Ion transfer dynamics of poly(3,4-ethylenedioxythiophene) films in deep eutectic solvents

An electrochemical sensor based on Ce-MOF-derived Ce-doped poly(3,4-ethylenedioxythiophene) composite for efficient determination of rutin in food

As a common antioxidant and nutritional fortifier in food chemistry, rutin has positive therapeutic effects against novel coronaviruses. Here, Ce-doped poly(3,4-ethylenedioxythiophene) (Ce-PEDOT) nanocomposites derived through cerium-based metal-organic framework (Ce-MOF) as a sacrificial template have been synthesized and successfully applied to electrochemical sensors. Due to the outstanding electrical conductivity of PEDOT and the high catalytic activity of Ce, the nanocomposites were used for the detection of rutin. The Ce-PEDOT/GCE sensor detects rutin over a linear range of 0.02-9 μM with the limit of detection of 14.7 nM (S/N = 3). Satisfactory results were obtained in the determination of rutin in natural food samples (buckwheat tea and orange). Moreover, the redox mechanism and electrochemical reaction sites of rutin were investigated by the CV curves of scan rate and density functional theory. This work is the first to demonstrate the combined PEDOT and Ce-MOF-derived materials as an electrochemical sensor to detect rutin, thus opening a new window for the application of the material in detection.

Effect of Graphene Oxide and Temperature on Electrochemical Polymerization of Pyrrole and Its Stability Performance in a Novel Eutectic Solvent (Choline Chloride-Phenol) for Supercapacitor Applications

Polypyrrole (Ppy)-modified graphene oxide (GO) electrodes were synthesized for the first time in a choline chloride-phenol-based deep eutectic solvent at various temperatures via electrochemical methods without the addition of any inorganic or organic catalysts. The surface morphologies and structures of the modified films were assessed via scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction techniques. The electrochemical properties and stability of the modified electrodes were investigated via cyclic voltammetry and impedance spectroscopy at various temperatures and scan rates. The results showed that the specific capacitance of the nanocomposites decreased with increasing scan rate during cycling. Additionally, the specific capacitances of the pure Ppy and Ppy/GO films increased with increasing temperature of the electrolyte (monomer-free), attributed to the reduction in viscosity at elevated temperature. The specific capacitances at 5 mV s^-1 were found to be 1071.78 and 594.79 F g^-1 for Ppy/GO (20 wt %) at 50 and 25 °C, respectively. It was also observed that the resistance in the cell decreased with increasing electrolyte temperature. Ppy/GO at 50 mV s^-1 was found to have the highest capacitance retention of 85% after 2000 cycles, showing better cycling stability than the pure Ppy film. Herein, the incorporation of GO in the Ppy matrix led to improved specific capacitance and cyclic stability, suggesting that Ppy/GO could represent a promising electrode material for supercapacitor applications.

In situ polymerization of PEDOT:PSS films based on EMI-TFSI and the analysis of electrochromic performance

In this report, PEDOT composite films were prepared by in situ electrochemical polymerization. 1-Ethyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide (EMI-TFSI) was used as an ionic liquid dopant for PEDOT:PSS films. Subsequently, these PEDOT:PSS/EMI-TFSI films were compared with PEDOT:PSS films based on their morphology, structure, electrochromic properties, and optical properties at different deposition voltages and deposition times. It was observed that the addition of EMI-TFSI enhanced all the aforementioned properties of the films. PEDOT:PSS/EMI-TFSI films were seen to have a larger ion diffusion coefficient (1.38 × 10−20 cm2·s−1), a wider color change range (43.48%), a shorter response time (coloring response time = 1.2 s; fade response time = 2 s), and a higher coloring efficiency (189.86 cm2·C−1) when compared with normal PEDOT:PSS films. The introduction of EMI-TFSI in the films ultimately resulted in superior electrochemical and optical properties along with higher stability.

Fundamental aspects of electrochemically controlled wetting of nanoscale composite materials

Electroactive films based on conducting polymers have numerous potential applications, but practical devices frequently require a combination of properties not met by a single component. This has prompted an extension to composite materials, notably those in which particulates are immobilised within a polymer film. Irrespective of the polymer and the intended application, film wetting is important: by various means, it facilitates transport processes - of electronic charge, charge-balancing counter ions ("dopant") and analyte/reactant molecules - and motion of polymer segments. While film solvent content and transfer have been widely studied for pristine polymer films exposed to molecular solvents, extension to non-conventional solvents (such as ionic liquids) or to composite films has been given much less attention. Here we consider such cases based on polyaniline films. We explore two factors, the nature of the electrolyte (solvent and film-permeating ions) and the effect of introducing particulate species into the film. In the first instance, we compare film behaviours when exposed to a conventional protic solvent (water) with an aprotic ionic liquid (Ethaline) and the intermediate case of a protic ionic liquid (Oxaline). Secondly, we explore the effect of inclusion of physically diverse particulates: multi-walled carbon nanotubes, graphite or molybdenum dioxide. We use electrochemistry to control and monitor the film redox state and change therein, and acoustic wave measurements to diagnose rheologically vs. gravimetrically determined response. The outcomes provide insights of relevance to future practical applications, including charge/discharge rates and cycle life for energy storage devices, "salt" transfer in water purification technologies, and the extent of film "memory" of previous environments when sequentially exposed to different media.