Beşer, Burcu Meryem; Arik, Mustafa; Onganer, Yavuz

In this study, photophysics and photodynamical properties of Pyronin Y (PyY) in different liquid media were investigated. Interactions of PyY, which is a positively charged pigment compound pertaining to the xanthene derivatives with surfactants possessing distinct charges, were determined by using the molecular absorption and fluorescence spectroscopy techniques. It was observed that band intensities of absorption and fluorescence spectra belonging to PyY increase in proportion to the water when compared to three micelle systems, cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and Triton X-100 (TX-100). This suggests that interactions in micelle systems are different from those in deionized water, and solvation and surface interactions modify. It is determined that the strongest interaction occurs between PyY dye and SDS, anionic surfactant, and this interaction arises from the electrostatic forces. Calculated photophysical parameters indicated that the microenvironment of PyY in SDS micelle is different to that of other systems. In temperature studies, it was reported that increasing the temperature of the samples increased non-radiative transitions. Steady-state fluorescence anisotropy values were calculated by using fluorescence intensities of PyY compound in pre-micellar, micellar and post-micellar systems. Once the PyY fluorescence probe is added to the surfactant containing solutions below the critical micelle concentrations, the measured anisotropy values were found to be low because the probe remains in the deionized water phase. When the surfactant concentration of the medium becomes closer to the critical micelle concentrations, the steady-state anisotropy value prominently increases. This is because of the restrictions on the rotational diffusion of the probe in micellar solution. It is observed that positively charged PyY shows a higher affinity to the negatively charged SDS compared with the positively charged CTAB and neutral TX-100 surfactants. This can be explained by Coulombic interactions.

Beşer, Burcu Meryem; Onganer, Yavuz; Arik, Mustafa

The photophysical properties and photodynamics of Pyronin Y (PyY) dye compound in seven polar protic solvents (n-alcohols) were examined as a function of temperature by using UV–visible, steady-state and time-resolved fluorescence spectroscopy techniques. To understand dye–solvent interactions, photophysical parameters including Stokes’ shifts, fluorescence quantum yields and fluorescence lifetimes were determined. To examine the effect of solvent polarity, the difference between the ground state dipole moment and the excited state dipole moment was determined. For this purpose, the multiple regression analysis and the Kamlet–Taft technique were used. Moreover, photodynamic parameters, rotational relaxation times and steady-state anisotropy were calculated. The result showed that the specific interactions of PyY with the solvent molecules take place through hydrogen bonding. As the hydrocarbon chain of the alcohols gets longer, photophysical parameters diminish, probably because of weaker hydrogen bonding. Furthermore, it was found out that the dipole moment of excited states (μe) is higher than that of the ground state (μg). In addition, Brownian motions increased with the increasing temperature that weakened the fluorescence character of PyY. It was also revealed that the rotation of PyY increased with a prolonged hydrocarbon chain of alcohol series, due to the lesser extent of hydrogen bonding.