TY - JOUR
T1 - Characterization of Aqueous Oleic Acid/Oleate Dispersions by Fluorescent Probes and Raman Spectroscopy
AU - Suga, Keishi
AU - Kondo, Dai
AU - Otsuka, Yoko
AU - Okamoto, Yukihiro
AU - Umakoshi, Hiroshi
N1 - Publisher Copyright:
© 2016 American Chemical Society.
Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2016/8/2
Y1 - 2016/8/2
N2 - Oleic acid (OA) and oleates form self-assembled structures dispersible in aqueous media. Herein, the physicochemical properties of OA/oleate assemblies were characterized using fluorescent probes and Raman spectroscopy, under relatively high dilution (<100 mM of total amphiphile) at 25 °C. Anisotropy analysis using 1,6-diphenyl-1,3,5-hexatriene showed that the microviscosity of the OA/oleate assembly was highest at pH 7.5 (the pH range of 6.9-10.6 was investigated). The fluorescence spectra of 6-lauroyl-2-dimethylaminonaphthalene revealed the dehydrated environments on membrane surfaces at pH < 7.7. The pH-dependent Raman peak intensity ratios, chain torsion (S = I1124/I1096) and chain packing (R = I2850/I2930), showed local maxima, indicating the occurrence of metastable phases, such as dispersed cubic phase (pH = 7.5), vesicle (pH = 8.5), and dispersed cylindrical micelle (pH = 9.7). These results suggest that large-scale OA/oleate assemblies could possess particular membrane properties in a narrow pH region, e.g., at pH 7.5, and 9.7.
AB - Oleic acid (OA) and oleates form self-assembled structures dispersible in aqueous media. Herein, the physicochemical properties of OA/oleate assemblies were characterized using fluorescent probes and Raman spectroscopy, under relatively high dilution (<100 mM of total amphiphile) at 25 °C. Anisotropy analysis using 1,6-diphenyl-1,3,5-hexatriene showed that the microviscosity of the OA/oleate assembly was highest at pH 7.5 (the pH range of 6.9-10.6 was investigated). The fluorescence spectra of 6-lauroyl-2-dimethylaminonaphthalene revealed the dehydrated environments on membrane surfaces at pH < 7.7. The pH-dependent Raman peak intensity ratios, chain torsion (S = I1124/I1096) and chain packing (R = I2850/I2930), showed local maxima, indicating the occurrence of metastable phases, such as dispersed cubic phase (pH = 7.5), vesicle (pH = 8.5), and dispersed cylindrical micelle (pH = 9.7). These results suggest that large-scale OA/oleate assemblies could possess particular membrane properties in a narrow pH region, e.g., at pH 7.5, and 9.7.
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U2 - 10.1021/acs.langmuir.6b02257
DO - 10.1021/acs.langmuir.6b02257
M3 - Article
AN - SCOPUS:84980377997
VL - 32
SP - 7606
EP - 7612
JO - Langmuir
JF - Langmuir
SN - 0743-7463
IS - 30
ER -