Thermoresponsive polymer brush on monolithic-silica-rod for the high-speed separation of bioactive compounds

Poly(N-isopropylacrylamide), one of the most utilized thermoresponsive polymers, brush-grafted monolithic-silica columns were prepared through surface-initiated atom transfer radical polymerization (ATRP) for effective thermoresponsive-chromatography matrices. ATRP initiator was grafted on monolithic silica-rod surfaces by flowing a toluene solution containing ATRP initiator into monolithic silica-rod columns. N-Isopropylacrylamide (IPAAm) monomer and CuCl/CuCl(2)/Me(6)TREN, an ATRP catalytic system, were dissolved in 2-propanol, and the reaction solution was pumped into the preprepared initiator-modified columns at 25 °C for 16 h. The constructed PIPAAm-brush structure on the monolithic silica-rod surface was confirmed by XPS, elemental analysis, SEM observation, and GPC measurement of grafted PIPAAm. The prepared monolithic silica-rod columns were also characterized by chromatographic analysis. PIPAAm-brush-modified monolithic silica-rod columns were able to separate hydrophobic steroids with a short analysis time (10 min), compared to PIPAAm-brush-modified silica-beads-packed columns, because of the horizontally limited diffusion path length of monolithic supporting materials. Additionally, diluted PIPAAm-brush monolithic silica-rod column gave a further shorting analysis time (5 min). These results indicated (1) surface-initiated ATRP constructed PIPAAm-brush structures on monolithic silica-rod surfaces and (2) PIPAAm-brush grafted monolithic silica-rod column prepared by ATRP was a promising tool for analyzing hydrophobic-bioactive compounds with a short analysis time.     

Carrier dynamics and magneto-transport in Kondo-Hubbard model

The motion of a single hole in the antiferromagnetic ground state and in the paramagnetic state at high temperatures is studied in the Kondo-Hubbard model with Hund coupling. It is shown that the Hund coupling strongly reduces both band-width of the coherent state at the ground state and the mobility at high temperatures. Implications of the results to magneto-transport phenomena in manganites are presented.     

Carrier dynamics and magneto-transport in Kondo-Hubbard model

The motion of a single hole in the antiferromagnetic ground state and in the paramagnetic state at high temperatures is studied in the Kondo-Hubbard model with Hund coupling. It is shown that the Hund coupling strongly reduces both band-width of the coherent state at the ground state and the mobility at high temperatures. Implications of the results to magneto-transport phenomena in manganites are presented.     

Simple,fast, and ultrasensitive method for textile dye determination based on luminol electrochemiluminescence (ECL) inhibition

Journal of Solid State Electrochemistry - Textile dyes are considered micropollutants or emerging pollutants since they can be present in the environment at very low concentrations and show...     

Competing thermal relaxation processes in response to intrinsic defects produced by exposing SiO2 to synchrotron radiation

Irradiation of SiO₂ with soft X-ray photons (hν>100 eV) produces a variety of defects, of which E₁′ centers and neutral Si–Si bonds are mainly responsible for the dielectric response change. The thermal processes that modify the structures around the defect sites have been investigated by in situ spectroscopic ellipsometry. Annealing the irradiated SiO₂ film diminishes the number of defects which are assigned to E₁′ centers by about half. The competing channels for annihilation of E₁′ centers are the recovery of the Si–O–Si bonding configuration and, in the opposite direction, the decomposition of the material into volatile products until the network is completely restructured. The other half of the defects are converted to Si–Si bond units and precipitates as nanocrystalline particles of Si.     

Structure and sorption properties of the polyion complex between poly(acrylic acid) and poly(4-vinylpyridine)

A polyion complex was formed from poly(acrylic acid) (PAA) and poly(4-vinylpyridine) (PVP). Its structure and composition were examined by means of infrared spectroscopy (IR), x-ray photoelectron spectroscopy (XPS), and elemental analysis. The polyion complex was obtained by dissolving PAA and PVP together in methanol. The composition of the polyion complex was independent of stirring speed, mixing sequence, and standing time after mixing. However, the composition depended on the concentrations and the ratio of the components in the reaction mixture. Excess of PAA in the product was observed when concentrated solutions (2.0 × 10^?1M) were used for the preparation or when an excess of PAA was added to PVP. The sorption of water vapor by an equimolar PAA/PVP complex at 293 and 303 K was higher than that by the pure components, especially in the low- and middle-pressure regions. In the high-pressure region, however, the uptake was not affected by the complex formation. While hydrogen bond interactions in general decrease sorption, Coulombic interactions between polymer chains increased the sorption capacity.     

Synchrotron radiation-stimulated photochemical reaction and its application to semiconductor processes

Recent results are reviewed on synchrotron radiation (SR)-excited photochemical reaction studies aimed at applications to semiconductor processes. Valence or core electronic excitations induced by SR irradiation and ensuing chemical reactions are classified and characterized by rate equations. Unique material selectivity in etching has been found. SiO₂ has been found to evaporate by SR irradiation and this phenomenon can be applied to the low-temperature surface cleaning of silicon. In the epitaxial growth of Silicon by ultrahighvacuum chemical vapor deposition using Si₂H₆, SR irradiation significantly lowers growth temperature beyond the low-temperature limit of thermal reaction. Lowering of the operating temperature by SR irradiation is especially effective in applications to the atomic layer epitaxial growth of silicon. The layer-by-layer process has been successfully demonstrated, confirming self-limiting adsorption of SiH₂Cl₂ and ensuring surface reactivation by SR irradiation.     

Electroorganic chemistry—XV : Electroreduction of sulfonium and ammonium salts. Formation of sulfonium ylids

In the electroreduction of sulfonium and ammonium salts, sulfonium ylid was generated from the sulfonium salt, whereas in the case of the ammonium salt, nitrogen ylid was not formed but the N+C bond was reductively cleaved. On the basis of the controlled potential electrolysis, it seems acceptable that the mechanism of formation of sulfonium ylid involves the direct electron transfer to the sulfonium salt as the initiation step.