An inorganic anionic polymer filter disc: direct crystallization of a layered silicate nanosheet on a glass fiber filter

An inorganic anionic polymer filter disc was successfully produced from heterogeneous nucleation reactions of layered silicate fine crystals on amorphous silica glass fibers. This hybrid material can be obtained only by immersing the silica fiber filter disc in an aqueous solution containing LiF, MgCl2, and urea at 373 K for 48 h. Silica sol, which was partially dissolved from the silica fibers by hydrolysis of urea, was a source of the layered silicate. Firm immobilization of the layered silicate on the fiber silica was confirmed by immersing in aqueous LiCl solution (12 mM) for three weeks. The layered silicate crystals evenly covered the silica fibers while maintaining the original filter disc shape. Careful design of the layered silicate was performed by changing the molar LiF : MgCl2 : urea : SiO2 ratio. The layered silicate on the fibers became thick on adding increasing amounts of LiF and MgCl2. In addition, by increasing the amount of LiF, the negative charge density of the layered silicate increased, following the trend of caffeine adsorption in water. Furthermore, we found that the amount of urea added to the starting solution was important for preventing a loss in the mechanical strength of the fibers (e.g., fracture due to unnecessary dissolution of the silica fiber) and emerging side-reactions (e.g., polymerization of silica sol to yield spherical silica particles). The resulting layers of silicate on the filter disc acted as adsorption sites for both organic (methylene blue and benzylammonium) and inorganic (sodium, calcium, and europium) cationic species in water, as exemplified by batch and flow tests.ArticleRSC ADVANCES. 6(31): 26130-26136 (2016)journal articl

CRYSTAL GROWTH OF A HECTORITE-LIKE LAYERED SILICATE ON MONODISPERSE SPHERICAL SILICA PARTICLES WITH DIFFERENT DIAMETERS

Fine crystals of hectorite-like layered silicate formed using hydrothermal reactions on monodisperse spherical silica particles with diameters of 0.2, 0.6 and 1.0 μm. The reactions were performed in a colloidal spherical silica suspension with lithium and magnesium ions under alkaline conditions at 373 K in a rotating Teflon-lined autoclave at the LiF:MgCl_2:SiO_2 molar ratio of 0.21:0.8:8.0. The grain size distributions were quite uniform irrespective of the silica size in the initial mixtures, as a result of the high rate of heterogeneous nucleation reaction than that of the homogeneous nucleation. The amount of a cationic surfactant that was intercalated tended to be large when the grain size of the silica spheres was small, while the negative layer charge of the hectorite-like silicate was same extent.ArticleClay Science. 19(2): 45-51 (2015)journal articl

Adsorption of tetrakis(p-sulfonatophenyl)porphyrin on kaolinite

Copyright (c) 2009 Springer The original publication is available at www.springerlink.comThe surface modification of kaolinite to introduce the adsorption sites for anionic species was reported. The introduction of an anion exchange site was as follows; intercalation of 2-aminoethanol into kaolinite by using dimethyl sulfoxide-kaolinite intercalation compound as a precursor and subsequent hydrochlorination of 2-aminoethanol-kaolinite in 1,4-dioxane. The hydrochlorination of 2-aminoethanol-kaolinite was confirmed by the increase in the basal spacing (0.2 nm, corresponding to the diameter of chlorine) and the appearance of the infrared absorption bands due to ammonium groups. The modified kaolinite adsorbed an anionic dye, tetrakis(p-sulfonatophenyl)porphyrin, from a N,N-dimethylformamide solution. Initial slope of the adsorption isotherm of tetrakis(p-sulfonatophenyl)porphyrin on the hydrochlorinated 2-aminoethanol-kaolinite was steep, showing strong adsorbate-adsorbent interactions. The gallery height after the adsorption of tetrakis(p-sulfonatophenyl)porphyrin was close to the thickness of the porphyrin ring, suggesting that tetrakis(p-sulfonatophenyl)porphyrin was intercalated as a monomolecular layer and that chlorine simultaneously deintercalated.ArticleJOURNAL OF POROUS MATERIALS. 16(6):623-629 (2009)journal articl

Photochromic Intercalation Compounds

Photochromism of intercalation compounds has been investigated so far. Starting from fundamental studies on the photochromic reactions of the dyes in the presence of layered materials, the precise design of the nanostructures of intercalation compounds toward controlled photochemical reactions and the creation of novel photoresponsive supramolecular systems based on layered solids have been a topic of interests. Various layered materials with different surface chemistries have been used as hosts for the controlled orientation, and aggregation of the intercalated dyes and the states of the intercalated guests affected photoresponses. Molecular design of the photochromic dyes has also been conducted in order to organize them on layered solids with the desired manner. On the other hand, layered solids with such functions as semiconducting and magnetic have been examined to host photochromic dyes for the photoresponsive changes in the materials' properties.ArticlePHOTOFUNCTIONAL LAYERED MATERIALS. 166: 177-211 (2015)journal articl

Water-floatable organosilica particles for TiO2 photocatalysis

A water-floatable TiO2 photocatalyst support was successfully produced from organosilica via sol-gel reactions of organosilanes (octyl- and methyl-silyl trichlorides and 3-aminopropyltrimethoxysilane). 3-Aminopropyltrimethoxysilane in silane coupling agents was shown to have an important role in depositing highly dispersed TiO2 nanocrystals onto organosilica particles. Calcination of the as-made sample at 400 degrees C in an airflow resulted in the loss of octyl- and 3-aminopropyl groups, modifying polymethylsiloxane while maintaining water floatability. Calcination led to an increase in the specific surface area from 88 to 230 m(2)/g and the growth of anatase crystallites. Floatability was not observed when the as-made sample was calcined at 600 degrees C, showing that methyl groups acted as surfactants at the air-water interface. Formic acid in water was catalytically oxidized over the water-floatable sample upon irradiation by a solar simulator. The evolved CO2 became saturated when the surface of the aqueous solution was filled with the floating particles. We demonstrated the importance of the floating photocatalyst with respect to the efficiency of light receipt and facile recovery from liquid media. (C) 2016 Elsevier B.V. All rights reserved.ArticleCHEMICAL ENGINEERING JOURNAL. 299: 367-372 (2016)journal articl

Vesicle formation in mixture of a PEO-PPO-PEO block copolymer (Pluronic P123) and a nonionic surfactant (Span 65) in water

Fabrication of vesicles with the diameter of 4-30 mu m was achieved by mixing hydrophobic nonionic surfactant (Span 65) with a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer (Pluronic P123) in aqueous solutions at room temperature. Ring-shaped structure of the Plutonic P123/Span 65 mixture assemblies was confirmed by fluorescence microscopy. The presence of internal aqueous phase in the Pluronic P123/Span 65 mixture assemblies was determined by measuring the entrapment efficiency of calcein using fluorescence spectroscopy. On the other hand, Pluronic P123/Span 60 mixture system formed wire-like assemblies but not vesicles.ArticleCOLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS. 389(1-3):82-89 (2011)journal articl

Concentration of 2-phenylphenol by organoclays from aqueous sucrose solution

The adsorption of 2-phenylphenol, which is an antifungal agent, onto organically modified clay from aqueous sucrose solution was investigated. 2-Phenylphenol was effectively adsorbed on neostigmine-modified smectites and octadecyltrimethylammoniurh modified smectites even in the presence of sucrose in the starting aqueous solution. Two smectites (a natural montmorillonite, Kunipia F, and a synthetic saponite, Sumecton SA) were used to find clay minerals with lower layer charge density gave larger adsorption capacity for 2-phenylphenol. The result showed the potential application of the organically modified clays to remove 2-phenylphenol from orange extracts. (C) 2014 Published by Elsevier B.V.ArticleAPPLIED CLAY SCIENCE. 109: 64-67 (2015)journal articl

Titania/C-n TAB Nanoskeleton as adsorbent and photocatalyst for removal of alkylphenols dissolved in water

We report here on the removal of alkylphenols (phenol, 4-n-propylphenol, 4-n-heptylphenol and 4-nonylphenol) dissolved in water using the composite particles of nanocrystalline titania and alkyltrimethylammonium bromide (CnH2n+1N(CH3)(3)Br, C(n)TAB; n = 12, 14, 16 and 18) (named as TiO2/C(n)TAB Nanoskeleton) as adsorbents and photocatalysts. In particular, the adsorption of alkylphenols onto TiO2/C(n)TAB Nanoskeleton in water was investigated in terms of hydrophobic interaction between alkylphenols and C(n)TAB, surface area, pore structure and crystal size of TiO2/C(n)TAB Nanoskeleton. We revealed that C(n)TAB incorporated in the TiO2/C(n)TAB Nanoskeleton promotes the adsorption of alkylphenols onto TiO2/C(n)TAB Nanoskeleton due to the hydrophobic interaction between alkylphenols and C(n)TAB. On the other hand, the surface area, pore structure and crystal size of TiO2/C(n)TAB Nanoskeleton did not affect the adsorption of allcylphenols onto TiO2/C(n)TAB Nanoskeleton. We also found that the alkylphenols dissolved in water were completely removed by the combination of adsorption and photocatalytic degradation by the TiO2/C(n)TAB Nanoskeleton under UV irradiation. These results prove that the TiO2/C(n)TAB Nanoskeleton acts as in tandem an adsorbent and a photocatalyst for removal of alkylphenols dissolved in water.ArticleJOURNAL OF HAZARDOUS MATERIALS. 248:487-495 (2013)journal articl

Crystal architectures of a layered silicate on monodisperse spherical silica particles cause the topochemical expansion of the core-shell particles

Anisotropic structural changes in an expandable layered silicate (directed towards the c-axis) occurring on isotropic and monodisperse microspheres were detected by measurable increases in the grain size. The hierarchical changes were observed through pursing the sophisticated growth of expandable layered silicate crystals on monodisperse spherical silica particles with diameters of 1.0 mu m; the core-shell hybrids with a quite uniform grain size were successfully produced using a rotating Teflon-lined autoclave by reacting spherical silica particles in a colloidal suspension with lithium and magnesium ions under alkaline conditions at 373 K. The size distribution of the core-shell particles tended to be uniform when the amount of lithium ions in the initial mixture decreased. The intercalation of dioctadecyldimethylammonium ions into the small crystals through cation-exchange reactions expanded the interlayer space, topochemically increasing the grain size without any change occurring in the shapes of the core-shell particles. (C) 2015 Elsevier Inc. All rights reserved.ArticleMICROPOROUS AND MESOPOROUS MATERIALS. 215:168-174 (2015)journal articl

Block copolymer-mediated synthesis of gold nanoparticles in aqueous solutions: Segment effect on gold ion reduction, stabilization, and particle morphology

We report here on the segment effects of poly(ethylene oxide)-containing block copolymers (PEO-BCP) on the reduction activity for tetrachloride gold(III) ([AuCl4](-)), interfacial activity for gold surface, colloidal stability, and morphology of gold nanoparticles formed in aqueous solutions. In particular, the effects of poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), polyethylene (PE) segments and amino group (NH2) on the rate of [AuCl4](-) reduction, adsorption of PEO-BCP onto gold surface, colloidal stability, and morphology of gold nanoparticles formed in aqueous solutions were examined using a poly(ethylene oxide)-poly(propylene oxide) triblock copolymer (PEO-PPO-PEO, Pluronic L44), an amino-terminated poly(ethylene oxide)-poly(propylene oxide) block copolymer (PEO-PPO-NH2, SURFONAMINE(R) L-207), a poly(ethylene oxide) homopolymer (PEO, poly(ethylene glycol)2000), and a polyethylene-poly(ethylene oxide) block copolymer (PE-PEO). We found that the reduction activity of PEO-BCP for [AuCl4](-) became higher with the order of PEO-PPO-NH2 < PE-PEO < PEO < PEO-PPO-PEO. The interfacial activity (affinity) of PEO-BCP for gold surface increased with the order of PEO < PE-PEO < PEO-PPO-PEO < PEO-PPO-NH2. Consequently, the colloidal stability of gold nanoparticles formed in aqueous PEO-PPO-NH2 solutions was extremely high compared with that in PEO, PEO-PPO-PEO, and PE-PEO solutions. In addition, the size of gold nanoparticles formed in aqueous PEO-PPO-NH2 solutions was much smaller than that in aqueous solutions of PEO-PPO-PEO, PEO or PE-PEO.ArticleJOURNAL OF COLLOID AND INTERFACE SCIENCE. 394:124-131 (2013)journal articl