Synthesis and enhanced photocatalytic activity of tin oxide nanoparticles coated on multi-walled carbon nanotube

A nanocomposite of SnO₂ nanoparticles coated on multi-walled carbon nanotube (MWNT@SnO₂) was synthesized and characterized by thermogravimetric analysis, X-ray diffraction, transmission electron microscopy, nitrogen physisorption measurements, photoluminescence. The results show that the SnO₂ nanoparticles with a narrow size of 4 nm are uniformly deposited on MWNT. The photocatalytic activity of the nanocomposite was studied using methyl orange as a model organic pollutant. MWNT@SnO₂ exhibits much higher photocatalytic activity than that of commercial TiO₂ (P-25). The promotion is mainly contributed from electron transfer between SnO₂ and MWNT.     

Poly(vinylidene fluoride)-assisted melt-blending of multi-walled carbon nanotube/poly(methyl methacrylate) composites

Multi-walled carbon nanotubes (MWNTs) were sonicated in the dimethylformamide solution of poly(vinylidene fluoride) (PVDF). The PVDF-covered MWNTs were then melt-blended with poly(methyl methacrylate) (PMMA). The dynamic mechanical behavior of various composites was studied. The presence of a small amount of PVDF leads to a significant improvement in the storage moduli of the MWNT/PMMA composites at low temperatures. The storage modulus of a PVDF/MWNT/PMMA composite containing 0.5 wt.% PVDF is almost twice as that of a MWNT/PMMA composite at 50°C. However, a further increase in the PVDF content leads to a reduction of the storage modulus. The beneficial effect of PVDF diminishes at higher temperatures.     

Preparation of Pt-Ru-Ni ternary nanoparticles by microemulsion and electrocatalytic activity for methanol oxidation

Ternary platinum-ruthenium-nickel nanoparticles are prepared by water-in-oil reverse microemulsions of water/Triton X-100/propanol-2/cyclohexane. Nanoparticles formed in the microemulsions are characterized by transmission electron microscopy (TEM), electron diffraction (ED), X-ray diffractometry (XRD), energy dispersive X-ray analysis (EDX). These resulting materials showed a homogenous alloy structure, the mono-dispersion and an average diameter of 2.6 ± 0.3 nm with a narrow particle size distribution. The composition and particle size of ternary Pt-Ru-Ni nanoparticles can be controlled by adjusting the initial metal salt solution and preparation conditions. Pt-Ru-Ni ternary metallic nanoparticles showed an enhanced catalytic activity towards methanol oxidation compared to Pt-Ru bimetallic nanoparticles.     

The poly(urethane-ionic liquid)/multi-walled carbon nanotubes composites

In the paper, a novel kind of imidazolium based poly(urethane-ionic liquid)/multi-walled carbon nanotubes (PUIL/MWCNT) composites was facilely prepared by uncovalent ways. The imidazolium based ionic liquid (IL) greatly improved the dispersion of pristine MWCNTs in PUIL by the π-cation interaction formed between the imidazolium cation and the π-electron of MWCNTs. The PUIL/MWCNT composites showed obviously increased modulus, glass transition temperature and tensile strength in comparison with PU/MWCNT composites. The thermal and mechanical properties of the PUIL/MWCNT composites presented significant increase with low load of the MWCNTs. It indicated the interactions between PUIL and MWCNTs played an important role to enhance the performances of the composites.     

High-performance carbon nanotube-implanted mesoporous carbon spheres for supercapacitors with low series resistance

Carbon nanotube-implanted mesoporous carbon spheres were prepared by an easy polymerization-induced colloid aggregation method using gelatin as a soft template. Scanning electron microscopy, transmission electron microscopy and nitrogen adsorption–desorption measurements reveal that the materials are mesoporous carbon spheres, with a diameter of ∼0.5–1.0 μm, a specific surface area of 284 m²/g and average pore size of 3.9 nm. Using the carbon nanotube-implanted mesoporous carbon spheres as electrode material for supercapacitors in an aqueous electrolyte solution, a low equivalent series resistance of 0.83 Ω cm² and a maximum specific capacitance of 189 F/g with a measured power density of 8.7 kW/kg at energy density of 6.6 Wh/kg are obtained.     

Exfoliated poly(methyl methacrylate)/MgFe-layered double hydroxide nanocomposites with small inorganic loading and enhanced properties

The novel exfoliated polymer nanocomposites (PMMA/MgFe(DS)-LDH) were synthesized by in situ polymerization based on poly(methyl methacrylate) (PMMA) and dodecyl sulfate-intercalated MgFe-layered double hydroxide (MgFe(DS)-LDH). The participation of Fe³⁺ ion is found to play an important role in the improvement of thermal stability of nanocomposites with small inorganic loading and well-dispersed inorganic components. The thermal degradation mechanism was discussed.     

Adsorption and electropolymerization of toluidine blue on the nanostructured octakis(hydridodimethylsiloxy)octasilsesquioxane surface

Toluidine blue O (TBO) was adsorbed on the octakis(hydridodimethylsiloxy)octasilsesquioxane (Q₈M₈^H) surface. The characterization of the precursor (Q₈M₈^H) and resulting materials obtained by the reaction of Q₈M₈^H and toluidine blue (CTBO) were defined using Fourier transform infrared spectra, nuclear magnetic resonance solid-state ¹³C and Si²⁹ magic angle spinning. The electrochemical polymerization in a glassy carbon electrode was verified by means of a film silsesquioxane formation (FCTBO) using cyclic voltammetry in a potential range of −0.5 to 1.3 V (vs. saturated calomel electrode (SCE)) in a Britton Robinson (B-R) buffer solution (pH 2.0). The cyclic voltammogram of the film exhibits two redox couples with a formal potential of −0.15 and −0.02 V (B-R buffer pH 5). The formal potential shifts linearly in the cathodic direction by increasing the pH solution with a slope of 71 and 57 mV per unit for the first and second couple, respectively. The film was electrochemically very stable.     

Processing and mechanical properties of carbon nanotube-alumina hybrid reinforced high density polyethylene composites

Carbon nanotube-alumina hybrid reinforced high density polyethylene (HDPE) matrix composites were prepared by melt processing technique. Microstructure studies verified that the nanotubes consisting of well-crystallized graphite formed a network structure with Al₂O₃ in the hybrid, which was homogeneously dispersed in the HDPE matrix composites. Mechanical measurements revealed that 5% addition of nanotube-alumina hybrid results in 100.8% and 65.7% simultaneous increases in Young's modulus and tensile strength, respectively. Fracture surface showed homogenous dispersion of nanotubes and Al₂O₃ in the HDPE matrix and presence of interlocking like phenomena between hybrid and HDPE matrix, which might contribute to the effective reinforcement of the HDPE composites.     

Effects of surface-functionalized multi-walled carbon nanotubes on the properties of poly(dimethyl siloxane) nanocomposites

The effects of surface-functionalized multi-walled carbon nanotubes (MWNTs) on the properties of poly(dimethyl siloxane) (PDMS) nanocomposites are investigated in the present study. The surface functionalization of MWNTs is carried out by diphenyl-carbinol functionalization followed by reaction with multifunctional silane, 3-aminopropyltriethoxisilane. Fourier transform infrared spectroscopy (FT-IR) and energy dispersion spectroscopy (EDS) analysis are used to confirm the presence of diphenyl-carbinol and silane on the surface of the MWNTs. The effects of the MWNTs’ surface treatment on the thermal and electrical properties of poly(dimethyl siloxane)-based (PDMS) nanocomposites are also studied. The results show that the grafting of silane molecules onto diphenyl-carbinol-functionalized MWNTs (SD-MWNTs) improves the dispersion of MWNTs in PDMS; this subsequently enhances the thermal conductivity and dynamic mechanical properties as compared to those containing unmodified (U-MWNTs) and diphenyl-carbinol-functionalized MWNTs (D-MWNTs). The electrical conductivity of the nanocomposites is shown to decrease due to the wrapping of MWNTs with non-electrical-conducting organic materials.     

Synthesis of Ru/multiwalled carbon nanotubes by microemulsion for electrochemical supercapacitor

An efficient way to decorate multiwalled carbon nanotubes with Ru had been developed. In this method, Ru nanoparticles were prepared by water-in-oil reverse microemulsion, and the produced Ru anchored on MWCNTs. Transmission electron microscopy (TEM) result showed that RuO₂ nanoparticles had the uniform size distribution after electrochemical oxidation. Energy dispersive X-rays (EDX) spectra elucidated the presence of ruthenium oxide in the as-prepared composites after electrochemical oxidation. Cyclic voltammetry result demonstrated that a specific capacitance of deposited ruthenium oxide electrode was significantly greater than that of the pristine MWCNTs electrode in the same medium.     

Synthesis of polycrystalline SnO2 nanotubes on carbon nanotube template for anode material of lithium-ion battery

Polycrystalline tin oxide nanotubes have been prepared by a layer-by-layer technique on carbon nanotubes template. Firstly, the surface of carbon nanotubes was modified by polyelectrolyte. Then, a uniform layer of tin oxide nanoparticles was formed on the positive charged surface of carbon nanotubes via a redox process. At last, the polycrystalline tin oxide nanotubes were synthesized after calcination at 650 °C in air for 3 h. The as-synthesized polycrystalline nanotubes with large surface area exhibit finer lithium storage capacity and cycling performance, which shows the potentially interesting application in lithium-ion battery.     

Synthesis of polyoxometalates-functionalized carbon nanotubes composites and relevant electrochemical properties study

Carbon nanotubes (CNTs)-based polyoxometalates (POMs)-functionalized nanocomposites were synthesized by simply functionalizing CNTs with Keggin and Dawson-type POMs. The positively charged polyelectrolyte poly (diallyldimethylammonium chloride) (PDDA) was introduced to assemble negatively charged POMs and CNTs. The composition, structure and morphology were investigated by UV-visible (UV-vis), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Cyclic voltammetry (CV) was employed to investigate the electrochemical properties of the resulting nanocomposites. The cyclic voltammograms indicate that the electrochemical properties of POMs are fully maintained. Functionalizing CNTs with POMs not only retains the unique properties of nanotubes, but also endows CNTs with the reversible redox activity of POMs.     

Synthesis of PbS/poly (vinyl-pyrrolidone) nanocomposite

A simple solution growth method for synthesis of nanocomposite of PbS nanoparticles in poly(vinyl-pyrrolidone) (PVP) polymer is described. The nanocomposite is prepared from methanolic solution of lead acetate (PbAc), thiourea (TU) and PVP at room temperature (∼27 °C). Optical absorption spectrum of PbS/PVP nanocomposite solution shows strong absorption from 300 to 650 nm with significant bands at 400 and 590 nm which is characteristic of nanoscale PbS. Spin-coated nanocomposite films on glass have an absorption edge at ∼650 nm with band gap of 2.55 eV. Fourier transform infrared (FTIR) spectroscopy of PbS/PVP nanocomposite and PVP shows strong chemical bond between PbS nanoparticles and host PVP polymer. The transmission electron microscope (TEM) images reveal that 5-10 nm PbS particles are evenly embedded in PVP polymer. The formation of PbS is confirmed by selective area electron diffraction (SAED) of a typical nanoparticle.     

Influence of multi-walled carbon nanotubes on electrochemical performance of transparent graphene electrodes

In this work, carbon-carbon nanocomposites as transparent electrodes were prepared by a chemical reduction of graphite oxide (GO) and multi-walled carbon nanotubes (MWNTs). The electric, optical, and electrochemical properties of graphene-MWNT nanocomposites (G-MCs) were investigated as a function of the MWNT content. It was found that chemically bonded G-MCs were successfully formed with a reduction of the functional groups of the GO and acid-treated MWNTs, resulting in the conjugation of 1D MWNTs onto a 2D graphene surface. The electrical conductivity of the graphene was significantly enhanced by introducing the MWNTs. In addition, the G-MCs showed improved current density and high efficiency compared with graphene alone. This indicated that the improved electrochemical performance of the G-MCs can be attributed to the increase in the activity and electrical conductivity enhanced by π-π interaction between graphene and MWNTs.     

Nanostructured TiC-TiB2 composites obtained by adding carbon nanotubes into the self-propagating high-temperature synthesis process

The synthesis of nanostructured TiC-TiB₂ by self-propagating high-temperature synthesis (SHS) has been investigated by using carbon nanotubes as precursor materials in partial substitution of graphite according to the following reaction: 6Ti + B₄C + (3−x)C + x CNT → 4TiC + 2TiB₂.Different amounts of CNTs addition have been studied in order to achieve structural refinement of the SHS products. The CNT molar content was varied in order to define the optimal composition, which allows to obtain nanostructured TiC-TiB₂ powders morphologically homogenous.The optimized composition has been chosen for the further densification step. The Pressure Assisted Fast Electric Sintering (PAFES) technique gave bulk composites with ultrafine grained microstructure. The mechanical characterization showed very high hardness and good fracture toughness values if compared to literature data.     

The formation of magnetite nanoparticles on the sidewalls of multi-walled carbon nanotubes

Linear polyethyleneimine (PEI) was used as a non-covalent functionalizing agent to modify multi-walled carbon nanotubes (MWCNTs). Fe₃O₄ nanoparticles were then formed along the sidewalls of the as-modified MWCNTs through a simple solvothermal method. X-ray diffraction, Fourier transform infrared spectrometry, transmission electron microscopy, and vibrating sample magnetometry were used to characterize the MWCNT/Fe₃O₄ nanocomposites. Results indicated that Fe₃O₄ nanoparticles with diameters ranging from 50 to 200 nm were attached to the surface of the MWCNTs by electrostatic interaction. PEI was found to improve the electrical conductivity of the MWCNT/Fe₃O₄ nanocomposites. The magnetic saturation value of these magnetic nanocomposites was 61.8 emu g⁻¹. These magnetic MWCNT/Fe₃O₄ nanocomposites are expected to have wide applications in bionanoscience and technology.     

High capacity and good cycling stability of multi-walled carbon nanotube/SnO2 core-shell structures as anode materials of lithium-ion batteries

The multi-walled carbon nanotube/SnO₂ core-shell structures were fabricated by a wet chemical route. The electrochemical performance of the core-shell structures as anode materials of lithium-ion batteries was investigated. The initial discharge capacity and reversible capacity are up to 1472.7 and 1020.5 mAh g⁻¹, respectively. Moreover, the reversible capacity still remains above 720 mAh g⁻¹ over 35 cycles, and the capacity fading is only 0.8% per cycle. Such high capacities and good cyclability are attributed to SnO₂ network structures, excellent mechanical property and good electrical conductivity of the multi-walled carbon nanotubes.     

Effect of multi-walled carbon nanotubes on the crystallization and hydrolytic degradation of biodegradable poly(l-lactide)

Biodegradable poly(l-lactide) (PLLA)/carboxyl-functionalized multi-walled carbon nanotubes (f-MWNTs) nanocomposites were prepared via solution blending. Scanning electron microscopy observations reveal a fine dispersion of f-MWNTs in the PLLA matrix. The presence of f-MWNTs enhances the crystallization of PLLA in the nanocomposites compared with that of neat PLLA; moreover, the overall crystallization rate of PLLA increases with increasing the f-MWNTs content in the PLLA matrix. The incorporation of f-MWNTs improves the storage modulus of the PLLA/f-MWNTs nanocomposites, with this effect being more pronounced at lower f-MWNTs content. The exciting aspect of this research is the enhanced hydrolytic degradation of PLLA after nanocomposites preparation with f-MWNTs, which may be of great interest for its wide practical application.     

Photochemical fabrication of size-controllable gold nanoparticles on chitosan and their application on catalytic decomposition of acetaldehyde

In this work, we report a new pathway to prepare size-controllable gold nanoparticles (NPs) on chitosan (Ch) in aqueous solutions for improving catalytic decomposition of acetaldehyde by pure gold NPs at room temperature. First, Au substrates were cycled in deoxygenated aqueous solutions containing 0.1N NaCl and 1 g/L Ch from −0.28 to +1.22 V vs Ag/AgCl at 500 mV/s for 200 scans. Then the solutions were irradiated with UV lights of different wavelengths to prepare size-controllable Au NPs on Ch. Experimental results indicate that the particle sizes of prepared NPs are increased when UV lights with longer wavelengths were employed. The particle sizes of resulted Au NPs can be controlled from 10 to 50 nm. Moreover, the decomposition of acetaldehydes in wines can be significantly enhanced by ca. 190% of magnitude due to the contribution of the adsorption of Au NPs on Ch.     

Nano-sized Li-Fe composite oxide prepared by a self-catalytic reverse atom transfer radical polymerization approach as an anode material for lithium-ion batteries

A novel Self-catalytic Reverse Atom Transfer Radical Polymerization (RATRP) approach that can provide the radical initiator and the catalyst by the system itself is used to synthesize a nano-sized Li-Fe composite oxide powder in large scale. Its crystalline structure and morphology have been characterized by X-ray diffraction and scanning electron microscopy. The results reveal that the composite is composed of nano-sized LiFeO₂ and Fe₃O₄. Its electrochemical properties are evaluated by charge/discharge measurements. The results show that the Li-Fe composite oxide is an excellent anode material for lithium-ion batteries with good cycling performance (1249 mAh g⁻¹ at 100th cycle) and outstanding rate capability (967 mAh g⁻¹ at 5 C). Such a self-catalytic RATRP approach provides a way to synthesize nano-sized iron oxide-based anode materials industrially with preferable electrochemical performance and can also be applied in other polymer-related area.