Detecting Methylmercury in Water and Fish with Gold Nanoparticle Sensors

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Current methods of measuring toxic concentrations of mercury and its derivative methyl mercury involve a time consuming laboratory process that requires millions of dollars of equipment[1].  Until now, there has been no field test for mercury concentrations that can detect levels at the EPA standard of 0.5 parts per trillion.  Conventional mercury detection methods such as Cold Vapor Atomic Fluorescence Spectrometry (CVAFS) can only detect concentrations of five nanograms per liter or above, making it inadequate for measuring anything at lower levels[2].

Scientists at Northwestern University in collaboration with Swiss scientists have created a novel test for mercury that can detect minute concentrations of mercury and other ionized heavy metals quickly in the field for orders of magnitude cheaper than the conventional CVAFS method[3].  The new test uses functionalized gold nanoparticle “hairs” attached to a piece of glass and covered in a thin film.  The sample of fish or water is placed on the sensor.  Any mercury or other ionized metals that come into contact with the “nanohairs” will be trapped by the functionalized gold, creating a circuit.  The glass plate is then inserted into a voltage measuring device that measures the voltage between the electrodes.  Higher heavy metal concentrations will lead to higher voltage measurements. 

This new sensor is very accurate, and was able to get measurements nearly identical to measurements by the USGS taken from the same samples.  Furthermore, the samples used in the research were taken from mosquito fish from the everglades.  These fish are at the bottom of the food chain and would have some of the lowest measurable mercury levels due to the lack of bioaccumulation.  These levels would be as low as or lower than concentrations found in the water of the everglades.  The sensors cost less than $10 to fabricate, and the voltage meter used to analyze the samples only costs a few hundred dollars.  This is a potential disruptive technology in mercury sensing and testing.



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This novel technology is used to test the concentration of mercury and other heavy metals in water resources and fish.





Benefit Summary: 

This technology has the potential to improve monitoring and testing of heavy metals in applications ranging from industrial to residential.


Risk Summary: 

Gold nanoparticles have been shown to accumulate in both white blood cells and renal cells in various studies undertaken on the topic. Not much is known about the potential cytotoxicity or nephrotoxicity of these nanoparticles, but they will likely be studied further. These initial results would suggest that the human health risks of gold nanowires are complex and uncertain.

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