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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Interaction of Auramine O with montmorillonite clays

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Author(s):
Ferreira, Avelardo U. C. [1] ; Poli, Alessandra L. [1] ; Gessner, Fergus [1] ; Neumann, Miguel G. [1] ; Schmitt Cavalheiro, Carla C. [1]
Total Authors: 5
Affiliation:
[1] Univ Sao Paulo, Inst Quim Sao Carlos, BR-13560970 Sao Carlos, SP - Brazil
Total Affiliations: 1
Document type: Journal article
Source: Journal of Luminescence; v. 136, p. 63-67, APR 2013.
Web of Science Citations: 15
Abstract

The spectroscopic behaviour of Auramine O (AuO) in aqueous suspensions of montmorillonite clays was studied using absorption and static and dynamic fluorescence techniques. The fluorescence of Auramine O increases immediately after mixing the dye solution with the suspension of clay due to its adsorption on the external surface of the clays, which restricts the torsional molecular motion of Auramine. At longer times, the dye molecules migrate into the interlamellar region of the clay particles. Aggregation of the dye molecules can occur in the interlayer region, leading to the decrease of the fluorescence emission. The fluorescence quantum yields (Phi(F)) of AuO on the natural montmorillonites SAz-1, SWy-1, Syn-1 and Laponite clays were 0.015, 0.007, 0.016 and 0.017, respectively. These values are higher than the Phi(F) of AuO in aqueous solution and are of the same order of magnitude of the Phi(F) found for viscous solvents such as n-hexanol and n-heptanol (0.014 and 0.015). Time-resolved fluorescence spectroscopy studies of adsorbed Auramine on clays revealed multi-exponential decays with components in the 25-36, 219-362 and 1300-1858 ps ranges. The short-lived components can be attributed to species bound to external surface and the longer lifetime is assigned to dye molecules in interlayer spaces interacting strongly with the clay. It seems clear that the binding of Auramine to clays causes a significant reduction of the rate of internal conversion that does involve rotational diffusion, so that the clay will be locked in a conformational geometry unfavourable for internal conversion. (c) 2012 Elsevier B.V. All rights reserved. (AU)

FAPESP's process: 09/15998-1 - UV/visible light interactions with polymer-clay composites: photopolymerization and photodegradation
Grantee:Carla Cristina Schmitt Cavalheiro
Support Opportunities: Regular Research Grants