Multi-walled Carbon Nanotubes COOH Research Articles

A nano curcumin-multi-walled carbon nanotube composite as a fluorescence chemosensor for trace determination of celecoxib in serum samples.

A novel method is presented here for trace determination of celecoxib by fluorescence detection using curcumin nanoparticles (CurNPs) loaded on multi-walled carbon nanotubes with carboxyl functional groups (CurNPs-MWCNT-COOH). For the synthesis of CurNPs-MWCNT-COOH, CurNPs were retained on carbon nanotubes with the aid of ultrasound waves. The sensing method is based on monitoring the quenching of synthesized CurNPs-MWCNT-COOH fluorescence by celecoxib. The morphology of CurNPs-MWCNT-COOH was studied by transmission electron microscopy (TEM) of the composite alone and in the presence of celecoxib. The effects of several parameters on the production of CurNPs-MWCNT-COOH and determination of celecoxib such as the Triton X-100 concentration, the amount of MWCNT-COOH and the pH were evaluated and optimum conditions were established. The calibration graph was found to be linear in the range of 20-220 ng mL-1 for celecoxib in the initial solution. The detection limit based on three times the standard deviation of the blank was 5.8 ng mL-1 for celecoxib and relative standard deviations (RSD) of 3.6% and 1.8% were obtained for eight replicate determinations of 60 ng mL-1 and 180 ng mL-1 of celecoxib, respectively. The method was applied to the determination of celecoxib in serum samples.

Preparation of Ultrafiltration Membrane by Polyethylene Glycol Non-Covalent Functionalized Multi-Walled Carbon Nanotubes: Application for HA Removal and Fouling Control.

Polyethylene glycol (PEG) non-covalent-functionalized multi-walled carbon nanotubes (MWCNT) membrane were prepared by vacuum filtration. The dispersion and stability of MWCNT non-covalent functionalized with PEG were all improved. TEM characterization and XPS quantitative analysis proved that the use of PEG to non-covalent functionalize MWCNT was successful. SEM image analysis confirmed that the pore size of PEG–MWCNT membrane was more concentrated and distributed in a narrower range of diameter. Contact angle measurement demonstrated that PEG non-covalent functionalization greatly enhanced the hydrophilicity of MWCNT membranes. The results of pure water flux showed that the PEG–MWCNT membranes could be categorized into low pressure membrane. PEG-MWCNT membrane had a better effect on the removal of humic acid (HA) and a lower TMP growth rate compared with a commercial 0.01-μm PVDF ultrafiltration membrane. During the filtration of bovine serum albumin (BSA), the antifouling ability of PEG-MWCNT membranes were obviously better than the raw MWCNT membranes. The TMP recovery rate of PEG–MWCNT membrane after cross flushing was 79.4%, while that of raw MWCNT–COOH and MWCNT membrane were only 14.9% and 28.3%, respectively. PEG non-covalent functionalization improved the antifouling ability of the raw MWCNT membranes and reduced the irreversible fouling, which effectively prolonged the service life of MWCNT membrane.

Simultaneous enhancement in thermal conductivity and flame retardancy of flexible film by introducing covalent bond connection

Owing to the high interface thermal resistance and aggregation in polymer-based materials, the thermal conductivity of multi-walled carbon nanotubes (MWCNTs) has been severely decreased in practical applications. In this work, an amino-functionalized black phosphorene (BP–NH 2 ) fabricated by ball milling has been employed to react with carboxylated multi-wall carbon nanotubes (MWCNTs–COOH) via covalent bonds to prepare a nanofiller (BP–MWCNTs) with high thermal conductivity and excellent flame retardancy. When incorporating 20.0 wt% BP–MWCNTs into cellulose nanofiber (CNF), the CNF/BP–MWCNTs 20.0 shows an in-plane thermal conductivity of 22.38 ± 0.39 W m −1 K −1 and a cross-plane thermal conductivity of 0.36 ± 0.03 W m −1 K −1 , resulting in an anisotropy index of 62.17. The effective medium theory (EMT) calculation demonstrates the interface thermal resistance is reduced to 1/39 that of pure MWCNTs, which is ascribed to the covalent bond between BP–NH 2 and MWCNTs–COOH. Simultaneously, the CNF/BP–MWCNTs 20.0 can pass the testing of UL-94 V-0 grade and the limiting oxygen index (LOI) value can be increased from 18.1% to 29.9%. Its peak of heat release rate (PHRR), total heat release (THR), smoke production rate (SPR), total smoke production (TSP), CO generated per second (COP) and CO 2 generated per second (CO 2 P) are decreased by 37.47%, 43.51%, 50.00%, 35.29%, 50.00% and 19.70%, respectively, which is due to the formation of an intumescent flame-retardant system rich in carbon source (MWCNTs), acid source (BP) and gas source (amino groups). This covalent linkage strategy offers a new thought for the preparation of flexible materials to enhance the thermal conductivity and fire resistance. • Aminated black phosphorene was successfully fabricated by ball milling. • Interface thermal resistance was significantly reduced. • Desirable thermal conductivity was obtained. • Efficient intumescent flame-retardant system was prepared.

MWCNT and COOH–MWCNT aqueous nanofluids: thermophysical and rheological characterization

The nanofluids characterization is of fundamental importance to predict their applicability in a real heat transfer situation. In addition to the transport properties, the nanofluid stability is an important factor to be studied, due to the long pumping, heating, cooling and resting cycles the fluids are usually subjected to. Carbon nanotubes have great potential to be used in nanofluids, due to their high thermal conductivity and low density. However, for aqueous medium, stability requires the use of stabilization methods. This work carried out the study of the transport properties and stability of nanofluids with multiwalled carbon nanotubes (MWCNT), using three stabilization methods: Triton X-100 (TrX–MWCNT) and Arabic gum (AG–MWCNT) as surfactants and functionalized carbon nanotubes with COOH group (COOH–MWCNT). These three nanofluids were compared to investigate the best configuration for heat transfer processes. The thermal conductivity was studied using the hot wire method; rheology was studied through three curves in rotational rheometer of concentric cylinders; specific heat was studied by the differential scanning calorimetry method; density was measured by the Coriolis Effect method; nanoparticles size and zeta potential were measured by the dynamic light scattering method. The COOH–MWCNT nanofluids present the highest thermal conductivity increase reaching 15% at 60 °C and 12% at 30 °C with 1wt% while the A.G–MWCNT and TrX–MWCNT reach 11% and 7.5%, respectively, at 30 °C. A.G–MWCNT nanofluids showed greater stability after long sonication times, while COOH–MWCNT presents best dispersion at 0.125 and 0.25 wt%, from 40 to 160 min of sonication. The specific heat increases with temperature and decreases with MWCNT concentration; however, it presents a peculiar increase in the concentration of 0.25 wt%, increasing about 0.5% and 4.5% for A.G–MWCNT and COOH–MWCNT, respectively at 60 °C. COOH–MWCNT nanofluids showed a thixotropic behavior for 0.5 and 1.0 wt% and large viscosity increase reaching 3.75 and 5.5 times the base fluid viscosity at 5 °C and 60 °C, respectively, with 1 wt%. The nanofluids A.G–MWCNT and COOH–MWCNT present good stability, as well as an increase in transport properties, optimized at a concentration close to 0.25 wt% and the COOH–MWCNT nanofluids can be stabilized simply by changing the water pH.

Data of preparation and evaluation of supramolecular hydrogel based on cellulose for sustained release of therapeutic substances with antimicrobial and wound healing properties.

The data article refers to the paper “supramolecular hydrogel based on cellulose for sustained release of therapeutic substances with antimicrobial and wound healing properties”[1]. The dataset includes the synthesis and characterization of (E)-1,3-bis(4-(allyloxy)phenyl)prop‑2-en-1-one (3) (crosslinking agent). Moreover, the multiwall carbon nanotubes (MWCNTs) synthesis and functionalization (MWCNTs-COOH) are described. The formulation obtained by adding multiwalled carbon nanotubes-COOH with the crosslinked cellulose-chalcone hydrogel is abbreviated as MWCNTsCCH, and the same formulation loaded with therapeutic substances (TS) is named MWCNTsCCH-TS. The MWCNTsCCH database such as components and their amounts, swelling degree, thermogravimetric analysis, and cytotoxicity evaluation are depicted. Finally, to elucidate the mechanism of therapeutic substances release, the obtained averages of the release profiles were fitted through mathematical models.

Multi-walled carbon nanotubes induce IL-1β secretion by activating hemichannels-mediated ATP release in THP-1 macrophages

Multi-walled carbon nanotubes (MWCNTs) are known to induce pulmonary inflammatory effects through stimulating pro-inflammatory cytokine secretion from alveolar macrophages. Despite extensive studies on MWCNTs’ pro-inflammatory reactivity, the understanding of molecular mechanisms involved is still incomplete. In this study, we investigated hemichannel’s involvement in MWCNTs-induced macrophage IL-1β release. Our results showed that the unmodified and COOH MWCNTs could induce ATP release and ATP-P2X7R axis-dependent IL-1β secretion from THP-1 macrophages. By using various inhibitors, we confirmed that the MWCNTs-induced ATP release was primarily through hemichannels. EtBr dye uptake assay detected significant hemichannels opening in MWCNTs exposed THP-1 macrophages. Inhibition of hemichannels by CBX, 43Gap27, or 10Panx1 pretreatment results in decreased ATP and IL-1β release. The addition of ATP restored the reduced IL-1β secretion level from hemichannel inhibition. We also confirmed with five other types of MWCNTs that the induction of hemichannels by MWCNTs strongly correlates with their capacity to induce IL-1β secretion. Taken together, we conclude that hemichannels-mediated ATP release and subsequent NLRP3 inflammasome activation through P2X7R may be one mechanism by which MWCNTs induce macrophage IL-1β secretion. Our findings may provide a novel molecular mechanism for MWCNTs induced IL-1β secretion.

Pyrenyl Carbon Nanotubes for Covalent Bilirubin Oxidase Biocathode Design: Should the Nanotubes be Carboxylated?

Understanding the characteristics of nanomaterials in the context of electrode designs for bio-electrocatalysis is an emerging research direction. Applications for fuel cells, batteries, and biosensors are directly benefited. The objective of this study is to understand the influence of unfunctionalized multiwalled carbon nanotubes (MWNT) in comparison to carboxylated nanotubes (MWNT–COOH) for pi-pi stacking with 1-pyrenebutyric acid (Py) and covalent immobilization of bilirubin oxidase (BOD) enzyme toward the resulting oxygen reduction currents. We designed pyrolytic graphite-edge electrodes modified with MWNT/Py, MWNT–COOH/Py, or only MWNT–COOH for carbodiimide activation and BOD immobilization. The relative increase in surface –COOH groups as we move from MWNT to MWNT/Py to MWNT–COOH/Py modification is voltammetrically estimated. Although the MWNT–COOH/Py displayed the highest relative amount of surface −COOH groups, the oxygen reduction current was the largest for the BOD-immobilized MWNT/Py electrode than others. Results indicate that unfunctionalized MWNT is the optimal choice for pi-pi stacking with pyrene linkers and covalent BOD immobilization as biocathode for direct electrocatalysis with high current densities. Favorable hydrophobic MWNT surface to interact more closely with the electron-receiving T1 Cu site of BOD, as opposed to the relatively polar and more defective MWNT–COOH material due to functionalization, is suggested to be one of the underlying factors for the observed electrocatalytic trend.

Saccharine based carbonyl multi-walled carbon nanotubes: novel modification, characterization and its ability for removing Cd(II) and Cu(II) from soil and environmental water samples

This research highlights the chemical modification of one of the carbon nanostructures (multi-walled carbon nanotubes-COOH) with an artificial sweetener (saccharine) to synthesize a highly efficient absorbent material (MWCNTs-CO-Sac). This material was thereafter used to the packing column in solid phase extraction of cadmium and copper divalent ions from real samples. This nano-adsorbent was diagnosed with different techniques: infrared spectroscopy (FTIR), Thermogravimetry (TG), Differential thermal analysis (DTA), powder X-ray diffraction (PXRD), energy-dispersive X-ray spectroscopy (EDX), Particle size distribution (PSD) and scanning electron microscopy (SEM). The effect of pH, sample and eluent flow rates, volume, type and concentration of eluent, volume of sample and interfering ions were studied to achieve the optimal conditions for solid phase extraction of Cd(II) and Cu(II) based on the inductively coupled plasma-optical emission spectrometry (ICP-OES). Moreover, the preconcentration factors were calculated to be 75. The results of a limit of detection (LOD) 0.07 μgL−1 and 0.09 μgL−1 for Cd(II) and Cu(II) respectively. The relative standard deviation (RSD %) of this study was 0.45% for Cd(II) and 0.51% for Cu(II). The optimized method was applied to soil and environmental water samples.

Enhanced hardness of nickel coating reinforced functionalized carbon nanomaterials via an electrodeposition technique

In this paper, the nickel (Ni) coatings reinforced carbon nanomaterials including graphene nanoplatelets (GNPs), multi-walled carbon nanotubes (MWCNTs) and MWCNTs/GNPs hybrid material prepared by the electrodeposition technique were investigated. GNPs and MWCNTs were functionalized with carboxylic (–COOH) function groups (GNPs–COOH, MWCNTs–COOH) then uniformly dispersed into Watts solution for the electrodeposition process. The obtained results revealed that the microhardness of the Ni coating reinforced COOH functionalized carbon nanomaterials is much improved compared to the bare Ni coating and Ni coating containing carbon nanomaterials without functional groups. The Ni coating containing MWCNTs–COOH/GNPs–COOH hybrid material showed the highest hardness value of 270 HV that is higher 44.7% compared to the bare Ni coating. The enhancement was attributed to the uniform dispersion of functionalized carbon nanomaterials in Ni matrix, the synergistic strengthening effect of the MWCNTs and GNPs, the grain refinement of Ni matrix and the enhanced load transfer effect from Ni matrix to MWCNTs and GNPs via atomic bonding during the electrodeposition process.

New insights about reactive red 141 adsorption onto multi–walled carbon nanotubes using statistical physics coupled with Van der Waals equation

In this communication, statistical physics models (sta–phy) coupled with the Van der Waals (VDW) state equation were employed to demonstrate insights regarding the reactive red 141 (RR 141) adsorption onto multi–walled carbon nanotubes (MWCNTs). Experimental isotherms were constructed for two types of carbon nanotubes (MWCNTs–OH and MWCNTs–COOH) at four different temperatures (298, 308, 318 and 328 K). These curves were predicted by sta–phy models coupled or not with the VDW state equation. It was demonstrated that the sta–phy coupled with VDW equation was able to predict the experimental isotherms more accurately than the other used models. Based in this approach, insights about RR 141 adsorption on the MWCNTs were presented considering the following parameters: number of molecules adsorbed at first and second site (n1 and n2), density of first and second receptor site (Nm1 and Nm2), concentration at half saturation relative to the first and second receptor site (W1 and W2) and VDW interaction parameters (a and b). The Van der Waals parameter related with the co–volume of the adsorbate molecule (b) was significant and ranged from 0.00001 to 0.00302 L mg−1.

Airway Exposure to Modified Multi-walled Carbon Nanotubes Perturbs Cardiovascular Adenosinergic Signaling in Mice.

The broad list of commercial applications for multi-walled carbon nanotubes (MWCNT) can be further expanded with the addition of various surface chemistry modifications. For example, standard commercial grade MWCNT (C-grade) can be carboxylated (COOH) or nitrogen-doped (N-doped) to suite specific utilities. We previously reported dose-dependent expansions of cardiac ischemia/reperfusion (I/R) injury, 24h after intratracheal instillation of C-grade, COOH, or N-doped MWCNT in mice. Here, we have tested the hypothesis that airway exposure to MWCNT perturbs cardiovascular adenosinergic signaling, which could contribute to exacerbation of cardiac I/R injury. 100µL of Vehicle or identical suspension volumes containing 100µg of C-grade, COOH, or N-doped MWCNT were instilled into the trachea of CD-1 ICR mice. 1 day later, we measured cyclic adenosine monophosphate (cAMP) concentrations in cardiac tissue and evaluated arterial adenosinergic smooth muscle signaling mechanisms related to nitric oxide synthase (NOS) and cyclooxygenase (COX) in isolated aortic tissue. We also verified cardiac I/R injury expansion and examined both lung histology and bronchoalveolar lavage fluid cellularity in MWCNT exposed mice. Myocardial cAMP concentrations were reduced (p < 0.05) in the C-grade group by 17.4% and N-doped group by 13.7% compared to the Vehicle group. Curve fits to aortic ring 2-Cl-Adenosine concentration responses were significantly greater in the MWCNT groups vs. the Vehicle group. Aortic constrictor responses were more pronounced with NOS inhibition and were abolished with COX inhibition. These findings indicate that addition of functional chemical moieties on the surface of MWCNT may alter the biological responses to exposure by influencing cardiovascular adenosinergic signaling and promoting cardiac injury.

New insights into the adsorption of crystal violet dye on functionalized multi-walled carbon nanotubes: Experiments, statistical physics and COSMO–RS models application

Two multi–walled Carbon Nanotubes (MWCNTs) adsorbents, chemically functionalized by either OH (MWCNTs–OH) or COOH (MWCNTs–COOH), were adopted to study the adsorption of Crystal Violet (CV) dye from aqueous solutions. A series of CV dye adsorption isotherms was recorded at different temperatures ranging from 298 to 328K. Experimental results demonstrated that the adsorbents have similar performances, even if the sample functionalized by COOH (MWCNTs–COOH) shows slightly higher adsorption capacity. In light of the statistical physics, a model was developed and applied to explain the adsorption mechanism and to describe the role of adsorbent functionalization through model parameters. Mathematically, this model was defined by three parameters reflecting the main physicochemical aspects of the adsorption process such as, the number of dye molecules linked per site of adsorbent (nd), an energetic coefficient (w) and the number of occupied receptor site (Km). A very good accordance between the experimental results and the proposed model was observed. The difference in nd values for the two adsorbents can be attributed to the intensity of interactions between dye and the specific functional groups of the adsorbents. An energetic characterization of the systems was carried out by calculating three specific interaction energies of CV dye with the functionalized carbon nanotubes (the electrostatic misfit energy; EMF, the hydrogen–bonding energy; EHB and the Van der Waals energy; EvdW) by application of conductor–like screening model for real solvents (COSMO–RS). The COSMO–RS model clearly indicated that the hydrogen–bonding interaction is the dominant energetic factor in CV dye adsorption. Finally, a good complementarity was retrieved between the results of statistical physics and COSMO–RS models.

Novel temperature and pH dual-sensitive PNIPAM/CMCS/MWCNT semi-IPN nanohybrid hydrogels: Synthesis, characterization, and DOX drug release

ABSTRACTNovel poly(N-isopropylacrylamide)/carboxymethyl chitosan/multiwalled carbon nanotube semi-interpenetrating nanohybrid hydrogels were prepared, and the chemical structure and morphology were characterized. The prepared hydrogels showed temperature and pH dual-responsiveness, and the one containing multiwalled carbon nanotubes (MWCNTs)–COOH possessed high maximal swelling ratios. The phase transition produced at pH of 6.8–7.4 and temperature of 35–40°C, hinging on the system compositions and charge ratios. The hydrogels were used to load hydrophilic anticancer drug, with high entrapped efficiency of about 44%. The drug release changed with temperature, pH, and MWCNTs–COOH contents. The designed hydrogels can be used for site-specific target delivery of protein or hydrophilic anticancer drug.

Influence of different functionalization on mechanical and interface behavior of MWCNTs/NBR sealing composites

Rubber sealants are key components in processing industries. Carbon nanotubes (CNTs), which are randomly dispersed in polymer, are able to generate exciting effects. Focusing on mechanical properties of composites and interface characteristic between the fillers and matrix, carrying out SEM, DMA and uniaxial tensile tests, the tensile strength of the composites with 4 phr (parts by weight per hundred parts of rubber) multiwalled carbon nanotubes (MWNTs) is obviously improved. MWNTs with different functionalization have different influence on the viscoelastic and mechanical properties of the composites. Results indicate that MWNTs–COOH are broken when composites fractured. While MWNTs, MWNTs–OH and MWNTs–NH2 are pulled out from the matrix because interface debonds under the tensile failure. The interfacial shear stress (IFSS) is about 4.7 MPa in composites. The glass transition temperature (Tg) shifts higher temperatures compared to pure NBR (Acrylonitrile-butadiene Rubber). The presence of the nanotubes limite the movement of NBR macromolecules.

Functionalized carbon nanotubes as suitable scaffold materials for proliferation and differentiation of canine mesenchymal stem cells.

In the field of regenerative medicine, numerous potential applications of mesenchymal stem cells (MSCs) can be envisaged, due to their ability to differentiate into a range of tissues on the basis of the substrate on which they grow. With the advances in nanotechnology, carbon nanotubes (CNTs) have been widely explored for use as cell culture substrate in tissue engineering applications. In this study, canine bone marrow-derived MSCs were considered as the cellular model for an in vitro study to elucidate the collective cellular processes, using three different varieties of thin films of functionalized carbon nanotubes (COOH-single-walled CNTs [SWCNTs], COOH-multiwalled CNTs [MWCNTs] and polyethylene glycol [PEG]-SWCNTs), which were spray dried onto preheated cover slips. Cells spread out better on the CNT films, resulting in higher cell surface area and occurrence of filopodia, with parallel orientation of stress fiber bundles. Canine MSCs proliferated at a slower rate on all types of CNT substrates compared to the control, but no decline in cell number was noticed during the study period. Expression of apoptosis-associated genes decreased on the CNT substrates as time progressed. On flow cytometry after AnnexinV-fluorescein isothiocyanate/propidium iodide (PI) staining, total number of apoptotic and necrotic cells remained lower in COOH-functionalized films compared to PEG-functionalized ones. Collectively, these results indicate that COOH-MWCNT substrate provided an environment of low cytotoxicity. Canine MSCs were further induced to differentiate along osteogenic, chondrogenic, and neuronal lineages by culturing under specific differentiation conditions. The cytochemical and immunocytochemical staining results, as well as the expression of the bone marker genes, led us to hypothesize that the COOH-MWCNT substrate acted as a better cue, accelerating the osteogenic differentiation process. However, while chondrogenesis was promoted by COOH-SWCNT, neuronal differentiation was promoted by both COOH-SWNCT and COOH-MWCNT. Taken together, these findings suggest that COOH-functionalized CNTs represent a promising scaffold component for future utilization in the selective differentiation of canine MSCs in regenerative medicine.

Estimation of Concentration of Polymer Dispersant and Carbon Nanotubes in Electrophoretically Deposited Coatings By Means of UV-Vis Absorption Spectroscopy

0.1 g/L Multi walled carbon nanotubes (MWCNTs) were dispersed in isopropyl alcohol (IPA) with the aid of polyvinylpyrrolidone (PVP). Initial ratio of PVP/MWCNTs is 20. Consecutive ultrasonication (1 h., with ultrasonic probe) and centrifugation (1200 rcf for 30 min.) yielded stable suspensions as evident in zeta potential measurements and sedimentation tests (suspensions are stable for months). Zeta potential value of PVP modified MWCNTs IPA suspensions was found -35,9 mV (Huckel’s approximation). Carboxyl group functionalized MWCNTs IPA suspensions were also prepared by acid functionalization technique (3/1 H2SO4/HNO3 mixture). Filtration, ultrasonication and centrifugation result in stable COOH modified MWCNTs IPA suspensions as well (Zeta potential:-47,5 mV). Prior to electrophoretic deposition PVP MWCNTs IPA suspensions were mixed with MgCl2 IPA solutions at proper amounts (9.64mM MgCl2). Presence of magnesium ions enabled adhesion of MWCNTs although their concentration is high in terms of stability. Zeta potential of magnesium ion containing electrophoretic suspensions were found 19,7mV. Electrophoretic deposition processes were conducted under 50 V DC voltage for 10 min. and 20 min. with a electrode separation of 1.5 cm. UV-Vis spectroscopy analysis were conducted in two different ways to determine concentration of PVP and MWCNTs in suspensions and hence in coatings. For the determination of PVP concentration, a calibration curve of PVP was obtained by evaluating spectra of PVP IPA solutions. UV-Vis spectra of PVP MWCNTs IPA were obtained by measuring diluted suspensions. In addition, spectra of COOH MWCNTs IPA were obtained which are overlapping with that of PVP MWCNTs IPA at the visible and infrared region of the spectrum where only MWCNTs contribute to absorption. Finally, subtraction of MWCNTs contribution yields representing PVP spectra of suspensions and ultimately PVP concentrations were determined by using a calibration curve. MWCNTs concentration was determined by overlapping properly diluted suspensions of centrifuged and uncentrifuged (Initial concentration of MWCNTs is known in uncentrifuged suspension) suspension spectra. Concentration of materials in coating and coating thickness is estimated by measuring UV-Vis spectra of electrophoretic suspensions before and after 20 min. deposition. Then the loss of material in suspension during electrophoretic deposition was determined. PVP concentration in coating was calculated 0.18 g/L and MWCNTs concentration was calculated 0.02 g/L. Thereby, Quantity of PVP and MWCNTs in coating were estimated 0.0009 g and 0.0001 g, respectively (Volume of suspensions is known). Surface area of coating is measured 0.8 cm2. Densities of MWCNTs and PVP were acknowledged as 1.32 g/cm3 (theoretical density of stacks of 18 layer multi wall carbon nanotubes) and 1.25 g/cm3. Ultimately, thickness of the coating was calculated ~10 µm. SEM images of the coatings were also conducted to determine the accuracy of the estimated values. It turns out that coating thickness is around 20 µm in diameter in terms of SEM measurements. The difference in measured and calculated values may be due to various reasons. Firstly, porosity in coating is neglected in estimations. Secondly, there is a small amount of deposition at the back of deposition electrode which is neglected as well. Thirdly, SEM measurements were taken from the bottom of the deposit at the region where the thickness is the highest due to probable sedimentation during deposition.

Selective Electrochemical Detection of Ciprofloxacin with a Porous Nafion/Multiwalled Carbon Nanotube Composite Film Electrode.

This study focuses on the development of electrochemical sensors for the detection of Ciprofloxacin (CFX) in natural waters and wastewater effluents. The sensors are prepared by depositing a layer of multiwalled carbon nanotubes (MWCNTs) dispersed in a porous Nafion film on to a boron-doped diamond (BDD) electrode substrate. The porous-Nafion-MWCNT/BDD electrode enhanced detection of CFX due to selective adsorption, which was accomplished by a combination of electrostatic attraction at -SO3(-) sites in the porous Nafion film and the formation of charge assisted hydrogen bonding between CFX and -COOH MWCNT surface functional groups. By contrast, the bare BDD electrode did not show any activity for CFX oxidation. The sensors were selective for CFX detection in the presence of other antibiotics (i.e., amoxicillin) and other nontarget water constituents (i.e., Cl(-), Ca(2+), humic acid, sodium dodecylbenzenesulfonate, salicylic acid, 4-aminobenzoic acid, and 4-hydroxybenzoic acid). A limit of detection of 5 nM (S/N = 5.04 ± 0.26) in a 0.1 M KH2PO4 supporting electrolyte (pH = 4.5) was obtained using differential pulse voltammetry. The linear dynamic ranges with respect to CFX concentration were 0.005-0.05 μM and 0.05-10 μM, and the sensitivities were 41 ± 5.2 μA μM(-1) and 2.1 ± 0.22 μA μM(-1), respectively. Sensor fouling was observed at high concentrations of some organic compounds such as 1 mM 4-aminobenzoic acid and 4-hydroxybenzoic acid. However, a short cathodic treatment fully restores sensor response. The results indicate that these sensors have application in detecting CFX in natural waters and wastewater effluents.

Interlaminar Fracture Toughness of CFRP Laminates Incorporating Multi-Walled Carbon Nanotubes

Carbon fiber reinforced polymer (CFRP) laminates exhibit limited fracture toughness due to characteristic interlaminar fiber-matrix cracking and delamination. In this article, we demonstrate that the fracture toughness of CFRP laminates can be improved by the addition of multi-walled carbon nanotubes (MWCNTs). Experimental investigations and numerical modeling were performed to determine the effects of using MWCNTs in CFRP laminates. The CFRP specimens were produced using an epoxy nanocomposite matrix reinforced with carboxyl functionalized multi-walled carbon nanotubes (COOH–MWCNTs). Four MWCNTs contents of 0.0%, 0.5%, 1.0%, and 1.5% per weight of the epoxy resin/hardener mixture were examined. Double cantilever beam (DCB) tests were performed to determine the mode I interlaminar fracture toughness of the unidirectional CFRP composites. This composite material property was quantified using the critical energy release rate, GIC. The experimental results show a 25%, 20%, and 17% increase in the maximum interlaminar fracture toughness of the CFRP composites with the addition of 0.5, 1.0, and 1.5 wt% MWCNTs, respectively. Microstructural investigations using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) verify that chemical reactions took place between the COOH–MWCNTs and the epoxy resin, supporting the improvements experimentally observed in the interlaminar fracture toughness of the CFRP specimens containing MWCNTs. Finite element (FE) simulations show good agreement with the experimental results and confirm the significant effect of MWCNTs on the interlaminar fracture toughness of CFRP.

Preparation, characterization and properties of polycaprolactone diol-functionalized multi-walled carbon nanotube/thermoplastic polyurethane composite

Multi-walled carbon nanotubes (MWCNTs) were chemically functionalized to prepare thermoplastic polyurethane (PU) composites with enhanced properties. In order to achieve a high compatibility of functionalized MWCNTs with the PU matrix, polycaprolactone diol (PCL), as one of PU’s monomers, was selectively grafted on the surface of MWCNTs (MWCNT–PCL), while carboxylic acid groups functionalized MWCNTs (MWCNT–COOH) and raw MWCNTs served as control. Both MWCNT–COOH and MWCNT–PCL improved the dispersion of MWCNTs in the PU matrix and interfacial bonding between them at 1wt% loading fraction. The MWCNT–PCL/PU composite showed the greatest extent of improvement, where the tensile strength and modulus were 51.2% and 33.5% higher than those of pure PU respectively, without sacrificing the elongation at break. The considerable improvement in both mechanical properties and thermal stability of MWCNT–PCL/PU composite should result from the homogeneous dispersion of MWCNT–PCL in the PU matrix and strong interfacial bonding between them.

Surface modification of multiwall carbon nanotubes determines the pro-inflammatory outcome in macrophage

Carbon nanotubes (CNTs) are widely used in industry and biomedicine. While several studies have focused on biological matters, attempts to systematically elucidate the toxicity mechanisms of CNTs are limited. The aim of the present study was to evaluate and compare the cytotoxicity of raw multi-walled carbon nanotubes (MWCNTs) and MWCNTs functionalized with carboxylation (MWCNTs–COOH) or polyethylene glycol (MWCNTs–PEG) in murine macrophages. Our results show that only MWCNTs–COOH and raw MWCNTs alter the oxidative potential of macrophages by increasing reactive oxygen species and the expression of pro-inflammatory factors in both a concentration- and surface coating-dependent manner. The data suggest that compare with raw MWCNTs and MWCNTs–PEG, the MWCNTs–COOH produces a significant increase in ROS generation, interruption of ATP synthesis, and activation of the MAPK and NF-κB signaling pathways, which in turn upregulates IL-1β, IL-6, TNF-α, and iNOS to trigger cell death. These findings suggest that contributory cellar uptake caused by physicochemical factors rather than residual metal catalysts plays a role in ROS-mediated pro-inflammatory responses in vitro.