13442 DOI: 10.1021/la9042809 Langmuir 2010, 26(16), 13442–13449 Published on Web 07/15/2010 pubs.acs.org/Langmuir © 2010 American Chemical Society Ce:YAG Nanoparticles Embedded in a PMMA Matrix: Preparation and Characterization Maria Luisa Saladino,* ,† Antonio Zanotto, † Delia Chillura Martino, † Alberto Spinella, ‡ Giorgio Nasillo, † and Eugenio Caponetti ‡,† † Dipartimento di Chimica Fisica “F. Accascina” and INSTM UdR di Palermo, Universit  a di Palermo, Parco d’Orleans II, Viale delle Scienze pad. 17, Palermo 90128, Italy, and ‡ Centro Grandi Apparecchiature, Universit  a di Palermo, Via Marini 14, Palermo 90128, Italy Received November 11, 2009. Revised Manuscript Received April 26, 2010 A Ce:YAG-poly(methyl methacrylate) composite was prepared using in situ polymerization by embedding the Ce: YAG nanopowder in a blend of methyl methacrylate (MMA) and 2-methacrylic acid (MAA) monomers and activating the photopolymerization using a radical initiator. The obtained nanocomposite was yellow and transparent. Its characterization was performed using transmission electron microscopy, small angle X-ray scattering, 13 C cross- polarization magic-angle spinning nuclear magnetic resonance, and photoluminescence spectroscopy. Results showed that Ce:YAG nanoparticles are well dispersed in the polymeric matrix whose structure is organized in a lamellar shape. The luminescence properties of the nanocomposite do not show quenching or a significant spectral shift, indicating that the nanocomposite can be useful for advanced applications such as white LED construction. 1. Introduction Yttrium aluminum garnet (Y 3 Al 5 O 12 , YAG) doped with Ce(III) and combined with GaN blue-light-emitting diodes (LED) is applied to a white light solid-state LED (WLED). 1,2 In addition, Ce:YAG can also be used in inorganic electroluminescence displays, 3 X-ray scintillators, 4,5 and fluorescence thermometers because fluorescence properties vary with temperature. 6 WLED can be obtained by a combination of nonabsorbed blue emission from a blue LED and the broad yellow emission from Ce:YAG phosphor because blue and yellow are complementary colors. 7-9 WLEDs have advantage such as higher energy efficiency, higher reliability, longer life, faster response, and lower pollution com- pared to traditional lighting. It is suggested that they have a prosperous future in the lamp market. However, at the moment, a limit is that the radiation diffusion on the particle surfaces reduces the WLED efficiency. It was suggested that nanophosphors be utilized to increase the transmission and to reduce the optical scattering loss. 10,11 The particle scattering scales as the square of the particle mass; therefore, the reduction of particle size to the nanoscale range should essentially eliminate the scattering. For this reason, in recent times research has been focused on the preparation of Ce: YAG nanoparticles using solid-state reactions 12-14 or on solution. 15-19 Prolonged heating at high temperature (around 1600 °C) is required to obtain a pure garnet phase that overcomes the competitive formation of secondary phases. However, high temperature can increase the particle size and the aggregation grade and, in particular for Ce:YAG, can causes the oxidation of Ce(III) to Ce(IV). 20 The great limit in the development and diffusion of Ce:YAG nanoparticles regards the enormous diffi- culty in finding a synthesis route that allows control of the particle morphology, size and distribution, and optical properties. In spite of this, some researchers at the University of Keio proposed a new procedure for the construction of high-efficiency LEDs using phosphor of 10 nm size. 21,22 For the development of new preparation methods, only two authors report the construction of a device and the incorporation of doped YAG nanopowders into a solid matrix. 23,24 The preparation of new transparent composites, consisting of polymers and nanopowders containing lanthanide ions, is a sector *Corresponding author. Tel: þ39 091 6459842. Fax: þ39 091 590015. E-mail: saladinoluisa@unipa.it. 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