According to the different wavelengths, ultraviolet rays are divided into short-wave regions 190-280nm, medium-wave regions 280-320nm, and long-wave regions 320-400nm. Ultraviolet rays in the short-wave region have the highest energy, but they are blocked when passing through the ozone layer. Therefore, the ultraviolet rays in the medium-wave and long-wave regions are generally harmful to the human body.
The strong UV resistance of titanium dioxide is due to its high refractive index and high photoactivity. Its anti-ultraviolet ability and its mechanism are related to its particle size: when the particle size is large, the UV is mainly blocked by reflection and scattering, and it is effective for both mid-wave and long-wave ultraviolet. The sun protection mechanism is a simple covering, which is a general physical sun protection, and the sun protection ability is weak; as the particle size decreases, the light can pass through the particle surface of titanium dioxide, and the reflection and scattering of ultraviolet rays in the long wavelength region are not obvious, and the centering The absorption of ultraviolet rays in the wave zone is obviously enhanced. Its sun protection mechanism is to absorb ultraviolet rays, mainly in the mid-wave region. It can be seen that the sunscreen mechanism of titanium dioxide for different wavelengths of ultraviolet rays is different. The long-wavelength ultraviolet rays are mainly blocked by scattering, and the medium-wavelength ultraviolet rays are mainly absorbed by absorption.
