Spectroscopy of proflavine adsorbed on clays

Schoonheydt, Robert A.; Cenens, Jos; Schrijver, Frans C. De

doi:10.1039/f19868200281

Cited by 38 publications

(20 citation statements)

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“…It is a well-documented phenomenon that the higher the particle size of the clay, the higher the tendency to form the tactoid structure (Schoonheydt et al, 1986). For Hect, an octahedrally substituted smectite with a greater particle size than LapB, the experimental results suggest that the tactoid structure is formed at relatively concentrated clay suspensions.…”

Section: Resultssupporting

confidence: 49%

Spectroscopic study of the adsorption of rhodamine 6G on clay minerals in aqueous suspensions

Arbeloa

Tapia²,

Arbeloa³

et al. 1997

Clay miner.

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A B STRACT: Absorption and fluorescence spectroscopies were applied to study the adsorption of rhodamine 6G on several smectite-type clays in aqueous suspension. The dye can be adsorbed as the monomeric and the dimeric forms on both the external and the interlamellar surfaces of the clay. The presence of these species and their evolution with the stirring time of the sample and the relative dye/ clay concentration depend on the nature of the smectite, the clay concentration and the particle size, factors that also affect the dispersion degree of the clay particles in water.In recent years, the research on colloidal systems has become more important to the scientific community, since colloid chemistry plays a significant role in the progress of modem chemistry and engineering. The use of aromatic compounds as molecular probes has allowed the application of electronic spectroscopies to study the properties of microheterogeneous systems (Thomas, 1984;Kalyanasundaram, 1987;Gehlen & De Schryver, 1993), providing significant information on the surface properties of the interface between the dispersed phase and the dispersing medium. These properties affect the adsorption and distribution of compounds in both phases of organized media. One of these systems is clay minerals in aqueous suspensions, the interest in which is based on their important applications in several fields such as agriculture, catalysis, decontamination of waste water and pharmaceutical and paint industries (Theng, 1974;Laszlo, 1991;Murray, 1991).Smectite-type clays have a lamellar structure formed by the condensation of an octahedral sheet of A1203 or MgO between two tetrahedral SiO2 sheets, the so-called TOT layer (Newman, 1987). The isomorphic substitution of some A13+, Mg 2+ or Si 4 § by cations with a lower oxidation number gives rise to a negative charge of the layers which is compensated by interchangeable inorganic cations at the lamellar surface. The inorganic cations can cause the stacking of clay layers in parallel planes, the face-to-face aggregation, leading to the tactoidal structure of smectites with two main adsorption surfaces: the external and the internal. The dispersion of smectite particles in aqueous suspensions and the capacity of clays to adsorb organic compounds depend, among other factors, on the nature of the negative charge of the layers (octahedral or tetrahedral substitution), the nature of the inorganic cations, the swelling of the interlamellar space, and the particle size.Although several techniques (thermogravimetry, X-ray diffraction and FTIR, SERS and NMR spectroscopies) have been largely used to study organo-clay systems in the solid state, these methods are limited techniques in the study of organo-clay systems in aqueous suspensions. Recently, the X-ray microscopic technique has been applied to study clay aggregates in aqueous environments (Niemeyer et al., 1994), but this technique gives information on the clay particles rather than the distribution of organic compounds on clays. The UV-Vis absorption and fluo...

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Section: Resultssupporting

confidence: 49%

Spectroscopic study of the adsorption of rhodamine 6G on clay minerals in aqueous suspensions

Arbeloa

Tapia²,

Arbeloa³

et al. 1997

Clay miner.

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“…Dimerization was also noted on the interlamellar surfaces as on the external surfaces. Interlamellar dimer formation means that two layers of MB § were formed in the interlamellar space; this is confirmed by measurements of the d(001) spacing of a fully exchanged MB § (15.5 ~k) and ofproflavine-adsorbed Camp Berteau montmorillonite and Wyoming bentonite (15.5 ~) (Schoonheydt et al, 1986).…”

Section: Dimerization and Trimerizationmentioning

confidence: 56%

“…The aim of the present paper is to substantiate this conclusion and to see if information, similar to that obtained by luminescence techniques (Schoonheydt et al, 1984(Schoonheydt et al, , 1986Cenens et al, 1987;Viaene et aL, 1987), can be obtained by classical absorption spectroscopy using MB as a probe molecule.…”

Section: Introductionmentioning

confidence: 85%

“…For organic molecules on clays, luminescence spectroscopy is a useful technique because of its extremely high sensitivity and because dynamic processes can be studied. The disadvantage of luminescence spectroscopy is its restriction to luminescent molecules on clays that are essentially free of Fe 3+ (Schoonheydt et al, 1984(Schoonheydt et al, , 1986Cenens et al, 1987;Viaene et al, 1987). Moreover, interpretation of the results is hampered by the heterogeneity of the clay minerals themselves and by side reactions of the organic probe, such as protonation and aggregation.…”

Section: Introductionmentioning

confidence: 99%

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Visible Spectroscopy of Methylene Blue on Hectorite, Laponite B, and Barasym in Aqueous Suspension

Cenens

1988

Clays and clay miner.

310

203

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Abstract--The absorption spectra of methylene blue ion exchanged on hectorite, Laponite B, Barasym, or sepiolite in dilute aqueous suspensions show the presence of the monomer, the protonated monomer, the dimer, and the trimer. Due to conformational differences, the absorption band maximum of the monomer with respect to its maximum in aqueous solution is red shifted when it is adsorbed on the external surface and blue shifted when it is adsorbed on the interlamellar surface. The availability of the interlamellar surface for methylene blue as a function of the type of clay and/or the counterion present thereby can be probed. The results indicate that 0.6-0.7% of the cation-exchange capacity of Barasym consists of acid sites capable of protonating methylene blue. Counterions of low hydration energy were found to induce a small number of similar sites in hectorite and Laponite B; hence, these sites must be situated on the external surface. Dimers formed on external surfaces show one absorption band. Dimers formed on the interlamellar surface of hectofite yield spectra having two absorption bands. The trimer was formed only at the external surface. With increasing loading of the clays, the spectra of methylene blue showed metachromasy. The metachromatic behavior can be fully explained by dye aggregation, which is the result of its concentration on the surface. No 7r-electron interaction with the surface oxygens need be invoked.

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“…Hectorite (HEC), Barasym (BS) and Wyoming bentonite (WB) from the Clay Minerals Society were fully exchanged with Na § fractionated (< 0.3 /tm) and freeze dried (Schoonheydt et al, 1986). Laponite (LAP), from Laporte Industries, was used as received due to its small particle size (20-30 nm).…”

Section: Sensitizers and Supportsmentioning

confidence: 99%

Tryptophan Photo-Oxidation by Clay-Adsorbed Sensitizers

Cenens

Schoonheydt

1988

Clay miner.

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A B S T R A C T :The photo-oxidation of tryptophan (TRP), photosensitized by methylene blue (MB) exchanged on hectorite, Wyoming bentonite and laponite is strongly influenced by three factors: (i) Fe(III) in the structure, which quenches the excited state of MB; (ii) the adsorption site of MB, as photo-oxidation only takes place with MB on the external surface; (iii) dye aggregation, which reduces the yield. Rose bengal (RB), chemically anchored on the external surface of Barasym does not sensitize the photo-oxidation of TRP.Two electronically excited singlet states of oxygen are located 94.3 and 157

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Spectroscopy of proflavine adsorbed on clays

Cited by 38 publications

References 1 publication

Spectroscopic study of the adsorption of rhodamine 6G on clay minerals in aqueous suspensions

Spectroscopic study of the adsorption of rhodamine 6G on clay minerals in aqueous suspensions

Visible Spectroscopy of Methylene Blue on Hectorite, Laponite B, and Barasym in Aqueous Suspension

Tryptophan Photo-Oxidation by Clay-Adsorbed Sensitizers

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