From sunblocks for people to sunblocks for outdoor surfaces, nanotechnology offers improvements which are both cosmetic and functional. The key is simple. Zinc Oxide has a very broad absorption in the ultraviolet for both UVB radiation (responsible for sunburn and skin cancer) and UVA radiation (responsible for tanning and aging effects). Luckily UVC, which is far more dangerous, is absorbed by ozone.

The thick, white zinc oxide ointments of yesterday were rejected by the public when inferior but transparent alternatives (such as PABA) hit the market. Recent advances in the reduction of zinc oxide particles to the nanoscale, however, has brought the return of the better-protecting ZnO. Why is ZnO transparent now? Because the particles, on the scale of 10 nm or less, are too small to effectively scatter light and so let visible light pass. They absorb UV because of their chemical structure and so the UV never makes it through to the skin, even though visible light does.

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