Multicolor emission from terpyridine–lanthanide ion complexes encapsulated in nanocomposite silica/poly(ethylene glycol) sol–gel matrices

Complex formation between Terpyridine and trivalent metal cations, namely In3+, Eu3+ and Tb3+ have been studied in different environments. Blue, green and red emission can be obtained from Terpyridine–Europium ion complexes, stabilized by poly(ethylene glycol) (PEG) oligomers in nanocomposite organic/inorganic matrices, by single Near-UV excitation in the ligand absorption band. Nanocomposite matrices have been synthesized by the sol–gel method. Single color, efficient photoluminescence can be also obtained by varying matrix composition. This behavior is the result of combination of three different physicochemical mechanisms: complex formation between Terpyridine and metal cations in coordination with PEG; ligand cis–trans or trans–trans transformations; and energy transfer from excited ligand to lanthanide ions.