Nanoparticle Sensor Detects Mercury at Levels a Million Times Below Current Technology

An international team of researchers has developed a nanoparticle that is the most sensitive sensor yet for detecting the known toxin mercury in our water—an interesting and ironic use of nanotechnology, given that a number of other researchers are hard at work determining whether other nanoparticles might be hazardous to our health or the environment.

Researchers at Northwestern University in collaboration with colleagues at Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland have developed a sensor system based around a nanoparticle that can detect minute levels of mercury and other heavy metals in water and fish. 

The research ("Ultrasensitive detection of toxic cations through changes in the tunnelling current across films of striped nanoparticles"), which was published in the journal Nature Materials, has produced a sensor capable of detecting heavy metals in much smaller concentrations than today's state-of-the-art methods.

“The system currently being used to test for mercury and its very toxic derivative, methyl mercury, is a time-intensive process that costs millions of dollars and can only detect quantities at already toxic levels,” says Bartosz Grzybowski, lead author of the study, in the university press release covering the research. “Ours can detect very small amounts, over [a] million times smaller than the state-of-the-art current methods. This is important because if you drink polluted water with low levels of mercury every day, it could add up and possibly lead to diseases later on. With this system consumers would one day have the ability to test their home tap water for toxic metals.”

The device the researchers have developed is basically a commercial strip of glass covered with a nanoparticle that gives the glass a kind of coat of hair—“a kind of nano-velcro”—that can then be dipped into water for testing purposes. If a metal cation—a positively charged ion—from something like methyl mercury comes in contact with the hairs, the hairs close up around the pollutant, trapping it.

The film then becomes electrically conductive and alerts the tester to the presence of the cation. A measurement of the voltage along the nanostructure film indicates the level of contamination. The researchers also found if they shortened the length of the nano-hairs they could detect cadmium.

What sounds particularly attractive about the method is that the nanofilm can be produced at a cost of somewhere between $1 to $10 to make, according to Grzybowski.

The researchers carried out studies on water in Lake Michigan near Chicago and on a mosquito fish from the Florida Everglades. The tests of the Lake Michigan water came within the range of the measurements found by the FDA and the fish testing was nearly identical to that of the US Geological Survey.

When you see a technology that is capable of improving on the current state-of –the-art by one million times and does so in a field designed for our health and safety, you have to wonder why it seems others are so keen to find replacements for it before it’s even been determined a risk.

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Nanoclast

IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

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