We investigated human plasma fibrinogen (HPF) immobilization onto a planar sodium polystyrene sulfonate (NaPSS) brush in a protein aqueous solution. The saturated amount and time constant of the phenomenon were measured using time-resolved attenuated total reflection (ATR) UV absorption technique. The static and kinetic behavior were revealed to depend on the salt concentration in the protein solution. The results indicate that the immobilization is driven by the entropic effect and coulombic interaction, in contrast to previous reports for micellar PEB that the entropic effect is dominant. The immobilization mechanism identified in this work is independent of the molecular species and is applicable for any combination of protein and planar PEB with the same sign of charge in water, which is consistent with the nonspecific immobilization of proteins onto various PEB that has been reported to date.
Recently, Ba1−xSrxTiO3, with a perovskite structure, has drawn much attention as a dielectric material. For this study, we prepared Ba0.7Sr0.3TiO3 films using electrophoretic deposition with Ba0.7Sr0.3TiO3 fine particles of various sizes. For the film-forming process, we optimized the deposition voltage, deposition time, sample concentration, I2 concentration, and other parameters. Results show that the film thickness is controllable by changing the deposition time and voltage, although higher voltage made the film inhomogeneous. A film prepared with larger particles seemed to have lower density, but the density was improved using heat treatment at higher temperatures. Investigation of dielectric properties of the films revealed that a Ba0.7Sr0.3TiO3 film deposited in 0.5 g·L−1 I2-added acetone for 8 s at 50 V with a particle size of 0.3 μm and then heat-treated at 900 °C for 30 min had 2.52 μm thickness. It exhibited capacitance density of 113.9 nF·cm−2.
A technique of immobilizing copper ions through a polypyrrole thin film that is covalently bonded to a substrate surface through a chemically adsorbed monolayer containing pyrrolyl group (PNN-CAM) was studied. Contact angle, Fourier transform infrared (FT-IR), UV-visible, and film thickness measurements were done to characterize the PNN-CAM and the polypyrrole thin film. The water contact angles on the slide glass changed from 4.5° to 67.0° by preparing the PNN-CAM. In the FT-IR spectrum for the slide glass covered with the PNN-CAM, strong bands attributable to the νasCH2 vibrations and νsCH2 appeared respectively at 2925 cm−1 and 2850 cm−1. These results indicate that PNN-CAM was prepared on the slide glass. In the subtracted UV-visible spectra before and after oxidative polymerization, a strong absorption band appearing at approximately 230 nm was assigned to the conjugated bonds of the polypyrrole groups. The result indicates that a polypyrrole thin film was prepared on the PNN-CAM. Measurements of the PNN-CAM and polypyrrole thin film using an automatic ellipsometer showed the respective thicknesses to be ca. 1.7 nm and ca. 2.1 nm. X-ray photoelectron spectroscopy (XPS) was also applied to confirm the immobilization of copper ions on the silicon substrate. Cu(2p) peak was observed from the silicon substrate covered with polypyrrole thin film after ultrasonic cleaning and wiping with wet cotton cloth. The result demonstrates the formation of the complex between the copper ions and the nitrogen atoms of the pyrrolyl groups.
Micrometer-scale patterning of a sol-gel derived TiO2 film was formed on a titanium plate using photo-irradiation patterning. The patterned TiO2 on a micrometer scale, which had nearly the same design as the TiO2 gel film, was formed at pulsed-current density by anodic oxidation in an alkaline bath under spark discharge.