Polyaniline Carbon Nanotubes Research Articles

Informatics-based design of polyaniline-carbon nanotube thermoelectric nanocomposite using ANN and GA

Abstract Conducting polymer and carbon nanotube (CNT) based nanocomposites have emerged as prospective thermoelectric (TE) materials due to their potential application in flexible electronics. Non-conventional charge and heat transport in these nanocomposites, presents the possibility to enhance the TE conversion efficiency, given by ZT. However, the highly non-linear and complex association of structure and composition with the overall TE properties have hindered the development of any general strategy to develop high ZT nanocomposites. Here, we implement artificial neural network (ANN) and genetic algorithm (GA) to develop data driven models followed by optimization to design high efficiency nanocomposites based on CNT dispersed in polyaniline (PANI) matrix. Our models suggest that CNT concentration plays the most crucial role in determining ZT. Non-dominated Pareto optimal solutions consisting of different combinations of design variables are obtained by multi-objective optimization. Although a range of optimal solutions span over different regions of the search space, in general we note that longer CNTs boost Seebeck coefficient (S) and electrical conductivity (σ), and smaller length lowers thermal conductivity (k), while higher diameter of CNTs increase S and lowers σ and k. The results provide a general guideline for developing CNT-PANI nanocomposites with enhanced TE figure of merit.

A novel enzymeless electrochemical sensor based on Ni(OH)2–NiO(OH) nanoelectrocatalyst for sensitive and selective detection of uric acid in PBS simulated body fluid

Neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, and Huntington's disease are increasing worldwide. Therefore, the development of a low-cost, highly stable, and portable device for rapid and accurate risk assessment of relevant biomarkers, especially uric acid (UA), by electrochemical detection is currently attracting much attention. Herein, an electrochemical enzymeless UA sensor based on highly active Ni(OH)2–NiO(OH) nanoelectrocatalyst decorated on polyaniline–carbon nanotubes (PANI-CNTs) nanocomposite film, which was modified on a commercial screen-printed carbon electrode (SPCE) by electrodeposition method for sensitive and selective detection of UA. The sensing behavior of the modified electrode (named Ni(OH)2–NiO(OH)/PANI-CNTs/SPCE) is examined in a simulated body fluid (phosphate buffer solution-PBS, 0.01 M, pH 7.4) using differential pulse voltammetry (DPV) technique. The obtained results showed that the Ni(OH)2–NiO(OH)/PANI-CNTs/SPCE electrode exhibited outstanding electrocatalytic performance for the detection of UA at low potential (0.33 V vs. Ag/AgCl) without exhibiting interfering signals of dopamine (DA), glucose (Glu), ascorbic acid (AA) and urea. The sensor exhibited extra high sensitivity (386.8 μA mM−1 cm−2), high selectivity, good reproducibility, and durable stability with the ability to detect UA at both low (5–100 μM) and high (100–800 μM) levels with a very low detection limit down to 0.11 μM (individual detection of UA) and 0.29 μM (detection of UA in presence of DA) in a simulated body fluid. The recovery test using the proposed electrochemical sensor showed a high recovery percentage (>99.81 %), making it a viable option for practical applications.

Superflexible porous PCSnf-Fe3O4/CNT-PANI BP/PCSnf-Fe3O4 sandwich composite films with excellent electromagnetic wave absorption performance based on integral assembly by electrospinning

Polycarbosilane nanofiber-ferroferric oxide (PCSnf-Fe3O4) films were assembled on both sides of carbon nanotube-polyaniline buckypaper (CNT-PANI BP) by electrospinning to obtain PCSnf-Fe3O4/CNT-PANI BP/PCSnf-Fe3O4 sandwich porous composites, with a diameter of 110–120 mm and a thickness of 150–200 µm. The Fe3O4 nanoparticles adhered on the PCS nanofibers formed a bamboo-like or plum-like structure. The PANI nanoparticles were uniformly embedded in the CNT network. Both PCSnf-Fe3O4 film skin layers were well bonded to the CNT-PANI BP core layer, with two main forms of the interlayer interface of rattan-like and root-like entanglement. The sandwich composite film (SCF) with 15.1 wt% Fe3O4 in the skin layers had a density of 0.97 g/cm3, a porosity of 61% and a total pore area of 30.1 m2/g, with a multimodal pore size distribution. The SCFs were superflexible, being tightly wound around a 4 mm diameter glass rod and repeated 100 times without damage. The absorption performance of the SCF was significantly improved by introducing Fe3O4 nanoparticles into its skin layers. The SCF with 11.8 wt% Fe3O4 in its skin layers achieved optimal dielectric and magnetic loss matching, with minimum reflection loss of − 43.54 dB and maximum effective absorption bandwidth of 6.97 GHz.

Mechanical and electrochemical properties of carbon nanotubule-polyaniline nanowire/polyaniline nanoparticle high-strength ultra-flexible aerogel buckypaper

The carbon nanotube-polyaniline nanowire/polyaniline nanoparticle (CNT-PANInw/PANInp) aerogel buckypaper (BP) was constructed, where PANI nanoparticles were uniformly embedded into the CNT network, and a series of downhanging PANI nanowires were grown in situ on the CNT monofilaments. The aerogel BP with 80 µm thickness had a PANI load of 3.5 mg/cm2 and a porosity of 69%. The cross-junctions between CNT monofilaments were anchored by polyvinyl alcohol gel. It had a tensile strength of 25 MPa, with a strain of 11.4%, being folded along sharp creases or violently rubbed without damage. The specific capacitance of the aerogel BP electrode decreased from 3.070 to 2.064 F/cm2, as the current density increased from 2 to 8 mA/cm2, with a capacitance retention of 67.2%. Its specific capacitance was 1.720 and 1.560 F/cm2 after 2000 folding in halfunfolding and 200 zigzag foldingunfolding cycles, respectively, with the capacitance retention of 84.0% and 76.2%, at 8 mA/cm2. Its specific capacitance was 1.832 and 1.224 F/cm2 after 2000 and 10,000 charge-discharge cycles, respectively, with the capacitance retention of 88.8% and 59.3%, at 8 mA/cm2. Its residual specific capacitance after 10,000 cycles was higher than most of the reported initial value of the materials with similar compositions.

Hanging Photothermal Fabric Based on Polyaniline/Carbon Nanotubes for Efficient Solar Water Evaporation.

Solar-driven water evaporation is essential to provide sustainable and ecofriendly sources of fresh water. However, there are still great challenges in preparing materials with broadband light absorption for high photothermal efficiency as well as in designing devices with large evaporation areas and small heat dissipation areas to boost the water evaporation rate. We designed a hanging-mode solar evaporator based on the polyaniline/carbon nanotube (PANI/CNT) fabric, in which the photothermal fabric acts as the solar evaporator and the micropores on the cotton fabric act as the water transfer channels. The hanging mode provides efficient evaporation at both interfaces by greatly reducing the heat dissipation area. The hanging mode PANI/CNT fabric solar evaporator can achieve an evaporation rate of 2.81 kg·m-2·h-1 and a photothermal efficiency of 91.74% under a solar illumination of 1 kW·m-2. This high-performance evaporator is designed by regulating the photothermal material and evaporation device, which provides a novel strategy for sustainable desalination.

Machine learning based models to investigate the thermoelectric performance of carbon nanotube-polyaniline nanocomposites

Thermoelectric materials have been widely recognized as a simple approach for harnessing green energy by converting thermal gradients into electrical energy. However, the intricate and conflicting interplay between electrical conductivity (σ), Seebeck coefficient (S), and thermal conductivity (k) in known materials present a challenge for improving their thermoelectric conversion efficiency. To overcome this challenge, various data-driven machine-learning techniques such as correlation matrix (CM), multiple linear regression (MLR), polynomial regression (PR), principal component analysis (PCA), and artificial neural network (ANN) have been utilized to identify the impact of different structural and compositional factors on the thermoelectric performance in carbon nanotube (CNT)-polyaniline (PANI) based nanocomposites. Our findings suggest that the thermoelectric figure of merit, (ZT=S2σκT) of these nanocomposites can be positively influenced by proper choice of doping agent of PANI and by using SWCNT, since these two parameters influence the thermoelectric outputs in the desired manner. The other input variables have conflicting impacts on the thermoelectric performance, although optimal solutions for maximized performance can be extracted. The investigation provides valuable insights about designing a PANI-CNT nanocomposite system with superior thermoelectric performance.

Functionalized carbon nanotube-polyaniline composite coating for on-line microextraction on a screw coupled with high performance liquid chromatography to determine opium alkaloids.

Anovel and efficient on-line microextraction on a screw coupled with high-performance liquid chromatography with an ultraviolet-visible detector was developed to extract and determine trace quantities of five opium alkaloids. All detections of the analytes were achieved at 210 nm. The surface of the screw grooves was electrochemically coated with the carbon nanotubes-COOH/polyaniline composite. The surface characterization was assessed by Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The prepared screw was inserted into a cartridge of a guard column, and then the constructed microextraction on a screw device was placed in the loop of a six-port HPLC injection valve. The parameters affecting the extraction efficiency of the analytes were optimized using the one variable-at-a-time method. The effective parameters for the extraction efficiency of the analytes, including sample volume, extraction time, sampling flow rate, desorption solvent type, ionic strength, and pH were investigated and optimized. Under optimal conditions, the detection limits were 3-10 μg L-1, and the linear dynamic ranges were 10-2000 μg L-1 with a coefficient of determination greater than 0.9940. The inter-day and intra-day (n = 3) relative standard deviations were less than 7% and 5%, respectively. The proposed method was simple and reproducible, with an acceptable relative recovery (90-108%) for determining opium alkaloids in water and urine samples.

Carbon Nanotube-Polyaniline Reinforced Flexible and Stretchable Strain Sensor with Enhanced Sensitivity for Smart Wearable and Skin-Mounted Applications

Flexible and stretchable strain sensors have emerged as promising components for integration into smart wearable devices and skin-mounted applications. These sensors enable accurate detection of physiological signals, thereby finding unique applications in diverse fields such as human health monitoring, soft robotics, human-machine interface, prosthetics, virtual reality, and professional sports. Two commonly utilized types of strain sensors are capacitive and resistive strain gauges, owing to their low production cost, simplified circuitry, and ease of construction. While resistive strain gauges exhibit high sensitivity, they are prone to nonlinearity and hysteresis. On the other hand, capacitive strain gauges demonstrate linear behavior with minimal hysteresis but offer lower sensitivity. In this study, we capitalize on the exceptional properties of carbon nanotubes, including high mechanical strength, electrical conductivity, and thermal stability, along with using polyaniline as an exemplary conductive polymer. These materials are employed as a reinforcing phase within the polymer matrix, while the dielectric layer is comprised of Ecoflex® 00-30. An interdigitated pattern is specifically designed for this strain gauge to enhance sensitivity. Through this research, we aim to develop a flexible and stretchable strain sensor with enhanced sensitivity and improved performance characteristics.

Polyaniline/carbon hybrids: Synthesis and application for alizarin red S removal from water

Polyaniline (PANI) nanofibers, Polyaniline/graphene oxide (PANI/GO) and polyaniline/carbon nanotube (PANI/CNTs) hybrids have been successfully prepared as highly effective adsorbent materials to remove alizarin red S (AR) dye from water. Herein, PANI nanofibers, PANI/GO composites, and PANI/CNTs composites were synthesized by chemical oxidation, directly blending, and in-situ polymerization methods, respectively. Compared with the mono-component PANI and carbon materials (GO, CNTs), the obtained PANI/carbon hybrid materials exhibited superior adsorption ability towards AR due to the synergistic effect. Effects of adsorption condition (i.e. adsorbents dosage, temperature, solution pH, adsorption time and the initial AR concentration) on the adsorption ability of the adsorbents were systematically studied. The sorption kinetics and isotherms of the hybrids for AR adsorption were studied with different models. Moreover, the adsorption ability of the PANI/carbon material hybrids towards other dye molecules, as well as their desorption and regeneration were also explored.

Preparation and performance of PANI/CNTs composite coating on 316 stainless steel bipolar plates by pulsed electrodeposition

Compact polyaniline (PANI) coating and polyaniline/carbon nanotubes (PANI/CNTs) composite coating are prepared on the surface of 316 stainless steel bipolar plate for proton exchange membrane fuel cells by a new method of pulse electrodeposition. The micro morphology shows that the PANI coating prepared by pulse electrodeposition is more uniform and compact than that by direct current electrodeposition. The compactness, corrosion resistance and electrical conductivity of PANI coating are further increased after CNTs are compounded. The results show that compared with PANI coating, the corrosion potential of PANI/CNTs coating is increased by about 78 mV, and the corrosion current density is reduced by an order of magnitude. Under the working potential of 0.6 V (vs. SCE), the current density of PANI/CNTs coating is reduced to about 1.9 μA·cm−2. After potentiostatic test for 5 h, there was no obvious corrosion on the surface of the coating. The interfacial contact resistance (ICR) contact resistance of PANI/CNTs coating is reduced by 35 % compared with PANI coating, and after the polarization process, PANI/CNTs coating has lower contact resistance than PANI coatings. The improved corrosion resistance and electrical conductivity of PANI/CNTs coating can be better applied in the protection of bipolar plates.

Electrooxidation of Methanol on Pt, Ru, and Metal Oxides Nanoparticles Modified with Polyaniline-Carbon Nanotube Hybrid Electrodes

Electrooxidation of Methanol on Pt, Ru, and Metal Oxides Nanoparticles Modified with Polyaniline-Carbon Nanotube Hybrid Electrodes

Advancement of Polyaniline/Carbon Nanotubes Based Thermoelectric Composites.

Organic thermoelectric (TE) materials have been widely investigated due to their good stability, easy synthesis, and high electrical conductivity. Among them, polyaniline/carbon nanotubes (PANI/CNTs) composites have attracted significant attention for pursuing enhanced TE properties to meet the demands of commercial applications. In this review, we summarize recent advances in versatile PANI/CNTs composites in terms of the dispersion methods of CNTs (such as the addition of surfactants, mechanical grinding, and CNT functional group modification methods), fabrication engineering (physical blending and in-situ polymerization), post-treatments (solvent treatments to regulate the doping level and microstructure of PANI), and multi-components composites (incorporation of other components to enhance energy filtering effect and Seebeck coefficient), respectively. Various approaches are comprehensively discussed to illustrate the microstructure modulation and conduction mechanism within PANI/CNTs composites. Furthermore, we briefly give an outlook on the challenges of the PANI/CNTs composites for achieving high performance and hope to pave a way for future development of high-performance PANI/CNTs composites for sustainable energy utilization.

Highly conducting PANI- fMWNT composites with exceptional crystallinity and enhanced thermal stability for potential applications

Here we report, the synthesis and characterization of the thin film of polyaniline-functionalized multiwalled carbon nanotube composite with exceptional electrical conductivity, excellent crystallinity and improved thermal stability. In this study, the multiwalled carbon nanotubes were functionalized using formaldehyde through an electrophilic substitution reaction and methylol groups (-CH2OH) attached to the sidewalls of the nanotubes. A significant dispersivity of polyaniline-multiwalled carbon nanotube composites was achieved as a result of the functionalization. The thin film of polyaniline-functionalized multiwalled carbon nanotube composite was prepared via the doping-dedoping-redoping process. The structural, morphological, thermal and conductivity studies of the synthesized polyaniline-functionalized multiwalled carbon nanotube composite samples were carried out using various characterization tools. The thin film sample shows an enhanced electrical conductivity of 1991 S/cm, which is pretty high among the reported values for polyaniline-carbon nanotube composites. It also exhibits an excellent crystallinity of 84.44%, the highest value ever reported. The thermal stability of the thin film sample is very high compared to the polyaniline sample. The charge transfer mechanism in the synthesized samples was investigated using the three-dimensional variable range hopping model. The ANOVA and regression analysis was performed to assess the validity of the model.

Selective reduction of nitrite to nitrogen by polyaniline-carbon nanotubes composite at neutral pH

The selective reduction of nitrite (NO2−) to nitrogen by chemical reductant is a desirable strategy to remove NO2− from polluted water and wastewater. However, the residue and reuse of chemical reductant are two main issues to be addressed. Herein, a novel polyaniline-carbon nanotubes composite (PANI-CNTs) was developed by in-situ polymerization to selectively reduce NO2− to nitrogen gas (N2). The used PANI-CNTs could be reused after regeneration with NaBH4. The PANI-CNTs could reduce NO2− with 93.9% N2 selectivity at initial pH of 6.8. The NO2− removal efficiency only decreased by 12.08% after five cycles of reduction/regeneration. The interconversion between imine nitrogen (–N) and amine nitrogen (–NH–) groups induced the chemical reduction of NO2− and regeneration of PANI-CNTs. PANI-CNTs exhibited an excellent performance for the removal of NO2− in the presence of competitive ions and in actual water and wastewater samples. This new PANI-CNTs composite may have great potential for water purification and wastewater denitrification.

Study of Structural, Thermal and Electrical Properties of Functionalized Multiwalled Carbon Nanotubes–Polyaniline Composites

Study of Structural, Thermal and Electrical Properties of Functionalized Multiwalled Carbon Nanotubes–Polyaniline Composites

(Digital Presentation) Electrical Properties of Nanocarbon-Polyaniline Nanocomposites

Macroscopic objects such as fibers and films formed from a combination of nanocarbon materials and polymers have promising electrical [1], thermal [2], thermoelectric [3], and mechanical [4] properties. In particular, composites of nanocarbon and conductive polymers revealed that they can constitute key parts of batteries [1] and thermoelectric generators [3]. In literature, it is possible to find many synthesis methods of this type of material. One of the most common approaches is electrochemical, wherein monomers are polymerized onto the nanocarbon surface due to its highly conducting nature [5]. Polyaniline (PANI) is the oldest and still one of the most popular conductive polymers used in this area. That is because PANI is relatively simple to manufacture at low cost and effort. Moreover, it has good mechanical strength and tunable electrical conductivity, which depend on the kind of PANI. This polymer has three forms: pernigraniline – fully oxidized (purpure/red), emeraldine – partially oxidized (blue/violet), and leucoemeraldine – fully reduced (black) [6]. Emeraldine achieves the highest conductivity when doped with Brøstead acids such as HCl, H2SO4, HBF4 [7].The goal of this study was to exploit the phenomenon of the hydrophilic surface of carbon nanostructure caused by thermal annealing, described by us previously [8], to electropolymerize aniline onto free-standing films from nanocarbon. The films were manufactured by the wet method [8] using single-walled nanotubes (SWCNTs) exclusively and SWCNTs/graphene nanoplatelet composite. Electropolymerization was used to synthesize PANI on the surface of these materials. To establish the parameters of synthesis of different forms of PANI, voltage ranges between [(-1.6 V) – (1.6 V)] were investigated. The films were tested as a counter and a working electrode in this process. After the synthesis, the composites were investigated by optical and Scanning Electron Microscopy, Raman spectroscopy, Atomic Force Microscopy. Moreover, water contact angles, electrical conductivity values, and Seebeck coefficients were determined. Composites containing all three PANI forms have been synthesized and thoroughly analyzed to elucidate the structure-property relations. Consequently, correlations between the forms of PANI and the characteristics of nanocomposites were established. Depending on the amount and type of PANI on the surface, the character of the nanocarbon films was affected considerably. For example, coating of the material with emeraldine salts enhanced the electrical conductivity of the films by about 60% [9], while simultaneously making the material much stronger.[1] L. Xiao, Y.H. Sehlleier, S. Dobrowolny, F. Mahlendorf, A. Heinzel, C. Schulz, H. Wiggers, Novel Si-CNT/polyaniline nanocomposites as Lithium-ion battery anodes for improved cycling performance, Mater. Today Proc. 4 (2017) S263–S268. doi:10.1016/J.MATPR.2017.09.197.[2] Z. Duan, Y. Luo, Z. Luo, W. Yu, C. Liu, S. Fan, The influence of charging and discharging on the thermal properties of a carbon nanotube/polyaniline nanocomposite electrode, RSC Adv. 9 (2019) 7629–7634. doi:10.1039/C9RA00151D.[3] R. Wu, H. Yuan, C. Liu, J. Le Lan, X. Yang, Y.H. Lin, Flexible PANI/SWCNT thermoelectric films with ultrahigh electrical conductivity, RSC Adv. 8 (2018) 26011–26019. doi:10.1039/c8ra04863k.[4] M.R. Saeb, P. Zarrintaj, Polyaniline/graphene-based nanocomposites, Fundam. Emerg. Appl. Polyaniline. (2019) 165–175. doi:10.1016/B978-0-12-817915-4.00010-5.[5] C. Oueiny, S. Berlioz, F.X. Perrin, Carbon nanotube–polyaniline composites, Prog. Polym. Sci. 39 (2014) 707–748. doi:10.1016/J.PROGPOLYMSCI.2013.08.009.[6] S.C. Rasmussen, The Early History of Polyaniline: Discovery and Origins, An Int. J. Hist. Chem. Subst. 1 (2017) 99–109. doi:10.13128/substantia-30.[7] Q. Qin, Y. Guo, Preparation and characterization of nano-polyaniline film on ITO conductive glass by electrochemical polymerization, J. Nanomater. 2012 (2012). doi:10.1155/2012/519674.[8] D. Janas, G. Stando, Unexpectedly strong hydrophilic character of free-standing thin films from carbon nanotubes, Sci. Rep. 7 (2017) 12274. doi:10.1038/s41598-017-12443-y.[9] G.Stando, P. Stando, P. Chulkin, M. Salhman, M. Lundström, D. Janas, Electropolymerization of aniline onto hydrophilic nanocarbon films (in preparation)G.S. and P.S. would like to thank the Ministry of Science and Higher Education of Poland for financial support of research (under Diamond Grant, grant agreement 0036/DIA/201948). G.S. also would like to thank European Union for thanks for financing the costs of the conference (European Social Fund, grant nr POWR.03.05.00-00-Z305) and National Agency for Academic Exchange of Poland (under the Iwanowska program, grant agreement PPN/IWA/2019/1/00017/UO/00001) for financial support during the stay at the University of Pittsburgh in the USA. G.S. and H.L. acknowledge NSF (CBET-2028826) for partial support of this work. P. S. acknowledges the National Agency for Academic Exchange of Poland (under the Academic International Partnerships program, grant agreement PPI/APM/2018/1/00004) for supporting training in the Aalto University. G.S, P.S and D.J. would like to thank the National Centre for Research and Development, Poland (under the Leader program, grant agreement LIDER/0001/L-8/16/NCBR/2017).

Microstructural effect of various polyaniline-carbon nanotube core-shell nanocomposites on electrochemical supercapacitor electrode performance

Various carbon nanotubes-polyaniline (CNT-PANI) core-shell nanocomposites such as multiwalled carbon nanotube-PANI (PAM), carboxylic acid functionalized MWCNT (cMWCNT)-PANI (PACM) and amine-functionalized MWCNT (nMWCNT)-PANI (PANM) core-shell composites are successfully prepared by in-situ chemical oxidation process using ammonium persulphate (APS). Fourier transform infrared spectrum (FTIR) analysis proves the bonding nature between CNT core and PANI shell in nanocomposites. High-resolution transmission electron microscopy (HRTEM) and Field emission scanning electron microscopy (FESEM) images confirm the nanometer-sized PANI layer over CNT or core-shell structure of CNT-PANI nanocomposites. Further, the specific capacitance of the PAM electrode is 647 Fg−1 at scan rate 1 mV s−1 and 491 Fg−1 at current density 1 Ag−1 through cyclic voltammetry (CV) and galvanostatic charge-discharge respectively (GCD) in H2SO4 (1 M) medium under an applied potential between −0.2 to +0.8 V. Among the other CNT-PANI core-sell electrodes, the PAM electrode exhibits the highest retention of specific capacitance of 98 % and maximum Coulombic efficiency of 100 % after 5000th cycles of galvanostatic charge-discharge in the same applied potential. Due to its high specific capacitance and exceptional capacitance retention, PAM composite was fabricated as symmetric supercapacitors. The highest specific capacitance of 483 Fg−1 at a scan rate of 1 mV s−1 and 268 Fg−1 at a current density of 1 Ag−1 in 6 M H2SO4 is found for PAM composite. The symmetric device delivered the maximum energy density of 37 Wh kg−1 at a power density of 166 W kg−1.

Self-healable and redox active hydrogel obtained via incorporation of ferric ion for supercapacitor applications

Poly (vinyl alcohol)/phytic acid (PVA/PA) hydrogels have been identified as self-healable electrolytes. In this work, a novel redox active and self-healable PVA/PA/Fe3+ (PPFe) hydrogel containing dual cross-linking network through the formation of both metal coordination bonds and hydrogen bonds was fabricated via a freezing-thawing method. For the first time to our best knowledge, it was found that the introduction of dynamic Fe3+ coordination bonds into the PPFe hydrogel not only improved its mechanical properties and self-healing ability via re-configuration of various bonds, but also afforded the hydrogel high electrochemical redox activity. Compared with plain PVA/PA hydrogels, the as-fabricated PPFe gel delivered greatly improved mechanical properties, including a tensile stress of 0.618 MPa and tensile strain of 924 %, as well as a strain self-healing efficiency of 72 %. The self-healable and redox active PPFe hydrogel was further utilized to fabricate supercapacitors, where the redox reaction of Fe3+ occurred on polyaniline/carbon nanotubes (PANI/CNTs) electro-active material, resulting in an ultra-high 1526 mF/cm2 at 0.5 mA/cm2, and a remarkable energy density of 0.212 mWh/cm2 at 0.25 mW/cm2, as wells as an excellent cycling stability. Moreover, it could recover its electrochemical performance after the cutting-healing, which would greatly improve the reliability and safety of the energy storage device.

Epitaxial nanofiber separator enabling folding-resistant coaxial fiber-supercapacitor module

Mechanically strengthened fiber-supercapacitors (FSCs) are urgently needed in wearable electronics to adapt frequent severe deformations. However, current bendable FSCs using gel electrolyte as separator are easily short-circuited under harsh folding due to the limited stretchability of gel polymer. Herein, a folding-resistant coaxial FSC, for the first time, was fabricated through in-situ electrospinning polyacrylonitrile (PAN) nanofibers as separator on fiber electrode, thus effectively avoiding the short-circuit risk under highly localized stretching, compressing and folding. Moreover, such “epitaxial growth” ultrathin (∼ 1 µm) PAN separator possesses high porosity, favorable strength and seamless contact with fiber electrode, enabling fast ion transport and decreased internal resistance of FSCs. Coupled with robust polyaniline/carbon nanotube (PANI/CNT) composite as model electrodes, our fabricated coaxial symmetric FSC exhibits outstanding structural folding-resistance without electrochemical failure. Amazingly, such in-situ encapsulated separator technique makes it easier to assemble multi-layer PANI/CNT electrode in series or parallel. As-assembled coaxial integrated series or parallel device keeps almost same volume as single device, but delivers higher output voltage or capacitance; and simultaneously remains excellent foldable property, showing great practical potential.

Development of an Efficient Voltammetric Sensor for the Monitoring of 4-Aminophenol Based on Flexible Laser Induced Graphene Electrodes Modified with MWCNT-PANI.

Sensitive electrodes are of a great importance for the realization of highly performant electrochemical sensors for field application. In the present work, a laser-induced carbon (LIC) electrode is proposed for 4-Aminophenol (4-AP) electrochemical sensors. The electrode is patterned on a commercial low-cost polyimide (Kapton) sheet and functionalized with a multi-walled carbon nanotubes polyaniline (MWCNT-PANI) composite, realized by an in-situ-polymerization in an acidic medium. The LIC electrode modified with MWCNT-PAPNI nanocomposite was investigated by SEM, AFM, and electrochemically in the presence of ferri-ferrocyanide [Fe(CN)6]3−/4− by cyclic voltammetry and impedance spectroscopy. The results show a significant improvement of the electron transfer rate after the electrode functionalization in the presence of the redox mediators [Fe(CN)6]3−/4−, related directly to the active surface, which itself increased by about 18.13% compared with the bare LIG. The novel electrode shows a good reproducibility and a stability for 20 cycles and more. It has a significantly enhanced electro-catalytic activity towards electrooxidation reaction of 4-AP inferring positive synergistic effects between carbon nanotubes and polyaniline PANI. The presented electrode combination LIC/MWCNT-PANI exhibits a detection limit of 0.006 μM for the determination of 4-AP at concentrations ranging from 0.1 μM to 55 μM and was successfully applied for the monitoring in real samples with good recoveries.