Single particle Mie calculations of near micron-sized TiO2 particles predict strong light scattering dominating the visible range that would give rise to a white appearance. We demonstrate that a polydisperse collection of these "white" particles can result in the generation of visible colors through ensemble scattering. The weighted averaging of the scattering over the particle size distribution modifies the sharp, multiple, high order scattering modes from individual particles into broad variations in the collective extinction. These extinction variations are apparent as visible colors for particles suspended in organic solvent at low concentration, or for a monolayer of particles supported on a transparent substrate viewed in front of a white light source. We further exploit the color variations on optical sensitivity to the surrounding environment to promote micron-sized TiO2 particles as stable and robust agents for detecting the optical index of homogeneous media with high contrast sensitivities. Such distribution-modulated scattering properties provide TiO2 particles an intriguing opportunity to impart color and optical sensitivity to their widespread electronic and chemical platforms such as antibacterial windows, catalysis, photocatalysis, optical sensors, and photovoltaics.
Bibliographical noteFunding Information:
This research was supported by the National Research Foundation of Korea (NRF) Grant funded by the Ministry of Science ICT and Future Planning (NRF-2016M1A2A2940914 and NRF-2017R1A5A1015365) and the Basic Science Research Program through the NRF funded by the Ministry of Education (2015R1D1A1A01059229).
© 2017 American Chemical Society.
- Mie scattering
- TiO particles
- color generation
- refractive index sensors