Spinach leaves embedded with carbon nanotubes can detect explosives in the soil

Spinach enhanced with carbon nanotubes creates wireless explosive sensor

Image credit: Public Domain Pictures

American researchers have created nanobionic spinach that can detect explosives and send information wirelessly into a handheld device.

The spinach plants have leaves enhanced with carbon nanotubes that give them some unusual properties. The nanobionic spinach has been engineered to be sensitive to a class of chemical compounds known as nitroaromatics, which are frequently used in landmines.

The plants would grow in the ground and if they detect the nitroaromatic compounds, the carbon nanotubes in their leaves would emit a fluorescent signal that can be read by an infrared camera. The camera further relays the signal to a small computer, which then alerts the user via an email.

“This is a novel demonstration of how we have overcome the plant/human communication barrier,” explained Michael Strano, a professor of chemical engineering at the Massachusetts Institute of Technology and leader of the research team.

“Plants are very good analytical chemists. They have an extensive root network in the soil, are constantly sampling groundwater, and have a way to self-power the transport of that water up into the leaves.”

The spinach plants are described in an article in the latest issue of the journal Nature Materials.

The experiment is one of the first successful demonstrations of plant nanobionics, which involve engineering electronic systems into plants.

“The goal of plant nanobionics is to introduce nanoparticles into the plant to give it non-native functions,” said Strano, who believes plants could be used to warn against all types of pollutants and detect looming environmental disasters such as drought.

“Plants are very environmentally responsive,” he said. “They know that there is going to be a drought long before we do. They can detect small changes in the properties of soil and water potential. If we tap into those chemical signalling pathways, there is a wealth of information to access.”

MIT graduate student Min Hao Wong, the lead author of the paper, added: “These sensors give real-time information from the plant. In the case of precision agriculture, having such information can directly affect yield and margins.”

The researchers integrated the carbon nanotubes into the leaves by applying a solution of nanoparticles to the underside of the leaf.

If there are any explosive molecules in the groundwater, it takes about 10 minutes for the plant to draw them up into the leaves, where they encounter the detector.

To read the signal, the researchers shine a laser onto the leaf, prompting the nanotubes in the leaf to emit near-infrared fluorescent light. This can be detected with a small infrared camera connected to a Raspberry Pi. Smartphones would be able to detect the signal as well if an infrared filter protecting their cameras could be removed.

The signal can be detected from the distance of about 1 metre.

Min Hao Wong has started a company called Plantea, which will attempt to further develop and commercialise the technology.

The MIT team has previously created nanobionic plants Arabidopsis thaliana that were able to detect nitric oxide, hydrogen peroxide, nerve gas sarin and the explosive TNT.

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