Luminescent mechanism analyzing and metal-ion sensing of Eu(III)-organic ligands complex doped gelatin-based films and hydrogels

Abstract

A series of gelatin-based composite films (gf) were prepared by doping Eu(TTA)3(H2O)2, Eu(TTA)3bipy, or Eu(TTA)3phen respectively into type-E or -B gelatin film substrate. All of B-gf and the E-gf doped Eu(TTA)3phen were realized with red luminescence under 365 nm excitation, while only slight blue luminescence originated from gelatin substrate can be observed in E-gf doped Eu(TTA)3(H2O)2 or Eu(TTA)3bipy. A UV-absorption competition between substrate and dopant was confirmed to decide the luminescent properties of gf. Weaker UV absorption of B-gelatin ensures that Eu(TTA)3, regardless of ancillary ligand, can obtain sufficient excitation energy for luminescence emission. While only Eu(TTA)3phen possesses a strong enough ability to absorb UV against E-gelatin. Based on the optimal matching principle of substrate and dopant, luminescent gelatin-based hydrogel (gh) doped Eu(TTA)3phen was prepared. A ‘dual effect’ mechanism was proposed for explaining metal-ion sensing applications. Among various metal ions, furthermore, both B and E types of Eu(TTA)3phen@gh exhibited similar significant luminescence quenching for Fe3+ with a detection limit of about 1.15 μmol/L.