Surface Of Multi-walled Carbon Nanotubes Research Articles

High-performance flexible tactile sensor enabled by multi-contact mechanism for normal and shear force measurement

Flexible tactile sensors are essential components of pressure monitoring in the fields of electronic skin, health care, and robotic hands. Currently, there is a great demand for tactile sensors that exhibit high sensitivity, linearity, and a wide dynamic range, as they play an increasingly vital role in information exchange. However, it is still challenging to achieve a synchronous improvement in performance through a simple strategy. Theoretically, we present the multi-contact mechanism for sensing enhancement by changing the contact mode and the initial state. Specifically, the curved polydimethylsiloxane (PDMS)/multi-walled carbon nanotubes (MWCNTs) surface ensures the continuity of contact deformation, leading to a wide dynamic range. Besides, the discrete resistor pillars on the micro-honeycomb electrodes (MHEs) depress the initial current, and thus enhance the sensitivity. Experimentally, we utilize microelectromechanical systems (MEMS) technology to fabricate the MHEs, mainly including patterning and micro-electroforming processes. By adjusting the resistor distribution density and the curvature of PDMS contact, the extraordinary sensitivity is tuned from 25.88 kPa−1 to 64.68 kPa−1, and the maximum detection pressure switches between 500 kPa and 1400 kPa, which is consistent with the physical model. Furthermore, a proof-of-concept of the flexible three-axis tactile sensor demonstrates the possibility of realizing normal and force measurement. These results reveal the great application prospect of tactile sensors based on multi-contact mechanism in future wearable electronics.

Photocatalytic Decolorization of Crystal Violate Dye Solution by ZnO/MWCNT Nanocomposite

By extracting crystal violate dye (CV) from its aqueous solution, the photocatalytic decolorization performance of ZnO/MWCNT nanocomposite was evaluated. The nanocomposite was prepared by precipitation of ZnO and incorporates on the surface of Multi-Walled Carbon Nanotubes (MWCNT). ZnO nanoparticles were synthesized using the sol gel process with MWCNT acting as a template. They were then analyzed by XRD, SEM, and TEM, which revealed how the shape of the spherical nano ZnO interacts with the point of zero charge (pzc), which allows us to see the physical attributes. In the dipping photoreactor, which included a slurry of dye solution and ZnO/MWCNT nanocomposite, the effectiveness of decolorization was assessed. The photodecolorization was studied for CV dye in aqueous solution at different conditions: The effect of time, weight of catalyst, concentration of dye, temperature, the initial pH of dye solution and addition of S2O82- to show the optimum condition of this process. The main results were the synthesis of incorporated ZnO on MWCNT surface with 10-20 nm with high photodecolorization against CV dye. Full decolorization reached at 90 min and 89.8% decolorization at the half time of reaction. ZnO/MWCNT weight of 0.06 gm per 100 mL was optimum for photodecolorization. The photocatalytic reaction was more efficient in the deceasing of CV concentration and obeys the Langmuir-Hinshelwood kinetic, while the photodecolorization was not less than 95% in pH range 6-10.Also, the photocatalytic reaction was effected in the presence of S2O82-, where the photodecolorization was more efficient.

On twin substantially improved thermal properties and stability of pyrrolidinium-based ionanofluids with long multi-walled carbon nanotubes

The quest for advanced heat transfer fluids with superior thermal properties has led to the exploration of ionanofluids (INFs). Such systems are composed of ionic liquids (ILs) and thermoactive dispersed nanoparticles, and offer promising opportunities for the enhanced heat transfer. In this work, we selected long multi-walled carbon nanotubes (MWCNTs) as well as 1-propyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C3C1pyr][NTf2]) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C4C1pyr][NTf2]) as base liquids. The chosen ILs have the same thermal conductivity and similar viscosity which results in the ‘twin’ thermal conductivity of related INFs in the whole range of MWCNTs loading as well as similar rheological performance. We find the remarkable synergistic effects of incorporating 5.0 wt% of long MWCNTs into [C3C1pyr][NTf2]-based INF, resulting in a sky-rocketing 560% increase in thermal conductivity of INF compared to the base IL. The [C4C1pyr][NTf2]-based INFs exhibited excellent thermal and sedimental long-term stability (4 years), characterized by change in thermal conductivity and in density lower than declared uncertainties. We proved that remarkably enhanced thermal conductivity was mainly influenced by the high aspect ratio of MWCNTs enabling formation of long-range, 3D nanotube networks additionally stabilized by nanolayers of IL on the MWCNTs surface.

Determination of aristolochic acid using a piezoelectric immunosensor based on magnetic carbon nanocomposites

A technique for the determination of aristolochic acid (AA) in food products using a piezoelectric immunosensor is presented. Magnetic carbon nanocomposites (MCNC) were used as the recognition layer of the sensor, on the surface of which protein conjugates of AA were immobilized. Abstract-Methods for the synthesis of Fe3O4 magnetic nuclei and their attachment to the surface of multi-walled carbon nanotubes (CNTs) have been studied. Using IR spectrometry, it was found that the formation of the recognition layer of the sensor occurs due to the formation of covalent bonds between the amino groups of AA conjugates and carboxyl groups of CNTs. The concentrations of protein conjugates based on ovalbumin (OVA) and bovine serum albumin (BSA) (0.3 and 0.2 mg/ml) and the degree of antibody dilution (0.25) were determined, which provide optimal characteristics of the piezoelectric immunosensor. The metrological characteristics of the method for determining AA have been established. The range of determined concentrations of AA and the limit of detection when using a piezoelectric immunosensor with a recognition layer based on MUNA/AA-OVA and MUNA/AA-BSA are (ng/ml): 50 – 400 and 10; 100 – 300 and 50, respectively. The sensor has been tested in the determination of AA in samples of Chinese herbal tea and dietary supplements for weight loss. No acid was found in tea, and in dietary supplements, the acid content is 3.2 μg/g.

Treatment of Multi-Walled Carbon Nanotubes with Dichromic Acid: Oxidation and Appearance of Intercalation.

This work is dedicated to the study of the treatment of multi-walled carbon nanotubes (MWCNTs) with dichromic acid. The dichromic acid was formed by dissolving different concentrations of CrO3 in water. The effect of the concentration of dichromic acid on the change in texture characteristics, elemental composition, defectiveness, graphitization degree, and surface chemistry of MWCNTs was investigated using various analytical techniques, such as transmission electron microscopy, energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). Testing of MWCNTs as electrodes for supercapacitors in 3.5 M H2SO4 solution was carried out using cyclic voltammetry. A decrease in the average diameter of CNTs after treatment was found. The EDX and XPS showed that the oxygen content on the surface of MWCNTs increased after treatment with dichromic acid. The formation of Cr2O3 after treatment with dichromic acid was detected by XPS. High angle annular dark field scanning transmission electron microscopy was used to confirm the intercalation of the chromium-containing compound between graphene layers of MWCNTs after treatment with dichromic acid. It was found that two different types of MWCNTs showed diverse behavior after treatment. The highest specific capacitance of the MWCNTs after treatment was 141 F g-1 (at 2 mV s-1) compared to 0.3 F g-1 for the untreated sample.

High‐performance main‐chain polybenzoxazine composites by incorporating multi‐walled carbon nanotubes with different surfacial structure: Mechanical properties, thermal stability and mechanisms

AbstractHerein, multi‐walled carbon nanotubes (MWCNTs) with different surfacial structure were first designed and synthesized, and then incorporated into main‐chain polybenzoxazine (PBZ) to fabricate PBZ composites. Fourier transform infrared results showed that the ring‐opening crosslinking process of benzoxazine (BZ) oligomer was catalyzed due to the existence of COOH and NH2 groups on the surface of MWCNTs. The enhanced interface interactions between MWCNTs‐fBZ and PBZ contributed to the improvement of the mechanical properties. When the MWCNTs‐fBZ content was 1.5%, the MWCNTs‐fBZ/PBZ composites had excellent tensile strength of 102.64 MPa. The highest impact strength, which was 15.96 kJ/m2 and 64.15% higher than that of neat PBZ at 1.5% MWCNTs‐fBZ was achieved. Through the Halpin‐Tsai equation, combined with the experimental results, the correction factor was obtained to predict the mechanical properties. FESEM observations showed that the dispersion of MWCNTs in the PBZ matrix depended on the functional groups of MWCNTs. TGA tests and Horowitz‐Metzger calculation found that the thermal decomposition temperature of the composites reached 451.7°C and had the highest decomposition activation energy of 153.20 kJ/mol at 2% MWCNTs‐fBZ. In summary, the obtained MWCNTs‐fBZ/PBZ composite showed excellent comprehensive performance and can potentially be used as advanced engineering material in demanding environments.

Facile synthesis of Co3O4@SeNPs grafted MWCNTs Nanocomposite for high energy density supercapacitor and antimicrobial applications

Herein for the first time, intertwined nanocomposite (Co3O4@Se NPs/MWCNTs) of cobalt oxide nanoparticles (Co3O4 NPs) adsorbed on selenium nanoparticles (Se NPs) (designated as Co3O4@Se NPs) and thiol (–SH) functionalized multiwalled carbon nanotubes (MWCNTs) was synthesized by a simple hydrothermal method to achieve excellent capacitive and microbicidal performance. The surface morphology, microstructure and functional group studies ensures that the existence of Co3O4@Se NPs onto MWCNTs. The electrochemical studies (cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD)) were performed and demonstrated the Supercapacitive performance of Co3O4@Se NPs/MWCNTs nanocomposite. Higher electrochemical capacitance (356 F/g) with better coulombic efficiency of 84% was acquired. Also, it exhibited an admirable antimicrobial study and illustrated that the pathogens were more susceptible to Co3O4@Se NPs/MWCNTs nanocomposite. The superior electrochemical and antimicrobial activity was achieved owing to the specific inherent properties of thiol (–SH) groups opt binding and stabilizing Co3O4@Se NPs against its aggregation on the surface of MWCNTs. The thiol (–SH) group influences the enrichment of Co3O4@Se NPs onto MWCNTs and facilitates in enhancement of energy storage and microbicidal performance the nanocomposite. These attained outcomes put forward the applicability of the synthesized active nanocomposite towards supercapacitor and antibacterial agents against pathogens.

Metal-Free Electrocatalysts for the Selective 2 e- Oxygen Reduction Reaction: A Never-Ending Story?

Hydrogen peroxide (H2 O2 ) electrosynthesis via the 2e- Oxygen Reduction Reaction (ORR) represents a highly challenging, environmentally friendly and cost-effective alternative to the current anthraquinone-based technology. Various lightweight element hetero-doped carbon nanostructures are promising and cheap metal-free electrocatalysts for H2 O2 synthesis, particularly those containing O-functionalities. The exact role of O-containing functional groups as electroactive sites for the process remains debated if not highly controversial. Herein, we have reported on the covalent exohedral functionalization of the outer surface of extra-pure multi-walled carbon nanotubes (MWCNTs) with discrete O-functional groups as a unique approach to prepare selective electrocatalysts for the process. This kind of decoration has added fundamental tiles to the puzzling structure/reactivity relationship of O-containing carbon-based catalysts for ORR, clearing doubts on the controversial role of hydroxyl/phenol groups as key functionalities for the design of more performing 2e- ORR electrocatalysts.

The Influence of Ag+/Ti4+ Ratio on Structural, Optical and Photocatalytic Properties of MWCNT–TiO2–Ag Nanocomposites

In this paper, we propose a simple procedure to obtain multi-walled carbon nanotubes (MWCNTs) decorated with TiO2–Ag nanoparticles (MWCNT–TiO2–Ag). The MWCNTs were decorated with TiO2–Ag via combined functionalization with –OH and –COOH groups and a polymer-wrapping technique using poly(allylamine)hydrochloride (PAH). TiO2-modified Ag nanoparticles were synthesized via the Pechini method using a mixture of acetylacetonate-modified titanium (IV) isopropoxide with silver nitrate (with Ag+/Ti4+ atomic ratios of 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%) and L(+)-ascorbic acid as reducing agents. XRD analysis revealed the formation of nanocomposites containing CNT, anatase TiO2, and Ag. The presence of nanoparticles on the MWCNT surfaces was determined using TEM. The morphology of the TiO2–Ag nanoparticles on the MWCNT surfaces was also determined using TEM. UV–Vis investigations revealed that an increase in the ratio between Ag+ and Ti4+ decreased the band gap energy of the samples. The characteristic vibrations of the TiO2, Ag, and C atoms of the graphite were identified using Raman spectroscopy. The photocatalytic activity of the MWCNT–TiO2–Ag nanocomposite was assessed by examining the degradation of Allura Red (E129) aqueous solution under UV irradiation. The dye photodegradation process followed a pseudo-first-order kinetic with respect to the Langmuir–Hinshelwood reaction mechanism. The spin-trapping technique evidenced that •O2− was the main species generated responsible for the Allura Red degradation.

Synthesis and characterization of Schiff base ligand-mutliwalled carbon nanotubes as mercury-free electrochemical sensor for detecting toxic metals in aquatic treatment

The aspire of the present investigation is to develop a novel mercury-free electrochemical sensor for the sensitive detection of toxic pollutant in environmental sources. The synthesis of N,N′-bis(salicylaldehyde)-1,2-diaminobenzene (BSD) as a pre designed Schiff-base ligand (SBL) coated on surface of multi-walled carbon nanotubes (MWCNTs) modified working electrode for the detection of Pb2+ and Hg2+ in various water sources. The role of BSD contains hydroxyl and imine ions acting as active sites to detect the metal ions in 0.1 M of acetate buffer solution. A star like crystal structure for BSD/MWCNTs modified surface of electrode was observed using SEM analysis. The conductance (σ) for PIG electrode (unmodified), MWCNTs modified and BSD/MWCNTs modified electrodes are 4.7 × 10−5 S cm−1, 408.1 × 10−5 S cm−1 and 553.2 × 10−5 S cm−1 were estimated. BSD/MWCNTs modified electrode shows the best conductivity compared with other electrodes. For the selective detection of Pb2+ and Hg2+, the square wave anodic stripping voltammetry (SWASV) was utilised. The linear range of Pb2+ and Hg2+ in the concentration from 2.0 to 155 nM and limits of detection for Pb2+ and Hg2+ were observed at 0.3 nM and 0.6 nM by SWASV. This sensor is often used for sensitive detection of analytes like Pb2+ and Hg2+ in different water samples. The results of SWASV recovered value are comparing with atomic absorption spectroscopy (AAS).

Preclinical evaluation of PEG-Multiwalled carbon nanotubes: Radiolabeling, biodistribution and toxicity in mice

Multiwalled carbon nanotubes (MWCNTs) have been integrated into many recent biomedical studies since their cylindrical architecture, high aspect ratio, and specific functionalization could allow carbon nanotubes (CNTs) to penetrate into the cells through the plasma membrane. However, one of the main challenges in the in vivo applications of these nanoparticles is their reduced biocompatibility and poor dispersibility. Furthermore, even today, there are still some knowledge gaps concerning CNTs toxicity and their behavior considering in vivo tumor-bearing mice models. In this sense, herein, polyethylene glycol chains were covalently bound to MWCNTs (PEG-MWCNTs) through an aliphatic nucleophilic substitution chemical reaction and radiolabeled with [99 mTc]Tc, yielding a high radiochemical rate. The physicochemical characterization procedures showed that the PEG chains were successfully covalently attached to the MWCNT surface. Biodistribution studies were carried out in tumor-bearing mice, and the results revealed that a produced system displays prolonged blood circulation time and relevant tumor uptake rates. Toxicological data were obtained from testing on healthy animals, and the data obtained revealed that PEG-MWCNTs did not induce an important toxicity profile. Considering all the results obtained in this work, the PEG-coated MWCNTs can be considered a potential candidate for future oncologic applications.

Synthesis, characterization, and electrochemical evaluation of SnFe2O4@MWCNTS nanocomposite as a potential hydrogen storage material

The widespread use of hydrogen as a vehicle fuel has prompted us to develop a new nanocomposite by immobilizing of tin ferrite nanoparticles (SnFe2O4) on the surface of multi-walled carbon nanotubes (abbreviated as MWCNTS) for the first time. The prepared nanocomposite powder (SnFe2O4@MWCNTS) was investigated utilizing various microscopy and spectroscopy methods, such as FT-IR, XRD, SEM, EDX, and BET techniques. Moreover, the electrochemical property of SnFe2O4@MWCNTS nanocomposite was investigated by cyclic voltammogram (CV) and charge–discharge chronopotentiometry (CHP) techniques. A variety of factors on the hydrogen storage capacity, such as current density, surface area of the copper foam, and the influence of repeated hydrogen adsorption-desorption cycles were assessed. The electrochemical results indicated that the SnFe2O4@MWCNTS has high capability and excellent reversibility compared to SnFe2O4 nanoparticles (NPs) for hydrogen storage. The highest hydrogen discharge capability of SnFe2O4@MWCNTs was achieved ∼ 365 mAh/g during the 1st cycle, and the storage capacity enhanced to ∼ 2350 mAh/g at the end of 20 cycles using a current of 2 mA. Consequently, the SnFe2O4@MWCNTS illustrated great capacity as a prospective active material for hydrogen storage systems.

Coaxial structured Bi2S3–SnS2-MWCNT hybrid nanocomposite with its improved thermoelectric properties

Bismuth(III) sulfide (Bi2S3), tin(IV) sulfide (SnS2), and a multi-walled carbon nanotube (MWCNT) are prepared as a hybrid composites (Bi2S3–SnS2-MWCNT) using a simple hydrothermal method. The as-prepared hybrid composite exhibit n-type thermoelectric (TE) characteristics and an enhanced power factor (PF) value. Bi2S3–SnS2 composites are anchored to the surface of MWCNT and form a coaxial structure. The nanostructure formation through bonding between these different materials is confirmed via scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS). The TE properties of the Bi2S3–SnS2-MWCNT composite is improved by changing the Bi2S3, SnS2 and MWCNT content. The maximum PF (∼150.8 μ·W/m·K2) was obtained for Bi2S3–SnS2-MWCNT composite with Bi:Sn ratio of 7:3 and 2 wt% of CNT. The highest PF values were ∼34 and ∼58 times higher than the PF of Bi2S3 and SnS2 at room temperature. The synthesized Bi2S3–SnS2-MWCNT hybrid nanocomposite can provide important components for fabrication CNT-based TE composites with high conversion efficiency, further advancing TE device.

Composite of DNA-Stabilized Multiwalled Carbon Nanotube and Nematic Liquid Crystal for Display Performance Optimization

We have prepared composites of a nematic liquid crystal (NLC) mixture to improve display performance by doping multiwalled carbon nanotubes (MWCNTs) and single-stranded-DNA-wrapped MWCNTs. Polarized optical microscopy images indicated the uniformity of the composite. Infrared absorption spectra showed there existed an interaction between MWCNTs and 4-pentyl-4′-cyanobiphenyl (5CB, a practical solvent-type monomer NLC) due to π–π stacking and charge transfer, indicating the anchoring of 5CB molecules on the MWCNT surface. The electro-optical property proved the incorporation of MWCNTs and DNA-wrapped MWCNTs reduced the threshold voltage and response time, thus following the changed splay elastic constant and rotational viscosity coefficient of LC, reflecting that DNA can improve the stability of MWCNTs in 5CB. Moreover, dielectric measurement showed the enhanced value to dielectric anisotropy and shift in relaxation frequency, including the changes of dielectric permittivity and loss, revealing the electrically “inertness” MWCNTs at high frequencies and the DNA-induced broadened frequency range of low dielectric loss. Then electrical conductivity tests further proved the cooperative orientation of MWCNTs with 5CB under the applied voltage and the contribution of MWCNTs’ high conducting along the long axis. This study revealed that MWCNT doping could improve the physical properties of NLCs, and DNA wrapping could pave a promising way toward stabilized MWCNT/NLC composites for display performance optimization.

Vapor-phase derived ultra-fine Bismuth nanoparticles embedded in carbon nanotube networks as anodes for sodium and potassium ion batteries

Bismuth (Bi) is a promising material as the anode for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) due to its characteristics such as reasonable price and high theoretical volumetric capacity (3800 mAh cm−3). Nevertheless, considerable drawbacks have hindered the practical applications of Bi, including its relatively low electrical conductivity and inevitable volumetric change during the alloying/dealloying processes. To solve these problems, we proposed a novel design:Bi nanoparticles were synthesized via a single-step low-pressure vapor-phase reaction and embedded onto the surfaces of multi-walled carbon nanotubes (MWCNTs). After being vaporized at 650℃ and 10-5 Pa, Bi nanoparticles less than 10 nm were uniformly distributed in the three-dimensional (3D) MWCNT networks to form a Bi/MWNTs composite. In this unique design, the nanostructured Bi can reduce the risk of structural rupture during cycling, and the structure of the MWCMT network is beneficial in shortening the electron/ion transport path. In addition, MWCNTs can improve the overall conductivity of the Bi/MWCNTs composite and prevent particle aggregation, thus improving the cycling stability and rate performance. As an anode material for SIB, the Bi/MWCNTs composite has demonstrated excellent fast charging performance with a reversible capacity of 254 mAh/g at 20 A/g. A capacity of 221mAhg−1 after cycling at 10 A/g for 8000 cycles has also been achieved for SIB. As an anode material for PIB, the Bi/MWCNTs composite has delivered excellent rate performances with a reversible capacity of 251 mAh/g at 20 A/g. A specific capacity of 270mAhg−1 after cycling at 1Ag−1 for 5000 cycles has also been achieved for PIB.

Resorc[4]arene Modifiers for Supramolecular Site-Directed Immobilization of Antibodies on Multi-Walled Carbon Nanotubes.

One of the main problems in developing immunosensors featuring carbon nanotubes (CNTs) is immobilizing antibodies (Abs) onto the CNT surface to afford selective binding to target antigens (Ags). In this work, we developed a practical supramolecular Ab conjugation strategy based on resorc[4]arene modifiers. To improve the Ab orientation on the CNTs surface and optimizing the Ab/Ag interaction, we exploited the host-guest approach by synthesizing two newly resorc[4]arene linkers R1 and R2 via well-established procedures. The upper rim was decorated with eight methoxyl groups to promote selective recognition of the fragment crystallizable (Fc ) region of the Ab. Moreover, the lower rim was functionalized with 3-bromopropyloxy or 3-azidopropiloxy substituents to bind the macrocycles on the multi-walled carbon nanotubes (MWCNTs) surface. Accordingly, several chemical modifications of MWCNTs were evaluated. After the morphological and electrochemical characterization of nanomaterials, the resorc[4]arene-modified MWCNTs were deposited onto a glassy carbon electrode surface to evaluate their potential applicability for label-free immunosensor development. The most promising system showed an improved electrode active area (AEL ) of almost 20 % and a site-oriented immobilization of the SARS-CoV-2 spike protein S1 antibody (Ab-SPS1). The developed immunosensor revealed a good sensitivity (23.64 μA mL ng-1 cm-2 ) towards the SPS1 antigen and a limit of detection (LOD) of 1.01 ng mL-1 .

Smart wearable triboelectric nanogenerator for self-powered bioelectronics and therapeutics

With the development of Triboelectric Nanogenerators (TENGs), the field of energy harvesting has experienced a new era of revolution following the trend to configure innovative materials, design, integrated sensing and high triboelectric output. Here, we investigated the electricity-generation process of TENG by conducting its finite-element analysis using COMSOL Multiphysics software. Further, the effect of different weight concentrations (0%, 2%, 4%, 6%) of multi-walled carbon nanotubes (MWCNT) into the Polydimethylsiloxane (PDMS) matrix was investigated. It has enabled us to find the optimal weight ratio of MWCNT and increase surface charge density, thereby enhancing triboelectric performance for realising smart wearable triboelectric nanogenerators (SW-TENG). On the other hand, a novel dynamic test platform was developed for automated tapping on TENG for quantified performance analysis of SW-TENG. The results indicate that 4 wt% is the optimal weight ratio for fabrication of MWCNT-PDMS based TENG as it recorded the highest open circuit voltage of 195.4 V revealing ∼79% enhancement in triboelectric output as compared to pure PDMS based TENG. Furthermore, SW-TENG was integrated with a bridge rectifier and 10 μF capacitor in order to power bioelectric devices such as a digital thermometer and a pulse sensor. Besides serving as a power source, the SW-TENG shows innovative sensing capabilities for delivering self-powered rehabilitation therapy augmenting the next generation healthcare systems.

CO Oxidation Reaction by Platinum Clusters on the Surface of Multiwalled Carbon Nanotubes: Experimental and Theoretical Study of Kinetics in a Wide Range of O2/CO Ratios

This work presents a systematic study of the kinetic aspects of CO oxidation reaction catalyzed by platinum nanoparticles (NPs) supported on the surface of multiwalled carbon nanotubes (MWCNTs). The investigation presented is closely related to the actual practical task of air purification in enclosed spaces. Therefore, the catalytic reaction was carried out in the presence of an excess of oxygen (5 vol.%) and over a wide range of CO concentrations from 50 ppm to 1600 ppm. For the catalyst characterization, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were applied. Kinetic modelling based on the Langmuir–Hinshelwood and Mars-van Krevelen mechanisms was taken as a basis, using the results obtained on Pt foil. Simulation of CO oxidation reaction on platinum NPs at temperatures above 90 °C was carried out using a kinetic model describing the reaction mechanism on bulk platinum. The description of the kinetics of CO oxidation reaction on Pt NPs over the entire temperature range, including the low temperatures down to −40 °C, required the introduction of the steps characterizing an additional concerted mechanism related to CO-assisted O2 dissociation. Using the presented model, some predictions of the kinetic behaviour of the system were made.

Block Copolymer Adsorption on the Surface of Multi-Walled Carbon Nanotubes for Dispersion in N,N Dimethyl Formamide

This research aims to characterize the adsorption morphology of block copolymer dispersants of the styrene-block-4-vinylpyridine family (S4VP) on the surface of multi-walled carbon nanotubes (MWCNT) in a polar organic solvent, N,N-dimethyl formamide (DMF). Good, unagglomerated dispersion is important in several applications such as fabricating CNT nanocomposites in a polymer film for electronic or optical devices. Small-angle neutron scattering (SANS) measurements, using the contrast variation (CV) method, are used to evaluate the density and extension of the polymer chains adsorbed on the nanotube surface, which can yield insight into the means of successful dispersion. The results show that the block copolymers adsorb onto the MWCNT surface as a continuous coverage of low polymer concentration. Poly(styrene) (PS) blocks adsorb more tightly, forming a 20 Å layer containing about 6 wt.% PS, whereas poly(4-vinylpyridine) (P4VP) blocks emanate into the solvent, forming a thicker shell (totaling 110 Å in radius) but of very dilute (<1 wt.%) polymer concentration. This indicates strong chain extension. Increasing the PS molecular weight increases the thickness of the adsorbed layer but decreases the overall polymer concentration within it. These results are relevant for the ability of dispersed CNTs to form a strong interface with matrix polymers in composites, due to the extension of the 4VP chains allowing for entanglement with matrix chains. The sparse polymer coverage of the CNT surface may provide sufficient space to form CNT-CNT contacts in processed films and composites, which are important for electrical or thermal conductivity.

Characterization of adhesion strength between carbon nanotubes and cementitious materials

Multi-walled carbon nanotube (MWCNT) and carbon nanofiber (CNF) additions increase the elastic modulus, flexural strength, and toughness of Portland cement concrete. However, the interaction mechanism between cement constituents and these nanomaterials is not fully understood. A modified MWCNT-coated atomic force microscopy (AFM) probe is developed by coating a silica particle with oxidized MWCNT through layer-by-layer assembly and adhering it to a tipless AFM cantilever. The probe allows measurement of adhesion between MWCNT and the substrate with a force control procedure. SEM-EDS is acquired in the same region as AFM measurements through a benchmarking scheme to correlate chemistry with the measured adhesion. Statistical deconvolution shows C–S–H regions have lower adhesion to MWCNT than intermixed regions (C–S–H/Clinker). Furthermore, in C–S–H regions, the normalized adhesion strength increases with calcium concentration. This result is due to the higher interaction between the oxygen functional groups in the MWCNT surface and the calcium in the substrate.