Papers by Grzegorz D Sulka
Electrochimica Acta, 2010
The formation of self-organized porous titania is achieved by electrochemical anodization under a... more The formation of self-organized porous titania is achieved by electrochemical anodization under a potentiostatic regime. Anodic titanium oxide (ATO) was fabricated by a three-step self-organized anodization of the Ti foil in an ethylene glycol electrolyte containing 0.38 wt% of NH 4 F and 1.79 wt% of H 2 O. Anodizing was carried out at the constant cell potential ranging from 30 to 70 V at the temperature of 20 • C. It was found that nanoporous TiO 2 arrays can be obtain only after a short duration of the third step (10 min). The influence of anodizing potential on the structural parameters of porous anodic titania including pore diameter, interpore distance, wall thickness, porosity and pore density was extensively studied. The linear dependencies between interpore distance, pore diameter and wall thickness upon the anodizing potential were found. The regularity of pore arrangement was monitored qualitatively by fast Fourier transforms (FFTs) of top-view FE-SEM images. It was found that the best arrangement of nanopores is observed at 40 V. This finding was confirmed by the analysis of pore circularity. The highest circularity of pores was observed once again at 40 V.
Electrochimica Acta, 2013
The hydroquinone monosulfonate-doped polypyrrole (PPy-HQS) nanowires were successfully fabricated... more The hydroquinone monosulfonate-doped polypyrrole (PPy-HQS) nanowires were successfully fabricated by potentiostatic electropolymerization of pyrrole (Py) inside the pores of home-made through-hole anodic aluminum oxide (AAO) membranes. The AAO templates with a nominal pore diameter of 80 nm were prepared by a two-step anodization process. The potentiostatic electropolymerization of HQSdoped polymer nanowires was carried out in 0.1 M NaClO 4 , or 0.1 M LiClO 4 or 0.1 M citric acid containing 0.05 M pyrrole and 0.05 M potassium hydroquinone monosulfonate. The synthesized PPy-HQS nanowire arrays were tested as potential potentiometric pH sensors. It was found that pH sensors based on PPy-HQS nanowires exhibited better electrochemical performance toward pH sensing than those based on PPy-HQS thin films. The best potentiometric response to pH changes and a very good stability in time showed the sensor based on the PPy-HQS nanowires polymerized in a 0.1 M LiClO 4 solution.
Anodic growth of TiO2 nanopore arrays at various temperatures
Electrochimica Acta, 2013
ABSTRACT Nanoporous anodic titanium oxide (ATO) layers with different cell sizes, pore diameters ... more ABSTRACT Nanoporous anodic titanium oxide (ATO) layers with different cell sizes, pore diameters and the thicknesses are successfully grown by three-step self-organized anodization in ethylene glycol containing 0.38 wt% of NH4F and 1.79 wt% of H2O at applied potential differences ranging from 30 V to 70 V at various electrolyte temperatures. A relatively high growth speed (about 40 μm h−1) of nanopore arrays is achieved at 30 °C under the potential difference of 70 V. The morphology and the structure of ATO layers are directly affected by anodizing conditions, especially temperature and potential difference. It was found that the oxide thickness and the cell size are linearly dependent on anodizing potential difference. On the other hand, the anodizing temperature in the range of 10–30 °C does not affect the cell size in ATO films. Analyses of the pore diameter, pore circularity and regularity of the pore arrangement suggests that nanoporous anodic titania with the best pore arrangement can be formed in a controlled manner by anodization performed at 50 V and 20 °C. Surprisingly, below and above this critical potential difference and temperature, pore diameters are smaller and obtained ATO structures are less regular. At higher anodizing temperatures, the regularity of pore arrangement observed at the surface and the pore diameter are considerably affected by the precipitated hydrous titanium dioxide.
Electrochimica Acta, 2010
The nanopore arrays were fabricated by two-step self-organized anodization of aluminum carried ou... more The nanopore arrays were fabricated by two-step self-organized anodization of aluminum carried out in 0.3 M oxalic acid at the temperature of 20 • C. This relatively high temperature shortens significantly the anodizing time and allows to fabricate quickly thick through-hole membranes without the additional operating cost of a cooling circuit. The structural features of anodic porous alumina such as pore diameter, interpore distance, porosity, pore density and pore circularity were investigated at various durations of pore opening/widening process carried out in 5% H 3 PO 4 . An excellent agreement of AAO structural features measured in FE-SEM images of the studied samples with results from software calculations was observed. The pore shape can be monitored qualitatively by fast Fourier transforms (FFTs) and quantitatively by calculation the percentage of pore circularity. Additionally, the regularity of the hexagonal arrangement of nanopores in through-hole AAO membranes was compared for various opening/widening time ranging from 40 to 100 min. It was shown that three-dimensional (3D) representations of FE-SEM images and their surface-height distribution diagrams provide interesting information about the surface roughness evolution during the pore opening/widening process. A template-assisted fabrication of Ag and Sn nanowire arrays by electrochemical deposition into the pores of the prepared AAO templates was also successfully demonstrated.
Electrochimica Acta, 2011
Anodic aluminum oxide (AAO) membranes with modulated pore diameter were synthesized by pulse anod... more Anodic aluminum oxide (AAO) membranes with modulated pore diameter were synthesized by pulse anodization in 0.3 M sulfuric acid at 1 • C. For AAO growth, a typical combination of alternating mild anodizing (MA) and hard anodizing (HA) pulses with applied potential pulses of 25 V and 35 V was applied. The control of the duration of HA pulses will provide an interesting way to tune the shape of pores and the structure of AAO channels. It was found that a non-uniform length of HA segments in cross section of AAO is usually observed when the HA pulse duration is shorter than 1.2 s. The pulse anodization performed with longer HA pulses leads to the formation of AAO templates with periodically modulated pore diameter and nearly uniform length of segments. Various diameter-modulated metallic nanowires (Au, Ag, Ni and Ag-Au) were fabricated by electrodeposition in the pores of anodic alumina membranes. A typical average nanowire diameter was about 30 nm and 48 nm for MA and HA nanowire segments, respectively. After a successful dealloying silver from Ag-Au nanowires, porous ultrathin Au nanowires were obtained.
Pulsatile Releasing Platform of Nanocontainers Equipped with Thermally Responsive Polymeric Nanovalves
Chemistry of Materials, 2013
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Papers by Grzegorz D Sulka