Tiny, glowing crystals have been developed that can both detect and trap toxic heavy metals in drinking water sources.

A collaboration led by Rutgers University researchers in New Jersey used intense X-rays at Lawrence Berkeley National Laboratory (Berkeley Lab) in California to probe the structure of the crystals and learn how they bind to heavy metals.

The structure of LMOF-261, a glowing crystal designed to detect and remove heavy metals from water. Credit: Rutgers UniversityThese luminescent metal-organic frameworks (LMOFs) function like miniature, reusable sensors and traps. Individual LMOF crystals, each measuring about 100 microns, were analyzed with X-rays at the lab's Advanced Light Source (ALS).

Using diffraction patterns produced as the X-ray light struck the LMOF samples, the researchers applied software tools were applied to map 3D structures with atomic resolution using diffraction patterns produced as the X-ray light struck the LMOF samples. A patterned, grid-like 3D structure containing carbon, hydrogen, oxygen, nitrogen, and zinc atoms that framed large, open channels was observed.

The structure allows heavy metals to enter the open channels and chemically bind to the MOFs. The open framework gives the MOFs an abundant surface area relative to their size, which allows them to filter a large amount of contaminants.

Incorporating a fluorescent chemical component, or ligand, in the original framework causes the glow; the fluorescence switches off when the LMOF interacts with heavy metals.

One LMOF selectively collected more than 99% of mercury from a test mixture of heavy and light metals within 30 minutes. The researchers collected, cleaned, and reused the LMOFs for three cycles of toxic cleansing before their performance began to degrade.

Scientists from the University of Texas at Dallas and Rider University also took part in the research.