Carboxyl-functionalized Carbon Nanotubes Research Articles

Enhanced interfacial bonding of AF/PEEK composite based on CNT/aramid nanofiber multiscale flexible-rigid structure

The application of aramid fiber (AF)/polyetheretherketone (PEEK) composites is currently hindered by the inert surface and poor wettability of AF, resulting in weak interfacial adhesion and poor mechanical properties. Surface coating and the introduction of nanostructures have been proven to be effective approaches to address this problem. Herein, a simple hybrid sizing agent has been developed to modify the AF surface, consisting of soluble polyimide (PI) as a compatibilizer, carboxyl-functionalized carbon nanotubes (CNT-COOH) as a rigid unit, and aramid nanofibers (ANF) as a flexible component. The synergetic effects of PI and the multiscale flexible-rigid structure (CNT-COOH/ANF) contribute to the formation of chemical and physical bonds between AF and PEEK matrix, further improving the interfacial adhesion and stress transfer efficiency. Attributed to the enhanced wettability and roughness of AF, compared with unsized AF, the flexural strength (220.97 MPa), modulus (13.26 GPa), ILSS (13.36 MPa), and storage modulus (12.93 GPa) of the AF/PEEK composite increase by 132.60 %, 99.00 %, 18.97 %, and 82.70 % respectively. Additionally, the flexible-rigid nanonetwork facilitates the penetration of the PEEK resin into pore spaces. This simple and effective approach exhibits promising potential in enhancing the interfacial bonding of AF/PEEK composites.

Photoconductivity of functionalized carbon nanotubes

Investigation of carbon nanotubes is a modern trend due to their combination of unique physical, chemical, electrical, and optical properties. Carboxyl-functionalized carbon nanotubes (fCNTs) for investigation of photoelectrical properties were synthesized. The photo-sensitivity spectra of a carboxyl-functionalized CNT sample for voltage range from 1 to 9 V, and for the spectral range from 400 to 900 nm were investigated. The voltage equal to 1 V generated lower photosensitivity in the broadband wavelength range for visible to near-infrared. The most efficient photocurrents of fCNTs were received for a voltage of 5 V in the wavelength range λp~400-800 nm and for voltage U=3V in the broadband spectral range λp~400-900 nm. The experimental data analysis helped to determine the widest photosensitivity range, as well as the highest sensitivity value. As result, the voltage U=5V was obtained. Here, the most significant photocurrent peak with Ip~2.67 μA for wavelength λ~720 nm was observed. A comparison between the photosensitivity spectra of fCNTs and pure CNTs shows that the photosensitivity of fCNTs has increased significantly. Thus, the maximum photosensitivity for fCNTs is Ip ~ 2.67 μA, and for pure CNTs, it equals Ip ~ 0.185 μA. A 14-fold enhancement of photosensitivity for fCNT has been registered. The mathematical analysis of spectral dependencies of generated photocurrents under different applied voltages can be described using fourth-order polynomials. The I-V characteristics for wavelengths 760 nm and 780 nm have the same trend with the shift of photocurrent maximum to the lower parameters of voltage. The carboxyl-functionalized nanotubes can be effectively used as light detectors and in optoelectronic applications.

Adsorption performance and mechanisms of Co2+ onto carboxyl-functionalized carbon nanotubes

In this study, carboxyl-functionalized carbon nanotubes (cCNTs) were used as adsorbents for nuclide Co2+, and their adsorption characteristics and mechanisms were investigated. The cCNTs presented a characteristic tubular morphology, a moderately ordered crystal structure, and good thermal stability. Their specific surface area and isoelectric point were 405.6 m2/g and 2.4, respectively. The adsorption of Co2+ onto the cCNTs exhibited rapid kinetics, with a maximum adsorption capacity of 25.1 mg/g at 303 K. This adsorption process is pH-sensitive, with higher pH resulting in better adsorption capacity. Moreover, the order of selective adsorption onto the cCNTs was Co > Sr > Cs, and the presence of coexisting cations in the simulated seawater was found to influence Co adsorption. The adsorption mechanisms of Co on cCNTs involved physical and chemical adsorption, driven by electrostatic interactions and coordination with the active sites. Density functional theory (DFT) calculation revealed that the adsorption energy of Co2+ onto cCNTs was −197.6 kcal/mol, and O atoms on the surface of cCNTs played a vital role in coordination. This study was beneficial for comprehending the adsorption performance and mechanism, particularly concerning the competitive adsorption performance of nuclides onto carbon nanotubes (cCNTs).

Thermal properties and mechanical behavior of functionalized carbon nanotube-filled polypropylene composites using molecular dynamics simulation

Polypropylene (PP) is widely recognized as an environmentally friendly material for cable insulation due to its good insulation performance and environmental friendliness. One common method for enhancing the overall performance of PP is the addition of nanoparticles. To analyze the influence of different functionalized multi-walled carbon nanotubes (MWCNT) fillers on the properties of PP/MWCNT composite materials from a microscale perspective, molecular dynamics is used to construct pure PP models and models filled with untreated carbon nanotubes (UFCNT), amino-functionalized carbon nanotubes (AFCNT), carboxyl-functionalized carbon nanotubes (CFCNT), and hydroxyl-functionalized carbon nanotubes (HFCNT) (functionalized MWCNT with 4 or 8 functional groups grafted onto them). The simulation results indicate that the doping of nanotubes can effectively enhance the thermodynamic properties of PP. Among them, PP/CFCNT-8 exhibits the most significant improvement in melting temperature and mechanical properties, with an increase in melting temperature of 88.85 K and a 184.52 % increase in Young's modulus. The melting temperature of PP/HFCNT-8 is second only to PP/CFCNT-8, with an increase of 82.59 K. The results indicate that the thermodynamic properties of PP nanocomposites filled with functionalized MWCNT are improved with the grafting rate. The filling of functionalized MWCNT alters the microscale properties of PP composites, with a significant decrease in root mean square displacement (RMSD), and improvement in free volume fraction (FFV) as well as interfacial binding energy, which can better maintain the electrical properties of PP insulation materials. Applying functionalized carbon nanotubes to filled PP can significantly increase the electrical insulation properties of PP cable materials, which provides meaningful guidance for adopting polypropylene cable insulation materials.

Poly(ionic liquid)-coated hydroxy-functionalized carbon nanotube nanoarchitectures with boosted catalytic performance for carbon dioxide cycloaddition

Poly(ionic liquid)s (PILs) bearing high ionic densities are promising candidates for carbon dioxide (CO2) fixation. However, efficient and metal-free methods for boosting the catalytic efficiencies of PILs are still challenging. In this study, a novel family of poly(ionic liquid)-coated carbon nanotube nanoarchitectures (CNTs@PIL) were facilely prepared via a noncovalent and in-situ polymerization method. The effects of different carbon nanotubes (CNTs) and PILs on the structure, properties, and catalytic performance of the composite catalysts were systematically investigated. Characterizations and experimental results showed that hybridization of PIL with hydroxyl- or carboxyl-functionalized CNTs (CNT-OH, CNT-COOH) endows the composite catalyst with increased porosity, CO2 capture capacity, swelling ability and diffusion rate with respect to individual PIL, and allows the CNTs@PIL to provide H-bond donors for the synergistic activation of epoxides at the interfacial layer. Benefiting from these merits, the optimal composite catalyst (CNT-OH@PIL) delivered a super catalytic efficiency in the cycloaddition of CO2 to propylene oxide, which was over 4.5 times that of control PIL under metal- and co-catalyst free conditions. Additionally, CNT-OH@PIL showed high carbon dioxide/nitrogen (CO2/N2) adsorptive selectivity and could smoothly catalyze the cycloaddition reaction with a simulated flue gas (15% CO2 and 85% N2). Furthermore, the CNT-OH@PIL exhibited broad substrate tolerance and could be readily recycled and efficiently reused at least 12 times. Hybridization of PIL with functionalized CNTs provides a feasible approach for boosting the catalytic performance of PIL-based solid catalysts for CO2 fixation.

PGM-Based Ammonia Oxidation Catalysts for Anion-Exchange Membrane Direct Ammonia Fuel Cells

Low-temperature direct ammonia fuel cells (DAFCs) use carbon-neutral ammonia as a fuel, which has attracted increasing attention recently due to ammonia's low source-to-tank energy cost, easy transport and storage, and wide availability. However, current DAFC technologies are greatly limited by the kinetically sluggish ammonia oxidation reaction (AOR) at the anode. Herein, we report an AOR catalyst, in which ternary PtIrZn nanoparticles with an average size of 2.3 ± 0.2 nm were highly dispersed on a binary composite support comprising cerium oxide (CeO2) and zeolitic imidazolate framework-8 (ZIF-8)-derived carbon (PtIrZn/CeO2-ZIF-8) through a sonochemical-assisted synthesis method. The PtIrZn alloy, with the aid of abundant OHad provided by CeO2 and uniform particle dispersibility contributed by porous ZIF-8 carbon (surface area: ∼600 m2 g−1), has shown highly efficient catalytic activity for the AOR in alkaline media, superior to that of commercial PtIr/C. The rotating disk electrode (RDE) results indicate a lower onset potential (0.35 vs. 0.43 V), relative to the reversible hydrogen electrode at room temperature, and a decreased activation energy (∼36.7 vs. 50.8 kJ mol−1) relative to the PtIr/C catalyst. Notably, the PtIrZn/CeO2-ZIF-8 catalyst was assembled with a high-performance hydroxide anion-exchange membrane to fabricate an alkaline DAFC, reaching a peak power density of 91 mW cm−2. Unlike in aqueous electrolytes, supports play a critical role in improving uniform ionomer distribution and mass transport in the anode. PtIrZn nanoparticles on silicon dioxide (SiO2) integrated with carboxyl-functionalized carbon nanotubes (CNT–COOH) were further studied as the anode in a DAFC. A significantly enhanced peak power density of 314 mW cm−2 was achieved. Density functional theory calculations elucidated that Zn atoms in the PtIr alloy can reduce the theoretical limiting potential of *NH2 dehydrogenation to *NH by ∼0.1 V, which can be attributed to a Zn-modulated upshift of the Pt–Ir d-band that facilitates the N–H bond breakage.

Carboxyl-functionalized carbon nanotubes coordinated with two-dimensional bimetallic porphyrin-based CuMOFs for efficient electrocatalytic CO2 reduction

The focus on electrocatalytic CO2 reduction to lessen surplus CO2 emissions and counteract the greenhouse effect has intensified. The synergistic combination of metal-organic frameworks (MOFs) and carbon-based materials has emerged as a potentially effective method to enhance electron transfer efficiency. In this study, we created a Cu-(Co+Cu)PMOF/CNT-COOH hybrid by integrating a two-dimensional bimetallic porphyrin-based CuMOF with carboxyl-modified carbon nanotubes. When compared with (Co+Cu)PMOF/CNT, which is formed through weak π-π interaction, our hybrid demonstrates superior stability, additional exposed active sites, and a higher electron transfer rate from CNT-COOH to Cu-(Co+Cu)PMOF, resulting in improved electrocatalytic action for CO2 reduction. Electrochemical tests indicate that the Cu-(Co+Cu)PMOF/CNT-COOH hybrid achieves a CO faradic efficiency of 95.98% with an impressive current density of -3.48 mA‧cm-2 at an overpotential of -0.9 V vs. RHE, significantly outperforming single metal porphyrin-based CuMOF counterparts. This research offers fresh perspective on how to thoughtfully construct high-performance electrocatalytic hybrid materials for CO2 reduction.

Role of alkane-[formula omitted],[formula omitted]-diamine in the nanostructure of carboxylic functionalized multiwalled carbon nanotubes grafted on amino-enriched nylon fabric toward metal ion absorption

Through a direct two-step functionalization reaction with alkane-α,ω-diamine (H2N(CH2)nNH2, n = 2, 4, 6, 8) and carboxylic functionalized multi-walled carbon nanotubes (MWCNT-COOH), the membrane labeled as C@(A[n]-nylon), is made up of nylon 6 fabric and intermediate amino-enriched nylon (A[n]-nylon) fabric. FTIR and Raman spectra confirm the efficient formation of amide bonds between the two amino heads of the alkane-α,ω-diamine, both with hydrolyzed nylon 6 and MWCNT-COOH. As a result, MWNCT-COOH were grafted to the nylon fiber side wall without causing damage to the nylon backbone. The SEM images confirm the plexus of MWCNT covering the amino-enriched nylon fibers. The long carbon chain of alkane-α,ω-diamine as an arm help amino groups reach beyond the surface of polyamide fiber, making it easier for -COOH groups of MWCNT-COOH to form amide bonds instead of being ejected when approaching CO groups on the polyamide surface. As-prepared C@(A8-nylon) membranes have metal ion rejection of more than 10% in vacuum filtration test with solution of M(CH3COO)2 (M = Ca, Co, Pb). Such membrane is long lasting for about 20 cycles, showing potential of turning polyamide fabrics with large pore sizes into highly efficient nanofiltration of reverse osmosis (RO) membranes. This unique structure opens up new possibilities for nanocomposite membranes and mass production by the proposed simple method.

In vitro comparative cytotoxic assessment of pristine and carboxylic functionalized multiwalled carbon nanotubes on LN18 cells.

Multiwalled carbon nanotubes (MWCNTs) have been used in biomedical applications due to their ability to enter the cells. Carboxylic functionalization of MWCNT (MWCNT-COOH) is used to mitigate the toxicity of MWCNTs. Our study focuses on comparing the toxicity of MWCNT and MWCNT-COOH on the neuronal cells, LN18. Concentrations of 5, 10, 20, and 40 µg ml-1 were used for the study, and cytotoxicity was determined at 0, 1, 3, 6, 12, 24, and 48 h of incubation. Cell viability was assessed by Trypan Blue, MTT, and Live dead cell assays, and the oxidative stress produced was determined by reactive oxygen species (ROS) and Lipid peroxidation assays. MWCNT-COOH showed higher cell viability than MWCNT for 20 and 40 µg ml-1 at 24 and 48 h. This was also visually observed in the live dead cell imaging. However, at 48 h, the morphology of the cells appeared more stretched for all the concentrations of MWCNT and MWCNT-COOH in comparison to the control. A significant amount of ROS production can also be observed at the same concentration and time. Viability and oxidative stress results together revealed that MWCNT-COOH is less toxic when compared to MWCNT at longer incubation periods and higher concentrations. However, otherwise, the effect of both are comparable. A concentration of 5-10 µg ml-1 is ideal while using MWCNT and MWCNT-COOH as the toxicity is negligible. These findings can further be extended to various functionalizations of MWCNT for wider applications.

Low temperature co-fired ceramic (LTCC)- based biosensor for detection of vanadium using immobilized Arachis hypogaea alkaline phosphatase on multi walled carbon nanotubes ethyl cellulose sponge matrix

Studies on enzyme based thermometric biosensor are limited. Here, we report on fabrication of an alkaline phosphate based thermometric biosensor. We designed alkaline phosphatase inhibition based biosensor for detection of vanadium using immobilized alkaline phosphatase on multi walled carbon nano tubes (MWCTs) ethyl cellulose sponge matrix. We isolated protein from plant source, partially purified and fabricated a miniature ceramic viz. LTCC (low temperature co-fired ceramics technology) based biosensor for detection of vanadium. This biosensor consists of a microreaction chamber with buried heaters. Alkaline phosphatase has been isolated from the seeds of ‘Arachis hypoghaea’ was studied for its biochemical properties viz. optimum pH and temperature. The partially purified enzyme was immobilized using carboxyl-functionalised carbon nanotubes (CNTs) by cross linking with epichlorohydrin (ECH) along with a matrix of ethyl cellulose. The developed LTCC based biosensor on testing indicated its linear response to vanadium concentration up to 9 mM with a relatively high sensitivity of about 147 nA/mM. Thus, we have demonstrated a LTCC based biosensor using immobilized alkaline phosphatase for detection of vanadium.

An alternative method of dispersive solid‐phase extracting Hg (II) from environmental aqueous solutions using carboxylic functionalized carbon nanotubes

This study is a simple method for rapid sample preparation before instrumental experiment, which is an important tool and the main step in an analytical proceeding. Till now, different sample preparation procedures based on solid-phase extraction manner were developed to isolate different types of analytes from different matrices. In this method, the preconcentration and removal of trace amounts of Hg (II) ion in aqueous samples with nanotubes functionalized carboxyl are displayed. The analysis of Hg2+ ions concentration in water solutions was accomplished by flame atomic absorption spectroscopy. Some parameters including the pH, value, and type of desorption eluent solvent, extraction time, ions effect etc. were optimized. The Freundlich, Langmuir, Temkin, and Dubinin–Radushkevich models were employed to estimate Hg (II) ions adsorption. The Freundlich model was obtained from the study of isotherm studies. The kinetic studies demonstrate the adsorption of Hg (II) ions by adsorbent fitted with the pseudo-second-order type and resulting from that chemisorption is the rate-limiting process in the Hg (II) adsorption. The concentration parameter such as level of detection of proposed method, and relative standard deviation test were obtained as 20.83, 6 µg L−1, and 1.16%, respectively.

Electrochemical response of carbon paste electrodes modified with carbon nanotubes: Effects of temperature of nitrogen doping and oxygen functionalization

Carbon paste electrodes (CPE) were modified with nitrogen-doped carbon nanotubes (N-CNTs) synthesized at 750 °C (N-CNT750) and 850 °C (N-CNT850), carboxyl functionalized carbon nanotubes (MWCNTCOOH), and pristine carbon nanotubes (MWCNT). Their electrochemical properties were investigated and compared towards a common redox probe, potassium ferricyanide (K3[Fe(CN)6]). The electrochemical responses were probed using cyclic voltammetry, and the results unveiled that modification with carbon nanotubes enhanced anodic peak currents (Ipa) for the electrodes CPE/MWCNTCOOH, CPE/N-CNT750 and CPE/N-CNT850 (Ipa, p < 0.05 in relation to pure CPE). In particular, CPE modified with N-CNTs synthesized at 850 °C (CPE/N-CNT850) exhibited better electrochemical response, with lower peak-to-peak potential separation (ΔEp, p < 0.05 in relation to pure CPE). Complementary studies were conducted to investigate the electroactive area (A) and heterogeneous electron-transfer kinetics (k0). CPE/N-CNT850 (0.034 ± 0.005 cm2) and CPE/MWCNTCOOH (0.057 ± 0.002 cm2) presented more satisfactory results for the anodic and cathodic electroactive area (A), respectively. Kinetic studies revealed a higher k0 (1.03 × 10−3 cm.s−1) for the CPE/N-CNT850 electrode. Differential pulse voltammetry was employed for the electrochemical detection of Acetaminophen (AC). The response was linear for an AC concentration range from 66.2 to 259.7 μmol L−1, with the lowest detection limit (LOD) of 0.37 μmol L−1 and the highest sensitivity of 0.244 ± 0.002 μA L μmol−1 for the respective electrodes CPE/N-CNT850 and CPE/MWCNTCOOH. The CPE/N-CNT850 and CPE/MWCNTCOOH electrodes show the best correlation of results, the presence of polar groups on the surface of MWCNTCOOH and a higher amount of graphitic nitrogen bond of N-CNT850 suggest that these CNTs are particularly promising for applications in electrochemical fields.

Constructing 3D interconnected CNTs network in PA6 composites with well-dispersed UHMWPE for excellent tribological and heat dissipation properties

Recently, the requirements for wear resistance of materials under harsh pressure-velocity (PV) conditions become increasingly high. Herein, ultra-high molecular weight polyethylene (UHMWPE) via a novel efficient plasma treatment was introduced to disperse evenly in polyamide 6 (PA6) matrix and a three-dimensional (3D) interconnected carboxyl functionalized carbon nanotubes (CNTs) network was further constructed in PA6 composites via solvent-free ball milling and compression molding to achieve excellent tribological and heat dissipation properties. Friction tests show that the incorporation of the plasma-treated UHMWPE, as well as CNTs, leads to a significant reduction of the coefficient of friction (COF) of PA6 by 77.5%. Moreover, the 3D interconnected CNTs network forms a high-speed pathway for heat transfer and achieves a relatively high thermal conductivity (TC) of 0.40 W/(m K) at an ultra-low level of 0.2 wt% CNTs, which is 42.9% higher than that of pure PA6. Interestingly, the maximum contact temperature monitored by the infrared camera reduces greatly from 108.9 °C to 57.2 °C, indicating that low COF and high TC are beneficial for low contact temperature. As a result, the specific wear rate of PA6 composites is dramatically decreased by 98.1% compared to pure PA6. The strategy can be used to produce advanced bearing bushes and wearing laths in industrial applications.

Stability of Carboxyl-Functionalized Carbon Nanotubes in Simulated Cement Pore Solution and Its Effect on the Compressive Strength and Porosity of Cement-Based Nanocomposites

The application of carbon nanotubes to produce cementitious composites has been extensively researched. However, the dispersion of this nanomaterial remains a technical limitation for its use. Thus, initially, this study assessed the stability of carboxyl-functionalized CNT on aqueous suspensions and simulated cement pore solution for 6 h through UV–visible spectroscopy. Subsequently, a CNT content of 0.1% by cement weight was incorporated into the cement pastes, and the compressive strength after 7, 14, 28, and 91 days was evaluated. In addition, the porosity of the CNT cementitious composites at 28 days of hydration was investigated by mercury intrusion porosimetry (MIP), and the microstructure was evaluated via scanning electron microscopy (SEM). The simulated cement pore solution’s alkaline environment affects the CNT stability, progressively reducing the dispersed CNT concentration over time. CNT reduced the cementitious matrix pores &lt; 50 nm by 8.5%; however, it resulted in an increase of 4.5% in pores &gt; 50 nm. Thus, CNT incorporation did not significantly affect the compressive strength of cement pastes. SEM results also suggested a high porosity of CNT cementitious composites. The CNT agglomeration trend in an alkaline environment affected the CNT performance in cement-based nanocomposites.

Ptirm (M=Zn, Ni) Ammonia Oxidation Catalysts for Anion-Exchange Membrane Direct Ammonia Fuel Cells

Low-temperature direct ammonia fuel cells (DAFCs) use carbon-neutral ammonia as a fuel, which has attracted increasing attention recently due to ammonia's low source-to-tank energy cost, easy transport and storage, and wide availability. However, current DAFC technologies are greatly limited by the kinetically sluggish ammonia oxidation reaction (AOR) at the anode. Herein, we report an AOR catalyst, in which ternary PtIrZn nanoparticles with an average size of 2.3 ± 0.2 nm were highly dispersed on a binary composite support comprising cerium oxide (CeO2) and zeolitic imidazolate framework-8 (ZIF-8)-derived carbon (PtIrZn/CeO2-ZIF-8) through a sonochemical-assisted synthesis method. The PtIrZn alloy, with the aid of abundant OHad provided by CeO2 and uniform particle dispersibility contributed by porous ZIF-8 carbon (surface area: ∼600 m2 g−1), has shown highly efficient catalytic activity for the AOR in alkaline media, superior to that of commercial PtIr/C. The rotating disk electrode (RDE) results indicate a lower onset potential (0.35 vs. 0.43 V), relative to the reversible hydrogen electrode at room temperature, and a decreased activation energy (∼36.7 vs. 50.8 kJ mol−1) relative to the PtIr/C catalyst. Notably, the PtIrZn/CeO2-ZIF-8 catalyst was assembled with a high-performance hydroxide anion-exchange membrane to fabricate an alkaline DAFC, reaching a peak power density of 91 mW cm−2. Unlike in aqueous electrolytes, supports play a critical role in improving uniform ionomer distribution and mass transport in the anode. PtIrZn nanoparticles on silicon dioxide (SiO2) integrated with carboxyl-functionalized carbon nanotubes (CNT–COOH) were further studied as the anode in a DAFC. A significantly enhanced peak power density of 314 mW cm−2 was achieved.

Modulating the adsorption orientation of methionine-rich laccase by tailoring the surface chemistry of single-walled carbon nanotubes

Achieving fast electron transfer process between oxidoreductase and electrodes is pivotal for the biocathode of enzymatic biofuel cells (EBFCs). However, in-depth understanding of the interplay mechanism between enzymes and electrode materials remains challenging when designing and constructing EBFCs. Herein, atomic-scale insight into the direct electron transfer (DET) behavior of Thermus thermophilus laccase (TtLac) with a special methionine-rich β-hairpin motif adsorbed on the carboxyl-functionalized carbon nanotube (COOH-CNT) and amino-functionalized carbon nanotube (NH2-CNT) surfaces were disclosed by multi-scale molecular simulations. Simulation results reveal that electrostatic modification is an effective way to tune the DET behavior for TtLac on the modified-CNTs electrode surface. Surprisingly, the positively charged TtLac can be attracted by both negatively charged COOH-CNT and positively charged NH2-CNT surfaces, yet only the latter is capable to trigger the DET process due to the ‘lying-on’ adsorption orientation. Specifically, the T1 copper site is near the methionine-rich β-hairpin motif, which is the key binding site for TtLac binding onto the NH2-CNT surface via electrostatic interaction, π−π stacking and cation−π interaction. Moreover, TtLac on the NH2-CNT surface undergoes less conformational changes than those on the COOH-CNT surface, which allows the laccase stability and catalytic efficiency to be well preserved. These findings provide a fundamental guidance for future design and fabrication of methionine-rich laccase-based EBFCs with high power output and long lifespan.

Novel catalytic self-cleaning membrane with peroxymonosulfate activation for dual-function wastewater purification: Performance and mechanism

The integration of in-situ chemical oxidation (ISCO) and membrane separation technology (MST) was appealing for one-step efficient removal of complex dye-contaminated oily wastewater. However, the construction of catalytic membranes remains an arduous challenge due to the critical restriction of unsatisfactory degradation and poor stability. In current work, manganese dioxide (MnO2)/carboxyl functionalized carbon nanotube (C-CNT) composites were prepared through a facile hydrothermal process. It was found that, the degradation rate of rhodamine B (Rh B, 100 ppm) in MnO2/C-CNT (0.2 g/L)/peroxymonosulfate (PMS, 0.5 g/L) system reached 2.071 min−1, which was 4.6 and 10.9 times higher than that of MnO2 and C-CNT (0.4541 and 0.1942 min−1), respectively. The vacuum-assisted filtration was utilized to construct MnO2/C-CNT@ polyvinylidene fluoride (PVDF) membrane, which exhibited excellent filtration catalytic activity and stability for dyes and natural small-molecular organics. Scavenger experiments and electron paramagnetic resonance (EPR) analysis verified the synergistic effect of radicals and nonradicals while 1O2 was the dominator for Rh B degradation. The MnO2/C-CNT@PVDF membrane also possessed high permeation flux (170.2 L/(m2·h)), separation efficiency (99.5%) and anti-oil properties for filtrating n-hexane/water emulsion. Moreover, the modified membrane could achieve the dual purification for one-step catalytic degradation of dyes and oil/water separation. Meanwhile, the flux recovery rate of the prepared membrane reached 91% after filtering the PMS solution for 10 min, indicating its brilliant self-cleaning performance. This study provided a novel insight into development of dual-function catalytic self-cleaning membranes for water treatment.

Effect of hydroxyl and carboxyl-functionalized carbon nanotubes on phase morphology, mechanical and dielectric properties of poly(lactide)/poly(butylene adipate-co-terephthalate) composites

A series of poly(lactide)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) composites containing different types of multi-walled carbon nanotubes (CNTs) such as hydroxyl and carboxyl-functionalized CNTs were fabricated using the melt blending method. The multifunctional epoxy oligomer (ADR) was selected as a chain extender in order to enhance the compatibility between PBAT and PLA. It was revealed that the addition of ADR could induce CNTs-OH to locate at the PLA/PBAT interface. But the inhibition effect of CNTs-COOH on chain extension reaction in PLA/PBAT blend system led to a decrease in the interaction force between PLA and PBAT owing to the high efficiency of the reaction between CNTs-COOH and ADR. The ε’ of PLA/PBAT/4CNTs-OH composite was greater than that of PLA/PBAT/4CNTs-COOH composite because of the strong interaction between fillers and polymer matrix in PLA/PBAT/4CNTs-OH composite. The PLA/PBAT/4CNTs-OH composite showed a high ε’ (24.9) and a low tan δ (0.23), respectively. The adjacent CNTs-OH could act as assemble microcapacitors electrodes and the polymer acted as a dielectric to, which greatly increased the interfacial polarization. The PLA/PBAT/4CNTs-OH composite has excellent mechanical and dielectric properties.

Carboxyl-Functionalized Carbon Nanotubes Loaded with Cisplatin Promote the Inhibition of PI3K/Akt Pathway and Suppress the Migration of Breast Cancer Cells.

PI3K/Akt signaling is one of the most frequently dysregulated pathways in cancer, including triple-negative breast cancer. With considerable roles in tumor growth and proliferation, this pathway is studied as one of the main targets in controlling the therapies’ efficiency. Nowadays, the development of nanoparticle–drug conjugates attracts a great deal of attention due to the advantages they provide in cancer treatment. Hence, the main purpose of this study was to design a nanoconjugate based on single-walled carbon nanotubes functionalized with carboxyl groups (SWCNT-COOH) and cisplatin (CDDP) and to explore the potential of inhibiting the PI3K/Akt signaling pathway. MDA-MB-231 cells were exposed to various doses (0.01–2 µg/mL SWCNT-COOH and 0.00632–1.26 µg/mL CDDP) of SWCNT-COOH-CDDP and free components for 24 and 48 h. In vitro biological tests revealed that SWCNT-COOH-CDDP had a high cytotoxic effect, as shown by a time-dependent decrease in cell viability and the presence of a significant number of dead cells in MDA-MB-231 cultures at higher doses. Moreover, the nanoconjugates induced the downregulation of PI3K/Akt signaling, as revealed by the decreased expression of PI3K and p-Akt in parallel with PTEN activation, the promotion of Akt protein degradation, and inhibition of tumor cell migration.

Electrical and Electrochemical Sensors Based on Carbon Nanotubes for the Monitoring of Chemicals in Water-A Review.

Carbon nanotubes (CNTs) combine high electrical conductivity with high surface area and chemical stability, which makes them very promising for chemical sensing. While water quality monitoring has particularly strong societal and environmental impacts, a lot of critical sensing needs remain unmet by commercial technologies. In the present review, we show across 20 water monitoring analytes and 90 references that carbon nanotube-based electrochemical sensors, chemistors and field-effect transistors (chemFET) can meet these needs. A set of 126 additional references provide context and supporting information. After introducing water quality monitoring challenges, the general operation and fabrication principles of CNT water quality sensors are summarized. They are sorted by target analytes (pH, micronutrients and metal ions, nitrogen, hardness, dissolved oxygen, disinfectants, sulfur and miscellaneous) and compared in terms of performances (limit of detection, sensitivity and detection range) and functionalization strategies. For each analyte, the references with best performances are discussed. Overall, the most frequently investigated analytes are H+ (pH) and lead (with 18% of references each), then cadmium (14%) and nitrite (11%). Micronutrients and toxic metals cover 40% of all references. Electrochemical sensors (73%) have been more investigated than chemistors (14%) or FETs (12%). Limits of detection in the ppt range have been reached, for instance Cu(II) detection with a liquid-gated chemFET using SWCNT functionalized with peptide-enhanced polyaniline or Pb(II) detection with stripping voltammetry using MWCNT functionalized with ionic liquid-dithizone based bucky-gel. The large majority of reports address functionalized CNTs (82%) instead of pristine or carboxyl-functionalized CNTs. For analytes where comparison is possible, FET-based and electrochemical transduction yield better performances than chemistors (Cu(II), Hg(II), Ca(II), H2O2); non-functionalized CNTs may yield better performances than functionalized ones (Zn(II), pH and chlorine).