This is a safe product that offers broad spectrum coverage against UVA and UVB without provoking allergic skin reactions. Until a few years ago, zinc oxide couldn’t be ground up finely enough to incorporate it into a transparent film. It has now been produced in a microfine form and made into a transparent formulation that offers superb sun protection against ultraviolet light. Zinc oxide crystals that are 120 nm in diameter are used, and the formulation is known commercially as Z-Cote.
Microfine zinc oxide protects against ultraviolet rays from 250 nm through the UV spectrum to about 380 nm in the UVA in which its absorbance drops to zero at 400 nm. Its closest competitor, avobenzone, covers UVA to only 365 nm.
This figure shows X-ray diffraction spectra of a sputtered thin zinc oxide film on a silicon wafer.
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