Synthesize uniform ZrO2 NPs by non-coordination solvents and modification for high refractive film

Abstract

Zirconia nanoparticles (ZrO2 NPs) are considered promising functional materials due to their high refractive index, thermal stability, and relatively wide bandgap. They can be particularly valuable when blended with monomer resins to create transparent composite materials with tunable refractive indices. However, the challenge of synthesizing uniformly sized and transparently dispersible ZrO2 NPs in organic resin monomers has been an ongoing research problem. In this study, we proposed an improved method based on an existing synthesis route for the production of ZrO2 NPs. We employed a sol-gel approach and introduced a simple yet effective strategy to synthesize ZrO2 NPs. Using high-boiling non-coordinating solvent squalane to adjust the concentration of oil amine ligands in the solution, helped to balance the nucleation and growth of ZrO2, thereby improving the size uniformity of ZrO2 NPs. In addition, the addition of sodium hydroxide (NaOH) to the reaction system effectively promoted the crystal growth of ZrO2 without affecting its crystal structure and crystallinity. Simultaneously, this addition significantly reduced the content of surface oleylamine (OAm) ligands. Finally, ZrO2 was modified using 2-Ethylhexanoic acid (EHA) and 3-methacryloxypropyltrimethoxysilane (KH-570), achieving successful transparent dispersion within the high refractive index acrylic monomer, benzyl acrylate (BZA). In-situ polymerization was used with a UV initiator to produce a refractive index continuously tunable BZA/ZrO2 composite film.