Here, we investigate the interactions between five representative gaseous analytes and two poly(ionic liquids) (PILs) based on the sulfopropyl acrylate polyanion in combination with the alkylphosphonium cations, P4,4,4,4 and P4,4,4,8, and their nanocomposites with fullerenes (C60, C70) to reveal the potential of PILs as sensitive layers for gas sensors. The gaseous analytes were chosen based on their molecular size (all of them containing two carbon atoms) and variation of functional groups: alcohol (ethanol), nitrile (acetonitrile), aldehyde (acetaldehyde), halogenated alkane (bromoethane), and carboxylic acid (acetic acid). The six variations of PILs-P4,4,4,4SPA (1), P4,4,4,4SPA + C60 (1 + C60), P4,4,4,4SPA + C70 (1 + C70), and P4,4,4,8SPA (2), P4,4,4,8SPA + C60 (2 + C60), P4,4,4,8SPA + C70 (2 + C70)-were characterized by UV-vis and Raman spectroscopy, and their interactions with each gaseous analyte were studied using electrochemical impedance spectroscopy. Exposure of all PIL samples to acetaldehyde, bromoethane, and ethanol leads to a decrease in the diffusion coefficient, while exposure to acetic acid reveals an increase. Fullerene-doping significantly enhances the response to the analyte. Semiempirical quantum mechanical xTB-GFN2 calculations revealed that hydrogen bonding and proton transfer events play an important role during the detection process.

• Publication type
• Journal Article MeSH

Solid polymer electrolytes show their potential to partially replace conventional electrolytes in electrochemical devices. The solvent evaporation rate represents one of many options for modifying the electrode-electrolyte interface by affecting the structural and electrical properties of polymer electrolytes used in batteries. This paper evaluates the effect of solvent evaporation during the preparation of solid polymer electrolytes on the overall performance of an amperometric gas sensor. A mixture of the polymer host, solvent and an ionic liquid was thermally treated under different evaporation rates to prepare four polymer electrolytes. A carbon nanotube-based working electrode deposited by spray-coating the polymer electrolyte layer allowed the preparation of the electrode-electrolyte interface with different morphologies, which were then investigated using scanning electron microscopy and Raman spectroscopy. All prepared sensors were exposed to nitrogen dioxide concentration of 0-10 ppm, and the current responses and their fluctuations were analyzed. Electrochemical impedance spectroscopy was used to describe the sensor with an equivalent electric circuit. Experimental results showed that a higher solvent evaporation rate leads to lower sensor sensitivity, affects associated parameters (such as the detection/quantification limit) and increases the limit of the maximum current flowing through the sensor, while the other properties (hysteresis, repeatability, response time, recovery time) change insignificantly.

• Keywords
• gas sensor, ionic liquid, noise spectroscopy, solid polymer electrolyte,
• Publication type
• Journal Article MeSH

An electrochemical amperometric ethylene sensor with solid polymer electrolyte (SPE) and semi-planar three electrode topology involving a working, pseudoreference, and counter electrode is presented. The polymer electrolyte is based on the ionic liquid 1-butyl 3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIM][NTf2] immobilized in a poly(vinylidene fluoride) matrix. An innovative aerosol-jet printing technique was used to deposit the gold working electrode (WE) on the solid polymer electrolyte layer to make a unique electrochemical active SPE/WE interface. The analyte, gaseous ethylene, was detected by oxidation at 800 mV vs. the platinum pseudoreference electrode. The sensor parameters such as sensitivity, response/recovery time, repeatability, hysteresis, and limits of detection and quantification were determined and their relation to the morphology and microstructure of the SPE/WE interface examined. The use of additive printing techniques for sensor preparation demonstrates the potential of polymer electrolytes with respect to the mass production of printed electrochemical gas sensors.

• Keywords
• ethylene, ionic liquid, printed electrochemical sensor, solid polymer electrolyte,
• Publication type
• Journal Article MeSH

Analyte flow influences the performance of every gas sensor; thus, most of these sensors usually contain a diffusion barrier (layer, cover, inlet) that can prevent the negative impact of a sudden change of direction and/or the rate of analyte flow, as well as various unwanted impacts from the surrounding environment. However, several measurement techniques use the modulation of the flow rate to enhance sensor properties or to extract more information about the chemical processes that occur on a sensitive layer or a working electrode. The paper deals with the experimental study on how the analyte flow rate and the orientation of the electrochemical sensor towards the analyte flow direction influence sensor performance and current fluctuations. Experiments were carried out on a semi-planar, three-electrode topology that enabled a direct exposure of the working (sensing) electrode to the analyte without any artificial diffusion barrier. The sensor was tested within the flow rate range of 0.1-1 L/min and the orientation of the sensor towards the analyte flow direction was gradually set to the four angles 0°, 45°, 90° and 270° in the middle of the test chamber, while the sensor was also investigated in the standard position at the bottom of the chamber.

• Keywords
• amperometric sensor, analyte flow, current fluctuations, signal-to-noise ratio,
• Publication type
• Journal Article MeSH