Pure Multi-walled Carbon Nanotubes Research Articles

A highly stable, accurate and fast photo-response in visible region: Role of introducing Ta2O5 /MWCNTs heterostructures in photodetector

This work presents the development of a novel photodetector design that leverages the synergistic combination of tantalum pentoxide (Ta2O5) and multi-walled carbon nanotubes (MWCNTs) to achieve superior visible light detection performance. Ta2O5/MWCNT heterostructures were synthesized and comprehensively characterized using various techniques. Structural, morphological, and optical analyses confirmed the suitability of these heterostructures for the targeted application. Photoluminescence spectroscopy was further employed to meticulously assess defect levels, which play a crucial role in photodetector performance. The photodetectors were fabricated using pure Ta2O5, pure MWCNTs, and the synthesized Ta2O5/MWCNT heterostructures. When subjected to different illumination wavelengths and voltages, the Ta2O5/MWCNT devices demonstrated significantly enhanced visible light detection and photocurrent compared to their individual counterparts. The measured responsivity, detectivity, and quantum efficiency of the Ta2O5/MWCNT photodetectors were highly impressive, reaching 81 mA/W, 16.38 × 106 Jones and 15.5 %, respectively. Critically, the fabricated photodetectors exhibited exceptional stability with rapid response times, characterized by an 80-ms rise and recovery cycle. This fast response characteristic underscores the potential of Ta2O5/MWCNT photodetectors in applications demanding high-speed and precise optical signal detection, such as those found in the fields of optical communication, sensing, and imaging.

The effects of Multiwalled Carbon Nanotube to the performance of a refrigeration system

By incorporating nanofluid technology and nanolubricants into compressors, the performance can be enhanced while also lowering worldwide fuel consumption and aiming at developing cleaner, more efficient energy sources and uses. The globe is being confronted with energy security issues and heating, cooling and HVAC systems highly contribute to it. Hence, it is critical to save energy and improve the efficiency of the refrigeration cycle. This study presents experimental and theoretical findings in order to investigate the effect of Polyester (POE)-oil based multiwalled Carbon Nanotube (MWCNT) nanolubricant on the Coefficient of Performance (COP) of a refrigeration system. The objectives of this study is to analyze the stability of MWCNT nanofluids, to obtain the COP of a refrigeration cycle run with pure POE oil and MWCNT nanofluids with different concentrations respectively. The experiment was conducted by preparing 0.55, 0.65 and 0.70 g/l MWCNT nanofluid by using the two step method. The most effective concentration used in the refrigeration system was referred to the one that resulted in the highest COP. It was determined from the experiment that 0.55 g/l MWCNT nanofluid resulted in a higher COP of 5.766 as compared to the other two concentrations. Besides, it showed an improvement of 34.6% in COP as compared to the COP of using pure POE oil in the refrigeration system, which was found to be 4.285. The 0.65 g/l and 0.70 g/l concentration of MWCNT resulted in a COP of 5.618 and 5.617, respectively. The compressor work was also analyzed and was found to be reduced noticeably after adding MWCNT nanoparticles. Hence it can be concluded that the increment of MWCNT concentration in nanofluids increases the COP of the refrigeration system but only up to a certain limit of concentration.

Arc Discharge Synthesis and Multistep Purification of Multiwall Carbon Nanotubes

This research work describes the cost-effective synthesis and purification of multiwall carbon nanotubes (MWCNTs). Synthesis of CNTs was carried out in distilled water between two electrodes using the electric arc discharge (EAD) method. EAD is a simple and straightforward route in which an electric arc is generated between graphite electrodes through DC power source to produce soot which contains MWCNTs along with impurities. The deposited soot containing MWCNTs was then chipped off and purified. In this case, multistep purification scheme was opted to remove unwanted impurities from produced MWCNTs. Purification route comprised thermal treatment, chemical treatment and a combination of both to yield pure MWCNTs. Thermal treatments were carried out in normal air and under controlled flow of oxygen at different temperatures whereas chemical treatment was performed using acidic solution. Thermo gravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) were carried out before and after purification treatments to investigate the outcome of employed treatments. Results showed that the thermal or chemical treatment alone is not sufficient to remove impurities from soot. Moreover, the introduction of an oxide group through chemical treatment reduces the oxidization temperature of graphitic particles. It was found that the chemical treatment followed by thermal annealing under the controlled flow of oxygen is the most appropriate method for successful purification of MWCNTs synthesized via EAD method.

PVDF/poly(3-methylthiophene)/MWCNT nanocomposites for EMI shielding in the microwave range

This work presents a new approach to enhance EMI shielding efficiency of nanocomposites of dielectric polymers, multiwalled carbon nanotubes (MWCNTs) and intrinsically conducting polymers for account of using core-shell morphology for conducting components. To realize this approach new ternary nanocomposites of poly(vinylidene fluoride) (PVDF), MWCNTs and poly(3-methylthiophene) doped by Cl− anions (P3MT) were prepared through synthesis of thermally stable core/shell nanocomposites PVDF/P3MT and MWCNT/P3MT. These binary nanocomposites were mixed with pure MWCNTs or PVDF followed by compression molding to prepare the ternary nanocomposites of different morphology to discriminate their EMI shielding properties in a wide frequency range (1–67 GHz). Values of the tangent of dielectric loss angle, the efficiency of transmission, reflection and absorption of microwave radiation, and shielding efficiency (SE) of the specified materials were found from analysis of spectral dependences of their complex dielectric constants. It was shown that while the melt mixing of the binary PVDF/P3MT nanocomposite with MWCNTs both in a pure state and in the binary nanocomposite (MWCNT/P3MT) expectedly strongly enhances SE of the former, this effect is non-linear and depends on presence/absence of the P3MT shell on the MWCNT core. The ternary nanocomposite PVDF/P3MT/MWCNT made of the binary polymer-polymer nanocomposite PVDF/P3MT and pure MWCNTs showed highest SE values at the frequencies above 4.5 GHz up to 68.4 dB at 67 GHz in the case of the 1 mm thickness sample. However, below 4.5 GHz the SE was higher in the case of the ternary nanocomposites containing core/shell MWCNT/P3MT nanocomposite instead of pure MWCNT.

Investigation of the visible-light-driven catalytic activity of nickel oxide-doped carbon nanotubes/polyvinylpyrrolidone nanocomposites towards methylene blue dye

In this study, multi-wall carbon nanotubes (MWCNTs) were wrapped with polyvinylpyrrolidone (PVP) followed by decoration with nickel oxide (NiO) nanoparticles. The composite ofMWCNTs/PVP exhibited an improved capacity for absorbing visible light in comparison to both pristine PVP and MWCNTs alone. Significantly, the ternary nanocomposite of NiO-doped MWCNTs/PVP demonstrated exceptional light absorption in the visible range (400–650 nm). Regarding XRD results, in the PVP pattern, a broad peak at 2θ = 20° implies its semi-crystalline structure. NiO displays diffraction peaks corresponding to the (111), (200), and (220) planes, verifying its crystallinity. Pure MWCNTs exhibit a strong peak at 2θ = 25.62° for the (002) plane, consistent with graphene structure. The MWCNTs/PVP/NiO sample was confirmed by the existence of characteristic peaks for all three components, which indicates successful formation of the triple nanocomposite. The morphological study by FESEM showed that MWCNTs possess diverse nanotube lengths and diameters with concentric graphene layers. In addition, NiO nanoparticles exhibited a uniform, spherical shape with a nanoscale diameter. Finally, the MWCNTs/PVP/NiO sample showed shorter MWCNTs dispersed in a PVP matrix with incorporated NiO nanoparticles. The photodegradation test revealed that pristine MWCNTs show limited photocatalytic performance, while MWCNTs/PVP and MWCNTs/PVP/NiO notably improve dye degradation. The inclusion of NiO nanoparticles, known for their high surface area and light absorption capacity, led to superior methylene blue degradation, underlining their efficacy as photocatalysts.

Dynamic crack growth propagation of Al 2024 thin plates reinforced with carbon nanotube subjected to non-proportional cycling loading

In this study, the dynamics crack growth in a thin plate made of aluminum alloy 2024T3, which was coated with two types of coating, electrocoating (Ni-CNTs) and electroless coating (Ni-CNTs), were investigated under a non-proportional cyclic loading. Pure multi-walled carbon nanotubes (MWCNTs) were added to the coating solution at a concentration of 2 g/l to enhance the mechanical properties and study the effect of adding carbon nanotubes to the coating solution.Fracture mechanics analysis was performed using two methods. First, a novel apparatus was designed for experimental analysis of the application of a non-proportional cyclic loading, consisting of a repeated, cyclic inplane shear stress with constant tension stress. Secondly, the numerical analysis was carried out using ABAQUS 2019 programming to obtain numerical results and compare them with the experimental results to validate the study. Paris law parameters, including Paris law constants c and m, K (change in stress intensity factor), and da/dN (crack growth per cycle), which were included in the ABAQUS software to simulate the model and compare the results with the experimental data.The specimens were analyzed using XRD, FESEM, and EDXRF after the coating process to determine the quality, distribution, and thickness of the coating layer on the specimen's surface. The hardness tests showed a 57% increase in the hardness of the specimens coated with electrocoating and a 72% increase in the hardness of specimens coated with electroless coating. The Young's modulus also showed an increase of 37.5% for specimens coated with electrocoating and 50% for specimens coated with electroless coating, compared to specimens without coating.

Ionic Liquids Modified CNTs and Graphene as Additives in Vegetable Lubricating Oil: A Route for Sustainable Tribology

The multi-walled carbon nanotubes (MWCNTs) and graphene oxide (GO) were covalently functionalised with imidazolium salt-based ionic liquids. The acid chloride-functionalised MWCNTs and GO were coupled with 1-(3-aminopropyl) imidazole, and then the products were reacted with 1-bromobutane. The bromine anions were exchanged with PF6− and NTf2−. The phase transformation of the MWCNTs was observed after the functionalisation with 1-(3-aminopropyl) imidazole. The black solids were transformed into black liquids, suggesting the imidazolium was chemically grafted onto the MWCNTs. FTIR, XPS, and TGA analyses confirmed the covalent modification and formation of imidazolium salts. SEM and AFM images showed no visual change between the pristine MWCNTs and the functionalised MWCNTs, indicating that the modification processes did not destroy the structural integrity. The solubility of the functionalised MWCNTs with different anions in water was analysed. It was found that hydrophobicity followed the order: NTf2− > PF6− > Br−. The functionalised MWCNTs and GO were employed as additives in vegetable oil at 1 wt.% concentration and the tribological properties were evaluated in a four-ball machine. It was found that vegetable oil with functionalised MWCNTs showed better lubrication performance than pure MWCNTs.

Carbon nanotube films embedded with Cu@C nanocubes for electromagnetic interference shielding

AbstractFlexible carbon tube films for electromagnetic interference (EMI) shielding are assembled by mixing the well‐aligned Cu@C core‐shell nanocubes with multi‐walled carbon nanotubes (MWCNTs). The Cu@C core‐shell nanocubes are achieved by the thermal pyrolysis of polyvinylpyrrolidone (PVP) coating on Cu2O nanocubes. With the optimal PVP concentration of 1.5 mg/mL, the Cu@C/MWCNTs composite film with ultra‐thin thickness (52.2 μm) displays good conductivity of 12.5 S cm−1 and excellent specific EMI shielding value of 510.73 dB mm−1, which is higher than the pure MWCNTs film (439.50 dB mm−1) under the same weight condition. Moreover, the 1.5 mg/mL‐Cu@C/MWCNTs composite film exhibits highly mechanical repeatability after being bended for 10,000 cycles. The carbon layers protecting metal nanoparticles can partly replace precious carbon nanotubes to construction highly flexible composite film with anticipated electrical conductivity, which have a good application prospect for thin, lightweight and flexible EMI shielding fields.

Effect of Diameter of Carbon Nanotubes in Nanocomposite Membrane for Methyl Orange Dye Removal

It is worth noticing that structure of nanomaterials affects the membrane performance, however, the effect of diameter of multiwalled carbon nanotubes (MWCNTs) has not been discussed in the past. This research aims to investigate the effect of diameter of MWCNTs on the performance of graphene oxide (GO)/ MWCNTs nanocomposite membrane for methyl orange dye removal. MWCNTs with different diameters (12-15 nm, 30-50 nm) with the same length (< 10 µm) are used to synthesize the nanocomposite membrane. The characteristics of the synthesized nanocomposite membrane were determined by surface hydrophilicity, pore size and porosity, zeta potential, and Fourier-transfer infrared (FTIR) spectroscopy. Besides, the membrane performance was evaluated by the water permeability test, dye rejection test, and antifouling test. The result showed that pure MWCNTs (30-50 nm) nanocomposite membrane (M2b) has the best performance among the synthesized membrane. The dye rejection of M2b membrane reached 86.77% and the normalized flux was approximately 0.82. Lower dye rejection (83.37%) and normalized flux (0.76) were attained by M2a membrane with smaller diameter MWCNTs (12-15 nm). This was due to M2b membrane having a smaller pore size (0.032 nm), which helped reduce the tendency of dye to pass through the membrane. Besides, M2b membrane has a more negative surface charge (-10.93 mV) that produces larger repulsion force, resulting in more dye being rejected. In conclusion, the performance of the synthesized nanocomposite membrane particularly antifouling properties can be enhanced with the addition of MWCNTs with larger diameter.

Inhalation of multi-wall carbon nanotubes changes the expression of apoptosis and cancer genes in rat brain and lungs.

One of the important issues in urban areas is air pollution which causes respiratory disorders. A significant association between exposure to inhaled particulate matter (PM), mainly ultrafine particles, and increased neurological and pulmonary morbidity and mortality was observed in some research. This study aimed to demonstrate the relation between multi-wall carbon nanotubes (MWCNTs) inhalation and the carcinogenic effect of these materials in the brain and lungs. For this purpose, we investigated gene expression in rat brain and lung tissues induced by exposure to MWCNTs. Rats were exposed to MWCNTs in diameters of 10 and 100 nm (pure and impure) at a concentration of 5 mg/m3. Exposure was done through a whole-body exposure chamber for 5 h/day, 5 days/week for 14 days. After exposure, both brain and lung tissues were isolated to evaluate certain gene expressions including Bax, Bcl2, Rac1, Tp53, Mmp12, and Arc. The results showed that exposure to impure and pure MWCNTs (10 and 100 nm) at a concentration of 5 mg/m3 causes up-regulation or down-regulation of some of these genes. The results suggest that impure and pure MWCNTs (10 and 100 nm) can increase the risk of central nervous system disorders such as Alzheimer's disease and increase the risk of carcinogenesis in the lung tissues of rats exposed to MWCNTs (Tab. 2, Fig. 2, Ref. 64). Text in PDF www.elis.sk Keywords: multi-wall carbon nanotube, inhalation, gene expression, carcinogenicity, brain, lung.

Fragmentation and release of pristine and functionalized carbon nanotubes from epoxy-nanocomposites during accelerated weathering.

There is an increasing volume of nano-enabled materials in the market. Once composites containing nano-additives are disposed of, weathering could deteriorate their structures, releasing nanoparticles and risking exposure of humans and aquatic organisms. Composite degradation due to environmental aging continues, including structural deterioration resulting in cracking, fragmentation, and release of microplastics and nano-additives to the environment. This research aims to study the degradation and release of initially embedded nanomaterials (NMs) from composites and their toxicity. The molecular interaction of carbon nanotube (CNT)/polymer composites is critical for modifying the polymer properties. This study investigated the interactions of functional multiwalled carbon nanotube (MWCNT) composites which affect their release during accelerated weathering processes. Different epoxy-MWCNT composites were prepared by filling a polymer with pure MWCNTs and MWCNTs functionalized with acid () and amine () groups. The physical and chemical changes of aged composites were characterized by gravimetric analysis, contact angle measurements, FTIR, SEM, and laser confocal microscopy. A loss of hydrophobicity was observed for composite surfaces long before surface cracks materialized. Released polymer fragments and nanoparticles were analyzed in wash water using TEM, FTIR and Raman spectroscopy. The environmental risks for long-term use of CNT-polymer composites and the influence of fillers on the extent of chemical photodegradation depended on the combination of polymer and fillers. If nanoparticles are released from the matrix, the high surface-to-volume ratio and reactivity of NMs make them highly dynamic in environmental systems. Exposure to these released NMs could negatively affect human health and the environment. This study provides fragmentation and CNT particle release data that could describe how molecular-level interactions between functionalized CNTs and epoxy polymers affect the aging and release of CNTs. A toxicity assessment based on a reactive oxygen species (ROS) formation assay and MTS assay for cell viability and activity of the released polymer and CNT fragments and leachate showed moderate levels of cytotoxicity of released materials as compared to pristine epoxy plates.

Rational design of nitrogen‒doped carbon nanotubes by defect engineering for Zn‒air batteries with high performance

The rational design of N‒doped multi‒walled carbon nanotubes (MWCNT) by surface engineering was performed by changing the synthetic method, the nitrogen source, and the addition of a surface defect promoter. The solvothermal (S), and the thermal treatment (TT) were used employing melamine or urea as nitrogen precursors. It was found that the activity for ORR through the TT increased in contrast to pure MWCNT and MWCNT modified by the S method. In addition, melamine allowed to obtain better activity than urea as N precursor. However, as the activity of N‒doped MWCNT was not as close to Pt/C, hydrogen peroxide as a surface‒defect promoter was added before the TT. The material obtained using melamine, the TT method, and H2O2 was employed as a highly active material for ORR, presenting onset (Eo) and half‒wave (E1/2) potentials of 0.9 and 0.77 V vs. reversible hydrogen electrode (RHE) respectively, having an activity loss of only 17% after 24 h. In the Zn‒air battery (ZAB), a cell voltage of 1.30 V was achieved, displaying a power density of 101 mW cm−2 and a specific capacity of 650 mA h g−1, being this capacity near to that obtained using Pt/C. Finally, Density Functional Theory allowed to explain how the incorporation of engineering defects and heteroatoms allowed to create a free energy state that increase the electrocatalytic activity.

Role of multi-walled carbon nanotubes as a growth regulator for Basella alba (Malabar spinach) plant and its soil microbiota

The effect of pure multi-walled carbon nanotubes (MWCNTs) was studied on the development and morphology of the Basella alba plant. The plants were treated with varying sonicated concentrations of MWCNTs. The parameters taken into consideration were germination percentage of seeds, protein content in the plant, estimation of chlorophyll concentration, and the effect on the soil microbial community after treatment with MWCNTs. A boost in vigour index was recorded with the 200 µg ml−1 concentration of MWCNTs. Increment in other parameters like protein content, chlorophyll concentration, and microbial community in soil samples have also been observed. All parameters showed higher efficiency in a concentration-dependent manner of MWCNTs compared to control by testing the significance of results through statistical one-way ANOVA analysis. The uptake of MWCNTs by plants was confirmed by SEM–EDX analysis of treated and control leaf tissue sections. This study concludes that MWCNTs exhibit significant growth effects with no toxicity to Basella alba.Graphical

Polyethylenimine embellished multiwalled carbon nanotube (MWCNTs) for efficiently enhancing sequestration of uranium(Ⅵ) from seawater

There are abundant uranium resources in seawater, and the development of low-cost and high-efficiency adsorbents for uranium extraction from seawater has high economic and environmental-friendly benefits. In this work, a polyethyleneimine modified MWCNTs adsorbent was fabricated and used for uranium capture. The prepared samples exhibited excellent removal efficiency (∼ 82.39∼96.98%) and adsorption selectivity (with a Kd ∼2.34 ×104∼1.61 ×105 mL/g) in the pH range of 4.0–8.0, which obviously superior than that of pure MWCNTs (∼ 36.16∼52.65%, Kd ∼2.83 ×103 ∼5.56 ×103 mL/g). The adsorption process followed a pseudo-second-order kinetic model, and its maximum adsorption capacity reached 97.60 mg/g. In addition, due to the existence of various chelating ligands in PEI, the specimen showed excellent adsorption performance in various interfering ions and simulated seawater. Therefore, the adsorbed samples can be easily regenerated in low-concentration hydrochloric acid solution, and the removal efficiency still reaches 85.83% after five consecutive adsorption-desorption experiments, showing fine regeneration performance. XPS analysis indicated that chelation between nitrogen- and oxygen-containing functional groups with UO22+ was the dominant removal mechanism. The excellent adsorption efficiency and regeneration performance, as well as low preparation cost and environmental friendliness, make it a potential seawater uranium sorbent.

A high-sensitivity thin-film MWNT@PDA-AgNP nanocomposite sensor for acquiring microscopic deformations

Carbon nanomaterial/polymer-based flexible strain sensors form the foundations of many cutting-edge applications, e.g., personalized health monitoring, human-machine interaction, etc. However, achieving a high sensitivity to slight deformations remains a challenging task for the existing technologies. Herein, we immobilize silver nanoparticles (AgNPs) onto the surfaces of multi-wall carbon nanotubes (MWNTs) by a polydopamine (PDA)-assisted process, in order to fabricate a new nanocomposite sensor for capturing microscopic static deformations (strain: <1%) and microscopic high-frequency vibrations (strain: <0.001%, frequency: up to 100 s kHz). The material characterizations performed show that AgNPs are compounded, in their elemental state, with the PDA nanolayers on the surfaces of MWNTs, and help to lower the potential barriers between nanofillers. As such, the tunneling of electrons across adjacent nanofillers, which underpins the sensing of slight deformations, is promoted. The proposed nanocomposite sensor demonstrates a significantly higher sensitivity to both static (gauge factor: ∼38) and dynamic deformations, than control specimens that are fabricated from pure MWNTs or PDA-coated MWNTs. Moreover, the sensitivity of the new sensor to microscopic high-frequency vibrations is positively related to the mass of the AgNPs added. This study presents a promising surface modification approach for optimizing the sensitivities of carbon nanomaterial/polymer-based strain sensors to slight deformations.

Construction of multi-walled carbon nanotubes/ZnSnO3 heterostructures for enhanced acetone sensing performance

Carbon nanotubes (CNTs) have attracted many researcher’s attention in gas sensing field because of their excellent physical and chemical properties. Herein, multi-walled carbon nanotubes (MWCNTs)/ZnSnO3 heterostructures have been obtained by a simple hydrothermal method without additional annealing process. The structural and composition information are characterized by x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). The acetone sensing properties of pure MWCNTs, ZnSnO3 and MWCNTs/ZnSnO3 heterostructures are systematically investigated, respectively. The results show that MWCNTs/ZnSnO3 heterostructures have better sensing properties compared with pure MWCNTs and ZnSnO3 sample. Specifically, MWCNTs/ZnSnO3 heterostructures exhibit not only high responses of 24.1 and rapid response/recovery speed of 1 s/9 s to 100 ppm acetone, but also relatively good repeatability and long-term stability. The enhanced sensing performance is analyzed in detail. In addition, this work provides the experimental and theory basis for synthesis of high-performance MWCNT-based chemical sensors.

Erosion resistance of ethylene propylene diene monomer insulations reinforced with precoated multi-walled carbon nanotubes

Condensed particles in the internal flow field of a solid rocket motor can cause serious erosion to thermal insulations under overload flight condition. Multi-walled carbon nanotubes (MWCNTs) can improve erosion resistance of insulations but at the cost of reduced thermal insulation performance. In this study, MWCNTs were precoated with pyrolytic carbon via chemical vapor deposition to reduce their thermal conductivity. Further, ethylene propylene diene monomer insulations reinforced with different contents of MWCNTs and precoated MWCNTs were prepared. Moreover, their ablation performances under simulated overload ablation conditions were tested and compared. Experimental results show that precoated MWCNTs can not only improve thermal insulation performance but also significantly increase particle erosion resistance of ethylene propylene diene monomer insulation materials. Charring ablation rate of the formula with 10phr precoated MWCNTs is 44.3% lower than that of basic formula and 41.6% lower than that of the formula with 3phr MWCNTs which has the same pure MWCNTs content. The char layers of MWCNTs reinforced formulas are more complete than basic formula, indicating that MWCNTs can improve char layer structure under particle erosion condition. The precoated MWCNTs can also promote the CVD reaction of pyrolysis gas in char layers during ablation, decreasing the porosity of char layers, which can increase the particle erosion resistance of insulation.

Synthesis of MWCNTs from xylenes for fabrication of highly electrically conductive and gas-sensitive polymer composites

For Multi-Walled Carbon Nanotubes (MWCNTs), high quality, purity, and low cost are very desirable. Therefore, in this reported research work, qualitative and pure MWCNTs were synthesized using a cheap and affordable carbon source-xylenes (a mixture of isomers) by the Aerosol Chemical Vapor Deposition Method (A-CVD). The high quality, purity, and homogeneity of the synthesized material have been verified by Raman spectroscopy, EDX, XRD, and SEM results. In the present study, Polystyrene/xMWCNT, Polyvinyl acetate/xMWCNT, and Polyvinyl alcohol/xMWCNT composites with different MWCNT contents of (x = 1, 2, 4, 8, and 16) wt% were prepared by an optimized technique for irreversible dispersion of MWCNTs inside polymers, which was developed by our research group. SEM analysis results revealed that the MWCNTs are well incorporated inside all three polymer matrices, and a highly dispersed distribution of MWCNTs has been obtained inside all three matrices due to this technique. Also, the electrical conductivity of the prepared composites was measured, and the prepared nanocomposites show high electrical conductivity for all concentrations of MWCNTs. Based on the maximum dispersion of MWCNTs inside the PS polymer matrix, the highest electrical conductivity is observed for this composite, which once more proves that the dispersion technique as well as the nature of the polymer play an important role in the preparation of highly electroconductive nanocomposites (1%-0.136 S/m; 2%-1.053 S/m; 4%-5.376 S/m; 8%-71.48 S/m; 16%-933.71 S/m). Comparison of electrical conductivity results of these composites with literature results demonstrates the advantages of this technique in substitution of the another dispersion methods. The nanocomposites prepared by our research group also show a sensor effect (change of resistivity) under different gases (methane, propane, carbon monoxide). It is interesting that, for analyzed gases, the resistivity of some nanocomposites increased, whereas for others it decreased. This effect can be explained by the different nature of the adsorption interaction between the analyzed gas and the polymer composite, and this depends on the chemical composition and properties of both gases and polymer matrices.

Multifunctional hybrid films from sudan III and multiwalled carbon nanotubes: electrical conduction and photoinduced molecular orientation

Multifunctional materials (MFMs) can be an important system because of their capacity to combine different properties useful for electronic devices. Multiwalled carbon nanotubes (MWCNTs) and azobenzene derivate Sudan III (SIII) are compounds with great potential to form this type of system. These compounds exhibit properties of electrical conduction and photoinduced molecular orientation, respectively, which can be combined in a single film-shaped system. In this study, we report on the fabrication and characterization of multifunctional hybrid films created from SIII mixed with MWCNTs via both Langmuir and Langmuir–Blodgett (LB) techniques. For SIII+MWCNTs monolayers obtained using the Langmuir technique, the surface pressure isotherms revealed that the aggregation process of pure SIII drives the formation of monolayers. Brewster angle microscopy of the monolayers indicated that MWCNTs form loop-shaped structures resembling rings. Such structures were not present in films of pure MWCNTs or pure SIII. The current–voltage characteristic curve showed that the films have an ohmic behavior associated to free electrons in MWCNTs, exhibiting conductivity on the order of that of semiconductors. The SIII+MWCNTs LB films exhibited a photoinduced molecular orientation determined via SIII photoisomerization. These processes, occurring in a single film, are the conceptual proof that these systems are MFMs with potential applications in developing hybrid devices.

Antibacterial and Cytotoxic Effects of Multi-Walled Carbon Nanotubes Functionalized with Iodine

The effect of multi-walled carbon nanotubes (MWCNTs) functionalized with iodine (15, 10, and 5 wt %) is studied for bacteria Escherichia coli and MCF-7 breast adenocarcinoma tumor cells. A significant increase in the antimicrobial activity of MWCNTs is obtained when they are modified with 15 and 10 wt % iodine: at concentrations of 0.1 and 0.01 g/L, the survival of bacteria was less than 2%, while for MWCNTs without iodine, the indicator was 7 and 30%, respectively. The modification of MWCNTs with 5-wt % iodine also enhances the antibacterial properties of nanotubes, but less significantly. MCF-7 cells also have the greatest cytotoxic effect on MWCNTs functionalized with 15- and 10-wt % iodine; however, unlike bacteria, the difference in the survival rates between composites and compared with pure MWCNTs was no more than 3%. Comparison of the effects of iodine in MWCNTs and pure iodine showed that functionalized MWCNTs at concentrations above 0.001 g/L are more toxic to bacteria, while pure iodine solutions are more cytotoxic to cells.