Microscopic channels of gold nanoparticles have the ability to transmit electromagnetic energy that starts as light and propagates via "dark plasmons," according to researchers at Rice University.
A new paper in the American Chemical Society journal Nano Letters shows how even disordered collections of nanoparticles in arrays as thin as 150 nanometers can be turned into waveguides and transmit signals an order of magnitude better than previous experiments were able to achieve. Efficient energy transfer on the micrometer scale may greatly improve optoelectronic devices.
The Rice lab of Stephan Link, an assistant professor of chemistry and electrical and computer engineering, has developed a way to "print" fine lines of gold nanoparticles on glass. These lines of nanoparticles can transmit a signal from one nanoparticle to the next over many microns, much farther than previous attempts and roughly equivalent to results seen using gold nanowires.
Complex waveguide geometries are far easier to manufacture with nanoparticle chains, Link said. He and his team used an electron beam to cut tiny channels into a polymer on a glass substrate to give the nanoparticle lines their shape. The gold nanoparticles were deposited into the channels via capillary forces. When the rest of the polymer and stray nanoparticles were washed away, the lines remained, with the particles only a few nanometers apart.
Plasmons are waves of electrons that move across the surface of a metal like water in a pond when disturbed. The disturbance can be caused by an outside electromagnetic source, such as light. Adjacent nanoparticles couple with each other where their electromagnetic fields interact and allow a signal to pass from one to the next.
Link said dark plasmons may be defined as those that have no net dipole moment, which makes them unable to couple to light. "But these modes are not totally dark, especially in the presence of disorder," he said. "Even for the subradiant modes, there is a small dipole oscillation.
"Our argument is that if you can couple to these subradiant modes, the scattering loss is smaller and plasmon propagation is sustained over longer distances," Link said. "Therefore, we enhance energy transport over much longer distances than what has been done before with metal-particle chains."
To see how far, Link and his team coated the 15-micron-long lines with a fluorescent dye and used a photobleaching method developed in his lab to measure how far the plasmons, excited by a laser at one end, propagate. "The damping of the plasmon propagation is exponential," he said. "At four microns, you have a third of the initial intensity value.
"While this propagation distance is short compared to traditional optical waveguides, in miniaturized circuits one only needs to cover small length scales. It might be possible to eventually apply an amplifier to the system that would lengthen the propagation distance," Link said. "In terms of what people thought was possible with nanoparticle chains, what we've done is already a significant improvement."Link said silver nanowires have been shown to carry a plasmon wave better than gold, as far as 15 microns, about a sixth the width of a human hair. "We know that if we try silver nanoparticles, we may propagate a lot longer and hopefully do that in more complex structures," he said. "We may be able to use these nanoparticle waveguides to link to other components such as nanowires in configurations that would not be possible otherwise."
Graduate student David Solis Jr. is the lead author of the paper. Co-authors are graduate students Britain Willingham, Liane Slaughter, Jana Olson and Pattanawit Swanglap, junior Scott Nauert and postdoctoral research associates Aniruddha Paul and Wei-Shun Chang, all of Rice.
The research was supported by the Robert A. Welch Foundation, the Office of Naval Research, the National Science Foundation, the American Chemical Society Petroleum Research Fund and a 3M Nontenured Faculty Grant.
Read the abstract at http://pubs.acs.org/doi/abs/10.1021/nl2039327Images for download:
Members of the lab of Rice Professor Stephan Link – from left, research associate Wei-Shun Chang and graduate students David Solis Jr. and Britain Willingham – created thin strips of gold nanoparticles to study their ability to carry electromagnetic signals via dark plasmons. (Credit: Jeff Fitlow/Rice University)
Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is known for its "unconventional wisdom." With 3,708 undergraduates and 2,374 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice has been ranked No. 1 for best quality of life multiple times by the Princeton Review and No. 4 for "best value" among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://www.rice.edu/nationalmedia/Rice.pdf
David Ruth | EurekAlert!
Researchers develop new lens manufacturing technique
21.05.2019 | Washington State University
Planetologists explain how the formation of the moon brought water to Earth
21.05.2019 | Westfälische Wilhelms-Universität Münster
Engineers at the University of Tokyo continually pioneer new ways to improve battery technology. Professor Atsuo Yamada and his team recently developed a...
With a quantum coprocessor in the cloud, physicists from Innsbruck, Austria, open the door to the simulation of previously unsolvable problems in chemistry, materials research or high-energy physics. The research groups led by Rainer Blatt and Peter Zoller report in the journal Nature how they simulated particle physics phenomena on 20 quantum bits and how the quantum simulator self-verified the result for the first time.
Many scientists are currently working on investigating how quantum advantage can be exploited on hardware already available today. Three years ago, physicists...
'Quantum technologies' utilise the unique phenomena of quantum superposition and entanglement to encode and process information, with potentially profound benefits to a wide range of information technologies from communications to sensing and computing.
However a major challenge in developing these technologies is that the quantum phenomena are very fragile, and only a handful of physical systems have been...
Working group led by physicist Professor Ulrich Nowak at the University of Konstanz, in collaboration with a team of physicists from Johannes Gutenberg University Mainz, demonstrates how skyrmions can be used for the computer concepts of the future
When it comes to performing a calculation destined to arrive at an exact result, humans are hopelessly inferior to the computer. In other areas, humans are...
Scientists develop a molecular recording tool that enables in vivo lineage tracing of embryonic cells
The beginning of new life starts with a fascinating process: A single cell gives rise to progenitor cells that eventually differentiate into the three germ...
29.04.2019 | Event News
17.04.2019 | Event News
15.04.2019 | Event News
21.05.2019 | Materials Sciences
21.05.2019 | Materials Sciences
21.05.2019 | Life Sciences