This field is known as plasmonics because scientists are trying to take advantage of plasmons, electrons that have been "excited" by light in a phenomenon that produces electromagnetic field enhancement. The enhancement achieved by metals at the nanoscale is significantly higher than that achievable with any other material.
This is an artistic representation of the film-nanoparticle plasmonic system. Spherical gold nanoparticles are coupled to a gold film substrate by means of an ultrathin layer that forbids the particles from directly touching the film. Electromagnetic ultra-hot spots are excited in the gaps. The system enables the science of light on a scale of a few tenths of a nanometer, the diameter of a typical atom.
Credit: Sebastian Nicosia and Cristian Ciracì
Until now, researchers have been unable to quantify plasmonic interactions at very small sizes, and thus have been unable to quantify the practical limitations of light enhancement. This new knowledge gives them a roadmap for precisely controlling light scattering that should help in the development of devices, such as medical sensors and integrated photonic communications components.
Typically, plasmonic devices involve the interactions of electrons between two metal particles separated by a very short distance. For the past 40 years, scientists have been trying to figure out what happens when these particles are brought closer and closer, at sub-nanometer distances.
"We were able to demonstrate the accuracy of our model by studying the optical scattering from gold nanoparticles interacting with a gold film," said Cristian Ciracì, postdoctoral researcher at Duke's Pratt School of Engineering. "Our results provide a strong experimental support in setting an upper limit to the maximum field enhancement achievable with plasmonic systems."
The results of the experiments, which were conducted in the laboratory of David R. Smith, William Bevan Professor of electrical and computer engineering at Duke, appear on the cover of Science, Aug. 31, 2012.
Ciracì and his team started with a thin gold film coated with an ultra-thin monolayer of organic molecules, studded with precisely controllable carbon chains. Nanometric gold spheres were dispersed on top of the monolayer. Essential to the experiment was that the distance between the spheres and the film could be adjusted with a precision of a single atom. In this fashion, the researchers were able to overcome the limitations of traditional approaches and obtain a photonic signature with atom-level resolution.
"Once you know maximum field enhancement, you can then figure out the efficiencies of any plasmonic system," Smith said. "It also allows us to 'tune' the plasmonic system to get exact predictable enhancements, now that we know what is happening at the atomic level. Control over this phenomenon has deep ramifications for nonlinear and quantum optics."
The Duke team worked with colleagues at Imperial College, specifically Sir John Pendry, who has long collaborated with Smith.
"This paper takes experiment beyond nano and explores the science of light on a scale of a few tenths of a nanometer, the diameter of a typical atom," said Pendry, physicist and co-director of the Centre for Plasmonics and Metamaterials at Imperial College. "We hope to exploit this advance to enable photons, normally a few hundred nanometers in size, to interact intensely with atoms which are a thousand times smaller."
The research was supported by the Air Force Office of Scientific Research and by the Army Research Office's Multidisciplinary University Research Initiative (MURI).
The other members of the team were Duke's Ryan Hill, Jack Mock, Yaroslav Urzhumov and Ashutosh Chilkoti; and from Imperial College, Antonio Fernández-Domínguez and Stefan Maier.
Richard Merritt | EurekAlert!
Bergamotene - alluring and lethal for Manduca sexta
21.04.2017 | Max-Planck-Institut für chemische Ökologie
How to color a lizard: From biology to mathematics
13.04.2017 | Université de Genève
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
23.06.2017 | Physics and Astronomy
23.06.2017 | Life Sciences
23.06.2017 | Information Technology