Surface Of Multi-walled Carbon Nanotubes Research Articles

Влияние термической обработки на структуру и электрохимические характеристики композита на основе многостенных углеродных нанотрубок и оксида марганца

In this paper, the effect of heat treatment in an inert medium on the structure and electrochemical characteristics of a composite based on multi-walled carbon nanotubes (MWCNTs) and manganese oxide formed by deposition from a KMnO4 solution is investigated. As a result of heat treatment composite (500°C) in argon on the surface of multi-walled carbon nanotubes are formed nanoparticles of non-stoichiometric manganese oxide. X-ray photoelectron spectroscopy data indicate a high degree of functionalization of the surface of carbon nanotubes by oxygen-containing groups, as well as the possible formation chemical bonds at the interfaces of the composite. Electrochemical measurements showed that the specific capacity of the composite after heat treatment (88-50 F/g) exceeds the capacity of the original MWCNTs (18-15 F/g) in the current range discharge 0.1-1A/g.

A multi-walled carbon nanotube-supported acidic ionic liquid catalyst for the conversion of biomass-derived saccharides to 5-hydroxymethylfurfural

Herein, the surface of multi-walled carbon nanotubes (MWCNTs) was functionalized with 3-mercaptopropyltrimethoxysilane followed by anchoring of 1-vinylimidazole on the surface through the thiol–ene click reaction.

HRMAS-NMR and simulation study of the self-assembly of surfactants on carbon nanotubes.

Polyethoxylated surfactants, such as those of the Tween and Pluronic series, are commonly used to disperse carbon nanotubes (CNTs) and other nanoparticles. However, the current understanding of the nature of interactions between these surfactants and CNTs is limited. The nature of the interactions between surfactants (Tween-80 [T80] and Pluronic F68 [PF68]) and CNTs was investigated using high-resolution magic angle spinning nuclear magnetic resonance (HRMAS-NMR) and coarse-grained molecular dynamics (MD) simulations. HRMAS-NMR revealed that T80 molecules interact with single-walled CNTs (SWCNTs) and multi-walled CNTs (MWCNTs) via the oleyl chain, whereas PF68 molecules interact with the surface of SWCNTs and MWCNTs via the polypropylene oxide residues. The polyethylene oxide chains were oriented towards the external aqueous environment. The HRMAS-NMR results were supported by MD simulations, and the latter provided further insights into the nature of the interactions.

Poly(N-vinyl triazole-b-N-vinyl imidazole) Grafted on MWCNTs as Nanofillers to Improve Proton Conducting Membranes

Carbon nanotubes (CNTs) are of particular interest because of their ability to enhance the mechanical strength in the material; however, processing difficulties of CNTs often restrict utilization up to its full potential. To resolve this, in the current study, we have developed a simple and efficient method to functionalize the surface of a multiwalled carbon nanotube (MWCNT) with precise functional polymer chains, which were covalently grafted on the surface of the MWCNT, and delved into an application to demonstrate this material as an efficient nanofiller in developing a proton conducting membrane (PEM) from polybenzimidazole (PBI). At first, the MWCNT surface was converted to a polymerizable surface by attaching a trithiocarbonate based chain transfer agent (CTA). Then, a N-heterocyclic block copolymer, namely poly-N-vinyl-1,2,4-triazole-b-poly-N-vinyl imidazole (pNVT-b-pNVI), was grown from the CTA anchored surface with a one-pot surface initiated reversible addition–fragmentation chain transfer (SI-RAFT) technique. Grafting of block copolymer chain was confirmed by GPC, NMR, TGA, TEM, FESEM, and EDX studies. To the best of our knowledge, this will be the first report of a growing block copolymer structure grafted covalently on the surface of the MWCNT. The novelty of the work was further enhanced by incorporating pNVT-b-pNVI-g-MWCNT as a nanofiller into the oxypolybenzimidazole (OPBI) membrane to obtain homogeneous nanocomposite membranes with excellent thermomechanical and tensile properties, thermal stability, superior proton conduction when doped with phosphoric acid (PA), and PA holding capacity. The nanocomposite membrane with 2.5 wt % nanofiller loading displayed a tensile stress of 1.8 MPa and a strain of 176% at break. The basic N-heterocyclic rings dangling from the block copolymer chains grafted on the MWCNT surface allowed formation of strong H-bonding, acid–base interaction with PA, which is responsible for high acid uptake and superior PA retention, and also exhibited proton conductivity as high as 0.164 S cm–1 at 180 °C, which is a 2.6-fold increment when compared with a pristine OPBI membrane. This significant increase in conductivity is attributed to the proton conducting nanochannel pathway generated along the polymer-g-MWCNT surface.

Composite Based on Multi-Walled Carbon Nanotubes and Manganese Oxide with Rhenium Additive for Supercapacitors: Structural and Electrochemical Studies

The structure and electrochemical characteristics of composites based on multi-walled carbon nanotubes (MWCNTs) and manganese oxide with the addition of rhenium oxide has been studied. It has shown that the decorating of the MWCNT surface with layers or nanoparticles of manganese oxide (Mn(III) + Mn(IV)) provides more than a twofold increase in the value of the specific capacitance at low potential scan rates. However, composites based only on manganese oxide exhibit poor electrochemical behavior and the value of the specific capacitance decreases rapidly with increasing potential scan rate due to the limitation of diffusion processes. The addition of rhenium oxide to composites significantly increases their electrochemical properties due to changes in the chemical composition and morphology of composites. Studies of the structure and chemical state have shown that an improvement in the specific capacitance is provided by increasing in the proportion of Mn(IV) oxide in such composites, which has the ability to rapidly and completely reverse redox reactions and has lower electrical resistance values, compared to Mn(III) oxide. A detailed analysis of the voltammetric data showed that an increase in the rate capability in composites with the addition of rhenium oxide can also be provided by increasing the availability of the electrode surface for electrolyte ions and increasing the amount of charge stored due to the formation of a double electric layer.

Improving reinforcement properties of CNTs in aluminium matrix composites: a case of surface modification through AlN nano-particle grafting

This paper accentuates a newer approach to modify the surfaces of pristine multiwall carbon nanotubes (CNTs) by two-phase acid treatment, followed by silanization and grafting of functionalized AlN nano-particles onto the CNT surfaces, as a preparatory treatment before reinforcing in liquid metallurgy processed aluminium matrix composites (AMCs) without disrupting their structural integrity. Besides, the surface modified CNTs will have the strong potential to improve their dispersion uniformity, wettability and matrix-reinforcement bonding strength in the AMCs. The AlN nano-particle grafted CNTs were characterized through dispersion stability test, UV-Visible spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, Raman spectroscopy and Thermogravimetric analysis (TGA). Microstructure and elemental analysis were conducted through Scanning electron microscope (SEM) embedded with Energy dispersive X-ray spectroscope (EDS), Field emission scanning electron microscope (FESEM) and Transmission electron microscope (TEM). The aforementioned characteristics of AlN nano-particle grafted CNTs were compared with those of the pristine CNTs, acid treated CNTs and silanized CNTs to demonstrate the effectiveness of AlN nano-particle grafting on the CNT surfaces. Results revealed improvement of dispersion stability, covalent attachment of AlN nano-particles onto CNT surfaces (FTIR spectroscopy), existence of AlN on the CNT sidewalls (XRD analysis) and peaks corresponding to Al and N (EDS). Evidence of AlN on the CNT surfaces was also established through SEM, FESEM, TEM and EDS. Though there was a paltry degradation of CNT surfaces after the acid treatment, it was recovered substantially during silanization, and there was no evidence of tube shortening or fragmentations in SEM of silanized and AlN grafted CNTs.

Composite proton exchange membranes based on inorganic proton conductor boron phosphate functionalized multi-walled carbon nanotubes and chitosan

Super inorganic proton conductor boron phosphate (BPO4) was utilized to functionalize the multi-walled carbon nanotubes (MWNTs) through a convenient sol-gel method with the assist of polydopamine (PDA) to yield BPO4 coated MWNTs (BPO4@MWNTs). Then the BPO4@MWNTs was dispersed in dilute chitosan (CTS) solution to fabricate CTS/BPO4@MWNTs composite membrane. The CTS/BPO4@MWNTs composite membranes showed superior performances in thermal stability, mechanical property and oxidation stability due to the well-dispersed BPO4@MWNTs in CTS matrix and the optimized interface compatibility between the BPO4@MWNTs and the CTS matrix. Moreover, BPO4 coated on the surface of MWNTs can provide an extra proton conducting pathway render the CTS/BPO4@MWNTs-2 composite membrane showed the proton conductivity of 0.040 S cm−1 at 80 °C and the maximum power density of 49.0 mW cm−2 at 70 °C and 2 M methanol concentration much higher than that for original CTS membranes.

The effect of acid treated multi-walled carbon nanotubes on the properties of cement paste prepared by ultrasonication with polycarboxylate ester

Chemical functionalization of carbon nanotubes by the mix of sulfuric (H2SO4) and nitric (HNO3) acids has been reported to enhance the hydrophilicity of carbon nanotubes, which, in turn, improves its dispersion quality in aqueous solution and within the cement matrix. In this study, multi-walled carbon nanotubes (MWCNT) were treated by a mix of H2SO4 and HNO3, and used for preparation of MWCNT solutions by ultrasonic tip sonication with low amounts of polycarboxylate ester (PCE). The effects of acid functionalization on the dispersion of MWCNT, mechanical performance and hydration of cement paste were studied with respect to changes in MWCNT concentration, ultrasonication time and MWCNT:PCE ratio. According to the experimental results, acid-treated MWCNT contained 13 wt% of carboxyl functional group. The results from Raman spectroscopy showed the increased amount of unadsorbed PCE in solution with acid-treated MWCNT due to the increase in hydrophilicity. Increase in hydrophilicity contributed to a stronger bond between a-MWCNT and cement hydration products, and increased the mechanical strength of cement paste by 55%. The addition of a-MWCNT at 0.1 wt% concentration resulted in the increase of 28-day compressive strength from 40 MPa up to 62 MPa and flexural strength from 4.4 MPa up to 7.6 MPa. Retardation in hydration and increase in porosity were found to be associated with PCE that was not adsorbed on the surface of MWCNT.

Pd-Ce-Ox species on MWCNTs surface: Probing the structure-activity correlation in low-temperature CO oxidation

Herein, the highly dispersed palladium and ceria species were deposted on the surface of multi-walled carbon nanotubes (MWCNTs) by co-deposition from acetone solutions. The use of MWCNTs allowed varying Pd/Ce atomic ratio in a wide range, while maintaining a high dispersion of the active components. Application of physicochemical methods revealed the formation of various palladium species. Single Pd2+ ions dispersed in CeO2 lattice were the main Pd-Ce-Ox species at low Pdat/Ceat ratio. With an increase of the Pd content in the samples the preferential formation of PdO particles in a tight contact with CeO2 nanoparticles was observed. The size of PdO and CeO2 primary particles was in a range of 1–5 nm.The Pd-Ce-Ox/MWCNTs samples showed high activity in the CO oxidation reaction already at room temperature with a temperature of 50% CO conversion below 100 °C. The Pd2+-CeO2 and PdO-CeO2 species demonstrated the comparable activity in “dry” CO oxidation. However, the presence of water vapor in the reaction mixture resulted in the immediate deactivation of Pd2+-CeO2 species, while PdO-CeO2 species retained a high activity at 20°С. The results of the work highlight the benefits of MWCNTs, Pd, and CeO2 combination for obtaining catalysts highly active in CO oxidation.

Multi-walled carbon nanotubes as a platform for Immunoglobulin G attachment

Nanomaterials have been extensively used in different applications due to their peculiar characteristics and nanoscale dimensions. Among nanoparticles, carbon-based nanomaterials are becoming highly attractive for biomedical applications such as diagnosis, tissue engineering, drug delivery, and biosensing. The conjugation of carbon-based nanomaterials with antibodies combines the properties of these materials with the specific and selective recognition ability of the antibodies to antigens. The present work proposes a process intensification approach for immunoglobulin G (IgG present in rabbit serum) attachment on multi-walled carbon nanotubes (MWCNTs) in a single step. The effect of several parameters, namely MWCNTs external diameter, rabbit serum concentration, MWCNTs functionalization and pH value, on the IgG attachment yield was evaluated. The dilution of rabbit serum decreased other protein attachment, namely rabbit serum albumin (RSA), while increasing the IgG yield to 100%. The interaction mechanisms between IgG and MWCNTs were evaluated at pH 5.0 to 8.0. The protonation of IgG amino acids indicates that N-term are the most reactive amino acids in the antibody structure. The identification of the N-term reactivity at pH 8.0 allows to indicate a possible orientation of the antibody over the MWCNTs surface, described as “end-on”. Since the amount of RSA attached to MWNT decreased with the increase in serum dilution, the IgG orientation and amine activity was not affected. This orientation demonstrates that the IgG attachment over the surface of the MWCNTs could be an effective strategy to maintain the antigen recognition by the antibody, and to be used for biomedical applications.

Fabrication of an intelligent anti-corrosion silane film using a MoO42− loaded Micro/mesoporous ZIF67-MOF/multi-walled-CNT/APTES core-shell nano-container

The design of smart coatings for corrosion protection aims has become one of the most interesting hotspots for contemporary corrosion researchers. For this purpose, scientists mostly grabbed on the utilization of carriers with control-release capability, and carbonaceous materials are the most well-known celebrities among all. In this work, the multi-walled carbon nanotube (CNT) surface was decorated with ZIF67 crystals, and then MoO42− ions (Mo) were loaded into the constructed nano-carrier. Eventually, the synthesized particles' were covered by (3-Aminopropyl) triethoxysilane (APTES) amino silane for better dispersion in the silane matrix. The silanized and un-modified nano-hybrids were precisely explored by different characteristic methods to prove their successful synthesis. Also, the inductively coupled plasma (ICP) measurements demonstrated around 49 ppm, 18 ppm, and 0.02 ppm Co ions in the acidic, neutral, and alkaline conditions, respectively. The Electrochemical Impedance Spectroscopy (EIS) and polarization records in the solution phase revealed that CNT-ZIF67-Mo nano-hybrids successfully declined the corrosion rate of metal up to 91% and 84%, respectively. Thereupon, to design a self-healable anti-corrosion system, CNT-ZIF67-Mo particles at 0.15 wt% were incorporated into the silane-based hybrid coating. The EIS explorations carried out on the scratched composites proved that the total resistance was tripled and self-healing activity with a 69% index was visualized after the inclusion of APTES/CNT-ZIF67-Mo nanoparticles. Also, the EIS investigations over the intact composites declared that the silane coating resistance was increased from 23156 Ω.cm2 to 200169 Ω.cm2 and water uptake was around 73% upon the incorporation of APTES/CNT-ZIF67-Mo nanoparticles.

High-Performance Ionanofluids from Subzipped Carbon Nanotube Networks

Investments in the transfer and storage of thermal energy along with renewable energy sources strengthen health and economic infrastructure. These factors intensify energy diversification and the more rapid post-COVID recovery of economies. Ionanofluids (INFs) composed of long multiwalled carbon nanotubes (MWCNTs) rich in sp2-hybridized atoms and ionic liquids (ILs) display excellent thermal conductivity enhancement with respect to the pure IL, high thermal stability, and attractive rheology. However, the influence of the morphology, physicochemistry of nanoparticles and the IL-nanostructure interactions on the mechanism of heat transfer and rheological properties of INFs remain unidentified. Here, we show that intertube nanolayer coalescence, supported by 1D geometry assembly, leads to the subzipping of MWCNT bundles and formation of thermal bridges toward 3D networks in the whole INF volume. We identified stable networks of straight and bent MWCNTs separated by a layer of ions at the junctions. We found that the interactions between the ultrasonication-induced breaking nanotubes and the cations were covalent in nature. Furthermore, we found that the ionic layer imposed by close MWCNT surfaces favored enrichment of the cis conformer of the bis(trifluoromethylsulfonyl)imide anion. Our results demonstrate how the molecular perfection of the MWCNT structure with its supramolecular arrangement affects the extraordinary thermal conductivity enhancement of INFs. Thus, we gave the realistic description of the interactions at the IL-CNT interface with its (super)structure and chemistry as well as the molecular structure of the continuous phase. We anticipate our results to be a starting point for more complex studies on the supramolecular zipping mechanism. For example, ionically functionalized MWCNTs toward polyionic systems─of projected and controlled nanolayers─could enable the design of even more efficient heat-transfer fluids and miniaturization of flexible electronics.

A Study on the Effects of Potassium Permanganate on the Functionalization of Multi-Walled Carbon Nanotubes

In this work, multi-walled carbon nanotubes (MWCNTs) are functionalized by a wet chemical oxidation method using a mixture of potassium permanganate (KMnO4) and sulfuric acid (H2SO4) at 70 °C, for 12 h. The effects of various KMnO4 amounts on the functionalization of MWCNTs are studied and reported. The surface morphologies, structural properties, dispersion and thermal stability of the MWCNTs are characterized using a field emission scanning electron microscope (FE-SEM), Raman spectroscopy, UV-visible spectroscopy (UV–vis), thermal gravimetric analysis (TGA). The FE-SEM images display some surface roughness, cutting and open ends of functionalized MWCNTs (f-MWCNTs). The TGA curves of f-MWCNTs indicate a weight loss between 150 °C and 350 °C, which is attributed to the loss of carboxyl groups on the MWCNTs surface and the weight loss is increased when KMnO4 mass is increased. The highest weight loss value of 22.23% is recorded for the oxidation treatment with a mixture of 5 M H2SO4 and 200 mg KMnO4. UV–vis measurements indicate that the f-MWCNTs are highly dispersed in the aquoues solution in comparision to the pristine MWCNTs (p-MWCNTs). And f-MWCNTs with higher functionalization degree show better dispersibility. This study provides a great prospect of effective method to cut, end-open, functionalize and disperse MWCNTs.

A facile approach for grafting ion imprinted polymer onto magnetic multi-walled carbon nanotubes for selective removal and preconcentration of cadmium in food and wastewater samples prior to atomic spectrometric determination

A 3D Fe3O4@MWCNT-CdIIP was synthesized by the oxidizing surface of multi-walled carbon nanotubes with carboxylic acid end groups and its subsequent termination with an ion imprinted polymer. An artificial neural network manifests better predictability than the central composite design methodology for optimising the adsorption procedure. The adsorption capacity was 109 mg g−1 (2.5 times more than non-imprinted polymer) under optimized conditions (pH; 5.6, time; 15 min, concentration; 800 μg mL−1 temperature; 25 °C), which was in accord with Toth isotherm. Fractal-like pseudo-second-order kinetics was found reasonably fast, with 66 % adsorption in 5 min. Solid phase extraction coupled Flame atomic absorption spectrometry method provides selective recognition towards Cd(II), with limit of detection; 1.13 µg/L, limit of quantification; 3.21 µg/L after preconcentration (preconcentration factor; 50) and good robustness. The developed method was applied for Cd(II) determination in food (tea, coffee, bread, tobacco, radish, spinach), water and wastewater (>99 % removal as well). Cd(II) loaded IIP was further utilized to remove anionic dyes with >95 % removal.

In Situ Activation of Superhydrophobic Surfaces with Triple Icephobicity at Low Temperatures.

Superhydrophobic surfaces have been widely studied due to their potential applications in aerospace fields. However, superhydrophobic surfaces with excellent water-repellent, anti-icing, and icephobic performances at low temperatures have rarely been reported. Herein, superhydrophobic surfaces with heating capability were prepared by etching square micropillar arrays on the surface of multiwalled carbon nanotube (MWCNT)/poly(dimethylsiloxane) (PDMS) films. The fabricated superhydrophobic surface has triple icephobicity, which can be activated even at low temperatures. The triple icephobicity is triggered by an applied voltage to achieve excellent water-repellent and icephobic capabilities, even at -40 °C. Additionally, theoretical calculations reveal that a droplet on a superhydrophobic surface loses heat at a rate of 8.91 × 10-5 J/s, which is 2 orders of magnitude slower than a flat surface (2.15 × 10-3 J/s). Also, at -40 °C, the mechanical interlocking force formed between the superhydrophobic surface and ice can be released by the heating property of the superhydrophobic surface. This low-energy, multifunctional superhydrophobic surface opens up new possibilities for bionic smart multifunctional materials in icephobic applications.

Effect of Extremely Short-Sized MWCNT as Additive Material in High Surface Area Activated Carbon and Its Enhanced Electrical LIC Performance.

Extremely short-sized multi-wall carbon nanotube (CNT) and high surface area activated carbon were used to increase the electrical performance of lithium-ion capacitors (LIC). After electrodes were synthesized using extremely short-sized CNTs and high specific surface area activated carbon, their electrochemical characteristics were evaluated by XRD, SEM, TEM, cyclic voltammetry, EIS, BET, adoption isotherm, t-plot, and pore size distribution. In the process of electrode preparation using extremely short-sized CNTs and high specific surface area activated carbon, CNTs certainly caused a space-filling effect between these two materials, which had a significant effect on the evaluation of electrical characteristics. These relationships were demonstrated by the results of adsorption–desorption isotherm, pore size distribution, t-plot, and BJH plot. Particularly, in the electrochemical cyclic test, as the content of CNT increased, the current density significantly increased with the formation of a near-perfect rectangular shape. This tendency also exhibited excellent characteristics in a t-I plot, Tafel plot, and LSV plot, which clearly affected the electrochemical oxidation–reduction reaction due to the densification of filling density and space structure by adding extremely short-sized CNTs to the active material. In addition, YP80_CNT3 formed a specific resistance value in the range of 7.2 to 6.2 Ω/cm2, showing significantly reduced values compared to other samples. This research presented herein offers a promising route for the rational design of MWCNT and stable electrochemical reaction with LIC working mechanism.

Sonochemical fabrication of a hybrid electrode material based on pristine carbon nanotubes and bentonite clay for fast and highly sensitive determination of dopamine in the presence of ascorbic and uric acid

This work focuses on the attachment of bentonite clay to external surface of individual pristine multiwalled carbon nanotubes (MWCNTs) and the use of the resulting hybrid material for the fast and highly sensitive electrochemical determination of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA). XRD, FE-SEM and EDX highlighted the pristine state of MWCNTs and bentonite clay. HR-TEM confirmed the adsorption of clay on the external surfaces of individual pristine MWCNTs. Electrochemical characterization showed that the fabricated sensor possesses a large electrochemical surface area with excellent electron transfer properties. The influence of parameters likely to affect sensor performance was studied; 40 s, 10 μL suspension, and pH 7.4 were found to be the optimal accumulation time, optimal suspension volume, and optimal electrolyte pH, respectively. Under these optimal conditions, DPV peak currents were linearly related to DA concentrations in the range of 0.4–14 μM, and the detection limit was found to be 6 nM (S/N = 3). The Interference study revealed that the sensor eliminates AA and UA interference up to concentrations above their blood levels. Furthermore, the developed sensor exhibited good repeatability, satisfactory long-term stability, and was successfully applied to the detection and quantification of DA in human serum sample with satisfactory recoveries.

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

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

Cubic MnSe2 nanoparticles dispersed on multi-walled carbon nanotubes: A robust electrochemical sensing platform for chloramphenicol

A robust electrochemical sensor for chloramphenicol has been constructed by cubic MnSe 2 nanoparticles decorated on multi-walled carbon nanotubes. • MnSe 2 nanoparticles were firstly synthesized by a one-step hydrothermal process. • MnSe 2 /MWCNTs shows excellent synergistically catalytic properties towards CAP redox. • MnSe 2 /MWCNTs /GCE displays wide detection range for CAP sensing. • Detection of CAP in food and biological fluids was implemented. In this work, cubic MnSe 2 nanoparticles were firstly synthesized through a simple one-step hydrothermal procedure at low temperature using N 2 H 4 ·H 2 O as a reductant as well as MnCl 2 and Se powders as precursors. The crystalline structure, morphology, chemical composition, and element valence states of the synthesized samples were specifically investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray photoelectron spectra (XPS), and Raman spectroscopy. It was found that the MnSe 2 product mainly exists in a roughly cubic morphology with the sizes between 20 and 50 nm. In order to alleviate the aggregation, cubic MnSe 2 nanoparticles were further ultrasonically dispersed on the surface of multi-walled carbon nanotubes (MWCNTs) to achieve an improved stability structure denoted as MnSe 2 /MWCNTs. Compared with the single components, the MnSe 2 /MWCNTs composite displays enhanced electrochemical sensing signals for chloramphenicol (CAP) derived from the synergistic catalytic performance of the corresponding components. After optimization of electrochemical assay parameters, an assay range of 8.00–5000.00 μM and a limit of detection (LOD) with 2.00 μM for CAP were obtained using the MnSe 2 /MWCNTs-based sensor. Finally, the application of the resulting sensor for CAP detection in food and biological fluids was evaluated with recoveries between 94.70 and 106.70 %, demonstrating that MnSe 2 /MWCNTs could be served as a preeminent sensing platform. To the best of our knowledge, this is the first report on the fabrication of MnSe 2 -based composite for electrochemical sensing applications.

Effect of MWCNTs surface functionalization group nature on the thermoelectric power factor of PPy/MWCNTs nanocomposites

This work aims to put forward the role of multiwalled carbon nanotubes (MWCNTs) surface functionalization on the enhancement of thermoelectric (TE) power factor of new nanocomposite-based polypyrrole/surface modified multiwalled carbon nanotubes (PPy/MWCNTs), prepared by a facile in-situ oxidative polymerization process. In fact, MWCNTs’ content was fixed to ∼11 wt%, and their surfaces were respectively modified with different functional groups (benzoic acid (-D1), benzene tricarboxylic acid (-D3), -O, -COOH, -NH2 and -SH). After running all the required, spectral, structural, morphological, and thermoelectrical characterizations, it is revealed that the nanocomposites-based functionalized MWCNTs remarkably increase the Seebeck coefficient, and thus enhancing the material’s power factor. This improvement of TE power factor was attributed to the coating homogeneity and the good interaction between PPy and MWCNTs mainly through π–π stacking between the polymer chains and the nanotubes as well as electrostatic, hydrogen bonding, and electrons donor/acceptor groups interactions due to the functional groups grafted on the nanotube’s sidewall. The highest power factor value (0.51 μWm−1K−2) was obtained with PPy/MWCNTs-SH, which means an enhancement of 8 folds compared to pure PPy. Considering the content of MWCNTs and the ease of preparation process, these results might help to develop future TE materials and devices.