Doping a highly charged, water-soluble lanthanide complex into a hydrophobic polymer for the preparation of luminescent films

Doping a highly charged water-soluble complex in a hydrophobic polymethyl methacrylate (PMMA) to form transparent film is demonstrated with using a heptaanionic tri-TbIII complex of thiacalix[4]arene-p-tetrasulfonate (TCAS), formulated as Tb3TCAS2. A bulky hydrophobic countercation, trihexyl(tetradecyl)phosphonium (THTDP+), enabled the isolation of the Tb3TCAS2 salt, which was soluble in a PMMA solution in chloroform. The drop casting of a polymer solution containing 10 wt% THTDP-Tb3TCAS2 salt yielded a transparent film with energy -transfer luminescence. Near -infrared emitting films with Yb3TCAS2 and Nd3TCAS2 were also prepared. The luminescence lifetime (tau) (1.15 ms) of 1.0 wt% Tb3TCAS2-doped PMMA films surpassed that of the salt (0.924 ms), while the luminescence quantum yield (phi) of the film (0.17) was smaller than that of the salt (0.33). DMSO was the suitable solvent for the salt, providing longer tau (1.40 ms) and larger phi (0.44) at 0.50 wt%. A low salt concentration in PMMA resulted in a long lifetime. Spin -coated films had longer lifetimes (1.47 ms) at 1.0 wt % owing to a solution -like PMMA environment preventing Tb3TCAS2 aggregation. Drop-casted films had larger phi values than spin -coated films, as the former might contain salt -like Tb3TCAS2 aggregates.