Investigation of Micellar Effects in Thermal Lens Spectrophotometry

Abstract

The effect of micellar solutions in thermal lens spectrophotometry was investigated. Several aspects of the thermal lens signal including the formation rate and the relaxation of the thermal lens were compared in various neat solvents and in aqueous micellar solutions. The experiments were performed with a double-beam thermal lens apparatus based upon a pulsed-dye laser as the excitation beam and a He-Ne laser as the probe beam. The results show that, if micellar solutions can be used to solubilize hydrophilic species in solvents having better thermo-optical properties than water, they do not provide sensitive modifications of the thermo-optical properties of water. The absence of micellar effect in thermal lensing, in comparison to the well-known micellar enhanced fluorescence, is discussed with respect to the size of micelles and micellar dynamics, the photophysical processes associated with thermal lensing, and the time dependence of the thermal lens signal.