Fullerene-Doped Poly(ionic Liquids) as Small Molecular Gas Sen-sors – Control of Intermolecular Interactions.
Jaroslav Otta(a,b), Jakub Mikuláštík(b), Richard Šípka(b), Matthias Stein(c), Irina A. Kühne(a), Martin Vrňata(b) and Jan Vlčeka(b)*

a Department of Functional Materials, FZU - Institute of Physics - Czech Academy of Sciences, Na Slovance 1999/2, Pra-gue 8, 182 00, Czech Republic.
b Department of Physics and Measurements, University of Chemistry and Technology, Technicka 5, 16 628 Prague 6, Czech Republic.
c Molecular Simulations and Design Group, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtor-strasse 1, 39106 Magdeburg, Germany. 

ABSTRACT: Here, we investigate the interactions between five representative gaseous analytes and two poly(ionic liquid)s (PILs) based on the 
sulfopropylacrylate 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 acetal-dehyde, bromoethane and 
ethanol leads to a decrease in the diffusion coefficient, while exposure to acetic acid reveals an in-crease. Fullerene-doping significantly enhances 
the response to the analyte. Semi-empirical quantum mechanical xTB-GFN2 calculations revealed that hydrogen bonding and proton transfer events play 
an important role during the detection process.

Data: Figures (as png, jpg or tif files), tables (as csv files)

Scheme1-Synthesis of PIL samples.
Scheme2-Preaparation of PILs on substrate.

Figure1-Measured sensor response of P4,4,4,4SPA + C70 (1 + C70) to synthetic air (black square), on exposure to acetaldehyde (top) andacetic acid (bottom) (blue triangle), and to synthetic air after exposure(purple diamond) and their fits as solid lines.

Table1-Relative Changes, ΔY0, of all PIL Materials whenExposed to the Analyte (with ΔY0 (%) = [(Y0 (Synthetic Air)− Y0 (Analyte)) × 100]/Y0 (Synthetic Air); the ΔY0 Valuesare given in Relation to the Reference Y0 Value in SyntheticAirTableS1-Polymerization mixture compositions

Figure2-Interactions of P4,4,4,4-SPA upon sequential addition of MeCN solvent molecules.
Figure3-Interactions of P4,4,4,4-SPA upon sequential addition of acetic acid.

Figure4-Scheme of gas measurement chamber and wiring.

FigureS1-Preparation of gold electrodes on optical glass substrates via magnetron sputtering

Raman spectra of prepared PILs with/without C60 fullerene: FigureS2 – FigureS7
FigureS8-Raman spectrum of drop casted C60 dissolved in methylcyclohexane.
TableS2-Representative Raman bands for P4,4,4,4SPA and P4,4,4,8SPA.

UV-Vis spectra of prepared PILs with/without C60 fullerene: FigureS9 – FigureS12
FigureS13-UV-Vis spectrum of drop casted C60 dissolved in methylcyclohexane.

EIS measurement and CPE model	
FigureS14-Equivalent circuit model used for the analysis of the poly(ionic liquid) sensor response and the equation for the impedance of the CPE.
TableS3- Absolute and relative values of Y0 before and after analyte exposure, together with their difference (with 𝐘𝟎∙ 10-9  in S sα); The Relative changes, ΔY0, of all PIL materials when exposed to the analyte (with ΔY0 = Y0 (reference gas/synthetic air) – Y0 (analyte); the ΔY0 values are given in relation to the reference Y0 value in synthetic air), including the percentual change upon addition of fullerenes.

TableS4 – TableS13:
Parameters evaluated using CPE model for acetaldehyde, acetic acid, acetonitrile, bromoethane and ethanol responses of sensors based on P4,4,4,4SPA and P4,4,4,8SPA, respectively and P4,4,4,4SPA/ P4,4,4,8SPA + C60/C70 nanocomposites.
FigureS15 – FigureS44:
Measured data of P4,4,4,4SPA and P4,4,4,8 (and the respective nanocomposites with C60 and C70) sensor response to synthetic air (green), gaseous analyte (orange) and after exposure (blue).	

TableS14-Physical properties of the used analytes (dipole moment, relative polarity, permittivity)
FigureS45-Linear dependence of the Y0 value change on the relative permittivity of the analyte.
FigureS46-Linear dependence of the Y0 value change on the dipole moment of the analyte.	
FigureS47-Linear dependence of the Y0 value change on the relative polarity of the analyte.
FigureS48-Dependence of the change in P4,4,4,XSPA sensor resistance on the dipole moment of various gas analytes.	
FigureS49-Interaction of P4,4,4,4SPA upon sequential addition of explicit ethanol solvent molecules.
