Monolayers of Europium Complexes with Different Long Chains and ß-Diketonate Ligands and Their Emission Properties in Langmuir-Blodgett Films

Monolayer morphology of some amphiphilic europium(III) complexes with different long chains and head groups has been investigated and directly observed at the air/water interface by Brewster angle microscopy. The domain structure and collapse processes for the monolayers of Eu complexes were closely related to the length and numbers of long chains and to the hydrophilicity of head groups of these complexes. Monolayer assembles of these complexes were fabricated by the LBmethod and a horizontal lifting technique. The emissions from both the higher excited singlet state 5D1 of the europium ion and the symmetric forbidden transition 5D0 → 7F0 are enhanced in LB films in comparison with those in solutions and solid powders. Stronger effects on europium ion emissions were revealed for the complexes with asymmetric β-diketonate ligands in LB films than for the complexes with symmetric ones. It is suggested that the nonradiative energy transfer 5D1→5D0 of europium complexes is decreased and also the closely packed arrangement has some effects on the splitting of Eu3+ ground states in LB films, especially for those with low symmetry of the ligands around central ions.