Tuesday, February 8, 2011

Could luminous trees replace streetlights?

From candlelight to gaslight to electric lighting, for centuries street lights have played a key role in keeping our suburbs safe and navigable through the night.

But a group of Taiwanese scientists are set to reverse the clock with their recent discovery that illuminated trees could replace street lights.

Dr. Yen-Hsun Su and his team came upon the idea of putting gold nanoparticles within the leaves of trees to produce a luminous, reddish glow while experimenting ways to create efficient lighting without the use of highly toxic and expensive chemicals like phosphor powder.

Testing on the Bacopa caroliniana plants, it was found the use of ultraviolet light shining on leaves with gold nanoparticles triggered a red emission in the chlorophyll.

Dr. Su believes this discovery could lead to a revolution of a major part of cities’ urban infrastructure via the replacement of street lights with luminous trees and reduce electricity costs and CO2 emissions.

“In the future, bio-LED could be used to make roadside trees luminescent at night,” he said in an interview with Chemistry World.

“This will save energy and absorb CO2 as the bio-LED luminescence will cause the chloroplast to conduct photosynthesis.”

This is not the first time gold nanoparticles have been thought to hold the key to scientific discoveries.

Scientists at Shanghai Jiaotong University in China found gold nanoparticles can be used to detect viral or bacterial DNA that may cause cancer.

Earlier this year researchers at the University of Pennsylvania discovered the potential of gold nanoparticles to turn optical radiation into electrical current that creates nano-sized circuits, which, if magnified could power themselves through sunlight without the need for an electrical current.

Although the Pandora-like world of glowing trees may be a while off yet, the science is still expanding as scientists continue to use chemistry to explore inventive ways to use gold.

Associate Professor at the University of NSW’s School of Chemistry John Stride explains gold is so special because it is an inert metal, meaning it does not rust, and is a good conductor.

“Gold is a very good conductor partly due to the absence of surface corrosion. As such it is widely used as electrical contacts,” he said.

“Some researchers have used the combination of inertness and conductivity for use in bio-applications such as biosensors. Other workers foresee using plasmon excitations to heat tissue surrounding implanted nanoparticles- either gold or gold-coated- to kill tumours.”

On Dr. Su’s research, Professor Stride believes hybrid materials (such as gold nanoparticles) in which LEDs can couple to the energy stored within plants via the biochemistry of the plant are possible but questions the practical application of the discovery to street lighting.

“If one were to impregnate leaves of urban trees with hybrid-nanoparticle type materials, would the loss of the trees warrant the 'cheap' or 'novel' lighting?” he said.

“What's more, how about autumn? With gold-filled leaves -albeit very small quantities per leaf- money would literally be first growing on trees & then falling off them!

“It may provoke local authorities to clean up fallen leaves more effectively however.”

You can read a published, abridged version at news.com.au here: http://www.news.com.au/technology/glowing-trees-are-the-new-street-lights/story-e6frfro0-1226011310001

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