An electrochemical gas sensor based on paper supported room temperature ionic liquids

Abstract

A sensitive and fast-responding membrane-free amperometric gas sensor is described, consisting of a small filter paper foil soaked with a room temperature ionic liquid (RTIL), upon which three electrodes are screen printed with carbon ink, using a suitable mask. It takes advantage of the high electrical conductivity and negligible vapour pressure of RTILs as well as their easy immobilization into a porous and inexpensive supporting material such as paper. Moreover, thanks to a careful control of the preparation procedure, a very close contact between the RTIL and electrode material can be achieved so as to allow gaseous analytes to undergo charge transfer just as soon as they reach the threephase sites where the electrode material, paper supported RTIL and gas phase meet. Thus, the adverse effect on recorded currents of slow steps such as analyte diffusion and dissolution in a solvent is avoided. To evaluate the performance of this device, it was used as a wall-jet amperometric detector for flow injection analysis of 1-butanethiol vapours, adopted as the model gaseous analyte, present in headspace samples in equilibrium with aqueous solutions at controlled concentrations. With this purpose, the RTIL soaked paper electrochemical detector (RTIL-PED) was assembled by using 1butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide as the wicking RTIL and printing the working electrode with carbon ink doped with cobalt(II) phthalocyanine, to profit from its ability to electrocatalyze thiol oxidation. The results obtained were quite satisfactory (detection limit: 0.5 mM; dynamic range: 2-200 mM, both referring to solution concentrations; correlation coefficient: 0.998; repeatability: AE7% RSD; long-term stability: 9%), thus suggesting the possible use of this device for manifold applications.

Room Temperature Ionic Liquids As Useful Overlayers for Estimating Food Quality from Their Odor Analysis by Quartz Crystal Microbalance Measurements

“…Thus, sensors designed to generate current responses and exploiting both gas permeable membranes 12,13 and membrane-free devices were developed, these last based on either solid polymer electrolytes (SPEs) [14][15][16] or room temperature ionic liquids (RTILs). [17][18][19][20][21][22][23] Unfortunately, these sensors provides responses for specific classes of VOCs alone, while flavors come out almost always from the contribution of different volatile species.…”

“…Just these profitable properties have promoted their increasing use for several applications, such as organic synthesis, 34 chemical analysis, 35 GC separations 36 microextractions 37 and electrochemical gas sensing. [17][18][19][20][21][22][23][38][39][40] Moreover, they have been adopted as soft-coatings for QCM gas sensors planned for the detection of some organic volatile species at either room or high temperature. 29,41 In this paper we propose an array of QCM sensors filmed with different RTIL overlayers for the analysis of flavors with complex composition.…”

“…To achieve retention of volatile compounds, overlayers consisting of GC stationary phases displaying adsorption properties, 30 supramolecular compounds, 31 organic polymers, 32 biomolecules 33 or room temperature ionic liquids (RTILs) [17][18][19][20][21][22][23]28,29 have been employed. Among these, RTILs appear to be particularly attractive for their good thermal and electrical conductivity, negligible vapor pressure and ability to dissolve several compounds, thanks to their amphiphilic character which can be tuned by tailoring suitably their cations and anions.…”

Multiple headspace extraction for gas detection in ionic liquids

“…depends on the choice of suitable combinations of cations and anions. Electrochemical IL based gas sensing methodologies [19][20][21][22][23][24][25][26][27][28][29] also profit of a preferably large uptake of the gas in question by the IL-electrolyte. Hence, several papers were published within the last decade, presenting different methods for the evaluation of gas solubilities in numerous ILs.…”

An Electrochemical Ammonia Sensor on Paper Substrate

“…Therefore, PADs have been employed for a variety of applications as discussed in recent articles. 10,11 Among the electrochemical PADs, amperometric gas sensors have gained interest with many desirable characteristics, including good sensitivity, selectivity and detection limit for electrochemically oxidizable or reducible toxic gases, and relatively low power requirements. 12 Room temperature ionic liquids (RTILs) have received substantial attention in recent years because of their interesting and often unique * Electrochemical Society Member.…”