74 research outputs found
New sensors based on silver nanowire arrays
Owing to its strong oxidizing properties, hydrogen peroxide has a wide range of applications. It is a key component for many industrial applications, such as pharmaceutical and cosmetic production or sterilization. Moreover, is produced in the human body by immune system cells and is a product of glucose oxidation. Therefore, creating an effective and selective method of detection has been of great importance. A novel glucose sensor, based on silver nanowires deposited into nanoporous anodic aluminum oxide (AAO) templates has been proposed. AAO templates has been prepared via anodization of Al in three electrolytes: oxalic, sulphuric and phosphoric acids. Silver nanowires has been created by deposition of silver in AAO templates. Electrodes based on silver nanowires were then investigated for electrocatalytical properties. reduction on silver nanowires was tested using cyclic voltammetry (CV) and chronoamperometry (ChA). An influence of interfering substances like ascorbic acid was also examined
Anodic alumina membranes with defined pore diameters and thicknesses obtained by adjusting the anodizing duration and pore opening/widening time
The through-hole porous anodic aluminum oxide (AAO) membranes were fabricated by a simple two-step anodization of aluminum in 0.3 M oxalic acid, 0.3 M sulfuric acid, and 2 wt.% phosphoric acid solutions under different operating conditions followed by the removal of the remaining Al substrate and the pore opening/widening process. The effect of duration of the second anodizing step on the thickness of the porous oxide layer and the influence of other anodizing conditions such as applied voltage, type of electrolyte, and purity of the substrate on the rate of porous oxide growth were discussed in detail. The pore opening procedure for all synthesized membranes was optimized, and the influence of the duration of chemical etching on structural features of AAO membranes, especially pore diameter, was studied. The rate of pore widening was established for AAO membranes formed in various anodizing electrolytes and for different temperatures of 5 wt.% H3PO4 used for alumina dissolution
Effect of different polishing methods on anodic titanium dioxide formation
Among various methods of synthesis of nanostructured TiO2, a self-organized anodization is the most commonly used and discussed in the literature. However, different methods of pretreatment of Ti before anodic titanium dioxide (ATO) formation are not often addressed. Therefore, various polishing procedures based on mechanical, chemical, electrochemical, and combined electrochemical with chemical pretreatments were examined to establish whether they represent effective methods for smooth Ti surface preparation before anodization. The ATO layers were prepared via two-step anodization carried out in an ethylene glycol solution containing fluoride ions at 20°C and under the anodizing potential of 60 V. The influence of applied polishing method on the cell size, pore diameter, pore circularity, pore density, and porosity of the top ATO layer was studied. In addition, the effect of polishing procedure on cell arrangement in ATO films was also investigated. The quantitative analyses of the regularity of cell arrangement, based on the regularity ratio derived from bottom-view SEM images, showed that the type of polishing procedure does not affect the cell order
Porous alumina membranes with branched nanopores as templates for fabrication of Y-shaped nanowire arrays
Analysis of nanopore arrangement and structural features of anodic alumina layers formed by two-step anodizing in oxalic acid using the dedicated executable software
Anodic porous alumina layers were fabricated
by a two-step self-organized anodization in 0.3 M oxalic
acid under various anodizing potentials ranging from 30 to
60 V at two different temperatures (10 and 17
◦
C). The ef-
fect of anodizing conditions on structural features and pore
arrangement of AAO was investigated in detail by using
the dedicated executable publication combined with ImageJ
software. With increasing anodizing potential, a linear in-
crease of the average pore diameter, interpore distance, wall
thickness and barrier layer thickness, as well as a decrease of
the pore density, were observed. In addition, the higher pore
diameter and porosity values were obtained for samples an-
odized at the elevated temperature, independently of the an-
odizing potential. A degree of pore order was investigated on
the basis of Delaunay triangulations (defect maps) and cal-
culation of pair distribution or angle distribution functions
(PDF or ADF), respectively. All methods confirmed that in
order to obtain nanoporous alumina with the best, hexag-
onal pore arrangement, the potential of 40 V should be ap-
plied during anodization. It was confirmed that the dedicated
executable publication can be used to a fast and complex analysis of nanopore arrangement and structural features of
nanoporous oxide layers
The effect of anode surface area on nanoporous oxide formation during anodizing of low purity aluminum (AA1050 alloy)
Porous anodic alumina layers were obtained by a simple two-step anodization of low purity aluminum (99.5 % Al, AA1050 alloy) in a 0.3 M oxalic acid electrolyte at 45 V and 20 °C. The effect of anode surface area on structural features of nanoporous oxide and process of oxide formation was investigated. An ordered structure composed of nanostripes or nanopores was formed on the Al surface during electrochemical polishing in a mixture of perchloric acid and ethanol. This nanopattern is then replicated during the anodic oxide formation. It was found that the pore diameter, interpore distance, and porosity increase slightly with increasing surface area of the aluminum sample exposed to the anodizing electrolyte. On the other hand, a slight decrease in pore density and cell wall thickness was observed with increasing surface area of the sample. The detailed inspection of current density vs. time curves was also performed. The obtained results revealed that the higher surface area of the anode, the local current density minimum, was reached faster during first step of anodization and the increase in current density corresponding to the pore rearrangement process was observed earlier. Finally, a dense array of Pd nanowires (∼90 nm in diameter) was synthesized by simple electrodeposition of metal inside the channels of through-hole nanoporous anodic alumina templates with relatively large surface areas (4 cm2)
Progress in biomedicine and neuromedicine : proceeding of the International Workshop (Humboldt-Kolleg) of Societas Hunboldtiana Polonorum & Polish Chemical Society, Kraków, June 21-23, 2015
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