Photoluminescent properties of host-guest compounds based on ion-excha
ngeable layered oxides were studied. Cs2Ti2O5, K4Nb6O17, and KNb3O8 sh
owed blue luminescence around 420-450 nm, whereas the luminescence of
KTiNbO5, CsTi2NbO7, K2Ti4O9, Cs2Ti5O11, and Cs2Ti6O13 was observed aro
und 500 nm. These results indicate that the two-dimensional sheets of
titanate and niobate hosts were photoactive. The coordination state in
layered structures is an important factor for the luminescent propert
ies. The emission spectrum of KTiNbO5 was red-shifted by replacing Kbetween the TiNbO5- layers by H+, showing that the energy structure of
the host materials was changed by the guest intercalated between the
layers. On the other hand, for layered perovskite oxides (K2La2Ti3O10
and KLaNb2O7) doped with rare earth ions in the perovskite layers, the
luminescence of the guest rare earth ions doped was observed by photo
exciting the host layered oxides. The host luminescence of the Pr3+-,
Eu3+- and Tb3+-doped layered perovskite oxides was completely quenched
, suggesting the importance of redox properties. Tb3+ intercalated in
the interlayers of Cs2Ti5O11 also showed the luminescence with the hos
t excitation. These results indicate that the excitation energy formed
by exciting the host layered oxides migrates in the two-dimensional o
xide layers and is trapped by the guest rare earth ions doped in the o
xide layer and intercalated in the interlayer, resulting in the lumine
scence. (C) 1998 Elsevier Science B.V. All rights reserved.