Transparent dispensible high-refractive index ZrO2/epoxy nanocomposites for LED encapsulation


Correspondence to: P. Tao (E - mail:


In this study, we report a facile ex situ approach to preparing transparent dispensible high-refractive index ZrO2/epoxy nanocomposites for LED encapsulation. Highly crystalline, near monodisperse ZrO2 nanoparticles (NPs) were synthesized by a nonaqueous approach using benzyl alcohol as the coordinating solvent. The synthesized particles were then modified by (3-glycidyloxypropyl)trimethoxysilane (GMS) ligand. It was found that, with tiny amount of surface-treating ligand, the modified ZrO2 NPs were able to be easily dispersed in a commercial epoxy matrix because of the epoxy compatible surface chemistry design as well as the small matrix molecular weight favoring mixing. Transparent thick (1 mm) ZrO2/epoxy nanocomposites with a particle core content as high as 50 wt % and an optical transparency of 90% in the visible light range were successfully prepared. The refractive index of the prepared composites increased from 1.51 for neat epoxy to 1.65 for 50 wt % (20 vol %) ZrO2 loading and maintained the same high-Abbe number as the neat epoxy matrix. Compared with the neat epoxy encapsulant, an increase of 13.2% in light output power of red LEDs was achieved with the 50 wt % ZrO2/epoxy nanocomposite as the novel encapsulant material. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3785–3793, 2013