Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Dark glasses go green

30.10.2001


Bright future: new glass could make shades greener
© PhotoDisc


New light-sensitive glass can be recycled cleanly.

Researchers in Japan have developed recyclable light-sensitive glass. The new ’ecoglass’ does not contain the environmentally damaging halogen elements chlorine, bromine or iodine. These elements are essential to the photochromic glass that is currently used for car windscreens, sunglasses and visual display units.

Like photographic film, today’s photochromic glasses darken because they contain compounds of silver and halogens, such as silver iodide. Ultraviolet light in sunlight gives some of the electrons in the halogen ions enough energy to move around - these electrons combine with silver ions to make neutral atoms of metallic silver. The silver atoms then aggregate into tiny particles, scattering light and turning the glass dark.



This process is reversible - some glasses go light again after a few minutes away from ultraviolet radiation, whereas others must be heated. In each case, electrons come away from the silver atoms, causing the clusters to fall apart into silver ions once more.

Instead of halogens, which react with carbon-based molecules to form toxic and carcinogenic compounds, Tetsuo Yazawa and colleagues at the National Institute of Advanced Industrial Science and Technology in Osaka add silver ions in the form of silver nitrate to a fairly standard mixture of glass ingredients1.

The silver-nitrate glass turns from clear to yellow under ultraviolet light. When the yellowed glass is heated to 500 oC for 15 minutes, it turns clear again. This colour change, from clear to yellow and back, can be repeated many times.

The researchers have not made glass in any other colours yet - a wider spectrum is needed for some applications. And the colour change has so far been produced only by several minutes of irradiation with an ultraviolet laser, rather than with natural sunlight. But the new material shows that halogens are not essential to the process.

Yazawa’s and his colleagues point out that their material might find more high-tech applications in ’optical memory’ devices that can be reversibly imprinted with information using lasers.

References
  1. Chen, S., Akai, T., Kadono, K. & Yazawa, T. A silver-containing halogen-free inorganic photochromic glass. Chemical Communications, 2001, 2090 - 2091, (2001).


PHILIP BALL | Nature News Service
Further information:
http://www.nature.com/nsu/011101/011101-8.html
http://www.nature.com/nsu/

More articles from Life Sciences:

nachricht A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht On the way to developing a new active ingredient against chronic infections
21.08.2017 | Deutsches Zentrum für Infektionsforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Stretchable biofuel cells extract energy from sweat to power wearable devices

22.08.2017 | Power and Electrical Engineering

New technique to treating mitral valve diseases: First patient data

22.08.2017 | Medical Engineering

IVAM Marketing Prize recognizes convincing technology marketing for the tenth time

22.08.2017 | Awards Funding

VideoLinks
B2B-VideoLinks
More VideoLinks >>>