Metachromasy as an indicator of photostabilization of methylene blue adsorbed to clays and minerals

Samuels, Maya; Mor, Omer; Rytwo, Giora

doi:10.1016/j.jphotobiol.2013.02.004

Cited by 21 publications

(7 citation statements)

References 19 publications

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“…Incorporation of organic molecules into inorganic host materials is known as a promising method to improve the stability of the organic molecules [10]. For instance, inclusion of dyes into the clay interlayers [11][12][13], zeolites [14,15], and mesoporous silicates [16][17][18] have been reported to enhance the stability of the guest materials. The ancient Maya Blue is also a good example of the composite materials, where the guest indigo dye is greatly stabilized by the incorporation into the channel of the palygorskite clay [19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Enhanced stability of natural anthocyanin incorporated in Fe-containing mesoporous silica

Kohno

Kato

Shibata

et al. 2015

Microporous and Mesoporous Materials

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Anthocyanin is known as a safe coloring material although its poor stability often limits more extended use. In this study, we tried the enhancement of the photostability of the anthocyanin by the incorporation into the pore of HMS type mesoporous silica containing various metal 2 ions. The anthocyanin was adsorbed on the HMS by pouring a highly concentrated anthocyanin solution to the dried HMS, urging the incorporation of the dye into the mesopore by a capillary condensation. Improved stability of the anthocyanin against visible irradiation was achieved by the adsorption onto the HMS containing Fe 3+ , although other metal ions in the HMS showed less effect on the stabilization. From the UV-Vis spectroscopy, the Fe 3+ species effective for the stabilization of the anthocyanin was found to be the tetrahedral one highly dispersed in the silica framework. The decrease in the absorptivity of the anthocyanin on the Fe-HMS compared to other metal-containing HMS suggested that the Fe-HMS promoted the aggregate formation of the anthocyanin molecules. The highly dispersed Fe 3+ species had an ability to gather the anthocyanin molecule close to itself, resulting in tight incorporation of the dye inside the mesopore. The incorporation and aggregate formation of the anthocyanin was expected to contribute to the improvement of the stability against irradiation.

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Section: Introductionmentioning

confidence: 99%

Enhanced stability of natural anthocyanin incorporated in Fe-containing mesoporous silica

Kohno

Kato

Shibata

et al. 2015

Microporous and Mesoporous Materials

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“…The inclusion of the dye as a guest molecule into inorganic host materials is a promising approach, like the ancient Mayan people who used the composite of indigo and palygorskite clay for their colorant [15,16]. The intercalation of cationic or anionic dye molecule into the clay interlayer has been carried out to enhance the stability of the dye [17][18][19][20][21][22][23][24]. We have also reported the stability enhancement of the natural dye such as anthocyanin [25] and carmine [26] by the intercalation between the clay layers.…”

Section: Introductionmentioning

confidence: 99%

Improved photostability of hydrophobic natural dye incorporated in organo-modified hydrotalcite

Kohno

Asai

Shibata

et al. 2014

Journal of Physics and Chemistry of Solids

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The β-carotene and annatto extract are typical carotenoids used as a safe colorant of foods. However, the instability against irradiation limits their wide use. The improvement of the stability was investigated by the intercalation of the dye into the interlayer space of the anion-exchangeable clay, hydrotalcite. The hydrophobic environment was constructed in the interlayer space of the hydrotalcite by the modification with anionic surfactant (dodecyl sulfate and dodecylbenzene sulfonate). The lipophilic β-carotene and annatto dye were successfully incorporated into the organo-modified hydrotalcite, and the incorporated dye exhibited the improved photostability under visible irradiation from a 100 W halogen lamp (190 klux) in the air. The effect of the stabilization on the anionic annatto dye was higher by the incorporation in the modified hydrotalcite than in the modified cation exchangeable clay, suggesting that the polarity of the clay sheet had some influence on the stabilization of the incorporated dye. The stabilization effect of the β-carotene was not so significant as that of the annatto dye, because sufficient intercalation of the non-polar β-carotene may require stronger hydrophobic environment. The π-π interaction between the β-carotene and the benzene ring of the dodecylbenzene sulfonate was found to contribute to the stability enhancement.

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“…Another cause of the metachromacy may be stacking interactions between the ligands and copper complexes in which the complexes' electron cloud may be attracted toward a polar group of the ligand. This lowers the energy of highest occupied molecular orbital (HOMO) while empty and lowest unoccupied molecular orbital (LUMO) remains unaffected creating a higher energy difference between the orbitals and the transition occurs at higher energy thus at shorter wave length [47,48]. Nevertheless, it is clearly visible that band shift is correlated with metal cation adsorption capacity and formation of organic complexes.…”

Section: Uv-vis-drsmentioning

confidence: 99%

Interaction between adsorbed molecules and tailor made large chelating ligands grafted on SBA-15 studied by means of thermoporometry

Węgrzyn

Radko

Majda

et al. 2018

Microporous and Mesoporous Materials

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Modified mesoporous silicas were examined as adsorbents for efficient removal of model pollutants from wastewaters. Functionalized SBA-15 materials for capture of cationic pollutants such as metal cations and anionic dyes were obtained using post-synthesis grafting method. Large organic ligands containing acetyloacetone, 2aminopyridine, 2-aminothiazole and 2-aminobenzothiazole groups were incorporated into the adsorbents' structure. The adsorption capacities reached levels of 38.6, 43.1, 64.3, 68.6 and 88.9 mg g −1 for Cu 2+ , Rose Bengal, Congo Red, Levafix Amber CA gran and Methyl Orange, respectively. Moreover, the adsorption efficiency depended on a type of the model molecule and a type of the surface chelating group. The pores' size and the pores' volume of the hybrid materials before and after adsorption was determined in hydrated state using thermoporometry. For the first time, by means of this methodology, it was possible to propose a model of interactions between the adsorbed molecules and the grafted organosilanes. Adsorption of organic dyes resulted in most cases in formation of J-aggregates.

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Metachromasy as an indicator of photostabilization of methylene blue adsorbed to clays and minerals

Cited by 21 publications

References 19 publications

Enhanced stability of natural anthocyanin incorporated in Fe-containing mesoporous silica

Enhanced stability of natural anthocyanin incorporated in Fe-containing mesoporous silica

Improved photostability of hydrophobic natural dye incorporated in organo-modified hydrotalcite

Interaction between adsorbed molecules and tailor made large chelating ligands grafted on SBA-15 studied by means of thermoporometry

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