(Invited) Synthesis and Luminescent Characterization of Core-Shell Nanophosphors

Abstract

Core/shell phosphors were synthesized and characterized for their structural and luminescent properties. Silicates phosphors were synthesized using a wet method as core materials and one of the possible shell materials, silica, was coated through Stöber process. SiO2 shells of 15- 90 nm were homogenously coated onto the nanophosphors, with the thickness controlled by the deposition time [1]. Core/shell particles show significant enhancement of the luminescence emission intensity over that of the core only particles. The luminescence intensity with thinner SiO2 shells (15-30 nm) and thicker shells (25-50 nm) is 72% and 25% higher than that of bare core particles. It has also been previously reported to show silimilar results that the inert shells mitigate the detrimental effect of the nanophosphor particle surfaces on the photoluminescence emission properties, thereby increasing luminous output by 20-70%, depending on the core phase and shell thickness [2]. Another possible shell material is a polymer. Polymers have various refractive indices and scattering of the excitation light (reflectivity) will be reduced when the index of refraction of the suspension media is near that of the particle, or the index of refraction of the shells is between that of the suspension media and core particle. Therefore, the reflectivity which influences on the photoluminescent properties of core/shell phosphors can be adjustable when different polymers are coated. Silicate phosphors were used as cores and monomers were attached on the surface of cores using electrostatic force and then polymerization reaction occurred in order to coat on the cores. The change of emission intensity will be reported for various thicknesses of the polymers. The structural features (core and shell materials and order of deposition) will be related to the photoluminescence properties. This work is supported by the National Science Foundation, Ceramics Program Grant (DMR-1411192). 1. J. K. Han, G. A. Hirata, J. B. Talbot, and J. McKittrick, Mater. Sci Eng. B, 176, 436-441 (2011). 2. D. Cervantes-Vasquez, O. E. Contreras, and G. A. Hirata, J. Lumin., 143, 226-232 (2013).