Newly-developed plasmonic nanoparticles have the ability to turn light into heat but researchers have been unsure how to use them to conduct electricity.
"[Researchers] suggest that the extraction of electrons generated by surface plasmons in metal nanoparticles may be optimized," a Rice University news release reported.
The team measured the speed and efficiency of "hot" electrons taken from a sheet of grapheme containing gold nanoparticles.
"We've looked at this process on a single-particle level," lead author and graduate student Anneli Hoggard said in the news release. "Instead of looking at a device that has many junctions, we've looked at one particle at a time. We had to measure a lot of particles to get good statistics."
The team determined it took 160 femtoseconds for the atom to transfer from graphene to carbon. Plasmons are "the collective excitation of free electrons in metals that, when stimulated by an energy source like sunlight or a laser, set up a harmonic oscillation of the surface charges similar to waves," the news release reported. The team scattered light that was captured with a spectrometer, which categorizes light by wavelength.
The team found plasmon excitation in gold nanoparticles produced heat so powerful it could instantly turn water into steam.
"The plasmon generates hot electrons that decay very quickly, so intercepting them is a challenge," chemist Stephan Link said in the news release. "We're now realizing these electrons can be useful."
In order to analyze single nanoparticles the team laid down nanorods on quartz and graphene beds and used a spectrometer to look at the" line width of the plasmon-scattering spectrum."
The team noticed that graphene widened the nanorods' surface plasmon response, which shortened its lifetime.
"The plasmon resonance is determined by the size and the shape of the nanoparticle," Hoggard said. "And it usually appears as a single peak for gold nanorods. But there are important parameters about the peak: The position and the width of the peak can give us information about the particle itself, or the type of environment it's in. So we looked at how the width of the peak changes when nanoparticles are introduced into an electron-accepting environment, which in this case is graphene."
"It would be fascinating if we could use this process as a source of hot electrons for catalysis and also as an analytical tool for observing such plasmon-enabled reactions. That's the big picture," link said.
