The steady-state measurements were recorded on a Jobin Yvon Fluorolog-3 spectrofluorometer from Horiba Scientific and the FluorEssence program. The excitation source was a 450 W xenon lamp, and the detector used was R-928 operating at a voltage of 950 V. Excitation and emission slits width were 1 nm. The fluorescence quantum yields were determined using quinine sulphate and tris(bipyridine)ruthenium (II) chloride as the standard (Φ = 0.53 in H2SO4, 0.05 M and Φ = 0.028 in H2O, respectively) using