HOUSTON (Dec. 2, 2013) Humble aluminum's plasmonic properties may make it far more valuable than gold and silver for certain applications, according to new research by Rice University scientists.
Because aluminum, as nanoparticles or nanostructures, displays optical resonances across a much broader region of the spectrum than either gold or silver, it may be a good candidate for harvesting solar energy and for other large-area optical devices and materials that would be too expensive to produce with noble or coinage metals.
Until recently, aluminum had not yet been seen as useful for plasmonic applications for several reasons: It naturally oxidizes, and some studies have shown dramatic discrepancies between the resonant "color" of fabricated nanostructured aluminum and theoretical predictions.
The combined work of two Rice labs has addressed each of those hurdles in a pair of new publications.
One paper by the labs of Rice scientists Naomi Halas and Peter Nordlander, "Aluminum for Plasmonics," demonstrates that the color of aluminum nanoparticles depends not only on their size and shape, but also critically on their oxide content. They have shown that, in fact, the color of an aluminum nanoparticle provides direct evidence of the amount of oxidation of the aluminum material itself. The paper appears in the American Chemical Society (ACS) journal ACS Nano.
Manufacturing pure aluminum nanoparticles has been a roadblock in their development for plasmonics, but the Halas lab created a range of disk-shaped particles from 70 to 180 nanometers in diameter to test their properties. The researchers found that while gold nanoparticles' plasmons resonate in visible wavelengths from 550 to 700 nanometers and silver from 350 to 700, aluminum can reach into the ultraviolet, to about 200 nanometers.
The labs also characterized the weakening effect of naturally occurring but self-passivating oxidation on
|Contact: David Ruth|