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Single sensor improves detection selectivity

Photonics Spectra
Jun 2011
CINCINNATI – A sensor that combines electrochemistry, spectroscopy and selective partitioning capabilities into one device has been developed and tested for components in nuclear waste. Unusual in that it offers more than two modes of selectivity, the highly sensitive sensor from the University of Cincinnati can find and identify a compound of interest in three ways. This proves crucial for settings like nuclear waste storage tanks because their contents are a jumbled mix of chemical and radioactive waste.

The three-way selectivity comes from the use of coatings, electrochemistry and spectroscopy. The selective coating allows only certain compounds to enter the sensing region. For example, all negatively charged ions may be able to enter the sensor, while all positively charged ions are excluded. Then, a potential is applied, and an even smaller group of compounds is electrolyzed. Lastly, a specific wavelength of light is used to detect the actual compound of interest.


William Heineman, distinguished research professor of chemistry at the University of Cincinnati (UC), presented a sensor that combines three testing means into one device. The three methods are represented in the illustration. Courtesy of Andrew Higley, UC; illustration by Lisa Ventre, UC.


The end result is that compounds – even those at low concentrations – can be detected and analyzed. The findings could be important in medical monitoring and other applications that require high selectivity and sensitivity.

More than a decade ago, the US Department of Energy started seeking a sensor that could be lowered into a tank to take multiple measurements quickly, or could be left in the tank to monitor its contents over the course of months or even a year.

The sensor has been tested at the Hanford site, a mostly decommissioned nuclear production complex in Washington State, where it was used to detect one important component of the radioactive and hazardous waste stored inside the giant tanks there.

Its design and concept could be used for many environmental and medical applications, including the detection of toxic heavy metals and polycyclic aromatic hydrocarbons at superfund sites, the scientists said.

Research related to the sensor was presented in March at the American Chemical Society’s biannual meeting in Anaheim, Calif.


GLOSSARY
electrochemistry
The study of the reversible conversion of chemical energy into electrical energy. Electroplating is an electrochemical process.
sensor
1. A generic term for detector. 2. A complete optical/mechanical/electronic system that contains some form of radiation detector.
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