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A sensor that detects water pollution in real time

A sensor that detects water pollution in real time

Water quality monitoring is mainly carried out at water intakes or wastewater treatment plants, and not along water lines at the final water consumption site. This algorithm does not accurately reflect the quality of the water, because on the way from the source of water to your tap a negative change in the quality of water can occur. It is necessary to monitor this key natural resource for the presence of various pollutants, such as toxic ions of heavy metals and bacteria in water distribution and purification systems.

The taken sample of water is sent to a laboratory where under special conditions the culture is germinated for several days. That is, only after a certain period of time it is possible to say whether such water is safe for consumption.

That is why accurate and affordable technologies for detecting harmful substances are now necessary to ensure continuous water quality control and early warning of pollution in order to avoid public safety catastrophes.

During the 64th AVS’s International Symposium and Exhibition held in October in Tampa, Fla., Junhong Chen, a respected professor of engineering, materials science and engineering at the University of Wisconsin-Milwaukee, presented his work: a graphene-based sensing platform for low-cost water analysis in real-time mode for the detection of various water pollutants. The new sensor detects heavy metals, bacteria, nitrates and phosphates.

“This technology addresses the unmet need for monitoring critical contaminants in drinking water in real time and at low cost,” says the scientist. “Water plays an important role in the modern world, but only 3 percent of available water is potable, and the demand for safe drinking water is growing with rising demand.”

Graphene, a single layer of carbon atoms located in a two-dimensional honeycomb lattice, is a promising nanomaterial due to its unique structure and electrical properties.
“Graphene with intrinsic conductivity is a zero- gap semiconductor that has extremely high electron mobility (100 times higher than that of silicon), which makes it an indispensable material for accurate high-speed chemical and biological sensors because of its high sensitivity to electronic perturbations” says the scientist.

The principle of the sensor is placing nanocrystals based on graphene which are semiconductors in the interelectrode distance. The electrical conductivity of graphene material changes with the binding of substances called analytes to its surface and their chemical constituents are identified and measured.

The magnitude of the change in conductivity can be correlated with the concentration of the analyte, and this technology also includes the functionalization of the surface of the graphene material by means of special probes that can be oriented to a specific analyte.

The sensor is based on a field effect transistor (FET) with a reduced content of graphene oxide (rGO) as its measuring channel. The principle of the sensor is that the conductivity of rGO (usually measured in resistance)changes with the binding of chemicals such as heavy metals to probes fixed to the rGO surface.

“Thus, the presence of chemicals can be determined by measuring the change in the resistance of the sensor,” says Junhong Chen.

The use of such sensors in real time to monitor pollution in water distribution systems will provide early warning of chemical and biological pollution, increased water safety and public health benefits.

The technology of the presented platform can be used to detect various analytes for food and beverages, as well as for biomedical applications. Junhong Chen launched a start-up called NanoAffix Science LLC to commercialize its water quality monitoring technology. With funding from the National Science Foundation and in cooperation with several companies, they have already developed a prototype of a hand-held device for the rapid and inexpensive detection of lead ions in drinking water in real time.

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