Carbon Nanotubes and Graphene - Research and Applications

CNTs with bamboo-like (B-CNTs) structure has been prepared via a CVD process with novel carbon precursor. The potential application of B-CNTs as electric conductive additive and anode materials for lithium ion batteries was explored.

The test cell with B-CNTs as anode material shows low reversible capacity of 135 mAh g^(-1) and very low initial cycle efficiency of 17.3%, which indicates that so-prepared B-CNTs is not suitable for anode material in lithium ion batteries. However, the EIS spectra prove that B-CNTs is better electric conductive additive than MWCNTs and traditional carbon black (CB). The electric resistance of the electrode is decreased around 20 Ohm when B-CNTs is used instead of CB. The cycle stability is also enhanced, thus B-CNTs is promising electric conductive additive in electrode for lithium ion batteries.
Source: Journal of Power Sources (2008), article in press.

Manganese oxide/carbon nanotubes (MO/CNTs) composite was prepared by hydrothermally reducing KMnO4 with CNTs, where the used CNTs are of dual role, i.e, they serve as reductant during reaction and the remaining CNTs act as conducting agent in the composite. This composite was characterized by X-ray diffraction and scanning electron microscopy techniques. In addition, the electrochemical performances of the composite were investigated, which suggested an excellent rate-capability of this material; e.g., it delivered a high discharge capacity as 131 mAh g^(-1) at a high current density of 4 A g^(-1) (20 C), and high capacity at low discharge current density, e.g., about 209 mAh g^(-1) at 0.2 C rate. Therefore, such a MO/CNTs composite is promising in high-power application of lithium battery and electrochemical capacitor.
Source: Materials Letters (2008), article in press.

Researchers have removed the unwrapped double-stranded DNA (dsDNA) from the dsDNA-solubilized single-wall carbon nanotube (SWCNT) aqueous solutions to obtain size-separated DNA/SWCNT hybrids (fr1-fr4). By using the re-injection procedure of the size-exclusion chromatography SEC-HPLC, researchers have discovered that, at the SEC chromatograph level, the fractionated dsDNA/SWCNT hybrids are highly stable without desorption from the hybrids to the unbound dsDNA for at least one month. The interaction of single-strand DNA (ssDNA) and SWCNTs is expected to be stronger than that of dsDNA and SWCNTs. Therefore, isolated ssDNA/SWCNTs hybrids should have similar stability. The present finding is important not only in the fundamental analysis of dsDNA/SWCNT hybrids, but also for their applications especially in biological areas.

Source: Chemical Physics Letters (2008), article in press

Researchers have developed a facile yet versatile and effective method for functionalization of carbon nanotubes with nanoparticles by covalent interaction. Densely distributed magnetite nanoparticles (MNP) with a size of ~8 nm have been deposited on the surface of carbon nanotubes (CNT) by covalent interaction, forming hybrid nanostructures. Transmission electron microscopy (TEM), FT-IR spectroscopy, and X-ray diffraction (XRD) analysis have been used to study the formation of MNP/CNT nanostructure.

The strategy employed is quite generic and applicable to a variety of nanoparticles. More work is under way to extend this method to attach other nanoparticles (e.g. semiconductor nanoparticles, electrical nanoparticles, bio-nanoparticles, etc.) on the CNTs by choosing different kinds of surface functional groups and surface charges. Therefore, the covalent binding process can be regarded as a general approach to effective functionalization of carbon nanotubes with various nanoparticles for a wide range of potential applications, including in advanced sensing, nanoelectronics, chemical sensing, field-emission displays, nanotribology, cell adhesion/biorecognition investigations, and catalytic systems.