Physicists have developed a new kind of ceramic nanoparticle that they say will make it easier to track drugs in the body, screen counterfeit money and boost the ability of solar cells to capture more energy.
The onion-like particle is only 50 nanometers wide, which is about 1,000 times smaller than a human hair, or the size of a virus. It is made from layers of unusual materials: a coating of organic dye, a neodymium shell and a core made of ytterbium and thulium. Together, the layers convert invisible near-infrared light to blue and ultraviolet (UV) light with high efficiency.
The ability to convert one kind of light to another is called "up-conversion" and this particle is able to do it 100 time more efficiently than other particles.
It's important because such a particle could improve several existing technologies that use dyes, biomarkers or fluorescent tracers.
For example, the particles could be used in special inks that would be invisible to the naked eye, but glow blue when hit by a low-energy laser pulse - something almost impossible for counterfeiters to reproduce, said Tymish Y. Ohulchanskyy, deputy director University at Buffalo's Institute for Lasers, Photonics, and Biophotonics.
Ohulchanskyy said the particles could also be used to make sure that expensive drugs reach their target in the body. Currently this is done using "bio-imaging," a technique that tags cells with markers that fluoresce under ultraviolet light shined from specialized imagers.
But fluorescent markers can scatter the incoming light from the imaging device. The new nanoparticle doesn't. Rather it creates it's own "glow" during the up-conversion process.
"This is a feature that none of the other materials display," Ohulchanskyy said.
Researchers say the particle's dye acts as an antenna, gathering photons from low-energy light sources. The shell of neodymium transfers the energy to the core, where the ytterbium and thulium amass the energy of several photons at once and then emits it as a single photon of blue and UV light.
With this ability to capture and boost photons to a higher energy state, the nanoparticle could also be used to capture energy from solar panels and convert it to higher level of electric current, the team says.
Zhihong Nie, professor of chemistry at the University of Maryland and an expert in nanoparticles said he was impressed with the new three-layer particle.
"It's an outstanding paper in general," Nie said. "It's interesting to look at the energy cascade phenomena and it shouldn't be hard to replicate. I believe they should be able to scale it up."
The research was published in the journal "NanoLetters" and led by researchers at SUNY-Buffalo, the Harbin Institute of Technology in China, with contributions from the Royal Institute of Technology in Sweden; Tomsk State University in Russia; and the University of Massachusetts Medical School.