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We report a newly developed surface engineering approach for TiO2 nanoparticles toward transparent TiO2/silicone nanocomposites with high refractive index (RI) values. Zirconate coupling agents are adopted on the TiO2 nanoparticles for surface passivation and to enhance the dispersibility of the nanoparticles in organic substrates. The modified TiO2 nanoparticles can be uniformly dispersed in silicone, forming transparent hybrid films with an ultrahigh RI of 2.01. The preparation technique of colloidal TiO2 and polymer-based nanocomposites is simple and suitable for scalable production, which is promising for expanding the application of TiO2 materials in photonic devices.

We report the synthesis of highly dispersible zirconia (ZrO2) nanoparticles in sub-kilogram-scale by hydrothermal process coupled with alkaline hydrogen peroxide (AHP) treatment, with detailed studies on the effects of experimental parameters. Under optimized experimental condition, which was hydrothermal reaction at 110 °C for 6 h with mole ratio of sodium hydrate to zirconium carbonate basic in reactants as 2.3, pure-phase cubic-ZrO2 nanoparticles are obtained. Followed by AHP treatment of the ZrO2 nanoparticles at 50 °C for 5 h in 0.4 M hydrogen peroxide and 4 M sodium hydrate, the dispersibility of ZrO2 nanoparticles in aqueous suspension was enhanced due to the introduced Zr-OH groups on the surface. ZrO2 nanodispersion with solid content of 37 wt% in aqueous solution exhibited a uniform hydrodynamic size of 14.15 ± 5.834 nm and was stable for over six months without significant aggregates. Transparent hybrid optical resins with tunable refractive index in the range of 1.55–1.71 were prepared by solution blending method using ZrO2 nanoparticles as composite fillers in polyvinyl alcohol substrate. Compared with pure polyvinyl alcohol resin, the hybrid resin exhibits significant enhanced mechanical properties. Sub-kilogram-scale preparation of highly aqueous dispersible ZrO2 nanoparticles offers possibility for practical applications.

The white light emitting diodes (LEDs) devices based on the use of blue chips and yttrium aluminum garnet phosphors have great potential impact on energy savings in the world. However, there has been public concern over the non-visual influences of blue light on human health. Herein, we report a high-gravity-hydrolysis approach for the synthesis of transparent nanozirconia/silicone hybrid materials, which can be used as the encapsulation of white LEDs with enhanced light extraction efficiency and reduced blue light exposure. The formation of zirconia nanoparticles on silicone chains is performed in a high-gravity rotating packed bed (RPB) reactor. The homogeneous micromixing of the reactants in the RPB enables the formation of ultrasmall zirconia nanoparticles in the silicone chains. Compared with LEDs encapsulated with commercial silicone, the white LEDs packaged by nanozirconia/silicone exhibit significant enhanced luminous flux (from 13.28 to 31.34) and decreased proportion of blue light (from 3.1% to 1.8%), resulting in low correlated color temperature (4573 K). This work demonstrates a scalable and efficient approach for healthy lighting based on the commercial white LEDs technology.

The ideal product of rare-earth-doped phosphors should have uniform particle size distribution and homogeneous doping ions in each particle, and therefore, intensified micromixing at mesoscale is highly required. In this article, inspired by the concept of "mesoscience", we demonstrate the tuning of Eu3+ doping in GdBO3 microparticles at mesoscale by a high-gravity-assisted reactive precipitation-coupled calcination process. The high-gravity environment and tiny droplets generated by the high-gravity rotating packed bed (RPB) reactor lead to significant intensification of mass transfer and micromixing, which are beneficial for the homogeneous doping of Eu3+ in the host material during reactive precipitation in liquid solution. Under excitation at 395 nm, the emission spectra of the Eu3+-doped phosphors exhibit a narrow-band red emission centered at 625 nm and the highest intensity was observed at x = 0.2. The RPB products show higher intensity than that of the control group even when the reaction time was shortened to 1/6. After calculation, the quenching in the sample most likely results from dipole-dipole interactions. The chromaticity coordinates for the RPB sample was measured as (0.598, 0.341) with a quantum yield of up to 78.11%, and the phosphors exhibit good thermal stability at 423 K. The phosphors were used as the luminescent materials for light-emitting diodes (LEDs), and the devices showed good performance. Our preliminary study illustrated that high-gravity-assisted approaches are promising for tuning the doping of rare-earth ions in microparticles at mesoscale toward efficient production of phosphors for LEDs.

Zirconia-based hybrid polymers has become one of the ideal encapsulation material for light emitting diodes (LEDs) with high extraction efficiency due to their proper refractive index to those of semiconductor chips. However, the controlling of the dispersion for zirconia nanoparticles in polymeric hosts to obtain optically transparent hybrid nanocomposites has been one of the major challenges. Herein, we reported the synthesis of zirconia nanodispersion via high-gravity-assisted homogeneous precipitation in an internal circulation rotating packed bed (RPB) reactor followed by two-step modification. An alternative to conventional precipitation in batch stirred tank reactors (STR), the process intensification by high-gravity RPB results in homogeneous micromixing during the nucleation and growth of zirconia particles, which are benefit for continuous and reproducible production of ultrasmall zirconia nanoparticles. The obtained zirconia nanoparticles are purely cubic phase with narrow size-distribution in the range of 3–5 nm according to the X-ray diffraction and transmission electron microscopy characterization, which were similarity to that by the conventional methods. Nevertheless, the average hydrodynamic diameters of zirconia nanoparticles in aqueous solutions obtained by RPB methods were much smaller than those prepared in conventional STR, which enabled easy control and surface modification for highly dispersed nanodispersion in organic solvents and/or polymeric hosts. After two-step surface modification, zirconia nanoparticles with goal-directed structures were obtained, with highly dispersity in various organic solvents (e.g. toluene, trichloromethane, tetrahydrofuran, etc.) and aliphatic epoxy resin, forming transparent hybrid films with tunable refractive indexes. The preliminary applications of these zirconia nanodispersions for LEDs encapsulation were demonstrated. The light extraction efficiency of the LEDs devices packaged with zirconia/epoxy hybrid material increased by 10 percent when the doping content of zirconia nanoparticles was 0.2, compared to the devices encapsulated by original epoxy.

Ultraviolet-curable polyurethane acrylate (PUA) materials can be used in a number of important applications spanning from microfluidics, surface patterning to wearable technology. For the first time, the potential of encapsulation of modified zirconia (ZrO2 ) nanoparticles is reported in PUA-based hybrid films aimed to facilitate profoundly enhanced hardness and refractive index. By successfully manipulating the interfacial reaction conditions between ZrO2 nanoparticles and PUA film, the PUA-based nanocomposites exhibit an ultrahigh hardness of 9 and superior refractive index of 1.64 (589.3 nm). The outcomes obtained pave the way for seamless application of nanozirconia/PUA as a potent encapsulating material that provides structurally morphable, water resistant, and optically transparent light emitting diodes toward wearables devices in healthcare.