Ionic liquids on optical sensors for gaseous carbon dioxide
This work presents a study on the influence of eight different ionic liquids (ILs) in the composition of dry membranes used for gaseous CO2 optical sensing. The presence of CO2 causes a displacement of a colorimetric pH indicator toward its acid form that increases the emission intensity of the luminophore by an inner filter process. The influence of ILs in the membrane on the stability and dynamic behavior—usually the main drawbacks of these sensors—of the membranes is studied. The characterization of the different membranes prepared was carried out and the discussion of the results is presented. In all cases, the response and recovery times improved considerably, with the best case being response times of only 10 s and recovery times of 48 s, compared to response and recovery times of 41 and 100 s, respectively, for membranes without IL. The useful life of the detection membranes is also considerably longer than that of membranes that do not include IL, at least 292 days in the best case. The sensing membrane without luminophore and only containing the pH indicator is proposed for the color-based measurement of CO2 using a digital camera for possible use in food-packaging technology.
KeywordsIonic liquids Carbon dioxide Phosphorescent sensor Color measurements Intelligent packaging
This study was supported by projects from the Spanish MINECO (CTQ2013-44545-R and CTQ2016-78754-C2-1-R)
The project was partially supported by European Regional Development Funds (ERDF) as well as by the Unidad de Excelencia de Química aplicada a biomedicina y medioambiente of the University of Granada.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no competing interests.
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