From Khoi-San indigenous knowledge to bioengineered CeO nanocrystals to exceptional UV-blocking green nanocosmetics.

Single phase CeO nanocrystals were bio-synthesized using Hoodia gordonii natural extract as an effective chelating agent. The nanocrystals with an average diameter of 〈Ø〉 ~ 5-26 nm with 4 electronic valence of Ce displayed a remarkable UV selectivity and an exceptional photostability. The diffuse reflectivity profile of such CeO exhibited a unique UV selectivity, in a form of a Heaviside function-like type profile in the solar spectrum.