Photoluminescence spectra resulting from hydroxy groups on magnesium oxide supported on silica

Photoluminescent excitation and emission spectra resulting from hydroxy groups on magnesium oxide have been investigated using highly dispersed magnesium oxide species supported on silica. Since this sample has almost only one kind of Mg—O species, reaction of Mg—O species with H2O produces hydroxy groups uniformly coordinated to Mg ions. Therefore, clear photoluminescent excitation spectra were obtained. Coordination states of the hydroxy groups were elucidated from excitation spectra. The hydroxy group attached to the surface Mg ion is excited by 255 nm light. The other hydroxy groups which are coordinated to Mg ions within the silica matrix are excited by 265 nm light. Hydroxy groups on the sample exhibit almost the same broad emission spectra centred at 440 nm regardless of their coordination.