Effects of synergetic ligands on structure and fluorescence properties of Langmuir and Langmuir–Blodgett films containing Eu(TTA)3nL

Effects of synergetic ligands of the europium complexes Eu(TTA)3nL (Eu denotes the central ion Eu(III), TTA denotes the β-diketone ligand α-thenoyltrifluoroacetone, L denotes the synergetic ligands triophenylphosphine oxide, 1,10-phenanthroline, 2,2′-bipy and H2O, respectively) on fluorescence properties and supermolecular structures of Langmuir and Langmuir–Blodgett films were studied. Experiments on the Langmuir trough showed that different supermolecular structures were formed for each complex with different synergetic ligands, in which aggregate structure was found at the air/subphase interface for Eu(TTA)3Phen and multilayer structure for the other three complexes. This result is accordance with the R values calculated in terms of their fluorescence spectra. Fluorescence enhancement was found to be in an order of the relative emission intensity of the fluorescent LB films: I(Eu(TTA)3(TPPO)2) > I(Eu(TTA)3Phen) > I(Eu(TTA)3Bipy) > I(Eu(TTA)3·2H2O). Detailed analysis on the LB film containing Eu(TTA)3(TPPO)2 revealed that the LB film containing Eu(TTA)3(TPPO)2 not only have the strongest red light emit, the best monochromacity, good miscibility with arachidic acid (AA), but also have condensed structure, controllable nanometer-scale thickness and vertical uniformity.