Physicist turns trees into street lights

Cities could one day be lit by glowing trees, thanks to a discovery at Taiwan’s National Cheng Kung University (NCKU).

While researching high-efficiency lighting, post-doctor Yen-Hsun Su has found that gold nanoparticles can induce luminescence in leaves.

“Light emitting diode (LED) has replaced traditional light source in many display panels and street lights on the road. A lot of light emitting diode, especially white light emitting diode, uses phosphor powder to stimulate light of different wavelengths. However, phosphor powder is highly toxic and its price is expensive,” says Yen-Hsun’s supervisor, assistant professor Shih-Hui Chang.

“As a result, Dr Yen-Hsun Wu had the idea to discover a method which is less toxic to replace phosphor powder which can harm human bodies and cause environmental pollution. This is a major motivation for him to engage in the research at the first place.”

Yen-Hsun found that by implanting the gold nanoparticles into Bacopa caroliniana plants, he could induce the chlorophyll in the leaves to produce a red emission. Under ultraviolet light, the nanoparticles produce a blue-violet fluorescence, which triggers a red luminescence in the surrounding chlorophyll.

While Bacopa caroliniana is a pretty small plant – it could barely illuminate your ankles – the team believes the technique could be applied to much larger plants.

“In the future, 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 Yen-Hsun.