Multi-walled Carbon Nanotube Paper Research Articles

Performance-improved Li–O2 battery with Ru nanoparticles supported on binder-free multi-walled carbon nanotube paper as cathode

Ru nanoparticles supported on a multi-walled carbon nanotube paper as a cathode in a Li–O2 battery can significantly reduce the charge overpotentials, and present a large discharge–charge capacity and stable cycles.

Improving mechanical and electrical properties of oriented polymer-free multi-walled carbon nanotube paper by spraying while winding

In this study, a new method is introduced for fabricating carbon nanotube (CNT) paper, in which the solvent is sprayed on the CNT sheet while it is wound on a rotating mandrel. As the solvent evaporated, the capillary force pulls CNT closer together, resulting in a CNT paper with a high degree of alignment and a high packing density. Three batches of multi-walled CNTs with different wall thicknesses, tube diameters and lengths are utilized for synthesizing highly oriented CNT papers. It is found that CNTs with smallest diameter of 8nm form strongest CNT paper with a tensile strength of 563MPa and a tensile modulus of 15GPa, while that made with CNTs of 10nm diameter shows the highest electrical conductivity of 5.5×104S/m.

X-RAY PHOTOELECTRON SPECTROSCOPY AND SCANNING ELECTROCHEMICAL MICROSCOPY STUDIES OF BRANCHED MULTIWALLED CARBON NANOTUBE PAPER MODIFIED BY ELECTROCHEMICAL GRAFTING AND CLICK CHEMISTRY

Modification of nanomaterials through electrochemical grafting is a useful approach to introduce linking groups on to the surface of these structures. This work shows the possibility of applying electrochemical grafting to branched multiwalled carbon nanotube paper with an electrical resistance of 0.1 ohm-cm, and subsequent reaction of the grafted 4-azidobenzenediazonium with ethynylferrocene through the Sharpless click chemistry reaction. A comparison is made between this paper electrode and adsorbed single-walled carbon nanotubes on a glassy carbon electrode, with electrochemistry, X-ray photoelectron spectroscopy and scanning electrochemical microscopy used for characterization.

Electrochemical properties of free-standing Sn/SnO2/multi-walled carbon nano tube anode papers for Li-ion batteries

Free-standing multiwalled carbon nano tube papers (buckypapers) were prepared by vacuum filtration from functionalized multi walled carbon nano tubes (MWCNTs) with controlling porosity. Double phase matrix Sn/SnO2/MWCNT nanocomposites were obtained in two steps, including thermal evaporation of metallic tin (Sn) on the MWCNT papers and RF plasma oxidation. The ratio between metallic tin (Sn) and tin oxide (SnO2) was controlled with plasma oxidation time. It was determined that the evaporated pure tin nano crystals were mechanically penetrated into pores of buckypapers to form functionally gradient nanocomposites. Sn/SnO2 coated on MWCNT buckypapers were used as working electrodes in assembled as coin-type (CR2016) test cells. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to determine the structure and morphology of the obtained nanocomposites. In addition, the discharge/charge test, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were carried out to characterize the electrochemical properties of these composites as anode materials for Li-ion batteries.

Multi-walled carbon nanotube papers as binder-free cathodes for large capacity and reversible non-aqueous Li–O2 batteries

Multi-walled carbon nanotubes (MWCNTs) were interpenetrated together to form a 3-dimensional porous structure, multi-walled carbon nanotube paper (WCNTP), by a floating catalyst method. The as-synthesized MWCNTP was employed as an air cathode for non-aqueous Li–O2 batteries without the addition of any binder or conductive additives. A huge specific capacity of 34 600 mA h g−1 could be obtained at a current density of 500 mA g−1. 50 cycles of continuous discharge and charge have been achieved with no capacity loss at 250 mA g−1, with a cut-off capacity of 1000 mA h g−1. The reversible formation and decomposition of the discharge product Li2O2 was clearly revealed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). These results suggest the great potential of the binder-free MWCNTPs as air cathodes for Li–O2 batteries with high energy density.

Biofuel Cell Anodes Integrating NAD+-Dependent Enzymes and Multiwalled Carbon Nanotube Papers

This research aims to overcome kinetics, ohmic and mass transport limitations by improving the nanoarchitectured design of the catalytic layer and the mass transport system in order to improve the current output and stability of the bioanode. Carbon nanostructured material, the multiwalled carbon nanotube (MWNTs) paper (buckeye paper (BEP)), and the polymeric structure of chitosan-carbon nanotubes (CNTs) mixture are integrated in the design. Integration of these nanostructured materials with various enzymes-alcohol, lactate and glucose dehydrogenases (ADH, LDH and GDH respectively)-was performed and analyzed. Polymethylene green (PMG) is used as a catalyst toward the oxidation of NADH to NAD+. The GDH-based anodic interface showed the best performance in the static electrolytic cell as well as in the quasi-2D flow-fan cell. Michaelis-Menten analysis on the GDH-based bioanode showed an IMax = 3.382 ± 0.180 mA.cm−2 and KM = 17.5 ± 3.1 mM compared to IMax = 226.6 ± 10.1 μA.cm−2 and KM = 16.0 ± 2.5 mM for ADH and, IMax = 53.4 ± 5.1 μA.cm−2 and KM = 6.6 ± 3.3 mM for LDH respectively (electrolytic cell). Stability studies showed the GDH- bioanode conserved ∼80% of its initial performance at 15 days and ∼65% at 30 days of dry storage at 4°C.

The effect of surface energy, adsorbed RGD peptides and fibronectin on the attachment and spreading of cells on multiwalled carbon nanotube papers

We report that hydrophilic oxidized multiwalled carbon nanotube papers (CNPs) were efficient substrates for attachment, spreading, and proliferation of MG-63 cells. Complete spreading occurred in the first 4 h of culture even without complete serum or pre-adsorbed adhesion proteins such as collagen or fibronectin. By contrast, the density of adherent cell on hydrophobic CNPs was low. Spreading did not happen after 24 h of culture in absence of serum proteins and growth factors on such papers. Cell viability concomitantly decreased. We also observed that a short RGD peptide, designed to adsorb on both hydrophobic and hydrophilic CNPs, enhanced adhesion, spreading, and proliferation only on hydrophilic CNPs. By contrast, adsorbed fibronectin triggers cell adhesion and spreading on both types of CNPs. Our results show that the imitation of tissue basal membranes with the nanofibrous structure of CNPs is insufficient to trigger the proliferation and spread of cells. Chemical cues are also needed for cells to spread. CNPs, however, offer a better substrate for adhesion protein absorption than do non-porous polymers.

Electric Field Induced, Superhydrophobic to Superhydrophilic Switching in Multiwalled Carbon Nanotube Papers

Superhydrophobic multiwalled carbon nanotube bucky paper, fabricated after ozonolysis, shows fascinating electrowetting behavior, which could be remarkably tuned by changing key solution variables like the ionic strength, the nature of the electrolyte, and the pH of the water droplet. More significantly, the droplet behavior can be reversibly switched between superhydrophobic, Cassie-Baxter state to hydrophilic, Wenzel state by the application of an electric field, especially below a threshold value.

Gas-phase surface functionalization of multi-walled carbon nanotubes with vacuum UV photo-oxidation

For bulk processing of carbon nanotubes, an important first step in adhesion to the nanotubes is often liquid-phase functionalization through chemical oxidation with acids (e.g., nitric and sulfuric), peroxides and/or potassium permanganate. In comparison, gas-phase photo-oxidation can be an alternative to introduce oxygenated functional groups on the surfaces of carbon nanotubes without the generation of liquid waste. In the present study, vacuum UV photo-oxidation of multi-walled carbon nanotube (MWNT) paper was investigated downstream from an Ar microwave plasma. X-ray Photoelectron Spectroscopy (XPS) was used to detect the carbon- and oxygen-containing functional groups in the top 2–5 nm of the sample's surface. The current results are compared to previous investigations using MWNT powder and single-walled carbon nanotube (SWNT) paper showing decreased levels of oxidation in MWNT samples.