Co-reporter:Suzuko Yamazaki;Kohei Watanabe
Industrial & Engineering Chemistry Research August 20, 2014 Volume 53(Issue 33) pp:13046-13057
Publication Date(Web):2017-2-22
DOI:10.1021/ie5018817
The surface interactions between xanthene (XN) dyes, including rhodamine B, rhodamine 3B, rhodamine 19, rhodamine 6G, rhodamine 110, and rhodamine 123, and tungsten(VI) oxide (WO3) colloid particles were investigated. These XN dyes were strongly adsorbed as a monolayer onto the WO3 surface via the electrostatic interaction between their peripheral cationic amino substituents and negatively surface-charged WO3 colloid particles, and most of the ones adsorbed eventually formed stable π-stacked dimers. The geometry of dimers formed on the WO3 colloid surface is discussed on the basis of the molecular exciton theory framework. Cationic XN dyes formed the approximately ideal face-to-face H-dimers on the WO3 colloid surface, whereas zwitterionic ones had a higher tendency to form the oblique J-dimers. Additionally, we have experimentally demonstrated the possibility of pH-induced switching between H- and J-aggregation modes of the XN dye’s dimers formed on the WO3 colloid surface. The findings lead to a better understanding of organic dye’s adsorption/aggregation behaviors on the metal oxide surface.
Co-reporter:Kenta Adachi, Masataka Tokushige, Kaoru Omata, Suzuko Yamazaki, and Yoshiaki Iwadate
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 22) pp:14019-14028
Publication Date(Web):May 9, 2016
DOI:10.1021/acsami.6b04115
Silicon oxycarbide/silica composites with well-dispersed tungsten(VI) oxide (WO3) nanoparticles were obtained as transparent hybrid xerogels via an acid-catalyzed sol–gel process (hydrolysis/condensation polymerization) of 3-(triethoxysilyl)propyl methacrylate (TESPMA) and tetraethoxysilane (TEOS). The self-diffusion mechanism of alkali-metal cations and the kinetics of the photochromic coloration process in the WO3/TESPMA/TEOS hybrid xerogel systems have been systematically investigated. Under continuous UV illumination, a gradual color change (colorless → blue) corresponding to the reduction of W6+ into W5+ states in WO3 nanoparticles can be confirmed from the WO3/TESPMA/TEOS hybrid xerogels containing alkali-metal sulfates, although no coloration of the hybrid xerogel without alkali-metal sulfate was observed. The coloration behavior depended exclusively on a variety of alkali-metal cations present in the hybrid xerogel system. Furthermore, a detailed analysis of the self-diffusion mechanism confirmed that the alkali-metal cations electrostatically interact with a layer of unreacted silanol groups on the TESPMA/TEOS matrix surface, and subsequently pass through the interconnected pore network of the hybrid xerogel. More interestingly, in the context of an Arrhenius analysis, we found a good coincidence between the activation energies for alkali-metal cation self-diffusion and UV-induced coloration in the WO3/TESPMA/TEOS hybrid xerogel system containing the corresponding alkali-metal sulfate. It is experimentally obvious that the photochromic properties are dominated by the diffusion process of alkali-metal cations in the WO3/TESPMA/TEOS hybrid xerogel system. Such hybrid materials with cation-controlled photochromic properties will show promising prospects in applications demanding energy-efficient “smart windows” and “smart glasses”.
Co-reporter:Kenta Adachi;Shoko Toyomura;Yuko Miyakuni;Suzuko Yamazaki;Kensuke Honda;Tomoyuki Hirano
Polymers for Advanced Technologies 2015 Volume 26( Issue 6) pp:597-605
Publication Date(Web):
DOI:10.1002/pat.3491
The catalytic performances of several bis(acetylacetonato)metal complexes [Cu(acac)2, Zn(acac)2, TiO(acac)2, VO(acac)2, MoO2(acac)2, and WO2(acac)2] were investigated for the crosslinking reaction via transesterifications in the ethylene-vinyl acetate copolymer/tetraethoxysilane (EVA/TEOS) composite system by means of dynamic attenuated total reflectance Fourier transform infrared, solvent swelling, and solid-state 29Si cross polarization/magic angle spinning nuclear magnetic resonance techniques. Results of the kinetic examination revealed that MoO2(acac)2 and WO2(acac)2 exhibited a higher catalytic activity than di-n-butyltin(IV) oxide, which is a catalyst most commonly used for the transesterification process in polymer system, but has a toxic effect on the environmental health. And furthermore, the crosslink density and final siloxane network structure of crosslinked EVA/TEOS composites are found to be greatly correlated with the catalyst used. On the basis of the SN2-Si pathway, a plausible catalytic mechanism of MoO2(acac)2 and WO2(acac)2 was proposed for the crosslinking reaction via transesterifications of the vinyl acetate moieties in EVA backbone with the ethoxysilane groups in one TEOS molecule. The findings in this study may fill the blank in the high performance and environmentally friendly catalyst in the field of the crosslinking reactions in polymer system and provide useful clue for other transesterifications. Copyright © 2015 John Wiley & Sons, Ltd.
Co-reporter:Naoya Kanetada, Chiyoe Matsumura, Suzuko Yamazaki, and Kenta Adachi
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 24) pp:12991
Publication Date(Web):November 20, 2013
DOI:10.1021/am403751t
The adsorption and aggregation behaviors of the cationic porphyrin derivatives such as 5,10,15,20-tetrakis(4-pyridyl)porphyrin [TPyP], 5,10,15,20-tetrakis(N-methyl-4-pyridyl)porphyrin [TMPyP], 5,10,15,20-tetrakis(N-ethyl-4-pyridyl)porphyrin [TEPyP], and 5,10,15,20-tetrakis(N-n-propyl-4-pyridyl)porphyrin [TPPyP] (hereafter called “TPyP derivatives”) in the tungsten(VI) oxide (WO3) colloid aqueous solution at weak acidic pH were studied by UV–vis spectroscopy. The TPyP derivatives were strongly adsorbed as monolayer onto the WO3 surface via the electrostatic interaction between their peripheral cationic substituents and negatively surface-charged WO3 colloid particles, and most of the ones adsorbed eventually formed J-type dimers aligned in the head-to-tail fashion. These different dimerization states were effectively analyzed by the change of ratios among the intensities of exciton split Soret bands (H- and J-bands). Judging from the exciton coupling theory and adsorption measurements, we concluded that the J-dimer geometry of the TPyP derivatives adsorbed on the WO3 colloid particle surface is strongly dependent on the presence and difference of peripheral substituents. The results described here indicate a new and promising way of designing surface supramolecular structures combination of two principles, the self-association of organic dyes, and the steric repulsive interaction between the peripheral substituents and the inorganic semiconductor surfaces.Keywords: adsorption; aggregation; porphyrin; self-organization; tungsten oxide;
Co-reporter:Shohei Tanaka, Kenta Adachi and Suzuko Yamazaki
Analyst 2013 vol. 138(Issue 9) pp:2536-2539
Publication Date(Web):25 Feb 2013
DOI:10.1039/C3AN36650B
The enhanced photochromic behaviors of the L-phenylalanine (Phe)–tungsten(VI) oxide (WO3) colloid binary aqueous solution have been investigated by means of UV-vis absorption spectrometry. The phenomena provided a potential use of the WO3 nanoparticles as a colorimetric probe for sensitive “label-free” detection of Phe.
Co-reporter:Kenta Adachi, Shohei Tanaka, Suzuko Yamazaki, Hideaki Takechi, Satoshi Tsukahara and Hitoshi Watarai
New Journal of Chemistry 2012 vol. 36(Issue 11) pp:2167-2170
Publication Date(Web):18 Jul 2012
DOI:10.1039/C2NJ40415J
In the methylene blue (MB)–phenylalanine (Phe)–tungsten(VI) oxide (WO3) colloid ternary aqueous solution, the MB H-aggregates, which could recognize the chirality of D- and L-Phe, were formed and investigated by means of UV-Vis absorption and CD spectroscopy. These results demonstrate a chirality transfer and amplification from only the pre-adsorbed Phe molecules to MB aggregates formed on the WO3 colloid surface via non-covalent interactions.
Co-reporter:Kenta Adachi, Tomohiro Mita, Shohei Tanaka, Kensuke Honda, Suzuko Yamazaki, Masaharu Nakayama, Takeyoshi Goto and Hitoshi Watarai
RSC Advances 2012 vol. 2(Issue 5) pp:2128-2136
Publication Date(Web):18 Jan 2012
DOI:10.1039/C2RA00217E
The nanostructured tungsten(VI) oxide (WO3)/cellulose derivatives (cellulose (CE) and triacetyl cellulose (TACE)) hybrid films were prepared by a solution-dipping adsorption process, and their structure and optical properties have been investigated. Various techniques, including adsorption isotherm, transmission electron microscopy (TEM), X-ray diffraction (XRD), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX), in situUV-Vis absorption, and in situ total internal reflection Raman spectroscopy, were used for the characterization of the WO3/CE and WO3/TACE hybrid materials. Under UV irradiation, the photochromism (colorless → blue) was confirmed from the WO3/CE hybrid film, although no coloration of the WO3/TACE hybrid film was observed. This distinct difference in the coloration suggested that the interfacial interaction between hydroxyl groups present on the surface of the CE substrate and WO3 nanoparticlesviahydrogen bonding plays a major role in the enhancement of photochromism in the WO3/CE hybrid system. Moreover, the joint evidence in in situUV-Vis absorption and in situ total internal reflection Raman studies clearly revealed that the photogenerated coloration is related to a partial reduction of W6+ cations into W5+ cations in the WO3/CE hybrid film. The findings in this study have great implications for the development of the novel green-functional inorganic/organic hybrid materials in optical devices.
Co-reporter:Kenta Adachi;Kensuke Honda;Suzuko Yamazaki;Tomoyuki Hirano;Hiroshi Kurokawa;Akinobu Wakabayashi;Paul H. Kasai;Katsuhiko Nakamae;Hitoshi Iwabuki;Koji Murakami
Polymer Engineering & Science 2011 Volume 51( Issue 4) pp:632-640
Publication Date(Web):
DOI:10.1002/pen.21856
Abstract
The vinyltrimethoxysilane-grafted ethylene-propylene copolymer/trifunctional methoxysilane (EPR-g-VTMS/RTMS) composites were prepared via in situ silica sol–gel reactions. Five trifunctional methoxysilane compounds (n-hexyltrimethoxysilane, n-decyltrimethoxysilane, n-tetradecyltrimethoxysilane, n-octadecyltrimethoxysilane, and phenyltrimethoxysilane) have been selected for this study. The water-cross-linked EPR-g-VTMS/RTMS composites were characterized by attenuated total reflectance-Fourier transform infrared spectroscopy, gel content, solid-state 29Si CP/MAS NMR, wide-angle x-ray scattering, tensile strength, and field emission scanning electron microscopy measurements. The type of RTMS additive has a substantial influence on the nature of siloxane band networks and eventually the mechanical tensile properties. This finding suggests that the interaction and/or entanglement between the EPR-g-VTMS matrix and the substituent of the RTMS additives are crucial for the modifying mechanical properties. Moreover, for the water-cross-linked EPR-g-VTMS/CnTMS (n = 6, 10, 14, and 18) composites, the joint evidence provided by attenuated total reflectance-Fourier transform infrared spectroscopy, 29Si CP/MAS NMR, and wide-angle x-ray scattering results suggested the formation of ladder-type poly(n-alkyl silsesquioxane)s and the presence of the highly ordered structure with a thickness equal to the length of two n-alkyl groups in all-trans conformation. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.
Co-reporter:Kenta Adachi;Tomoyuki Hirano;Paul H Kasai;Katsuhiko Nakamae;Hitoshi Iwabuki;Koji Murakami
Polymer International 2010 Volume 59( Issue 4) pp:510-516
Publication Date(Web):
DOI:10.1002/pi.2729
Abstract
In situ silica sol–gel-derived organic–inorganic hybrid materials, which comprise a vinyltrimethoxysilane-grafted ethylene–propylene copolymer (EPR-g-VTMS) and n-hexyltrimethoxysilane (HTMS), were successfully prepared in the presence of an organic acid and base catalyst. Benzenesulfonic acid and aniline were selected as the organic acid and base catalyst, respectively, to examine the progress and effect of progressive changes in the silane water-crosslinking reaction of EPR-g-VTMS/HTMS composites. The water-crosslinked EPR-g-VTMS/HTMS composites were characterized by means of attenuated total reflectance Fourier transform infrared spectroscopy, gel content, solid-state 29Si cross-polarization/magic-angle spinning NMR, wide-angle X-ray scattering, tensile strength and field-emission scanning electron microscopy measurements. These results revealed that the type of catalyst has a substantial influence on the nature of siloxane bonds and eventually the physical tensile properties of the water-crosslinked EPR-g-VTMS/HTMS composites, which can be explained mainly from knowledge of the traditional acid- and base-catalyzed silica sol–gel reaction. Moreover, an in-depth analysis of the aniline-catalyzed composites indicated the formation of ladder-type poly(n-hexylsilsesquioxane)s and the presence of a highly ordered structure with a thickness equal to the length of two n-hexyl groups in all-trans conformation. We demonstrate potential for the future design of highly ordered silicate-based organic–inorganic hybrid nanocomposites. Copyright © 2009 Society of Chemical Industry
Co-reporter:Kenta Adachi, Tomohiro Mita, Taiki Yamate, Suzuko Yamazaki, Hideaki Takechi and Hitoshi Watarai
Langmuir 2010 Volume 26(Issue 1) pp:117-125
Publication Date(Web):August 20, 2009
DOI:10.1021/la902174s
The monomer−aggregate equilibrium of four phenothiazine (PN) dyes, containing thionine (TH), methylene blue (MB), new methylene blue (NMB), and 1,9-dimethylmethylene blue (DMB), in the tungsten(VI) oxide (WO3) nanocolloid solution has been investigated by means of UV−vis spectroscopy. Addition of PN dye into the WO3 nanocolloid solution brought about significant changes in the absorption spectrum, suggesting the formation of H-type (face-to-face fashion) trimer on the WO3 nanocolloid surface. The adsorptivity of PN dyes onto the WO3 nanocolloid surface was diminished by the raising the ionic strength, indicating the evidence of the electrostatic interaction between cationic PN dye and negatively charged WO3 nanocolloids. The detail analysis of each spectral data provided insight into the effect of molecular structure of PN dyes on the adsorption and aggregation behaviors on the WO3 nanocolloid surface. Moreover, in situ measurement of PN dye aggregation using the centrifugal liquid membrane (CLM) technique revealed that the aggregation of PN dyes on the WO3 nanocolloid surface proceeded in a two-step three-stage (monomer → dimer → trimer) formation. The aggregation mechanism of PN dyes on the WO3 nanocolloid surface was discussed on the basis of Kasha’s exciton theory.
Co-reporter:Kenta Adachi;Tomoyuki Hirano
Journal of Sol-Gel Science and Technology 2009 Volume 49( Issue 2) pp:186-195
Publication Date(Web):2009 February
DOI:10.1007/s10971-008-1857-2
Catalytic effects of Brönsted acid on the early kinetics of water-crosslinking reaction in the vinyltrimethoxysilane-grafted ethylene–propylene copolymer (EPR-g-VTMS) system were investigated by means of an attenuated total reflectance-Fourier transform infrared (ATR-FTIR) technique and gel fraction measurements. Four sulfonic acids with different substituent, including methanesulfonic acid (C1SO3H), 1-propanesulfonic acid (C3SO3H), 1-pentanesulfonic acid (C5SO3H), and dodecylbenzenesulfonic acid (C12PhSO3H), were selected to examine the progress and effect of progressive changes in the silane water-crosslinked network structure in comparison with a primary amine (n-octadecylamine, Lewis base). From the kinetic analysis using Arrhenius equation, we found that the frequency factors for both hydrolysis (ATR-FTIR) and condensation step (gel content) of EPR-g-VTMS decreased in the order of C1SO3H > C3SO3H > C5SO3H > C12PhSO3H, while the activation energy values for each reaction did not differ significantly. These relationships can be explained mainly on the basis of the diffusion factors of the sulfonic acids in EPR-g-VTMS system. Moreover, the stress–strain curve comparison between water-crosslinked EPR-g-VTMS samples containing sulfonic acid and amine compound clearly indicated the difference in their tensile properties as a result of the catalyst variation; the use of sulfonic acid as water-crosslinking catalyst eventually achieves to the soft and tough water-crosslinked EPR-g-VTMS, while the hard and strong one was produced using amine catalyst. Not only the catalytic activity but also the type of the catalyst has eventually significant effects upon the physical properties of the water-crosslinked EPR-g-VTMS.
![3,6-diamino-9-[2-(methoxycarbonyl)phenyl]xanthylium chloride](/data/chemimg/622800/62669-70-9.png)
![3,6-diamino-9-[2-(methoxycarbonyl)phenyl]xanthylium chloride](/data/chemimg/622800/62669-70-9_b.png)
