Monitoring Ternary Systems of C₁₂E₅/Water/Tetradecane via the Fluorescence of Solvatochromic Probes

Abstract

In this work ternary systems of the nonionic surfactant C 12 E 5 (C 12 H 25 (OCH 2 CH 2) 5 OH), tetradecane, and water were probed by the use of steady state and time-resolved fluorescence. Microemulsions, which were rich in oil, rich in water, and also both continuous in oil and water, were monitored via the application of solvatochromic fluorescent probes. The hydrophobic laser dye Nile Red was used to report from the side of the oil-surfactant interface, while Prodan, which is soluble in each of the constituent solvents, was used to provide a global picture. To complement these, the hydrophilic dye 4-(2-(dimethylamino)phenyl)-1-methylpyridinium iodide was used to report from the side of the water-surfactant interface. The results show the partitioning of the probes into different environments within the ternary systems as evident from the solvatochromic shift in the emission spectra, uncovering similarities between the water-rich and bicontinuous regions in terms of polarity. Estimates for the polarity of the environments in which the fluorophores are solubilized are made in terms of the E T(30) parameter scale. The time-resolved kinetics of some of the probes have been found to be viscosity dependent, which brought out similarities between the bicontinuous and oil-rich regions along with the observation of the effect of solvent relaxation in these ternary systems.

Vesicle–micelle transition in aqueous mixtures of the cationic dioctadecyldimethylammonium and octadecyltrimethylammonium bromide surfactants

“…In addition, this probe exhibits solvatochromic behaviour and in polar media it is observed a red shift in the emission maximum, together with fluorescence quenching, due to the capability of NR to establish hydrogen bonds with protic solvents [24]. As a consequence, the NR emission in water is very weak with λ max ≈ 660 nm [25]. Fig.…”

The use of Nile Red to monitor the aggregation behavior in ternary surfactant–water–organic solvent systems

“…Nile Red 1 has been used previously in ternary surfactant systems. 2,3 Nile Red is soluble over a very wide range of solvents and shows a large bathochromic absorbance shift with increasing solvent polarity (108 nm from n-hexane to water), 4 which is linear with that of the long-wavelength absorption band of the popular E T (30) probe. 5 The E T (30) value of a solvent is the energy of the intramolecular charge transfer transition of 2,6-diphenyl-4-(2,4,6-triphenyl-1-pyridinium) phenolate, which depends strongly on the polarity of the medium.…”

Domain Formation in DODAB–Cholesterol Mixed Systems Monitored via Nile Red Anisotropy

“…This probe has a hydrophobic nature and has demonstrated its value in the study of biomembrane heterogeneity [23,24]. Both its steady-state and time-resolved fluorescence emission properties are strongly medium dependent [25][26][27] and it usually exhibits an increase in fluorescence yield with decreasing solvent polarity, with a corresponding blue shift in the peak emission. By studying the fluorescence anisotropy of Nile Red, we have previously obtained information concerning polarity and hydration level changes in vesicle systems [26].…”