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Street lights are an important part of our urban infrastructure — they light our way home and make the roads safe at night. But what if we could create natural street lights that don’t need electricity to power them? A group of scientists in Taiwan recently discovered that placing gold nanoparticles within the leaves of trees, causes them to give off a luminous reddish glow. The idea of using trees to replace street lights is an ingenious one – not only would it save on electricity costs and cut CO2 emissions, but it could also greatly reduce light pollution in major cities.

The discovery came about accidentally after the scientists were looking for a way to create high-efficiency lighting similar to LED technology, but without using toxic chemicals such as phosphor powder. Speaking about the development, Professor Shih-Hui Chang said, “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. As a result, Dr. Yen-Hsun Wu had the idea to discover a method that is less toxic to replace phosphor powder. This is a major motivation for him to engage in the research at the first place.”

By implanting the gold nanoparticles into the leaves of the Bacopa caroliniana plants, the scientists were able to induce the chlorophyll in the leaves to produce a red emission. Under a high wavelength of ultraviolet light, the gold nanoparticles were able to produce a blue-violet fluorescence to trigger a red emission in the surrounding chlorophyll.