Synthesis of Nanoparticles and One-Dimensional Nanomaterials - Nanotechnologies for Water Environment Applications - page 32

the products (Xu et al., 2002a). Formation of the desired material is obviously affected
by both the starting material and the surfactants. Also, the viscosity of the flux during
the calcinations, the pH value, and the concentration of the reactant are factors that have
considerable potential to affect the synthesis outcome. As a result, this method can be
considered as a trial-and-error based procedure, especially in terms of obtaining a
suitable dose of chemicals and proper environment (Lu et al., 2006). With this method,
Te nanorods (Liu et al., 2003b), ZnO nanorods (Xu et al., 2002b), NiO nanorods (Xu et
al., 2002a), and PbO nanorods (Cao et al., 2004) have been successfully synthesized.

Other Methods. As previously mentioned, the sonochemical method can be
utilized to synthesize one-dimensional nanostructures; ultrasonic waves are used to
acoustically agitate or alter the reaction environment. By using this process, Fe 3 O 4
nanorods (Kumar et al., 2001) and ZnO nanorods (Hu et al., 2004) have been obtained.

For example, Kumar et al. (2001) synthesized Fe 3 O 4 nanorod by sonochemical
method with iron acetate in the presence of -cyclodextrin which serves as a size-
stabilizer. Ultrasonic irradiation process was conducted under 1.5 atm of Ar at room
temperature (Kumar et al., 2001).
In addition, the hydrothermal method has been employed to synthesize one-
dimensional nanostructures. This method was conducted under an elevated temperature
and a relatively high pressure condition using soluble metal salts. Recently, different
kinds of one-dimensional nanostructures such as MnO 2 nanowires (Eftekhari et al.,
2005), ZnO nanorods (Guo et al., 2005), and MnO 2 nanotubes (Zheng et al., 2005) have
been produced.

One-dimensional TiO 2 nanomaterials (i.e., nanotube, nanofiber, nanoribbon and
nanowire) were synthesized by one-step hydrothermal reaction with TiO 2 powder and
alkaline solution. First, nanotubes were synthesized by using TiO 2 powder at a
temperature range of 100-180 °C. Second, nanofibers were synthesized when
amorphous TiO 2 was used with NaOH at a temperature range of 100-160 °C. Third,
nanoribbons were formed using crystalline or amorphous TiO 2 in NaOH solution in a
temperature range of 180-250 °C. Finally, nanowires with a diameter of 5-10 nm were
obtained by reaction with TiO 2 particles and KOH solution at 130 °C (Yuan and Su,
2004).

2.4 Conclusions

While considerable research has been reported on nanomaterial syntheses, only
selected synthesis methods and synthesized nanomaterials have been discussed in this
chapter, focusing on general methods for the preparation of nanoparticles and one-