Researchers at
Rice University's Laboratory for Nanophotonics (LANP) have unveiled the nanoegg, an ultrasmall, light-focusing particle with potential uses in molecular imaging, medical diagnostics and chemical sensing.
Rice previously developed nanoshells, of similar size at 20 times smaller than a red blood cell, and able to be tuned to focus light on small regions of space. But each nanoegg interacts with about five times the number of wavelengths of light than their nanoshell cousins. Their asymmetric structure also allows them to focus more energy on a particular spot.
Like nanoshells, nanoeggs have a spherical, non-conducting core that's covered with a thin metal shell. But where the casing on a nanoshell has a uniform thickness, the nanoegg's covering is thicker on one side than the other.
The off-centre core in the nanoegg radically changes its electrical properties due to the way light interacts with electrons at the nanoscale.
Metal particles have a sea of free electrons flowing continuously over their surface called plasmons, which have a wave-like movement. When the wavelength of incoming light matches the wavelength of the plasmon, the amplitude of the waves gets bigger until it spills over as focussed light.
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