Sulfonated Carbon Nanotubes Research Articles

One-Pot Electrodeposition of a PANI:PSS/MWCNT Nanocomposite on Carbon Paper for Scalable Determination of Ascorbic Acid

In recent years, there has been growing demand for the monitoring of ascorbic acid levels, especially in underdeveloped populations where ascorbic acid deficiency affects up to 74% of individuals. To facilitate widespread ascorbic acid screening, we have developed a highly scalable conductive polymer nanocomposite with excellent ascorbic acid sensing performance. The material is based on polyaniline, which is deposited in a single step in the presence of polystyrene sulfonate and multi-walled carbon nanotubes onto carbon paper. The modified electrodes take advantage of the electrocatalytic properties of polyaniline toward ascorbic acid, which are boosted by the proton donating polystyrene sulfonate polymer and the high surface area of the multi-walled carbon nanotubes. The morphology and composition of the composite are characterized using field-emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy and the electrochemical characteristics are examined using cyclic voltammetry and electrochemical impedance spectroscopy. The modified electrode shows good ascorbic acid sensing characteristics, with a linear range of 1–400 μM, a sensitivity of 546 μA mM−1 cm−2, and a limit of detection of 0.11 μM. High performance and low cost results in a promising platform to support the widespread, cheap monitoring of ascorbic acid deficiency.

Promoting Effect of Ball Milling on the Functionalization and Catalytic Performance of Carbon Nanotubes in Glycerol Etherification.

A facile and eco-friendly approach using in situ-generated 4-benzenediazonium sulfonate (BDS) was applied to prepare highly functionalized carbon nanotubes (CNTs). The effectiveness of this functionalization was additionally enhanced by a green and short-time ball milling process applied beforehand. The obtained BDS-modified CNTs presented significant activity in glycerol etherification, producing tert-butyl glycerol ethers, which are considered promising fuel additives. Excellent results of ~56% glycerol conversion and ~10% yield of higher-substituted tert-butyl glycerol ethers were obtained within just 1 h of reaction at 120 °C using a low catalyst loading of only 2.5 wt.%. Furthermore, the sulfonated CNTs were reusable over several reaction cycles, with only a minor decrease in activity. Additionally, the sample activity could be restored by a simple regeneration approach. Finally, a clear correlation was found between the content of -SO3H groups on the surface of CNTs and the catalytic performances of these materials in glycerol etherification. Improved interaction between functionalized ball-milled CNTs and the reactants was also suggested to positively affect the activity of these catalysts in the tested process.

Flexible and ultrasensitive piezoresistive electronic skin based on chitin/sulfonated carbon nanotube films

Wearable electronic skin has gained increasing popularity due to its remarkable properties of high flexibility, sensitivity, and lightweight, making it an ideal choice for detecting human physiological activity. In this study, we successfully prepared e-skin using regenerated chitin (RCH) and sulfonated carbon nanotubes (SCNTs). The e-skin demonstrated brilliant mechanical and sensing properties, exhibiting a sensitivity of 1.75 kPa−1 within the 0–5 kPa range and a fast response-recovery time of <10 ms. Furthermore, it displayed an ultra-low detection limit of 1.39 Pa (5 mg), exceptional stability (up to 11,000 cycles), and a remarkable mechanical strength, reaching up to 50 MPa. Moreover, the e-skin was fabricated through a simple and economical approach. With the popularity of micro sensing devices, the e-skin holds tremendous potential for various applications, including wearable electronic devices, health and sports monitoring, artificial intelligence and other fields.

One-step preparation of flexible nanocellulose-based composite hydrogel supercapacitors with high specific capacitance

Supercapacitors (SCs) have ultra-high specific capacitance far exceeding traditional capacitors, and have become an important direction in the field of capacitor research. However, SCs devices based on carbon materials usually require a high temperature environment for N-doping or compounding of pseudocapacitive materials, which greatly increases the manufacturing cost and the difficulty of industrialized production. Herein, we fabricated cellulose-based flexible hydrogel supercapacitors by Fe3+ facilitated one-step ternary composite of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCN)/sulfonated carbon nanotubes (SCNT)/polyaniline (PANI). The combination of these three substances could form a porous and flexible three-dimensional conductive hydrogel just at room temperature. By comparing the performance of supercapacitors prepared with different ratios of three substances, it was found that the best supercapacitors exhibited a high area specific capacitance of 1786 mF/cm2 at a current density of 1 mA/cm2 and excellent flexibility. Therefore, these composite hydrogels are promising for high-performance flexible solid-state supercapacitors.

Fabrication and Characterization of a Novel Smart-Polymer Actuator with Nanodispersed CNT/Pd Composite Interfacial Electrodes.

As emerging smart polymers, ionic polymer-metal composites (IPMCs) are playing more and more important roles as promising candidates for next-generation actuators in terms of academic interest and industrial applications. It is reported that the actuation behaviors of IPMCs are dependent on the electrochemical kinetic process between metal/polymer interfaces to a great extent. Thus, the fabrication of tailored metal/polymer interface electrodes with large surface areas and superior interface characteristics is highly desirable in improving the actuation performance of IPMCs, which is still technologically critical for IPMCs. In this contribution, we developed a novel fabrication technology for carbon/metal composite electrodes with a superior interface structure and characteristics to optimize the actuation behaviors of IPMCs by exploiting the synergistic effect of combining a sulfonated multi-walled carbon nanotube (SCNT)/Nafion hybrid layer with nanodispersed Pd particles. The improved IPMCs showed significantly enhanced capacitance characteristics and highly facilitated charge–discharge processes. Moreover, their actuation behaviors were greatly improved as expected, including approximately 2.5 times larger displacement, 3 times faster deformation speed, 4 times greater output force, and 10 times higher volume work density compared to those of the IPMCs with traditional electrode structures. The advantages of the developed SCNT/Pd-IPMCs will greatly facilitate their applicability for artificial muscles.

Frost-resistant and ultrasensitive strain sensor based on a tannic acid-nanocellulose/sulfonated carbon nanotube-reinforced polyvinyl alcohol hydrogel

The operating temperature of hydrogels, especially at low temperatures, is crucial due to their wide applicability in soft robots, sensors, and electronic skin. Hydrogels are often used at room temperature, but their performance may deteriorate at low temperatures. Therefore, it is crucial to develop hydrogels that can be used at low temperatures to expand their range of use. Herein, we have proposed a simple one-pot method to prepare a frost-resistant (−70 °C) and conductive hydrogel consisting of a glycerol (Gly)-water binary solvent. We have added tannic acid (TA)-coated carboxymethylated cellulose nanofibrils (CMCNFs) to poly (vinyl alcohol) (PVA) as a functional filler to improve the hydrogel's mechanical properties. The introduction of sulfonated carbon nanotubes (SCNT) has provided the hydrogel with high conductivity (0.1 S/m), strain sensitivity (gauge factor of 3.76), and cyclic stability (1600 cycles). Due to the strong hydrogen bonding and physical entanglement effects between the components, the hydrogel exhibied excellent tensile properties (297 %), high toughness (0.44 MJ/m3), and a high Young's modulus (1.25 MPa). These characteristics ensure that the hydrogel is well suited for low-temperature environments, health monitoring, and wearable devices.

Au Nanoparticles Anchored on Sulfonated Carbon Nanotubes for Benzyl Alcohol Oxidation

Promotion of gold (Au)–support synergy provides considerable opportunities to enhance the thermal stability of nanoscale gold catalysts. In this work, we developed an anchorage strategy for Au on sulfonated carbon nanotubes (CNTs), inspired by the mysterious Au–S synergy. S species existed mainly as sulfonyl groups with a tiny quantity of S atoms inserted in the carbon skeleton. The geometric and electronic structures of gold particles were modified, rendering them efficient for the selective oxidation of benzyl alcohol. Using integrated experimental and theoretical approaches, we explicitly show that Au particles of around 2.6 nm were highly dispersed at a S/C ratio of 1.4 at. %. Electrons were delivered from Au to the support with a maximized Au–C interfacial perimeter and promoted adsorption ability with the reactant. However, high S/C atomic ratios (≥3.9%) resulted in increased surface acidity and self-rearrangement of particles with abundant high-coordinated Au3+ sites at the expense of conversion loss. Under appropriate sulfonation, Au/S1CNT exhibited a TOF value of 2294 h–1 at only 50 °C. This work disentangled the structure manipulation of Au catalyst with a suitable action mode between Au and S species to afford a better Au catalyst with resistance to coarsening.

The synthesis and properties of PANI/(TOCNF-SMWCNT) supercapacitor electrode materials by in situ polymerization

Aiming at the problems of the destroyed structure, the decreased capacitance retention rate and the bad cycle stability of polyaniline (PANI) during the continuous charge/discharge due to the irreversible deformation of PANI, this article proposes that the TEMPO-oxidized cellulose nanofiber (TOCNF), doping sulfonated multi-walled carbon nanotube (SMWCNT) enhances its electrical conductivity, the microstructure of the polymer is controlled via in-situ polymerization of the aniline on the surface of TOCNF-SMWCNT, the composite electrode materials PANI/(TOCNF-SMWCNT) is synthesized. The composite electrode materials were characterized by SEM, TEM, XRD, XPS, FTIR, and Raman, and the structure-activity relationship of the enhanced electrical properties was also clarified. The test results showed that the specific capacitance of PANI/(TOCNF-SMWCNT) is 546.0 F/g at a current density of 1.0 A/g. In addition, the composite electrode exhibited good cyclic stability with retention of 82.4% even after 5000 cycles when the current density is 1.0 A/g.

Nondestructive CNT chained Fe3O4 anode materials for high-performance Li-ion batteries

Designing a realistic structure for transition metal oxides (TMOs) with high specific capacity and good stability is a critical challenge for the development of lithium-ion batteries (LIBs). Herein, we report an effective strategy to fabricate sulfonated carbon nanotubes (SCNT) chained Fe3O4 nanoparticles (SCNT/Fe3O4). Compared with acidized carbon nanotubes (CCNT), the nondestructive preparation process of SCNT made it retain high electron conductivity and acquired larger length-diameter ratio. The SCNT/Fe3O4 used as anode material delivered a high reversible capacity (674 mAh g−1 at 500 mA g−1 after 100 cycles) and excellent rate capability (402 mAh g−1 at 2 A g−1 after 200 cycles). The excellent performance may be related to the faster electron transmission network and the more stable three-dimensional framework provided by SCNT. This work presents an approach to fabricate high-performance TMO-based composites for LIBs.

Enhancing Anti-Static Performance of Fibers by Construction of the Hybrid Conductive Network Structure on the Fiber Surface.

The hybrid antistatic agent SCNTs/OAA composed of sulfonated carbon nanotubes (SCNTs) and organic antistatic agent (OAA) was treated on the fiber surface to construct the hybrid conductive layer. Among them, SCNTs were synthesized through a simple method, and their chemical structure and morphology were characterized. SCNTs had good dispersibility due to the presence of sulfonic acid groups, which made SCNTs uniformly dispersed on the fiber surface. The SCNTs/OAA-treated fiber was hardly affected by relative humidity, because SCNTs form a continuous and uniform physical conductive network on the fiber surface. When the addition amount of SCNTs/OAA was 0.5~2 wt%, the fiber had excellent antistatic ability. Under the synergistic effect of SCNTs and OAA, the resistivity of SCNTs/OAA-treated fiber was almost not affected by fiber stretching.

In-situ synthesis of flexible nanocellulose/carbon nanotube/polypyrrole hydrogels for high-performance solid-state supercapacitors

Nanocellulose has become one of the most attractive matrix materials for flexible supercapacitors, owing to the high surface area, good mechanical properties and environmental friendliness. Herein, we developed electrode materials with high capacitance and mechanical flexibility through the in-situ synthesis of polypyrrole (PPy) in TEMPO-oxidized cellulose nanofibril (TOCN)/sulfonated carbon nanotubes (SCNT) composite hydrogels. The TOCN/SCNT/PPy composite hydrogels were thus obtained via a bifunctional Fe3+ in-situ oxidation, showing high specific capacitance of 5299 mF/cm2 at a current density of 1 mA/cm2. Furthermore, the assembled symmetric TOCN-40SCNT-PPy solid-state supercapacitor exhibited outstanding capacitance of 375 mF/cm2 and electrochemical stability with 163.2 % capacitance retention at a current density of 1 mA/cm2 for 2500 cycles. These nanocellulose/carbon nanotube/polypyrrole hydrogels are thus promising in the fields of flexible solid-state supercapacitor with superior electrochemical performance.

Fabrication of carbon nanotubes/polystyrene nanocomposites via Pickering emulsion polymerization

In this paper, the carbon nanotubes/polystyrene nanocomposites were fabricated via Pickering emulsion polymerization using sulfonated carbon nanotubes as solid surfactant. The functionalized carbon nanotubes could be used as effective surfactant of styrene-in-water emulsion and dispersed homogeneously in the production of polystyrene as effective nanofiller by this method. The research results show that the carbon nanotubes/polystyrene nanocomposites were prepared and the thermal stability of polystyrene was significantly improved with low functionalized carbon nanotubes loading.

Polypyrrole/sulfonated multi-walled carbon nanotubes conductive hydrogel for electrochemical sensing of living cells

Conductive hydrogels, a class of novel polymeric material that combine the electronic conductivity of intrinsically conductive materials and diverse functionalities of hydrogels, are promising candidates for a range of applications in bioelectronics. However, poor conductivity and biocompatibility of conventional conducting hydrogels compromise the reliable function of hydrogel bioelectronic devices. Herein, we report the development of a conjugated polypyrrole (PPy) hydrogel with conductive sulfonated multi-walled carbon nanotubes (s-MWCNTs) as crosslinking agent. The electrostatic interaction between -SO3- groups of s-MWCNTs and nitrogen groups of PPy facilitates the hydrogel gelation, and the conductivity of PPy/s-MWCNTs hydrogel with interconnected 3D conducting network is measured to be 30 S m−1. Furthermore, the in vitro cytocompatibility results suggest that the proposed PPy/s-MWCNTs hydrogels have excellent biocompatibility. For bioelectronics applications, the PPy/s-MWCNTs hydrogels were demonstrated to serve as highly sensitive electrochemical biosensors for in situ detection of biomolecules released from living cells and cell-substrate impedance biosensors for real-time monitoring of cell proliferation. Our strategy for assembling conjugated polymer hydrogel with conductive crosslinker would offer new insight for the construction of highly conductive hydrogels for various potential applications in bioelectronics.

Improving Biocatalytic Synthesis of Furfuryl Alcohol by Effective Conversion of D-Xylose into Furfural with Tin-Loaded Sulfonated Carbon Nanotube in Cyclopentylmethyl Ether-Water Media

Carbon nanotube (CNT) was utilized as as the precursor to synthesize solid acid (tin-loaded sulfonated carbon nanotube, SO42−/SnO2-CNT) for catalyzing D-xylose into furfural. Fourier transform infrared spectroscopy, Roman spectroscopy, X-ray diffraction analysis, and scanning electron microscope techniques were used for characterizing SO42−/SnO2-CNT. Different loading of D-xylose (20–100 g/L) were converted into furfural (81.6–299.1 mM) at 41.9–61.2% yield by SO42−/SnO2-CNT (3.5 wt%) within 15 min at 180 °C in cyclopentylmethyl ether-water (1:2, v:v) biphasic media. Subsequently, whole-cells of recombinant Escherichia coli CG-19 cells expressing reductase catalyzed D-xylose-derived furfural at 35 ℃ and pH 7.5. Within 3 h, the prepared D-xylose (81.6–299.1 mM) could be converted into furfuryl alcohol at 32.7–61.2% yield (based on the D-xylose loading). Sequential conversion of D-xylose with SO42−/SnO2-CNT and reductase catalysts was established for the effective production of furfuryl alcohol.

Synthesis of the novel binary composite of self-suspended polyaniline (S-PANI) and functionalized multi-walled carbon nanotubes for high-performance supercapacitors

To push the upper limit of capacitive materials, the integration of multi-modal capacitive materials has emerged as a potential solution. In this regard, we reported the novel binary composite of self-suspended polyaniline (S-PANI) and multi-walled carbon nanotubes (MWNTs). Compared with conventional polyaniline, S-PANI offers higher porosity and fibrillar polymeric network, which was achieved by doping long-chain protonic acid during in situ polymerization. S-PANI was loaded on oxidized carbon nanotubes (OCNTs) and sulfonated carbon nanotubes (SCNTs) to prepare S-PANI/OCNT and S-PANI/SCNT composite electrodes, respectively. The conductive and exclusive fibrillar S-PANI provide unobstructed channels for charge transport and electrolyte infiltration. Preliminary electrochemical studies revealed that the capacitance of the composite electrode reached 316.8 F g−1 and 345.4 F g−1, and established exceptional capacitance retention rates of 92.8% and 93.7% after 5000 cycles for S-PANI/OCNT and S-PANI/SCNT composite, respectively, making it a potential candidate for imminent energy storage devices.

Enhanced methane hydrate formation in the highly dispersed carbon nanotubes-based nanofluid

The hydrate-based technology has been viewed as a great potential approach for the natural gas storage and transportation, whose commercialization however is challenged by the limited energy storage efficiency and slow formation kinetics. In this work, we used carbon nanotubes (CNTs) as carriers and covalently grafted functional group of -SO3- (similar to the hydrophilic group contained in sodium dodecyl sulfate) onto the nano-carriers surface to prepare a novel promoter, sulfonated carbon nanotubes (SCNTs). The SCNTs nanofluid showed higher dispersity and stability than the pristine CNTs (PCNTs). In the methane hydrate formations, the high methane storage capacity of 142 v/v in the SCNTs nanofluid was achieved, whereas 50–65 v/v was obtained with the oxidized CNTs (OCNTs) or PCNTs as promoter. Interestingly, the larger number of sulfonate groups grafted on CNTs, the shorter hydrate formation period and the smaller hydrate reaction stochasticity were obtained. The formation rate was enhanced from 0.237 mmol/(mol water·min) to 0.413 mmol/(mol water·min) when SCNTs concentration grew from 25 mg/L to 150 mg/L. Additionally, the SCNTs kept excellent recycling performance at ten reuses in the methane hydrate formations, which was meaningful to the actual hydrate-based gas storage and transportation.

Optimized structure and electrochemical properties of sulfonated carbon nanotubes/Co–Ni bimetallic layered hydroxide composites for high-performance supercapacitors

Technical development in electronic devices is frequently stifled by their insufficient capacity and cyclic stability of energy-storage devices. The nano-structured materials have sensational importance for providing novel and optimized combination to overcome exiting boundaries and provide efficient energy storage systems. Metal hydroxide materials with high capacity for pseudo-capacitance properties have grabbed special attention. Lately, the blend of nickel and cobalt hydroxides has been considered as a favorable class of metallic hydroxide materials owing to their comparatively high capacitance and exceptional redox reversibility. The sulfonated carbon nanotube fluid (SCNTF) was prepared by the ion exchange method to be utilized as the exceptional templates due to astonishing specific surface area, ensuring the maximum utilization of the active material. The CoNi-layered double hydroxides (LDHs)/SCNTF core-shell nanocomposite was prepared by the simple solvothermal method. Structural analysis showed that the composite material had the high conductance of carbon materials, the pseudo-capacitance characteristics of metal hydroxides, and porous structure, which facilitates the ion shuttle when the electrolyte reacts with the active material. Electrochemical analysis results showed that CoNi-LDHs/SCNTF had excellent rate performance, reversible charge-discharge properties and cycle stability. It exhibited an extreme specific capacity of 1190.5 F g−1 at a current density of 1 A g−1; whereas specific capacity remained 953.7 F g−1 at the current density was 10 A g−1. In addition, the capacity retention rate after 5000 charge-discharge cycles at a current density of 20 A g−1 was 81.0%. The results indicated that the CoNi-LDHs/SCNTF core-shell nanocomposite material is cost efficient and an effective substitute in energy storage applications.

Morphology of electrospun PVA nanofibers enhanced with graphene oxide, poly (3,4-ethylenedioxythiophene): Polystyrene sulfonate (PEDOT:PSS) and multiwalled carbon nanotubes

Morphology of poly(vinyl alcohol) (PVA) nanofibers was studied while varying needle-collector distance and concentrations of graphene oxide, poly (3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), and functionalized multiwalled carbon nanotubes. Most notably, we found that variations in PVA nanofiber diameter of ~ 34 nm exist in the radial area of electrospinning; the variation is believed to be the result of a fringing electric field effect at the edge of the collector plates. Needle-collector distance was varied between 10 and 17 cm, and FESEM images revealed average fiber diameter decreased from 173 nm to 144 nm with no obvious change in morphology at both nanofiber diameters. Similarly, electrospinning of PVA-GO solution at 17 cm resulted in nanofibers with decreased average diameter of 197 nm (σ = 97 nm), compared with PVA alone (349 nm, σ = 87 nm) with no obvious change in morphology. The average diameter of PVA nanofibers then increased with added PEDOT:PSS to 244 nm, σ = 75 nm. PVA-MWCNT samples at 2 wt% and 4 wt% showed no beading, while at 6, 8, and 10 wt%, beads were prevalent in the fibers. The presence of beads could be the result of re-agglomeration of MWCNTs in the electrospinning solution at higher wt%. No clear trend was found with increasing concentrations of MWCNTs, with average nanofiber diameters varying in the range of 115 – 206 nm.

Mechanically stable and economically viable polyvinyl alcohol-based membranes with sulfonated carbon nanotubes for proton exchange membrane fuel cells

Development of low-cost membranes with enhanced mechanical strength and minimal sensitivity to variation in humidity, for PEMFC applications.

Enhanced desalination performance utilizing sulfonated carbon nanotube in the flow-electrode capacitive deionization process

The novel sulfonated carbon nanotubes (CNT-S) material was successfully introduced into the flow-electrode capacitive deionization (FCDI) process, which could reduce inter-tube aggregation and promote good contact between the active material and the current collector by forming the conductive network. The physical characteristic and electrochemical tests were carried out to analyze the effects of surface properties of CNT-S on the suspension stability and electrochemical performance of the flow-electrode, respectively. The results indicated that the CNT-S flow-electrode slurry displayed better dispersible property and suspension stability, higher charging capacity and lower ohmic impedance than that of the CNT flow-electrode slurry. Moreover, the desalination performance of the CNT-S flow-electrode was investigated based on the symmetric FCDI cell. For the 2.0 wt% CNT-S flow-electrode, the mean electrosorption rate of 4.85 mg/(g·min) and the salt removal efficiency of 45.8% were achieved in 1.0 g/L NaCl solution, both of which were all about 1.6 times that of the CNT flow-electrode. It was also found that the CNT-S FCDI system coupled with the adsorption and desorption process simultaneously can achieve high electrode regeneration efficiency by controlling the flux ratio of the washing fluid to the feed solution. Therefore, the CNT-S flow-electrode was a promising active material in the FCDI process and displayed prominent advantage in improving the desalination performance of the FCDI cell.