High-gravity-assisted synthesis of highly dispersible TiO2 nanoparticles for alicyclic epoxy-based nanocomposites with high refractive index and their application in LED packaging

Uniform TiO 2 nanoparticles with low polydispersity index of 0.121. • Highly dispersed TiO 2 nanoparticles in epoxy resin with high refractive index. • Enhanced luminous flux of AlGaInP LED by 30.66% using nanocomposites encapsulant. Physical blending of high-refractive-index titanium dioxide (TiO 2 ) nanoparticles into optical resins offers a novel and efficient approach to prepare high-transparency and high-refractive-index optical materials, which are promising for light-emitting diode (LED) packing and advanced displays. Efficient synthesis and uniform dispersion of inorganic nanoparticles are crucial for their commercialization. In this work, methoxy triethyleneoxypropyl trimethoxysilane (MTE-TMS) modified TiO 2 nanoparticles with excellent dispersibility were synthesized using a high-gravity-assisted rotating packed bed (RPB) reactor. The as-prepared nanoparticles possess an extremely low polydispersity index (PDI) of 0.121 and are homogeneously dispersed in alicyclic epoxy resin, namely 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylate (EEC). The resultant nanocomposite films exhibit tunable refractive indices ranging from 1.49 to 1.74, while the intrinsic refractive index of MTE-TMS-modified TiO 2 (named as M-TiO 2 ) nanoparticles is determined to reach up to 2.416. The intense mixing of RPB improves the grafting content of surface modifiers and reaction efficiency, thus achieving uniform coating on nanoparticle surfaces. With 50 wt% M-TiO 2 incorporated, the 200 μm-thick film retains transmittance over 85% in the visible region, accompanied by a haze of 0.45% and a refractive index of 1.74. The nanocomposites also possess better hardness, water resistance and thermal conductivity than pure EEC resin. When used for packaging AlGaInP-based (refractive index ≈3.0) LEDs, the materials boost the luminous flux of devices by 30.66%, showing bright prospects in high-refractive-index chip packaging.