Nano Sunscreen

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Water wave (ripple tank) simulation: http://www.falstad.com/ripple/

Slide 38

What could we do to inorganic clusters to prevent them from scattering visible light?

Source: Adapted from http://www.loc.gov/rr/scitech/mysteries/images/sunscreen2.jpg

Slide 39

Nanosized Inorganic Clusters

Source: Graph adapted from http://www.aims.gov.au/pages/research/projects/sunscreens/pages/sunscreens02.html

Maximum scattering occurs for wavelengths twice as large as the clusters

Make the clusters smaller (100 nm or less) and they won’t scatter visible light

Slide 40

Nano-Sunscreen Appears Clear

Source: http://www.science.org.au/sats2003/images/barber-slide3.jpg

Slide 41

Let’s Look at Some Real Data…

Three sunscreens were tested for scattering with different wavelengths of light

One contains nanosized inorganic ingredients

One contains traditional inorganic ingredients

One contains organic ingredients

Can you answer these three questions:

Which one is which and how do you know?

Will each one appear white or clear on your skin?

What size (approximately) are the clusters in each sunscreen?

Slide 42

Light Scattering by Three Sunscreens

Slide 43

In Summary…

Nanoparticle sunscreen ingredients are small inorganic clusters that:

Provide good UV protection by absorbing both UVB and UVA light

Appear clear on our skin because they are too small to scatter visible light

Source: http://www.smalltimes.com/images/st_advancednanotech_inside_.jpg

Slide

Essential Questions: Time for Answers

What are the most important factors to consider in choosing a sunscreen?

How do you know if a sunscreen has “nano” ingredients?

How do “nano” sunscreen ingredients differ from other ingredients currently used in sunscreens?