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Courtesy of Dr. Chad A. Mirkin, International Institute of Nanotechnology, Northwestern University |
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First-known nano application: Stained glass
Without understanding the underlying theory, artists in the 18th century used gold and silver particles to make red and yellow stained glass. So how does that work?
By adding gold chloride to the glass mixture, the artists introduced gold spheres that were about 25 nanometers, or 25 billionth of a meter, in diameter. At those small sizes, gold no longer glitters like gold. Electrons at the surface of the nanoparticles slosh back and forth in unison, absorbing blue and yellow light. But the particles reflect longer-wavelength red light, which passes through the window. Similarly, nanoparticles of silver in stained glass give a bright yellow hue.
Today we still take advantage of the light-absorbing and -reflecting properties of nanoparticles when we use zinc oxide in sunblock lotions.
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