Issue 17, 2015

Towards improving the robustness of electrochemical gas sensors: impact of PMMA addition on the sensing of oxygen in an ionic liquid

Abstract

The electrochemical reduction of oxygen (O2) has been studied on commercially-available integrated Pt thin-film electrodes (TFEs). Chemically reversible (but electrochemically quasi-reversible) cyclic voltammetry was observed in the room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][NTf2]), showing superior behaviour of TFEs compared to screen-printed electrodes for oxygen sensing. As a step towards the preparation of robust gas sensors, the RTIL was mechanically stabilised on the TFE surface by the addition of poly(methyl methacrylate) (PMMA). At a PMMA concentration in the RTIL of ca. 50% mass, electrolyte flow was not evident. O2 reduction peak currents were found to decrease systematically with increasing PMMA content, reflecting the higher viscosity of the electrolyte medium. Linear calibration graphs were obtained for 0–100% vol. oxygen at all PMMA–RTIL mixtures studied. The sensitivities decreased as [PMMA] increased, but the limits of detection were relatively unchanged. Mechanical stability of the sensors was tested in different orientations (flat, upside down, sideways) with both the neat RTIL and 50% mass electrolyte. Whilst the electrochemical responses were dramatically changed for the neat RTIL, the responses in the PMMA–RTIL mixture were independent of electrode orientation. Additionally, the oxygen response in the PMMA–RTIL mixture was less affected by atmospheric impurities and moisture, compared to the neat RTIL. This suggests that these low-cost miniaturised devices can successfully be used for oxygen sensing applications in field situations, especially where portability is essential.

Graphical abstract: Towards improving the robustness of electrochemical gas sensors: impact of PMMA addition on the sensing of oxygen in an ionic liquid

Supplementary files

Article information

Article type
Paper
Submitted
25 2 2015
Accepted
18 5 2015
First published
18 5 2015
This article is Open Access
Creative Commons BY license

Anal. Methods, 2015,7, 7327-7335

Author version available

Towards improving the robustness of electrochemical gas sensors: impact of PMMA addition on the sensing of oxygen in an ionic liquid

J. Lee, G. Du Plessis, D. W. M. Arrigan and D. S. Silvester, Anal. Methods, 2015, 7, 7327 DOI: 10.1039/C5AY00497G

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