced Raman scattering spectroscopy (SERS). The repeat units and possible structures of the electrodeposited polyaniline (PANI) film were proposed; i.e., aniline monomer is coupled in head-to-tail predominately at the C-4 of aniline and amine of 4-ATP, and the thin PANI film is orientated vertically to substrate surface. Simultaneous Raman spectra during potential scanning indicate clearly that the ultrathin PANI film (in initial growth of the film) consists of semiquinone radical cation (IP+), para-disubstituted benzene (IP and IP+) and quinine diimine (NP) while it is oxidized, and without quinine diimine and semiquinone radical cation while reduced. Meanwhile, the results confirm that 4-ATP monolayer shows a strong promotion on the electrodeposition of aniline monomer, and a possible polymerization mechanism was proposed.

ELECTROCHEMICAL REACTION OF CYTOCHROME-C AT GOLD ELECTRODES MODIFIED WITH THIOPHENE CONTAINING ONE FUNCTIONAL-GROUP

The electrochemical reactions of cytochrome c were studied at a thiophene-modified gold electrode. It was demonstrated that thiophene is an effective promoter, although there is only one functional group in the molecule. Based on this result, the mechanis

Influence of Electrostatic Interaction on Fibrinogen Adsorption on Gold Studied by Imaging Ellipsometry Combined with Electrochemical Methods

Imaging ellipsometry was combined with electrochemical methods for studying electrostatic interactions of protein and solid surfaces. The potential of zero charge for gold-coated silicon wafer/solution interfaces wad determined by AC impedance method. The potential of the gold-coated silicon wafer was controlled at the potential of zero charge, and the adsorption of fibrinogen on the potential-controlled and non-controlled surfaces was measured in real time at the same time by imaging ellipsometry The effect of electrostatic interaction was studied by comparing the difference between the potential of controlled adsorption and the Potential of noncontrolled adsorption. It was shown that the rate of fibrinogen adsorption on the potentiostatic surface was faster than that on the nonpotentiostatic surface. The electrostatic influence on fibrinogen adsorption on the gold-coated silicon wafer was weak, so the hydrophobic interaction should be the major affinity.

Electrochemical, spectroscopic and SPM evidence for the controlled formation of self-assembled monolayers and organised multilayers of ferrocenyl alkyl thiols on Au(111)

Organised multilayers were formed from the controlled self-assembly of ferrocene alkyl thiols on Au(111) surfaces. The control was accomplished by increasing the concentration of the thiol solutions used for the assembly. Cyclic voltammetry, ellipsometry, scanning probe microscopy (STM and AFM) and in situ FTIR spectroscopy were used to probe the differences between mono- and multilayers of the same compounds. Electrochemical desorption studies confirmed that the multilayer structure is attached to the surface via one monolayer. The electrochemical behaviour of the multilayers indicated the presence of more than one controlling factor during the oxidation step, whereas the reduction was kinetically controlled which contrasts with the behaviour of monolayers, which exhibit kinetic control for the oxidation and reduction steps. Conventional and imaging ellipsometry confirmed that multilayers with well-defined increments in thickness could be produced. However, STM indicated that at the monolayer stage, the thiols used promote the mobility of Au atoms on the surface. It is very likely that the multilayer structure is held together through hydrogen bonding. To the best of out knowledge, this is the first example of a controlled one-step growth of multilayers of ferrocenyl alkyl thiols using self-assembly techniques.

Electrochemical Impedance Spectroscopy Of Peo Coating On Aluminum Alloy In Nacl Solution

Various Plasma Electrolytic Oxidation (PEO) ceramic coatings were prepared on LY12 aluminum alloy by adjusting the concentration of sodium silicate solution. Optical microscope (OM), XRD and EIS were used to study their morphology, composition and anti corrosion behavior in NaCl solution. Increasing concentration of sodium silicate leads to the increase of the total coating thickness while too high and too low concentration lead to the decrease of inner dense layer. The main composition of PEO coatings prepared in 20, 40 and above 60g/L concentration solution are correspondingly alumina, alumina with mullite, and amorphous phase. The corrosion resistance is determined by the inner dense layer. Increasing the thickness of inner dense layer can improve the anti-corrosion performance. PEO coating's corrosion resistance in acidic, alkaline and neutral NaCl solution is proved and the corrosion mechanism involved is also discussed.

Adsorption of human serum albumin onto gold: a combined electrochemical and ellipsometric study

Human serum albumin adsorption onto gold surfaces was investigated by electrochemical and ellipsometric methods. Albumin adsorption onto gold was confirmed by the change of the open circuit potential of gold and by the ellipsometric parameter variation during albumin immobilization. In both experiments the parameters reached stable values within 10-15 min. The albumin adsorption layer thickness measured with the ellipsometer was about 1.5 nm. The adsorption of albumin Under applied potential was also investigated and it was found that both positive and negative applied potential promote albumin adsorption. Changes in the optical parameters of bare gold and albumin adsorbed onto gold surface under applied potential were investigated with in Situ ellipsometry. The similarity and reversibility of the optical changes showed that adsorbed albumin was stable on the gold surface Under the applied potential range (-200-600 mV). The cyclic voltammograms of K3Fe(CN)(6) on the modified gold surface showed that albumin Could partly block the oxidation and reduction reaction. (C) 2004 Elsevier Inc. All rights reserved.

Applying the Electrochemical Deposition Technology to Construct the Hybrid Devices

Nanowires functionalized by special molecules can be used to as the candidates for biological application in many areas. In this paper, nickel nanowires, which were fabricated by electrochemical deposition and functionalized by biotinylated peptide, were applied to constructing the hybrid device powered by F-1-ATPase motors.

Electrochemical fabrication and electronic behavior of polypyrrole nano-fiber array devices

Electrochemically active Polypyrrole (PPy) nano-fiber array device was fabricated via electrochemical deposition method using aluminum anodic oxide (AAO) membrane as template. After alkaline treatment electrochemically active PPy nano-fiber lost electrochemical activity, and became electrochemically inactive PPy. The electronic properties of PPy nano-fiber array devices were measured by means of a simple method. It was found that for an indium-tin oxide/electrochemically inactive PPy nano-fiber device, the conductivity of nano-fiber increased with the increase of voltage applied on the two terminals of nano-fiber. The electrochemical inactive PPy nano-fiber might be used as a nano-fiber switching diode. Both Au/electrochemically active PPy and Au/electrochemically inactive PPy nano-fiber devices demonstrate rectifying behavior, and might have been used for further application as nano-rectifiers. (c) 2005 Elsevier B.V. All tights reserved.

Growth promotion of vegetative gametophytes of Undaria pinnatifida by blue light

Through an acclimation period of 10 days, compared to white light, the maximal net photosynthetic rates were significantly higher for gametophytes of Undaria pinnatifida cultivated under blue light (400-500 nm), and were lower under red light (600-700 nm). Chlorophyll c and the carotenoid content of gametophytes were similar under blue light and red light but were much lower under white light. The growth rate of female gametophytes under blue light was higher than that under other lights, and the growth rate of male gametophytes showed little variation with respect to blue and white light. Male and female gametophytes were mixed together to form sporophytes under white, blue and red light. After approximately 5 days, 50% gametophytes became fertile under blue and white light, but remained vegetative under red light after 10 days.

Photoluminescence from C+ ion-implanted and electrochemical etched Si layers

The microstructural and optical analysis of Si layers emitting blue luminescence at about 431 nm is reported. These structures have been synthesized by C+ ion implantation and high-temperature annealing in hydrogen atmosphere and electrochemical etching sequentially. With the increasing etching time, the intensity of the blue peak increases at first, decreases then and is substituted by a new red peak at 716 nm at last, which shows characteristics of the emission of porous silicon. C=O compounds are induced during C+ implantation and nanometer silicon with embedded structure is formed during annealing, which contributes to the blue emission. The possible mechanism of photoluminescence is presented. (c) 2005 Elsevier B.V. All rights reserved.

Carrier Depth Profile of Si/SiGe/Si n-p-n HBTStructural Materials Characterized by Electrochemical Capacitance- Voltage Method

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