Journal of Luminescence 101 (2003) 135–140 Multicolor emission from terpyridine–lanthanide ion complexes encapsulated in nanocomposite silica/poly(ethylene glycol) sol–gel matrices Vlasoula Bekiari, Panagiotis Lianos* Engineering Science Department, University of Patras, 26500 Patras, Greece Received 28 February 2002; received in revised form 19 June 2002; accepted 23 July 2002 Abstract Complex formation between Terpyridine and trivalent metal cations, namely In 3+ , Eu 3+ and Tb 3+ 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. r 2002 Elsevier Science B.V. All rights reserved. PACS: 7855.m; 8120.Fw Keywords: Terpyridine; Lanthanide; Sol–gel 1. Introduction Luminescent lanthanide ions are basic compo- nents of fluorescent lamps, cathode ray tubes, lasers and other light-generating devices. Their choice is dictated by the fact that they emit light in very narrow spectral bands, thus providing high chromatic purity, while the lifetime of their excited state is long, so that they make efficient phosphors. In addition to the above applications, which are around since several decades and they are very well known, lanthanides emitting visible light have recently acquired renewed interest as components of light conversion molecular devices [1]. The study of such devices has obtained large ground since the notion of the ‘‘antenna effect’’ has been introduced [2–4]. This term is used for complexes of lanthanide ions with light-harvesting ligands, where short wavelength light is absorbed by the ligand and then energy is transferred to the metal which emits light at much longer wavelength. The antenna effect offers luminescent lanthanides *Corresponding author. Tel.: +30-61-997587; fax: +30-61- 997803. E-mail address: lianos@upatras.gr (P. Lianos). 0022-2313/03/$-see front matter r 2002 Elsevier Science B.V. All rights reserved. PII:S0022-2313(02)00405-2