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 Using a simple, scalable method, a material that can be used as a sensor is developed
15.02.2017 | University of the Basque Country

nachricht New mechanical metamaterials can block symmetry of motion, findings suggest
14.02.2017 | University of Texas at Austin

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Biocompatible 3-D tracking system has potential to improve robot-assisted surgery

17.02.2017 | Medical Engineering

Real-time MRI analysis powered by supercomputers

17.02.2017 | Medical Engineering

Antibiotic effective against drug-resistant bacteria in pediatric skin infections

17.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>