ABSTRACT
Since the discovery of carbon nanotubes (CNTs) by Iijima in 1991 [1], great progress has been made toward many applications, including, for example:
• Materials • Chemical and biological separation, purification, and catalysis • Energy storage such as hydrogen storage, fuel cells, and the lithium battery • Composites for coating, filling, and structural materials
• Devices • Probes, sensors, and actuators for molecular imaging, sensing, and manipulation • Transistors, memories, logic devices, and other nanoelectronic devices • Field emission devices for x-ray instruments, flat panel display, and other vacuum nanoelec-
tronic applications
The advantages of these applications have been demonstrated, including their small size, low power, low weight, and high performance, and will be discussed in the following chapters. These applications and advantages can be understood by the unique structure and properties of nanotubes, as outlined below:
• Structures (Sections 1.1-1.3) •
Bonding:
sp
hybrid orbital allows carbon atoms to form hexagons and occasionally pentagons and pentagon units by in-plane
σ
bonding and out-of-plane
π
bonding. •
Defect-free nanotubes:
these are tubular structures of hexagonal network with a diameter as small as 0.4 nm. Tube curvature results in
σ−π
rehybridization or mixing.
