Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/71863
Type: Artigo de periódico
Title: Solvation of coumarin 314 at water/air interfaces containing anionic surfactants. I. Low coverage
Author: Pantano, DA
Sonoda, MT
Skaf, MS
Laria, D
Abstract: Through the use of molecular dynamics techniques, we analyze equilibrium and dynamical aspects of the solvation of Coumarin 3 14 adsorbed at water/air interfaces in the presence of sodium dodecyl sulfate surfactant molecules. Three different coverages in the submonolayer regime were considered, 500, 250, and 100 angstrom(2)/SDS molecule. The surfactant promotes two well-differentiated solvation environments, which can be clearly distinguished in terms of their structures for the largest surfactant coverage considered. The first one is characterized by the probe lying adjacent or exterior to two-dimensional spatial domains formed by clustered surfactant molecules. A second type of solvation environment is found in which the coumarin appears embedded within compact surfactant domains. Equilibrium and dynamical aspects of the interfacial orientation of the probe are investigated. Our results show a gradual transition from parallel to perpendicular dipolar alignment of the probe with respect to the interface as the concentration of surfactant rho(s) increases. The presence of the surfactant leads to an increase in the roughness and in the characteristic width of the water/air interface. These modifications are also manifested by the decorrelation times for the probe reorientational dynamics, which become progressively slower with rho(s) in both solvation states, although much more pronounced for the embedded ones. The dynamical characteristics of the solvation responses of the charged interfaces are also analyzed, and the implications of our findings to the interpretation of available experimental measurements are discussed.
Country: EUA
Editor: Amer Chemical Soc
Rights: fechado
Identifier DOI: 10.1021/jp045687e
Date Issue: 2005
Appears in Collections:Artigos e Materiais de Revistas Científicas - Unicamp

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