Engineers create electroluminescent plants that can be repeatedly charged

Using specialized nanoparticles embedded in plant leaves, engineers at MIT have created an electroluminescent plant that can be charged by an LED. After 10 seconds of charging, the plants glow intensely for several minutes and can be recharged repeatedly.

These plants can produce a light 10 times brighter than the first generation of glowing plants reported by the research group in 2017.

“We wanted to create an electroluminescent plant with particles that will absorb light, store some of it and gradually emit it,” says Michael Strano, Carbon P. Dubbs professor of chemical engineering at MIT and lead author of the new study. “It’s a big step towards herbal lighting. “

“Creating ambient light with the renewable chemical energy of living plants is a bold idea,” says Sheila Kennedy, professor of architecture at MIT and author of the article who worked with Strano’s group on based lighting. of plants. “This represents a fundamental change in the way we think about living plants and electrical energy for lighting.”

The particles can also increase the light output of any other type of electroluminescent plant, including those originally developed by Strano’s lab. These plants use nanoparticles containing the enzyme luciferase, found in fireflies, to produce light. The ability to mix and match functional nanoparticles inserted into a living plant to produce new functional properties is an example of the emerging field of “plant nanobionics”.

Pavlo Gordiichuk, a former postdoctoral fellow at MIT, is the lead author of the new article, which appears in Scientists progress.

Light condenser

The Strano laboratory has been working for several years in the new field of plant nanobionics, which aims to give plants new functionalities by integrating them with different types of nanoparticles. Their first generation of light-emitting plants contained nanoparticles carrying luciferase and luciferin, which work together to give fireflies their glow. Using these particles, the researchers generated watercress plants that could emit faint light, about a thousandth of the amount needed to read, for a few hours.

In the new study, Strano and his colleagues wanted to create components that could extend the duration of light and make it brighter. They came up with the idea of ​​using a capacitor, which is part of an electrical circuit that can store electricity and release it when needed. In the case of glowing plants, a light condenser can be used to store light as photons and then gradually release it over time.

To create their “light condenser,” the researchers decided to use a type of material called phosphor. These materials can absorb visible or ultraviolet light and then slowly release it as a phosphorescent glow. The researchers used a compound called strontium aluminate, which can be turned into nanoparticles, such as phosphorus. Before incorporating them into the plants, the researchers coated the silica particles, which protects the plant from damage.

The particles, which measure several hundred nanometers in diameter, can be infused into plants through stomata, small pores located on the surface of leaves. The particles collect in a spongy layer called a mesophyll, where they form a thin film. A major finding from the new study is that the mesophyll of a living plant can be used to display these photonic particles without harming the plant or sacrificing lighting properties, the researchers said.

This film can absorb photons from sunlight or from an LED. The researchers showed that after 10 seconds of exposure to the blue LED, their plants could emit light for about an hour. The light was brightest for the first five minutes, then gradually faded. Plants can be recharged continuously for at least two weeks, as the team demonstrated during an experimental exhibit at the Smithsonian Institute of Design in 2019.

“We need an intense light, delivered as a pulse for a few seconds, and which can charge it,” says Gordiichuk. “We have also shown that we can use large lenses, like a Fresnel lens, to transfer our amplified light over a distance of over a meter. This is a good step towards creating scale illumination. that people could use. “

“The Plant Properties exhibit at the Smithsonian demonstrated a future vision where the lighting infrastructure from living plants is an integral part of the spaces where people work and live,” Kennedy said. “If living plants could be the starting point for advanced technology, plants could replace our current unsustainable urban electric lighting grid for the mutual benefit of all plant-dependent species, including humans.”

Large scale lighting

MIT researchers have found that the “light condenser” approach can work in many different plant species, including basil, watercress and tobacco, the researchers found. They were also shown to be able to illuminate the leaves of a plant called Thailand’s elephant ear, which can be over a foot wide, a size that could make the plants useful as a source of outdoor lighting.

The researchers also investigated whether the nanoparticles interfere with the normal functioning of plants. They found that over a 10-day period, plants were able to photosynthesize normally and evaporate water through their stomata. After the experiments were completed, the researchers were able to extract about 60% of the phosphorus in plants and reuse it in another plant.

Researchers at Strano’s lab are now working on combining the phosphorescent light capacitor particles with the luciferase nanoparticles they used in their 2017 study, in the hopes that the combination of the two technologies will produce plants capable of producing even brighter light, for longer periods.

This story is republished courtesy of MIT News (web.mit.edu/newsoffice/), a popular site that covers current affairs in MIT’s research, innovation and education.