Nanoparticles make leaves glow

22 October 2010

Can street lights be replaced by trees? Taiwanese scientists believe that they can using gold nanoparticles to induce luminescence in leaves.

Light emitting diodes (LEDs) are used in street and bicycle lights as they have a higher efficiency than traditional light bulbs but even more environmentally-friendly LED's are desirable. Now Yen Hsun Su and coworkers at Academia Sinica and the National Cheng Kung University in Taipei and Tainan have tackled this problem by synthesising gold nanoparticles shaped like sea urchins and diffusing them into plant leaves to create bio-LEDs.

Chlorophyll shows bioluminescence upon high wavelength (400 nm) ultra violet excitation. In contrast, the gold nanoparticles are excited at shorter wavelengths and emit at 400 nm. By implanting the nanoparticles into Bacopa caroliniana plants, Su was able to induce the chlorophyll in the leaves to produce a red emission. In addition, the nanoparticles are able to suppress emission blinking - a known problem for gold nanoparticles -as they have a strong surface plasmon resonance which localises light on the nanoscale.

Gold nanoparticles in the leaves induce bioluminescence

'The bio-LED could be used to make roadside trees luminescent at night. This will save energy and absorb CO2 as the bio-LED luminescence will cause the chloroplast to conduct photosynthesis,' says Su.

'The way the researchers introduce these gold nano-sea urchins in live plants utilising the 400 nm photoluminescence of gold to obtain the bioluminescence of chlorophyll is impressive,' comments Krishanu Ray, an expert in nanotechnology and fluorescence at the University of Maryland in the US. 'Proper optimisation and tuning could potentially result in stronger bioluminescence,' he adds.

The researchers agree that bioluminescence efficiency needs to be improved and are also looking to apply the same strategy to other plant biomolecules.

Yuandi Li


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