The photoluminescence properties of hybrid materials of metal (II)-8-hydroxyquinoline into mesoporous silica

The hybrid materials (HBs) of metal (II)-8-hydroxyquinoline complexes, namely Coq(2), Niq(2) and Znq(2) (Mq(2)), in the mesoporous silica were prepared, as well as their optical properties were investigated. The mesoporous silica (MCM) was synthesized by colloidal reaction of sodium silicate solution from the rice husk. After that the HBs was prepared by the solid-solid reactions between mesoporous silica, transition metals and 8-hydroxyquinoline. The incorporation of HBs were characterized by SEM, FT-IR, AAS, as well as PL. The photoluminescence maxima and intensities of the HBs varied depending on the spectro-chemical series and electron configuration as well as microstructure of metal complexes and mesoporous characteristics. The photoluminescence of the products increased in the order of Coq(2)@MCM < Znq(2)@MCM < Niq(2)@MCM. The host mesoporous silica improves photoluminescence properties such that the PL intensities of Mq(2) complexes into MCM were higher than those of the free complexes because mesoporous silica can reduce the luminescence quenching and enhance the complete metal-to-ligand charge transfer of metal complexes. Especially, the Niq(2) and Znq(2) in the mesoporous silica revealed the excellent photoluminescence property.