Synthesis and characterization of Polyindole and its catalytic performance study as a heterogeneous catalyst

Development of High-Performance Polyindole/Silicon Carbide Nanocomposites for Optoelectrical and Sensing Applications

In this study, silicon carbide (SiC)-reinforced polyindole (PIn) nanocomposites were prepared by a simple in situ polymerization method. The successful reinforcement of the nanofiller within the host matrix was characterized using different analytical techniques. The chemical bonding of SiC in the polymer was identified by the characteristic peak around 800 cm1 using Fourier transform infrared spectroscopy (FT-IR). The increment in intensity of the absorption and enhanced crystallinity of the samples upon the addition of nanofillers were analyzed using UV-vis spectroscopy and X-ray diffraction (XRD). The prepared specimens showed reduced optical bandgap energy (3.188 eV) and Urbach energy (2.315 meV) with an improved refractive index (2.348). The effect of nanoparticles on the surface morphology of the nanocomposites was studied using scanning electron microscopy (SEM), and a uniform dispersion of fillers in the matrix was found for PInSiC7. A high-resolution transmission electron microscopy (HR-TEM) revealed the shape and average particle size of the sample. X-ray electron spectroscopy (XPS) measurements confirmed the formation of the nanocomposite by exhibiting the presence of all elements in the corresponding spectra. The thermal stability and glass transition temperature of the nanocomposites were significantly improved with the addition of SiC. The temperature-dependent AC conductivity, dielectric parameters, complex impedance, and electrical modulus were also evaluated using an impedance analyzer. The increased electrical characteristics of the PInSiC7 sample can be attributed to the uniform spread and strong synergetic interaction of SiC with PIn. The results thus showcased the potential of the samples for use in optical and energy storage applications. This study was also extended to understand the ammonia sensing properties, which make it possible to design and develop gas sensors using the PInSiC nanocomposites.

High Photoluminescence Polyindole/CuInS Quantum Dots for Pb Ions Sensor

Polyindole is considered an excellent conducting polymer with interested properties for different applications. A novel polyindole (PIn)/CuInS (CIS)/ZnS quantum dots (QDs) nanocomposite was synthesized via in situ polymerization of PIn in presence of CIS/ZnS QDs. By investigating the effect of CIS/ZnS QDs on optical properties of PIn, it was found that the optical band gaps of PIn, CIS/ZnS QDs, and PIn/CIS/ZnS QDs nanocomposite were 3.24 eV, 4.68 eV and 3.44 eV, respectively. From the luminance spectra, it was observed that emission peaks of PIn at 442 and 468 nm are independent of the excitation wavelength with the highest intensity at excitation wavelength of 380 nm. However, the luminance spectrum of PIn/CIS/ZnS QDs nanocomposite exhibited a quenching peak for CIS/ZnS QDs while the intensity of PIn peak was enhanced. High resolution of transmission electron microscope image of CIS/ZnS QDs revealed nanocrystals with a size of 3–4.5 nm and lattice space of 0.2 nm. PIn/CIS/ZnS QDs nanocomposite as the fluorescent probe was employed for sensing different concentrations of Pb2+ from 5 to 50 ppb. The reaction between PIn/CIS/ZnS QDs and Pb2+ was slightly quenched and fixed after 90 min. The emission peak was reduced gradually with increasing concentration of lead via photo-induced electron transfer or ion exchange mechanism. The value of correlation coefficient (R2) was 0.99, the sensitivity was 0.0041 ppb−1 and limit of detection value was 4.48 ppb.

Recent trends and advances in polyindole-based nanocomposites as potential antimicrobial agents: a mini review

Infections caused by multi-drug resistant microbes are a big challenge to the medical field and it necessitates the need for new biomedical agents that can act as potential candidates against these pathogens. Several polyindole based nanocomposites were found to exhibit the ability to release reactive oxygen species (ROS) and hence they show excellent antimicrobial properties. The features of polyindole can be fine-tuned to make them potential alternatives to antibiotics and antifungal medicines. This review clearly portrays the antimicrobial properties of polyindole based nanocomposites, reported so far for biomedical applications. This review will give a clear insight into the scope and possibilities for further research on the biomedical applications of polyindole based nanocomposites.

Synthesis, Characterization and Electrochemical Performance of a Redox-Responsive Polybenzopyrrole@Nickel Oxide Nanocomposite for Robust and Efficient Faraday Energy Storage

A polybenzopyrrole@nickel oxide (Pbp@NiO) nanocomposite was synthesized by an oxidative chemical one-pot method and tested as an active material for hybrid electrodes in an electrochemical supercapattery device. The as-prepared composite material exhibits a desirable 3D cross-linked nanostructured morphology and a synergistic effect between the polymer and metal oxide, which improved both physical properties and electrochemical performance. The unprocessed material was characterized by X-ray diffraction, FTIR and UV-Vis spectroscopy, scanning electron microscopy/energy disperse X-ray analysis, and thermogravimetry. The nanocomposite material was deposited without a binder on gold current collectors and investigated for electrochemical behavior and performance in a symmetrical two- and three-electrode cell setup. A high specific capacity of up to 105 C g-1 was obtained for the Pbp@NiO-based electrodes with a gravimetric energy density of 17.5 Wh kg-1, a power density of 1925 W kg-1, and excellent stability over 10,000 cycles.

Dynamic Response of Polyindole Coated Zinc Ferrite Particle Suspension under an Electric Field

ZnFe2O4 particles initially synthesized through a simple solvothermal method were coated using polyindole (PIn) to prepare an actively controllable core-shell typed hybrid material under both electric and magnetic fields. An advantage of this process is not needing to add the stabilizers or surfactants commonly used for uniform coating when synthesizing core or shell-structured particles. The synthesized ZnFe2O4/PIn particles have a lower density than conventional magnetic particles and have suitable properties as electrorheological (ER) particles. The expected spherical shape of the particles was proven using both scanning electron microscopy and transmission electron microscopy. The chemical characterization was performed using Fourier-transform infrared spectroscopy and X-ray diffraction analysis. To analyze the rheological properties, a ZnFe2O4/PIn based suspension was prepared, and dynamic rheological measurements were performed for different electric field strengths using a rotary rheometer. Both dynamic and elastic yield stresses of the ER fluid had a slope of 1.5, corresponding to the conductivity model. Excellent ER effect was confirmed through rheological analysis, and the prepared ER fluid had a reversible and immediate response to repeated electric fields.

Physical, Chemical, and Electrochemical Properties of Redox-Responsive Polybenzopyrrole as Electrode Material for Faradaic Energy Storage

Polybenzopyrrole (Pbp) is an emerging candidate for electrochemical energy conversion and storage. There is a need to develop synthesis strategies for this class of polymers that can help improve its overall properties and make it as suitable for energy storage applications as other well-studied polymers in this substance class, such as polyaniline and polypyrrole. In this study, by synthesizing Pbp in surfactant-supported acidic medium, we were able to show that the physicochemical and electrochemical properties of Pbp-based electrodes are strongly influenced by the respective polymerization conditions. Through appropriate optimization of various reaction parameters, a significant enhancement of the thermal stability (up to 549.9 °C) and the electrochemical properties could be achieved. A maximum specific capacitance of 166.0 ± 2.0 F g⁻¹ with an excellent cycle stability of 87% after 5000 cycles at a current density of 1 A g⁻¹ was achieved. In addition, a particularly high-power density of 2.75 kW kg⁻¹ was obtained for this polybenzopyrrole, having a gravimetric energy density of 17 Wh kg⁻¹. The results show that polybenzopyrroles are suitable candidates to compete with other conducting polymers as electrode materials for next-generation Faradaic supercapacitors. In addition, the results of the current study can also be easily applied to other systems and used for adaptations or new syntheses of advanced hybrid/composite Pbp-based electrode materials.

Well-defined polyindole–Au NPs nanobrush as a platform for electrochemical oxidation of ethanol

Over the recent decades, conducting polymers have received great interest in many fields including microelectronics, energy conversion devices, and biosensing due to their unique properties like electrical conductivity, stability, and simple synthesis. Modification of conducting polymers with noble metals e.g. gold enhances their properties and opens new opportunities to also apply them in other fields like electrocatalysis. Here, we focus on the synthesis of hybrid material based on polyindole (PIN) nanobrush modified with gold nanoparticles and its application towards electrooxidation of ethanol. The paper presents systematic studies from synthesis to electrochemical sensing applications. For the characterization of PIN–Au composites, scanning electron microscopy and X-ray diffraction analyses were used. The electrocatalytic performance of the proposed hybrid material towards alcohol oxidation was studied in alkaline media by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy techniques. The results show that PIN–Au hybrid can be employed as an effective and sensitive platform for the detection of alcohols, which makes it a promising material in electrocatalysis or sensors. Moreover, the proposed composite exhibits electrocatalytic activity towards ethanol oxidation, which combined with its good long-term stability opens the opportunity for its application in fuel cells.

Development of an imidazole salt catalytic system for the preparation of bis(indolyl)methanes and bis(naphthyl)methane

Imidazolium salts are shown to catalyze the rapid room temperature reaction of indoles or naphthol with aldehydes to provide bis(indolyl)methanes or bis(naphthol)methane in excellent yields and the reaction proceeds optimally in dichloromethane with no base additives. The reaction exhibits a broad substrate tolerance and occurs through nucleophilic activation of the indoles and naphthols through a cation-π interaction.

Rare earth metal oxide (RE2O3; RE = Nd, Gd, and Yb) incorporated polyindole composites: gravimetric and volumetric capacitive performance for supercapacitor applications

The modified morphology and the extra pseudocapacitive contribution from RE₂O₃ particles lead to enhanced capacitive performance of polyindole.