Fabrication of europium complexes with 4'-(4-methylphenyl) 2,2':6',2"-terpyridine and 4,4'-dinonyl-2,2'-dipyridyl at the air-water interface and their emission properties in Langmuir-Blodgett films

Ternary europium complexes were formed at the air-water interface mediated by monolayers of 4,4'-dinonyl-2,2'-dipyridyl (DNDPy) and 4'-(4-methylphenyl)-2,2':6',2"-terpyridine (MPTPy). A saturated Eu(TTA)₃ (TTA: theonyltrifluoroacetone) aqueous solution was used as subphase, on the surface of which condensed DNDPy and MPTPy monolayers could be stabilized. The DNDPy-/MPTPy-Eu(TTA)3 layers were transferred onto either hydrophobic or hydrophilic substrate surfaces by Langmuir-Blodgett (LB) method. Fluorescence spectra showed several sharp peaks corresponding to Eu³⁺ emissions from  ⁵D₁ → ⁷F₁ (535 nm) and ⁵D₀ → ⁷F_0,1,2,3 (580, 595, 612 and 650 nm). A relative stronger emission from ⁵D₁ → ⁷F₁ to that from ⁵D₀ → ⁷F₂ was recorded for the LB films of DNDPy-Eu(TTA)3 complex. Compared with that in solution, longer fluorescence lifetime was observed for the complexes in the LB films.