4-Cyanophenol herbicide sensor using multi-walled carbon nanotube embedded dual-microporous polypyrrole nanoparticles as metal-free and environmentally friendly hybrid electrode

A highly sensitive 4-cyanophenol (4-CP) sensor was fabricated using multi-walled carbon nanotube (MWCNT)-embedded dual-microporous polypyrrole nanoparticle-modified screen-printed carbon electrodes (SPCE/DMPPy/MWCNT). The well-defined dual pores of DMPPy and MWCNT (~ 0.53 and ~ 0.65 nm) acted as good analyte absorption agents (shortening the ion diffusion path) and conducting agents (reducing the internal electron-transfer resistance). This enhanced electrical conductivity resulted in the improved electro-oxidation of 4-CP. A higher sensitivity (19.0 μA μM^-1 cm^-2) and lower limit of detection (0.8 nM) were achieved with a wide detection range of 0.001-400 µM (R² = 0.9988). The proposed sensor exhibited excellent recovery of 4-CP in real-world samples. Therefore, the SPCE/DMPPy/MWCNT sensor is regarded highly suitable for rapidly detecting 4-CP.

Graphene Nanoplatelet/Multiwalled Carbon Nanotube/Polypyrrole Hybrid Fillers in Polyurethane Nanohybrids with 3D Conductive Networks for EMI Shielding

This work reports the preparation of graphene nanoplatelet (GNP)/multiwalled carbon nanotube (MWCNT)/polypyrrole (PPy) hybrid fillers via in situ chemical oxidative polymerization with the addition of a cationic surfactant, hexadecyltrimethylammonium bromide. These hybrid fillers were incorporated into polyurethane (PU) to prepare GNP/MWCNT/PPy/PU nanohybrids. The electrical conductivity of the nanohybrids was synergistically enhanced by the high conductivity of the hybrid fillers. Furthermore, the electromagnetic interference (EMI) shielding effectiveness (SE) was greatly increased by interfacial polarization between the GNPs, MWCNTs, PPy, and PU. The optimal formulation for the preparation of GNP/MWCNT/PPy three-dimensional (3D) nanostructures was determined by optimization experiments. Using this formulation, we successfully prepared GNP/PPy nanolayers (two-dimensional) that are extensively covered by MWCNT/PPy nanowires (one-dimensional), which interconnect to form GNP/MWCNT/PPy 3D nanostructures. When incorporated into a PU matrix to form a nanohybrid, these 3D nanostructures form a continuous network of conductive GNP-PPy-CNT-PPy-GNP paths. The EMI SE of the nanohybrid is 35-40 dB at 30-1800 MHz, which is sufficient to shield over 99.9% of electromagnetic waves. Therefore, this EMI shielding material has excellent prospects for commercial use. In summary, a nanohybrid with excellent EMI SE performance was prepared using a facile and scalable method and was shown to have great commercial potential.

Nano-Sheet-like Morphology of Nitrogen-Doped Graphene-Oxide-Grafted Manganese Oxide and Polypyrrole Composite for Chemical Warfare Agent Simulant Detection

Chemical warfare agents (CWAs) have inflicted monumental damage to human lives from World War I to modern warfare in the form of armed conflict, terrorist attacks, and civil wars. Is it possible to detect the CWAs early and prevent the loss of human lives? To answer this research question, we synthesized hybrid composite materials to sense CWAs using hydrothermal and thermal reduction processes. The synthesized hybrid composite materials were evaluated with quartz crystal microbalance (QCM) and surface acoustic wave (SAW) sensors as detectors. The main findings from this study are: (1) For a low dimethyl methyl phosphonate (DMMP) concentration of 25 ppm, manganese dioxide nitrogen-doped graphene oxide (NGO@MnO₂) and NGO@MnO₂/Polypyrrole (PPy) showed the sensitivities of 7 and 51 Hz for the QCM sensor and 146 and 98 Hz for the SAW sensor. (2) NGO@MnO₂ and NGO@MnO₂/PPy showed sensitivities of more than 50-fold in the QCM sensor and 100-fold in the SAW sensor between DMMP and potential interferences. (3) NGO@MnO₂ and NGO@MnO₂/PPy showed coefficients of determination (R²) of 0.992 and 0.975 for the QCM sensor and 0.979 and 0.989 for the SAW sensor. (4) NGO@MnO₂ and NGO@MnO₂/PPy showed repeatability of 7.00 ± 0.55 and 47.29 ± 2.69 Hz in the QCM sensor and 656.37 ± 73.96 and 665.83 ± 77.50 Hz in the SAW sensor. Based on these unique findings, we propose NGO@MnO₂ and NGO@MnO₂/PPy as potential candidate materials that could be used to detect CWAs.

Polypyrrole functionalized Cobalt oxide Graphene (COPYGO) nanocomposite for the efficient removal of dyes and heavy metal pollutants from aqueous effluents

A cobalt oxide graphene nanocomposite functionalized with polypyrrole (COPYGO) having a heterogenous porous structure was synthesized using hydrothermal method. Microscopic imaging of the COPYGO surface revealed its highly porous and ordered features. The adsorption performance of the COPYGO composite was systemically investigated for Methylene Blue (MB), Congo red (CR) dyes and toxic lead (Pb(II)) and Cadmium (Cd(II)) metals. These were selected as they are the common pollutants in industrial wastewater. The COPYGO was found to be thermally stable up to 195 ^oC with a specific surface area of 133 m² g^-1. Experimental data indicates that the COPYGO follows Langmuir and Temkin adsorption isotherm. The COPYGO was efficient in removing MB (92.8%), CR (92.2%), Pb(II) (93.08%) and Cd(II) (95.28%) pollutants at pH 7.2, 5.0, 5.5 and 6.1 respectively from the simulated effluents. The maximum adsorption capacity (Q_max) observed for MB 663.018 mg g^-1, CR 659.056 mg g^-1, Pb(II) 780.363 mg g^-1 and Cd(II) 794.188 mg g^-1 pollutants. The thermodynamic analysis of the COPYGO indicates that the adsorption is endothermic and spontaneous in nature. COPYGO showed very high efficient removal rate for the pollutants in simulated effluents which guaranteed its benefits and efficacy in industrial wastewater treatment.

Polypyrrole-Based Metal Nanocomposite Electrode Materials for High-Performance Supercapacitors

Metallic nanostructures (MNs) and metal-organic frameworks (MOFs) play a pivotal role by articulating their significance in high-performance supercapacitors along with conducting polymers (CPs). The interaction and synergistic pseudocapacitive effect of MNs with CPs have contributed to enhance the specific capacitance and cyclic stability. Among various conjugated heterocyclic CPs, polypyrrole (PPy) (prevalently knows as “synthetic metal”) is exclusively studied because of its excellent physicochemical properties, ease of preparation, flexibility in surface modifications, and unique molecular structure–property relationships. Numerous researchers attempted to improve the low electronic conductivity of MNs and MOFs, by incorporating conducting PPy and/or used decoration strategy. This was succeeded by fine-tuning this objective, which managed to get outstanding supercapacitive performances. This brief technical note epitomizes various PPy-based metallic hybrid materials with different nano-architectures, emphasizing its technical implications in fabricating high-performance electrode material for supercapacitor applications.

Hexagonal nanostructured cobalt oxide @ nitrogen doped multiwalled carbon nanotubes/polypyyrole composite for supercapacitor and electrochemical glucose sensor

Hexagonal nanostructured cobalt oxide @ N-doped MWCNT /polypyyrole (Co₃O₄/PPy@N-MWCNT) composite was produced by an ultrasonication-mediated solvothermal method for electrochemical supercapacitor and glucose sensor applications. The structural and electrochemical properties of the Co₃O₄/PPy@N-MWCNT were confirmed by various spectroscopic and microscopic techniques. The as-prepared electrode showed an excellent capacitance of ∼872 F/g at 0.5 A/g with a capacitance retention of 96.8 %, even after 10,000 cycles. In addition, analysis of the sensing activity of the composite materials towards the glucose detection showed excellent electrochemical sensing performance that includes the glucose linear limit of (10 to 0.15) μm, detection sensitivity of 195.72 μA/cm²/mM, and lower detection value of S = 0.07327 μA/cm² @ R² = 0.99. The as-prepared composite material can be a promising candidate for the electrochemical supercapacitor and the efficient sensing of glucose.

Ultrasonication-mediated nitrogen-doped multiwalled carbon nanotubes involving carboxy methylcellulose composite for solid-state supercapacitor applications

In this study, a novel nanohybrid composite containing nitrogen-doped multiwalled carbon nanotubes/carboxymethylcellulose (N-MWCNT/CMC) was synthesized for supercapacitor applications. The synthesized composite materials were subjected to an ultrasonication-mediated solvothermal hydrothermal reaction. The synthesized nanohybrid composite electrode material was characterized using analytical methods to confirm its structure and morphology. The electrochemical properties of the composite electrode were investigated using cyclic voltammetry (CV), galvanic charge-discharge, and electrochemical impedance spectroscopy (EIS) using a 3 M KOH electrolyte. The fabricated composite material exhibited unique electrochemical properties by delivering a maximum specific capacitance of approximately 274 F g^-1 at a current density of 2 A g^-1. The composite electrode displayed high cycling stability of 96% after 4000 cycles at 2 A g^-1, indicating that it is favorable for supercapacitor applications.

Biogenic synthesis of a green tea stabilized PPy/SWCNT/CdS nanocomposite and its substantial applications, photocatalytic degradation and rheological behavior

A green tea leaf-derived cadmium sulfide quantum dot-based system containing different weight percentages of single-walled carbon nanotubes (SWCNTs) and polypyrrole, named PSC, was designed via a green method. The photocatalytic degradation of Ponceau BS dye (λ _max 505 nm) in the presence of PSC was measured. PSC with the highest weight percentage of SWCNTs (7-PSC) showed maximum photocatalytic activity, with 94.6% dye degradation in 55 minutes of irradiation time. This significant enhancement was due to the synergism in the intrinsic properties of the parent components. Alongside this, the rheological behavior of the prepared nanomaterial PSC was examined at constant (100 s^-1) and varying shear rate from 0 to 500 s^-1 at a fixed temperature of 25 °C for a specified volume percentage of 0.1% using Castrol class: 15W-40 engine oil as a base fluid. The objective of lowering the viscosity of engine oil by 98.9% (initial: 0.221000 Pa s, final: 0.0022 Pa s.) was achieved by chartering/mixing the prepared PSC nanomaterial into the engine oil. A comparative study of the experimental and simulation outputs implied the high precision of the modeling via a neural network with minute 0.373 average % errors.

Porous materials of nitrogen doped graphene oxide@SnO2 electrode for capable supercapacitor application

The porous materials of SnO₂@NGO composite was synthesized by thermal reduction process at 550 °C in presence ammonia and urea as catalyst. In this process, the higher electrostatic attraction between the SnO₂@NGO nanoparticles were anchored via thermal reduction reaction. These synthesized SnO₂@ NGO composites were confirmed by Raman, XRD, XPS, HR-TEM, and EDX results. The SnO₂ nanoparticles were anchored in the NGO composite in the controlled nanometer scale proved by FE-TEM and BET analysis. The SnO₂@NGO composite was used to study the electrochemical properties of CV, GCD, and EIS analysis for supercapacitor application. The electrochemical properties of SnO₂@NGO exhibited the specific capacitance (~378 F/g at a current density of 4 A/g) and increasing the cycle stability up to 5000 cycles. Therefore, the electrochemical results of SnO₂@NGO composite could be promising for high-performance supercapacitor applications.

The construction of a sandwich structured Co3O4@C@PPy electrode for improving pseudocapacitive storage

Sandwich structured hybrids consisting of a Co₃O₄ nanowire as the core, amorphous carbon (C) as the inner shell and a polypyrrole (PPy) outer layer as the exodermis are synthesized via a hydrothermal method and constant current electropolymerization. The formation mechanism and growth stage of PPy on carbon surfaces is investigated and it was discovered that PPy layer thickness, corresponding to nucleation time of the polymer, as the dynamic factor, can influence the pseudocapacitive properties of the obtained composites. The carbon layer acts as both a network to increase the electric conductivity and a buffer agent to reduce volume expansion of Co₃O₄ during ion insertion/extraction to achieve higher capacitance and better cyclic stability. So for a capacitor, the Co₃O₄@C@PPy electrode delivers a higher areal capacitance of 2.71 F cm⁻² at 10 mA cm⁻² (1663 F g⁻¹ at 6.1 A g⁻¹) and improved rate capability compared to Co₃O₄ and Co₃O₄@C. An asymmetric device is assembled by the Co₃O₄@C@PPy hybrids as a cathode and a relatively high energy density of 63.64 W h kg⁻¹ at a power density of 0.54 kW kg⁻¹ is obtained, demonstrating that the sandwich structured Co₃O₄@C@PPy hybrids have enormous potential for high-performance pseudocapacitors.

The fabrication of sandwich structural CO₃O₄@C@PPy electrode for improving rate capability and areal capacitance.