-
[show abstract]
[hide abstract]
ABSTRACT: Water wettabilities of hydrophilic-hydrophobic nanohybrid silica thin films were investigated by contact angles of extremely small size water droplets (8 pL-1 nL) and using an antifog analyzer. The nanohybrid silica was prepared via our unique sol-gel process based on tetramethoxysilane (TMOS) and metyltrimethoxysilane (MTMS) with a hydroxyacetone catalyst, in which hydrophilic portion was generated from hydrolysis of microporous silica prepared from TMOS and hydrophobic portion was directly prepared from MTMS. The sizes of these domains were controlled by the growth time of the microporous precursor polymers in solution. The hydrophilic and hydrophobic domains in the nanohybrid surface were visualized and confirmed by a lateral-mode friction force microscopy using the cantilever modified with self-assembled monolayers of mercaptohexadecanol. Using a small size of water droplets (< 100 pL), the contact angles for the nanohybrid silica films were lower than those for the wholly hydrophilic silica. The small size of the water droplet has a characteristic effect on the lower contact angle on the nanohybrid silica. The contact angles using the small size 70 pL of the water droplet on the nanohybrid silica films at [MTMS]/[TMOS] ratios from 0.25 to 0.75 were lower than those using the conventional size 2 microL. The dependence of the [MTMS]/[TMOS] ratio in the preparation on the antifog parameter was similar to that on the contact angle using the small size 70 pL of the water droplet. The use of the small water droplet for the contact angle measurement was suitable for the evaluation of the antifog films.
Journal of Nanoscience and Nanotechnology 04/2013; 13(4):2758-64. · 1.56 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Amorphous titanium dioxide (TiO(2)) thin films exhibiting high refractive indices (n ≈ 2.1) and high transparency were fabricated by spin-coating titanium oxide liquid precursors having a weakly branched polymeric structure. The precursor solution was prepared from titanium tetra-n-butoxide (TTBO) via the catalytic sol-gel process with hydrazine monohydrochloride used as a salt catalyst, which serves as a conjugate acid-base pair catalyst. Our unique catalytic sol-gel technique accelerated the overall polycondensation reaction of partially hydrolyzed alkoxides, which facilitated the formation of liner polymer-like titanium oxide aggregates having a low fractal dimension of ca. (5)/(3), known as a characteristic of the so-called "expanded polymer chain". Such linear polymeric features are essential to the production of highly dense amorphous TiO(2) thin films; mutual interpenetration of the linear polymeric aggregates avoided the creation of void space that is often generated by the densification of high-fractal-dimension (particle-like) aggregates produced in a conventional sol-gel process. The mesh size of the titanium oxide polymers can be tuned either by water concentration or the reaction time, and the smaller mesh size in the liquid precursor led to a higher n value of the solid thin film, thanks to its higher local electron density. The reaction that required no addition of organic ligand to stabilize titanium alkoxides was advantageous to overcoming issues from organic residues such as coloration. The dense amorphous film structure suppressed light scattering loss owing to its extremely smooth surface and the absence of inhomogeneous grains or particles. Furthermore, the fabrication can be accomplished at a low heating temperature of <80 °C. Indeed, we successfully obtained a transparent film with a high refractive index of n = 2.064 (at λ = 633 nm) on a low-heat-resistance plastic, poly(methyl methacrylate), at 60 °C. The result offers an efficient route to high-refractive-index amorphous TiO(2) films as well as base materials for a wider range of applications.
Langmuir 07/2012; 28(33):12245-55. · 4.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Titanium oxide polymers having a low-fractal dimension (d(f) < 2) were rapidly synthesized from titanium tetra-n-butoxide via a catalytic sol-gel process with a hydrazine monohydrochloride catalyst. Different from conventional sol-gel processes aimed at producing low-fractal dimension titanium oxide polymers, the present synthetic strategy needed neither organic ligand to enhance the stability of titanium alkoxides nor an extremely long reaction time in a strongly acidic solution condition, thanks to a drastically accelerated polycondensation reaction. We pursued the structure evolution of the titanium oxide polymers by means of time-resolved small-angle X-ray scattering (Tr-SAXS). The SAXS data unambiguously demonstrate the generation of the expanded polymer-like structure characterized by the fractal dimension of d(f) approximately equal 5/3. The results offer an efficient route to the synthesis of the weakly-branched titanium oxide polymers, which are expected to be used to create a wide range of optical materials having a high refractive index, such as anti-glare coating.
Journal of Nanoscience and Nanotechnology 05/2012; 12(5):3732-8. · 1.56 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We measured the production levels of seven different matrix metalloproteinases (MMP-1, 2, 3, 7, 8, 9 and 13) and two tissue
inhibitors of metalloproteinases (TIMP-1 and 2) in the homogenates of human oral squamous cell carcinomas and control normal
squamous epithelia by the corresponding sandwich enzyme immunoassay systems. The levels of MMP-1, 2, 3, 8, 9, 13 and TIMP-1
were significantly higher in the carcinoma samples than in the control. Among them, only the production level of MMP-2 was
significantly higher in the carcinomas with cervical lymph node metastasis than in those without metastasis (P < 0.05). Gelatin zymography demonstrated that activation ratio of the zymogen of MMP-2 (proMMP-2) is significantly higher
in the carcinomas with lymph node metastasis than in those without metastasis (P < 0.05) or normal control (P < 0.01). Quantitative RT-PCR for membrane-types 1, 2 and 3 MMPs (MT1, 2 and 3-MMPs), which activate proMMP-2 in vitro, demonstrated that MT1-MMP is predominantly expressed in the carcinoma tissues, and the expression level is significantly
higher in the carcinomas with lymph node metastasis than in those without metastasis (P < 0.05) or the control samples (P < 0.05). Although MT2-MMP and MT3-MMP were detected in approximately 30% of the carcinoma cases, their expression levels
were extremely lower compared with that of MT1-MMP. There was a direct correlation between the MT1-MMP expression level and
proMMP-2 activation ratio (r = 0.62, P < 0.01). In situ hybridization and immunohistochemistry indicated that carcinoma cells and stromal cells adjacent to carcinoma cell nests
express MT1-MMP transcripts and protein. MMP-2 and TIMP-2 were also immunolocalized to the carcinoma cells in the carcinoma
samples. By in situ zymography, gelatinolytic activity was demonstrated in the carcinoma cell nests and abolished by the treatment with an MMP
inhibitor, BB94. These results suggest that among seven different MMPs, the production of proMMP-2 and its activation mediated
by MT1-MMP play an important role in the cervical lymph node metastasis of the human oral squamous cell carcinomas.
Clinical and Experimental Metastasis 04/2012; 18(2):179-188. · 3.52 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The so-called sol-gel technique has been shown to be a template-free, efficient way to create functional porous silica materials having uniform micropores. This appears to be closely linked with a postulation that the formation of weakly branched polymer-like aggregates in a precursor solution is a key to the uniform micropore generation. However, how such a polymer-like structure can precisely be controlled, and further, how the generated low-fractal dimension solution structure is imprinted on the solid silica materials still remain elusive. Here we present fabrication of microporous silica from tetramethyl orthosilicate (TMOS) using a recently developed catalytic sol-gel process based on a nonionic hydroxyacetone (HA) catalyst. Small angle X-ray scattering (SAXS), nitrogen adsorption porosimetry, and transmission electron microscope (TEM) allowed us to observe the whole structural evolution, ranging from polymer-like aggregates in the precursor solution to agglomeration with heat treatment and microporous morphology of silica powders after drying and hydrolysis. Using the HA catalyst with short chain monohydric alcohols (methanol or ethanol) in the precursor solution, polymer-like aggregates having microscopic correlation length (or mesh-size) < 2 nm and low fractal dimensions ∼2, which is identical to that of an ideal coil polymer, can selectively be synthesized, yielding the uniform micropores with diameters <2 nm in the solid materials. In contrast, the absence of HA or substitution of 1-propanol led to considerably different scattering behavior reflecting the particle-like aggregate formation in the precursor solution, which resulted in the formation of mesopores (diameter >2 nm) in the solid product due to apertures between the particle-like aggregates. The data demonstrate that the extremely fine porous silica architecture comes essentially from a gaussian polymer-like nature of the silica aggregates in the precursor having the microscopic mesh-size and their successful imprint on the solid product. The result offers a general but significantly efficient route to creating precisely designed fine porous silica materials under mild condition that serve as low refractive index and efficient thermal insulation materials in their practical applications.
The Journal of Physical Chemistry B 06/2011; 115(30):9369-78. · 3.70 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A microporous silica thin film with low refractive index (low-n) of 1.27 and high Young's modulus of 19.5 GPa was obtained by sol-gel synthesis using hydroxyacetone catalyst with tetramethyl orthosilicate and water in ethanol. Transmission electron microscope images and nitrogen adsorption-desorption measurements showed that the pores in the synthesized silica were <1 nm in diameter. Unlike many other microporous synthesis methods, our method did not require sacrificial reagents as templates. This allowed low-temperature fabrication of high-strength low-n silica.
ACS Applied Materials & Interfaces 10/2010; 2(11):3128-33. · 4.53 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Highly dispersed ternary PtRuRh/C anode catalysts for direct methanol fuel cells were prepared with various contents and their electro-catalytic activities towards methanol oxidation at 25°C and 60°C were examined to investigate the influence of the catalyst composition. Electrocatalysts were prepared by a co-impregnation method using ethanolic solutions of metal precursors and carbon black followed by pyrolysis under reducing conditions. X-ray diffraction analysis revealed that the fcc peaks shifted to higher diffraction angles with increasing Rh content, indicating the alloying of Rh into the fcc structure. In terms of the mass specific current density, the activity towards methanol oxidation differed significantly depending on the catalysts composition and cell temperature. The catalyst prepared at a ratio of Pt:Ru:Rh=1:1:2 exhibited the highest activity at 60°C of 155A (g-Pt)−1 at 0.5V vs. RHE.
Journal of Applied Electrochemistry 01/2006; 36(10):1117-1125. · 1.75 Impact Factor
-
Electrochemical and Solid State Letters - ELECTROCHEM SOLID STATE LETT. 01/2006; 9(7).
-
[show abstract]
[hide abstract]
ABSTRACT: Electrochemical impedance spectroscopy was conducted on a series of hydrous ruthenium oxides, RuO(2).xH(2)O, (x = 0.5, 0.3, 0) and a layered ruthenic acid hydrate (H(0.2)RuO(2.1).nH(2)O) in order to evaluate their protonic and electronic conduction. The capacitor response frequency was observed at lower frequency for RuO(2).xH(2)O with higher water content, which was suggested to be due to electrolyte exhaustion within the film and/or utilization of hydrated interparticle micropores that have high ionic resistance. Analysis of the impedance data indicated that the charge-transfer resistance through the film is not significantly affected by the water content in RuO(2).xH(2)O, and the capacitor frequency response is dominated by the protonic conduction. The capacitor response frequency of layered H(0.2)RuO(2.1).nH(2)O was comparable to RuO(2).0.5H(2)O. The high specific capacitance at low frequency for layered H(0.2)RuO(2.1).nH(2)O is attributed to the utilization of the expandable hydrous interlayer, which accounts for the ionic conduction. The present results demonstrate the importance of hydrous regions (either interparticle or interlayer) to allow appreciable protonic conduction for high energy and high power electrochemical capacitors.
The Journal of Physical Chemistry B 05/2005; 109(15):7330-8. · 3.70 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A titania-based self-standing film with high transparency and flexibility was successfully prepared via a sol-gel process, in which a titanium tetraisopropoxide/isostearate complex (precursor), n-hexylammonium isostearate (catalyst), and o-xylene (solvent) were used. The sol obtained by the sol-gel reaction was floated on a water surface to form an unsupported film. This film was composed of a titania/isostearate nanocomposite with ordered layer structure. The basal spacings of the nanocomposites depended on the chain length of the carboxylate modifier.
Journal of Materials Research. 04/2005; 20(05):1308 - 1315.
-
Bulletin of The Chemical Society of Japan - BULL CHEM SOC JPN. 01/2005; 78(4):633-637.
-
[show abstract]
[hide abstract]
ABSTRACT: A hydrous ruthenic acid
possessing a layered structure with a crystalline framework was prepared by proton exchange of a layered potassium ruthenate.
Its electrochemical capacitor behavior was studied by cyclic voltammetry in various electrolytes. Specific capacitance up
to 390 F
at a scan rate of 50 mV s−1, which is a ten-fold increase compared to conventional anhydrous
was obtained using layered ruthenic acid hydrate in 0.5 M
electrolyte. Slightly lower values were obtained for 1 M
and 1 M KOH electrolytes. The difference in the specific capacitance of anhydrous ruthenium oxide, hydrous ruthenium oxide,
hydrous ruthenic acid, and restacked ruthenic acid nanosheets in the various electrolytes is discussed. © 2004 The Electrochemical
Society. All rights reserved.
Journal of The Electrochemical Society. 07/2004; 151(8):A1181-A1187.
-
Angewandte Chemie International Edition 10/2003; 42(34):4092-6. · 13.45 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Well-homogenized PtRu/C electrocatalysts possessing high specific activity for methanol electro-oxidation were prepared by a co-impregnation method from carbon black and ethanolic solutions of Pt(NH3)2(NO2)2 and RuNO(NO3)
x
. The specific activity for methanol electro-oxidation increased with an increase in the PtRu particle size. A similar size effect was observed for Pt/C electrocatalysts. The size effect was discussed by considering a model catalyst method.
Catalysis Surveys from Asia 03/2003; 7(1):21-29. · 1.90 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Matrix metalloproteinase (MMP)-2 and -9 degrade type IV collagen, which is one of the major components of the basement membrane in normal tissue and expressed in the surroundings of the cancer nest in squamous cell carcinoma. The degeneration of type IV collagen is an essential step in the metastasis to lymph nodes and distant organs. In this study, we examined MMP-2 and -9 levels of cancer tissue and serum obtained from patients with head and neck squamous cell carcinoma (HNSCC) in order to evaluate the relationship between the clinicopathologic features and MMPs. We examined the production of MMP-2 and -9 in cancer tissue homogenates of 73 patients who had HNSCC and the serum MMP levels of 16 patients with HNSCC and 8 healthy volunteers. We also studied the localization of MMP-2 in the carcinoma using an immunohistochemical approach. The concentrations of MMP-2 and -9 in the tissue homogenates and serum were measured by means of a sandwich enzyme immunoassay using a monoclonal antibody. Immunohistochemical analyses were performed with monoclonal antibody to MMP-2. The concentration of MMP-2 in the tumor tissue homogenates was unrelated to tumor size, but that in patients with lymph node metastases was significantly higher than in those without lymph node metastases. The concentration of MMP-9 was unrelated to lymph node metastasis and tumor size. The levels of both MMP-2 and -9 in serum were unrelated to lymph node metastasis. Immunohistochemistry indicated that MMP-2 was mainly expressed in cancer cells. Because MMP-2 degrades type IV collagen, the level of MMP-2 in carcinomas may be a useful indicator of the degree of invasion and metastasis.
Acta Oto-Laryngologica 02/2002; 122(1):101-6. · 1.08 Impact Factor
-
Chemical Communications - CHEM COMMUN. 01/2001;
-
[show abstract]
[hide abstract]
ABSTRACT: Catalysis in a sol−gel process of titanium alkoxide was switched off to control the size of sheetlike particles of a resulting titanium oxide. The oxide growth was suspended by adding acetic acid, which regulated the catalytic activity of ammonium acetate. An ultraviolet−visible absorption band depended on the size of sheetlike particles. A lower energy region appeared for the larger size (>1 μm) of sheetlike particles but not for the smaller one. It is probably due to a bridging bidentate of acetate on the flat surface of titanium oxide particles.
02/2000;
-
[show abstract]
[hide abstract]
ABSTRACT: Membrane type 3 matrix metalloproteinase (MT3-MMP), an activator for the zymogen of MMP-2 (proMMP-2, or progelatinase A), is known to be expressed in human placenta, brain, lung and rat vascular smooth muscle cells, but information about its biochemical properties is limited. In the present study, we expressed and purified a truncated form of MT3-MMP lacking the transmembrane and intracytoplasmic domain (ΔMT3) and characterized the enzyme biochemically. ΔMT3 digested type III collagen into characteristic 3/4- and 1/4-fragments by cleaving the Gly781-Ile782 and Gly784-Ile785 bonds of α1(III) chains. Although ΔMT3 did not have such an activity against type I collagen, it attacked the Gly4-Ile5 bond of the triple helical portion of α2(I) chains, leading to removal of the crosslink containing N-terminal telopeptides. By quantitative analyses of the activities of ΔMT3 and a similar deletion mutant of MT1-MMP (ΔMT1), ΔMT3 was approximately fivefold more efficient at cleaving type III collagen. ΔMT3 also digested cartilage proteoglycan, gelatin, fibronectin, vitronectin, laminin-1, α1-proteinase inhibitor and α2-macroglobulin into almost identical fragments to those given by ΔMT1, although carboxymethylated transferrin digestion by ΔMT3 generated some extra fragments. The activity of ΔMT3 was inhibited by tissue inhibitor of metalloproteinases-2 (TIMP-2) and TIMP-3 in a 1 : 1 stoichiometry, but not by TIMP-1. ProMMP-2 was partially activated by ΔMT3 to give the intermediate form. These results indicate that, like MT1-MMP, MT3-MMP exhibits proteolytic activities against a wide range of extracellular matrix molecules. However, differences in the proMMP-2 activation and tissue distribution suggest that MT3-MMP and MT1-MMP play different roles in the pathophysiological digestion of extracellular matrix.
European Journal of Biochemistry. 05/1999; 262(3):907 - 914.
-
[show abstract]
[hide abstract]
ABSTRACT: The sol−gel process from titanium alkoxide monomer to titanium oxide polymer was remarkably enhanced by salt catalysts containing basic anions and acidic cations. An ammonium carbonate catalyst promoted the precipitation of spherical titanium oxide particles at low concentrations of titanium alkoxide and water at room temperature. Dehydrative polycondensation in the sol−gel process involves both deprotonation and dehydroxylation, and the carbonate anion enhanced the deprotonation as a base catalyst while the ammonium cation enhanced the dehydroxylation as an acid catalyst. If the ammonium acetate catalyst was added, the monolithic titanium oxide gel which consists of sheetlike titanium oxide particles was formed. The acetate anion acted not only as the catalyst for the dehydrative polycondensation but also as a ligand coordinating to titanium for capping the polycondensation sites, resulting in planar titanium oxide particles.
03/1999;
-
Chemistry Letters - CHEM LETT. 01/1999;
