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Nanotech Process Developed to Detect Heavy Metal Pollution

Francesco Stellacci (EPFL)

Francesco Stellacci (EPFL)

Researchers at Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland and Northwestern University in Evanston, Illinois developed a nanoscale process to test for heavy metals such as mercury and cadmium in water and fish. Their findings appear onlne in the journal Nature Materials (paid subscription required).

The process created by EPFL nanomaterials scientist Francesco Stellacci (pictured right) and chemical engineer Bartosz Grzybowski of Northwestern, with colleagues from EPFL and University of Michigan, tests for methyl mercury, a toxic and common form of mercury pollution, in minute concentrations. Mercury exposure can affect the human nervous system and harm the brain, heart, kidneys, lungs, and immune system.

Mercury is a naturally occurring element that is found in air, water and soil. When mercury in the air or in soil washes into water, according to the U.S. Environmental Protection Agency, organisms can change it into methyl mercury. The methyl mercury then is ingested by fish and seafood, with large predatory fish such as tuna and swordfish often having the highest concentrations.

Stellacci’s and Grzybowski’s process uses nanoscale fibers to trap heavy metals for testing. The new methods can make it much easier and less expensive to test for heavy metals that the authors say can encourage more continuous testing for these pollutants, which is needed because of the fluctuating nature of industrial waste disposal.

The technology uses particles of organic ligands, which are neutral ions or molecules that bind to metal atoms, configured as nanoscale fibers attached to strips of glass. When ions of methyl mercury or other heavy metals gets between the fibers, the tiny fibers bind to the metal and trap it. The fibers can be made longer or shorter to capture ions of specific target metals.

The system then measures the voltage generated by the trapped ions, with the more ions trapped by the fibers, the higher the voltage recorded. The researchers calculate that the glass strips with nanofibers would cost less than $10.00 and an entire self-contained testing system would cost a few hundred dollars. “With a conventional method,” says Stellaci, “you have to send samples to the laboratory, and the analysis equipment costs several million dollars.”

The researchers tested their process in the waters of Lake Michigan, near the Northwestern University campus, and compared the results to FDA measurements using conventional methods. They also tested the system on small mosquito fish in the Florida Everglades, a fish lower in the food chain and thus with lower mercury concentrations than tuna or swordfish, and compared those results to studies by the United States Geological Survey. In each case the the new methods yielded comparable to near-identical results.

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