The synthesis of monodisperse trioctylphosphine oxide-capped EuF 3 nanoparticles N.G. Zhuravleva a , N.A. Sapoletova a , A.A. Eliseev a , A.V. Lukashin a, * , Yu.D. Tretyakov a , U. Kynast b a Department of Material Science, Moscow State University, Leninskie Gory, 119992 Moscow, Russian Federation b Fachhochschule Muenster, Steinfurt, Germany Available online 13 December 2005 Abstract Europium fluoride based systems are promising luminescent materials due to the possibility of realizing photon splitting effect, allow- ing emission of two photons in visible part of spectra after the excitation of one photon in vacuum ultraviolet. The EuF 3 nanoparticles are of special interest due to an opportunity of sensitizing fluoride particles with an light absorbing shell. In the present work the synthesis of monodisperse trioctylphosphine oxide-capped europium fluoride nanostructures is described. The diameter of obtained particles can be controlled in the range of 3–10 nm. The formation of fluoride nanoparticles was confirmed by TEM, electron diffraction, X-ray diffraction and luminescence spectroscopy. Ó 2005 Elsevier B.V. All rights reserved. 1. Introduction The rare-earth based compounds are one of the most widespread luminescent materials, due to their high photo- chemical stability, characteristic sharp emission lines of lanthanide ions and exceptional quantum efficiencies. Among them are commonly used YAG: Eu, Tb, Ce and Gd 2 O 2 S:Eu, Tb phosphors [1]. In the present-day era of nanotechnology a special attention is paid to the develop- ment of nanostructured luminophores with unusual optical properties, such as widely known semiconductor quantum dots, doped oxide nanopowders or rare earth clusters sen- sibilized by aromatic organic complexes. Rare earth fluorides were not extensively studied so far, though from the theoretical point on view they possess a peculiar feature which moves them the leading position amongst luminescent materials. This is the possibility to produce two photons by excitation with one photon in UV region [2]. At present the interest to this thematic is intensively increasing due to the international program of mercury replacement in fluorescent lamps. Usually the excitation of phosphors occurs in UV or VUV spectral regions while luminescent materials are required to convert high-energy radiation into visible light. This process always necessitates a lot of energy to be loosed for conversion. In classical luminescent lamps the maxi- mum of emission spectra is 254 nm, while for xenon lamp the maximums of emission are 147 nm (for the monomer) and 172 nm (for dimer Xe 2 ). The highest discharge energy efficiency reported for xenon (the most promising candi- date for the replacement of Hg) does not exceed 65% that is still lower than the efficiency of the mercury plasma (75%) [3]. Therefore the possibility to develop phosphors with ultrahigh quantum efficiencies (>100%) is of particu- lar interest. This process is theoretically possible: the energy of a VUV photon is more than twice the energy of visible ones. For the first time the phenomenon called quantum cutting (or two-photon luminescence, photon-cascade emission) was observed for Pr 3+ -doped fluorides in 1974 [4]. 0925-3467/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.optmat.2005.09.068 * Corresponding author. Tel./fax: +7 95 939 5931. E-mail address: alex@inorg.chem.msu.ru (A.V. Lukashin). www.elsevier.com/locate/optmat Optical Materials 28 (2006) 606–609