A carbon nanotube based resettable sensor for measuring free chlorine in drinking water

Free chlorine from dissolved chlorine gas is widely used as a disinfectant for drinking water. The residual chlorine concentration has to be continuously monitored and accurately controlled in a certain range around 0.5–2 mg/l to ensure drinking water safety and quality. However, simple, reliable, a...

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Bibliographic Details
Published in:Applied physics letters 2015-02, Vol.106 (6)
Main Authors: Hsu, Leo H. H., Hoque, Enamul, Kruse, Peter, Ravi Selvaganapathy, P.
Format: Article
Language:English
Subjects:
ABUNDANCE
ANILINE
Applied physics
CARBON NANOTUBES
CHLORINE
CONCENTRATION RATIO
DOPED MATERIALS
DRINKING WATER
ELECTRIC CONDUCTIVITY
ELECTROCHEMISTRY
Electrode polarization
Low resistance
MONITORING
NANOSCIENCE AND NANOTECHNOLOGY
OXIDATION
Oxidation resistance
REAGENTS
SENSORS
Single wall carbon nanotubes
Switches
Water quality
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Summary:Free chlorine from dissolved chlorine gas is widely used as a disinfectant for drinking water. The residual chlorine concentration has to be continuously monitored and accurately controlled in a certain range around 0.5–2 mg/l to ensure drinking water safety and quality. However, simple, reliable, and reagent free monitoring devices are currently not available. Here, we present a free chlorine sensor that uses oxidation of a phenyl-capped aniline tetramer (PCAT) to dope single wall carbon nanotubes (SWCNTs) and to change their resistance. The oxidation of PCAT by chlorine switches the PCAT-SWCNT system into a low resistance (p-doped) state which can be detected by probing it with a small voltage. The change in resistance is found to be proportional to the log-scale concentration of the free chlorine in the sample. The p-doping of the PCAT-SWCNT film then can be electrochemically reversed by polarizing it cathodically. This sensor not only shows good sensing response in the whole concentration range of free chlorine in drinking water but is also able to be electrochemically reset back many times without the use of any reagents. This simple sensor is ideally suited for measuring free chlorine in drinking water continuously.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4907631