Integrity Of Multi-walled Carbon Nanotubes Research Articles

Enhancing Photovoltaic Performance with BaTiO3/MWCNTs Composite Photoelectrodes in Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have attracted renewed research interest as a potential low-cost substitute for conventional silicon photovoltaics. This work aims to improve the photovoltaic performance of the DSSCs by incorporating multi-walled carbon nanotubes (MWCNTs) into the BaTiO3 photoelectrode. The pure BaTiO3 and BaTiO3/MWCNT nanocomposites were sensitized with N719 dye and fabricated into solar cell devices for testing. The structural characterization confirmed the successful formation of the nanocomposite with an optimal dispersion at 6% of MWCNT incorporation, beyond which agglomeration effects manifested. The optical analysis verified the modulation of defect states and bandgap engineering induced by the MWCNT network. The morphological studies revealed irregular nanoparticle clusters with embedded nanotubes. Solar cell testing under AM1.5G-simulated sunlight demonstrated a peak power conversion efficiency of 4.044% for 6% of MWCNT doping, constituting a 6-fold increment versus pure BaTiO3 (0.693%). It originated from the simultaneous enhancements in the open-circuit voltage and short-circuit current enabled by the favorable band structure alterations and percolation-assisted charge transport. However, further increasing MWCNT content deteriorated the device metrics, owing to emerging limitations like trapping. The rational integration of multi-walled carbon nanotubes with lead-free ferroelectric metal oxides can contribute to the development of emerging organic-inorganic hybrid solar platforms.

Doped-MXene assists in deciphering metabolic signature of psoriasis and unraveling dysregulated leukotriene metabolism

Psoriasis, characterized by erythematous plaques, desquamation, persistent pruritus, and discomfort, significantly compromises the quality of life for afflicted individuals. The intricate interplay of immunological, genetic, and environmental factors has left the molecular intricacies of psoriasis only partially elucidated, underscoring the imperative to unravel these intricate mechanisms. In contradistinction to conventional techniques such as nuclear magnetic resonance (NMR) and liquid chromatography-mass spectrometry (LC-MS), the burgeoning laser desorption/ionization (LDI) metabolic paradigm holds substantial promise in elucidating the molecular mechanism of psoriasis. Nonetheless, achieving heightened sensitivity and high-throughput metabolite detection within intricate clinical biosamples mandates stringent requisites, encompassing favourable ionization efficiency and high surface area. Henceforth, we proffered a dual-strategy entailing the utilization of transition metal carbides (MXene) with unique morphology and the integration of multi-walled carbon nanotubes (MWCNTs) to ameliorate these challenges for psoriasis. We have corroborated the morphological architecture, elemental composition, and efficacy of LDI when applied to MWCNTs-doped MXene. Egregiously, through the employment of both animal models and clinical specimens, we attained diagnostic efficiencies of 0.959 and 0.924 via receiver operating characteristic (ROC) curve analysis, respectively, for discrimination psoriasis from control individuals. Doped MXene evinced exceptional signal amplification and imperviousness to salt and protein interference. Furthermore, enrichment pathway analysis unveiled a significant escalation in leukotriene E4 and arachidonic acid levels within the psoriasis cohort. Harnessing LDI metabolic fingerprints, concomitant with MWCNTs-doped MXene, expedited the recognition of the distinct metabolic characteristics inherent to psoriasis, thereby laying bare the dysregulation in leukotriene metabolism. This epochal breakthrough holds immense potential to usher in new vistas for exploring the underlying mechanisms governing the onset and progression of psoriasis-related disorders, thereby significantly contributing to the refinement of psoriasis health management strategies.

MWCNT Filled Banana-Rice Husk Epoxy Hybrid Natural Fiber Polymer Composites

Natural fiber composites are prepared by combining two varying fiber/filler contents with a single matrix material. Hybrid polymer composite material made with synthetic agents (Thermosetting polymer) and natural fiber/filler contents. The current study focuses on hybrid polymer composite Multi Walled Carbon nanotubes (MWCNT)-filled Banana fiber/Rice husk filler-reinforced composites that have been assessed for mechanical responses. The banana fiber mat has been in the constant piling mode and altering the MWCNT and rice husk percentage in volume. Vacuum lay-up technique was used to construct the hybrid polymer composite and MWCNT was included with the help of ultrasonic probe sonicator instrument. Mechanical testing is performed accordance to the ASTM standards. The integration of MWCNT, as well as the constant piling order of banana fiber layers, has a stronger impact on mechanical properties. The three samples are prepared at the extremities 5% Banana fiber mat uniform loading and rice husk proportions are 10%, and 15% along with MWCNT filler (0.5% and 1%) for BRME2 and BRME3. The exhibited mechanical testing of the hybrid polymer composite to identify the conventional enhancement of hardness, tensile, impact, flexural, and compressive properties. Scanning Electron Microscope (SEM) is used to examine the fractograph of the tensile sample prepared with BRME3. BRME2 polymer composite with 1% weight of MWCNT was identified higher mechanical properties compare to BRME3 and BRME1 (Tensile, Flexural Strength, and Shore-D Hardness: 46.5 MPa, 59.7 MPa, and 88.5). Furthermore, the impact strength of BRME3 was significantly higher than BRME2 and BRME1.

Integration of multiwalled carbon nanotubes with cobalt oxide for smart electrochemical sensing of epicatechin in foods

Integration of multiwalled carbon nanotubes with cobalt oxide for smart electrochemical sensing of epicatechin in foods

Solid-state reaction induced defects in multi-walled carbon nanotubes for improving microwave absorption properties

• Defect structures and contents of MWCNTs have been optimized. • MA property of MWCNTs could be optimized by the defect engineering. • Dipole polarization can effectively improve MA performance. • Permeability-to-permittivity transformation is another MA mechanism. Dielectric polarization performance induced by defect engineering approach has been proved to be an effective way for improving the microwave absorption property of carbon-based materials. Assisting by the solid-state reaction, the structural integrity of multi-walled carbon nanotubes (MWCNTs) would be broken along with the volume expansion and etching process of cobalt oxides. Therefore, the defects could be obtained and result in the enhancement of microwave absorption property. Ascribing to the broken wall structures, the defect-distances ( L D ) and concentrations ( n D ) have been optimized to be 9.80 nm and 3.37 × 10 11 cm −2 . The minimum reflection loss ( RL ) had reached -54.6 dB at 4.5 GHz with a thickness of 4.13 mm and the corresponding effective absorption bandwidth (EAB <-10 dB ) was analyzed to be 14.6 GHz. Such enhancement is correlated to the dielectric polarization and the permeability-to-permittivity transformation raised from the defect structures and concentrations. The present work demonstrates an effective strategy for tailoring the microwave absorption property of MWCNTs by engineering defect concentrations, and could be further extended to other carbon-based absorbents.

Chemical Wet Oxidation of Carbon Nanotubes for Electrochemical Determination of Methyl Parathion

Surface properties of carbon nanotubes in electrochemical sensors can be dramatically altered depending on chemical groups and structural defects present on the surface. The effect of oxidation on structural integrity of multiwalled carbon nanotubes through acidic (nitric/sulfuric acids) and basic (sodium hydroxide) agents has been studied. Chemical modifications of carbon nanotubes structures were evaluated by Raman, Fourier transform infrared spectroscopy and transmission electronic microscopy. Furthermore, these materials were used to construct sensors for electrochemical determination of pesticide methyl parathion (MP). Under optimized conditions, a calibration curve was obtained for MP determination employing a glassy carbon electrode modified with acidic treated and basic treated carbon nanotubes which showed a linear response ranging from 1.0 × 10–7 to 3.4 × 10–5 M with limits of detection of 3.3 × 10–8 and 3.5 ×10–8 M, respectively. Analytical performance of the electrodes showed similar voltammetric behavior providing good sensitivity for the determination of methyl parathion.

Structural evolution of multi-walled carbon nanotubes during the consolidation of Al matrix composites

Abstract The crystalline integrity of multi-walled carbon nanotubes (MWCNTs) plays a critical role in determining the performance of MWCNT/Al composites. In this work, the structural evolution of MWCNTs during composite consolidation was studied via high-resolution transmission electron microscopy and Raman spectroscopy. The MWCNTs were not structurally damaged during the spark plasma sintering of MWCNT/Al mixed powders. However, two kinds of fractures, i.e., clear break and sword-in-sheath failure, were generated under severe plastic deformation of Al during hot extrusion. We concluded that the MWCNT failure, seen on the fractured composites, was caused by the consolidation process rather than the tensile tests. This work provides a better understanding of the strengthening behavior of MWCNTs, and the design of high-performance MWCNT/Al composites using suitable consolidation techniques.

The influence of manganese(IV) oxide addition on the dispersion characteristics and structural integrity of MWCNTs in metal oxides

Recent advancement in material science and engineering has fostered the utilization of metal oxides (MOs) in diverse engineering applications. Despite the widespread application of MOs, they have certain limitations such as brittleness and low thermal conductivity. Therefore, the integration of multiwalled carbon nanotubes (MWCNTs) into their structure will augment the properties of MOs since they posses excellent mechanical, thermal and electrical properties. In order to achieve the effective transfer of the unique properties of MWCNTs into MOs, it is paramount to homogenously disperse the nanotubes within the MO matrix. Past works have emphasized that MWCNTs tend to agglomerate during their incorporation into metal matrices. In this study, the homogeneous dispersion of 1 wt% MWCNTs in metal oxides was accomplished by the introduction of manganese oxide (MnO2) of various (5, 10, 15) weight percentages in titanium oxide (TiO2). This was carried out by the adoption of regulated milling parameters: speed 100 rpm, time 6 h, and ball to powder ratio 10:1 using a high-energy ball mill. The dispersion characteristics and structural integrity of the MWCNTs in MOs were evaluated by the adoption of scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray diffraction (XRD) techniques. The results indicated that MWCNTs were homogeneously dispersed in the MOs; however, better dispersion with minimal structural strain to the MWCNTs was achieved at a higher weight percent of MnO2 in the composite powder mixture.

Bidirectional and Stretchable Piezoresistive Sensors Enabled by Multimaterial 3D Printing of Carbon Nanotube/Thermoplastic Polyurethane Nanocomposites.

Fabricating complex sensor platforms is still a challenge because conventional sensors are discrete, directional, and often not integrated within the system at the material level. Here, we report a facile method to fabricate bidirectional strain sensors through the integration of multiwalled carbon nanotubes (MWCNT) and multimaterial additive manufacturing. Thermoplastic polyurethane (TPU)/MWCNT filaments were first made using a two-step extrusion process. TPU as the platform and TPU/MWCNT as the conducting traces were then 3D printed in tandem using multimaterial fused filament fabrication to generate uniaxial and biaxial sensors with several conductive pattern designs. The sensors were subjected to a series of cyclic strain loads. The results revealed excellent piezoresistive responses with cyclic repeatability in both the axial and transverse directions and in response to strains as high as 50%. It was shown that the directional sensitivity could be tailored by the type of pattern design. A wearable glove, with built-in sensors, capable of measuring finger flexure was also successfully demonstrated where the sensors are an integral part of the system. These sensors have potential applications in wearable electronics, soft robotics, and prosthetics, where complex design, multi-directionality, embedding, and customizability are demanded.

Multifunctional Cement Composites Enhanced With Carbon Nanotube Thin Film Interfaces

Concrete and other cementitious composites used in civil infrastructure are prone to many forms of damage. For example, cracks could occur and propagate to cause catastrophic component or system-level failure. Therefore, the objective of this study was to nano-engineer a self-sensing cementitious composite that could detect and locate damage. Integration of multi-walled carbon nanotubes (MWNTs) in the mortar mix design and during casting enhanced the electromechanical or sensing properties of the cementitious composites. Instead of directly dispersing MWNTs in the cement matrix, the cement-particle interface was modified using spray-coated MWNT-latex thin films deposited directly onto dry sand particles prior to mortar casting. This procedure preserved MWNT dispersions within the thin film architecture, used minimal amounts of MWNTs, was scalable, and provided dramatic sensing performance enhancements. The mechanical and electromechanical properties of mortar specimens were characterized using compressive cyclic load tests. Furthermore, an electrical resistance tomography (ERT) algorithm was used for mapping mortar specimens' spatial resistance distributions. Since their resistance was precalibrated to strain, localized changes in calculated resistance indicated damage. Spatial damage detection was validated by drilling holes in various locations in cementitious composite plates and then by mapping resistance distributions using ERT.

Synthesis, Optimization, and Performance Demonstration of Electrospun Carbon Nanofiber-Carbon Nanotube Composite Sorbents for Point-of-Use Water Treatment.

We developed an electrospun carbon nanofiber-carbon nanotube (CNF-CNT) composite with optimal sorption capacity and material strength for point-of-use (POU) water treatment. Synthesis variables including integration of multiwalled carbon nanotubes (CNTs) and macroporosity (via sublimation of phthalic acid), relative humidity (20 and 40%), and stabilization temperature (250 and 280 °C) were used to control nanofiber diameter and surface area (from electron microscopy and BET isotherms, respectively), surface composition (from XPS), and strength (from AFM nanoindentation and tensile strength tests). Composites were then evaluated using kinetic, isotherm, and pH-edge sorption experiments with sulfamethoxazole (log Kow = 0.89) and atrazine (log Kow = 2.61), representative micropollutants chosen for their different polarities. Although CNFs alone were poor sorbents, integration of CNTs and macroporosity achieved uptake comparable to granular activated carbon. Through reactivity comparisons with CNT dispersions, we propose that increasing macroporosity exposes the embedded CNTs, thereby enabling their role as the primary sorbent in nanofiber composites. Because the highest capacity sorbents lacked sufficient strength, our optimal formulation (polyacrylonitrile 8 wt %, CNT 2 wt %, phthalic acid 2.4 wt %; 40% relative humidity; 280 °C stabilization) represents a compromise between strength and performance. This optimized sorbent was tested with a mixture of ten organic micropollutants at environmentally relevant concentrations in a gravity-fed, flow-through filtration system, where removal trends suggest that both hydrophobic and specific binding interactions contribute to micropollutant uptake. Collectively, this work highlights the promise of CNF-CNT filters (e.g., mechanical strength, ability to harness CNT sorption capacity), while also prioritizing areas for future research and development (e.g., improved removal of highly polar micropollutants, sensitivity to interfering cosolutes).

Solvent and Substituent Effects on the Aggregation Behavior of Surface-Active Ionic Liquids with Aromatic Counterions and the Dispersion of Carbon Nanotubes in their Hexagonal Liquid Crystalline Phase.

The aggregation behavior of surface-active ionic liquids (SAILs) 1-dodecyl-3-methylimidazolium m- and p-hydroxybenzoate (m-C12mimHB and p-C12mimHB) in water and ethylammonium nitrate (EAN) was investigated. Surface tension measurements indicate that the cmc values of SAILs in EAN are much higher than those in water, resulting from the weaker solvophobic effect of EAN, and the stronger stability of SAILs/EAN complexes proven by DFT calculations. Compared to 1-dodecyl-3-methylimidazolium salicylate (C12mimSal), the effect of substituent position leads to weaker interactions between aromatic counterions and headgroups. The hexagonal liquid crystal (H1) phase formed by C12mimHB in water or EAN at a higher concentration was determined by polarized optical microscopy (POM), small-angle X-ray scattering (SAXS), and rheology techniques. Structural parameters estimated from SAXS curves suggest that the higher SAILs concentration or temperature leads to a smaller lattice parameter (a0) and a denser arrangement of cylinders. For C12mimHB, the formation of the H1 phase in H2O is easier than that in EAN. Furthermore, compared to C12mimSal, C12mimHB exists over a broad region of the hexagonal liquid crystalline (H1) phase, which is due to the different position of the substituents on the aromatic ring of counterions. Therefore, the H1 phase of the lypotropic liquid crystals (LLCs) formed in the C12mimHB/H2O system exhibits excellent performance in uniformly dispersing multiwalled carbon nanotubes (MWCNTs). Increasing the concentration of MWCNTs results in a larger lattice parameter (a0) value, indicating the integration of MWCNTs within the cylinders of the H1 phase. The rheological measurement results demonstrate that MWCNTs/LLCs composites are highly viscoelastic, and the presence of MWCNTs obviously strengthens the apparent viscosity of the H1 phase.

Multi-Walled Carbon Nanotube Electrode Optimization for Thermocells

There is an abundance of rejected thermal energy in industrial settings available for conversion to electricity by devices such as thermocells. Compared to solid state thermoelectric technology, thermocells scavenge low-grade heat more efficiently and offer 10-fold greater Seebeck coefficients (ferro/ferricyanide α = -1.4 mV/K). Since aqueous ferrocyanide cells are thermodynamically constrained by the Seebeck coefficient, focus has shifted to optimizing their kinetic performance. Nanocarbons, particularly multi-walled carbon nanotubes (MWNTs) are emerging as the favored active electrode material in thermocells (1-3). These offer high conductivity and large electrochemically active surface areas. The preparation of MWNT-based electrodes, however, is no trivial task and non-electrochemically active binder materials (e.g. PVDF) are nearly always required. A variety of methods for MWNT/PVDF electrode casting have been investigated but doctor blade and spray-coat methods are currently lowest cost and most commonly employed. In this study, we contribute to the on-going optimization of spray-coated MWNT/PVDF on Al electrodes by exploring the influence of mass loading and active material-binder content via characterization in functioning full thermocells. While varying the MWNT/PVDF ratio had little impact on peak power densities, we found that the thinnest possible coatings (i.e. one coat) yielded the highest power density per mass of MWNTs at 290 W kg-1. This suggests that tortuosity and/or poor wettability (hydrophobicity) of the MWNT electrodes limit the penetration depth of aqueous ferro/ferricyanide ions during thermoelectric conversion. Therefore, if coating thickness is strictly controlled, only 0.08 mg cm-2 (in our case) is needed. This minimizes inactive bulk MWNTs and brings the previously prohibitively expensive MWNTs to a fraction of the cost of the ferro/ferricyanide electrolyte for thermal to electric energy harvesting. The findings may be of broader interest for the fabrication of any electrochemical cells where integration of MWNTs is desired. Figure 1. Potential-current and power curves of thermocells for three thicknesses of spray-coated MWNT/PVDF electrodes on Al. Current and power are normalized by MWNT mass, where the thicknesses refer to loadings of 1.0, 0.23, and 0.08 mg cm-2 MWNTs at 50/50 MWNT/PVDF content by mass.

Carbon nanotubes modified with ZnO nanoparticles: High-efficiency electromagnetic wave absorption at high-temperatures

Carbon nanotube–ZnO composite powders, which act as high-temperature electromagnetic wave absorbents, are prepared by homogeneous precipitation. Carbon nanotube–ZnO/glass composites are fabricated by pressureless sintering. ZnO nanoparticles are assembled on the surface of carbon nanotubes, which produces heterostructure and enhances polarization at heterogeneous interface. Owing to the consumption of an amorphous carbon layer on the outer surface of carbon nanotubes and the generation of oxygen vacancies in ZnO during sintering, a higher concentration of charge carriers is produced in ZnO, which causes more relaxation polarization and dielectric loss in electromagnetic field. Owing to the shortened relaxation time, and the increase of relaxation polarization, permittivity and dielectric loss increases with the increase in testing temperature. Reflection coefficient of the obtained composite reaches −70dB. The special integration of multiwalled carbon nanotubes modified with some metal oxide semiconductor nanoparticles provides an effective approach to design high-temperature electromagnetic absorbing materials.

Carbon-Based Nanomaterial for Nanoelectronics

Carbon-based nanomaterials such as carbon nanotubes (CNT) and graphene have been known for their outstanding transport, thermal and mechanical properties, and their great potentials in nanoelectronic device applications such as CNT field effect transistors (CNFET), interconnects, nano-electromechanical systems (NEMS). Using an energy-delay optimization approach, we showed that the current available best CNT FETs is about 2-3 times more energy efficient than 32nm state-of-art silicon MOSFETs, evaluated at the same delay. At the 11nm technology node, CNFET is projected to outperform the ITRS target for logic devices by 2-3 times. In spite of the great performance potentials, challenges still exist on the way towards commercial carbon-based device technology. In this paper, we review some of the recent advances such as wafer-scale fabrication of CNFET-based logic circuit, circuit-level solution for removal of metallic CNTs, and integration of multi-walled CNTs and graphene interconnects with CMOS circuit.

Interface interactions in benzophenone doped by multiwalled carbon nanotubes

The interface interactions were studied by methods of conductometry, low-temperature phosphorescence and differential scanning calorimetry (DSC) in multiwalled carbon nanotubes (MWCNT) and benzophenone (BP) composite. The concentration of MWCNTs was varied within 0–1 wt%. A percolative threshold was found at MWCNT concentrations exceeding 0.1 wt%. The integration of MWCNTs caused melting temperature increase (≈3 K for 1 wt% of MWCNTs). The effect of positive thermal resistively coefficient, as well as substantial hysteretic behaviour of electrical conductivity σ in a heating–cooling cycle, was observed near the melting point of BP ( T m =321.5 K). The activation-type temperature behaviour of electrical conductivity was observed in the temperature range of supercooled BP. The activation energy was decreasing with increase of MWCNT concentration. The observed nonlinear dependencies of electrical conductivity σ vs. applied voltage U reflect the transport mechanism of the charge carriers through amorphous interface films formed near the surface of the MWCNTs. The thermal shifts of phosphorescence spectra measured within the temperature range 5–200 K evidence existence of such interface films of amorphous BP with width of the order of 0.1 μm.

Magnetic removal of dyes from aqueous solution using multi-walled carbon nanotubes filled with Fe 2O 3 particles

The Fe 2O 3 nanoparticles have been introduced into the multi-walled carbon nanotubes (MWCNTs) via wet chemical method. The resulting products are characterized by TEM, EDX, XRD and VSM. The magnetic MWCNTs have been employed as adsorbent for the magnetic separation of dye contaminants from water. The adsorption test of dyes (Methylene Blue and Neutral Red) demonstrates that it only takes 60 min to attain equilibrium and the adsorption capacities for Methylene Blue and Neutral Red in the concentration range studied are 42.3 and 77.5 mg/g, respectively. The magnetic MWCNTs can be easily manipulated in magnetic field for desired separation, leading to the removal of dyes from polluted water. The integration of MWCNTs with Fe 2O 3 nanoparticles has great potential application to remove organic dyes from polluted water.

Chemical oxidation of multiwalled carbon nanotubes

The effect of oxidation on the structural integrity of multiwalled carbon nanotubes through acidic (nitric acid and a mixture of sulfuric acid and hydrogen peroxide) and basic (ammonium hydroxide/hydrogen peroxide) agents has been studied. In order to purify the as-received material, a non-oxidative treatment (with hydrochloric acid) was also applied. Electron microscopy and thermogravimetric analysis clearly revealed that the nitric acid-treated material under reflux conditions suffered the highest degree of degradation, such as, nanotube shortening and additional defect generation in the graphitic network. Basic oxidative treatment led to the complete removal of amorphous carbon and metal oxide impurities but the structural integrity was found to be intact. X-ray photoelectron spectroscopy was employed to confirm the different functionalities produced for each oxidation agent, whereas titration measurements determined the relative concentration of carboxylic functions onto the graphitic surface. Moreover, a general relationship between the chemical treatment and the amount of non-graphitic carbon was established by means of Raman spectroscopy measurements. The possibility of controlling the required amount of functionality, carboxylic and hydroxyl, via these oxidation procedures is discussed.