Ce:Y 3 Al 5 O 12 -Poly(methyl methacrylate) Composite for White-Light- Emitting Diodes Maria Luisa Saladino,* ,† Delia Chillura Martino, † Michele A. Floriano, † Dariusz Hreniak, ‡ Lukasz Marciniak, ‡ Wieslaw Stręk, ‡ and Eugenio Caponetti †,§ † Dipartimento Scienze e Tecnologie Biologiche, Chimiche e Farmaceutiche - STEBICEF and INSTM UdR - Palermo, Universita ̀ di Palermo, Parco d’Orleans II, Viale delle Scienze pad. 17, Palermo I-90128, Italy ‡ Department of Spectroscopy of Excited States, Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Ul Okó lna 2, Wrocław, Poland § Centro Grandi Apparecchiature-UniNetLab, Universita ̀ di Palermo, Via F. Marini 14, Palermo I-90128, Italy * S Supporting Information ABSTRACT: A Ce:YAG-poly(methyl methacrylate) (PMMA) composite was prepared by using the melt compounding method. The structure and morphology were investigated by X-ray diffractometry, transmission electron microscopy, and small-angle X-ray scattering. The optical properties (emission, excitation, and fluorescence decay rate) of the composite were studied by using photoluminescence spectroscopy. The polymer-filler interactions were studied using 13 C cross-polarization magic-angle spinning NMR spectroscopy ( 13 C{ 1 H} CP-MAS NMR). The results indicated that Ce:YAG particles are well-dispersed in the PMMA matrix without loss of their luminescence properties or significant spectral shift, thus suggesting that this composite can be valuable for advanced applications in white LED manufacture. A demonstration of its efficiency in white LED devices is also reported. 1. INTRODUCTION Polymeric composites of lanthanide-doped materials were recently considered as potential candidates for the development of light-emitting diodes (LEDs), lasers, and luminescent concentrators for solar cells. 1-4 Polymers such as poly(methyl methacrylate) (PMMA), polycarbonate (PC), and polyur- ethane (PU) are adequate matrixes due to their good transmittance over the visible spectral range, their excellent mechanical properties such as plasticity, lightness, and work- ability, and the low cost of their industrial production. Yttrium aluminum garnet (YAG) doped with lanthanide ions, due to its luminescence properties, is an excellent candidate as a luminescent host. However, the YAG low compatibility and affinity with polymer matrixes hinders the uniform dispersion of large amounts of nanopowders in the polymer matrixes. Several authors have suggested some methods to overcome this difficulty. Ryszkowska prepared a nanocomposite of Tb:YAG and PU using the in situ polymerization, 4 and Nyman et al., by a solvent exchange process, encapsulated Ce:YAG nanopowder into a transparent epoxy resin without any change in the Ce:YAG emission properties. 5 In a recent work, some of us reported the preparation of a polymeric nanocomposite of Ce:YAG nanoparticles, hereafter labeled as Ce:YAG-polyMMA/MAA, by dispersing the filler in a methacrylic acid (MAA) and methyl methacrylate (MMA) mixture followed by in situ polymerization. 6 A satisfactory dispersion was obtained, and the nanoparticles maintained their luminescence properties and caused an increase of thermal stability and stiffness of PMMA. 7 However, the above proposed preparation methods are not suitable for a scale-up of the process for industrial production, and further research on this topic is needed. In this work, we propose to prepare the Ce:YAG-PMMA nanocomposite through a melt compounding method starting from a commercial Ce:YAG powder. This method, which is not expensive and can be easily scaled up, allows one to obtain large amounts of material, of any shape and size, and allows one to minimize the exposure by the operator to the carcinogenic monomer MMA used as a starting precursor for the in situ polymerization. 6 The optical properties of both the powder and the composite were characterized by using photoluminescence spectroscopy. The structure, the morphology, and the interactions between the two components were investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM), 13 C cross-polarization magic-angle spin- ning NMR ( 13 C{ 1 H} CP-MAS NMR), and small-angle X-ray scattering (SAXS). A comparison between the Ce:YAG-PMMA composite here investigated and the Ce:YAG-polyMMA/MAA was performed. The obtained composite was combined with a blue LED to evaluate its potential in a white LED assembly. Received: December 12, 2013 Revised: April 9, 2014 Article pubs.acs.org/JPCC © XXXX American Chemical Society A dx.doi.org/10.1021/jp412173g | J. Phys. Chem. C XXXX, XXX, XXX-XXX