Heavy metals can contaminate drinking water sources, posing a threat to public health. Publicized cases of drinking-water contamination in Flint, Mich., and Newark, N.J., motivated research into the development of tiny, customized crystals that can detect and trap waterborne heavy metals like mercury and lead.
A research team led by scientists at Rutgers University designed glowing, boxy structures called luminescent metal-organic frameworks, or LMOFs, that are made to glow by attaching a fluorescent chemical component.
The luminescence of these largely hollow LMOFs, which each measure about 100 millionths of an inch across, switches off when they interact with the heavy metals — so the absence of the luminescence signals the presence of heavy metal toxins.
“Others had developed MOFs for either the detection of heavy metals or for their removal, but nobody before had really investigated one that does both,” said Jing Li, a chemistry professor at Rutgers University who led the research.
Researchers sent samples of LMOF crystals to Simon Teat, a staff scientist at Lawrence Berkeley National Laboratory's (Berkeley Lab) Advanced Light Source to get a 3-D view of their structure. Using patterns produced as the X-ray light struck the crystals, Teat applied software tools to map the 3-D structure of the LMOFs with atomic resolution.
Knowing their structure provides clues about how the LMOFs work, and also in how to improve upon their design to further customize them for real-world applications.
In a test mixture of heavy and light metals, the LMOFs took up more than 99 percent of mercury in just 30 minutes. No other MOFs have performed as well in the dual role of detecting and capturing toxic heavy metals, the research team reported. The LMOFs can be cleaned and reused for a few cycles of decontamination.
Use your mouse to explore! The Advanced Light Source is a specialized particle accelerator that generates bright beams of x-ray light for scientific research. Electron bunches travel at nearly the speed of light in a circular path, emitting light in the process. The light is directed through about 40 beamlines (check out one of them below) to numerous experimental endstations, where scientists from around the world can conduct research in a wide variety of fields.
Researchers would like to expand on this research and develop more durable LMOFs that can last for more cleanup cycles. It is also conceivable that the LMOFs could be incorporated in a solid film to create water filters that capture contaminants on a large scale.