Brightest nanoparticles shun quantum
R Colin Johnson
1/19/2011 12:40 PM EST
PORTLAND, Ore.—The crown for the world's brightest nanoparticles has been claimed by the inventor of mesoporous silicon-dioxide (silica) nanoparticles, which have proven to be 34-times brighter than the brightest quantum dots—previously the world's brightest nanoparticles. The transparent silicon-dioxide hulls harbored fluorescent nanoparticles inside—rather than use quantum-confinement like quantum dots—enabling much brighter operation, according to their inventors at Clarkson University (Potsdam, New York).
The mesoporous silica nanoparticles have potential applications in medicine, biology, material science, and environmental protection, according to Clarkson University Physics professor Igor Sokolov, who claims that his brighter particles will allow much finer detection of environmental pollutants, biosensors and homeland defense detectors.
Fluorescent nanoparticles work by absorbing light of one wavelength, the emitting it at another. By functionalizing the particles so that they fluoresce only when in the presence of the substance to be detected, ultra-sensitive nanoparticles can detect smaller amounts of the pollutant or toxin that would otherwise be possible. To date, quantum dots were the world's brightest nanoparticles, but Clarkson University now claims that its mesoporous silica nanoparticles have won that crown.
Sokolov’s process securely seals a large number of organic fluorescent molecules inside nanoporous silicon dioxide hulls, which can range from 20 to 50 nanometers in diameter. As an example of their brightness, Sokolov claims that nanoparticles of just 40 nanometers in diameter are brighter than 25-30 nanometer water-dispersible quantum dots—the brightest reported quantum dots to date.
The ultra-bright particles were synthesized with the help of postdoctoral fellows Shajesh Palantavida and Eun-Bum Cho (now an assistant professor at Seoul National University of Science and Technology) along with a doctoral candidate at Clarkson, Dmytro Volkov.
Funding for the project was provided by the National Science Foundation and the U.S. Army Research Laboratory's Army Research Office.
Transmission electron microscopy (TEM) image of an ultrabright fluorescent mesoporous silica nanoparticle (image colored artificially to match the actual color of the dye in the particles).