Published March 2, 2022
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From Khoi-San indigenous knowledge to bioengineered CeO2 nanocrystals to exceptional UV-blocking green nanocosmetics.

Creators

  • 1. College of Graduate Studies, UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, Muckleneuk Ridge, PO Box 392, Pretoria, South Africa. Ntombi.Ditlopo@dst.gov.za.
  • 2. Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, PO Box 722, Somerset West, 7129, Western Cape, South Africa. Ntombi.Ditlopo@dst.gov.za.
  • 3. College of Graduate Studies, UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, Muckleneuk Ridge, PO Box 392, Pretoria, South Africa.
  • 4. Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, PO Box 722, Somerset West, 7129, Western Cape, South Africa.
  • 5. Physics Deptartment, TUCAS Campus, Thiruvalluvar University Serkadu, Vellore, 632115, India.
  • 6. P.G. and Research Physics Department, A M Jain College, University of Madras, Meenambakkam, Tamil Nadu, 600114, India.
  • 7. Physics Department, University of Nottingham, Nottingham, UK.
  • 8. University of Nottingham
  • 9. IMMM, UMR 6283 CNRS, University of Le Maine, Bd O. Messiaen, 72085, Le Mans Cedex 09, France.
  • 10. International Organization for Chemistry in Development, Liege, Belgium.
  • 11. College of Graduate Studies, UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, Muckleneuk Ridge, PO Box 392, Pretoria, South Africa. Maazam@unisa.ac.za.
  • 12. Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, PO Box 722, Somerset West, 7129, Western Cape, South Africa. Maazam@unisa.ac.za.

Description

Single phase CeO2 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 CeO2 exhibited a unique UV selectivity, in a form of a Heaviside function-like type profile in the solar spectrum. While the UV reflectivity is significantly low; within the range of 0.7%, it reaches 63% in the VIS and NIR. Their relative Reactive Oxygen Species (ROS) production was found to be < 1 within a wide range of concentration (0.5-1000 μg/ml). This exceptional photostability conjugated to a sound UV selectivity opens a potential horizon to a novel family of green nano-cosmetics by green nano-processing.
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