Norifumi Isu

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer/anatase titanium oxide nanocomposites possessing photocatalytic activity even after calcination at 1000°C.

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [R(F)-(VM)(n)-R(F)] underwent the sol-gel reaction under alkaline conditions in the presence of anatase titanium oxide nanoparticles (an-TiO(2)) in tetrahydrofuran to give the corresponding fluorinated oligomer/anatase titanium oxide nanocomposites [R(F)-(VM-SiO(2))(n)-R(F)/an-TiO(2)]. Crystalline structure of an-TiO(2) in the nanocomposites thus obtained was found to keep completely its structure without phase transformation to rutile even after calcination at 1000°C, although crystalline structure of the original an-TiO(2) nanoparticles underwent a complete phase transformation to the rutile under similar conditions. Interestingly, R(F)-(VM-SiO(2))(n)-R(F)/an-TiO(2) nanocomposites before and after calcination at 1000°C exhibited the similar photocatalytic activity for the decolorization of methylene blue under UV light irradiation.

Preparation and Properties of Novel Fluoroalkyl End-capped Oligomers/Hydrogarnet Nanocomposites

Novel fluoroalkyl end-capped oligomers/hydrogarnet (katoite) nanocomposites were prepared by the hydrothermal reactions of a stoichiometric mixture of Ca(OH)2, Al(OH)3, and Al2Si2O 5(OH)4 in the presence of the corresponding fluorinated acrylic acid, acryloylmorpholine, and N,N-dimethylacrylamide oligomers. These fluorinated katoite nanocomposites thus obtained are nanometer size-controlled, and were found to exhibit a good dispersibility in water, methanol, ethanol, and tetrahydrofuran. Fluoroalkyl end-capped oligomers were also applied to the dispersion of parent katoite into these solvents; however, a poor dispersiblity for these solvents was observed. On the other hand, fluoroalkyl end-capped 2-methacryloyloxyethanesulfonic acid oligomer [RF—(MES) n—RF] was able to solubilize katoite into water to afford the transparent colorless solution. The obtained RF—(MES) n—RF/katoite nanocomposites were found to exhibit a good antibacterial activity against Staphylococcus aureus, and were also applied to the surface modification of poly(vinyl alcohol) to exhibit a good oleophobicity imparted by fluorine on the surface.

XAFS and XRF studies of anti-bacterial ceramics using synchrotron radiation

Recently anti-bacterial techniques have been spread into daily commodities with improving consciousness of health. Silver is most common anti-bacterial chemicals for anti-bacterial consumers in Japan, however, the resource of silver is limited and it became so expensive to be used for daily commercial item. In addition, the anti-bacterial effects on silver have not been elucidated because of difficulties of in-situ chemical state analyses for these systems. In this study, XAFS and XRF analyses using Synchrotron Radiation were applied for Ag in the sanitary wares and Zn in anti-bacterial tiles which are the products of INAX co. in order to elucidate the anti bacterial mechanism of these elements and develop new anti-bacterial material instead of limited silver. Each specimen was cut into 1cm x 1cm blocks to be used for XAFS measurements. The glaze of these specimens were examined with XRD, however, no crystalline materials was detected. From elemental analyses using EPMA, a content of silver was about 0.08wt% in sanitary ware and that of zinc was about 15wt% in anti-bacterial tiles. XAFS spectra of the silver in sanitary ware measured in fluorescence mode at AR-NW10A with MSSD for K-edge, and at BL9A with Lytle type detector at SX-mode for L-edge in Photon Factory. XAFS spectra for zinc were measured at BL12C and BL9A with Lytle type detector. The Ag LIII-XANES spectra of the sanitary indicated that chemical state of the silver was mono-valent similar to Ag2O, however, EXAFS spectra of the sanitary ware was different from crystalline Ag2O but amorphous without 2 neighbor interactions. The Ag ion was coordinated with about two oxygens in 2.22A. On the other hands, zinc in the anti-bacterial tile was divalent and the local structure was similar to Zn2SiO4 which is coordinated with four oxygens in 1.96A. Zinc in the anti-bacterial tiles should be cooperated with SiO4 network but its crystalinty was low. Fig. 1 Ag LIII-XANES spectra of the sanitary ware