Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Optical materials: Holey gold

08.06.2012
Imaging nanoporous metals with beams of electrons provides deep insights into the unusual optical properties of these materials

Gold is usually thought of as being a shiny metal — however, in its porous form, gold actually appears dull and black. The surfaces of nanoporous gold are rough and the metal loses its shine.

Michel Bosman at the A*STAR Institute of Materials Research and Engineering and co-workers have now experimentally demonstrated that the dullness is a consequence of the way incoming light couples to the electrons on the gold surface1.

A beam of light hitting metal can cause all of the electrons at the surface to oscillate in unison. If the light is within an appropriate narrow band of wavelengths, it gets absorbed by the surface and creates half-matter hybrid particles known as surface plasmon polaritons (SPPs). Bosman and his team showed that the narrow-band absorption of many SPPs across a surface can combine to give the broadband high-absorption characteristics of nanoporous materials.
“Our measurements show that these materials are not black at all when looked at up close; they are actually very colorful,” explains Bosman. “They only appear black to us because we look at them from far away, where over a large area all the different colors have been absorbed.”

These effects caused by the SPPs occur at the sub-micron level. For this reason, conventional optical imaging methods do not offer the resolution necessary to view SPPs directly. In response, the team used imaging techniques based on electron beams. By firing electrons at the surface and measuring the energy that they lose during their interaction with the material, Bosman and his team were able to calculate the energy required to create a SPP, and from this they could infer the wavelength of light that it would absorb.

The researchers scanned their electron beam across both gold and silver films, which enabled them to generate a two-dimensional map showing both the wavelength of light absorbed at a particular point as well as the local surface geometry (see image). The varying shape and size of the nanopores gave rise to SPPs that absorb light at a wide range of wavelengths.

The concept could lead to improved power conversion efficiency in photovoltaic devices. “These results show that it is possible to design the color of a gold or silver film,” says Bosman. “It will, for example, be possible to more efficiently absorb the energy of sunlight, by tuning the light absorption of the gold or silver to that of the solar spectrum.”

The A*STAR-affiliated researchers contributing to this research are from the Institute for Materials Research and Engineering
Associated links
http://www.research.a-star.edu.sg/research/6507
Journal information
Bosman, M., Anstis, G. R., Keast, V. J., Clarke, J. D. & Cortie, M. B. Light splitting in nanoporous gold and silver. ACS Nano 6, 319–326 (2012).

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 Nanomaterial makes laser light more applicable
28.03.2017 | Christian-Albrechts-Universität zu Kiel

nachricht New value added to the ICSD (Inorganic Crystal Structure Database)
27.03.2017 | FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur GmbH

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

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...

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

Periodic ventilation keeps more pollen out than tilted-open windows

29.03.2017 | Health and Medicine

Researchers discover dust plays prominent role in nutrients of mountain forest ecoystems

29.03.2017 | Earth Sciences

OLED production facility from a single source

29.03.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>