Hydrophobic Multiwalled Carbon Nanotubes Research Articles

Ni3S4 combined hydrophilic hydroxylated MWCNTs for high performance asymmetric supercapacitors

A composite material (Ni3S4-Q) of Ni3S4 combined with hydrophilic hydroxylated multi-walled carbon nanotubes (MWCNTs) was prepared by one-step method in the reactor. For comparison, hydrophilic MWCNTs were replaced by hydrophobic MWCNTs (Ni3S4-S), and pure Ni3S4 was synthesized without adding MWCNTs, so as to study the influence of the hydrophilicity and hydrophobicity of MWCNTs on the capacitive performance of Ni3S4. The contact Angle analysis shows that Ni3S4-Q has better hydrophilicity. The electrochemical cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy show that Ni3S4-Q has the highest specific capacitance and the lowest ion diffusion resistance. In addition, the asymmetric supercapacitor assembled by Ni3S4-Q and activated carbon has a maximum energy density of 51 Wh kg−1. This work strongly validated that hydrophilicity can improve the electrochemical properties of supercapacitors.

In Russian

The microviscosity of erythrocyte membranes is directly related to their integrity, the violation of which in the presence of foreign objects manifests itself in a sharp increase in the microviscosity index, which certainly indicates the degree of cytotoxic effect of objects in contact with cells of a living organism. Using the spin probe method, a comparative study was made of the effect of a number of carbon nanoparticles on the microviscosity of rat erythrocyte membranes. It has been found that the presence of oxidized graphene (OG) in suspension of red blood cells practically does not affect the microviscosity index of membranes. In the presence of carbon nanotubes (CNTs) of various structures during prolonged (24 h) incubation with erythrocytes, an increase in the microviscosity of erythrocyte membranes is 1.5–2 times. Oxidized multi-walled nanotubes exert the greatest effect. Hydrophobic multi-walled CNTs have a smaller effect, and single-walled nanotubes are characterized by a slight effect on the membranes. Incubation of erythrocytes with carbon nanochorns (CNCh) leads to a significant increase in the microviscosity of erythrocyte membranes by 60 % and higher; after 1 h of incubation, the polarity of the surface of the lipid layer of the membranes increases stepwise, apparently due to the destruction of the membrane and the ingress of water molecules there, as well as the disorder of phospholipids. The introduction of detonation nanodiamond (DND) nanoparticles into a suspension of erythrocytes at a concentration of 25 μg/ml produced no noticeable change in the membrane microviscosity index. An increase in the concentration of DND in suspension of red blood cells to 50 and 75 μg/ml led to a decrease in the microviscosity of erythrocyte membranes (increase in fluidity of the membranes) by 20 and 28 %, respectively. Thus, among carbon nanoparticles, nanotubes and nanochorns can exhibit cytotoxicity, which is mainly due to their structure, size, and shape.

Stable pickering emulsions using multi-walled carbon nanotubes of varying wettability

The influence of surface functional groups on multi-walled carbon nanotubes (MWNT) the stability and type of Pickering emulsions in water and oil systems is reported. The strong interaction between carbon nanotubes allows for the unique ability to tune emulsion type and droplet size while producing emulsions that are stable for over a month. This behavior stands in stark contrast to what is known for other Pickering emulsion stabilizers such as colloidal silica. Emulsion droplet size displays parabolic behavior, with amphiphilic MWNTs stabilizing the smallest emulsion droplets while larger droplets are stabilized with more hydrophobic or hydrophilic MWNTs. At equivalent volumes of oil and water, water-in-oil emulsions are stabilized by hydrophobic MWNTs, while hydrophilic MWNTs result in oil-in-water emulsions. Emulsion droplet size and type vary depending on the wettability of the MWNTs when changing the oil-to-water ratio. Mixing MWNTs of different wettability results in a non-linear emulsion droplet size trend and may possibly be due to the interaction between the MWNTs of different wettability. To our knowledge, no other Pickering emulsion stabilizer allows for this range of tuning of emulsion properties while sustaining high emulsion stability, even when changing the oil-to-water ratio to induce catastrophic emulsion inversion.

The Effect of Hydrophilic and Hydrophobic Multi-Wall Carbon Nanotubes on Methane Dissolution Rates in Water at Three Phase Equilibrium (V−Lw−H) Conditions

Presently, gas hydrates are being studied for their potential applications in technologies involving natural gas transportation, carbon dioxide sequestration, and component separation. In order to optimize their use, research has focused on finding hydrate-promoting agents and understanding how they work. One such promoter, multiwall carbon nanotubes (MWNTs), was found to enhance hydrate growth. The current study investigates the effects of adding plasma-functionalized hydrophilic MWNTs and as-produced hydrophobic MWNTs on the dissolution stage of methane hydrate formation. It was found that the addition of the hydrophilic MWNTs increased methane dissolution rates with an increase in MWNT loading. Furthermore, the hydrophobic MWNTs initially enhanced dissolution up until a concentration of 5 ppm, at which point the rates began to return to their nominal values. It was also found that the addition of either type of MWNT did not significantly affect the total number of moles of methane dissolved in the water.

Synthesis and characterization of functionalized carbon nanotubes with different wetting behaviors and their influence on the wetting properties of carbon nanotubes/polymethylmethacrylate coatings

Abstract The synthesis and characterization of hydrophobic functionalized multi-wall carbon nanotubes (MWCNTs) were investigated and their influence on the wetting properties of organic coatings and composites was studied. Functionalization was performed using oxidation, 1,3-dipolar cycloaddition, and silanization. Silanization was conducted using three hydrophobic silane precursors: 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, and triethoxyoctylsilane. Functionalization was directly confirmed and characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis, and scanning electron microscopy. The water contact angle of the functionalized MWCNTs was 40–142° for different surface functionalities and the functionalized MWCNTs were incorporated into an acidic solution of polymethylmethacrylate. The effect of surface functionality and the concentration of the functionalized MWCNTs on the wetting properties of these composites were studied by measuring the water contact angle. Under optimum conditions, composite surfaces with water contact angles greater than 110° were obtained. Atomic force microscopy was used to determine the topography of the surface and energy dispersion spectroscopy was used to determine the distribution of the functionalized MWCNTs in the composite film. It was shown that the hydrophobic functionalized MWCNTs migrated to the surface; this was more pronounced for the more hydrophobic MWCNTs.

Electrodeposition of copper on aligned multi-walled carbon nanotubes

In this work, the electrochemical deposition of copper on aligned multi-walled carbon nanotubes (MWCNTs) from an aqueous electrolyte is described. The addition of sodium dodecyl sulphate has been applied to enhance wettability of the hydrophobic MWCNT surface. The transfer of the MWCNT–copper composite film from nickel substrates, as applied for the chemical vapour deposition process for carbon nanotube synthesis, onto adhesive tapes is performed. Moreover, a sandwich layer consisting of copper top layers and copper incorporated MWCNT interlayer was produced. The structure of the resulting composite material of MWCNTs and copper was characterised by scanning electron microscopy. An electrochemical investigation of the MWCNTs on nickel foil and on conductive carbon ribbon by cyclic voltammetry is presented.

Electro-responsive transdermal drug delivery behavior of PVA/PAA/MWCNT nanofibers

The electro-responsive transdermal drug delivery system was prepared by electrospinning of poly(vinyl alcohol)/poly(acrylic acid)/multi-walled carbon nanotubes (MWCNTs) nanocomposites. The surface modification of MWCNTs was carried out by oxyfluorination to introduce the functional groups on the hydrophobic MWCNTs. The dispersion of MWCNTs and the compatibility with polymer matrices were improved by oxyfluorination. The MWCNT content and oxyfluorination condition played important roles in the swelling and drug release characteristics of nanofibers. The conductivity of nanofibers increased by increasing the content of MWCNTs and performing oxyfluorination with higher oxygen content. Uniform distribution of the oxyfluorinated MWCNTs in the nanofibers was crucial to the electro-responsive swelling and drug releasing behaviors of nanofibers.

Electrochemical Formation of Pt Nanoparticles on Multiwalled Carbon Nanotubes: Useful for Fabricating Electrodes for Use in Dye-Sensitized Solar Cells

In the present work, hydrophobic multiwalled carbon nanotubes (MWCNTs) were modified, by the substitution of poly(acrylic acid) (PAA) and inorganic acids (H2SO4 and HNO3), as hydrophilic MWCNTsPAA and MWCNTsAcid. The modified nanotubes were dispersed in an ethanol solution containing 3,4-ethylenedioxythiophene (EDOT). PtCl62− ions were reduced electrochemically to platinum (Pt) by electrons supplied by the polymerization of EDOT. The reduced platinum was deposited as Pt nanoparticles (nps) on the MWCNTs, to form MWCNTsPAA-PEDOT-Pt(nps) and MWCNTsAcid-PEDOT-Pt(nps). Electrostatic interactions between carboxyl groups on the MWCNTs and EDOT monomers allowed the Pt(nps) to be adsorbed onto the MWCNTs. The quantity of Pt(nps) associated with the MWCNTsPAA-PEDOT-Pt(nps) composite was greater than that with the MWCNTsAcid-PEDOT-Pt(nps) composite, due to the substitution of the carboxyl group in MWCNTsPAA. UV−visible spectroscopy was used to measure the reducing ability of EDOT. FTIR-ATR, TGA, ZETA potential anal...