Temperature Effect on the Fluorescence Anisotropy Decay Dynamics of Coumarin-153 Dye in Triton-X-100 and Brij-35 Micellar Solutions¶

Abstract

The fluorescence anisotropy decay dynamics of the fluorescent probe Coumarin-153 (C153) have been investigated in two neutral micelles, Triton-X-100 (TX-100) and Brij-35 (BJ-35), at different temperatures and analyzed on the basis of the well-known two-step model. Because steady-state fluorescence spectra of the above probe do not show any noticeable changes with respect to temperature, for either of the studied micelles, suggests a similar polarity in the microenvironment around the probe at all the temperatures studied. The anisotropy results indicated that, for both the micelles, the fluidity inside the Palisade layer increases with temperature. However, the temperature effect on the anisotropy decay is relatively more pronounced in TX-100 than in BJ-35. It is inferred that the temperature effect on the anisotropy decay in the BJ-35 micelle is mainly due to the thermal effect on the microviscosity in the micellar phase. In the case of TX-100, the results indicate that, along with the above thermal effect, an additional effect is observed due to the increased size and hydration of the micelle with temperature, with the result being that the fluorescence anisotropy decay in TX-100 is more sensitive to temperature than in BJ-35. In the TX-100 micelle, our studies show that with an increase in temperature, even though the micellar size increases substantially, the distance of the probe from the micellar core does not increase that significantly. Thus, with increasing temperature, the probe undergoes a relative migration toward the micellar core to avoid the increased hydration in the micellar Palisade layer.

Nanothermometry: From Microscopy to Thermal Treatments

“…[50] Higher temperature leads to as horter rotational correlation time, and therefore, lower anisotropy according to the Perrin equation. Fluorescenceanisotropyh as ac omplex dependence on temperature.…”

Effect of nanosize micelles of ionic and neutral surfactants on the photophysics of protonated 6-methoxyquinoline: Time-resolved fluorescence study

“…The appreciable difference of average lifetime of 6MQ + in the SDS micelles than that in pure water rules out the possibility of location of 6MQ + molecules around the bulk phase and suggests that most of the 6MQ + molecules in SDS micelles are localized in micelle-water interface. The single exponential nature of the fluorescence decay in micellar systems indicate that the probe molecules are mostly solubilized at similar sites of the micelles [51][52][53]. 6MQ + giving multi-exponential decay at different concentrations of micellar solution at different emission wavelengths suggest that the probe molecule is not located in a single type of site of the micelles.…”

Quantitative model for prediction of hydrodynamic size of nonionic reverse micelles

“…This phenomenon is attributed to a disruption of hydrogen bonding, between the water and the polyethoxylate units in the molecule. Although studies on the temperature dependence of NP micelle size have yet to be reported, previous studies on other surfactants such as Triton X-100, Brij-35, and pyridinium surfactants also indicate a temperature dependence [16,44,[47][48][49][50]. While temperature does in fact affect micelle size, it was not included as a parameter in the determination of the model.…”