Electropolymerization of Pyrrole-Tailed Imidazolium Ionic Liquid for the Elaboration of Antibacterial Surfaces

Abstract

A strategy was developed to prepare antibacterial surfaces by electropolymerization of a pyrrole-functionalized imidazolium ionic liquid bearing an halometallate anion. The objective was to combine the antibacterial efficiency of polypyrrole (PPy) with those of the ionic liquid's components (cation and anion). For this, N-(1-methyl-3-octylimidazolium)pyrrole bromide monomer [PyC 8 MIm]Br was synthesized and coordinated to ZnCl 2 affording [PyC 8 MIm]Br-ZnCl 2 . The antibacterial properties of [PyC 8 MIm]Br-ZnCl 2 monomer were evaluated against Escherichia coli and Staphylococcus aureus by measurement of the minimum inhibitory concentration (MIC) values. This monomer presents higher activity against S. aureus (MIC = 0.098 μmol• mL −1 ) than against E. coli (MIC = 2.10 μmol•mL −1 ). Mixtures of pyrrole and the pyrrole-functionalized ionic liquid [PyC 8 MIm]Br-ZnCl 2 were then used for the electrodeposition of PPy films on Fluorine-doped tin oxide (FTO) substrates. The concentration of pyrrole was fixed to 50 mM, while the concentration of [PyC 8 MIm]Br-ZnCl 2 was varied from 5 to 100 mM. The efficient incorporation of the imidazolium cation and zinc halometallate anion into the films was confirmed by X-ray photoelectron spectroscopy (XPS) measurements. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements confirmed the homogeneity of the different films with structures that depend on the [PyC 8 MIm]Br-ZnCl 2 concentration. The films' thickness determined by profilometry varies only slightly with the [PyC 8 MIm]Br-ZnCl 2 concentration from 7.4 μm at 5 mM to 8.9 μM at 100 mM. The films become more hydrophilic with an increase of [PyC 8 MIm]Br-ZnCl 2 concentration with water contact angles varying from 47°at the lowest concentration to 32°at the highest concentration. The antibacterial activities of the different PPy films were determined both by the halo inhibition method and by the colony forming units (CFUs) counting method over time against Gram-positive S. aureus and Gram-negative E. coli bacteria. Films obtained by incorporation of [PyC 8 MIm]Br-ZnCl 2 showed excellent antibacterial properties, at least two times higher than those of neat PPy, validating our strategy. Furthermore, a comparison of the antibacterial properties of the films obtained using the same [PyC 8 MIm]Br-ZnCl 2 concentration (50 mM) evidenced much better activity against Gram-positive (no bacterial survival within 5 min) than against Gram-negative bacteria (no bacterial survival within 3 h). Finally, the antibacterial performances over time could be tuned by the concentration of the employed pyrrolefunctionalized ionic liquid monomer. Against E. coli, using 100 mM of [PyC 8 MIm]Br-ZnCl 2 , the bacteria were totally killed within a few minutes, using 50 mM, they were killed after 2 h while using 10 mM, about 20% of bacteria survived even after 6 h.

Conductometric Sensor Based on Electropolymerized Pyrrole-Tailed Ionic Liquids for Acetone Detection

“…The synthesis route for the pyrrole-functionalized imidazolium monomers is featured in Scheme . The three monomers [PyC 8 MIm]­BF 4 , [PyC 8 MIm]­PF 6 , and [PyC 8 MIm]­TFSI were obtained by anion metatheses of [PyC 8 MIm]­Br , with sodium tetrafluoroborate, potassium hexafluorophosphate, and lithium bis­(trifluoromethylsulfonyl)­imide (see experimental details in the Supporting Information). The structure and the purity of the synthesized monomers were confirmed by 1 H, 13 C, 19 F, and 31 P NMR analyses, attenuated total reflection-infrared (ATR-IR) spectroscopy, and mass spectrometry (Figures S2–S14).…”