Carbon-Based Nanomaterials/Allotropes: A Glimpse of Their Synthesis, Properties and Some Applications

Abstract

Carbon in its single entity and various forms has been used in technology and human life for many centuries. Since prehistoric times, carbon-based materials such as graphite, charcoal and carbon black have been used as writing and drawing materials. In the past two and a half decades or so, conjugated carbon nanomaterials, especially carbon nanotubes, fullerenes, activated carbon and graphite have been used as energy materials due to their exclusive properties. Due to their outstanding chemical, mechanical, electrical and thermal properties, carbon nanostructures have recently found application in many diverse areas; including drug delivery, electronics, composite materials, sensors, field emission devices, energy storage and conversion, etc. Following the global energy outlook, it is forecasted that the world energy demand will double by 2050. This calls for a new and efficient means to double the energy supply in order to meet the challenges that forge ahead. Carbon nanomaterials are believed to be appropriate and promising (when used as energy materials) to cushion the threat. Consequently, the amazing properties of these materials and greatest potentials towards greener and environment friendly synthesis methods and industrial scale production of carbon nanostructured materials is undoubtedly necessary and can therefore be glimpsed as the focal point of many researchers in science and technology in the 21st century. This is based on the incredible future that lies ahead with these smart carbon-based materials. This review is determined to give a synopsis of new advances towards their synthesis, properties, and some applications as reported in the existing literatures.

Keywords: applications; carbon nanostructures; materials science; properties; synthesis.

Figure 1

Structural illustration of some 0-, 1-, 2- and 3-dimensional carbon nanomaterials with sp² and sp³ hybridization allotropes occurring in different crystallographic forms [44].

Figure 2

Field emission scanning electron and polarized light micrographs of the platy morphology of flake graphite.

Figure 3

(a) Raman spectra of graphene as compared to that of graphite measured at 514.5 nm; (b) comparison of the 2D peaks in graphene and graphite. Reproduced with permission from [51].

Figure 4

Structure of graphene configured to buckyballs (0-dimensional) by wrapping up, to nanotubes (1-dimensional) via rolling and to graphite (3-dimensional) by stacking. Reproduced with permission from [10]. Copyright nature materials.

Figure 5

A schematic diagram illustrating the main processes frequently employed for the preparation of graphene along with their key features, and the existing and prospective applications. Reproduced with permission from [107].

Figure 6

Metal compounds that are commonly used as the catalyst to synthesize single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs).

Figure 7

Various types of applications of carbon nanomaterials in relation to their properties. Properties were given in blue text and applications in red.