Mu Shaolin

Bioelectrochemical responses of the polyaniline glucose oxidase electrode

Abstract A simple technique is described for constructing a glucose sensor by the entrapment of glucose oxidase in a polyaniline film which was electrochemically deposited on a platinum foil (4 mm × 4 mm). The new glucose sensor has a fast response time (20–40 s) with high storage and operational stability ( > 60 days). The kinetic behavior of enzymes immobilized in polyaniline film is quite similar to that of solublized enzyme. The maximum current response for the enzyme electrode is at pH 5.6, 0.60 V (vs. SCE) and 40° C.

Bioelectrochemical responses of the polyaniline uricase electrode

Abstract The catalytic activity of the polyaniline uricase electrode is very sensitive to uric acid. At a very low concentration of the substrate, such as 1. 2 × 10−6 mol dm−3, uric acid can be determined reliably by using a polyaniline uricase electrode. The response current increases linearly with increasing concentration of uric acid in the region of 1.2 × 10−6 to 1.2 × 10−3 mol dm−3. The reaction rate of the enzyme electrode is affected quite significantly by potential: the response time of the enzyme electrode at 0.35 V (vs. SCE) is about 40 s. The effect of the solution pH on the electrode reaction is rather complicated, the reaction rate increasing with rising temperature. The activation energy of the enzyme-catalyzed reaction is 29.9 kJ/mol.

Bioelectrochemical response of the polyaniline galactose oxidase electrode

Abstract Galactose oxidase has been immobilized in a polyaniline film. The response current of the galactose oxidase electrode is a function of the applied potential and increases as the pH increases from 5.61 to 7.25. The optimum pH of the immobilized galactose oxidase is 7.25. The activation energy of the enzyme-catalysed reaction is 41.8 kJ mol −1 . The response current of the enzyme electrode shows good reproducibility at temperatures below the optimum temperature of 30.4°C and increases as the galactose concentration increases from 0.2 to 6 mmol dm −3 . Thus the polyaniline galactose oxidase electrode can be used to determine galactose concentration.

Photoelectrochemical behaviour of polyaniline affected by potentials and pH of solutions

Abstract The transitions of polyaniline semiconductor from p-type into n-type or from n-type into p-type are caused by the change in potentials, and meanwhile the transition potentials increase with decreasing solution pH. The potentials of photocurrent peaks for n-type polyaniline shift to lower potentials with increasing pH and the potentials for p-type polyaniline are almost unaffected by the pH.

Effects of conducting polymers on immobilized galactose oxidase

Based on the doping principle of conducting polymers, galactose oxidase immobilized in the polyaniline film shows a good bioelectrochemical response to galactose, but no bioelectrochemical response is observed for galactose oxidase immobilized in the polypyrrole film. The results from scanning tunneling microscopy (STM) images, Raman spectra and infrared reflectance spectra reveal that galactose oxidase is doped into the polyaniline film, but is not doped into the polypyrrole film.

The kinetics of activated uricase immobilized on a polypyrrole film

The effect of 15 metal cations and NH+4 on the response current of an inactive polypyrrole uricase electrode has been investigated. Uricase is activated only by Mn2+ among the investigated cations. The response current of the uricase electrode increases with increasing the concentrations of Mn2+ and uric acid. Based on the experimental fact, a mechanism of the activation kinetics of immobilized uricase in the presence of Mn2+ is presented, that is, E + M ⇌ EM, EM + S ⇌ EMS → EM + P, and a rate equation from this model is given. The activation time of the immobilized uricase relates to an applied potential and less than 10s at potentials above 0.375 V.

Bioelectrochemical activation and inhibition of polyaniline glucose oxidase electrode by cations

Abstract The effect of 14 metal cations and NH4+ on the response current of a polyaniline glucose oxidase electrode is investigated in this paper. The immobilized glucose oxidase is only activated by Mn2+ among investigated cations. Based on the experimental results, a mechanism of the activation kinetics of the immobilized glucose oxidase in the presence of Mn2+ is presented, that is E + M ⇋ EM, EM + S ⇋ EMS → EM + P, and a rate equation from this model is given. The inhibition of glucose oxidase by Cu2+ is reversible and non-competitive.

Effect of thiourea on the activity of the polypyrrole uricase electrode and determination of thiourea

Abstract An inactive polypyrrole uricase electrode can be activated by thiourea and reused for determining the concentration of uric acid. We have observed an interesting reaction in which the oxidation of thiourea is catalysed by the uricase immobilized on a polypyrrole film in the absence of uric acid. The reaction rate of the enzyme electrode with respect to thiourea decreases with increasing pH value and increases with increasing applied potential and temperature. The activation energy of the enzyme-catalysed reaction for the thiourea is 42.2 kJ mol −1 . The response current of the enzyme electrode in the absence of uric acid increases linearly with increasing concentration of thiourea in the range below 2.0 mmol dm −3 . Thus the polypyrrole uricase electrode can be used to determine the concentration of thiourea.

Effect of α,α'-bipyridine on activity of the polyaniline uricase electrode

Abstract An inactive polyaniline uricase electrode can be activated by α,α′-bipyridine and reused for determining the concentration of uric acid. The concentration of α,α′-bypridine hardly influences the response current. The reaction rate of the enzyme electrode with respect to uric acid increases with increasing applied potential and temperature. The response current of the enzyme electrode in the presence of α,α′-bipyridine increases linearly with increasing concentration of uric acid in the range below 0.6 mmol dm−3. The optimum pH of the inactive enzyme electrode in the presence of α,α′-bipyridine is 9.35, which is close to the value of 9.25 for the free uricase. The activation energy of the enzyme-catalysed reaction is 32.3 kJ mol−1 in buffer containing α,α′-bipyridine.

The investigation of the electrochemical polymerization of aniline and o-methylaniline by means of the rotating ring-disk electrode

Abstract The ring electrode was set to −0.20 V(vs.SCE). For the first scan, when the potential was over 0.75 V(vs.SCE), the disk current and the ring current rapidly increased. The electroactive species formed at the disk were kinetically sufficiently long-lived to passage from disk to ring, and they reduced at the ring electrode, at which, polyaniline film has been detected, but no poly-o-methylaniline trace was found, The polymerization rates related to the concentrations of aniline, o-methylaniline and acid.