When Nanoparticles Meet Poly(Ionic Liquid)s: Chemoresistive CO₂ Sensing at Room Temperature

Abstract

1wileyonlinelibrary.com oxidizing or reducing gases while operating at room temperature (RT). [16][17][18] Since then, electron conductive polymer-based sensors have attracted rapidly growing interest. [ 19 ] Particularly, the polymers with amino groups have been reported as promising candidates for CO 2 sensing, but in practice they suffer from poisoning with carbamates and therefore failed to fi ll the gap in the CO 2 gas sensor sector. [ 20,21 ] As a consequence, sensing of inert CO 2 gas is still performed with infrared spectroscopy, owing to trade-offs between the technological and economical factors, and having limited portability. Recently, poly(ionic liquid)s (PILs), a unique type of functional polyelectrolytes composed of ionic liquid repeating units chosen from structural diversity of the cation/anion-repertoire of ionic liquid chemistry, have been synthesized. [22][23][24] Their physical properties can be easily and broadly adjusted by the choice of the anion-cation pair. For example, structurally well-designed PILs are capable of reversible CO 2 capture and are showing high interfacial activity to bind various surfaces of metals, carbons, and to ionically interact with charged species via electrostatic repulsion or complexation. [25][26][27][28] Others demonstrated the ability of resistive CO 2 sensing with carbon nanotubes (CNTs) wrapped with poly[1-(p-vinylbenzyl)-3-methyl-imidazolium tetrafl uoroborate], P[VBTMA] [BF 4 ]. [ 29 ] They show a high sensitivity to low concentrations of CO 2 in oxygen-free atmospheres, but the response saturates already at 50 ppm, which is much lower than the normal CO 2 concentration level in fresh air (250 ppm) and thus lacks of practical application. Therefore, transforming the CO 2 sorption capacity of PILs into a chemoresistive sensor operating in real conditions, i.e., 21 vol% of oxygen and 50% relative humidity (rh), in the presence of 400 ppm [ 30 ] of CO 2 at RT requires a new structural model and additionally an understanding of the intrinsic interaction between organic and inorganic building blocks and their impact on the overall properties of such composites. Among different candidates, poly [( p -vinylbenzyl nanoparticles-both of which are intrinsically insulating materials-are utilized as building blocks, taking full advantage of the electrostatic interaction at their interface to boost the overall conductivity of composites at room temperature. To rationalize this unique behavior, the charge transport mechanism is studied using impedance spectroscopy. It is found fi nd that, for the composites with La 2 O 2 CO 3 content of 60-80 wt%, the interfacial effect becomes dominant and leads to the formation of conduction channels with increased mobility of [PF 6 ] − anions. These composites show further increase of the conductivity when exposed to pulses of CO 2 between 150 and 2400 ppm at room temperature in a relative humidity of 50%. This work therefore provides a simple strategy to achieve an enhancement of the electrical properties required for the utilizat...

High-energy resolution X-ray absorption and emission spectroscopy reveals insight into unique selectivity of La-based nanoparticles for CO2

“…The rare-earth-based materials like perovskites and oxycarbonates, owing to their unique f-electron configuration of Ln (Ln = rare earth) and layered crystal structure, emerge as the most interesting for future photo-and electrochemical applications (3-8). Among rare-earth oxycarbonates (19,20), particularly lanthanum strongly responds to CO 2 and shows up to 16-fold conductivity changes, not seen before for any metal oxides (21). This is very surprising because a direct injection of an electron into CO 2 molecule requires the activation energy of nearly 2 eV (22).…”

Ionogel—Based Composite Material for CO2 Sensing Deposited on a Chemiresistive Transducer

“…Extending the works on Ionogel [4] and on composites of MOX with PILs [3], our investigations revealed interesting phenomena occurring upon combining both approaches. Namely, CO2 response which is stronger than reported in literature and also is manifested by increasing resistance, has been observed.…”

“…It was shown that a variety of gaseous analytes can be detected by ionogel-based sensors, e.g., H2S, ethylene, NO2 and CO2 [2]. A composite material of Poly Ionic Liquid (PIL) with La2O3 was shown by Willa et al [3] to be sensitive to CO2. They ascribed the detection mechanism to a pre-concentration of CO2 by PIL and subsequent detection of CO2 by the La2O2CO3 particles.…”

Infrared investigation of CO2 sorption by amine based materials for the development of a NDIR CO2 sensor

“…Current approaches for CO 2 detection are divided into two mains categories: Non-dispersive infrared technique (NDIR) [2,3] and chemical sensors using resistive [4], capacitive [5] and mass sensitive [6] transducers.…”