More than 50 years have passed since Clark and Lyon developed the concept of glucose biosensors. Extensive research about biosensors has been carried out up to this day, and an exponential trend in this topic can be observed. The scope of this review is to present various enzyme immobilization methods on gold nanoparticles used for glucose sensing over the past five years. This work covers covalent bonding, adsorption, cross-linking, entrapment, and self-assembled monolayer methods. The experimental approach of each modification as well as further results are described. Designated values of sensitivity, the limit of detection, and linear range are used for the comparison of immobilization techniques.
The selection of efficient corrosion inhibitors requires detailed knowledge regarding the interaction mechanism, which depends on the type and amount of functional groups within the inhibitor molecule. The position of functional groups between different isomers is often overlooked, but is no less important, since factors like steric hinderance may significantly affect the adsorption mechanism. In this study, we have presented how different dihydroxybenzene isomers interact with aluminum alloy 5754 surface, reducing its corrosion rate in bicarbonate buffer (pH = 11). We show that the highest inhibition efficiency among tested compounds belongs to catechol at 10 mM concentration, although the differences were moderate. Utilization of novel impedance approach to adsorption isotherm determination made it possible to confirm that while resorcinol chemisorbs on aluminum surface, catechol and quinol follows the ligand exchange model of adsorption. Unlike catechol and quinol, the protection mechanism of resorcinol is bound to interaction with insoluble aluminum corrosion products layer and was only found efficient at concentration of 100 mM (98.7%). The aforementioned studies were confirmed with Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy analyses. There is a significant increase in the corrosion resistance offered by catechol at 10 mM after 24 h exposure in electrolyte: from 63 to 98%, with only negligible changes in inhibitor efficiency observed for resorcinol at the same time. However, in the case of resorcinol a change in electrolyte color was observed. We have revealed that the differentiating factor is the keto-enol tautomerism. The Nuclear Magnetic Resonance (NMR) studies of resorcinol indicate the keto form in structure in presence of NaOH, while the chemical structure of catechol does not change significantly in alkaline environment.
In this article, we studied the annealing
process of AuCu layers
deposited on TiO2 nanotubes (NTs) conducted in various
atmospheres such as air, vacuum, argon, and hydrogen in order to obtain
materials active in both visible and UV–vis ranges. The material
fabrication route covers the electrochemical anodization of a Ti plate,
followed by thin AuCu film magnetron sputtering and further thermal
treatment. Scanning electron microscopy images confirmed the presence
of spherical nanoparticles (NPs) formed on the external and internal
walls of NTs. The optical and structural properties were characterized
using UV–vis, X-ray diffraction, and X-ray photoelectron spectroscopies.
It was proved that thermal processing under the argon atmosphere leads
to the formation of a CuAuTi alloy in contrast to materials fabricated
in air, vacuum, and hydrogen. The electrochemical measurements were
carried out in NaOH using cyclic voltammetry, linear voltammetry,
and chronoamperometry. The highest photoactivity was achieved for
materials thermally treated in the argon atmosphere. In addition,
the Mott–Schottky analysis was performed for bare TiO2 NTs and TiO2 NTs modified with gold copper NPs indicating
a shift in the flatband potential. Overall, thermal processing resulted
in changes in optical and structural properties as well as electrochemical
and photoelectrochemical activities.
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