Zinc oxide is an important and widely used physical sunscreen. The principle of UV shielding is absorption and scattering. Zinc oxide belongs to the N-type semiconductor, and the electrons on the valence band can accept the energy transition in the ultraviolet light, which is also the principle that they absorb ultraviolet light. The function of scattering ultraviolet rays is related to the particle size of the material. When the size is much smaller than the wavelength of ultraviolet rays, the particles can scatter the ultraviolet rays acting on them in various directions, thereby reducing the ultraviolet intensity in the irradiation direction. In addition, if the particle size of this material is too large, unnatural whitening will occur on the skin. Therefore, nanoscale particles have significant advantages over the usual size.
Nano-zinc oxide is a stable compound that provides a broad spectrum of UV protection (UVA and UVB), as well as antibacterial and anti-inflammatory properties, and is by far the safest and most effective ingredient in the evaluation of sunscreens in various countries. However, their extremely small size makes them more chemically active and may be absorbed by the human body, which is potentially harmful to the human body and the environment. Therefore, there is still much controversy about the use of nanometer zinc oxide.
The most worrying aspect of nanoparticles is that it releases free radicals, which increase oxidative stress and damage proteins, esters and DNA in the body. The hydroxyl radicals produced by titanium may damage DNA and cells, and the production of hydroxyl radicals by zinc may damage the DNA and cellular structure in the skin. In addition, when you apply sunscreen to wash your face or swim, or use a sunscreen with a sunscreen factor, there is a great possibility that the nano-level sunscreen contained in it will be directly eaten, so that the human body can directly absorb it.
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