A. Kaisheva

Electrochemical gas biosensor for phenol

A gas biosensor for vapors of phenolic compounds, comprising an enzyme/gas-diffusion electrode with tyrosinase enzyme is investigated. The transient amperometric signal and the calibration curves of this gas biosensor are studied in the presence of phenol, p-cresol and 4-chlorphenol vapors. It is shown that phenol vapor concentrations in the ppb range are detectable with this type of gas biosensor. The stable steady-state performance of the biosensor allow the measurement of the electrochemical impedance of the system in a broad frequency range (50 kHz to 1 mHz).

Transient response of electrochemical biosensors with asymmetrical sandwich membranes

Abstract A mathematical model of a sandwich membrane biosensor operating in the diffusion-limited regime is proposed. The enzyme (oxidase) is immobilized between two diffusion membranes with different thicknesses. The electrochemically active product of the enzymatic reaction (H2O2) is detected on a catalytic electrode. The exact transient solution of the model is obtained under the assumptions of diffusion-limited enzymatic and electrochemical reactions, a stepwise increase of the substrate concentration (from 0 to CG°) and zero concentration of the electrochemically active product (H2O2) in the bulk solution. The thickness of the enzyme layer in the sandwich is assumed to be negligibly small in comparison with that of the diffusionn membranes. The numerical values of the transient concentration distribution C(x, t), of the transient current i(t) and its time derivative di(t)/dt are computed and presented in dimensionless form for different sets of parameters of the model. The influence of the enzyme layer position in the sandwich membrane and of the ratio of the effective diffusion coefficients of the substrate and the electrochemically active product on the transient behaviour of the sensor is discussed. The model gives some hints for the design of amperometric biosensors.

AMPEROMETRIC ENZYME/GAS-DIFFUSION ELECTRODES

Abstract An amperometric enzyme/gas-diffusion electrode is developed which combines a porous air-breathing gas-diffusion electrode with an enzyme immobilized on its catalytic layer. The behaviour of glucose oxidase/gas-diffusion and lactate oxidase/gas-diffusion electrodes are investigated when oxygen, needed for the enzymatic reaction, is supplied in the gas phase through the porous structure of the gas-diffusion electrode. This electrode can be used as a system model for the investigation of the influence of oxygen on the performance both of the peroxide or mediated enzyme electrodes in the effort to develop oxygen-independent biosensors.

Metallocene-mediated amperometric biosensors for one-shot glucose determination

Abstract Amperometric biosensors for the determination of glucose based on carbon black screen-printed on ceramics are described. The mediators, nickelocene, ferrocene and their derivatives, are used for the conjunction of glucose oxidase-catalysed oxidation of glucose and electrochemical reaction at the applied potential. It is shown that the nickelocene-mediated glucose oxidase electrode exhibits a similar behaviour to that mediated with ferrocene. However, the quasi-redox potential of nickelocene/nickelocenium cation, which is by 0.3 V more negative than that of any of the investigated ferrocene derivatives, significantly lowers the operating potential of the biosensor to ≈0.00 V versus an Ag/AgCl electrode.

Enzyme Electrodes For Determination Of Phenol Concentration

Enzyme electrode for the determination of phenol concentration is investigated comprising a new type of porous hydrophobic carbon electrode (made from acetylene black treated with PTFE by a special technology) on which enzyme tyrosinase is immobilized. Oxygen needed for the enzymatic reaction can be transported to the immobilized enzyme in gas phase from the air through this carbon electrode. It is shown that the fast O/sub 2/ supply in gas phase results in an increase of the amperometric signal of the phenol electrode and in enlargement of the linear part of its calibration curve.

APPLICATION OF CARBON-BASED MATERIALS IN METAL-AIR BATTERIES: RESEARCH, DEVELOPMENT, COMMERSIALIZATION

Metal-air cells have been developed, comprising a carbon air gasdiffusion electrode providing low polarization and stable long-term operation and metal anode with low self-discharge, operational at high current densities. The mechanism of gas-transport in the hydrophobic gas layer of the air electrode is investigated. Various carbon-based catalysts for the electrochemical oxygen reduction were tested. Methods for diagnostic of the activity and transport properties of the catalysts are proposed. A range of metal air cells developed in this laboratory is presented.

ENZYME ELECTRODES WITH PTFE MODIFIED CARBON BLACK MEDIATOR MATRIX AND THEIR APPLICATION IN GLUCOSE BIOSENSORS

Publisher Summary This chapter focuses on enzyme electrodes with PTFE modified carbon black mediator matrix and their application in glucose biosensors. PTFE modified carbon blacks are prepared as a powder material by a special technology that allows the use of different carbon blacks and a controlled carbon black/PTFE ratio. This material possesses an electronic conductivity combined with hydrophobic surface properties, and enzymes can be immobilized on it by adsorption. Mediators are mixed with the PTFE modified carbon blacks to form a powdered composite material. Glucose oxidase electrode is prepared by coating of the porous matrix from composite material with enzyme solution and further evaporation of the solvent. The use of a PTFE modified carbon black-mediator matrix coated with enzyme allows standardizing the production of biosensors with reproducible performance.