2.3. Fluorescence Lifetime Measurements

Fluorescence lifetime measurements were conducted at 298.15 K using an FS5 fluorescence spectrometer (Edinburgh Instruments, Livingston, U.K.) equipped with a 270 nm picosecond pulsed LED source using the time-correlated single-photon counting method as reported in previous work.¹⁹ The emission wavelength was set as 340.0 nm, and both excitation and emission slits were set as 5.0 nm. The instrumental response function (IRF) was detected by measuring the colloidal silica (Ludox AM-30, 30 wt % suspension in water) solution. The fluorescence decay plots were fitted with the biexponential decay law using Origin 7.5 software after deconvolution of the IRF.