Modified Carbon Nanotubes Research Articles

Thermal/Near-Infrared Light Dual-Responsive Reconfigurable and Recyclable Polythiourethane/CNT Composite with Simultaneously Enhanced Strength and Toughness.

Thermoset polymers cross-linked by dynamic covalent bonds are recyclable and reconfigurable based on solid-state plasticity, resulting in less waste and environmental pollution. However, most thermoset polymers previously reported show thermal-responsive solid-state plasticity, depending much on external conditions and not allowing for local shape modulation. Herein, the isocyanate modified carbon nanotubes (CNTs-NCO) are introduced into the polythiourethane (PCTU) network with multiple dynamic covalent bonds by in situ polymerization to prepare the composite with thermal/light dual-responsive solid-state plasticity, reconfigurability, and recyclability. The introduction of CNTs-NCO simultaneously strengthens and toughens the PCTU composite. Moreover, based on the photothermal properties and light-responsive solid-state plasticity, the PCTU/CNTs composite or bilayer sample can achieve complex permanent shape by locally precise shape regulation without affecting other parts. This work provides a simple and reliable method for preparing high-performance polymer composite with light-responsive solid-state plasticity, which may be applied in the fields of sensing and flexible electronics.

A Flexible, Highly Accurate, and Stable Pressure Sensor with Anti‐Interference from Temperature, Sweat, and Humidity

AbstractThe highly accurate and stable pressure sensors with anti‐interference from varying sensing environments (temperature and humidity) are essential and a challenge in practical applications. However, real‐time electrical resistance fluctuation or even sensing inaccuracy are widely existed due to the sensibility of conductive materials towards varying temperatures, humidity, and sweat circumstance. Here, for the first time, the hydrophobic, non‐fluoride, titanium dioxide nanoparticle (TiO2‐ODI) modified carbon nanotube (CNT)/carbon black (CB) pressure sensors are introduced to achieve anti‐interference from temperature, droplets, and humidity. The sensors with a near‐zero temperature coefficient of resistance (near‐ZTC) effect (≈ −10 to 70 °C). The anti‐interference from moisture benefits from the effective isolation effect of the hydrophobic TiO2‐ODI layer. Meanwhile, the TiO2‐ODI/CNT/CB pressure sensors obtain a favorable sensitivity of 1.57 kPa−1, a fast response time of 20 ms, a negligible hysteresis ratio of 1.9%, prominent air permeability, and a facile scalable strategy. Hence, the TiO2‐ODI/CNT/CB pressure sensors are feasible for accurately and stably sensing under varying sensing environments by efficiently suppressing interferences from varying temperatures, high humidity, and sweat.

Surface Modification of Carbon Nanotubes by Ar Plasma Jet

Atmospheric pressure low temperature plasma jet (APPJ) is a technical direction that has attracted much attention in recent years. In this paper, argon is used as the working gas to produce highly active ions through funnel shaped glass tubes to modify the surface of carbon nanotubes. After the carbon nanotubes treated for 4 mins, SEM, water contact angle and FTIR detection results were compared before and after the experiment. The results showed that the hydrophobicity of carbon nanotubes was enhanced and the surface dispersion was improved after DBD plasma jet treatment.

Individual and Simultaneous Electrochemical Determination of Vanillin and Caffeine Using Nafion/Ethylenediamine Grafted Multi-walled Carbon Nanotubes Modified Boron-doped Diamond Electrode

Individual and Simultaneous Electrochemical Determination of Vanillin and Caffeine Using Nafion/Ethylenediamine Grafted Multi-walled Carbon Nanotubes Modified Boron-doped Diamond Electrode

Effects of Different End Functional Groups Hyperbranched Polymers-Modified Carbon Nanotubes on the Crystallization and Mechanical Properties of Poly(l-lactic acid) (PLLA).

Poly-l-lactic acid (PLLA) is a biodegradable polymer with great mechanical properties and good transparency, but its low crystallization rate greatly limits its application. Hyperbranched polyesters (HBPs) modified carbon nanotubes (CNTs) are an ideal nucleating agent to prove the crystallization of PLLA. To compare different terminal group HBPs' effect on the modification of CNTs and the crystallization of PLLA, through the condensation reaction and amidation reaction, CNTs-H202 and CNTs-N102 were prepared, respectively. The modification was confirmed by Fourier-transform infrared (FTIR) spectroscopy, X-ray electron spectroscopy (XPS), and thermogravimetric analysis (TGA). Using transmission electron microscopy (TEM), we observed the changes on the surface of modified CNTs. PLLA/CNT composites were prepared, and differential scanning calorimetry (DSC) was used to investigate the crystallization behavior of the composites. The mechanical properties of PLLA/CNT composites were investigated as well. The results showed that the modified CNTs had a better promotion on PLLA crystallization and mechanical properties than the unmodified CNTs. CNTs-N102 had a slight advantage on the promotion on PLLA crystallization, which was caused by the lower grafting rate of HBP N102, and CNTs-H202 had a better promotion on the mechanical properties of PLLA, which was caused by the better compatibility with PLLA. In conclusion, hydroxy-terminated HBP is a better CNT modified material than amino-terminated HBP.

1-(2-pyridylazo) 2-naphthol-modified bacterial cellulose/multiwall carbon nanotube/silicon dioxide membrane for selectively adsorbed Er (III)

Considering the economic benefits and environmental pollution, it is of great significance to recover rare earth elements from wastewater. In this article, the modified bacterial cellulose is the raw material, and multi-wall carbon nanotubes are added to construct together. The ion imprinting technology is introduced to prepare a silicon-based modified film for the recovery of Er(III) and selectively adsorption function of Er(III) in experiments. The maximum adsorption amount of modified carbon nanotube silicon bacterial cellulose composite imprinted membrane can reach 46.52 mg L−1, and the adsorption capacity is greatly improved compared to other methods that of the non-imprinted membrane. The adsorption efficiency of Er(III) can reach 92%.

Corrosion resistance enhancement of a sol-gel coating by incorporation of modified carbon nanotubes: Artificial neural network (ANN) modeling and experimental explorations

A computational method of data analysis based on an artificial neural network (ANN) has been proposed to model the behavior of a sol-gel coating modified with different amounts of oxidized multi-walled carbon nanotubes (O-MWCNT). The constructed ANN model utilized a single hidden-layer perceptron. The Levenberg–Marquardt algorithm optimization procedure was applied as a learning algorithm. In this model, the input variables were the different concentrations of O-MWCNT, the immersion time, and the real part of the impedance, and consequently, the imaginary part of the impedance was considered as the output variable. Then, the accuracy of the optimized model was evaluated using the correlation coefficient and schematically comparing the simulated data with the experimental ones in the Nyquist diagrams. Furthermore, the protection performance of the sol-gel layer was enhanced by the incorporation of O-MWCNTs. To this end, the different concentrations of the O-MWCNTs up to 0.9 % wt./wt. have been added to a silane layer, and the performance was followed by electrochemical exploration using electrochemical impedance spectroscopy (EIS). The results revealed the improvement of the protective performance of the silane coating by increasing the content of the O-MWCNTs in the matrix, followed by the enhancement of barrier properties. Moreover, the polarization curves, in agreement with the AC impedance spectra, reflected the significant decrease in the corrosion current density by employing more content of O-MWCNTs in the silane-based coatings.

Electroanalytical Detection of Indigo Carmine in Presence of Tartrazine Using a Poly(dl-phenylalanine) Modified Carbon Nanotube Paste Electrode

Certain dyes are deleterious to the biological system, including animals and plants living in the water sources, soil sources, and so on. Thus, the analysis of these dyes requires a potent, quick, and cost-effective approach to the environmental samples. The present research work shows a modest, low-cost, and eco-friendly electrochemical device based on poly(dl-phenylalanine)-layered carbon nanotube paste electrode (P(PAN)LCNTPE) material for indigo carmine (ICN) detection in the presence of tartrazine. The cyclic voltammetric, field emission scanning electron microscopy, and electrochemical impedance spectroscopic methods were operated for the detection of the redox nature of ICN and electrode material surface activities, respectively. In better operational circumstances, P(PAN)LCNTPE provided better catalytic activity for the redox action of ICN than the bare carbon nanotube paste electrode. The P(PAN)LCNTPE showed good electrochemical activity during the variation of ICN concentrations ranging from 0.2 µM to 10.0 µM with improved peak current, and the limit of detection was about 0.0216 µM. Moreover, the P(PAN)LCNTPE material was performed as a sensor of ICN in a tap water sample and shows adequate stability, repeatability, and reproducibility.

Polyethylene glycol modified-carbon nanotubes as materials for biomedical applications: In vitro and in vivo sub-acute toxicity evaluation

• MWCNTs modification minimizes their toxicity while improving their performance. • Functionalized MWCNTs displays high percentage of cells viability on human skin fibroblast cells. • Functionalized MWCNTs induces none to minimum sub-acute toxicity in rats. Multiwalled-carbon nanotubes (MWCNTs) serve as one of the popular options for biomedical applications. Nonetheless, MWCNTs toxicity and biosafety are concerned, particularly on their aggregation after systemic distribution, necessitating modification. Although there was evidence of the toxicity of MWCNTs in the literature, the inconsistent parameters reported by each study, however, provide limited information to claim the sub-acute toxicity caused by MWCNTs. Thus, the present study aims to evaluate the subacute toxicity of modified MWCNTs, both in vitro and in vivo. In this study, polyethylene glycol-MWCNTs (PEG-MWCNTs) were characterized by standard characterization analysis. Exposure of PEG-MWCNTs on normal human fibroblast cells in vitro exhibited a high percentage of cell viability while in vivo assessment demonstrated no significant changes in rats’ behavior, body weight and serum biochemical analysis. Moreover, organ histological analysis indicated no significant changes following PEG-MWCNTs administration. No-observed-adverse-effect-level (NOAEL) value from this study was determined at 4 mg/kg. Results from this study suggested that modified MWCNTs induced minimal toxicity effect following systemic delivery in rats, thus, could be an excellent material for biomedical applications.

Activation of persulfate by vanadium oxide modified carbon nanotube for 17β-estradiol degradation in soil: Mechanism, application and ecotoxicity assessment

Steroid hormones in the environment have attracted public attention because of their high endocrine-disrupting activity even at rather low exposure level. Excessive hormones in the soil from the pollutant discharge of intensive farming would pose a potential threat to the ecology and the human health. Vanadium oxide modified carbon nanotube (VOX-CNT) was synthesized and applied as persulfate (PDS) activator to reduce17β-estrogen (17β-E2) in soil. 86.06 % 17β-E2 could be degraded within 12 h. Process of materials exchange during oxidation was interfered by soil, resulting in insufficient degradation of 17β-E2, but the active species involved in 17β-E2 degradation would also be enriched by it. 17β-E2 was adsorbed on the VOX-CNT surface and directly degraded mainly by the active species generated on the catalyst surface, and •OH dominated the degradation of 17β-E2 in VOX-CNT/PDS system. CO, defective sites and vanadium oxides on the surface of VOX-CNT contributed to the generation of activate species. Oxidizer dosage, catalyst dosage, water-soil ratio and soil properties would affect the degradation of 17β-E2. The ecotoxicological impact on soil caused by VOX-CNT/PDS was acceptable, and would be weakened with time. Additionally, a rapid decrease in the concentration of 17β-E2 and the promotion of maize growth were observed with VOX-CNT/PDS in situ pilot-scale remediation. Those results reveal that VOX-CNT/PDS is a potential technology to remove excessive steroid hormone from soil around large-scale livestock and poultry farms.

Improvement in electrical characteristics by surface modification of multi-wall carbon nanotube based buckypaper for de-icing application

Icing hazards often cause severe mobility concerns, safety risks, and even accidents in modern industries. Various ice mitigation strategies have been employed. Electro-thermal heating approach is a popular measure for ice protection, in which heat is generated electrically by internal components and then transferred to the outer surface for anti-icing and de-icing operation. Given the increasing usage of composites in aircraft structures, self-heating fibre reinforced polymer composite has been studied as an ice protection solution for the new generation aircraft. The present work focuses on improving electrical characteristics of carbon nanotube (CNT) based buckypaper (via surface functionalization) and the heating performance with an ice-phobic resin. The results indicated that surface functionalization of multi-wall carbon nanotubes (MWCNTs) was effective in obtaining MWCNT buckypaper (CNP) with improved electrical conductivity. The de-icing test confirmed the electro-thermal heating performance of the CNP based composite in a climate chamber at −20°C. The utilisation of surface modified MWCNTs in self-heating composites could be a promising strategy for maintaining lightweight and efficiency for electro-thermal systems to mitigate icing hazards.

Combined Atomic and Molecular Layer Deposition Surface Modification of Carbon Nanotubes for CNT–Epoxy Polymer Composites

Optimizing the interactions between the matrix and reinforcement components is key to attaining high-performance composite materials. Yet, balancing the reinforcing–matrix phase interactions for synthetic composites remains a great challenge. Here, a combined methodology using molecular and atomic layer deposition (M/ALD) is demonstrated for tailoring carbon nanotube (CNT) interfacial interactions, yielding high-performance-reinforced polymer composites. CNT mats are used as a model system to systematically study the molecular details as they do not involve powder processing and other aspects which obscure the understanding of molecular level effects. Noncovalent attachment of the M/ALD layer at the interface allows good wetting of the CNTs, provides an effective means for stress dissipation without compromising the CNTs’ Csp2–Csp2 network which remains intact, while introducing amine functionalities to facilitate the cross-linking polymer matrix (epoxy). M/ALD-modified CNT mat–epoxy composites showed an increase in the maximal tensile strength and toughness of up to 32 and 247%, respectively. These findings may pave the way to systematically develop high CNT loading composites as well as other nano-reinforced composite systems showing both high strength and toughness as well as numerous other desirable properties related to nanomaterial composites in general.

CeO2 modified carbon nanotube electrified membrane for the removal of antibiotics

Electrified carbon nanotube membranes (ECM) are used as electroactive porous materials for the degradation of micropollutants. It integrated design of both electrochemical processes and filtration functions. In this study, CeO2 modified carbon nanotube electrified membrane (CeO2@CNT membrane) was prepared and activate NaClO towards degradation of antibiotics. As CeO2 with face-centered cubic (Fcc) fluorite structure was loaded onto the CNT sidewalls, the CeO2@CNT membrane showed a higher over potential and a smaller equivalent polarization resistance compared to ECM. More reactive oxygen species (ROS) and reactive chlorine species (RCS) were generated by CeO2@CNT membrane due to faster electron transfer at the solid-liquid interface. Thus, the removal efficiencies of DCF, SMX, CIP, TC and CBZ were more than 91.2%, 91.3%, 94.4%, 99.3% and 89.4% by the CeO2@CNT membrane with NaClO, respetively. And the apparent reaction rate constant (k) of the CeO2@CNT membrane was 2.9 times of that of ECM. The selective capping experiments and density functional theory (DFT) calculation showed that the oxygen vacancies of CeO2 contributed to the generation of ‧OH, and the generation of ClO‧ and ‧O2− would mainly occur on Lewis acid sites of CeO2. In addition, the CeO2@CNT membrane showed a reasonable stability to treat actual water samples and reduced disinfection byproducts (DBPs) formation, suggesting that it can potentially be combined with the conventional chlorine disinfection to degrade antibiotics in water.

Environment-friendly bio-based controlled-release phosphate fertilizer with waste kitchen oil as coating material: Preparation, characterization, and mechanisms

Recently, Bio-based polyurethane controlled-release fertilizers (BPCF) have been developed rapidly owing to their environmental friendliness, renewability, and low cost. However, the unsatisfying controlled release prohibits their large-scale direct application in agricultural production. Here, we prepared bio-based controlled-release phosphate (P) fertilizers using harmful waste kitchen oils (WKO) as coating materials. The membrane shell surface was modified with multi-walled carbon nanotubes (CNT), and superhydrophobic controlled-release phosphorus fertilizers (SCRF) were obtained. After CNT modification, the controlled release period of SCRF was greatly improved. Phosphorus released period of SCRF reached over 67 d while that of BPCF was merely ∼49 d. Additionally, the surface energy, cracks, roughness, microstructure, cross-linking degree, etc., of the membrane shells were measured. The results showed that CNT greatly improved the hydrophobic properties of the membrane shells. The findings indicated the application of modified WKO with great agricultural value in preparing environment-friendly BPCFs.

Shielding-Sensing Integrated Multilayer PET–Carbon Nanotube Composites for 5G Applications

We designed a shielding–sensing integrated multilayer composite based on PET (poly(ethylene terephthalate)) and carbon nanotubes using UV laser scribing and electroless plating. APTES ((3-aminopropyl)triethoxysilane)-modified carbon nanotubes and the mixture of carbon nanotubes and silica gel were used as the active and shielding layer in the composite, respectively. The electrochemical performance and electromagnetic shielding effectiveness (SE) were investigated to assess the sensing and shielding properties of the composite. Under optimized conditions, the sensor achieved a sensitivity of 6699.0 μA mM–1 cm–2 with a linear range (LR) of 1.0–5 mM at high concentrations toward glucose oxidation. In contrast, a sensitivity of 7140.0 μA mM–1 cm–2 in the linear range of 10–60 μM was displayed for low concentrations. Simultaneously, the composite exhibited a SE value up to 43.64 dB between 30 and 6000 MHz. To explore the protective effect of the designed composite, the electric field distribution was calculated through finite difference time domain (FDTD) simulations. Additionally, tensile tests were conducted to validate the excellent serviceability and stretchability of the composite. The as-prepared multilayer composite with integrated shielding–sensing function holds great potential in the wearable physiology monitoring and electromagnetic interference shielding applications for 5G electronic products.

ВПЛИВ НЕКОВАЛЕНТНОЇ МОДИФІКАЦІЇ ВУГЛЕЦЕВИХ НАНОТРУБОК ЗА ДОПОМОГОЮ ПОЛІЕТИЛЕНГЛІКОЛЮ НА ЇХ РОЗПОДІЛ У ПОЛІМЕРНІЙ МАТРИЦІ

In polymer nanocomposites filled with carbon nanotubes, it is very difficult to ensure uniform distribution of nanotubes in the polymer matrix, as well as the stability of this dispersion over time. Therefore, in such systems, over time, due to the strong van der Waals forces of attraction between individual nanotubes, aggregation of filler particles takes place. It leads to a transition from the nano to the micro level of their structural organization. This transition significantly affects the complex of functional properties of polymer nanocomposites filled with carbon nanotubes (CNTs). Therefore, the development of new approaches to the stabilization of nanoparticles in order to prevent their aggregation to create nanocomposite materials with improved functional characteristics is an actual task. The work is devoted to the study of the influence of non-covalent modification of carbon nanotubes on the degree of their distribution in the polymer matrix of polyethylene glycol. The peculiarities of CNT distribution of two types were studied: unmodified and non-covalently modified nanotubes. It was found that unmodified CNTs contained hydroxyl, carboxyl and lactone groups on the surface. The presence of these groups on the surface of CNTs allowed for their noncovalent modification. The analysis of microscopic images revealed that the modified CNTs are more evenly distributed in the polymer matrix than the unmodified nanotubes, which can be explained by the different nature of the interaction between the polymer matrix and the CNT. It is shown that for systems containing modified CNTs, a higher value of fractal dimension is observed, which indicates the formation of more fluffy aggregates with CNTs, while unmodified CNTs tend to form denser aggregates. Modification of CNTs with PEG is a promising method to increase the degree of distribution of nanotubes in the polymer matrix, which will significantly improve the properties of such nanocomposite materials.

Application of Nanocomposite Energy Storage Materials in Green Building Design.

In order to solve the problem of the application of composite phase change heat storage materials in building energy conservation, the author proposes the application of nanocomposite energy storage materials in green building design. Modified carbon nanotubes were prepared by mixed acid oxidation and ball milling, and composited with stearic acid to prepare phase change heat storage materials. Modified carbon nanotubes were prepared by mixed acid oxidation and ball milling and composited with stearic acid to prepare phase change heat storage materials. Experimental results show that acidified carbon nanotubes have a hindering effect on the thermal diffusion of stearic acid molecular segments so that the thermal conductivity of carbon nanotubes added with a mass fraction of 1% is only 1.3 times higher than that of pure stearic acid. Conclusion. Nanocomposite energy storage materials have excellent application prospects in green building design.

Research on Modified Carbon Nanotubes in Wastewater Treatment

The application of modified carbon nanotubes (MCNTs) in the field of wastewater treatment has received much attention in recent years. To better understand the research progress and trends of MCNTs in wastewater treatment, this paper presents a bibliometric analysis of the scientific literature on the application of MCNTs in wastewater, highlight how it has evolved over the years, and identify the sectors for which the study could be beneficial. The CiteSpace software was used to perform the analysis of the data in which specific maps were used to represent the network of the relationships among countries, journals, organizations, authors, and keywords related to the investigated topic and subtopics. The results show that in the time frame of the study, most attention has been focused on the functional modification of carbon nanotubes, the study of their application in water treatment, and the study of the patterns and mechanisms of pollutant removal. The recycling of MCNTs and their environmental risks have not been sufficiently studied. In conclusion, the recycling and regeneration methods of MCNTs, as well as the potential ecological, environmental and health risks will be the focus of future research and more research should be invested.

Improved Electrical Conductivity and Strength of α-Al-Carbon Nanotubes Blended with Silver Nanoparticles Composites

An attempt has been made to develop a new enhanced electrical conductor nanocomposites using green synthesis silver nanoparticles (GAgNPs) modified carbon nanotubes (CNTs) reinforced aluminum nanocomposites. High-intensity ball milling and spark plasma sintering (SPS) were used to produce the composites. The nanocomposite' microstructure, strength, model, and electrical conductivity were all determined. 2%GAg.NPs in Al-4-percent CNTs helps to refine the grain structure of the Al-4-percent CNTs. More dislocation density was generated by the creation of sub-grain in the Al-4 percent CNTs+2 percent GAgNPs composite. Tensile strength and electrical conductivity were increased by 82.14 and 106.88% using Al-4-percent CNTs +2%GAg.NPs nanocomposite. The ductility mode of fracture associated with the tiny sub-grain produced at the surface was greatly improved when 2% GAgNPs were added to Al-4% CNTs. It was established that the GAgNPS can been used to coat CNTs enhance the strength and electrical conductivity of Al-4 percent CNTs nanocomposites.

Promoting desalination performance of carbon nanotubes through cationic and anionic surface modifications

Carbon nanotubes (CNTs) hold great promise for the design of novel desalination devices. However, the performance of pristine CNTs is very limited because of the trade-off between ion selectivity and water permeability, and thus the surface modification could be an effective strategy to promote the performance. Although great effort has been made on the CNT modifications in both experiments and simulations, most of the previous studies focus on the CNT entrance or exterior modification, while the interior modification remains poorly understood. In this work, a series of molecular dynamics simulations demonstrate that the modification of CNT interior with charged residues of either COO– or NH3+ can significantly promote the desalination performance. Specifically, even under a high pressure, the ion rejections can attain a high level of around 90 % that can reach drinkable standards at certain charge densities. The two systems exhibit dynamical bifurcations because of the discrepancy in the ion-residue interaction, where the water flux and ion rejection for NH3+ system are always greater. Consequently, the inner surface modification of CNTs could open a new avenue to break the trade-off between ion selectivity and water permeability, which should have great implications for the design of novel desalination devices.