Nanostructures and Fascinating Properties of Carbon Nanohorns

Carbon nanohorns (CNHs) also called nanocones are the matter of intense research nowadays because of its unique physical and chemical properties. It is a conical carbon nanostructure consisting of SP2 bonded carbon atoms. The diameter persists in the range of 2–5 nm. In the synthesis of carbon nanohorns, there is no requirement of metal catalysts, and the production takes place in bulk quantities, and the temperature should be normal, i.e., room temperature. These are the two major advantages of CNHs over carbon nanotubes. The process of production of CNHs is cost-effective and catalyst-free on industrial scale. CNHs can be produced using arc discharge and CO2 laser ablation techniques. CNHs consist of thousands of individual nanohorns with 2–5 nm in diameter and 20° cone angle. It aggregates into spherical clusters during synthesis whose diameter is approximately in the range of 100 nm. It limits the dispersion as well as separation of a big cluster shape into discrete nanosized cones and makes the functionalization difficult. We can compensate this limitation with a latest methodology of separating the “dahlia-like” clusters and transfigure into single nanocones. Hence, we have great interest in future in replacing nanostructures like nanotubes, graphene, as well as fullerene with nanohorns. Nanohorns consist of a large number of shapes likes pentagons, hexagons, and heptagons. CNHs are highly pure and thermally stable and have better electrical conductivity making it an important field for future research. Its various applications include supercapacitors, catalyst support or catalyst, drug carrier systems, etc. Linear combination of atomic orbitals (LCAO) technique is useful in calculating the small finest structure of CNHs and related electronic properties. To describe the finest electronic structure as well as total energy differences for system, this approach has been found useful. One of the applications of CNHs is that it is used as electrode for fuel cells. Due to porosity and adsorption capability of CNHs, it can be used for storing materials. Hence, we can conclude that CNHs are having vast application in various fields due to their unique properties.