Rutin (Fluca) and methanol (Aldrich) were used as received.
The 0.1 M phosphate buffer at pH 7.4 was prepared using distilled
water solutions of salts NaH2PO4 H2O and Na2HPO4 in appropriate
proportions. Ethanol (95%) was purified and tested by spectral
techniques. The low-temperature measurements were carried out
at 77 K in ethanol which becomes glassy at this temperature. The
absorption spectra were recorded using a Cary-500 spectrophotometer
in 2 mm cells and concentrations at 3 10−5 M. The
luminescence spectra were measured by a high-aperture system
described in [15]. The kinetics and the phosphorescence spectra
were recorded by a two-disk phosphoroscope driven by two
synchronous motors. The phosphoroscope time resolution was
10−3 s. The fluorescence quantum yield Φf was measured with
respect to quinine sulfate in 1 N H2SO4 with a refractive index
n¼1.338 which has the fluorescence quantum yield Φf¼0.55 [16].
Nanosecond fluorescence lifetimes were determined by the
method of time-correlated single-photon counting using a PRA
model 3000 ns lifetime fluorometer. The parameters describing
the fluorescence decays were analyzed using a packet of programs
T900 developed in Edinburg Instruments Company.