electronic properties. In other words, derivatization can alter the properties of
pristine CNT in a tailor made manner. Similarly, gallium nitride (GaN) nanotubes
are used for nanoscale electronics, biochemical sensing and in general optoelectronics applications [38].
3.2 Nanorod/Nanowire
Nanorod/nanowire is basically a solid cylinder with the morphology of nanoscale
object each of their dimension ranging from 1 to 100 nm. They are synthesized from
metals or semiconducting materials with the aspect ratios of 3 to 5. Nanorods/
nanowires are produced by chemical synthesis or a combination of ligands acting as
shape control agents and bond to different facets of the nanorods with different
strengths. This allows the different faces of the nanorod to grow at different rates,
producing an elongated nanostructural object like long sticks with a nanoscale
dimension having a large length. Zinc oxide (ZnO) nanorods have been used to
fabricate nano-scale electronic devices, including field effect transistor, ultraviolet
photo-detector, Schottky diode and light-emitting diode. Nanorods of gold, copper,
alumina, silicon, platinum and nickel are also produced by direct chemical synthesis or electrochemical methods from porous alumina or polycarbonate membrane
templates in presence of a surfactant [39–43].
3.3 Nanofibers
Nanofibers are defined as fibers with diameters less than 100 nm. They can be
produced by using interfacial polymerization, electrospinning, and force spinning
methods. CNFs are graphitized fibers produced by catalytic syntheses. CNF are
formed mainly in gas phase during the process of decaying ethane, methane and
other hydrocarbon in presence of a catalyst and then purified to remove aromatic
hydrocarbons [44]. Inorganic nanofibers can also be prepared from various kinds of
inorganic substances through electrospinning technique. Often used ceramic materials with nanofiber morphology are titanium dioxide (TiO 2 ) [45], silicon dioxide
(SiO 2 ) [46], zirconium dioxide (ZrO 2 ) [47], aluminum oxide (Al 2 O 3 ) [48], lithium
titanate (Li 4 Ti 5 O 12 ) [49], titanium nitride (TiN) [50] or platinum (Pt) [51]. The
synthesis of these nanofibers usually consists of two main steps. In the first step, the
polymer (organic) nanofibers are created by conventional electrospinning technique
and subsequently they are transformed into ceramics by heat treatment. Other
production methods include direct drawing from a solution or melt. Potential uses
of nanofibers are in the biomedical arena such as artificial organ components, tissue
engineering, implant material, drug delivery, and energy applications like Li-ion
batteries [52], photovoltaic cells [53], membrane fuel cells [54] and dye-sensitized
solar cells [55] etc. (Scheme 1).
18
K.K. Jana et al.
pristine CNT in a tailor made manner. Similarly, gallium nitride (GaN) nanotubes
are used for nanoscale electronics, biochemical sensing and in general optoelectronics applications [38].
3.2 Nanorod/Nanowire
Nanorod/nanowire is basically a solid cylinder with the morphology of nanoscale
object each of their dimension ranging from 1 to 100 nm. They are synthesized from
metals or semiconducting materials with the aspect ratios of 3 to 5. Nanorods/
nanowires are produced by chemical synthesis or a combination of ligands acting as
shape control agents and bond to different facets of the nanorods with different
strengths. This allows the different faces of the nanorod to grow at different rates,
producing an elongated nanostructural object like long sticks with a nanoscale
dimension having a large length. Zinc oxide (ZnO) nanorods have been used to
fabricate nano-scale electronic devices, including field effect transistor, ultraviolet
photo-detector, Schottky diode and light-emitting diode. Nanorods of gold, copper,
alumina, silicon, platinum and nickel are also produced by direct chemical synthesis or electrochemical methods from porous alumina or polycarbonate membrane
templates in presence of a surfactant [39–43].
3.3 Nanofibers
Nanofibers are defined as fibers with diameters less than 100 nm. They can be
produced by using interfacial polymerization, electrospinning, and force spinning
methods. CNFs are graphitized fibers produced by catalytic syntheses. CNF are
formed mainly in gas phase during the process of decaying ethane, methane and
other hydrocarbon in presence of a catalyst and then purified to remove aromatic
hydrocarbons [44]. Inorganic nanofibers can also be prepared from various kinds of
inorganic substances through electrospinning technique. Often used ceramic materials with nanofiber morphology are titanium dioxide (TiO 2 ) [45], silicon dioxide
(SiO 2 ) [46], zirconium dioxide (ZrO 2 ) [47], aluminum oxide (Al 2 O 3 ) [48], lithium
titanate (Li 4 Ti 5 O 12 ) [49], titanium nitride (TiN) [50] or platinum (Pt) [51]. The
synthesis of these nanofibers usually consists of two main steps. In the first step, the
polymer (organic) nanofibers are created by conventional electrospinning technique
and subsequently they are transformed into ceramics by heat treatment. Other
production methods include direct drawing from a solution or melt. Potential uses
of nanofibers are in the biomedical arena such as artificial organ components, tissue
engineering, implant material, drug delivery, and energy applications like Li-ion
batteries [52], photovoltaic cells [53], membrane fuel cells [54] and dye-sensitized
solar cells [55] etc. (Scheme 1).
18
K.K. Jana et al.