Bindu Sadanadan

Photoinduced oxidation of carbon nanotubes

Photoinduced phenomena are of general interest for new materials. Recently, photoinduced molecular desorption of oxygen has been reported in carbon nanotubes. Here we present, using thermopower measurements, that carbon nanotubes when exposed simultaneously to UV light and oxygen exhibit photoinduced oxidation of the nanotubes. At least two plausible mechanisms for the experimentally observed photoinduced oxidation are proposed: (i) a lower energy barrier for the adsorption of photo-generated singlet oxygen, or (ii) due to the presence of defects in carbon nanotubes that may facilitate the formation of locally electron-deficient and electron-rich regions on the nanotubes which facilitate the adsorption of oxygen molecules on the nanotubes.

Electrochemical insertion of lithium into multi-walled carbon nanotubes prepared by catalytic decomposition

Various electrochemical techniques have been used to study the electrochemical insertion (extraction) of lithium into (from) multi-walled carbon nanotubes (MWNTs) prepared by catalytic decomposition of ferrocene and xylene. The galvanostatic charge/discharge profiles display a small hysteretic loss and the cyclic voltammograms are quite symmetric in the shape of cathodic and anodic branches, implying that lithium insertion/extraction process is highly reversible. In addition, rate capability and cycleability of charge into the MWNTs are satisfactory. The excellent reversibility and small hysteretic loss of the MWNT are attributed to the extremely pure structural character of the MWNTs with moderate chemical diffusion coefficient of lithium through the structure.

Electronic properties of polyaniline/carbon nanotube composites

Composites of high molecular weight polyaniline and carbon nanotubes are investigated for electronic device applications. Physical characterization by Thermogravimetric analysis and atomic force microscopy indicates that polyaniline containing 1% Carbon Nanotubes is suitable for organic devices. Measured electrical characteristics of Schottky diodes fabricated using these materials exhibit current levels in the polyaniline/carbon nanotube composite devices nearly an order of magnitude higher than in the polyaniline devices.

Mechanical and Electrical Properties of Solution-Processed Polyaniline/Multiwalled Carbon Nanotube Composite Films

Mechanical and electrical properties of high molecular weight polyaniline/multiwalled carbon nanotube composite films were investigated. Addition of carbon nanotubes to polyaniline films was accomplished by solution processing. Physical characterization of these composites by thermogravimetric analysis, tensile testing, dynamic thermal mechanical analysis, and atomic force microscopy measurements indicate that polyaniline containing 1% carbon nanotubes is more mechanically and thermally stable than neat polyaniline. Rectifying aluminum contacts were fabricated using this composition of the composite material, along with neat polyaniline for comparison. The measured electrical characteristics indicate that the current levels of the polyaniline/carbon nanotube composite devices are nearly an order of magnitude higher than those of the polyaniline devices; thus, this composite material has the potential for applications in organic electronics.

Coupling of photon energy via a multiwalled carbon nanotube array

Fluorescent beads were excited by a laser beam coupled through a multiwalled carbon nanotube array. The images of the fluorescent beads showed a distinctive dependence on the polarization direction of the laser beam owing to the surface plasmons induced from the metallic property of the array. The thickness of the array is 2μm as compared to the metallic films of tens of nanometers in thickness that are conventionally used for surface plasmon excitation. This remarkable photon coupling capacity of a multiwalled carbon nanotube array is attributed to the confinement of electrons in its outermost tube shells and ballistic transport.

Mechanical Properties Of Polyaniline / Multi-walled Carbon Nanotube Composite Films

High molecular weight polyaniline / multi-walled carbon nanotube composite films were fabricated using solution processing. Composite films with various weight percentages of multiwalled carbon nanotubes were fabricated. Physical properties of these composites were analyzed by thermogravimetric analysis, tensile testing, and scanning electron microscopy. These results indicate that the addition of multiwalled nanotubes to polyaniline significantly enhances the mechanical properties of the films. In addition, metal–semiconductor (composite) (MS) contact devices were fabricated, and it was observed that the current level in the films increased with increasing multiwalled nanotube content. Furthermore, it was observed that polyaniline containing one weight percent of carbon nanotubes appears to be the most promising composition for applications in organic electronic devices.