Luminescent hybrid films obtained by covalent grafting of terbium complex to silica network

Luminescent hybrid thin films consisting of terbium complex covalently bonded to a silica-based network have been obtained in situ via a sol-gel approach. A new monomer, N-(4-benzoic acid-yl), N′-(propyltriethoxysilyl)urea (PABI), has been synthesized by grafting isocyanatopropyltriethoxysilane (ICPTES) to p-aminobenzoic acid and characterized by ¹H NMR, IR and MS. The monomer acts as a ligand for Tb³⁺ ion and as a sol-gel precursor. Band emission from Tb³⁺ ion due to an efficient ligand-to-metal energy transfer was observed by UV excitation. The decay curves of Tb³⁺ in the hybrid films were measured. The energy difference between the triplet state energy of PABI and the ⁵D₄ level of Tb³⁺ ion falls in the exciting range to sensitize Tb³⁺ ion fluorescence.