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Shinsuke Takagi - One of the best experts on this subject based on the ideXlab platform.
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Structure resembling effect of Clay Surface on photochemical properties of meso-phenyl or pyridyl-substituted monocationic antimony(V) porphyrin derivatives
RSC Advances, 2020Co-Authors: Takamasa Tsukamoto, Tetsuya Shimada, Shinsuke TakagiAbstract:Four types of meso-phenyl or pyridyl-substituted monocationic antimony(V) porphyrin derivatives (SbVPors)—5,10,15,20-tetraphenyl; 5,10,15-triphenyl-20-mono(4-pyridyl); 5,15-diphenyl-10,20-di(4-pyridyl); and 5,10,15,20-tetra(4-pyridyl)porphyrinato dihydroxo antimony(V) chloride—with different hydrophobicities were synthesised, and their photochemical properties on anionic Clay were investigated. The absorption and fluorescence behaviour of the SbVPors were strongly affected by complex formation with Clay. Interestingly, the absorption transition probabilities and fluorescence quantum yields of the SbVPors prominently increased on the Clay Surface. The more hydrophobic SbVPor showed greater absorption transition probability increase and fluorescence quantum yield enhancement. These unique effects of the highly flat Clay Surface on the photochemical behaviour of SbVPor were discussed mainly from the viewpoint of transition probability, by using the potential energy curves of SbVPor with and without Clay. For the more hydrophobic SbVPor, the molecular structure of the ground and excited states on the Clay Surface tended to become similar because of the strong hydrophobic interaction between porphyrin and the Clay Surface, i.e. the ‘structure resembling effect’. This effect induces a change in the transition probabilities.
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Adsorption and stacking behaviour of zwitterionic porphyrin on the Clay Surface
Clay Minerals, 2020Co-Authors: T. Eyama, Takuya Fujimura, Tetsuya Shimada, Haruo Inoue, Shinsuke Takagi, Y. Yogo, Takamasa Tsukamoto, Dai Masui, Hiroshi Tachibana, John AdamsAbstract:AB ST R ACT : Zwitterionic porphyrin (tetrakis {4-(2-carboxyethyl)pyridinio}porphyrin (TPyCP)) with four pyridinium and carboxyl groups in the molecule was synthesized. The adsorption behaviour of TPyCP on the montmorillonite Clay Surface was examined in an aqueous colloidal solution. While the adsorption maximum lmax of TPyCP was 424 nm in water, it shifted to longer wavelengths on complex formation with Clay. The lmax on the exfoliated Clay Surface was 450 nm, and that in the stacked Clay sheets was 471 nm, respectively. Under alkaline conditions ([NaOH] = 2610 4 M), the stacking behaviour of the Clay was completely suppressed. It emerged that anionic parts in the porphyrin molecule can suppress the stacking of Clay sheets. Judging from the quantitative analysis, the maximum adsorption amount of TPyCP was 100% vs. cation exchange capacity (CEC) of the Clay. As the adsorption density of TPyCP increased, lmax shifted slightly to longer wavelengths due to the interactions between adjacent porphyrins. When the loading level of TPyCP was 200% vs. CEC, the stacking of TPyCP was indicated. The average stacking layer number was calculated to be 1.48. On the other hand, it is known that tetra cationic porphyrins without anionic parts do not form such stacking structures. Thus, it seems that zwitterionic porphyrin has the potential to form a three dimensional structure through electrostatic interactions between porphyrins on the Clay Surface.
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Energy transfer reaction of cationic porphyrin complexes on the Clay Surface: effect of sample preparation method
Research on Chemical Intermediates, 2020Co-Authors: Shinsuke Takagi, Tetsuya Shimada, Miharu Eguchi, Satoshi Hamatani, Haruo InoueAbstract:Photochemical energy transfer of non-aggregated cationic porphyrins on an anionic-type Clay (Smecton SA) Surface was investigated. The efficiency of energy transfer and excited-state quenching in the absence of energy transfer were evaluated at various loading levels of porphyrin on the Clay Surface and were found to be significantly affected by the loading level. As the latter increased, both energy transfer efficiency and excited-state quenching increased. Judging from the dependency of energy-transfer efficiency on the porphyrin loading level, a partially clustered structure, but without aggregation, of porphyrins on the Clay Surface is proposed.
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Thermodynamic study of the adsorption of acridinium derivatives on the Clay Surface
RSC Advances, 2020Co-Authors: Yuma Yoshida, Tetsuya Shimada, Tamao Ishida, Shinsuke TakagiAbstract:Thermodynamic studies indicate that van der Waals and hydrophobic interactions contribute to the adsorption of mono-cationic acridinium derivatives on the Clay Surface.
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Factors for the emission enhancement of dimidium in specific media such as in DNA and on a Clay Surface.
Physical Chemistry Chemical Physics, 2019Co-Authors: Ryosuke Nakazato, Tetsuya Shimada, Tamao Ishida, Keito Sano, Hiroyuki Ichihara, Shinsuke TakagiAbstract:Dimidium (3,8-diamino-5-methyl-6-phenylphenanthridinium: NH2PhP) is a well-known fluorophore as a DNA probe, although its fluorescence enhancement mechanism is not clear. In this study, we investigated the fluorescence enhancement mechanism of NH2PhP on a Clay Surface by observing the fluorescence behavior. Four systematically selected phenanthridinium derivatives (PDs): NH2PhP, 3,8-bisdimethylamino-5-methyl-6-phenylphenanthridinium (NMe2PhP), 5-methyl-6-phenylphenanthridinium (PhP) and 5-methylphenanthridinium (P) and synthetic Clay were used as guest and host materials, respectively. It was revealed that the suppression of hydrogen bonding with water (N–HOH or NH–OH2) is the dominant factor for the fluorescence enhancement on the Clay Surface for NH2PhP and NMe2PhP. In addition, judging from the fluorescence enhancement for NH2PhP, NMe2PhP and PhP and no fluorescence enhancement for P on the Clay Surface, the suppression of rotation of the phenyl ring was indicated to make a partial contribution to the fluorescence enhancement mechanism. Because the fluorescence enhancement behavior was quite similar on the Clay Surface and in DNA, the obtained results afford an important clue to discuss the fluorescence enhancement mechanism of NH2PhP in DNA.
Haruo Inoue - One of the best experts on this subject based on the ideXlab platform.
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Adsorption and stacking behaviour of zwitterionic porphyrin on the Clay Surface
Clay Minerals, 2020Co-Authors: T. Eyama, Takuya Fujimura, Tetsuya Shimada, Haruo Inoue, Shinsuke Takagi, Y. Yogo, Takamasa Tsukamoto, Dai Masui, Hiroshi Tachibana, John AdamsAbstract:AB ST R ACT : Zwitterionic porphyrin (tetrakis {4-(2-carboxyethyl)pyridinio}porphyrin (TPyCP)) with four pyridinium and carboxyl groups in the molecule was synthesized. The adsorption behaviour of TPyCP on the montmorillonite Clay Surface was examined in an aqueous colloidal solution. While the adsorption maximum lmax of TPyCP was 424 nm in water, it shifted to longer wavelengths on complex formation with Clay. The lmax on the exfoliated Clay Surface was 450 nm, and that in the stacked Clay sheets was 471 nm, respectively. Under alkaline conditions ([NaOH] = 2610 4 M), the stacking behaviour of the Clay was completely suppressed. It emerged that anionic parts in the porphyrin molecule can suppress the stacking of Clay sheets. Judging from the quantitative analysis, the maximum adsorption amount of TPyCP was 100% vs. cation exchange capacity (CEC) of the Clay. As the adsorption density of TPyCP increased, lmax shifted slightly to longer wavelengths due to the interactions between adjacent porphyrins. When the loading level of TPyCP was 200% vs. CEC, the stacking of TPyCP was indicated. The average stacking layer number was calculated to be 1.48. On the other hand, it is known that tetra cationic porphyrins without anionic parts do not form such stacking structures. Thus, it seems that zwitterionic porphyrin has the potential to form a three dimensional structure through electrostatic interactions between porphyrins on the Clay Surface.
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Energy transfer reaction of cationic porphyrin complexes on the Clay Surface: effect of sample preparation method
Research on Chemical Intermediates, 2020Co-Authors: Shinsuke Takagi, Tetsuya Shimada, Miharu Eguchi, Satoshi Hamatani, Haruo InoueAbstract:Photochemical energy transfer of non-aggregated cationic porphyrins on an anionic-type Clay (Smecton SA) Surface was investigated. The efficiency of energy transfer and excited-state quenching in the absence of energy transfer were evaluated at various loading levels of porphyrin on the Clay Surface and were found to be significantly affected by the loading level. As the latter increased, both energy transfer efficiency and excited-state quenching increased. Judging from the dependency of energy-transfer efficiency on the porphyrin loading level, a partially clustered structure, but without aggregation, of porphyrins on the Clay Surface is proposed.
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Microstructures of the Porphyrin/Viologen Monolayer on the Clay Surface: Segregation or Integration?
Journal of Physical Chemistry C, 2014Co-Authors: Saki Konno, Takuya Fujimura, Yuta Otani, Tetsuya Shimada, Haruo Inoue, Shinsuke TakagiAbstract:Microstructures of the porphyrin/viologen monolayer on an anionic Clay Surface (synthetic saponite) were investigated by the observation of photochemical behavior of porphyrin. Fluorescence behaviors of porphyrin–viologen–Clay complexes were observed by steady state and time-resolved fluorescence spectroscopy. Although fluorescence of porphyrin was effectively quenched by coadsorbed viologen on the Clay Surface, a part of the fluorescence of porphyrin was not quenched and remained even at high loading level of viologen. According to time-resolved fluorescence measurement, the decay profile of excited singlet porphyrin can be analyzed by two- or three-component fitting for porphyrin–viologen–Clay complexes. These results indicate that porphyrin and viologen adsorb with island (segregation) structure on the Clay Surface. The size of the island formed by porphyrin was quantitatively estimated for two kinds of porphyrins. It turned out that the porphyrin molecular structure affects the size of the island. It ...
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Role of Hydrophobic Interaction in Controlling the Orientation of Dicationic Porphyrins on Solid Surfaces
Journal of Physical Chemistry C, 2013Co-Authors: Miharu Eguchi, Tetsuya Shimada, Haruo Inoue, Donald A Tryk, Shinsuke TakagiAbstract:The adsorption orientational behavior of dicationic porphyrins on Clay Surfaces in various solvents was examined. Addition of aprotic solvents to the aqueous solution containing the Clay–porphyrin complex induced a large spectral shift to shorter wavelength. The blue shift turned out to be due to the orientation angle change of porphyrin, which leads to the relaxation of molecular flattening. From dichroic measurements on a waveguide, the orientation of the porphyrin was directly observed and found to be parallel to the Clay Surface in water and to be at a tilt angle of 68° with respect to the Clay Surface in DMF. A thermodynamic study of the porphyrin orientation on the Clay Surface was undertaken. This analysis showed that the parallel orientation of the porphyrin was stabilized mainly by the entropy term, and the tilted orientation was stabilized mainly by the enthalpy term. Furthermore, the effects of different organic solvents on porphyrin orientation on the Clay Surface were examined, and strong cor...
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Investigation of adsorption behavior and energy transfer of cationic porphyrins on Clay Surface at low loading levels by picosecond time-resolved fluorescence measurement
Research on Chemical Intermediates, 2012Co-Authors: Tetsuya Shimada, Haruo Inoue, Yohei Ishida, Satoshi Hamatani, Shingo Onodera, Shinsuke TakagiAbstract:Time-resolved fluorescence and steady-state spectroscopic measurements were performed with +4-charged cationic porphyrins adsorbed on an anionic-type Clay (Sumecton SA; SSA) Surface at a low molecular loading level (10 % vs. cation-exchange capacity of Clay) corresponding to an occupied area of ca 50 nm2 per molecule. Absorption spectra indicated no interaction between transition moments of the porphyrins on the Clay Surface. An efficient energy-transfer process from donor to acceptor porphyrin was observed on the Clay Surface even under low porphyrin loading conditions. The efficiency of energy transfer obtained from the steady-state measurement was 65 %. Real-time behavior of the porphyrins was successfully captured during energy transfer. The rate constant of the energy transfer obtained from time-resolved fluorescence measurements was found to be 5.3 × 108 s−1. According to the efficiency and the rate constant, it is proposed that the adsorbed porphyrins did not have a uniform and fixed distribution.
Tetsuya Shimada - One of the best experts on this subject based on the ideXlab platform.
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Energy transfer reaction of cationic porphyrin complexes on the Clay Surface: effect of sample preparation method
Research on Chemical Intermediates, 2020Co-Authors: Shinsuke Takagi, Tetsuya Shimada, Miharu Eguchi, Satoshi Hamatani, Haruo InoueAbstract:Photochemical energy transfer of non-aggregated cationic porphyrins on an anionic-type Clay (Smecton SA) Surface was investigated. The efficiency of energy transfer and excited-state quenching in the absence of energy transfer were evaluated at various loading levels of porphyrin on the Clay Surface and were found to be significantly affected by the loading level. As the latter increased, both energy transfer efficiency and excited-state quenching increased. Judging from the dependency of energy-transfer efficiency on the porphyrin loading level, a partially clustered structure, but without aggregation, of porphyrins on the Clay Surface is proposed.
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Adsorption and stacking behaviour of zwitterionic porphyrin on the Clay Surface
Clay Minerals, 2020Co-Authors: T. Eyama, Takuya Fujimura, Tetsuya Shimada, Haruo Inoue, Shinsuke Takagi, Y. Yogo, Takamasa Tsukamoto, Dai Masui, Hiroshi Tachibana, John AdamsAbstract:AB ST R ACT : Zwitterionic porphyrin (tetrakis {4-(2-carboxyethyl)pyridinio}porphyrin (TPyCP)) with four pyridinium and carboxyl groups in the molecule was synthesized. The adsorption behaviour of TPyCP on the montmorillonite Clay Surface was examined in an aqueous colloidal solution. While the adsorption maximum lmax of TPyCP was 424 nm in water, it shifted to longer wavelengths on complex formation with Clay. The lmax on the exfoliated Clay Surface was 450 nm, and that in the stacked Clay sheets was 471 nm, respectively. Under alkaline conditions ([NaOH] = 2610 4 M), the stacking behaviour of the Clay was completely suppressed. It emerged that anionic parts in the porphyrin molecule can suppress the stacking of Clay sheets. Judging from the quantitative analysis, the maximum adsorption amount of TPyCP was 100% vs. cation exchange capacity (CEC) of the Clay. As the adsorption density of TPyCP increased, lmax shifted slightly to longer wavelengths due to the interactions between adjacent porphyrins. When the loading level of TPyCP was 200% vs. CEC, the stacking of TPyCP was indicated. The average stacking layer number was calculated to be 1.48. On the other hand, it is known that tetra cationic porphyrins without anionic parts do not form such stacking structures. Thus, it seems that zwitterionic porphyrin has the potential to form a three dimensional structure through electrostatic interactions between porphyrins on the Clay Surface.
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Structure resembling effect of Clay Surface on photochemical properties of meso-phenyl or pyridyl-substituted monocationic antimony(V) porphyrin derivatives
RSC Advances, 2020Co-Authors: Takamasa Tsukamoto, Tetsuya Shimada, Shinsuke TakagiAbstract:Four types of meso-phenyl or pyridyl-substituted monocationic antimony(V) porphyrin derivatives (SbVPors)—5,10,15,20-tetraphenyl; 5,10,15-triphenyl-20-mono(4-pyridyl); 5,15-diphenyl-10,20-di(4-pyridyl); and 5,10,15,20-tetra(4-pyridyl)porphyrinato dihydroxo antimony(V) chloride—with different hydrophobicities were synthesised, and their photochemical properties on anionic Clay were investigated. The absorption and fluorescence behaviour of the SbVPors were strongly affected by complex formation with Clay. Interestingly, the absorption transition probabilities and fluorescence quantum yields of the SbVPors prominently increased on the Clay Surface. The more hydrophobic SbVPor showed greater absorption transition probability increase and fluorescence quantum yield enhancement. These unique effects of the highly flat Clay Surface on the photochemical behaviour of SbVPor were discussed mainly from the viewpoint of transition probability, by using the potential energy curves of SbVPor with and without Clay. For the more hydrophobic SbVPor, the molecular structure of the ground and excited states on the Clay Surface tended to become similar because of the strong hydrophobic interaction between porphyrin and the Clay Surface, i.e. the ‘structure resembling effect’. This effect induces a change in the transition probabilities.
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Thermodynamic study of the adsorption of acridinium derivatives on the Clay Surface
RSC Advances, 2020Co-Authors: Yuma Yoshida, Tetsuya Shimada, Tamao Ishida, Shinsuke TakagiAbstract:Thermodynamic studies indicate that van der Waals and hydrophobic interactions contribute to the adsorption of mono-cationic acridinium derivatives on the Clay Surface.
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Factors for the emission enhancement of dimidium in specific media such as in DNA and on a Clay Surface.
Physical Chemistry Chemical Physics, 2019Co-Authors: Ryosuke Nakazato, Tetsuya Shimada, Tamao Ishida, Keito Sano, Hiroyuki Ichihara, Shinsuke TakagiAbstract:Dimidium (3,8-diamino-5-methyl-6-phenylphenanthridinium: NH2PhP) is a well-known fluorophore as a DNA probe, although its fluorescence enhancement mechanism is not clear. In this study, we investigated the fluorescence enhancement mechanism of NH2PhP on a Clay Surface by observing the fluorescence behavior. Four systematically selected phenanthridinium derivatives (PDs): NH2PhP, 3,8-bisdimethylamino-5-methyl-6-phenylphenanthridinium (NMe2PhP), 5-methyl-6-phenylphenanthridinium (PhP) and 5-methylphenanthridinium (P) and synthetic Clay were used as guest and host materials, respectively. It was revealed that the suppression of hydrogen bonding with water (N–HOH or NH–OH2) is the dominant factor for the fluorescence enhancement on the Clay Surface for NH2PhP and NMe2PhP. In addition, judging from the fluorescence enhancement for NH2PhP, NMe2PhP and PhP and no fluorescence enhancement for P on the Clay Surface, the suppression of rotation of the phenyl ring was indicated to make a partial contribution to the fluorescence enhancement mechanism. Because the fluorescence enhancement behavior was quite similar on the Clay Surface and in DNA, the obtained results afford an important clue to discuss the fluorescence enhancement mechanism of NH2PhP in DNA.
Thomas J Pinnavaia - One of the best experts on this subject based on the ideXlab platform.
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thermoset epoxy Clay nanocomposites the dual role of α ω diamines as Clay Surface modifiers and polymer curing agents
Journal of Solid State Chemistry, 2002Co-Authors: Costas S Triantafillidis, Peter C Lebaron, Thomas J PinnavaiaAbstract:Diprotonated forms of polyoxypropylene diamines of the type α,ω-[NH3CHCH3CH2(OCH2CHCH3)xNH32+ with x=2.6, 5.6, and 33.1, have been intercalated into montmorillonite and fluorohectorite Clays and subsequently evaluated for the formation of glassy epoxy–Clay nanocomposites. The intercalated onium ions functioned concomitantly as a Clay Surface modifier, intragallery polymerization catalyst, and curing agent. Depending on the chain length of the diamine, different orientations of the propylene oxide chains were adopted in the Clay galleries, resulting in basal spacings from ∼14 A (lateral monolayer, x=2.6) to ∼45 A (folded structure, x=33.1). The initial Clay basal spacings were correlated with the formation of intercalated and exfoliated Clay–epoxy nanocomposites with improved mechanical properties and high thermal stabilities. In comparison to Clay–monoamine intercalates, the use of diamine intercalates greatly reduced the plasticizing effect of the alkyl chains on the polymer matrix, resulting in improved mechanical properties while at the same time reducing the cost and time needed for nanocomposite fabrication.
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Thermoset Epoxy–Clay Nanocomposites: The Dual Role of α,ω-Diamines as Clay Surface Modifiers and Polymer Curing Agents
Journal of Solid State Chemistry, 2002Co-Authors: Costas S Triantafillidis, Peter C Lebaron, Thomas J PinnavaiaAbstract:Diprotonated forms of polyoxypropylene diamines of the type α,ω-[NH3CHCH3CH2(OCH2CHCH3)xNH32+ with x=2.6, 5.6, and 33.1, have been intercalated into montmorillonite and fluorohectorite Clays and subsequently evaluated for the formation of glassy epoxy–Clay nanocomposites. The intercalated onium ions functioned concomitantly as a Clay Surface modifier, intragallery polymerization catalyst, and curing agent. Depending on the chain length of the diamine, different orientations of the propylene oxide chains were adopted in the Clay galleries, resulting in basal spacings from ∼14 A (lateral monolayer, x=2.6) to ∼45 A (folded structure, x=33.1). The initial Clay basal spacings were correlated with the formation of intercalated and exfoliated Clay–epoxy nanocomposites with improved mechanical properties and high thermal stabilities. In comparison to Clay–monoamine intercalates, the use of diamine intercalates greatly reduced the plasticizing effect of the alkyl chains on the polymer matrix, resulting in improved mechanical properties while at the same time reducing the cost and time needed for nanocomposite fabrication.
Virginie Marry - One of the best experts on this subject based on the ideXlab platform.
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Solvation of complex Surfaces via molecular density functional theory.
The Journal of chemical physics, 2012Co-Authors: Maximilien Levesque, Virginie Marry, Rodolphe Vuilleumier, Benjamin Rotenberg, Guillaume Jeanmairet, Daniel BorgisAbstract:We show that classical molecular density functional theory, here in the homogeneous reference fluid approximation in which the functional is inferred from the properties of the bulk solvent, is a powerful new tool to study, at a fully molecular level, the solvation of complex Surfaces and interfaces by polar solvents. This implicit solvent method allows for the determination of structural, orientational, and energetic solvation properties that are on a par with all-atom molecular simulations performed for the same system, while reducing the computer time by two orders of magnitude. This is illustrated by the study of an atomistically-resolved Clay Surface composed of over a thousand atoms wetted by a molecular dipolar solvent. The high numerical efficiency of the method is exploited to carry a systematic analysis of the electrostatic and non-electrostatic components of the Surface-solvent interaction within the popular Clay Force Field (ClayFF). Solvent energetics and structure are found to depend weakly upon the atomic charges distribution of the Clay Surface, even for a rather polar solvent. We conclude on the consequences of such findings for force-field development.
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Structure and dynamics of water at a Clay Surface from molecular dynamics simulation.
Physical chemistry chemical physics : PCCP, 2008Co-Authors: Virginie Marry, Benjamin Rotenberg, Pierre TurqAbstract:We report a molecular dynamics study of the structure and dynamics of water at a Clay Surface. The negative charge of the Surface and the presence of Surface oxygen atoms perturbs water over two to three molecular layers, while the nature of the counterions (Na(+)or Cs(+)) has only a small effect. In the first molecular layer, approximately half of the water molecules are H-bonded to the Surface. We also analyze the H-bond network between Surface water molecules. The diffusion of water molecules along the Surface is slowed down compared to the bulk case. As far as the orientational order and dynamics of the water dipole are concerned, only the component normal to the Clay Surface is perturbed. We investigate the Surface H-bond formation and dissociation dynamics and their coupling to the release of molecules from the first molecular layer. We introduce a simple kinetic model in the spirit of Luzar and Chandler [Nature, 1996, 379, 55] to allow for a comparison with bulk water dynamics. This model semi-quantitatively reproduces the molecular simulation results and suggests that H-bond formation is faster with the Surface than in the bulk, while H-bond dissociation is slower.