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Tomoaki Hino - One of the best experts on this subject based on the ideXlab platform.
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SOLUBILITY OF MONOALKYL PHOPHATE IN WATER IN THE PRESENCE OF ARGININE AND TRITON, AND SOLUBILIZATION OF Methyl Yellow THROUGH THE MIXED MICELLE
Phosphorus Research Bulletin, 2008Co-Authors: Takeshi Murata, Tomoaki Hino, Satoru Ueno, Saburo ShimabayashiAbstract:Effects of arginine (Arg) and Triton such as Triton-X (TX) and Triton-N (TN) on the solubility of monoalkyl phosphoric acid (MAP) such as dodecyl (DP), myristyl (MP), and cetyl phosphoric acid (CP) in an aqueous phase were studied. Although these MAPs are scarcely soluble in water, their solubility at 70 oC increased with a concentration of Triton added. The effect of TN was stronger than that of TX. DP became soluble at room temperature when Arg was added up to the mixing ratio of Arg/DP = 3 in mole. MP and CP were hardly soluble yet in the presence of Arg alone while these became soluble after adding Triton together with Arg. Their acidic head group was ionized by Arg, resulting in an increase in its affinity for water. DP was soluble just after the ionization while MP and CP were soluble after the ionization and concomitant formation of the mixed micelle with the Triton added. Methyl Yellow, barely soluble in water, was solubilized after entrapment into the mixed micelle. Its solubility increased with a concentration and chain length of the MAP added as a solubilizing agent.
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Interaction and Complex Formation of Pluronic Polymers with Ionic Surfactants
Studies in Surface Science and Catalysis, 2007Co-Authors: Saburo Shimabayashi, Akihito Ichimori, Tomoaki HinoAbstract:ABSTRACT: Interaction of a pluronic polymer(Plu) with an ionic surfactant was studied. Specific behaviors of a solution of Plu mixed with an ionic surfactant, such as cloud point, relative viscosity, and solubilization of Methyl Yellow, were discussed, taking the binding isotherm into considerstion.
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Adsorption of Nonionic Surfactants, Triton X and Triton N, on Hydroxyapatite after Surface Modification with Sodium Dodecyl Sulfate in an Aqueous Phase
Studies in Surface Science and Catalysis, 2001Co-Authors: Saburo Shimabayashi, Masashi Hoshino, Takahisa Ohnishi, Tomoaki HinoAbstract:ABSTRACT Although Triton X-100 and Triton N, which are water-soluble nonionic surfactants, were scarcely adsorbed by HAP without SDS, these were adsorbed in the presence of SDS. On the other hand, Methyl Yellow, a water-insoluble dye, was also captured on the surface of HAP when HAP was treated with SDS. It was concluded that surface modification of HAP by SDS and hydrophobic interaction with SDS on the surface of HAP play important roles in the adsorption.
Rômulo A. Ando - One of the best experts on this subject based on the ideXlab platform.
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shifting the azo hydrazone tautomeric equilibrium of Methyl Yellow in acidic medium by the formation of inclusion complexes with cyclodextrins
Chemical Physics Letters, 2012Co-Authors: Ivania R. Ferreira, Rômulo A. AndoAbstract:Abstract The protonation of Methyl Yellow (MY) leads to a tautomeric equilibrium involving the azo and hydrazone species, where the latter is predominant. Electronic and Raman spectroscopic data show that when MY in acidic medium is included in cyclodextrins, there is an inversion in the relative ratio of tautomers, in which the azo species become the major species. This indicates that the azo bond is included in cyclodextrin precluding its protonation. The understanding of the protonation, tautomeric and inclusion equilibria of these systems plays an important role in the designing of cyclodextrin based molecular machines controlled by light.
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Shifting the Azo–hydrazone tautomeric equilibrium of Methyl Yellow in acidic medium by the formation of inclusion complexes with cyclodextrins
Chemical Physics Letters, 2012Co-Authors: Ivania R. Ferreira, Rômulo A. AndoAbstract:Abstract The protonation of Methyl Yellow (MY) leads to a tautomeric equilibrium involving the azo and hydrazone species, where the latter is predominant. Electronic and Raman spectroscopic data show that when MY in acidic medium is included in cyclodextrins, there is an inversion in the relative ratio of tautomers, in which the azo species become the major species. This indicates that the azo bond is included in cyclodextrin precluding its protonation. The understanding of the protonation, tautomeric and inclusion equilibria of these systems plays an important role in the designing of cyclodextrin based molecular machines controlled by light.
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Chromic materials for responsive surface-enhanced resonance Raman scattering systems: a nanometric pH sensor
Physical chemistry chemical physics : PCCP, 2009Co-Authors: Rômulo A. Ando, Nicholas P. W. Pieczonka, Paulo Santos, Ricardo ArocaAbstract:The use of chromic materials for responsive surface-enhanced resonance Raman scattering (SERRS) based nanosensors is reported. The potential of nano-chromic SERRS is demonstrated with the use of the halochrome Methyl Yellow to fabricate an ultrasensitive pH optical sensor. Some of the challenges of the incorporation of chromic materials with metal nanostructures are addressed through the use of computational calculations and a comparison to measured SERRS and surface-enhanced Raman scattering (SERS) spectra is presented. A strong correlation between the measured SERRS and the medium’s proton concentration is demonstrated for the pH range 2–6. The high sensitivity achieved by the use of resonance Raman conditions is shown through responsive SERRS measurements from only femtolitres of volume and with the concentration of the reporting molecules approaching the single molecule regime.
Saburo Shimabayashi - One of the best experts on this subject based on the ideXlab platform.
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SOLUBILITY OF MONOALKYL PHOPHATE IN WATER IN THE PRESENCE OF ARGININE AND TRITON, AND SOLUBILIZATION OF Methyl Yellow THROUGH THE MIXED MICELLE
Phosphorus Research Bulletin, 2008Co-Authors: Takeshi Murata, Tomoaki Hino, Satoru Ueno, Saburo ShimabayashiAbstract:Effects of arginine (Arg) and Triton such as Triton-X (TX) and Triton-N (TN) on the solubility of monoalkyl phosphoric acid (MAP) such as dodecyl (DP), myristyl (MP), and cetyl phosphoric acid (CP) in an aqueous phase were studied. Although these MAPs are scarcely soluble in water, their solubility at 70 oC increased with a concentration of Triton added. The effect of TN was stronger than that of TX. DP became soluble at room temperature when Arg was added up to the mixing ratio of Arg/DP = 3 in mole. MP and CP were hardly soluble yet in the presence of Arg alone while these became soluble after adding Triton together with Arg. Their acidic head group was ionized by Arg, resulting in an increase in its affinity for water. DP was soluble just after the ionization while MP and CP were soluble after the ionization and concomitant formation of the mixed micelle with the Triton added. Methyl Yellow, barely soluble in water, was solubilized after entrapment into the mixed micelle. Its solubility increased with a concentration and chain length of the MAP added as a solubilizing agent.
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Interaction and Complex Formation of Pluronic Polymers with Ionic Surfactants
Studies in Surface Science and Catalysis, 2007Co-Authors: Saburo Shimabayashi, Akihito Ichimori, Tomoaki HinoAbstract:ABSTRACT: Interaction of a pluronic polymer(Plu) with an ionic surfactant was studied. Specific behaviors of a solution of Plu mixed with an ionic surfactant, such as cloud point, relative viscosity, and solubilization of Methyl Yellow, were discussed, taking the binding isotherm into considerstion.
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Adsorption of Nonionic Surfactants, Triton X and Triton N, on Hydroxyapatite after Surface Modification with Sodium Dodecyl Sulfate in an Aqueous Phase
Studies in Surface Science and Catalysis, 2001Co-Authors: Saburo Shimabayashi, Masashi Hoshino, Takahisa Ohnishi, Tomoaki HinoAbstract:ABSTRACT Although Triton X-100 and Triton N, which are water-soluble nonionic surfactants, were scarcely adsorbed by HAP without SDS, these were adsorbed in the presence of SDS. On the other hand, Methyl Yellow, a water-insoluble dye, was also captured on the surface of HAP when HAP was treated with SDS. It was concluded that surface modification of HAP by SDS and hydrophobic interaction with SDS on the surface of HAP play important roles in the adsorption.
Rita H. De Rossi - One of the best experts on this subject based on the ideXlab platform.
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Cyclodextrin modified niosomes to encapsulate hydrophilic compounds
RSC Advances, 2018Co-Authors: Noelia D. Machado, Rita H. De Rossi, O. Fernando Silva, Mariana A. FernándezAbstract:Niosomes were prepared from equimolar mixtures of two non-ionic surfactants, Span 80 and Tween 80. The capability of the vesicular systems was studied through the encapsulation of two azo dyes as molecular probes of different hydrophobicity (Methyl orange (MO) and Methyl Yellow (MY)). To improve the efficiency of the niosomes to encapsulate the dyes, we employed an additional modification of the vesicular system, adding β-cyclodextrin (β-CD) or a modified amphiphilic β-CD (Mod-β-CD) to the niosomes. Neither the inclusion of dyes nor the incorporation of β-CD to the niosomes produces considerable modifications in size and morphology of the vesicles. However, in the presence of Mod-β-CD the niosomes became smaller, probably due to the anchoring of the cyclodextrin at the surface of vesicles through the hydrophobic chain, altering the curvature of the outer monolayer and reducing the surface charge of the interphase. The entrapment efficiency (EE) for MY was higher than that for MO in niosomes without cyclodextrin, however, the content of MO in the presence of β-CD increased considerably. Besides, the release of this dye under the same conditions was faster and reached 70% in 24 hours whereas in the absence of the macrocycle, the release was 15%, in the same time. UV-visible spectrophotometry and induced circular dichroism analysis allowed it to be established that MO is complexed with cyclodextrins inside vesicles, whereas MY interacts mainly with the niosome bilayer instead of with CD. Besides, the cavity of cyclodextrins is probably located in the interphase and preferably in the polar region of niosomes.
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Effect of β-Cyclodextrin on the Thermal Cis−Trans Isomerization of Azobenzenes
The Journal of Organic Chemistry, 1996Co-Authors: Ana M. Sanchez And, Rita H. De RossiAbstract:The cis−trans thermal isomerization of p-Methyl red (1), o-Methyl red (2), and Methyl orange (3) was inhibited by β-cyclodextrin (β-CD) at constant pH. Their isomerization rate decreased 4, 8, and 1.67 times, respectively, in a solution containing 0.01 M β-CD. This effect can be attributed to the formation of an inclusion complex between the substrate and β-CD which hinders the rotation of the NN bond. The isomerization rate of Methyl Yellow (4), 4-(diMethylamino)-4‘-methoxyazobenzene (5), and naphthalene-1-azo[4‘-(diMethylamino)benzene] (6) was not affected by β-CD due to the presence of an organic cosolvent in the solution which displaces the azobenzene from the cavity, and the complex formed is probably equatorial. In addition, the transition state for the isomerization of compounds 1−3 involves rotation and that of 4−6, which have only electron-donating groups, inversion. This latter process brings about less volume change than rotation so it is less hindered by the complexation with β-CD.
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Strong inhibition of cis-trans isomerization of azo compounds by hydroxide ion
The Journal of Organic Chemistry, 1993Co-Authors: Ana M. Sanchez, Rita H. De RossiAbstract:The thermel cis-trans isomerization rate of Methyl Yellow (1), p-phenyl red (2), and o-Methyl red (3) in aqueous solution was measured at different hydroxide ion concentrations, and it was found that there is a very strong inhibition as the pH increases. For 1 the rate changes from 2.17'710 -2 s -1 et NaOH 6'710 -3 M to 1.0'710 -3 s -1 at NaOH 0.1 M. The observed rate constant for 2 was too fast for the experimental technique used at a concentration of NaOH lower than 0.01 M. These results are interpreted in terms of a much faster rate of isomerization ofthe protonated cis compounds than the neutral ones, and values for the pK a and rate constants for both species are calculated
Daniel R. Spiegel - One of the best experts on this subject based on the ideXlab platform.
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forced rayleigh scattering studies of mixtures of amplitude and phase gratings in Methyl Yellow alcohol solutions
Journal of Chemical Physics, 2000Co-Authors: Ha Seon Park, Taihyun Chang, Daniel R. SpiegelAbstract:Forced Rayleigh scattering (FRS) studies have been carried out on Methyl Yellow/alcohol solutions at two different probe wavelengths (633 and 543 nm). The signal shapes observed at the two wavelengths are quite different: using ethanol and 2-propanol as solvents, we observe at 633 nm a decay–grow–decay (DGD) shape similar to profiles frequently reported in the literature, while at 543 nm we observe a DGD shape in which the signal at the local minimum does not reach the baseline. In principle, the nonzero minimum can be accounted for by a difference (due to amplitude/phase-grating mixtures) in the phase shifts of light scattered from the photoproduct and ground-state molecules. To test this hypothesis, we first show in a straightforward manner that the signal can be approximated as the product of a polynomial and an exponential decay, which allows for data reduction of profiles with zero or nonzero phase-shift differences. Using this approach, the diffusion coefficients measured using the two probe wavelengths are found to be the same to within an uncertainty of 2%–3%. The results provide strong evidence that the difference in signal shapes is caused by amplitude/phase-grating mixtures within the Methyl Yellow/alcohol system, and imply that diffusion coefficients can be measured without difficulty for other FRS systems characterized by such mixtures.
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Forced Rayleigh scattering studies of mixtures of amplitude and phase gratings in Methyl Yellow/alcohol solutions
The Journal of Chemical Physics, 2000Co-Authors: Ha Seon Park, Taihyun Chang, Daniel R. SpiegelAbstract:Forced Rayleigh scattering (FRS) studies have been carried out on Methyl Yellow/alcohol solutions at two different probe wavelengths (633 and 543 nm). The signal shapes observed at the two wavelengths are quite different: using ethanol and 2-propanol as solvents, we observe at 633 nm a decay–grow–decay (DGD) shape similar to profiles frequently reported in the literature, while at 543 nm we observe a DGD shape in which the signal at the local minimum does not reach the baseline. In principle, the nonzero minimum can be accounted for by a difference (due to amplitude/phase-grating mixtures) in the phase shifts of light scattered from the photoproduct and ground-state molecules. To test this hypothesis, we first show in a straightforward manner that the signal can be approximated as the product of a polynomial and an exponential decay, which allows for data reduction of profiles with zero or nonzero phase-shift differences. Using this approach, the diffusion coefficients measured using the two probe wavelengths are found to be the same to within an uncertainty of 2%–3%. The results provide strong evidence that the difference in signal shapes is caused by amplitude/phase-grating mixtures within the Methyl Yellow/alcohol system, and imply that diffusion coefficients can be measured without difficulty for other FRS systems characterized by such mixtures.
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analysis of complex forced rayleigh scattering decay profiles for the diffusion of Methyl Yellow in binary solution
Bulletin of The Korean Chemical Society, 1997Co-Authors: Ha Seon Park, Taihyun Chang, Jungmoon Sung, Hyunjung Lee, Daniel R. SpiegelAbstract:The nature and analysis methods of complicated decay profiles found in forced Rayleigh scattering (FRS) have been investigated for the probe diffusion of Methyl Yellow in 2-propanol. The complementary shifted and ground state grating effect, which is known to be the origin of non-single exponential decays, was analyzed by non-linear regression fitting to a double exponential model function. We confirmed that the parameters were highly correlated so that it was difficult to extract a unique set of parameters in the presence of experimental noise. Nevertheless, a reasonable range of decay time constants could be estimated from the grating spacing dependence.