Optical and luminescence investigations of hydroxy substituted porphyrins in borate glasses

Hybrid borate glasses containing various hydroxy phenyl derivatives of porphyrin were prepared by melt quenching technique. The effect of hydroxy functional groups on the photophysical properties was investigated by means of optical absorption, steady-state fluorescence and time resolved fluorescence spectroscopy. The optical absorption spectra show red shift in Soret and Q-band with increase in the number of –OH groups on the phenyl ring of the porphyrin. The steady-state emission spectrum shows strong S2→S0 emission around 498–540 nm and red shifted S1→S0 emission around 669–803 nm. Time resolved fluorescence shows three exponential decay with τ1 = 11 ± 2 ps (64.56%), τ2 = 0.16 ± 0.1 ns (24.54%), and τ3 = 2.94 ± 0.1 ns (10.9%) for 2 mg of H2OHP doped glass. The appearance of strong S2→S0 emission indicates that the structure of porphyrin inherently modified in the glass matrix. The boron ions of the borate network interact at the central core of the porphyrin and also form oxy bridge at the periphery. The effect of porphyrin concentration on photophysical properties and the possible structures of porphyrin in the borate glass matrix were investigated.

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