2 research outputs found
Determination of the pH Dependent Redox Potential of Glucose Oxidase by Spectroelectrochemistry
The
pH dependent redox potential of the oxidoreductase glucose
oxidase (GOx) from Aspergillus niger, which is the most frequently applied enzyme in electrochemical
glucose biosensors and biofuel cells, was measured between pH 4.5
and 8.5 using UV/vis spectroelectrochemistry. In the entire pH range
under investigation, the flavin adenine dinucleotide cofactor of
GOx changed directly from the oxidized quinone to the doubly reduced
hydroquinone. No stable semiquinoid species could be detected if electrochemical
equilibrium was reached. From the pH dependency of the GOx redox potential,
a p<i>K</i><sub>a</sub> of 7.2 has been determined for the
GOx flavohydroquinone. At pH values ≤6.0, a dependency of the
reduction mechanism and the GOx redox potential on the presence of
halides, especially on Cl<sup>–</sup>, was observed. For the
development of glucose biosensors and glucose biofuel cell anodes
working at physiological or neutral pH, the GOx redox potentials at
pH 7.4 and pH 7.0 are of main interest. Here values of <i>E</i><sub>1/2 pH 7.4</sub> = −97 ± 3 mV and <i>E</i><sub>1/2 pH 7.0</sub> = −80 ± 4 mV
have been determined
Correlation of Electrical and Structural Properties of Single As-Grown GaAs Nanowires on Si (111) Substrates
We present the results of the study
of the correlation between the electrical and structural properties
of individual GaAs nanowires measured in their as-grown geometry.
The resistance and the effective charge carrier mobility were extracted
for several nanowires, and subsequently, the same nano-objects were
investigated using X-ray nanodiffraction. This revealed a number of
perfectly stacked zincblende and twinned zincblende units separated
by axial interfaces. Our results suggest a correlation between the
electrical parameters and the number of intrinsic interfaces