Thermally Induced Depolarization of the Photoluminescence of Carbon Nanodots in a Colloidal Matrix

The effect of temperature on fluorescence polarization in a colloidal system of carbon nanodots in glycerol under linearly polarized excitation is investigated for the first time. It is found that the experimentally obtained temperature dependence of the degree of linear polarization of fluorescence can be described by the Levshin–Perrin equation, taking into account the rotational diffusion of luminescent particles (fluorophores) in the liquid matrix. The fluorophore size determined in the context of the Levshin–Perrin model is significantly smaller than the size of carbon nanodots. This discrepancy gives evidence that small atomic groups responsible for nanodot luminescence are characterized by high segmental mobility with a large amplitude of motion with respect to the nanodot core.