Photophysical investigation of methyl 2-hydroxy-3-naphthoate (MHN23) in different self-organized supramolecular assemblies of micelles and niosomes formed by nonionic surfactant

In this work, we have investigated the photophysical properties of methyl 2-hydroxy-3-naphthoate (MHN23) in two different types of heterogeneous microenvironments, micelles and niosomes formed by nonionic surfactant (Tween-80) by using the steady state and time-resolved fluorescence spectroscopy. The transmission electron microscopy (TEM) technique was also employed to confirm the formation of Tween-80/PEG-6000 niosomes. The experimental results indicate that in the confined systems both the absorption and the fluorescence intensity have been enhanced. The fluorescence intensity and fluorescence lifetime of MHN23 in niosomes were enhanced more than that in micelles. The enhanced fluorescence intensity and lifetime of MHN23 arise from the more rigid and confined microenvironment of niosomes. However, with the increasing of the surfactant concentration in micelles, the fluorescence lifetime of MHN23 in micelles gets longer gradually than that in niosomes. Consequently, it has been demonstrated that the photophysical properties of probes could be significantly affected by both the confined microenvironment and the concentration of surfactants.