Secrets of tunneling through energy barriers: How massless electrons tunnel through energy barriers in a carbon sheet called graphene

ScienceDaily (Nov. 7, 2011) — Electrons moving in graphene behave in an unusual way, as demonstrated by 2010 Nobel Prize laureates for physics Andre Geim and Konstantin Novoselov, who performed transport experiments on this one-carbon-atom-thick material. A review article, just published in The European Physical Journal B, explores the theoretical and experimental results to date of electrons tunneling through energy barriers in graphene.

As good an electrical conductor at room temperature as copper graphene is, it also outperforms all other known materials as a heat conductor. It is both very dense due to its honeycomb lattice structure and almost completely transparent, making it suitable, among other applications, for touch screens and light panels.

What could partly explain graphene's properties is that electrons travelling inside the material behave as if they were massless. Their behavior is described by the so-called massless Dirac equation that is normally used for high-energy particles such as neutrinos nearing the speed of light. However, electrons in graphene move at a constant speed 300 times smaller than that of light.

In this review, P.E. Allain and J.N. Fuchs, both from the Université Paris-Sud, focus on the tunneling effect occurring when Dirac electrons found in graphene are transmitted through different types of energy barriers. Contrary to the laws of classical mechanics, which govern larger scale particles that cannot cross energy barriers, electron tunneling is possible in quantum mechanics -- though only under restricted conditions, depending on the width and energy height of the barrier.

However, the Dirac electrons found in graphene can tunnel through energy barriers regardless of their width and energy height; a phenomenon called Klein tunneling, described theoretically for 3D massive Dirac electrons by the Swedish physicist Oskar Klein in 1929. Graphene was the first material in which Klein tunneling was observed experimentally, as massive Dirac electrons required energy barriers too large to be observed.

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Journal Reference:

P. E. Allain, J. N. Fuchs. Klein tunneling in graphene: optics with massless electrons. The European Physical Journal B, 2011; 83 (3): 301 DOI: 10.1140/epjb/e2011-20351-3

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Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Secrets of tunneling through energy barriers: How massless electrons tunnel through energy barriers in a carbon sheet called graphene

ScienceDaily (Nov. 7, 2011) — Electrons moving in graphene behave in an unusual way, as demonstrated by 2010 Nobel Prize laureates for physics Andre Geim and Konstantin Novoselov, who performed transport experiments on this one-carbon-atom-thick material. A review article, just published in The European Physical Journal B, explores the theoretical and experimental results to date of electrons tunneling through energy barriers in graphene.

As good an electrical conductor at room temperature as copper graphene is, it also outperforms all other known materials as a heat conductor. It is both very dense due to its honeycomb lattice structure and almost completely transparent, making it suitable, among other applications, for touch screens and light panels.

What could partly explain graphene's properties is that electrons travelling inside the material behave as if they were massless. Their behavior is described by the so-called massless Dirac equation that is normally used for high-energy particles such as neutrinos nearing the speed of light. However, electrons in graphene move at a constant speed 300 times smaller than that of light.

In this review, P.E. Allain and J.N. Fuchs, both from the Université Paris-Sud, focus on the tunneling effect occurring when Dirac electrons found in graphene are transmitted through different types of energy barriers. Contrary to the laws of classical mechanics, which govern larger scale particles that cannot cross energy barriers, electron tunneling is possible in quantum mechanics -- though only under restricted conditions, depending on the width and energy height of the barrier.

However, the Dirac electrons found in graphene can tunnel through energy barriers regardless of their width and energy height; a phenomenon called Klein tunneling, described theoretically for 3D massive Dirac electrons by the Swedish physicist Oskar Klein in 1929. Graphene was the first material in which Klein tunneling was observed experimentally, as massive Dirac electrons required energy barriers too large to be observed.

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Story Source:

The above story is reprinted from materials provided by Springer Science+Business Media.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

P. E. Allain, J. N. Fuchs. Klein tunneling in graphene: optics with massless electrons. The European Physical Journal B, 2011; 83 (3): 301 DOI: 10.1140/epjb/e2011-20351-3

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Space telescopes reveal secrets of turbulent black hole

ScienceDaily (Sep. 30, 2011) — Supermassive black holes at the hearts of active galaxies swallow large amounts of gas. During this feast they spill a lot of their 'food', which is discharged in turbulent outbursts. An international team of astronomers has revealed some striking features of such an outburst around a supermassive black hole in a distant galaxy. They found a very hot 'convertor' corona hovering above the black hole and cold gas 'bullets' in hotter diffuse gas, speeding outwards with velocities up to 700 km/s.

Unlike popular belief, not all the matter around a black hole is swallowed up. A disc of infalling gas forms around the black hole. On the journey inwards the gas and dust emit large amounts of X-ray and UV radiation. This radiation can be so strong that it diverts a part of the gas inflow. It causes winds flowing outward with velocities up to several hundreds of km/s. An international team of astronomers led by Dr. Jelle Kaastra from the SRON Netherlands Institute for Space Research took the opportunity to observe and map such an extreme environment around one of the brightest supermassive black holes known to us. This 'monster' black hole -- in the distant galaxy Markarian 509 -- has a mass 300 million times that of the Sun.

Convertor corona

The Markarian 509 black hole is surrounded by a disc of gas shining bright in ultraviolet light. This emission varies in a synchronised way with emissions observed at the low end of the X-ray band, some 100s of times higher in energy than visible light. "The only way to explain this is by having gas hotter than that in the disc, a so-called 'corona', hovering above the disc," Jelle Kaastra says. "This corona absorbs and reprocesses the ultraviolet light from the disc, energising it and converting it into X-ray light. It must have a temperature of a few million degrees. Using five space telescopes, which enabled us to observe the area in unprecedented detail, we actually discovered a very hot 'corona' of gas hovering above the disc. This discovery allows us to make sense of some of the observations of active galaxies that have been hard to explain so far."

Cold gas bullets

The X-ray spectrum obtained with the Reflection Grating Spectrometer (RGS) of the space telescope XMM-Newton is the best obtained so far of such a system. It reveals unprecedented details of its gaseous environment. For the first time it has been possible to show that the outflow consists of at least five distinct components with temperatures ranging between 20.000 to a million degrees. The superb ultraviolet spectrum obtained by the Cosmic Origins Spectrograph of the Hubble Space Telescope reveals that the coolest gas in the line of sight towards Markarian 509 has 14 different velocity components at various locations in the innermost parts of this galaxy. Thus far only seven velocity components were identified.

The combined X-ray and UV measurements demonstrate that most of the visible outflowing gas is blown off from a dusty gas torus surrounding the central region more than 15 light years away from the black hole. This outflow consists of dense, cold blobs or gas bullets embedded in hotter diffuse gas. "Even at a distance of 15 light years, the energy released near the black hole manages to blow off gas from the dusty torus that surrounds the disc of infalling gas," Kaastra says.

Signs of cosmic collision

Further outwards, the signatures of the interstellar gas of the host galaxy are seen. That gas is strongly ionised by the central X-ray source: atoms are stripped of some or most of their electrons when illuminated by the powerful flux of X-rays. Even further out, at hundred thousands of light years, the X-ray light shines through gas falling in towards Markarian 509 with speeds of 200 km/s. This gas may point at a collision with a smaller galaxy in the past, that may have triggered the activity of Markarian 509.

Space telescopes

Five large space telescopes were involved in this hundred days campaign that took place in late 2009. The heart of the campaign consisted of repeated visible, X-ray and gamma-ray observations with ESA's XMM-Newton and INTEGRAL satellites, which monitored Markarian 509 for six weeks. This was followed by long observations with NASA's Chandra X-ray satellite, using the Low Energy Transmission Grating, and the NASA/ESA Hubble Space Telescope using the new Cosmic Origins Spectrograph. Prior to these observations short snapshots to monitor the behaviour of the source at all wavelengths were taken with the Swift satellite.

The combined efforts of all these instruments and astronomers gave an unprecedented insight into the core of an active galaxy. Right in the middle of the campaign the source went into outburst. The physical changes due to this outburst could be followed over the electromagnetic spectrum from visible light to X-rays.

Papers

The international consortium responsible for this campaign consists of 26 astronomers from 21 institutes on 4 continents. The first results of this campaign will be published as a series of 7 papers in Astronomy and Astrophysics, titled Multiwavelength campaign on Mrk 509 (see below). More results are in preparation.

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Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by SRON Netherlands Institute for Space Research.

Journal References:

J. S. Kaastra, P.-O. Petrucci, M. Cappi, N. Arav, E. Behar, S. Bianchi, J. Bloom, A. J. Blustin, G. Branduardi-Raymont, E. Costantini, M. Dadina, R. G. Detmers, J. Ebrero, P. G. Jonker, C. Klein, G. A. Kriss, P. Lubinski, J. Malzac, M. Mehdipour, S. Paltani, C. Pinto, G. Ponti, E. M. Ratti, R. A. N. Smith, K. C. Steenbrugge, C. P. de Vries. Multiwavelength campaign on Mrk 509: I. Variability and spectral energy distribution. Astronomy & Astrophysics, 2011; 534: A36 DOI: 10.1051/0004-6361/201116869J. S. Kaastra, C. P. de Vries, K. C. Steenbrugge, R. G. Detmers, J. Ebrero, E. Behar, S. Bianchi, E. Costantini, G. A. Kriss, M. Mehdipour, S. Paltani, P.-O. Petrucci, C. Pinto, G. Ponti. Multiwavelength campaign on Mrk 509: II. Analysis of high-quality Reflection Grating Spectrometer spectra. Astronomy & Astrophysics, 2011; 534: A37 DOI: 10.1051/0004-6361/201116870R. G. Detmers, J. S. Kaastra, K. C. Steenbrugge, J. Ebrero, G. A. Kriss, N. Arav, E. Behar, E. Costantini, G. Branduardi-Raymont, M. Mehdipour, S. Bianchi, M. Cappi, P. Petrucci, G. Ponti, C. Pinto, E. M. Ratti, T. Holczer. Multiwavelength campaign on Mrk 509: III. The 600 ks RGS spectrum: unravelling the inner region of an AGN. Astronomy & Astrophysics, 2011; 534: A38 DOI: 10.1051/0004-6361/201116899M. Mehdipour, G. Branduardi-Raymont, J. S. Kaastra, P. O. Petrucci, G. A. Kriss, G. Ponti, A. J. Blustin, S. Paltani, M. Cappi, R. G. Detmers, K. C. Steenbrugge. Multiwavelength campaign on Mrk 509: IV. Optical-UV-X-ray variability and the nature of the soft X-ray excess. Astronomy & Astrophysics, 2011; 534: A39 DOI: 10.1051/0004-6361/201116875J. Ebrero, G. A. Kriss, J. S. Kaastra, R. G. Detmers, K. C. Steenbrugge, E. Costantini, N. Arav, S. Bianchi, M. Cappi, G. Branduardi-Raymont, M. Mehdipour, P. O. Petrucci, C. Pinto, G. Ponti. Multiwavelength campaign on Mrk 509: V. Chandra-LETGS observation of the ionized absorber. Astronomy & Astrophysics, 2011; 534: A40 DOI: 10.1051/0004-6361/201117067G. A. Kriss, N. Arav, J. S. Kaastra, J. Ebrero, C. Pinto, B. Borguet, D. Edmonds, E. Costantini, K. C. Steenbrugge, R. G. Detmers, E. Behar, S. Bianchi, A. J. Blustin, G. Branduardi-Raymont, M. Cappi, M. Mehdipour, P. Petrucci, G. Ponti. Multiwavelength campaign on Mrk 509: VI. HST/COS observations of the far-ultraviolet spectrum. Astronomy & Astrophysics, 2011; 534: A41 DOI: 10.1051/0004-6361/201117123K. C. Steenbrugge, J. S. Kaastra, R. G. Detmers, J. Ebrero, G. Ponti, E. Costantini, G. A. Kriss, M. Mehdipour, C. Pinto, G. Branduardi-Raymont, E. Behar, N. Arav, M. Cappi, S. Bianchi, P.-O. Petrucci, E. M. Ratti, T. Holczer. Multiwavelength campaign on Mrk 509: VII. Relative abundances of the warm absorber. Astronomy & Astrophysics, 2011; 534: A42 DOI: 10.1051/0004-6361/201117304

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Space telescopes reveal secrets of turbulent black hole

ScienceDaily (Sep. 30, 2011) — Supermassive black holes at the hearts of active galaxies swallow large amounts of gas. During this feast they spill a lot of their 'food', which is discharged in turbulent outbursts. An international team of astronomers has revealed some striking features of such an outburst around a supermassive black hole in a distant galaxy. They found a very hot 'convertor' corona hovering above the black hole and cold gas 'bullets' in hotter diffuse gas, speeding outwards with velocities up to 700 km/s.

Unlike popular belief, not all the matter around a black hole is swallowed up. A disc of infalling gas forms around the black hole. On the journey inwards the gas and dust emit large amounts of X-ray and UV radiation. This radiation can be so strong that it diverts a part of the gas inflow. It causes winds flowing outward with velocities up to several hundreds of km/s. An international team of astronomers led by Dr. Jelle Kaastra from the SRON Netherlands Institute for Space Research took the opportunity to observe and map such an extreme environment around one of the brightest supermassive black holes known to us. This 'monster' black hole -- in the distant galaxy Markarian 509 -- has a mass 300 million times that of the Sun.

Convertor corona

The Markarian 509 black hole is surrounded by a disc of gas shining bright in ultraviolet light. This emission varies in a synchronised way with emissions observed at the low end of the X-ray band, some 100s of times higher in energy than visible light. "The only way to explain this is by having gas hotter than that in the disc, a so-called 'corona', hovering above the disc," Jelle Kaastra says. "This corona absorbs and reprocesses the ultraviolet light from the disc, energising it and converting it into X-ray light. It must have a temperature of a few million degrees. Using five space telescopes, which enabled us to observe the area in unprecedented detail, we actually discovered a very hot 'corona' of gas hovering above the disc. This discovery allows us to make sense of some of the observations of active galaxies that have been hard to explain so far."

Cold gas bullets

The X-ray spectrum obtained with the Reflection Grating Spectrometer (RGS) of the space telescope XMM-Newton is the best obtained so far of such a system. It reveals unprecedented details of its gaseous environment. For the first time it has been possible to show that the outflow consists of at least five distinct components with temperatures ranging between 20.000 to a million degrees. The superb ultraviolet spectrum obtained by the Cosmic Origins Spectrograph of the Hubble Space Telescope reveals that the coolest gas in the line of sight towards Markarian 509 has 14 different velocity components at various locations in the innermost parts of this galaxy. Thus far only seven velocity components were identified.

The combined X-ray and UV measurements demonstrate that most of the visible outflowing gas is blown off from a dusty gas torus surrounding the central region more than 15 light years away from the black hole. This outflow consists of dense, cold blobs or gas bullets embedded in hotter diffuse gas. "Even at a distance of 15 light years, the energy released near the black hole manages to blow off gas from the dusty torus that surrounds the disc of infalling gas," Kaastra says.

Signs of cosmic collision

Further outwards, the signatures of the interstellar gas of the host galaxy are seen. That gas is strongly ionised by the central X-ray source: atoms are stripped of some or most of their electrons when illuminated by the powerful flux of X-rays. Even further out, at hundred thousands of light years, the X-ray light shines through gas falling in towards Markarian 509 with speeds of 200 km/s. This gas may point at a collision with a smaller galaxy in the past, that may have triggered the activity of Markarian 509.

Space telescopes

Five large space telescopes were involved in this hundred days campaign that took place in late 2009. The heart of the campaign consisted of repeated visible, X-ray and gamma-ray observations with ESA's XMM-Newton and INTEGRAL satellites, which monitored Markarian 509 for six weeks. This was followed by long observations with NASA's Chandra X-ray satellite, using the Low Energy Transmission Grating, and the NASA/ESA Hubble Space Telescope using the new Cosmic Origins Spectrograph. Prior to these observations short snapshots to monitor the behaviour of the source at all wavelengths were taken with the Swift satellite.

The combined efforts of all these instruments and astronomers gave an unprecedented insight into the core of an active galaxy. Right in the middle of the campaign the source went into outburst. The physical changes due to this outburst could be followed over the electromagnetic spectrum from visible light to X-rays.

Papers

The international consortium responsible for this campaign consists of 26 astronomers from 21 institutes on 4 continents. The first results of this campaign will be published as a series of 7 papers in Astronomy and Astrophysics, titled Multiwavelength campaign on Mrk 509 (see below). More results are in preparation.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by SRON Netherlands Institute for Space Research.

Journal References:

J. S. Kaastra, P.-O. Petrucci, M. Cappi, N. Arav, E. Behar, S. Bianchi, J. Bloom, A. J. Blustin, G. Branduardi-Raymont, E. Costantini, M. Dadina, R. G. Detmers, J. Ebrero, P. G. Jonker, C. Klein, G. A. Kriss, P. Lubinski, J. Malzac, M. Mehdipour, S. Paltani, C. Pinto, G. Ponti, E. M. Ratti, R. A. N. Smith, K. C. Steenbrugge, C. P. de Vries. Multiwavelength campaign on Mrk 509: I. Variability and spectral energy distribution. Astronomy & Astrophysics, 2011; 534: A36 DOI: 10.1051/0004-6361/201116869J. S. Kaastra, C. P. de Vries, K. C. Steenbrugge, R. G. Detmers, J. Ebrero, E. Behar, S. Bianchi, E. Costantini, G. A. Kriss, M. Mehdipour, S. Paltani, P.-O. Petrucci, C. Pinto, G. Ponti. Multiwavelength campaign on Mrk 509: II. Analysis of high-quality Reflection Grating Spectrometer spectra. Astronomy & Astrophysics, 2011; 534: A37 DOI: 10.1051/0004-6361/201116870R. G. Detmers, J. S. Kaastra, K. C. Steenbrugge, J. Ebrero, G. A. Kriss, N. Arav, E. Behar, E. Costantini, G. Branduardi-Raymont, M. Mehdipour, S. Bianchi, M. Cappi, P. Petrucci, G. Ponti, C. Pinto, E. M. Ratti, T. Holczer. Multiwavelength campaign on Mrk 509: III. The 600 ks RGS spectrum: unravelling the inner region of an AGN. Astronomy & Astrophysics, 2011; 534: A38 DOI: 10.1051/0004-6361/201116899M. Mehdipour, G. Branduardi-Raymont, J. S. Kaastra, P. O. Petrucci, G. A. Kriss, G. Ponti, A. J. Blustin, S. Paltani, M. Cappi, R. G. Detmers, K. C. Steenbrugge. Multiwavelength campaign on Mrk 509: IV. Optical-UV-X-ray variability and the nature of the soft X-ray excess. Astronomy & Astrophysics, 2011; 534: A39 DOI: 10.1051/0004-6361/201116875J. Ebrero, G. A. Kriss, J. S. Kaastra, R. G. Detmers, K. C. Steenbrugge, E. Costantini, N. Arav, S. Bianchi, M. Cappi, G. Branduardi-Raymont, M. Mehdipour, P. O. Petrucci, C. Pinto, G. Ponti. Multiwavelength campaign on Mrk 509: V. Chandra-LETGS observation of the ionized absorber. Astronomy & Astrophysics, 2011; 534: A40 DOI: 10.1051/0004-6361/201117067G. A. Kriss, N. Arav, J. S. Kaastra, J. Ebrero, C. Pinto, B. Borguet, D. Edmonds, E. Costantini, K. C. Steenbrugge, R. G. Detmers, E. Behar, S. Bianchi, A. J. Blustin, G. Branduardi-Raymont, M. Cappi, M. Mehdipour, P. Petrucci, G. Ponti. Multiwavelength campaign on Mrk 509: VI. HST/COS observations of the far-ultraviolet spectrum. Astronomy & Astrophysics, 2011; 534: A41 DOI: 10.1051/0004-6361/201117123K. C. Steenbrugge, J. S. Kaastra, R. G. Detmers, J. Ebrero, G. Ponti, E. Costantini, G. A. Kriss, M. Mehdipour, C. Pinto, G. Branduardi-Raymont, E. Behar, N. Arav, M. Cappi, S. Bianchi, P.-O. Petrucci, E. M. Ratti, T. Holczer. Multiwavelength campaign on Mrk 509: VII. Relative abundances of the warm absorber. Astronomy & Astrophysics, 2011; 534: A42 DOI: 10.1051/0004-6361/201117304

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Beetle bling: Researchers discover optical secrets of 'metallic' beetles

ScienceDaily (Apr. 25, 2011) — Costa Rica was once regarded as the poorest of all the colonies of the Spanish Empire, sadly deficient in the silver and gold so coveted by conquistadors. As it turns out, all of the glittering gold and silver those explorers could have ever wanted was there all along, in the country's tropical rainforests -- but in the form of two gloriously lustrous species of beetle.

Today, the brilliant gold- (Chrysina aurigans) and silver-colored (Chrysina limbata) beetles have given optics researchers new insights into the way biology can recreate the appearance of some of nature's most precious metals, which in turn may allow researchers to produce new materials based on the natural properties found in the beetles' coloring.

A team of researchers at the University of Costa Rica has found that the beetles' metallic appearance is created by the unique structural arrangements of many dozens of layers of exo-skeletal chitin in the elytron, a hardened forewing that protects the delicate hindwings that are folded underneath. A paper about the discovery appears in the first issue of the Optical Society's (OSA) newest open access journal, Optical Materials Express, which launched this month.

The beetles were captured in the University of Costa Rica's Alberto Brenes Mesén Biological Reserve, a tropical rainforest environment. "The metallic appearance of these beetles may allow them to be unnoticed, something that helps them against potential predators," says physicist and study leader William E. Vargas. The surface of their elytra "reflects light in a way that they look as bright spots seen from any direction," he explains. "In a tropical rainforest, there are many drops of water suspended from the leaves of trees at ground level, along with wet leaves, and these drops and wet leaves redirect light by refraction and reflection respectively, in different directions. Thus, metallic beetles manage to blend with the environment."

To interpret the cause of this metallic look, Vargas and his team assumed that a sequence of layers of chitin appears through the cuticle, with successive layers having slightly different refractive indices.. In these beetles, the cuticle, which is just 10 millionths of a meter deep, has some 70 separate layers of chitin -- a nitrogen-containing complex sugar that creates the hard outer skeletons of insects, crabs, shrimps, and lobsters. The chitin layers become progressively thinner with depth, forming a so-called "chirped" structure.

"Because the layers have different refractive indices," Vargas says, "light propagates through them at different speeds. The light is refracted through -- and reflected by -- each interface giving, in particular, phase differences in the emerging reflected rays. For several wavelengths in the visible range, there are many reflected rays whose phase differences allow for constructive interference. This leads to the metallic appearance of the beetles."

This is similar to the way in which a prism breaks white light into the colors of the rainbow by refraction, but in the case of these beetles, different wavelengths, or colors of light are reflected back more strongly by different layers of chitin. This creates the initial palette of colors that enable the beetles to produce their distinctive hues. The mystery the researchers still needed to understand in more detail, however, was how the beetles could so perfectly create the structure causing the brilliant metallic tones of silver and gold.

Using a device they specially designed to measure the reflection of light when it strikes the curved surface of the beetles' elytra, Vargas and his colleagues found that as light strikes the interface between each successive layer (the first interface being the boundary between the outside air and the top chitin layer), some of its energy is reflected and some is transmitted down to the next interface.

"This happens through the complete sequence of interfaces," Vargas says.

Because a portion of the light is reflected, it combines with light of the exact same wavelength as it passes back through layer upon layer of chitin, becoming brighter and more intense. Ocean waves can exhibit the same behavior, combining to produce rare but powerful rogue waves. In the case of the beetles, this "perfect storm" of light amplification produces not only the same colors but also the striking sheen and glimmer that we normally associate with fine jewelry.

In the two beetle species, interference patterns are produced by slightly different wavelengths of light, thus producing either silver or gold colors. "For the golden-like beetle, the constructive interference is found for wavelengths larger than 515 nm, the red part of the visible wavelength range," Vargas says, "while for the silver-like beetle it happens for wavelengths larger than 400 nm -- that is, for the entire visible wavelength range."

"The detailed understanding of the mechanism used by the beetles to produce this metallic appearance opens the possibility to replicate the structure used to achieve it," Vargas says, "and thus produce materials that, for example, might look like gold or silver but are actually synthesized from organic media."

This potentially could lead to new products or consumer electronics that can perfectly mimic the appearance of precious metals. Other products could be developed for architectural applications that require coatings with a metallic appearance. Vargas notes that in the solar industry, for example, chirped multilayer reflectors could be used as back layers supporting the active or light-absorbing medium, to improve the absorption of the back-reflected light.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Optical Society of America.

Journal Reference:

Cristian Campos-Fernández, Daniel E. Azofeifa, Marcela Hernández-Jiménez, Adams Ruiz-Ruiz, William E. Vargas. Visible light reflection spectra from cuticle layered materials. Optical Materials Express, 2011; 1 (1): 85 DOI: 10.1364/OME.1.000085

Note: If no author is given, the source is cited instead.

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View the original article here