Researchers at the University of Illinois (US) have demonstrated a method of producing fluorescent red, blue, green and yellow nanoparticles from plain-vanilla silicon wafers.
The new materials could yield microscopic lasers. They also hold the promise of putting optical communications on electronic chips. Even though silicon "is the worst material for optics," said Munir Nayfeh, a UI professor of physics, the team devised its synthesis process using "a commercial silicon wafer, the kind used to make ordinary computer chips.
"When the surface is broken up into very small particles — on the manometer scale — the [particles] become highly fluorescent," Nayfeh said. "We are making sand glow — it's kind of unbelievable, but this is what happens at these nanoscale sizes," said Nayfeh.
Sahraoui Chaieb, a professor of theoretical and applied mechanics, also demonstrated that the fluorescent nanoparticles could be made into microscopic lasers. "Their microlasing is an important step toward a laser-on-a-chip, which could some day replace wires with optical interconnects," said Chaieb, who is also a researcher at the Beckman Institute.
Because silicon is chemically benign within the human body, the new nanoparticles could find immediate applications as fluorescent markers. By attaching biological materials to the nanoparticles, their location could be traced in the body by stimulating their fluorescence with just two photons from harmless infrared beams.
Outside the body, the nanoparticles fluoresce when exposed to ultraviolet radiation, and in aggregates they lased in response to a single green mercury lamp.
"We have seen aggregates of only a few microns that directed both blue beams and even red beams from the larger particles, so it is hopeful that this may be a great gain for lasers," said Nayfeh. The researchers are currently studying the electronic properties of their nanoparticles in an attempt to create tiny memory modules that can store information on single electrons but that can be read out with optics.
"We want to see if we can store charge on these nanoparticles — they are so tiny that adding just a single electron to one of [them] can raise its potential by almost half a volt," said Nayfeh. It should be possible to build single-electron devices "requiring very little current, producing very little heat and becoming faster and smaller even at room temperature or higher," he said.
