Motivated by public hazards associated with contaminated sources of drinking water, a group of scientists has successfully developed and tested tiny, glowing crystals that detect and trap heavy-metal toxins like mercury and lead.
A team led by researchers at Rutgers University used intense X-rays at Lawrence Berkeley National Laboratory (Berkeley Lab) to probe the structure of the crystals and learn how they bind to heavy metals.
The crystals, known as luminescent metal-organic frameworks (LMOFs) function like miniature, reusable sensors and traps.
Within 30 minutes, one LMOF was found to selectively take up more than 99 percent of mercury from a test mixture of heavy and light metals.
Simon Teat, a Berkeley Lab staff scientist, studied individual LMOF crystals, each measuring about 100 microns (millionths of a meter), with X-rays at the lab’s Advanced Light Source (ALS). Using diffraction patterns produced as the X-ray light struck the LMOF samples, Teat applied software tools to map their three-dimensional structure with atomic resolution.
The researcher discovered a patterned, grid-like 3-D structure containing carbon, hydrogen, oxygen, nitrogen, and zinc atoms that framed large, open channels.
The structure allows heavy metals to enter the open channels and chemically bind to the MOFs. The very open framework gives the MOFs an abundant surface area relative to their size, which allows them to filter a large amount of contaminants.
According to Jing Li, a chemistry professor at Rutgers University who led the research, the technology could be a money-saving solution.
“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 Li.
Li said that further R&D could explore lower-cost and more durable LMOFs that could last for more cycles. Researchers could also pursue the development of water filters by blending the LMOFs with polymers to create a solid film.
Her team also has tested the use of MOF crystal structures for a variety of other applications, including high-explosives detection; toxin detection in foods; and new types of light-emitting components for LEDs, known as phosphors, that incorporate cheaper, more abundant materials.
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