Application Of Multiwalled Carbon Nanotubes Research Articles

Multi-Walled Carbon Nanotubes Improve the Development of Chrysanthemum × morifolium (Ramat.) Hemsl. ‘Jinba’ Inflorescences

The application of cut flower preservation technology can significantly enhance both the ornamental and economic value of fresh-cut flowers. Research on vase solutions has become a concentrated area in current studies on cut flower preservation. Multi-walled carbon nanotubes (MWCNTs), as a type of carbon nanomaterial with bactericidal and membrane-penetrating properties, can be used as a component in vase solutions. This supplementation of energy substances aims to improve antioxidant enzyme activity, thereby enhancing the postharvest quality of cut chrysanthemums. In this study, deionized water and a standard preservative solution were employed as control groups to compare the effects of MWCNTs applied at different concentrations, combined with common preservatives such as sugar and 8-hydroxyquinoline, on the postharvest flowering and preservation of Chrysanthemum × morifolium ‘Jinba’. By observing the distribution of MWCNTs in the tissues surrounding the cut and changes in water content, carbon sources, osmoregulatory substance levels, and the expression of relevant key genes, a formulation with excellent postharvest treatment effects was identified. Preliminary investigations into its action and mechanism were also conducted. The results indicated that the combined treatment with 5 mg L−1 MWCNTs, 30 g L−1 sucrose, and 0.2 g L−1 8-hydroxyquinoline effectively promoted water and sugar uptake in chrysanthemum flowers, accelerating bud opening, maintaining larger inflorescence diameter, and extending the vase life. Ultimately, this enhanced the ornamental value of cut chrysanthemums. These research findings provide theoretical and experimental foundations for the application of multi-walled carbon nanotubes as auxiliary additives to improve the ornamental quality of cut flowers.

Fabrication of an amino-modified MWCNTs grafted with chlorosulfonated PMIA nanofibrous membrane via electrospinning for efficient high-temperature dust filtration

The development of nanofibrous membrane with exceptional filtration efficiency, excellent mechanical properties, and high-temperature resistance poses a significant challenge in the field of industrial dust removal. Incorporating multi-walled carbon nanotubes (MWCNTs) into poly(m-phenylene isophthalamide) PMIA enhances the mechanical properties of nanofibrous membrane fabricated via electrospinning. However, the application of MWCNTs is limited due to their poor dispersion and self-aggregation in solvents. Herein, amino-modified MWCNTs (MWCNTs-NH2) grafted with chlorosulfonated PMIA (PMIA-SO2Cl) nanofibrous membrane was fabricated via electrospinning. The results demonstrated that the coupling effect of PMIA-SO2Cl and MWCNTs-NH2 significantly enhanced the stability of MWCNTs in the PMIA electrospinning solution, resulting in a more homogeneous dispersion of MWCNTs and a smaller average particle size (D50 = 198.03 nm). The filtration efficiency of the most penetrating particle size (MPPS) and the tensile strength of PMIA-SO2Cl/MWCNTs-NH2 nanofibrous membrane were 99.990 % and 57.514 MPa, respectively. The tensile strength retention rates in 30 wt% H2SO4 and 10 wt% NaOH were 52.56 % and 80.25 %, respectively. The MWCNTs-NH2/PMIA-SO2Cl nanofibrous membrane exhibited significantly enhanced mechanical property, filtration efficiency and high-temperature resistance (approximately 250 °C) compared to the unmodified nanofibrous membranes. This study was instructive for the application of electrospinning nanofibrous membranes in the field of high-temperature dust removal.

Alignment of multiwalled carbon nanotubes‐reinforced epoxy by a novel shear assisted method in the presence of the electric field

AbstractThe application of multiwall carbon nanotubes (MWCNTs) alignment associated with external field techniques is fairly limited in the industry due to the cost implications of scaling such external fields. To address this problem, a new shear‐assisted method is introduced to increase the effectiveness of MWCNTs alignment techniques using electric field. In addition, the effect of curing temperature of polymer in CNT‐reinforced nanocomposites, is studied on the alignment of MWCNTs using our novel shear‐assisted technique. The results show that increasing the temperature during the curing process of the polymer can help with the alignment of MWCNTs using our shear‐assisted technique. This may be attributed to lower gel‐time of polymer matrix at high temperatures that can prevent agglomeration of the MWCNTs in the matrix. Moreover, fractography of reinforced composites has been studied by scanning electron microscopy to investigate the effects of curing temperature on the alignment of MWCNTs in the epoxy matrix.

The application of multi-walled carbon nanotubes modified pencil graphite electrode for voltammetric determination of favipiravir used in COVID-19 treatment.

This study describes the first application of an improved procedure on a pencil graphite electrode decorated with functionalized multi-walled carbon nanotubes (f-MWCNTs/PGE) for the determination of the COVID-19 antiviral drug, favipiravir (FVP). The electrochemical behavior of FVP at f-MWCNTs/PGE was examined by cyclic voltammetry and differential pulse voltammetry (DPV) methods, and it was noted that the voltammetric response significantly increased with the modification of f -MWCNTs to the surface. The linear range and limit of detection from DPV studies were determined as 1–1500 µM and 0.27 µM, respectively. In addition, the selectivity of the method was tested toward potential interferences, which can be present in pharmaceutical and biological samples, and it was found that f-MWCNTs/PGE showed high selectivity for the determination of FVP in the presence of probable interferences. The results with high accuracies and precisions from the obtained feasibility studies also revealed that the designed procedure can be used for accurate and selective voltammetric determination of FVP in real samples.

Application of multi-walled carbon nanotubes functionalized with hemin to evaluate the electrochemical behavior of nitrofurazone in aqueous media

A sensor based on a carbon glassy electrode modified with hemin complex and multi-walled carbon nanotubes (MWCNT) was developed as an alternative technique to evaluate the behavior electrochemical of nitrofurazone (NF). This modified electrode showed only one irreversible diffusion-controlled cathodic process in acidic medium, involving four electrons for the hydroxylamine derivative formation with 90 mV potential anticipation and current peak 45 times higher when compared to the bare glassy carbon electrode, GCE. From pH > 9, the NF reduction to hydroxylamine derivative occurred in two steps, being the first one associated to the nitro-anion radical formation in one-electron reversible process. In this case, the reduction potential referring to the radical was anticipated in 250 mV and the peak currents were approximately 13 times higher for sensor modified than those for GCE. The molecular O2 was confirmed as the best radical scavengers against the glutathione and cysteine and it was 4 times more stable on modified sensor than on the GCE.

Inflammatory Genes Associated with Pristine Multi-Walled Carbon Nanotubes-Induced Toxicity in Ocular Cells.

The wide application of multi-walled carbon nanotubes (MWCNTs) in various fields has raised enormous concerns regarding their safety for humans. However, studies on the toxicity of MWCNTs to the eye are rare and potential molecular mechanisms are completely lacking. This study was to evaluate the adverse effects and toxic mechanisms of MWCNTs on human ocular cells. Human retinal pigment epithelial cells (ARPE-19) were treated with pristine MWCNTs (7-11 nm) (0, 25, 50, 100 or 200 μg/mL) for 24 hours. MWCNTs uptake into ARPE-19 cells was examined using transmission electron microscopy (TEM). The cytotoxicity was evaluated by CCK-8 assay. The death cells were detected by Annexin V-FITC/PI assay. RNA profiles in MWCNT-exposed and non-exposed cells (n = 3) were analyzed using RNA-sequencing. The differentially expressed genes (DEGs) were identified through the DESeq2 method and hub of which were filtered by weighted gene co-expression, protein-protein interaction (PPI) and lncRNA-mRNA co-expression network analyses. The mRNA and protein expression levels of crucial genes were verified using quantitative polymerase chain reaction (qPCR), colorimetric analysis, ELISA and Western blotting. The toxicity and mechanisms of MWCNTs were also validated in human corneal epithelial cells (HCE-T). TEM analysis indicated the internalization of MWCNTs into ARPE-19 cells to cause cell damage. Compared with untreated ARPE-19 cells, those exposed to MWCNTs exhibited significantly decreased cell viabilities in a dose-dependent manner. The percentages of apoptotic (early, Annexin V positive; late, Annexin V and PI positive) and necrotic (PI positive) cells were significantly increased after exposure to IC50 concentration (100 μg/mL). A total of 703 genes were identified as DEGs; 254 and 56 of them were, respectively, included in darkorange2 and brown1 modules that were significantly associated with MWCNT exposure. Inflammation-related genes (including CXCL8, MMP1, CASP3, FOS, CXCL2 and IL11) were screened as hub genes by calculating the topological characteristics of genes in the PPI network. Two dysregulated long non-coding RNAs (LUCAT1 and SCAT8) were shown to regulate these inflammation-related genes in the co-expression network. The mRNA levels of all eight genes were confirmed to be upregulated, while caspase-3 activity and the release of CXCL8, MMP1, CXCL2, IL11 and FOS proteins were demonstrated to be increased in MWCNT-treated ARPE-19 cells. MWCNTs exposure also can induce cytotoxicity and increase the caspase-3 activity and the expression of LUCAT1, MMP1, CXCL2, and IL11 mRNA and protein in HCE-T cells. Our study provides promising biomarkers for monitoring MWCNT-induced eye disorders and targets for developing preventive and therapeutic strategies.

Exogenous Application of Multi-Walled Carbon Nanotubes (MWCNTs) and Nano-Selenium (Nano-Se) Alleviated the PEG-Induced Water Deficit Stress and Improved the Crop Performance of Camelina

While previous studies have shown camelina drought tolerance relative to other oilseed crops, drought has been documented to severely influence the productivity of camelina. To date, little information is available on the drought tolerance of camelina genotypes. This study was conducted to evaluate drought tolerance in fifteen camelina genotypes and test the alleviative effect of nanoparticles on PEG-induced water deficit stress (WDS) at the whole-plant level at the Yangzhou University Pratacultural Science Experimental Station in September 2021. Four different degrees of WDS were induced by a range of PEG solution concentrations (0, 16.7, 25.0, 37.5, and 56.3 mM). A petri dish study determined that CamK8 and CamK9 (GR50 = 19.0 and 34.3 mM, respectively) were the most sensitive and tolerant genotypes, respectively, to PEG-induced WDS. Results from the whole-plant test showed that the foliar application of MWCNTs (dose: 50 or 100 mg L−1) or nano-Se (dose: 5 or 10 mg L−1) alleviated the adverse effect of PEG-induced WDS, and increased the camelina plant height (ranges: 51.1–56.3 cm) and crop yield (ranges: 0.11–0.14 g plant−1) compared with untreated control and PEG-treated plants (height: 43.5–56.9 cm; yield: 0.06–0.12 g plant−1) in CamK8 without affecting the principal fatty acid composition and groups in camelina oil. The results of this study demonstrated that applying MWCNTs or nano-Se could alleviate WDS and maintain seed yield in camelina, providing the possibility of using these nanoparticles to manage WDS in agricultural practices.

High-Temperature-Annealed Multi-Walled Carbon Nanotubes as High-Performance Conductive Agents for LiNi0.5Co0.2Mn0.3O2 Lithium-Ion Batteries

In this work, the high yield of MWNTs was prepared by chemical vapor deposition (CVD) method, followed by annealing at 2000–2800 °C, and the effects of high annealing temperature on metal impurities and defects in multi-walled carbon nanotubes (MWNTs) was explored. Furthermore, the annealed MWNTs were dispersed using a sand mill to make a conductive slurry, and finally the cathode LiNi0.5Co0.2Mn0.3O2 was added to the assembled batteries, and the application of MWNTs (slurry) as conductive agents in LiNi0.5Co0.2Mn0.3O2 (NCM) cathode materials by sand-mill dispersion on the performance of lithium-ion batteries was investigated. The results indicate that high temperature annealing can effectively remove the residual metal impurities from MWNTs and the defects in MWNTs gradually decreases as the temperature rises. In addition, 2 wt% of MWNTs (slurry) in LiNi0.5Co0.2Mn0.3O2 is sufficient to form an electronically conductive network; as a result, the electronic conductivity and the high rates performance of the LiNi0.5Co0.2Mn0.3O2 batteries were greatly improved. The LiNi0.5Co0.2Mn0.3O2 battery with MWNTs slurries annealed at 2200 ℃ as a conductive additive displays the highest initial discharge capacity of 173.16 mAh·g−1 at 0.1 C. In addition, after 100 cycles, a capacity retention of 95.8% at 0.5 C and a discharge capacity of 121.75 mAh·g−1 at 5 C were observed. The multi-walled carbon nanotubes used as conductive agents in LiNi0.5Co0.2Mn0.3O2 (NCM) cathode materials show excellent battery behaviors, which would provide a new insight for the development of high-performance novel conductive agents in lithium-ion batteries.

Effect of Cellulose Material-Based Additives on Dispersibility of Carbon Nanotubes

In nanoscience, nanotechnology is applied to various technologies, and research is actively being conducted. As the application of multi-walled carbon nanotubes (MWCNTs) in various fields increases, efforts have been made to develop dispersion and functionalization technologies. In order to effectively use MWCNT nanofluids, it is most important to solve the problem of dispersion. In this study, MWCNTs were improved in dispersibility and functionalized through various chemical and mechanical treatments. In addition, MWCNTs aggregation was alleviated by using cellulose nanocrystal (CNC) as a dispersant. The processing results of MWCNTs and CNC were analyzed through transmission electron microscopy (TEM) and the dispersion was characterized by UV–Vis spectroscopy. The addition of CNC to MWCNTs has been confirmed to have high dispersibility and improved stability compared to untreated MWCNTs, and this effect affects the quality of the machine.

Pre-Harvest Application of Multi-Walled Carbon Nanotubes Improves the Antioxidant Capacity of ‘Flame Seedless’ Grapes during Storage

As a widely distributed fruit, grapes are susceptible to oxidative damage during storage and transportation, resulting in declining quality and commodity value. This study aimed to investigate the effects of preharvest application of different concentrations of multi-walled carbon nanotubes (MWCNTs) on the postharvest quality of ‘Flame Seedless’ grapes. The results showed that low-concentration (25 and 50 mg L−1) MWCNTs treatments maintained the comprehensive quality index, firmness, soluble sugar, titratable acid, pH value, and ascorbic acid (AsA) content of grapes. MWCNTs at 25 and 50 mg L−1 increased the activities of peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), and ascorbic acid (APX). Furthermore, MWCNTs reduced the malondialdehyde (MDA) content and decreased the accumulation of excessive reactive oxygen species (ROS) in grape peel and pulp tissues. In addition, transmission electron microscopy (TEM) images demonstrated that MWCNTs were absorbed by parenchymal cells in the grape peel and pulp through the epidermal cell layer. MWCNTs with a specific concentration can be used as a new inducer for the biosynthesis of antioxidants to reduce oxidative damage in grapes during storage.

Application of multi-wall carbon nanotubes supported l-proline in continuous flow catalysis

l-proline on multi-wall carbon nanotubes (l-proline/MWCNTs) catalysts doped with suitable auxiliary support materials are successfully applied in the continuous flow catalytic syntheses, including Aldol reaction, Mannich reaction and Knoevenagel condensation reaction. With the advantages of easy operation, high efficiency and excellent stability, this method is promising in large-scale synthesis.

Experimental investigations on the thermal performance and phase change hysteresis of low-temperature paraffin/MWCNTs/SDBS nanocomposite via dynamic DSC method

Benefitting from high storage density, phase change material (PCM) has been widely utilized in cold chain logistics. However, the phase change process of composites is normally non-isothermal, which will lead to phase change hysteresis (PCH). The exploration of the mechanism and influence factors of PCH remains a huge challenge. In this paper, a nanocomposite PCM (NCPCM) based on paraffin (PA) was prepared to address this issue via the two-step method. Here, the applications of multi-walled carbon nanotubes (MWCNTs) and sodium dodecylbenzene sulfonate (SDBS) were contributed to the enhancement of thermal conductivity and suspension stability. Subsequently, after various characterization techniques, the results showed that thermal conductivity of the NCPCM with 1.0 wt% MWCNTs and a 2:1 mass ratio of MWCNTs and SDBS increased by 1.86 times. Moreover, the NCPCM exhibited high thermal charging-discharging efficiency, thermal stability, and cyclic stability. More importantly, the PCH has been studied via the dynamic differential scanning calorimetry (DSC) method. The effects of temperature range, temperature changing rate, and sample mass on the hysteresis degree were investigated. Furthermore, the PCH was interpreted in terms of energy storage, temperature delay, internal thermal resistance, crystallinity, and interfacial free energy. It was proved that the NCPCM possesses a smaller hysteresis degree when the temperature range was −40–50 °C, temperature changing rate was 10 K min−1, and sample mass was within 10 mg.

V2O5, CeO2 and Their MWCNTs Nanocomposites Modified for the Removal of Kerosene from Water

In this paper, the application of multiwalled carbon nanotubes (MWCNTs) based on metal oxide nanocomposites as adsorbents for the removal of hydrocarbons such as kerosene from water was investigated. Functionalized MWCNTs were obtained by chemical oxidation using concentrated sulfuric and nitric acids. V2O5, CeO2, and V2O5:CeO2 nanocomposites were prepared using the hydrothermal method followed by deposition of these oxides over MWCNTs. Individual and mixed metal oxides, fresh MWCNTs, and metal oxide nanoparticle-doped MWCNTs using different analysis techniques were characterized. XRD, TEM, SEM, EDX, AFM, Raman, TG/DTA, and BET techniques were used to determine the structure as well as chemical and morphological properties of the newly prepared adsorbents. Fresh MWCNTs, Ce/MWCNTs, V/MWCNTs, and V:Ce/MWCNTs were applied for the removal of kerosene from a model solution of water. GC analysis indicated that high kerosene removal efficiency (85%) and adsorption capacity (4270 mg/g) after 60 min of treatment were obtained over V:Ce/MWCNTs in comparison with fresh MWCNTs, Ce/MWCNTs and V/MWCNTs. The kinetic data were analyzed using the pseudo-first order, pseudo-second order, and intra-particle diffusion rate equations.

Chain-ring covalently interconnected cellulose nanofiber/MWCNT aerogel for supercapacitors and sensors.

Bending multi-walled carbon nanotubes (MWCNTs) into rings and structuring them into aerogels is difficult. In this study, cellulose nanofiber (CNF)-MWCNT composite fibers with chain-ring structures were prepared by covalently interconnecting carboxylated CNF and aminated MWCNT by dehydration condensation, solving the problems of the formation of MWCNT aerogels and their phase separation during the compounding process and providing CNF-based aerogels with electrical conductivity. The covalently interconnected aerogels (CAs) had hierarchical porous structures with mechanical resilience and chain-ring fibers, which drove the CNF and MWCNT to form a continuous homogeneous network resulting in a high compression resistance of 269.02 kPa. The CA-based flexible all-solid-state supercapacitor had a quality specific capacitance of 114.8 F g-1, a capacitance retention rate of 94.78% and a Coulomb efficiency of 100%. The CA-based flexible sensor can sense different pressures with a stable response for 1000 cycles. This first study of pulling and bending MWCNT through CNF is expected to inspire more applications of MWCNTs in the fields of flexible supercapacitors and sensors.

When nanoparticle and microbes meet: The effect of multi-walled carbon nanotubes on microbial community and nutrient cycling in hyperaccumulator system

Carbon nanotubes can potentially stimulate phytoremediation of heavy metal contaminated soil by promoting plant biomass and root growth. Yet, the regulating mechanism of carbon nanotubes on the rhizosphere microenvironment and their potential ecological risks remain poorly characterized. The purpose of this study was to systematically evaluate the effects of multi-walled carbon nanotubes (MCNT) on the diversity and structure of rhizosphere soil bacterial and fungal communities, as well as soil enzyme activities and nutrients, in Solanum nigrum L. (S. nigrum)-soil system. Here, S. nigrum were cultivated in heavy metal(loid)s contaminated soils applied with MCNT (100, 500, and 1000 mg kg-1 by concentration, none MCNT addition as control) for 60 days. Our results demonstrated more significant urease, sucrase, and acid phosphatase activities in MCNT than in control soils, which benefit to promoting plant growth. Also, there were significant reductions in available nitrogen and available potassium contents with the treatment of MCNT, while the organic carbon and available phosphorus were not affected by MCNT application. Notably, the alpha diversity of bacterial and fungal communities in the MCNT treatments did not significantly vary relative to control. However, the soil microbial taxonomic compositions were changed under the application of MCNT. Compared to the control, MCNT application increased the relative abundances of the Micrococcaceae family, Solirubrobacteraceae family, and Conexibacter genus, which were positively correlated with plant growth. In addition, the non-metric multidimensional scaling (NMDS) analysis revealed that the community structure of bacterial and fungal communities did not significantly change among all the treatments, and bacterial community structure was significantly correlated with soil organic carbon. At the same time, sucrase activity had the highest relation to fungal community structure. This study highlighted soil microbes have strong resistance and adaptation ability to carbon nanotubes with existence of plants, and revealed linkage between the rhizosphere microenvironment and plant growth, which well improved our understanding of carbon nanotubes in heavy metal phytoremediation.

A Novel Glassy Carbon Electrode Modified with Multi-Walled Carbon Nanotubes for Potentiometric Xipamide Determination

Solid contact electrodes are widely used in analytical fields due to their outstanding performance over classical ones. However, they showed formation of a water layer affecting stability of those electrodes’ type. Herein, we develop a solid contact ion selective electrode to overcome this common drawback through application of multi-walled carbon nanotubes as a hydrophobic layer between the ion sensing membrane and a glassy carbon electrode. This fine modification improved stability of the electrode via preventing the formation of this water layer. The obtained potential was steady over 30 days with a drift of ∼0.8 mV h−1. The MWCNTs-modified electrode was used for determination of xipamide with a Nernstian slope of −56.01 over a linearity range of 1.0 × 10−5–1.0 × 10−2 mol l−1 and detection limit of 6.0 × 10−6 mol l−1. The proposed sensor was effectively applied for determination of the cited drug in its marketed pharmaceutical dosage form and spiked human plasma.

Seed Priming with Multiwall Carbon Nanotubes (MWCNTs) Modulates Seed Germination and Early Growth of Maize Under Cadmium (Cd) Toxicity

Application of multiwall carbon nanotubes (MWCNTs) could have promotive effects on crop plants; however, their effects on seed germination and early growth of maize under cadmium (Cd) stress have rarely been investigated. A pot experiment was conducted with two maize varieties, Yuebaitiannuo7 and Yuecainuo2, grown under three Cd levels, i.e., 0, 100, and 200 mg L−1 (denoted as Cd0, Cd100, and Cd200, respectively) and three MWCNT levels, i.e., 0, 100, and 200 mg L−1 (denoted as M0, M100, and M200, respectively) as seed priming treatments to assess the MWCNT-induced modulations in seed germination rate, seedling growth, and related physio-biochemical attributes under Cd stress. Yuebaitiannuo7 showed higher seed germination rate and less root and shoot growth than Yuecainuo2. The MWCNT application promoted the seed germination rate of Yuecainuo2 by 11.42% at M100 and 24.76% at M200 under Cd100 at 4 days after sowing; however, these effects remained non-significant for Yuebaitiannuo7. Moreover, the MWCNTs enhanced root and shoot fresh weight and antioxidant enzyme activities, including peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) activities, and reduced the malonaldehyde (MDA) content under Cd across MWCNT treatments. Nevertheless, the toxic effects were also observed, indicating a potential risk posed by MWCNTs at high concentrations. Application of MWCNTs alleviated the Cd toxicity in growing maize plants; however, their effects were concentration dependent. Yuecainuo2 performed better than Yuebaitiannuo7 with the application of MWCNT under Cd stress.

Multi-walled carbon nanotube-based nanobiosensor for the detection of cadmium in water

Industrial and agricultural processes have led to the prevalence of cadmium in the ecosystem. A successive build-up of cadmium in food and drinking water can result in inadvertent consumption of hazardous concentrations. Such environmental contamination of cadmium can pose a substantial threat to human and animal life. In humans, it is known to cause hypertension, cardiovascular diseases, DNA lesions, inhibition of DNA repair protein or disturb the functioning of lung, liver, prostate and kidney. The development of a reliable method for Cd (II) ions detection would reduce the exposure and complement existing conventional methods. In this study, a DNA based electrochemical method is employed for the detection of Cd (II) ions using ethyl green (EG) and multi-walled carbon nanotube (MWCNT). Glassy carbon electrode (GCE)/MWCNT forms the working electrode for differential pulse voltammetry (DPV) analysis for the detection of Cd (II) ions. The dsDNA is immobilized onto the working electrode. The indicator dye EG, preferably binds to ssDNA and its reduction peak current is noticeably less in the presence of dsDNA. The Cd (II) ions after interacting with dsDNA, unwinds the dsDNA to ssDNA, upon which the EG molecules bind to ssDNAs, giving a higher reduction peak current. The difference in the reduction peak currents in the presence and absence of Cd (II) ions is proportional to its concentration. The linear detection range achieved in this method is 2 nM–10.0 nM with a sensitivity of around 5 nA nM−1 and the limit of detection is 2 nM, which is less than the permissible limit of WHO for human exposure. This study considerably broadens the possible application of multi-walled carbon nanotube modified electrodes as biosensors and holds prospects for the detection of other heavy metals in environmental samples.

In Vitro Biocompatibility Test of Multiwall Carbon Nanotubes with Human Osteoblast Cells: Potential Application for Bone Implant Interface Reinforcement.

Application of multiwall carbon nanotubes (MWCNT) as a filler component in composite materials can lead to remarkable increase in mechanical strength. It is a challenging application to form a living bone tissue biocomposite that is reinforced with MWCNTs at a dental implant-bone interface. The successful biointegration of MWCNT and the implant material depends on the processes of osseointegration, namely surface interactions at the molecular and cellular level. In this work the compatibility of MWCNT with main osseointegration processes has been overviewed with special attention to the toxicity of MWCNT for interacting human cells, and In Vitro experiments were performed with primary human osteoblast cells. The cells were isolated from oral bone fragments and grown in cell culture conditions. Plate wells were covered with MWCNT layers of three different densities. Osteoblast cell suspensions were placed onto the MWCNT layers and into empty plate wells. 24 and 72 hours after seeding the attachment and proliferation of cells was evaluated using Thiazolyl Blue Tetrazolium Bromide (MTT) colorimetric assay. The extent of cell death was characterized by Lactate Dehydrogenase (LDH) assay. The osteoblast cell viability tests show that cells were attached to all investigated surfaces, but with lower rate to higher density MWCNTs. A low level of cell death was observed in each sample type. Phase contrast and fluorescent microscopic observations show that although MWCNTs are not toxic for human primary osteoblast cells, an intense interaction of the cells with MWCNTs reduces their proliferation and markedly affects their morphology.

Preparation of diameter-controlled free-standing MWCNT membranes and their application for dye adsorption.

The synthesis of multi-walled carbon nanotubes (MWCNTs) was carried out over different Ni-loaded metallic oxide catalyst nanoparticles and under different reduction times to control the outside diameter of the nanotubes. Moreover, high-purity, free-standing membranes were fabricated by a simple filtration of the as-grown MWCNTs. Furthermore, the dye-adsorption properties of the nanotubes depended on the diameter of the carbon nanotubes (CNTs). The adsorption isotherms and kinetics of anionic dyes could be described by Freundlich and pseudo-second-order models, respectively. Thermodynamic studies suggested that the adsorption processes were spontaneous and exothermic. This work provides new insights into the synthesis and application of MWCNTs with the selective adsorption properties of carbon-based materials for the removal of organic dyes.