Scientists in Australia have created plants with integrated nanomaterials called metal organic frameworks (MOFs). These ‘super plants’ could be useful for detecting indoor air pollution – or for improving airport security by sensing explosives or other volatile chemicals, they reported at the ACS meeting in Orlando in April 2019.
MOFs – comprising metal ions or clusters linked to organic molecules – usefully act as molecular sponges for soaking up chemicals in the environment. Chemists have created thousands of them in the laboratory. However, in this work the researchers coaxed the plants to make or self- assemble the MOFs themselves, by placing the plants or plant cuttings into a solution of water containing the precursor metal salts and organic linker compounds.
‘We assembled two types of MOFs as plants sucked up the starting ingredients through the roots,’ explained Joseph Richardson at the University of Melbourne. ‘This is the first time a nanomaterial has been assembled inside a plant.’
The MOF crystals grew throughout the plants, and fluoresced green or orange-red depending whether they contained Tb or Eu, respectively. In the presence of low concentrations of acetone in water, MOF-producing lotus plant clippings were observed to fluoresce less brightly, providing a proof-of-concept for their use as sensors.
Meanwhile, MOFs could also have other applications as plant coatings, by converting harmful UV rays into light that can be useful for photosynthesis to boost plant growth. This could be especially useful, Richardson said, ‘as we contemplate growing crops in space or on Mars, where you don’t have an atmosphere and are bombarded by UV rays.’
The team coated clippings of chrysanthemum and lilyturf with luminescent MOFs and then exposed the plants to UVC light for three hours, and found that they showed less wilting and bleaching. Next, they plan to investigate the effects on plant growth. While many MOFs are inedible, some are approved in iron supplements, Richardson pointed out.