Abstract

Nanorods are nanostructures that are the object of fundamental and applied research. They may be prepared from carbon, gold, zinc oxide, and many other materials. They are bigger than individual atoms (measured in angstroms, 1 Å = 10<sup>10</sup> m) and also than small molecules. The turning point for nanomaterials research was the discovery of carbon nanotubes in 1991. Their mechanical, electrical, and optical properties depend upon their size, allowing for multiple applications. Also, nanorods may be functionalized for different applications. In this Chapter, the methods of synthesis and analysis, and the applications of carbon, zinc oxide, gold, and magnetic nanorods are reviewed.

Keywords: nanorods, gold nanorods, ZnO nanorods, carbon nanorods, magnetic nanorods

#### 1. Introduction

Nanomaterials are foundations of nanoscience and nanotechnology. The development of nanomaterial has been attracted great interest in the worldwide in the past few years. The turning point for nanomaterials research was the discovery of carbon nanotubes in 1991 [1]. Nanomaterials are usually defined as having a particle size between 1 and 100 nanometers (nm). They are bigger than individual atoms (measured in angstroms, 1 Å = 10<sup>10</sup> m. One nanometer is millionth of millimeter. It is equal to 100,000 times smaller than the diameter of human hair. After this discovery, there was an explosive increase in the number of research teams working in the field. The properties of nanomaterials deviate from those of "bulk" materials with the same composition, thus allowing for many interesting applications. At nanodimensions, quantum effects, like quantum confinement, permit multiple applications [2–4]. Some of nanotechnology applications include alternative energy [3], electronics [5, 6], catalysis [5], biomedicine [2], batteries [7], water treatment [8], and materials reinforcement [9] (Figure 1).

#### 2. Classification of nanomaterial

Classification is based on the number of dimensions, which are not confined to the nanoscale range (<100 nm) (Figure 2 and Table 1):

1. zero-dimensional (0-D);

DOI: http://dx.doi.org/10.5772/intechopen.84550

2. one-dimensional (1-D);

3. two-dimensional (2-D); and

3. One-dimensional (1-D): needle-like shape structure

Nanomaterials: An Overview of Nanorods Synthesis and Optimization

1-D nanostructures as a series of the most important materials owed by it fascinating physical properties. Due distinct structure-dependent properties had lead it application widely especially in solar energy conversion, thermoelectric devices, energy storage technology. 1-D nanostructures mainly show three different

Among those 1-D nanostructures, nanorods have the advantage as it can be made from most elements (metals and nonmetals) and compounds, and the synthetic requirements for their production are more flexible than for nanotubes and nanowires. Nanorods have typical lengths of 10–120 nm. For example, metallic nanorods, semiconductor nanorods, carbon nanorods, and oxides nanorods, are essential for the development of electronic, optical, magnetic, and micromechanical

Nanorod Nanowires Nanotube [9]

bounded.

metal

etc.

Nanowires have typically diameters of a few tens of nm, but the lengths are not

Nanotubes are also like nanowires, in terms of diameter, but hollow and with a standard aspect ratio (length divided by width) of 3–5. Exist as single-or multi-walled. Made: carbon; single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotube (MWCNT) Application: scaffolds or templates

for the building [13].

Made: ceramic, metal oxide,

Application: magnetic devices,

nanogenerator, semiconductor,

nanowires battery,

4.three-dimensional (3-D).

morphologies (Table 2):

ii. nanowires; and

Nanorods similar to nanotube but without internal surface. Less versatile than nanotube but thermally stable Made: carbon, metal oxide,

Application: drug delivery, bioimaging, photothermal therapy nanocapacitors, etc.

Nanorods, nanowires and nanotube.

i. nanorod;

iii. nanotube.

devices [5, 6].

metal

[5, 6]

Table 2.

13

#### Figure 1.

(a) Evolution of science and technology and the future [10]; (b) an example of nanomaterial comparison; and (c) an example of the nanorod image [11].

#### Figure 2.

0-D, 1-D, 2-D and 3-D nanomaterial [12].

Table 1. Details characteristic of nanomaterial classification.

Nanomaterials: An Overview of Nanorods Synthesis and Optimization DOI: http://dx.doi.org/10.5772/intechopen.84550

