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All-Solid-State Potentiometric Sensors with a Multiwalled Carbon Nanotube Inner Transducing Layer for Anion Detection in Environmental Samples
Journal article   Peer reviewed

All-Solid-State Potentiometric Sensors with a Multiwalled Carbon Nanotube Inner Transducing Layer for Anion Detection in Environmental Samples

D Yuan, A H C Anthis, M Ghahraman Afshar, N Pankratova, M Cuartero, G A Crespo and Eric Bakker
Analytical Chemistry, Vol.87(17), pp.8640-8645
2015
DOI: https://doi.org/10.1021/acs.analchem.5b01941
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https://doi.org/10.1021/acs.analchem.5b01941View
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Abstract

Analytical Chemistry Chemical Engineering Other Chemical Sciences carbon carbonation electrodes ion selective electrodes ions negative ions nitrates organic solvents potentiometers (electric measuring instruments) slope stability solid-state sensors transducers yarn
While ion to electron transducing layers for the fabrication of potentiometric membrane electrodes for the detection of cations have been well established, similar progress for the sensing of anions has not yet been realized. We report for this reason on a novel approach for the development of all-solid-state anion selective electrodes using lipophilic multiwalled carbon nanotubes (f-MWCNTs) as the inner ion to electron transducing layer. This material can be solvent cast, as it conveniently dissolves in tetrahydrofuran (THF), an important advantage to develop uniform films without the need for using surfactants that might deteriorate the performance of the electrode. Solid contact sensors for carbonate, nitrate, nitrite, and dihydrogen phosphate are fabricated and characterized, and all exhibit comparable analytical characteristics to the inner liquid electrodes. For example, the carbonate sensor exhibits a Nernstian slope of 27.2±0.8 mV.dec-1, a LOD = 2.3 μM, a response time of 1 s, a linear range of four logarithmic units, and a medium-term stability of 0.04 mV.h-1 is obtained in a pH 8.6 buffered solution. Water layer test, reversibility, and selectivity for chloride, nitrate, and hydroxide are also reported. The excellent properties of f-MWCNTs as a transducer are contrasted to the deficient performance of poly(3-octyl-thiophene) (POT) for carbonate detection. This is evidenced both with a significant drift in the potentiometric measures as well as a pronounced sensitivity to light (either sunlight or artificial light). This latter aspect may compromise its potential for environmental in situ measurements (night/day cycles). The concentration of carbonate is determined in a river sample (Arve river, Geneva) and compared to a reference method (automatic titrator with potentiometric pH detection). The results suggest that nanostructured materials such as f-MWCNTs are an attractive platform as a general ion-to-electron transducer for anion-selective electrodes. © 2015 American Chemical Society.

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