Absorption and photoluminescence (PL) spectra, PL quantum efficiency, and PL lifetime have been investigated on bis(8-hydroxyquinoline) zinc (Znq2) and magnesium (Mgq2) in solutions and powder. Znq2 and Mgq2 have the lowest-energy absorption band at 376 and 396 nm in acetonitrile solution, respectively, and emission band with peak at 555 and 480 nm. The PL quantum efficiency is 0.03 and 0.45 for Znq2 and Mgq2 in the solution, respectively, while 0.45 and 0.36 in powder. Unlike the case of powders, two PL lifetimes are obtained in solutions. The longer lifetime is attributed to molecule having interaction with its neighboring molecule, while the shorter one to the isolated single molecule.
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