Document Detail


Effect of Pressure on the Solubilization of a Fluorescent Merocyanine Dye by a Non-Ionic Surfactant.
MedLine Citation:
PMID:  22107347     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The target dye, which is a derivative of Merocyanine 540 bearing a naphthoxazole head group, persists as a monomer in ethanol solution but dimerizes in water under ambient conditions. Analysis of the absorption spectrum indicates that the dimer has an oblique geometry with the two molecules being held at an angle of ca. 550. Applying high pressure to the system forces the two molecules into closer contact, resulting in a decreased partial molar volume of 3.1 cm <sup>3. One molecule of the monomeric dye enters a neutral micelle formed from Triton X-100, where it is highly fluorescent and free of exciton coupling. The result of applied pressure on these latter systems depends on the concentration of surfactant. Above the critical micelle concentration (CMC), applied pressure has little effect other than to increase the viscosity inside the micelle. At very low surfactant concentration, applied pressure forces monomeric dye into the dimeric form, as observed in the absence of Triton X-100. It is notable, however, that the pressure effect on the dimerization constant is exaggerated in the presence of surfactant. At intermediate surfactant concentrations, applied pressure leads to a marked change in the CMC. In particular, applied pressure reduces the partial molar volume of the micelle by ca. 7.9 cm3 and induces micelle formation at relatively low concentration of surfactant. For example, the CMC falls from ca. 250 M at atmospheric pressure to only 50 μM at 460 MPa.
Authors:
Mohammed A H Alamiry; Andrew Christopher Benniston; Anthony Harriman
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-11-22
Journal Detail:
Title:  The journal of physical chemistry. B     Volume:  -     ISSN:  1520-5207     ISO Abbreviation:  -     Publication Date:  2011 Nov 
Date Detail:
Created Date:  2011-11-23     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101157530     Medline TA:  J Phys Chem B     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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