Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Plasmonics: When silver is better than gold

22.06.2012
Silver nanostructures exhibit a resonance feature that is useful for a multitude of sensing applications.
Silver nanostructures exhibit a resonance feature that is useful for a multitude of sensing applications.

Certain metallic nanostructures are known to exhibit a distinctly asymmetric spectral feature. This characteristic feature, known as a Fano resonance, has attracted a considerable amount of attention due to its potential in sensing applications.

Fano resonance is caused by the interference of two eigenmodes (modes of electron excitations), so its shape and wavelength are sensitive to slight variations in the environment. A small change in the refractive index, for example, could lead to a big change in the Fano resonance.

So far, most of the metallic structures used to generate Fano resonances have been made of gold. The wavelength of such Fano resonances is typically in the infrared region, which is not ideal for practical sensing applications. Jing Bo Zhang and co-workers at the A*STAR Data Storage Institute have now proposed a silver dual-disk ring nanostructure for generating Fano resonance in the visible range.

The nanostructure comprises a dual-disk ring consisting of two silver disks, measuring tens of nanometers wide, placed inside a silver ring. The researchers calculated the optical modes of the structures using the finite-difference time-domain (FDTD) method. They found that the coupling between one of the dual-disk eigenmodes and one of the ring eigenmodes produces a Fano resonance just below 700 nanometers in wavelength, well within the visible spectrum.

The shape and wavelength of the Fano resonance can be finely tuned by varying the geometric parameters that define the dual-disk ring structure. The key capability of a biomolecule sensor is its reaction to a change in the surroundings. The calculations showed that by increasing the refractive index of the environment, the Fano resonance is strongly red-shifted. This is to simulate for a case in which a thin coat of a dielectric material, such as a layer of specific biomolecules, is assumed to cover the nanostructure.

The calculations were promising but had to be verified experimentally. The researchers used electron beam lithography and corresponding nanoprocessing techniques to fabricate silver dual-disk rings on quartz and indeed observed Fano resonance in the visible light range.

Observation of the Fano resonance and its sensitivity to environmental changes in the visible range is an important result for sensing applications. The researchers aim to improve the design of the nanostructure further. “We have already determined and fabricated the optimum geometry of dual-disk ring structures for biosensing,” says Zhang. “Next we are going to functionalize the surface of the structure chemically to examine and improve the sensing power experimentally.”

References:

Niu, L., Zhang, J. B., Fu, Y. H., Kulkarni, S. & Luk'yanchuk, B. Fano resonance in dual-disk ring plasmonic nanostructures. Optics Express 19, 22974–22981 (2011).

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

More articles from Physics and Astronomy:

nachricht Tracing aromatic molecules in the early universe
23.03.2017 | University of California - Riverside

nachricht New study maps space dust in 3-D
23.03.2017 | DOE/Lawrence Berkeley National Laboratory

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

When Air is in Short Supply - Shedding light on plant stress reactions when oxygen runs short

23.03.2017 | Life Sciences

Researchers use light to remotely control curvature of plastics

23.03.2017 | Power and Electrical Engineering

Sea ice extent sinks to record lows at both poles

23.03.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>