Advancing CEA quantification: Designing a sensitive electrochemical immunosenor using MWCNT/Ni(OH)2 nanocomposite

An ultra-sensitive immunosensor was designed for the accurate determination of Carcinoembryonic Antigen (CEA). To enhance the performance of immunosensor, an MWCNT/Ni(OH)2 nanocomposite was utilized as the electrochemical interface and modifier of the electrode surface. The simple preparation procedures for MWCNT/Ni(OH)2 composite were provided. Its characteristics and properties were investigated by HRTEM, FESEM, XRD, and FTIR techniques. Leveraging the unique electrochemical characteristics shown by the MWCNT/Ni(OH)2 nanocomposite and its correlation with CEA, high accuracy in CEA detection was achieved. Experimental findings provide evidence that the proposed immunosensor has the ability to detect CEA in laboratory samples. This research contributes towards achieving precise and rapid CEA detection in cancer diagnosis and prognosis. Across a wide concentration range of CEA, the designed immunosensor demonstrated a linear response from 0.0001 ng/mL to 2 ng/mL, and its limit of detection (LOD) was just 0.076 pg/mL. To evaluate the practical applicability of the electrochemical immunosensor, blood serum samples were examined, revealing the immunosensor's remarkable specificity and longevity. Its high accuracy and stability make it a valuable tool in clinical settings and biomedical research, paving the way for improved cancer management and patient outcomes.

Improved Performance of QDSSCs Can Be Achieved by Constructing a Transparent Anatase TiO2@MWCNT Photoanode Based on the Bionic Mountain Lotus

In this research, the structural characteristics of the mountain holly leaf were emulated. It was observed that after the initially uneven surface of the petals is filled with infiltrated water, it exhibits a distinctive transparent beauty after rainfall. Furthermore, the presence of leaf veins enhances the structural strength of the petals and facilitates nutrient transport. Inspired by previous studies on double-layer spin-coated films, we further developed and designed the TA TiO2@MWCNT photocathode thin film. This innovative film incorporates multiwalled carbon nanotubes (MWCNT) into a previously established TA TiO2 photocathode thin film. The inclusion of MWCNT results in the formation of a three-dimensional highway structure, where MWCNT intertwines within the TA TiO2 film. Under the operational state of immersion in the electrolyte, it maintains a level of transparency similar to that of the TA TiO2 photoanode thin film. The high-temperature sintering process results in the oxidation and depletion of MWCNTs on the surface of the film, leaving behind uniformly dispersed concave defects, thereby greatly enhancing the specific surface area. The findings demonstrate that the optoelectrode of high transparency and high specific surface area, TA TiO2@MWCNT, comprehensively enhances the performance of the solar cells. The transparent QDSSC surpasses its counterparts for the first time, achieving a power conversion efficiency (PCE) of 6.335%. This sets the stage for new materials and innovative approaches in the field of solar cells and other titanium dioxide film-related areas.

Intricate Ionic Behaviors in High-Performance Self-Powered Hydrothermal Chemical Generator Using Water and Iron (III) Gate

Utilizing the ionic flux to generate voltage output has been confirmed as an effective way to meet the requirements of clean energy sources. Different from ionic thermoelectric (i-TE) and hydrovoltaic devices, a new hydrothermal chemical generator is designed by amorphous FeCl3 particles dispersing in MWCNT and unique ferric chloride or water gate. In the presence of gate, the special ion behaviors enable the cell to present a constant voltage of 0.60 V lasting for over 96 h without temperature difference. Combining the differences of cation concentration, humidity and temperature between the right and left side of sample, the maximum short-circuit current and power output can be obtained to 168.46 µA and 28.11 µW, respectively. The generator also can utilize the low-grade heat to produce electricity wherein Seebeck coefficient is 6.79 mV K-1 . The emerged hydrothermal chemical generator offers a novel approach to utilize the low-grade heat, water and salt solution resources, which provides a simple, sustainable and low-cost strategy to realize energy supply.

Hybrid Organosulfur Network/MWCNT Composite Cathodes for Li-S Batteries

Lithium-sulfur (Li-S) batteries hold a promising position as candidates for next-generation high-energy storage systems. Here, we combine inverse vulcanization of sulfur with multiwalled carbon nanotubes (MWCNTs) to increase the conductivity of cathode materials for Li-S batteries. The mixing process of inversely vulcanized sulfur copolymer networks with MWCNTs is aided by shear in a two-roll mill to take advantage of the soft nature of the copolymer. The high-throughput mixing method demands a source of conductive carbon that can be intimately mixed with the S copolymer, rendering MWCNTs an excellent choice for this purpose. The resulting sulfur copolymer network-MWCNTs composites were thoroughly characterized in terms of structure, chemical composition, thermal, and electronic transport properties, and finally evaluated by electrochemical benchmarking. These promising hybrids yielded electrodes with high sulfur content and demonstrate stable electrochemical performance exhibiting a specific capacity of ca. 550 mAh·gsulfur-1 (380 mAh·gelectrode-1) even after 500 charge-discharge cycles at specific current of 167 mA·g-1 (corresponds to 0.1C discharge rate), and thus are superior to melt-infiltrated reference samples.

Non-toxic flexible screen-printed MWCNT-based electrodes for non-invasive biomedical applications

Here, a non-toxic, flexible, low-cost, and disposable multiwalled carbon nanotube (MWCNT)-based screen-printed electrode (SPE) was developed for non-invasive health monitoring applications. A novel MWCNT-based conductive paste formulation was prepared and optimized for printing SPEs using a computer numerical control (CNC)-made stencil. The electrodes were electrochemically characterized and subjected to physical stress to investigate their mechanical durability in extreme situations such as heavy exercise. The reproducibility of the fabrication approach and the stability of the electrodes were also demonstrated. The electrochemical performance of the electrodes was tested with first dopamine (DA) and then glucose. The SPE displayed a linear response in the DA concentration range of 5-500 μM with a limit-of-detection (LOD) of 0.87 μM. Detection of glucose was carried out based on electrochemical-enzymatic redox cycling in artificial sweat; wherein the flexible SPE-based biosensor exhibited a linear response, particularly up to 1 mM with an LOD of 31.7 μM. It is likely that the high sensitivity was achieved due to the large surface-to-volume ratio of MWCNTs and micro/nanoporous network morphology of the electrode surface which was observed in scanning electron microscopy (SEM). Cytotoxicity tests confirmed that the flexible MWCNT-SPEs are non-toxic and therefore safe for non-invasive health monitoring. As a result, the electrodes displayed excellent electrochemical behavior and are expected to contribute to wearable sensor technology due to features such as high stability, sensitivity, flexibility, and non-toxicity.

Amorphous, Carbonated Calcium Phosphate and Biopolymer-Composite-Coated Si3N4/MWCNTs as Potential Novel Implant Materials

A biodegradable amorphous carbonated calcium phosphate (caCP)-incorporated polycaprolactone (PCL) composite layer was successfully deposited by a spin coater. In this specific coating, the PCL acts as a bioadhesive, since it provides a better adherence of the coatings to the substrate compared to powder coatings. The caCP-PCL coatings were deposited and formed thin layers on the surface of a Si3N4-3 wt% MWCNT (multiwalled carbon nanotube) substrate, which is an emerging type of implant material in the biomedical field. The composite coatings were examined regarding their morphology, structure and biological performance. The biocompatibility of the samples was tested in vitro with MC3T3-E1 preosteoblast cells. Owing to the caCP-PCL thin layer, the cell viability values were considerably increased compared to the substrate material. The ALP and LDH tests showed numerous living cells on the investrigated coatings. The morphology of the MC3T3-E1 cells was examined by fluorescent staining (calcein and DAPI) and scanning electron microscopy, both of which revealed a well-spread, adhered and confluent monolayer of cells. All performed biocompatibility tests were positive and indicated the applicability of the deposited thin composite layers as possible candidates for orthopaedic implants for an extended period.

Highly Efficient Ru-Based Catalysts for Lactic Acid Conversion to Alanine

The primary objective of this research was to develop efficient solid catalysts that can directly convert the lactic acid (LA) obtained from lignocellulosic biomass into alanine (AL) through a reductive amination process. To achieve this, various catalysts based on ruthenium were synthesized using different carriers such as multi-walled carbon nanotubes (MWCNTs), beta-zeolite, and magnetic nanoparticles (MNPs). Among these catalysts, Ru/MNP demonstrated a remarkable yield of 74.0% for alanine at a temperature of 200 °C. This yield was found to be superior not only to the Ru/CNT (55.7%) and Ru/BEA (6.6%) catalysts but also to most of the previously reported catalysts. The characterization of the catalysts and their catalytic results revealed that metallic ruthenium nanoparticles, which were highly dispersed on the external surface of the magnetic carrier, significantly enhanced the catalyst's ability for dehydrogenation. Additionally, the -NH2 basic sites on the catalyst further facilitated the formation of alanine by promoting the adsorption of acidic reactants. Furthermore, the catalyst could be easily separated using an external magnetic field and exhibited the potential for multiple reuses without any significant loss in its catalytic performance. These practical advantages further enhance its appeal for applications in the reductive amination of lactic acid to alanine.

Chitosan modified multi-walled carbon nanotubes and arginine aerogel for enhanced carbon capture

Global warming is emerging as a significant issue because of increasing CO2 levels in the atmosphere due to urbanization, industrialization, and fossil-fuel usage. Therefore, reducing atmospheric CO2 levels using new materials with high carbon capture capacity and efficient CO2 capture technologies is essential. Herein, we propose a hybrid chitosan (CS) aerogel containing multi-walled carbon nanotubes (MWCNTs) and an arginine (Arg) aerogel (CSCNTArg aerogel) for efficient carbon capture. This aerogel was successfully synthesized using a cross-linker reagent via step-freeze drying method. Fourier-transform infrared spectroscopy and X-ray diffraction analyses confirmed the successful grafting of CS, MWCNTs, and Arg onto the CSCNTArg aerogel. The thermogravimetric analysis (TGA) confirmed good thermal stability up to 500 °C of the as-developed aerogel. Field-emission scanning electron microscopy showed that the surface morphology of the CSCNTArg aerogel differed from that of CS, Arg, and MWCNTs with pores on their surfaces. N2 and CO2 adsorption-desorption studies on the CSCNTArg aerogel were performed using the Brunauer-Emmett-Teller method and TGA, respectively. The CSCNTArg aerogel showed a high adsorption capacity of approximately 5.00 mmol g-1 at 35 °C. Therefore, this new material may be useful for facilitating high-efficiency CO2 adsorption to reduce atmospheric carbon footprint.

Enhanced O2/N2 separation by QuaternizedMatrimid/Multiwalled carbon nanotube mixed-matrix membrane

The air separation (O2/N2) based on polymeric membranes is critical because it is more energy efficient than traditional methods. Dense polymeric membranes are now the main stay of industrial processes that generate oxygen and nitrogen enriched gas. Though, regular polymeric membranes often fall short of selective pressure demands because O2 and N2 gases have such comparable equivalent diameters. While polymer composites have their benefits, nanocomposite (NCs) allows for the production of high-performance barriers. Utilising Matrimid® 5218 (Matrimid) as the base framework and multiwall carbon nanotube (MWCNT) as the filler, a novel NCs for O2/N2 separation was developed. Both matrimid and MWCNTs were chemically modified quaternization and functionalizing the MWCNTs. The membranes were casted using solution casting with a combination of quaternized matrimid and functionalized multi-walled carbon nanotubes (f-MWCNT). When f-MWCNT was added to quaternized matrimid, it created interfacial compatibility, which increased O2/N2 selectivity and permeability by 65 % and 35 %, respectively. In the current study, increasing O2 diffusivity and O2/N2 solubility selectivity resulted in improved performance, this paves a way for manufacturing innovation.

Coating of Felt Fibers with Carbon Nanotubes and PEDOT with Different Counterions: Temperature and Electrical Field Effects

The use of wearable devices has promoted new ways of integrating these devices, one of which is through the development of smart textiles. Smart textiles must possess the mechanical and electrical properties necessary for their functionality. This study explores the impact of polymer-felt microstructure variations on their morphology, electrical, and mechanical properties. The application of thermal treatment, along with an electric field, leads to a substantial structural reorganization of the molecular chains within pristine felt. This results in a system of nanofibrils coated with MWCNT-PEDOT, characterized by highly ordered counterions that facilitate the flow of charge carriers. Both temperature and an electric field induce reversible microstructural changes in pristine felt and irreversible changes in coated felt samples. Furthermore, electropolymerization of PEDOT significantly enhances electrical conductivity, with PEDOT:BTFMSI-coated fabric exhibiting the highest conductivity.

Electrochemical sensor based on carbon nanotube decorated with manganese oxide nanoparticles for naphthalene determination

In this work, an electrochemical sensor was developed for the determination of naphthalene (NaP) in well water samples, based on a glass carbon electrode (GCE) modified as a nanocomposite of manganese oxides (MnOx) and COOH-functionalized multi-walled carbon nanotubes (MWCNT). The synthesis of MnOx nanoparticles was performed by the sol-gel method. The nanocomposite was obtained by mixing MnOx and MWCNT with the aid of ultrasound, followed by stirring for 24 h. Surface modification facilitated the electron transfer process through the MnOx/MWCNT/GCE composite, which was used as an electrochemical sensor. The sensor and its material were characterized by cyclic voltammetry (CV), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Important parameters influencing electrochemical sensor performance (pH, composite ratios) were investigated and optimized. The MnOx/MWCNT/GCE sensor showed a wide linear range of 2.0-16.0 μM, a detection limit of 0.5 μM and a quantification limit of 1.8 μM, in addition to satisfactory repeatability (RSD of 7.8%) and stability (900 s) in the determination of NaP. The determination of NaP in a sample of water from a gas station well using the proposed sensor showed results with recovery between 98.1 and 103.3%. The results obtained suggest that the MnOx/MWCNT/GCE electrode has great potential for application in the detection of NaP in well water.

Exposure of Rats to Multi-Walled Carbon Nanotubes: Correlation of Inhalation Exposure to Lung Burden, Bronchoalveolar Lavage Fluid Findings, and Lung Morphology

To evaluate lung toxicity due to inhalation of multi-walled carbon nanotubes (MWCNTs) in rats, we developed a unique MWCNT aerosol generator based on dry aerosolization using the aerodynamic cyclone principle. Rats were exposed to MWNT-7 (also known as Mutsui-7 and MWCNT-7) aerosolized using this device. We report here an analysis of previously published data and additional unpublished data obtained in 1-day, 2-week, 13-week, and 2-year inhalation exposure studies. In one-day studies, it was found that approximately 50% of the deposited MWNT-7 fibers were cleared the day after the end of exposure, but that clearance of the remaining fibers was markedly reduced. This is in agreement with the premise that the rapidly cleared fibers were deposited in the ciliated airways while the slowly cleared fibers were deposited beyond the ciliated airways in the respiratory zone. Macrophage clearance of MWNT-7 fibers from the alveoli was limited. Instead of macrophage clearance from the alveoli, containment of MWNT-7 fibers within induced granulomatous lesions was observed. The earliest changes indicative of pulmonary toxicity were seen in the bronchoalveolar lavage fluid. Macrophage-associated inflammation persisted from the one-day exposure to MWNT-7 to the end of the two-year exposure period. Correlation of lung tumor development with MWNT-7 lung burden required incorporating the concept of area under the curve for the duration of the study; the development of lung tumors induced by MWNT-7 correlated with lung burden and the duration of MWNT-7 residence in the lung.

Self-Assembly of Multiwalled Carbon Nanotubes on a Silicone Rubber Foam Skeleton for Durable Piezoresistive Sensors

Conductive nanomaterial/flexible polymer composite foams are of great interest in the field of flexible and wearable piezoresistive pressure sensors. However, the existing composite foam sensors are faced with stability issues from conductive nanomaterials, which tends to decrease their long-term durability. Herein, we developed a solvent evaporation-induced self-assembly strategy, which could significantly improve the stability of multiwalled carbon nanotubes (MWCNTs) on a silicone rubber foam skeleton. The process for self-assembly of MWCNTs was straightforward. Aqueous MWCNT dispersion droplets were first hierarchically enclosed in silicone rubber via water-in-oil (W/O) Pickering high internal phase emulsions (HIPEs). Then, the high pressure generated by fast evaporation of the solvent from the droplets could break the thinnest pore walls to form interconnected pores. As a result, very dense and firm MWCNT layers were self-assembled on the pore wall surface. Due to the excellent stability of MWCNTs and tetramodal interconnected porosity, our MWCNTs/silicone rubber composite foam showed the following "super" properties: low density of 0.26 g/mL, high porosity of 76%, and excellent mechanical strength (the maximum stress loss of 8.3% at 80% strain after 100 compression cycles). In addition, excellent piezoresistive performance, including superior discernibility for different amplitudes of compressive strain (up to 80%), rapid response time (150 ms), and high sensitivity (gauge factor of 1.44), was demonstrated for such foams, together with prominent durability (39,000 compression cycles at 60% strain in air) and excellent stability of resistance response in water and organic solvents (5000 compression cycles at 30% strain in water and ethanol). Regarding its application, a wearable piezoresistive sensor, which was assembled from the as-prepared conductive silicone rubber composite foam, could capture various movements from tiptoeing and finger bending to small deformations resulting from human pulse.

Highly Stable MWCNT@NVP Composite as a Cathode Material for Na-Ion Batteries

A 3D framework with Nasicon structured polyanionic Na₃V₂(PO₄)₃ (NVP) has been emphasized as a leading cathode material for sodium-ion batteries (SIBs) due to its high working voltage plateau, structural stability, and good rate performance. Herein, pristine NVP and MWCNT@NVP composite synthesized via a facile solid-state method are examined and compared as cathode materials for Na-ion batteries. The morphological study confirms the uniform distribution of MWCNTs in the pristine NVP structure. Impedance spectroscopy clearly confirms more diffusion of Na ions for the MWCNT@NVP composite as compared to pristine NVP, considering its diffusion coefficient which directly implies on an increase in specific capacity. MWCNT@NVP (FNV-2) showed specific discharge capacity 110 mAhg-1 at 0.1C current rate which is almost stable at higher current rates with marginal fading. However, the pristine NVP shows capacity loss at a higher current rate. It is noteworthy that the MWCNT@NVP composite shows stable performance with marginal specific capacity fading (1%) compared to pristine (15%). This is because of the mechanical integrity and stability afforded to the composite by the intertwined MWCNT framework in the MWCNT@NVP composite matrix against electrode degradation during the electrochemical reaction. More significantly, even at a higher current rate, that is, at 10 C, the composite recorded a very stable and excellent Columbic efficiency of 97% with a reversible specific capacity of 94 mAhg^-1 after 2000 cycles. An enhanced electrochemical performance, that is, rate capability and cycling stability, demonstrates the high potential of the MWCNT@NVP composite for Na-ion storage. Moreover, a sodium-ion full cell with hard carbon demonstrated a reversible capacity of 103 mAhg^-1 at C/20 current rate, which clearly demonstrates that MWCNT@NVP is a promising cathode material for sodium-ion batteries.

Anticancer Activity of Au/CNT Nanocomposite Fabricated by Nanosecond Pulsed Laser Ablation Method on Colon and Cervical Cancer

Gold nanoparticles (AuNPs) and carbon nanotubes (CNTs) are increasingly being investigated for cancer management due to their physicochemical properties, low toxicity, and biocompatibility. This study used an eco-friendly technique (laser synthesis) to fabricate AuNP and Au/CNT nanocomposites. AuNPs, Au/CNTs, and CNTs were tested as potential cancer nanotherapeutics on colorectal carcinoma cells (HCT-116) and cervical cancer cells (HeLa) using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. In addition, the non-cancer embryonic kidney cells HEK-293 were taken as a control in the study. The cell viability assay demonstrated a significant reduction in cancer cell population post 48 h treatments of AuNPs, and Au/CNTs. The average cell viabilities of AuNPs, Au/CNTs, and CNTs for HCT-116 cells were 50.62%, 65.88%, 93.55%, and for HeLa cells, the cell viabilities were 50.88%, 66.51%, 91.73%. The cell viabilities for HEK-293 were 50.44%, 65.80%, 93.20%. Both AuNPs and Au/CNTs showed higher cell toxicity and cell death compared with CNT nanomaterials. The treatment of AuNPs and Au/CNTs showed strong inhibitory action on HCT-116 and HeLa cells. However, the treatment of CNTs did not significantly decrease HCT-116 and HeLa cells, and there was only a minor decrease. The treatment of AuNPs, and Au/CNTs, on normal HEK-293 cells also showed a significant decrease in cell viability, but the treatment of CNTs did not produce a significant decrease in the HEK-293 cells. This study shows that a simplified synthesis technique like laser synthesis for the preparation of high-purity nanomaterials has good efficacy for possible future cancer therapy with minimal toxicity.

Optimization of Filler Compositions of Electrically Conductive Polypropylene Composites for the Manufacturing of Bipolar Plates

In this research, polypropylene (PP)-graphite composites were prepared using the melt mixing technique in a twin-screw extruder. Graphite, multi-walled carbon nanotubes (MWCNT), carbon black (CB), and expanded graphite (EG) were added to the PP in binary, ternary, and quaternary formations. The graphite was used as a primary filler, and MWCNT, CB, and EG were added to the PP-graphite composites as secondary fillers at different compositions. The secondary filler compositions were considered the control input factors of the optimization study. A full factorial design of the L-27 Orthogonal Array (OA) was used as a Design of Experiment (DOE). The through-plane electrical conductivity and flexural strength were considered the output responses. The experimental data were interpreted via Analysis of Variance (ANOVA) to evaluate the significance of each secondary filler. Furthermore, statistical modeling was performed using response surface methodology (RSM) to predict the properties of the composites as a function of filler composition. The empirical model for the filler formulation demonstrated an average accuracy of 83.9% and 93.4% for predicting the values of electrical conductivity and flexural strength, respectively. This comprehensive experimental study offers potential guidelines for producing electrically conductive thermoplastic composites for the manufacturing of bipolar fuel cell plates.

Development of MWCNT/Magnetite Flexible Triboelectric Sensors by Magnetic Patterning

The fabrication of low-electrical-percolation-threshold polymer composites aims to reduce the weight fraction of the conductive nanomaterial necessary to achieve a given level of electrical resistivity of the composite. The present work aimed at preparing composites based on multiwalled carbon nanotubes (MWCNTs) and magnetite particles in a polyurethane (PU) matrix to study the effect on the electrical resistance of electrodes produced under magnetic fields. Composites with 1 wt.% of MWCNT, 1 wt.% of magnetite and combinations of both were prepared and analysed. The hybrid composites combined MWCNTs and magnetite at the weight ratios of 1:1; 1:1/6; 1:1/12; and 1:1/24. The results showed that MWCNTs were responsible for the electrical conductivity of the composites since the composites with 1 wt.% magnetite were non-conductive. Combining magnetite particles with MWCNTs reduces the electrical resistance of the composite. SQUID analysis showed that MWCNTs simultaneously exhibit ferromagnetism and diamagnetism, ferromagnetism being dominant at lower magnetic fields and diamagnetism being dominant at higher fields. Conversely, magnetite particles present a ferromagnetic response much stronger than MWCNTs. Finally, optical microscopy (OM) and X-ray micro computed tomography (micro CT) identified the interaction between particles and their location inside the composite. In conclusion, the combination of magnetite and MWCNTs in a polymer composite allows for the control of the location of these particles using an external magnetic field, decreasing the electrical resistance of the electrodes produced. By adding 1 wt.% of magnetite to 1 wt.% of MWCNT (1:1), the electric resistance of the composites decreased from 9 × 10⁴ to 5 × 10³ Ω. This approach significantly improved the reproducibility of the electrode's fabrication process, enabling the development of a triboelectric sensor using a polyurethane (PU) composite and silicone rubber (SR). Finally, the method's bearing was demonstrated by developing an automated robotic soft grip with tendon-driven actuation controlled by the triboelectric sensor. The results indicate that magnetic patterning is a versatile and low-cost approach to manufacturing sensors for soft robotics.

A new non-enzymatic biosensor for the determination of bisphenol-A

In this study, a new non-enzymatic carbon paste biosensor was developed for the determination of Bisphenol-A (BPA) based on Multiwalled Carbon Nanotube (MWCNT) modified Myoglobin (Mb). The measurement principle of the biosensor was developed based on the inhibition effect of BPA on the heme group of myoglobin in the presence of hydrogen peroxide. With the designed biosensor, measurements were taken in the potential range of (-0.15 V & +0.65 V) using the differential pulse voltammetry (DPV) method in the medium containing K₄[Fe(CN)₆]. The linear range for BPA was determined to be 100-1000 µM. Response time was calculated as 16 s. The limit of detection was set at 89 μM. As a result, it has been proven that MWCNT modified myoglobin based biosensor is an alternative method that can be used for BPA determination, giving very sensitive and fast results.

Design and development of keratin/chitosan/glucosamine sulfate composite loaded MWCNT intended for osteoarthritis drug delivery

Osteoarthritis (OA) is an inflammatory disease that affects the cartilage and tissues around the joints, which results in excessive pain and stiffness. One of the most critical challenges for improving the therapeutic effect in osteoarthritis treatments is the current drug design utilizing functional polymers. Indeed, there is a need to design and develop novel therapeutic drugs for positive outcomes. In this view, glucosamine sulfate is a drug used to manage osteoarthritis (OA) because of its potential therapeutic effects on cartilage and ability to inhibit disease progression. This research aims to develop a Keratin/Chitosan/Glucosamine sulfate composite loaded functionalized multi-walled carbon nanotubes (MWCNT) as a potential carrier for the treatment of osteoarthritis. The nanocomposite was developed using various ratios of Keratin, Chitosan, Glucosamine sulfate, and MWCNT. Molecular docking analysis has been performed with (D-Glucosamine) and targeted proteins (PDB ID: 1HJV, 1ALU) to determine the binding affinity and interactions. Field Emission Scanning Electron Microscope (FESEM) study showed that the composite (KRT/CS/GLS) incorporated on the surface of functionalized multi-walled carbon nanotubes effectively. Fourier Transform Infrared spectroscopy (FTIR) analysis showed the presence of keratin, chitosan, and glucosamine sulfate in the nanocomposite and remained intact. X-ray diffraction (XRD) analysis indicated that the nature of the composite in MWCNT transformed from a crystalline to an amorphous state. Thermogravimetric (TGA) analysis revealed that the nanocomposite has a high thermal decomposition temperature of 420° C. The MTT assay results showed that 83% of cell viability has remained in RAW 264.7 cells at the maximum concentration (500μg/ml) of MWCNT-GLS/KRT/CS nanocomposite. Also, molecular docking results revealed the excellent binding affinity of D-Glucosamine to each protein structure (PDB ID: 1HJV and 1ALU).

Development of in-situ electrochemical heavy metal ion sensor using integrated 1D/0D/1D hybrid by MWCNT and CQDs supported MnO2 nanomaterial

An integrated 1D/0D/1D hybrid nanomaterial was prepared from MWCNT supported carbon quantum dots @ MnO₂ nanomaterial for a sensitive and selective electrochemical heavy metal ion sensor by hydrothermal methods. The developed nanomaterials were characterized by various analytical methods such as FESEM, HRTEM, XRD, FTIR, EDX and elemental mapping study, and also its electrochemical properties of the prepared samples were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analysis. Differential pulse voltammetry (DPV) analysis has been used to investigate the quantitative detection of heavy metal ions such as cadmium and chromium on modified electrodes under optimal conditions. The in-situ electrochemical sensitivity and selectivity of the samples were determined by varying various parameters, such as the concentration of heavy metal ions, different electrolytes and electrolyte pH. The observed DPV results show that prepared MWCNT (0.05 wt%) and CQD (0.1 wt%) supported MnO₂ nanoparticles show effective detection response for chromium (IV) metal ion. In particular, 0D CQD, 1D MWCNT, and MnO₂ hybrid nanostructures produced a synergistic effect among them, resulting in strong electrochemical performance of the prepared samples against the target metal ions.

Multi-walled carbon nanotubes induce arachidonate 5-lipoxygenase expression and enhance the polarization and function of M1 macrophages in vitro

Fibrogenic carbon nanotubes (CNTs) induce the polarization of M1 and M2 macrophages in mouse lungs. Polarization of the macrophages regulates the production of proinflammatory and pro-resolving lipid mediators (LMs) to mediate acute inflammation and its resolution in a time-dependent manner. Here we examined the molecular mechanism by which multi-walled CNTs (MWCNTs, Mitsui-7) induce M1 polarization in vitro. Treatment of murine macrophages (J774A.1) with Mitsui-7 MWCNTs increased the expression of Alox5 mRNA and protein in a concentration- and time-dependent manner. The MWCNTs induced the expression of CD68 and that induction persisted for up to 3 days post-exposure. The expression and activity of inducible nitric oxide synthase, an intracellular marker of M1, were increased by MWCNTs. Consistent with M1 polarization, the MWCNTs induced the production and secretion of proinflammatory cytokines tumor necrosis factor-α and interleukin-1β, and proinflammatory LMs leukotriene B4 (LTB4) and prostaglandin E2 (PGE2). The cell-free media from MWCNT-polarized macrophages induced the migration of neutrophilic cells (differentiated from HL-60), which was blocked by Acebilustat, a specific leukotriene A4 hydrolase inhibitor, or LY239111, an LTB4 receptor antagonist, but not NS-398, a cyclooxygenase 2 inhibitor, revealing LTB4 as a major mediator of neutrophil chemotaxis from MWCNT-polarized macrophages. Knockdown of Alox5 using specific small hairpin-RNA suppressed MWCNT-induced M1 polarization, LTB4 secretion, and migration of neutrophils. Taken together, these findings demonstrate the polarization of M1 macrophages by Mitsui-7 MWCNTs in vitro and that induction of Alox5 is an important mechanism by which the MWCNTs promote proinflammatory responses by boosting M1 polarization and production of proinflammatory LMs.

Needlelike, short and thin multi-walled carbon nanotubes: comparison of effects on wild type and p53+/- rat lungs

Carbon nanotubes (CNTs) are nanomaterials presenting an occupational inhalation risk during production or handling. The International Agency for Research on Cancer classified one CNT, Mitsui-7 (MWNT-7), as 'possibly carcinogenic to humans'. In recognition of their similarities, a proposal has been submitted to the risk assessment committee of ECHA to classify all fibers with 'Fibre Paradigm' (FP)-compatible dimensions as carcinogenic. However, there is a lack of clarity surrounding the toxicity of fibers that do not fit the FP criteria. In this study, we compared the effects of the FP-compatible Mitsui-7, to those of NM-403, a CNT that is too short and thin to fit the paradigm. Female Sprague Dawley rats deficient for p53 (GMO) and wild type (WT) rats were exposed to the two CNTs (0.25 mg/rat/week) by intratracheal instillation. Animals (GMO and WT) were exposed weekly for four consecutive weeks and were sacrificed 3 days or 8 months after the last instillation. Exposure to both CNTs induced acute lung inflammation. However, persistent inflammation at 8 months was only observed in the lungs of rats exposed to NM-403. In addition to the persistent inflammation, NM-403 stimulated hyperplasic changes in rat lungs, and no adenomas or carcinomas were detected. The degree and extent of hyperplasia was significantly more pronounced in GMO rats. These results suggest that CNT not meeting the FP criteria can cause persistent inflammation and hyperplasia. Consequently, their health effects should be carefully assessed.

Exposure to multi-walled carbon nanotubes causes suppression in octopamine signal associated with transgenerational toxicity induction in C.elegans

Multi-walled carbon nanotube (MWCNT), a kind of carbon-based nanomaterials, has been extensively utilized in a variety of fields. In Caenorhabditis elegans, MWCNT exposure can result in toxicity not only at parental generation (P0-G) but also in the offspring. However, the underlying mechanisms remain still largely unknown. DAF-12, a transcriptional factor (TF), was previously found to be activated and involved in transgenerational toxicity control after MWCNT exposure. In this study, we observed that exposure to 0.1-10 μg/L MWCNTs caused the significant decrease in expression of tbh-1 encoding a tyramine beta-hydroxylase with the function to govern the octopamine synthesis, suggesting the inhibition in octopamine signal. After exposure to 0.1 μg/L MWCNT, the decrease in tbh-1 expression could be also detected in F1-G and F2-G. Moreover, in germline cells, the TF DAF-12 regulated transgenerational MWCNT toxicity by suppressing expression and function of TBH-1. Meanwhile, exposure to 0.1-10 μg/L MWCNTs induced the increase in octr-1 expression and the decrease in ser-6 expression. After exposure to 0.1 μg/L MWCNT, the increased octr-1 expression and the decreased ser-6 expression were further observed in F1-G and F2-G. Germline TBH-1 controlled transgenerational MWCNT toxicity by regulating the activity of octopamine receptors (SER-6 and OCTR-1) in offspring. Furthermore, in the offspring, SER-6 and OCTR-1 affected the induction of MWCNT toxicity by upregulating or downregulating the level of ELT-2, a GATA TF. Taken together, these findings suggested possible link between alteration in octopamine related signals and MWCNT toxicity induction in offspring in organisms.

Characterization and in vivo toxicological evaluation of multi-walled carbon nanotubes: a low-dose repeated intratracheal administration study

This study characterized and investigated the toxicity of two multi-walled carbon nanotubes (MWCNT) NM-401 and NM-403 at 60 and 180 µg after four repeated intratracheal instillations; follow-up times were 3, 7, 30, and 90 days after the last instillation. NM-401 was needle-like, long, and thick, while NM-403 was entangled, short, and thin. Both MWCNT types induced transient pulmonary and systemic alterations in renal function and oxidative lipid damage markers in recent times. Animals showed general toxicity in the immediate times after exposures, in addition to increased pulmonary LDH release at day 3. In further times, decreased liver and kidney relative weights were noted at higher MWCNT doses. Lung histological damages included pulmonary fibrosis, for both MWCNT types, similarly to asbestos; single liver and kidney histological alterations were present. Repeated instillations led to persistent pulmonary damage at low doses, and possibly the extrapulmonary effects may be associated with the consecutive exposures.

Aging influence on pulmonary and systemic inflammation and neural metabolomics arising from pulmonary multi-walled carbon nanotube exposure in apolipoprotein E-deficient and C57BL/6 female mice

OBJECTIVE

Environmental exposures exacerbate age-related pathologies, such as cardiovascular and neurodegenerative diseases. Nanoparticulates, and specifically carbon nanomaterials, are a fast-growing contributor to the category of inhalable pollutants, whose risks to health are only now being unraveled. The current study assessed the exacerbating effect of age on multiwalled-carbon nanotube (MWCNT) exposure in young and old C57BL/6 and ApoE-/- mice.

MATERIALS AND METHODS

Female C57BL/6 and apolipoprotein E-deficient (ApoE-/-) mice, aged 8 weeks and 15 months, were exposed to 0 or 40 µg MWCNT via oropharyngeal aspiration. Pulmonary inflammation, inflammatory bioactivity of serum, and neurometabolic changes were assessed at 24 h post-exposure.

RESULTS

Pulmonary neutrophil infiltration was induced by MWCNT in bronchoalveolar lavage fluid in both C57BL/6 and ApoE-/-. Macrophage counts decreased with MWCNT exposure in ApoE-/- mice but were unaffected by exposure in C57BL/6 mice. Older mice appeared to have greater MWCNT-induced total protein in lavage fluid. BALF cytokines and chemokines were elevated with MWCNT exposure, but CCL2, CXCL1, and CXCL10 showed reduced responses to MWCNT in older mice. However, no significant serum inflammatory bioactivity was detected. Cerebellar metabolic changes in response to MWCNT were modest, but age and strain significantly influenced metabolite profiles assessed. ApoE-/- mice and older mice exhibited less robust metabolite changes in response to exposure, suggesting a reduced health reserve.

CONCLUSIONS

Age influences the pulmonary and neurological responses to short-term MWCNT exposure. However, with only the model of moderate aging (15 months) in this study, the responses appeared modest compared to inhaled toxicant impacts in more advanced aging models.

Biomimetic Material for Quantification of Methotrexate Using Sensor Based on Molecularly Imprinted Polypyrrole Film and MWCNT/GCE

This study investigates biomimetic sensors for the detection of methotrexate contaminants in environmental samples. Sensors inspired by biological systems are the focus of this biomimetic strategy. Methotrexate is an antimetabolite that is widely used for the treatment of cancer and autoimmune diseases. Due to the widespread use of methotrexate and its rampant disposal into the environment, the residues of this drug are regarded as an emerging contaminant of huge concern, considering that exposure to the contaminant has been found to lead to the inhibition of some essential metabolic processes, posing serious risks to humans and other living beings. In this context, this work aims to quantify methotrexate through the application of a highly efficient biomimetic electrochemical sensor constructed using polypyrrole-based molecularly imprinted polymer (MIP) electrodeposited by cyclic voltammetry on a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNT). The electrodeposited polymeric films were characterized by infrared spectrometry (FTIR), scanning electron microscopy (SEM), and cyclic voltammetry (CV). The analyses conducted using differential pulse voltammetry (DPV) yielded a detection limit of 2.7 × 10^-9 mol L^-1 for methotrexate, a linear range of 0.01-125 μmol L^-1, and a sensitivity of 0.152 μA L mol^-1. The results obtained from the analysis of the selectivity of the proposed sensor through the incorporation of interferents in the standard solution pointed to an electrochemical signal decay of only 15.4%. The findings of this study show that the proposed sensor is highly promising and suitable for use in the quantification of methotrexate in environmental samples.

Outstanding Separation Performance of Oil-in-Water Emulsions with TiO2/CNT Nanocomposite-Modified PVDF Membranes

Membrane filtration is an effective technique for separating micro- and nano-sized oil droplets from harmful oil-contaminated waters produced by numerous industrial activities. However, significant flux reduction discourages the extensive application of this technology; therefore, developing antifouling membranes is necessary. For this purpose, various titanium dioxide/carbon nanotube (TiO₂/CNT) nanocomposites (containing 1, 2, and 5 wt.% multi-walled CNTs) were used for the modification of polyvinylidene fluoride (PVDF) ultrafilter (250 kDa) membrane surfaces. The effects of surface modifications were compared in relation to the flux, the filtration resistance, the flux recovery ratio, and the purification efficiency. TiO₂/CNT_2% composite modification reduced both irreversible and total filtration resistances the most during the filtration of 100 ppm oil emulsions. The fluxes were approximately 4-7 times higher compared to the unmodified PVDF membrane, depending on the used transmembrane pressure (510, 900, and 1340 L/m²h fluxes were measured at 0.1, 0.2, and 0.3 MPa pressures, respectively). Moreover, the flux recovery ratio (up to 68%) and the purification efficiency (95.1-99.8%) were also significantly higher because of the surface modification, and the beneficial effects were more dominant at higher transmembrane pressures. TiO₂/CNT_2% nanocomposites are promising to be applied to modify membranes used for oil-water separation and achieve outstanding flux, cleanability, and purification efficiency.

Hybrid Nano Flake-like Vanadium Diselenide Combined on Multi-Walled Carbon Nanotube as a Binder-Free Electrode for Sodium-Ion Batteries

As the market for electric vehicles and portable electronic devices continues to grow rapidly, sodium-ion batteries (SIBs) have emerged as energy storage systems to replace lithium-ion batteries (LIBs). However, sodium-ion is heavier and larger than lithium-ion, resulting in volume expansion and slower ion transfer. It is necessary to find suitable anode materials with high capacity and stability. In addition, wearable electronics are starting to be commercialized, requiring a binder-free electrode used in flexible batteries. In this work, we synthesized nano flake-like VSe₂ using organic precursor and combined it with MWCNT as carbonaceous material. VSe₂@MWCNT was mixed homogenously using sonication and fabricated film electrodes without a binder and substrate via vacuum filter. The hybrid electrode exhibited high-rate capability and stable cycling performance with a discharge capacity of 469.1 mAhg^-1 after 200 cycles. Furthermore, VSe₂@MWCNT exhibited coulombic efficiency of ~99.7%, indicating good cycle stability. Additionally, VSe₂@MWCNT showed a predominant 85.5% of capacitive contribution at a scan rate of 1 mVs^-1 in sodiation/desodiation process. These results showed that VSe₂@MWCNT is a suitable anode material for flexible SIBs.

Zinc Vanadate (Zn3V2O8) Immobilized Multiwall Carbon Nanotube (MWCNT) Heterojunction as an Efficient Photocatalyst for Visible Light Driven Hydrogen Production

Z-scheme photocatalytic reaction is considered an effective strategy to promote the photogenerated electron-hole separation for significantly improving the efficiency of photocatalytic hydrogen precipitation from splitting water. In this study, a heterojunction nanocomposite material based on Zn₃V₂O₈ (ZV) with MWCNT was prepared by a hydrothermal process. The photocatalysts were characterized by X-ray diffraction, scanning electron microscopy (SEM), Fourier transform infrared (FTIR), UV-visible absorption spectroscopy, and transmission electron microscopy (TEM) to understand crystal structure, morphology, and optical properties. The efficiency of the samples was evaluated for the photocatalytic H₂ production under visible solar radiation using water glycerol as a sacrificial reagent. The obtained results suggest that, between ZV and ZV@MWCNT, the latter shows higher efficiency for H₂ production. The maximum H₂ production efficiency was found to be 26.87 μmol g^-1 h^-1 for ZV and 99.55 μmol g^-1 h^-1 for ZV@MWCNT. The synergistic effect of MWCNT to ZV resulted in improving the efficiency of charges and light-absorbing capacity, resulting in enhanced H₂ production in the heterojunction nanocomposite material. The nanocomposite was stable and highly efficient for H₂ production of six or more cycles. Based on the outcomes of this study, it can be observed that forming the heterojunction of individual nano systems could result in more efficient material for H₂ production under visible solar energy.

Three-Dimensional van der Waals Heterostructure-Based Nanocages as Supersensitive 3-Hydroxy-2-butanone Gas Sensors at Room Temperature

3-Hydroxy-2-butanone is one of the biomarkers of Listeria monocytogenes, which is quite important for the intelligent detection of 3H-2B. However, it is still a challenge to fabricate sensing materials obtaining excellent sensitivity and selectivity under the ppb-level detection limit. Herein, a plasma-assisted synthetic approach was proposed for the construction of hierarchical nanostructures and the simultaneous loading of TAPP-COFs, which could reduce interlayer interaction and convert the metallized sites on the surface of predesigned porphyrin rings into quantum nanoparticles. These multichannel pathways of Co-TAPP-COFs@SnO₂@MWCNTs nanocages contributed to the gas adsorption and diffusion, thus enhancing the sensing behavior. The nanocages exhibited a highly specific sensing performance toward 3H-2B with the highest sensitivity (R_a/R_g = 100.9 to 0.5 ppm) in all reported sensing materials. The 3H-2B sensor presented outstanding long-term stability, and the detection limit was 100 ppb at room temperature. Furthermore, the synthesized materials were integrated into the sensing module connecting to an Internet of Things platform, providing rapid and real-time detection of 3H-2B. We also applied machine learning methods to analyze the nanocage-based sensors and found that the combined effects of modified sites on the heterointerfaces contributed to the improvement of the sensing performance.

Hemin-Modified Multi-Walled Carbon Nanotube-Incorporated PVDF Membranes: Computational and Experimental Studies on Oil-Water Emulsion Separations

The separation of oil/water emulsions has attracted considerable attention for decades due to the negative environmental impacts brought by wastewater. Among the various membranes investigated for separation, polyvinylidene fluoride (PVDF) membranes have shown significant advantages of ease of fabrication, high selectivity, and fair pore distribution. However, PVDF membranes are hydrophobic and suffer from severe fouling resulting in substantial flux decline. Meanwhile, the incorporation of wettable substrates during fabrication has significantly impacted the membrane performance by lowering the fouling propensity. Herein, we report the fabrication of an iron-containing porphyrin (hemin)-modified multi-walled carbon nanotube incorporated PVDF membrane (HA-MWCNT) to enhance fouling resistance and the effective separation of oil-in-water emulsions. The fabricated membrane was thoroughly investigated using the FTIR, SEM, EDX, AFM, and contact angle (CA) analysis. The HA-MWCNT membrane exhibited a water CA of 62° ± 0.5 and excellent pure water permeance of 300.5 L/m2h at 3.0 bar (400% increment), in contrast to the pristine PVDF, which recorded a CA of 82° ± 0.8 and water permeance of 59.9 L/m2h. The hydrophilic HA-MWCNT membrane further showed an excellent oil rejection of >99% in the transmembrane pressure range of 0.5−2.5 bar and a superb flux recovery ratio (FRR) of 82%. Meanwhile, the classical molecular dynamics (MD) simulations revealed that the HA-MWCNT membrane had greater solvent-accessible pores, which enhanced water permeance while blocking the hydrocarbons. The incorporation of the hemin-modified MWCNT is thus an excellent strategy and could be adopted in the design of advanced membranes for oil/water separation.

Effects of inhalation of multi-walled carbon nanotube (MWCNT) on respiratory syncytial virus (RSV) infection in mice

Multi-walled carbon nanotubes (MWCNTs), a kind of nanomaterial, are widely used in battery electrodes and composite materials, but the adverse effects associated with their accumulation in the living body have not been sufficiently investigated. MWCNTs are a fibrous material with molecules similar to asbestos fibers, and there are concerns about its effects on the respiratory system. In this study, we conducted a risk assessment by exposing mice using a previously developed nanomaterial inhalation exposure method. We quantified the exposure in the lungs by a lung burden test, evaluated the deterioration due to pneumonia using respiratory syncytial virus (RSV) infection, and measured inflammatory cytokines in bronchoalveolar lavage fluid (BALF). As a result, in the lung burden test, the amount of MWCNT in the lung increased according to the inhalation dose. In the RSV infection experiment, CCL3, CCL5, and TGF-β, which are indicators of inflammation and lung fibrosis, were elevated in the MWCNT-exposed group. Histological examination revealed cells phagocytosing MWCNT fibers. These phagocytic cells were also seen during the recovery period from RSV infection. The present study found that MWCNT remained in the lungs for about a month or more, suggesting that the fibers may continue to exert immunological effects on the respiratory system. Furthermore, the inhalation exposure method enabled the exposure of nanomaterials to the entire lung lobe, allowing a more detailed evaluation of the effects on the respiratory system.

Continuous infiltration of small peritoneal macrophages in the mouse peritoneum through CCR2-dependent and -independent routes during fibrosis and mesothelioma development induced by a multiwalled carbon nanotube, MWNT-7

Although toxicities of multiwalled carbon nanotube (MWCNT) have been found to be related with activities of macrophages phagocytosing the fibers, the exact relationship between macrophage population and pathogenesis of fibrosis and mesotheliomas induced by MWCNTs is largely unknown. CCL2-CCR2 axis, a major monocyte/macrophage infiltration route, is thought to be involved in not only acute inflammation but also the formation of tumor microenvironment. We therefore described a time-course of alteration of macrophage population in an attempt to clarify the contribution of the Ccr2 gene to mesotheliomagenesis. Wild-type (WT) C57BL/6 mice and Ccr2-knockout (KO) mice were intraperitoneally administered with MWNT-7 and were sequentially necropsied at 1, 7, 28, 90, and 245 day(s) after the injection. Peritoneal fibrosis was prominent in all MWCNT-treated mice, with a lower severity in the KO mice. No differences were observed in the incidences of neoplastic lesions of mesothelia between WT and KO mice. A flow cytometric analysis revealed that after gross disappearance of macrophages after MWCNT exposure, small peritoneal macrophages (SPMs) were exclusively refurbished by the CCR2-dependent route at day 1 (as Ly-6C+MHC class II- cells), followed by additional CCR2-independent routes (as Ly-6C-MHC class II- cells); i.e., the only route in KO mice; with a delay of 1-7 days. The SPMs derived from both routes appeared to differentiate into maturated cells as Ly-6C-MHC class II+, whose ratio increased in a time-dependent manner among the total SPM population. Additionally, most macrophages expressed M1-like features, but a small fraction of macrophages exhibited an M1/M2 mixed status in MWCNT-treated animals. Our findings demonstrate a long-persistent activation of the CCL2-CCR2 axis after MWCNT exposure and enable a better understanding of the participation and potential roles of SPMs in fibrous material-induced chronic toxicities.

High Temperature Performance of Concrete Confinement by MWCNT Modified Epoxy Based Fiber Reinforced Composites

The conventional method of fiber reinforced polymer (FRP) wrapping around concrete columns uses epoxy as the binder along with synthetic or natural fibers such as carbon, glass, basalt, jute, sisal etc. as the reinforcement. However, the thermal stability of epoxy is a major issue in application areas prone to fire exposure. The current work addressed this major drawback of epoxy by modifying it with a nanofiller, such as multiwalled carbon nanotubes (MWCNT), and reinforcing it using basalt and sisal fibers. The effect of exposure to elevated temperature on the behavior of concrete cylinders externally confined with these FRP systems was analyzed. Three types of specimens were considered: unconfined; confined with sisal fiber reinforced polymer (SFRP); and confined with hybrid sisal basalt fiber reinforced polymer (HSBFRP) specimens. The test samples were exposed to elevated temperature regimes of 100 °C, 200 °C, 300 °C and 400 °C for a period of 2 h. The compressive strengths of unconfined specimens were compared with various confined specimens, and from the test results, it was evident that the mechanical and thermal durability of the FRP systems was substantially enhanced by MWCNT incorporation. The reduction in the compressive strength of the FRP-confined specimens varied depending on the type of the confinement. After two hours of exposure at 400 °C, the compressive strength corresponding to the epoxy-HSBFRP-confined specimens were improved by 15%, whereas a 50% increase in strength corresponding to MWCNT-incorporated epoxy-HSBFRP-confined specimens was observed with respect to unconfined unexposed specimens. The MWCNT-modified epoxy-incorporated FRP-confined systems demonstrated superior performance even at elevated temperatures in comparison to unconfined specimens at ambient temperatures.

Effects of Molarity and Storage Time of MWCNTs on the Properties of Cement Paste

Nowadays, nanomaterials in cement pastes are among the most important topics in the cement industry because they can be used for several applications. For this reason, this work presents a study about the influence of changing the molarity of dispersed multiple wall carbon nanotubes (MWCNTs) and varying the number of storage days on the mechanical properties of the cement paste. To achieve this objective, dispersions of 0.35% MWCNTs, varying the molarity of the surfactant as 10 mM, 20 mM, 40 mM, 60 mM, 80 mM, and 100 mM, were performed. The mixture of materials was developed using the sonication process; furthermore, materials were analyzed using UV-Vis, Z-potential, and Raman spectroscopy techniques. Materials with a molarity of 10 mM exhibited the best results, allowing them to also be stored for four weeks. Regarding the mechanical properties, an increase in the elastic modulus was observed when MWCNTs were included in the cement paste for all storage times. The elastic modulus and the maximum stress increased as the storage time increased.

Effective Attenuation of Electromagnetic Waves by Synergetic Effect of α-Fe2O3 and MWCNT/Graphene in LDPE-Based Composites for EMI Applications

In this study, a polymer nanocomposite is synthesized using magnetic and conducting fillers for enhanced electromagnetic interference (EMI) shielding. Alfa-ferrite (α-Fe₂O₃) nanoparticles with minimal multiwalled carbon nanotube (MWCNT) as low as 5 weight % in combination with variable concentrations of graphene nanoplatelets (GNP) are used as fillers in low-density polyethylene (LDPE) polymer matrix. Nanofillers and the polymer matrix are characterized by various techniques such as XRD, SEM, color mapping, EDAX, TGA, etc. The EMI shielding efficiency of the LDPE-based nanocomposites is tested using Vector Network Analyzer (VNA). The results showed that composite with LDPE:MWCNT:GNP:α-FO-50:5:40:5 displayed enhanced EMI shielding (in X-band (8.2-12.4 GHz) compared to other concentrations studied. This is due to the superior ohmic, dielectric, and magnetic losses at this particular composition and to the synergism amongst the filler. An attenuation of 99.99% was achieved for 5% α-Fe₂O₃. The mechanistic aspects of the shielding are discussed using permittivity, conductivity, and attenuation.

Electrochemical Sensor Based on Multi-Walled Carbon Nanotubes and N-Doped TiO2 Nanoparticles for Voltametric Simultaneous Determination of Benserazide and Levodopa

An electrochemical sensor for simultaneous determination of Benserazide (BEZ) and levodopa (L-dopa) was successfully developed using a glassy carbon electrode (GCE) modified with multi-walled carbon nanotube and nitrogen-doped titanium dioxide nanoparticles (GCE/MWCNT/N-TiO₂). Cyclic voltammetry and square wave voltammetry were employed to investigate the electrochemical behavior of different working electrodes and analytes. In comparison with unmodified GCE, the modified electrode exhibited better electrocatalytic activity towards BEZ and L-dopa and was efficient in providing a satisfactory separation for oxidation peaks, with a potential difference of 140 mV clearly allows the simultaneous determination of these compounds. Under the optimized conditions, linear ranges of 2.0-20.0 and 2.0-70.0 μmol L^-1 were obtained for BEZ and L-dopa, respectively, with a limit of detection of 1.6 µmol L^-1 for BEZ and 2.0 µmol L^-1 for L-dopa. The method was applied in simultaneous determination of the analytes in pharmaceutical samples, and the accuracy was attested by comparison with HPLC-DAD as the reference method, with a relative error lower than 4.0%.

Novel Experimental Setup for Coulometric Signal Transduction of Ion-Selective Electrodes

In this work, a novel and versatile experimental setup for coulometric signal transduction of ion-selective electrodes (ISEs) is introduced and studied. It is based on a constant potential coulometric measurement carried out using a one-compartment three-electrode electrochemical cell. In the setup, a potassium ion-selective electrode (K⁺- ISE) is connected as the reference electrode (RE). A poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS)-based electrode with a dummy membrane (DM) and a glassy carbon (GC) rod are connected as the working electrode (WE) and counter electrode (CE), respectively. Adding a non-selective dummy membrane to the structure of the WE facilitates the regulation of the measured signal and response time. The results from electrochemical impedance spectroscopy measurements carried out on the WE showed that the time constant is profoundly influenced by the dummy membrane thickness. In addition, the redox capacitance of the PEDOT:PSS film shows a better correlation with the electrode area than the film thickness. Sequential addition/dilution experiments showed the improvement of current and cumulated charge signals in the new setup studied in this work compared to the setup used in the original coulometric signal transduction method. Both conventional ISEs and solid-contact ISEs (SCISEs) were used in this work. The results showed that the coulometric response was independent of the type of ISE used as RE, confirming the versatility of the novel set-up.

Potentiality of MWCNT on 3D-printed bio-inspired spherical-roof cubic core under quasi-static loading

Sandwich panel is increasingly used as lightweight energy absorbing components, which provides excellent crashworthiness performance with the three-dimensional periodic core. This paper investigates 3D-printed bio-inspired spherical-roof cubic cores with multi-walled carbon nanotubes (MWCNT) and foam-filled cores under quasi-static loading. The proposed bio-inspired spherical-roof cubic cores with 1.5 mm wall thickness were manufactured using the fused filament fabrication process, which used 70% polylactic acid (PLA) and 30% carbon fiber filament. Moreover, four groups of 3D-printed bio-inspired spherical-roof cubic cores were compared and analyzed on compressive properties and failure behavior. Experimental results were shown that foam-filled double bio-inspired spherical-roof cubic core with MWCNT was the maximum Fpeak with 1.92 kN, which provided a much more stable plateau load and better energy-absorbing characteristics. In addition, it is conducted that a double bio-inspired spherical-roof cubic core with four notches core is considered as the potential energy-absorbing core.

Effect of Recycling on the Mechanical, Thermal and Rheological Properties of Polypropylene/Carbon Nanotube Composites

In this research the effect of physical recycling on the mechanical, thermal, and rheological properties of polypropylene (PP)/multiwalled carbon nanotube (MWCNT) was investigated. After melt homogenization by extrusion, specimens were injection moulded with 0.1 and 0.5 wt% MWCNT content. The recycling process was simulated by multiple grinding and re-moulding, then we compared the behavior of original and recycled PP/MWCNT composites. Differential scanning calorimetry (DSC) measurements proved that MWCNT had double the effect on the morphology of the PP matrix: on the one hand nucleating effect can be detected because 0.5 wt% MWCNT increased the onset temperature of crystallization by 10 °C, compared to the basic PP material; on the other hand, the crystalline fraction of the recycled composite materials decreased compared to the original PP material with the same MWCNT content. This resulted in a slight decrease in strength and stiffness but an increase in elongation at break. However, compared to the original unreinforced PP reference, even the recycled materials have better properties. The mechanical test results showed that recycled PP/MWCNT 0.5 wt% increased the elastic modulus (~15%) and decreased the tensile strain at yield (~10%). However, in the values of tensile stress at yield, relevant difference was not found. It was also shown by oscillatory rheometry that MWCNT had a significant effect on the rheological properties (storage and loss modulus, complex viscosity) of PP compounds in a wide temperature range (190-230 °C).

An ultra-sensitive rifampicin electrochemical sensor based on Fe3O4 nanoparticles anchored Multiwalled Carbon nanotube modified glassy carbon electrode

This study aimed to guide future sensor studies against other pharmaceutical drugs by synthesizing Fe₃O₄NPs@MWCNT metallic nanoparticles (NPs). Side damage caused by excessive accumulation of tuberculosis drugs in the body can cause clots in the organs, and cause serious damage such as heart attack and respiratory failure, and threaten human life. Therefore, the development of sensors sensitive to various antibiotics in this study is important for human health. In this study, the sensitivity of Fe₃O₄ NPs to tuberculosis drug (rifampicin) was evaluated by catalytic reaction using bare/GCE, MWCNT/GCE, and Fe₃O₄NPs@MWCNT/GCE electrodes. First of all, Fe₃O₄ NPs were successfully synthesized for the study and MWCNT/GCE and Fe₃O₄ NPs@MWCNT/GCE electrodes were formed with the modification of the MWCNT support material. It was observed that the Fe₃O₄ NPs@MWCNT/GCE electrode gave the highest signal against the other electrodes. The morphological structure of Fe₃O₄ NPs was determined by various characterization techniques such as Transmission Electron Microscopy (TEM), Fourier Transmission Infrared Spectroscopy (FTIR), ultraviolet-visible (UV-Vis), and X-ray differential (XRD) and the obtained NPs were used for sensor studies, and it was observed that the current intensity increased as the scanning speed of each electrode increased in CV and DPV measurements. The average size of Fe₃O₄ NPs was found to be 7.32 ± 3.2 nm. Anodic current peaks occurred in the linear range of 2-25 μM. According to the results obtained from the measurements, the limit of detection (LOD) value was calculated as 0.64 μM limit of quantification (LOQ) 1.92 μM.

MWCNT supported V2O5 quantum dot nanoparticles decorated Bi2O3 nanosheets hybrid system: Efficient visible light driven photocatalyst for degradation of ciprofloxacin

A novel composite of multiwall carbon nanotube (MWCNT) supported V₂O₅ quantum dots decorated Bi₂O₃ hybrid was prepared by the simple wet-impregnation method, and the photocatalytic performance of the prepared samples was investigated against the photodegradation of ciprofloxacin (CIP). Herein, different samples of pristine, V₂O₅/Bi₂O₃ and MWCNT@V₂O₅/Bi₂O₃ hybrid photocatalyst were prepared and systematically characterized by various physicochemical techniques. The characterization results demonstrated that the introduction of MWCNT can change the energy band gap of V₂O₅/Bi₂O₃, and the band energies vary with a constituent of MWCNT@V₂O₅/Bi₂O₃ catalyst, in which MWCNT@V₂O₅/Bi₂O₃-5 (0.05 g@0.50 g:0.50 g) has the optimal band gap energy of 2.46 eV. The photocatalytic test demonstrates that the MWCNT@V₂O₅/Bi₂O₃-5 hybrid composites exhibited enhanced photocatalytic activity in CIP degradation compared to that pure and other photocatalyst and its degradation efficiency did not decrease significantly even after five cyclic experiments. The enhanced photocatalytic activity was due to the formation of heterojunction among MWCNT, V₂O₅ and Bi₂O₃, which distinctly improved the separation efficiency of the photogenerated charge carrier, thus increasing the degradation performance. This work gives a new approach to designing an efficient photocatalyst for contaminants degradation.

Electronic structure modulation of multi-walled carbon nanotubes using azo dye for inducing non-radical reaction: Effect of graphitic nitrogen and structural defect

Multiwalled carbon nanotube (MWCNT) have a great potential for advanced oxidation process as a metal free catalyst. However, there catalytic activity is very low and needs to be appropriately tuned. Herein, we demonstrate a novel synthesis method for tuning the defect and surface functionality of MWCNT using azo dyes and the catalytic performance was tested for the degradation of different organic contaminates using PMS as an oxidant. The content, type of heteroatom functional groups, and the defect parameters were optimized by varying the pH and concentration of the organic dye. The quenching effect showed that singlet oxygen (¹O₂) is the primary reactive species generated by graphitic nitrogen, which can be boosted by the degree of graphitic structure disruption in MWCNT. The Linear sweep voltammetry (LSV) also confirmed that extrinsic doping enhanced the non-radical degradation by increasing the direct charge transfer rate from MB to PMS. Moreover, the designed catalyst showed a fast degradation performance with 35.1 kJ/mol activation energy and achieved the highest dye degradation rate and even surpassed some state-of-the-art metal-based and metal-free catalysts. The effect of inorganic anions study has also confirmed its industrial applicability.

Silver Nanoparticle-Decorated Multiwalled Carbon Nanotube Ink for Advanced Wearable Devices

Silver nanoparticles of average size 12-13 nm were successfully decorated on the surface of multiwalled carbon nanotubes (MWCNTs) through a scalable wet chemical method without altering the structure of the MWCNTs. Employing this Ag@MWCNT, a multifunctional room-temperature curable conductive ink was developed, with PEDOT:PSS as the conductive binder. Screen printing of the ink could yield conductive planar traces with a 9.5 μm thickness and a conductivity of 28.99 S/cm, minimal surface roughness, and good adhesion on Mylar and Kapton. The versatility of the ink for developing functional elements for printed electronics was demonstrated by fabricating prototypes of a wearable strain sensor, a smart glove, a wearable heater, and a wearable breath sensor. The printed strain sensor exhibited a massive sensing range for wearable applications, including an impressive 1332% normalized resistance change under a maximum stretchability of 23% with superior cyclic stability up to 10 000 cycles. The sensor also exhibited an impeccable gauge factor of 142 for a 5% strain (59 for 23%). Furthermore, the sensor was integrated into a smart glove that could flawlessly replicate a human finger's gestures with a minimal response time of 225-370 ms. Piezoresistive vibration sensors were also fabricated by printing the ink on Mylar, which was employed to fabricate a smart mask and a smart wearable patch to monitor variations in human respiratory and pulmonary cycles. Finally, an energy-efficient flexible heater was fabricated using the developed ink. The heater could generate a uniform temperature distribution of 130 °C at the expense of only 393 mW/cm² and require a minimum response time of 20 s. Thus, the unique formulation of Ag@MWCNT ink proved suitable for versatile devices for future wearable applications.

Tetracycline capture from aqueous solutions by nanocomposite of MWCNTs reinforced with glutaraldehyde cross-linked poly (vinyl alcohol)/chitosan

The presence of pharmaceuticals as the emerging contaminates needs novel approaches and new materials to be remediated. This study aimed to develop and apply MWCNTs reinforced with glutaraldehyde cross-linked poly (vinyl alcohol)/chitosan nanocomposite (MWCNTs/CS-PVA/GA NC) for removal of tetracycline (TC) as a model of antibiotics from aqueous solutions. The successful synthesis of NC was supported by techniques of SEM, XRD, TGA, FTIR, and EDX. The prepared NC was then utilized for TC adsorption under the main effective parameters of TC concentration (25-125 mg/L), sonication time (0-8 min), NC dose (1-130 mg), and tempearure (5-45 °C). The process behavior was comparably explored with different methods of central composite design (CCD), artificial neural networks (ANN), and general regression neural network (GRNN). The results showed that under the optimum settings presented by desirability function (DA), in which the respective values for the factors were 125 mg/L, 6.8 min, 130 mg, and 45 °C, the efficiency and adsorption capacity of NC is supposed to be 99.07% and ∼525 mg/g, respectively. From the models studied, although all were able to express the process with satisfactory accuracy, ANN provided the best accuracy and reliability owning to the highest R² (0.999) and lowest RMSE, ADD, MAE. The kinetics, isotherms, and thermodynamic studies showed that the process is fast (over 4.5 min), chemisorption, heterogeneous with multilayer nature, spontaneous, feasible, and endothermic. In addition, the as prepared NC could be recycled for five times without significant fail in its performance. All in all, the developed MWCNTs/CS-PVA/GA NC can be considered as a promising candidate in dealing with aqueous solutions' pollution with antibiotic.

Enhanced neurogenic differentiation on anisotropically conductive carbon nanotube reinforced polycaprolactone-collagen scaffold by applying direct coupling electrical stimulation

Electrical stimulation is conducive to neural regeneration. Different types of stimuli propagation patterns are required for regenerating cells in peripheral and central nervous systems. Modulation of the pattern of stimuli propagation cannot be achieved through external means. Reinforcing scaffolds, with suitably shaped conductive second phase materials, is a promising option in this regard. The present study has taken the effort of modulating the pattern (arrangement) of reinforced phase, namely multiwalled carbon nanotubes (MWCNT), in a biodegradable scaffold made of PCL-collagen mixture, by applying an external electric field during curing. Because of their extraordinary physical properties, MWCNTs have been selected as nano-reinforcement for this study. The nature of reinforcement affects the electrical conductivity of the scaffold and also determines the type of cell it can support for regeneration. Further, electrical stimulation, applied during incubation, was observed to have a positive influence on differentiating neural cells in vitro. However, the structure of the nano-reinforcement determined the differentiated morphology of the cells. Reinforced MWCNTs being tubes, imparted bipolarity to the cells. Therefore, these scaffolds, coupled with electrical stimulation possess significant potential to be used for directional regeneration of the nerves.

Investigations on influences of MWCNT composite membranes in oil refineries waste water treatment with Taguchi route

Most of the 'oil refineries' severally pollutes the water resources by depleting their untreated waste water like cooling water, storm water and unsanitary sewage water. These wastewaters are to be treated with high care to protect the human, pebbles, plants, fish and other water animals and from harmful effects. The present study focused to treat the oil refinery wastewater by means of Multi wall carbon nanotube (MWCNT) coated Polyvinylidene Fluoride (PVDF) membrane. The main objectives are: to increases the life of filter, reduce the percolation flux and reduce the formation of antifouling in the filter by using MWCNT composite membrane in it. Different process parameters of the proposed water treatment process, like diameter of MWCNT (15 nm, 20 nm, 25 nm and 30 nm), operating pressure (3 bar, 4 bar, 5 bar and 6 bar), pH value (3, 5, 7 and 9) and temperature (25 °C, 30 °C, 35 °C and 40 °C) temperature. Taguchi statistical technique is employed for designing experiments and for optimizing the process parameters of wastewater treatment process of an oil refinery. The proposed filter for wastewater treatment exhibited appreciable performance in removal rate of Percolation flux, percentage of chemical oxygen demand removal and percentage of total carbolic rejection as 27.2 kg/m²h, 78.51% and 95.33% respectively.

Friction Properties of Solid Lubricants with Different Multiwalled Carbon Nanotube Contents

Bushes are circular bearings that surround a shaft and help it rotate smoothly. In heavy equipment, bushes are coated with solid lubricants to reduce friction. Although the coating layer of the lubricant has a stable coefficient of friction (CoF), it is important that this should last for a long time. In this study, multiwalled carbon nanotubes (MWCNTs), which have a low CoF, were added to the lubricant to improve its performance. When 2.3 wt% MWCNTs were added to the polymer resin, the dynamic CoF (under a 29 N external load) decreased by 78% in relation to that of the resin without MWCNTs. As the MWCNT content increased, the roughness of the coating decreased, which reduced the CoF. Moreover, MWCNT addition increased the overall tensile strength owing to an increase in the bonding force between the resins. Under a high load of 20 tonnes (t), the MWCNT-based solid lubricant had a CoF of 0.05, lower than commercial MoS₂-based solid lubricants; this was maintained for more than 10,000 cycles in a bush and shaft test. With the MWCNT-based solid lubricant, a lubricating polymer film formed, even on worn bush surfaces. The CoF of the solid lubricant was reduced and the number of cycles with a constant CoF increased when MWCNTs were added owing to the formation of the lubricating polymer film.

Modification of epoxy binder with multi walled carbon nanotubes in hybrid fiber systems used for retrofitting of concrete structures: evaluation of strength characteristics

The rapid development in infrastructural facilities necessitates an efficient approach for the repair and retrofitting of concrete structures and, confinement method using fiber reinforced polymer is a promising one. The commonly used carbon and glass fibers for confinement poses environmental and performance issues. The present study addresses these two major aspects by considering natural fibers along with modification of epoxy binder to impart ductile behavior ie., to investigate the effectiveness of multiwalled carbon nanotubes (MWCNT) incorporated synthetic and natural fiber reinforced polymer (FRP) systems as the external confinement. MWCNT is incorporated in 0.5-1.5wt.% in epoxy nano and epoxy multiscale and there is significant enhancement in tensile and fracture properties of the composites up to 1wt.%, beyond which it declined due to agglomeration. Various strength tests were performed with sisal, basalt, carbon and hybrid sisal-basalt FRP systems with different FRP layer thickness on plain concrete cylinders. From the test results it is outlined that external confinement with MWCNT incorporated FRP improved the axial load-carrying capacity, energy absorption and ductility of concrete with respect to that of control specimens. Compared with unconfined specimens, those strengthened with MWCNT modified hybrid FRP wraps containing sisal and basalt fibers recorded increments of 114% and 87% in their load-carrying capacity and energy absorption, due to the intrinsic rigidity of hybrid fibers and epoxy modification. Furthermore, the outcomes indicate that MWCNT incorporated hybrid sisal-basalt FRP confined specimens exhibited superior properties and the low strength of natural FRP confinement compared to artificial FRP can be improved by epoxy modification. The outer jacketing resisted abrupt and catastrophic failure to a great extent.

Two-year intermittent exposure of a multiwalled carbon nanotube by intratracheal instillation induces lung tumors and pleural mesotheliomas in F344 rats

BACKGROUND

A mounting number of studies have been documenting the carcinogenic potential of multiwalled carbon nanotubes (MWCNTs); however, only a few studies have evaluated the pulmonary carcinogenicity of MWCNTs in vivo. A 2-year inhalation study demonstrated that MWNT-7, a widely used MWCNT, was a pulmonary carcinogen in rats. In another 2-year study, rats administered MWNT-7 by intratracheal instillation at the beginning of the experimental period developed pleural mesotheliomas but not lung tumors. To obtain data more comparable with rats exposed to MWNT-7 by inhalation, we administered MWNT-7 to F344 rats by intratracheal instillation once every 4-weeks over the course of 2 years at 0, 0.125, and 0.5 mg/kg body weight, allowing lung burdens of MWNT-7 to increase over the entire experimental period, similar to the inhalation study.

RESULTS

Absolute and relative lung weights were significantly elevated in both MWNT-7-treated groups. Dose- and time-dependent toxic effects in the lung and pleura, such as inflammatory, fibrotic, and hyperplastic lesions, were found in both treated groups. The incidences of lung carcinomas, lung adenomas, and pleural mesotheliomas were significantly increased in the high-dose group compared with the control group. The pleural mesotheliomas developed mainly at the mediastinum. No MWNT-7-related neoplastic lesions were noted in the other organs. Cytological and biochemical parameters of the bronchoalveolar lavage fluid (BALF) were elevated in both treated groups. The lung burden of MWNT-7 was dose- and time-dependent, and at the terminal necropsy, the average value was 0.9 and 3.6 mg/lung in the low-dose and high-dose groups, respectively. The number of fibers in the pleural cavity was also dose- and time-dependent.

CONCLUSIONS

Repeated administration of MWNT-7 by intratracheal instillation over the 2 years indicates that MWNT-7 is carcinogenic to both the lung and pleura of rats, which differs from the results of the 2 carcinogenicity tests by inhalation or intratracheal instillation.