Photoluminescence (PL) spectra were recorded in quartz cuvettes on a Spectrofluorometer SF5 (Edinburgh Instruments) with a standard cuvette holder SC-05. A xenon lamp was used as an excitation source, and data were processed with the Fluoracle software. Absorbance spectra were measured from 200-600 nm with a 1 nm bandwidth and a step of 1 nm. The absorbance data were used to calculate a real concentration of dye in the samples.