Investigation of Electrochemical Properties of Carbon Nanofibers Prepared by CCVD Method

Carbon nanofibers, with diameters between 80 and 290 nm and specific area of 242 m²g^?1, have been prepared by the catalytic chemical vapor deposition method. After preparation, the powder was mixed with silicon oil in order to create a paste electrode. The electrochemical behavior of this type of electrode was investigated by cyclic voltammetry, using a solution of 10^?3 M ferrocenecarboxylic acid as mediator. The redox process is quasi-reversible, and it involves the transfer of electrons between Fe(II) and Fe(III).

The same mediator was used for the construction of a second-generation glucose biosensor. The mediator was co-immobilized with the enzyme in the carbon nanofibers paste. The sensor linearly responded to glucose, in the concentration range of 1.7 to 7 mM. A time of around 30 seconds was required to reach 95% of the maximum steady-state current.

Also, the oxidation of calf thymus DNA at the carbon nanofiber paste electrode was investigated by differential pulse voltammetry (DPV). A clear signal, due to guanine oxidation, was obtained in the case of single-stranded DNA.     

Reduction of Dissolved Oxygen in Model Salad Dressing by Glucose Oxidase-Catalase Dependent on pH and Temperature

As the pH increased from 3, 4, 5, to 6, the amount of dissolved oxygen of the dressing decreased (α= 0.05). When the temperature increased from 10, 20 to 30 °C, the amount of dissolved oxygen decreased (α= 0.05). With the temperature increase from 30 to 40, 50 °C, the amount of dissolved oxygen increased. As the concentration of glucose increased from 0 to 0.5%, the amount of dissolved oxygen decreased (α= 0.05). There was no difference (α= 0.05) in dissolved oxygen reduction among the samples containing 0.5, 1.0, 1.5, or 2.0% glucose.     

Influence of Pentosanase and Oxidases on Water-extractable Pentosans during a Straight Breadmaking Process

ABSTRACT: Effects of flour type and enzymes on total pentosans (TP) and water‐soluble pentosans (WSP) and composition of isolated water‐extractable pentosans (WEP) during a straight breadmaking process were investigated. Two wheat flours (F1, F2) and 3 enzymes (pentosanase, glucose‐oxidase (GOX) and lacasse (LAC)), and their combinations were used. The presence of pentosanase increased the WSP content while oxidases produced a decrease. Extractability of pentosans was greater for dough than for bread but the latter had higher purity. Major sugars were xylose (Xyl) and arabinose (Ara) with a xylose/arabinose ratio between 1.00 and 1.56. Molecular weight profiles (MWP) of WEP comprised 5 fractions with the same distribution for the 2 flours but different relative proportions.     

Investigation of Electrochemical Properties of Carbon Nanofibers Prepared by CCVD Method

Carbon nanofibers, with diameters between 80 and 290 nm and specific area of 242 m²g^-1, have been prepared by the catalytic chemical vapor deposition method. After preparation, the powder was mixed with silicon oil in order to create a paste electrode. The electrochemical behavior of this type of electrode was investigated by cyclic voltammetry, using a solution of 10^-3 M ferrocenecarboxylic acid as mediator. The redox process is quasi-reversible, and it involves the transfer of electrons between Fe(II) and Fe(III).

The same mediator was used for the construction of a second-generation glucose biosensor. The mediator was co-immobilized with the enzyme in the carbon nanofibers paste. The sensor linearly responded to glucose, in the concentration range of 1.7 to 7 mM. A time of around 30 seconds was required to reach 95% of the maximum steady-state current.

Also, the oxidation of calf thymus DNA at the carbon nanofiber paste electrode was investigated by differential pulse voltammetry (DPV). A clear signal, due to guanine oxidation, was obtained in the case of single-stranded DNA.     

Immobilization of GOD on Ppy–PVS Composite Film for Determination of Glucose: A Comparative Study of Phosphate and Acetate Buffers

The Polypyrrole-polyvinylsulphonate-glucose oxidase (Ppy–PVS–GOD) biosensor for determination of glucose has been described in the present investigation. The enzyme, glucose oxidase (GOD) was immobilized by crosslinking via glutaraldehyde on a polypyrrole–polyvinyl sulphonate (Ppy–PVS) composite film. The Ppy–PVS film was electrochemically synthesized on indium-tin-oxide (ITO)–coated glass plate. The synthesized composite films were characterized using galvanostatic electrochemical technique, electrical conductivity, UV-Visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The crosslinking of enzyme and porous morphology of the polymer film leads to high enzyme loading and an increase in lifetime, stability, and fast response time of the enzyme electrode. Characterization of resulting amperometric biosensor for the estimation of glucose has been experimentally determined in terms of linear response range, optimum pH, applied potential, and shelf-life. These Ppy–PVS–GOD electrodes can be used for glucose estimation from 1 to 50 mM and have a shelf-life of about 5–6 weeks at 4°C. The sensitivity of Ppy–PVS–GOD electrode in phosphate and acetate buffer has been studied. It was found that the phosphate buffer gives fast response as compared to acetate buffer in amperometric measurements.