Synthesis,characteristic, and flammability of modified carbon nanotube/poly(ethylene-<Emphasis Type="Italic">co</Emphasis>-vinyl acetate) nanocomposites containing phosphorus and silicon

A novel flame retardant containing phosphorus–silicon, spirocyclic pentaerythritol bisphosphorate disphosphorylchloride/9,10-dihydro-9-oxa-10-phosphaphanthrene-10-oxide/vinyl methyl dimethoxysilane (SPDV), has been used to modify multiwalled carbon nanotubes (MWNTs) and the m-MWNTs (MWNTs-g-SPDV) was obtained by the covalent grafting of SPDV onto the surfaces of MWNTs. And then the according poly(ethylene-co-vinyl acetate) nanocomposites were prepared via melt blending. Transmission electron microscopy (TEM) results showed that a core–shell nanostructure with MWNTs as the hard core and SPDV as the soft shell was formed, and the resultant m-MWNTs can achieve better dispersion than pristine MWNTs in EVM matrix. Cone calorimeter results showed that better flame retardancy was obtained for EVM/m-MWNTs nanocomposites. Mechanical measurements showed that the Young’s modulus increases due to the presence of MWNTs or m-MWNTs. The flammability and mechanical properties of the nanocomposites are strongly dependent on the dispersion state of nanotubes.     

Synthesis and electrocatalytic activity of multi-walled carbon nanotubes/Cu–Ag nanocomposites

Cu–Ag bimetallic nanoparticles with atomic ratio of 2.1:1 and diameter in the range of 15–30 nm were decorated on acid-treated multi-walled carbon nanotubes by a chemical reduction method, which was characterized by transmission electron microscope (TEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). The Cu–Ag/MWNTs nanocomposites were used to construct a modified electrode toward biosensing of H₂O₂ with a high sensitivity. The catalytic ability of MWNTs/Cu–Ag toward H₂O₂ was much better than that of MWNTs/Cu and MWNTs/Ag, which indicated that there is a cooperation effect between Cu and Ag.     

Photoinactivation of bacteria by using Fe-doped TiO<Subscript>2</Subscript>-MWCNTs nanocomposites

In this study, nanocomposites of Fe-doped TiO₂ with multi-walled carbon nanotubes (0.1– 0.5?wt. %) were prepared by using sol–gel method. The structural and morphological analysis were carried out with using X-ray diffraction pattern and transmission electron microscopy, which confirm the presence of pure anatase phase and particle sizes in the range 15–20?nm. X-ray photoelectron spectroscopy was used to determine the surface compositions of the nanocomposites. UV–vis diffuse reflectance spectra confirm redshift in the optical absorption edge of nanocomposites with increasing amount of multi-walled carbon nanotubes. Nanocomposites show photoinactivation against gram-positive Bacillus subtilis as well as gram-negative Pseudomonas aeruginosa. Fe-TiO₂-multi-walled carbon nanotubes (0.5?wt. %) nanocomposites show higher photoinactivation capability as compared with other nanocomposites. The photoluminescence study reveals that the Fe-TiO₂-multi-walled carbon nanotubes nanocomposites are capable to generate higher rate of reactive oxygen species species than that of other nanocomposites. Our experimental results demonstrated that the Fe-TiO₂-multi-walled carbon nanotubes nanocomposites act as efficient antibacterial agents against a wide range of microorganisms to prevent and control the persistence and spreading of bacterial infections.     

Fabrication of nanocomposites based on carbon nanotubes containing Pt nanoparticles and TiO<Subscript>2</Subscript>

Using conical multiwalled carbon nanotubes (CNTs), we have prepared Pt/CNT and Pt/TiO₂/CNT nanocomposites with an average platinum particle size of 3–5 nm, Pt/Ti molar ratio on the surface in the range 3.5–4, and C/Pt = 21–22. Titania was deposited onto the CNTs through titanium tetrachloride (TiCl₄) hydrolysis. Platinum particles were produced by reducing chloroplatinic acid (H₂PtCl₆) with sodium borohydride (NaBH₄) in the presence of CNTs. The composition and structure of the composites have been studied using X-ray photoelectron spectroscopy, electron microscopy, X-ray diffraction, and thermogravimetry. The materials have been tested as catalysts for hydrogen oxidation and oxygen reduction. The results demonstrate that the modification of Pt/CNT with titania enhances the catalytic activity of the material.     

Visible light photocatalytic properties of novel molybdenum treated carbon nanotube/titania composites

Two types of molybdenum–carbon nanotubes and molybdenum treated carbon nanotubes/titania composites were prepared using a sol–gel method. These composites were characterized comprehensively by the Brauer–Emett–Teller (BET) surface area, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis absorption spectroscopy. It was found that the photocatalytic degradation of a methylene blue solution could be attributed to the combined effects caused by the photo-degradation of titania, the electron assistance of carbon nanotube network, and the enhancement of molybdenum. The proposed redox mechanism of the photodegradation of methylene blue on Mo-CNT/TiO₂ composites is suggested.     

Synthesis and electrocatalytic activity of platinum nanoparticle/carbon nanotube composites

Pt/CNT nanocomposite materials with an average platinum particle size of 3–5 nm and platinum content of 13–28 wt % have been prepared by reducing chloroplatinic acid, H₂PtCl₆, in the presence of conical carbon nanotubes. The effect of synthesis conditions on the average platinum particle size, total platinum content, and surface composition of the nanocomposites has been studied using X-ray photoelectron spectroscopy, IR spectroscopy, electron microscopy, X-ray diffraction, and thermogravimetry. The materials have been tested as catalysts for hydrogen oxidation and oxygen reduction. Their performance has been assessed by cyclic and steady-state voltammetric techniques. The structure and composition effects on the electrocatalytic properties of the nanocomposites are discussed.     

Effect of heat treatment on structure and magnetic properties of FeCoNi/CNTs nanocomposites

Fe₄₆Co₃₅Ni₁₉/CNTs nanocomposites have been prepared by an easy two-step route including adsorption and heat treatment processes. We investigated the effect of heat treatment conditions on structure, morphology, nanoparticle sizes and magnetic properties of the Fe₄₆Co₃₅Ni₁₉ alloy nanoparticles attached on the carbon nanotubes by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-disperse X-ray spectroscopy (EDS) and vibrating sample magnetometer (VSM). When the reducing temperature changes from 300–450°C, a transition of the crystalline structure from bcc phase to fcc-bcc dual phase and an increase in particle size of Fe₄₆Co₃₅Ni₁₉ nanoparticles together with a local maximum at 350°C are observed. Meanwhile, the saturation magnetization (M _s) for Fe₄₆Co₃₅Ni₁₉ nanoparticles increases with the increase of reducing temperature and the coercivity (H _c) decreases rapidly with a local minimum at 350°C. When the reducing time (tr) changes from 2–5 h, bcc phase is predominant in the Fe₄₆Co₃₅Ni₁₉ alloy particles. Both the particle size and M _s have a maximum at tr = 3 h, and the H _c reaches a maximum at tr = 4 h.     

Hydroxylation of multi-walled carbon nanotubes reduces their cytotoxicity by limiting the activation of mitochondrial mediated apoptotic pathway

Hydroxylation of carbon nanotubes (CNTs) can enhance their dispersibility in water, and allows the capability to conjugate with other molecules for the expected applications. However, the cytotoxicity of hydroxylated CNTs has not been thoroughly investigated. Here, we compared the cytotoxicity of hydroxylated multi-walled carbon nanotubes (MWCNTs–OH) on a human cell line with that of pristine multi-walled carbon nanotubes (p-MWCNTs). We showed that while both MWCNTs–OH and p-MWCNTs induced apoptosis in a time- and dose-dependent manner, MWCNTs–OH triggered a significantly milder cytotoxic response than that of p-MWCNTs. We further showed that such attenuated response could be attributed to a reduced disruption of the mitochondrial membrane potential (MMP), leading to the attenuation of both cytochrome c (cyt-c) release and activation of caspases. These findings suggest that MWCNTs–OH, could be more biocompatible for in vivo applications than that of p-MWCNTs by limiting the activation of the mitochondrial mediated apoptotic pathway.     

Development of a modified electrode with amine-functionalized TiO2/multi-walled carbon nanotubes nanocomposite for electrochemical sensing of the atypical neuroleptic drug olanzapine

In this work, using of amine-functionalized TiO₂/multi-walled carbon nanotubes (NH₂-TiO₂-MWCNTs) nanocomposite for modification of glassy carbon electrode (GCE) was investigated. The nanocomposite was characterized by Fourier transformed infrared spectroscopy, transmission electron microscopy and scanning electron microscopy. The efficiency of modified electrode for electrocatalytic the oxidation of olanzapine was studied by cyclic voltammetry, square wave voltammetry and chronoamperometry. The electrochemical measurements were carried out in phosphate-buffered solution (PBS, pH 5.0). The NH₂-TiO₂-MWCNTs/GCE provided high surface area and more sensitive performance. The charge transfer coefficient (α) and the apparent charge transfer rate constant (k_s) were calculated to be equal to 0.42 and 0.173 s^? 1, respectively. The square wave voltammetry exhibited two linear dynamic ranges and a detection limit of 0.09 μM of olanzapine. In addition, the modified electrode was employed for the determination of olanzapine in pharmaceutical and human blood serum samples in order to illustrate the applicability of proposed method.     

Toughening and reinforcement of poly(vinylidene fluoride) nanocomposites with “bud-branched” nanotubes

Bud-branched nanotubes, fabricated by growing metal particles on the surface of multi-wall carbon nanotubes (MWCNTs), were used to prepare poly(vinylidene fluoride) (PVDF) based nanocomposites. The results of differential scanning calorimetry (DSC) showed that the introduction of the MWCNTs and bud-branched nanotubes both increased the crystallization temperature, while no significant variation of T_m (melting temperature), ΔH_c (melting enthalpy) and ΔH_m (crystallization enthalpy) occurred. The results of wide angle X-ray diffraction (WAXD) tests showed that α-phase was the dominated phase for both pure PVDF and its nanocomposites, indicating the addition of the MWCNTs and bud-branched nanotubes did not alter the crystal structures. Dynamic mechanical analysis (DMA) tests showed that bud-branched nanotubes were much more efficient in increasing storage modulus than the smooth MWCNTs. In addition, no significant variation of the T_g (glass transition temperature) was observed with the addition of MWCNTs and bud-branched nanotubes. Tensile tests showed that the introduction of MWCNTs and bud-branched nanotubes increased the modulus. However, a dramatic decrease in the fracture toughness was observed for PVDF/MWCNTs nanocomposites. For PVDF/bud-branched nanotubes nanocomposites, a significant improvement in the fracture toughness was observed compared with PVDF/MWCNTs nanocomposites.     

Controllable synthesis and magnetic properties of Fe–Co alloy nanoparticles attached on carbon nanotubes

Fe–Co alloy nanoparticles with different size were attached on the carbon nanotubes through adjusting the ratio of the metal to carbon in the mixed solution of nitrate with Fe:Co = 1:1 (molar ratio) via wet chemistry. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectrometry (EDX) indicated that the Fe–Co alloy nanoparticles attached on the surface of carbon nanotubes has body-centered cubic (bcc) structure, with sizes in the range of 13–25 nm and in the shape of spheroids. Magnetization measurements indicated that both the coercivities and the saturation magnetizations altered with size changes of the Fe–Co alloy nanoparticles. The saturation magnetization decreases with decreasing the Fe–Co alloy nanoparticles’ sizes. A decrease in coercivity with increasing Fe–Co size together with a local maximum coercivity at size of ca. 15 nm is visible. A linear relationship between the inverse particle diameter and the coercivity was found for larger particles. These demonstrated that the chemical method here is promising for fabricating Fe–Co alloy nanoparticles coated on carbon nanotubes for magnetic storage applications.     

Photochemical modification of single-walled carbon nanotubes using HPHMP photoinitiator for enhanced organic solvent dispersion

Photochemical modification of single-walled carbon nanotubes (SWCNTs) was carried out by covalent attachment of 2-propanol-2-yl radicals on the surface of SWCNTs, which were engendered by the photolysis of 1-[4-(2-Hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (HPHMP) under ultraviolet (UV) light. Pristine single-walled carbon nanotubes (p-SWCNTs) were dispersed in acetone along with HPHMP photoinitiator. After that, the mixture was irradiated by UV light to generate the free radicals which were introduced onto the surface of SWCNTs. The modification of SWCNTs was supported by UV/visible spectroscopy, Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, thermal gravimetric analysis–mass spectrometry (TGA–MS), and transmission electron microscopy (TEM). UV/visible results revealed the loss of van Hove singularities due to covalent modification. The modification was further verified by FT-IR showing the signals at 3421 and 1100 cm⁻¹ due to stretching and bending of O–H group, respectively. Moreover, other peaks at 2927 and 2858 cm⁻¹ indicated the asymmetric and symmetric stretching modes of aliphatic C–H bond, respectively. Raman spectra illustrated that the intensity ratio of the tangential mode to the disorder mode (I _G/I _D), for modified SWCNTs (F-SWCNTs), decreased nearly four times than p-SWCNTs. TGA–MS also evidenced the signal corresponding to m/z 59 at 400 °C indicating the presence of 2-propanol-2-yl groups. TEM and dispersibility data demonstrated that the sidewall modification detached the bundled structure, enhanced the dispersion in common organic solvents and retained the original size of SWCNTs without hefty modification, which could cut or damage the nanotubes.     

Synthesis and photocatalytic behaviors of Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>–CNT/TiO<Subscript>2</Subscript> composite materials under visible light

Cr₂O₃–CNT/TiO₂ composites derived from chromium acetylacetonate, multi-walled carbon nanotubes (MWCNT) and titanium n-butoxide (TNB) were prepared, and the photocatalytic activity of the Cr₂O₃–CNT and CNT/TiO₂ composites was examined. The Cr₂O₃–CNT/TiO₂ composites were characterized by BET surface area measurement, X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray analysis. The photocatalytic activity was determined from the decomposition of methylene blue (MB) under visible light irradiation. Methylene blue was photodegraded successfully in the presence of the Cr₂O₃–CNT/TiO₂ composite under visible light irradiation.     

Synthesis, characterization, and evaluation of lubrication properties of composites of ordered mesoporous carbons and luminescent CePO4:Tb nanocrystals

Having new potential applications in forging processes in mind, composites of an ordered mesoporous carbon and luminescent metal phosphate nanocrystals were synthesized for the first time. Three kinds of CMK-3/CePO₄:Tb nanocomposites were prepared by treating a mesoporous CMK-3 host with different lanthanide phosphate precursor solutions. Characterization of the obtained nanocomposites by small-angle X-ray scattering, wide-angle X-ray diffraction, transmission electron microscopy, thermogravimetry, and nitrogen physisorption analysis showed that in two cases, the nanocrystals (ca. 2–3 nm in size) were located inside the mesopores, whereas in the third case the nanocystals (ca. 6 nm in size) merely adhered to the outer surfaces of the carbon particles. The CMK-3 and the two nanocomposites had ordered hexagonal structures (space group p6mm); all the materials possessed amorphous carbon walls. After combustion of the nanocomposites, the residues upon excitation with UV light exhibited the typical green luminescence of Tb³⁺. A preliminary evaluation of the lubrication properties of the CMK-3 and one nanocomposite material was performed. The friction factors determined by means of ring upsetting tests revealed that the carbon materials were able to lower frictional forces although they were 3–4 times less efficient than a commercial graphite-based reference lubricant.     

Microwave assisted fast fabrication of Fe3O4-MWCNTs nanocomposites and their application as MRI contrast agents

Uniform Fe₃O₄ nanoparticles with diameters of 3-5 nm are successfully decorated onto the external walls of multiwall carbon nanotubes (MWCNTs) by in situ high-temperature decomposition of Fe(acac)₃ in polyol solution under the irradiation of microwave. With this method, reaction time of forming Fe₃O₄-MWCNTs nanocomposites has been significantly shortened to 15 min. The resulting Fe₃O₄-MWCNTs nanocomposites show superparamagnetic property at room temperature and can be remained as stable aqueous dispersion for 2 months. Longitudinal relaxivity (r₁) and transverse relaxivity (r₂) of the magnetic MWCNTs are 8.34 Fe mM⁻¹ S⁻¹ and 146 Fe mM⁻¹ S⁻¹ respectively. The much higher r₂ value and the obvious change in the gray scale of MR images confer the Fe₃O₄-MWCNTs nanocomposites as potential candidates for T₂-weighted MRI contrast agents.     

Temperature dependence of electrical conductivity in double-wall and multi-wall carbon nanotube/polyester nanocomposites

The aim of this study is to investigate temperature dependence of electrical conductivity of carbon nanotube (CNT)/polyester nanocomposites from room temperature to 77 K using four-point probe test method. To produce nanocomposites, various types and amounts of CNTs (0.1, 0.3 and 0.5 wt.%) were dispersed via 3-roll mill technique within a specially formulized resin blend of thermoset polyesters. CNTs used in the study include multi walled carbon nanotubes (MWCNT) and double-walled carbon nanotubes (DWCNT) with and without amine functional groups (–NH₂). It was observed that the incorporation of carbon nanotubes into resin blend yields electrically percolating networks and electrical conductivity of the resulting nanocomposites increases with increasing amount of nanotubes. However, nanocomposites containing amino functionalized carbon nanotubes exhibit relatively lower electrical conductivity compared to those with non-functionalized carbon nanotubes. To get better interpretation of the mechanism leading to conductive network via CNTs with and without amine functional groups, the experimental results were fitted to fluctuation-induced tunneling through the barriers between the metallic regions model. It was found that the results are in good agreement with prediction of proposed model.     

Electrical properties of electrodeposited polyaniline nanotubes

The electrical properties of polyaniline nanotubes-aluminum like Schottky diode are described. Polyaniline nanotubes (PANI) were deposited on aluminum thin films using the polarographic technique. The nanotubes were characterized by scanning electron microscopy (SEM) and UV-Vis absorption spectra. The electrical properties of the heterojunction PANI-Al were examined. The current density–voltage (J × V) profile has shown a behavior typical of Schottky diode, with ideality factor (n) of 6.76 and ϕ _b of 0.70 eV. Impedance spectroscopy data apparently shows that the resistance dominated the AC behavior of the PANI-Al system. The equivalent circuit is composed from a resistor in series with a parallel resistor–capacitor circuit. The results indicate that polyaniline nanotubes may be interesting to the development of electro-optical devices with 2D structure.     

Photocatalytic activity of polypyrrole/TiO<Subscript>2</Subscript> nanocomposites under visible and UV light

A series of polypyrrole (PPy)/titanium dioxide (TiO₂) nanocomposites were prepared in different polymerization conditions by ‘in situ’ chemical oxidative polymerization. The nanocomposites were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy spectra (XPS), and UV–Vis diffuse reflectance spectra. The photocatalytic degradation of methyl orange (MO) was chosen as a model reaction to evaluate the photocatalytic activities of TiO₂/PPy catalysts. The results show that a strong interaction exists at the interface between TiO₂ and PPy, the deposition of PPy on TiO₂ nanoparticles can alleviate their agglomeration, PPy/TiO₂ nanocomposites show stronger absorbance than neat TiO₂ under the whole range of visible light. The obtained PPy/TiO₂ nanocomposites exhibit significantly higher photocatalytic activity than the neat TiO₂ on the degradation of MO aqueous solution under visible and UV light illumination. The reasons for improving the photocatalytic activity were also discussed.     

Characteristics and plasma parameters of a short-wavelength low-pressure discharge lamp

We have studied the working optical characteristics and electron kinetic coefficients of a short-wavelength, electric discharge exciplex-halogen UV-VUV lamp employing a mixture of argon and chlorine with a total pressure of P = 0.5–10 kPa. The lamp operates on a system of broadened electron-vibrational bands of ArCl (175 nm) and chlorine (200, 258 nm) molecules, which overlap to form a continuum in the spectral range of 160–260 nm. It is established that the optimum mixtures are those with p(Ar) − p(Cl₂) = (2–4)−(0.15–0.30) kPa. The average output power of the short-wavelength radiation is 1–2 W at an efficiency of ∼5%. The electron energy distribution functions (EDFs) and the discharge plasma parameters have been calculated by solving the Boltzmann equation for a gas mixture with the experimentally determined optimum composition in the range of E/P values from 1 to 200 V/(cm Torr), where E is the electric field strength and P is the total gas pressure. Using the obtained EDFs, the electron transport characteristics, specific discharge power losses for the main elementary processes, and rate constants of electron processes are determined.     

Temperature optimisation of CNT synthesis by spray pyrolysis of alpha-pinene as the carbon source

Multi-wall carbon nanotubes (MWCNTs) were prepared by spray-pyrolysis of a botanical hydrocarbon, alpha-pinene and ferrocene as the catalyst at 700–1000°C. The MWCNTs were analysed by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and X-ray diffraction. The microscopy studies show the formation of carbon nanotubes with diameters between 20 and 30 nm and length greater than 100 µm. Raman spectroscopy revealed that the alpha-pinene-grown carbon nanotubes were graphitised showing both the D and G bands at 1330 and 1590 cm^?1, respectively, and that the corresponding intensity band ratio (I _D/I _G) varied with respect to temperature formation.