Electrochemically Produced Copolymers of Pyrrole and Its Derivatives: A Plentitude of Material Properties Using "Simple" Heterocyclic Co-Monomers

Single laser synthesis of gold nanoparticles-polypyrrole-chitosan on laser-induced graphene for ascorbic acid detection

The simultaneous synthesis of gold nanoparticles (AuNPs) and graphene by laser ablation was demonstrated. The in-situ synthesis was performed by laser ablation of a polymer substrate covered with a gold precursor dispersion. The gold precursor was prepared in a copolymer solution of pyrrole (Py) and chitosan (Chi) to improve the nucleation of gold embedded on the laser-induced graphene electrode (LIGE). The morphology of AuNPs-pPy-Chi/LIGE was studied by scanning electron microscopy and characterized electrochemically by cyclic voltammetry. A comprehensive investigation of the electrochemical and physical features of the AuNPs-pPy-Chi/LIGE was carried out. The parameters of differential pulse voltammetry were adjusted to enhance the response to ascorbic acid (AA). The AuNPs-pPy-Chi/LIGE produced two linear ranges: from 0.25 to 5.00 and 5.00-25.00 mmol L-1. The limit of detection was 0.22 mmol L-1. Hundreds of electrodes were tested to demonstrate the excellent reproducibility of the AuNPs-pPy-Chi/LIGE fabrication. Overall, the proposed electrode allows the successful detection of AA in orange juice products with acceptable accuracy (recoveries = 97 ± 2 to 109.1 ± 0.7). The preparation strategy of the proposed AuNPs-pPy-Chi/LIGE could be adapted to detect other compounds or biomarkers.

Investigation of spectroscopic and electrical properties of doped poly(pyrrole-3-carboxylic acid)

The spectroscopic and electrical properties of poly(pyrrole-3-carboxylic acid) doped with p-TSA- (p-toluenesulfonate) and AQS- (anthraquinone sulfonate) were investigated. The variation in electrical conductivity as a function of temperature shows that the systems have semiconductor-like electrical characteristics. The investigated polymers exhibit 3D conductivity and less than 0.6 eV energy gaps. The IR and Raman spectra show that the charge carriers are polarons and bipolarons. Doping the poly(pyrrole-3-carboxylic acid) increases the number of charge carriers. Electron paramagnetic resonance has shown that localized polarons and bipolarons are formed within these polymers.

Effect of hydrostatic pressure on charge carriers in a conducting pyrrole-co-poly(pyrrole-3-carboxylic) copolymer

The charge carriers in conducting pyrrole-co-poly(pyrrole-3-carboxylic) were examined using high-pressure Raman spectroscopy. The molecular structure of the new copolymer was investigated using high-resolution 13C ssNMR, 1H-13C 2D NMR correlation spectroscopy, and density functional theory (DFT) calculations. Bands in Raman spectra that showed the presence of polarons and bipolarons were studied. It was observed that the quantity of polarons and bipolarons correlated with the hydrostatic pressure. At a pressure of 4 GPa, an anomaly in the correlation between pressure and the position of the Raman band was identified.

3-Trifluoromethyl Pyrrole Synthesis Based on β-CF3-1,3-Enynamides

A new metal-free method for the rapid, productive, and scalable preparation of 3-trifluoromethyl pyrroles has been developed. It is based on the electrophilic nature of the double bond of β-CF3-1,3-enynamides due to the electron-withdrawing characteristics of the trifluoromethyl groups and the strong nucleophilic nature of alkyl primary amines. Evidence for the highly regioselective 1,4-hydroamination was observed after the isolation and characterization of the allenamide intermediate.

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

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 [PyC₈MIm]Br was synthesized and coordinated to ZnCl₂ affording [PyC₈MIm]Br-ZnCl₂. The antibacterial properties of [PyC₈MIm]Br-ZnCl₂ 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 [PyC₈MIm]Br-ZnCl₂ 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 [PyC₈MIm]Br-ZnCl₂ 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 [PyC₈MIm]Br-ZnCl₂ concentration. The films' thickness determined by profilometry varies only slightly with the [PyC₈MIm]Br-ZnCl₂ concentration from 7.4 μm at 5 mM to 8.9 μM at 100 mM. The films become more hydrophilic with an increase of [PyC₈MIm]Br-ZnCl₂ 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 [PyC₈MIm]Br-ZnCl₂ 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 [PyC₈MIm]Br-ZnCl₂ 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 pyrrole-functionalized ionic liquid monomer. Against E. coli, using 100 mM of [PyC₈MIm]Br-ZnCl₂, 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.

The Role of Electrochemical and Spectroelectrochemical Techniques in the Preparation and Characterization of Conjugated Polymers: From Polyaniline to Modern Organic Semiconductors

This review article presents different electrochemical and spectroelectrochemical techniques used to investigate conjugated polymers. The development of this research area is presented from an over 40-year perspective-the period of research carried out by Professor Mieczyslaw Lapkowski. Initial research involved polymers derived from simple aromatic compounds, such as polyaniline. Since then, scientific advances in the field of conductive polymers have led to the development of so-called organic electronics. Electrochemical and spectroelectrochemical methods have a great influence in the development of organic semiconductors. Their potential for explaining many phenomena is discussed and the most relevant examples are provided.