Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Nanoplasmonics - Hunt for nonlocal effects turns to gold

14.02.2014
Experiments on tiny gold prisms help to explain the unusual electrodynamics of nanostructures

Nanoplasmonics — the study of light manipulation on the nanometer scale — has contributed to the production of novel devices for chemical and biological sensing, signal processing and solar energy.

However, components at such small scales experience strange effects that classical electrodynamics cannot explain. A particular challenge for theorists lies in isolating so-called ‘nonlocal’ effects, whereby the optical properties of a particle are not constant but depend on nearby electromagnetic fields.

Now, Joel Yang and colleagues at the A*STAR Institute of Materials Research and Engineering in Singapore, with co-workers in the United Kingdom and China, have used both simulations and experiments to investigate the nonlocal effects displayed by electrons in metal nanostructures1.

The team developed three-dimensional simulations of electron-energy loss spectroscopy (EELS) spectra. EELS is a powerful laboratory technique that can provide information on nanostructure geometries, but also gives rise to nonlocal effects. An EELS device is used to fire energetic electrons at a metal nanostructure and then to measure how much energy the electrons lose when they excite plasmon resonances in the sample. Previously, it had been difficult for experimentalists to correctly interpret EELS spectra because the nonlocal effects are not considered in current theory — the relevant solutions of Maxwell’s field equations.

Yang and co-workers present the first full three-dimensional solution of Maxwell’s equations for a sample being probed by an EELS source. “Our theoretical configuration mimics the experimental setup and the equations were, for the first time, implemented and solved using commercial software,” says Yang.

The researchers applied their theory to triangular gold nanoprisms and concluded that significant nonlocal effects occur when the side length of the prisms is smaller than 10–50 nanometers, causing a spatial dispersion of electromagnetic fields. They then examined real EELS results for gold ‘bowtie’ nanostructures — each gold bowtie was created by joining two nanoprisms at their peaks using gold bridges as narrow as 1.6 nanometers (see image).

The real bowties exhibited a similar spatial field dispersion to that anticipated for single prisms, but with greatly reduced high-frequency conduction at the narrow connective bridges. The researchers speculate that the field reduction is caused by two factors not included in their model — quantum confinement in the narrow bridges as well as electron scattering from grain boundaries. These factors help to explain the interplay between nonlocality and geometry.

“Existing models tend to treat metals as having homogeneous optical properties,” says Yang. “Our results suggest that at the nanoscale we need to take account of quantum confinement and granularity.”

The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering

Journal information

Wiener, A., Duan, H., Bosman, M., Horsfield, A. P., Pendry, J. B. et al. Electron-energy loss study of nonlocal effects in connected plasmonic nanoprisms. ACS Nano 7, 6287–6296 (2013).

A*STAR Research | Research asia research news
Further information:
http://www.a-star.edu.sg
http://www.researchsea.com

More articles from Materials Sciences:

nachricht New material for digital memories of the future
19.10.2017 | Linköping University

nachricht Electrode materials from the microwave oven
19.10.2017 | Technical University of Munich (TUM)

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Electrode materials from the microwave oven

19.10.2017 | Materials Sciences

New material for digital memories of the future

19.10.2017 | Materials Sciences

Physics boosts artificial intelligence methods

19.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>