Influence of the cetyltrimethylammonium chloride micellar pseudophase on the protolytic equilibria of oxyxanthene dyes at high bulk phase ionic strength

Mchedlov‐Petrossyan, Nikolay O.; Kleshchevnikova, V. N.

doi:10.1039/ft9949000629

Cited by 67 publications

(116 citation statements)

References 31 publications

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“…indicating an apparent pKa value [29] of roughly 9 instead of 10. The downward shift in apparent pKa upon sorption in cationic micelles was also observed by Mchedlov-Petrossyan and Kleshcheevnikova [30] and is at least partly due to the fact that the local pH at the micelle-water interface is higher than the bulk pH. In addition, it is known that the dissociation equilibrium may be affected by the molecular environment of the dissociating group.…”

Section: H-nmrmentioning

confidence: 56%

NMR study of the influence of pH on phenol sorption in cationic CTAB micellar solutions

Sabatino

Szczygiel

Sinnaeve

et al. 2010

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Interactions between phenol and cationic cetyltrimethylammonium bromide (CTAB) micelles have been investigated by means of nuclear magnetic resonance spectroscopy. The combined use of 1 H and NOESY techniques revealed that phenol has different preferred locations of interaction depending on the pH. At neutral pH (6.70) conditions, phenol molecules are preferentially located in the outer micelle region, at the micelle-water interface, while at more basic pH (9.94), the deprotonated phenol molecules (C 6 H 5 O -) are immersed into the palisade layer of the micelle. In addition, quantitative estimates of the solubilized fraction of phenol were obtained by using PFG-NMR. The results indicate that the phenol-CTAB interactions, although already present in neutral pH conditions, are largely favored in basic conditions as a consequence of the strong electrostatic interaction between the negatively charged phenolate ions and the positive charge of the cationic surfactant head group.(e)

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Section: H-nmrmentioning

confidence: 56%

NMR study of the influence of pH on phenol sorption in cationic CTAB micellar solutions

Sabatino

Szczygiel

Sinnaeve

et al. 2010

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…9,11,39,40 In turn, for neutral red and malachite green similar spectral shifts were registered in micellar solutions and microemulsions of an anionic surfactant SDS, in aqueous solutions of anionic calixarens, in suspensions of liposomes. [9][10][11][12] Batochromic shift of 10 nm was observed for basic forms of eosin, ethyleosin, methyleosin, and uranin (disodium salt of fluorescein), captured in gelatin layer of photographic plates manufactured by Agfa (Agfa Gevaert graphic gelatin film, 61101508).…”

Section: Spectral Characteristics Of Indicators Immobilized In the Gementioning

confidence: 80%

“…This indicates the shift of tautomeric equilibrium of this neutral form from the quinonoid, which is colored like that of ethyleosin ( Figure 4, curves 2, 4) toward the colorless lactone ( Figure 6). 39,40 It is worth to point out that disappearance of fluorescence was observed for xanthenes during injection of it in gelatin film. It can be caused both by concentration quenching and dimerization of the dyes in the gelatin matrix.…”

Section: Spectral Characteristics Of Indicators Immobilized In the Gementioning

confidence: 99%

Protolytic properties of dyes embedded in gelatin films

Никитина¹,

Reshetnyak²,

Svetlova³

et al. 2011

J. Braz. Chem. Soc.

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O filme de gelatina endurecida fixo em uma base transparente de triacetilcelulose pode ser utilizado como um suporte conveniente para indicadores ácido-base. Azul de bromofenol, verde de bromocresol, eosina, etil-eosina, n-decil-eosina, n-decil-fluoresceína, vermelho neutro e verde de malaquita foram incorporados nos filmes de gelatina por extração em meio aquoso sob condições apropriadas. A absorção de luz dos filmes dopados com corante exibe uma resposta ao pH de soluções tampão aquosas nas quais foram imersos. Valores reprodutíveis das constantes aparentes de dissociação dos indicadores, pK a app , foram calculados pelo tratamento convencional dos valores de pH do tampão aquoso e também para a água absorvida nos filmes de gelatina. Os experimentos com pH abaixo e acima do ponto isoelétrico da gelatina (em torno de pH 5) resultaram em valores de pK a app semelhantes àqueles em meios micelares de tensoativos catiônicos e aniônicos, respectivamente. Os filmes de gelatina modificados por corantes podem ser recomendados para uso em sensores óticos e dispositivos similares.The hardened gelatin film fixed on the transparent triacetylcellulose support can be utilized as a convenient carrier for acid-base indicator dyes. Bromophenol blue, bromocresol green, eosin, ethyleosin, n-decyleosin, n-decylfluorescein, neutral red, and malachite green were embedded into the gelatin films by extracting from aqueous media under appropriate conditions. The light absorption of dye-doped films exhibits a response to the pH values of aqueous buffer solutions, where they were soaked in. The well-reproducible indices of the apparent ionization constants, pK a app , of the indicators were calculated by conventional equating the pH values of the bulk aqueous buffer and those of the 'internal' water into the gelatin films. The experiments with pH below and above the isoelectric point of gelatin (around pH 5) result in pK a app values, which resemble those in micellar media of cationic and anionic surfactants, respectively. The dye-modified gelatin films can be recommended for use in optical sensors and related devices. Keywords: dye-modified gelatin film, indicators, apparent ionization constants, medium effects IntroductionThis paper is devoted to the influence of hardened gelatin media on the spectral and acid-base properties of immobilized xanthene, sulfonephthalein, and some other dyes.The immobilization of reagents in solid matrix (cellulose, ion-exchangers, polymers, silica, xerogels, etc.) 1-7 or using organized solutions, e.g., surfactant-based ones, [8][9][10][11][12] modifies the properties of guest molecules owing to the change of the microenvironment.Such modifications, or medium effects, are most studied and well documented for acid-base indicators. 8,9 In this case, the influence of the microenvironment results in the shift of the indicator equilibrium as compared to that in aqueous media. The main reasons are the local polarity and the local electrical charge. The latter often (but not always) manifests itself in the decre...

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“…The carboxyl group of benzoic acid was transformed into the carboxylate and formed a chelate complex with the titanium species as reported in the fluorescein-doped titania [14]. This is because the proton dissociation constant, pK a , of the carboxyl group of benzoic acid, i.e., 4.2, is close to that of fluorescein, i.e., 4.45 [32]. The FTIR spectrum suggests that a dehydration between the carboxyl group of benzoic acid and the OH group on the titania surface induced the chelating linkage.…”

Section: Resultsmentioning

confidence: 66%

Photocatalytic reaction on photofuel cell titania electrode

2011

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Benzoic acid-doped titania electrodes were prepared from titanium alkoxide sols containing benzoic acid in order to examine the photocatalytic reaction of the fuel material concentrated on the titania surface of a photofuel cell electrode. This doping was developed in order to understand the physicochemical processes on the titania rather than to advance the practical use of the photofuel cells. The observed photocurrent and CO 2 and H 2 O productions indicated that the oxidation of the benzoic acid enhanced the generation of electricity during the UV irradiation. Benzoic acid molecules should be oxidized by oxygen molecules and holes on the titania surface. The steam treatment of the electrodes improved the benzoic acid oxidation and the photocurrent because it promoted the titania densification and enhanced the interaction between the benzoic acid and titania. The benzoic acid-doped titania is a valid model of the fuel material concentrated in the porous titania when using benzoic acid as the fuel material. The contact between the benzoic acid and titania is important in order to obtain a high photofuel electric conversion.

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Influence of the cetyltrimethylammonium chloride micellar pseudophase on the protolytic equilibria of oxyxanthene dyes at high bulk phase ionic strength

Cited by 67 publications

References 31 publications

NMR study of the influence of pH on phenol sorption in cationic CTAB micellar solutions

NMR study of the influence of pH on phenol sorption in cationic CTAB micellar solutions

Protolytic properties of dyes embedded in gelatin films

Photocatalytic reaction on photofuel cell titania electrode

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