Highly Transparent and Wide Viewing Optical Films Using Embedded Hierarchical Double-Shell Layered Nanoparticles with Gradient Refractive Index Surface

The essential improvements in the performance of light-diffusing materials for wide viewing angles in potential optoelectronic applications have attracted considerable attention. In this study, a simple and unprecedented strategy is proposed to simultaneously provide exceptional light scattering performance and high optical transparency for transparent optical thin films using hierarchical double-shell nanoparticles possessing a refractive index gradient on the nanoparticle surface. The hierarchical SiO2/TiO2/poly­(methyl methacrylate) (PMMA) double-shell layered nanoparticles induce enhanced light scattering properties by their nanolayered gradient refractive index structure. Fourier transform infrared spectroscopy and scanning electron microscopy–energy-dispersive X-ray spectroscopy analyses show the successful formation of the multiple nanolayered structure of the double-shell nanoparticles. The synthesized SiO2/TiO2/PMMA nanoparticles with a diameter of 40 nm and a TiO2 layer thickness of 4.5 nm exhibit the highest diffuse reflectance of 87% in the visible region. An ultraviolet-light-cured optical film with an extremely low content of double-shell nanoparticles exhibits efficient light scattering characteristics while maintaining high optical transparency. This study provides a facile yet effective, scalable approach to improve the viewing angle performances of optoelectronic devices and paves the new way for further studies on the wide applications of light scattering phenomenon using optically active hierarchical nanoparticles with multiple refractive indices.