Carbon nanohorn is a new allotrope of carbon found in recent years. It can be seen as a single layer of graphite, one end is an angular closed structure and the other end is an open structure. The diameter of the carbon nanowires is generally from 2 to 5 nanometers and the length is from several nanometers to tens of nanometers. The carbon nanowires usually aggregate into spherical aggregates of 50-100 nanometers in diameter, with one end of the pyramid pointing to the outside of the aggregate. The pyramidal hollow structure and the unique morphology of carbon nanohorn have great potential in catalyst carrier, fuel cell, lithium ion battery and drug transport carrier. Therefore, the synthesis and characterization of carbon nanohorn have become a hotspot in scientific research recent years.

Carbon nanohorns CNHs have various important applications as below:

(1) Adsorption and storage materials

CNHs have a large specific surface area and high binding energy, can be used as a new type of adsorption materials, such as adsorption gas xenon and hydrogen, CNHs have two kinds of adsorption sites: the gap between the angle and the angle of the gap. The use of nitric acid to treat CNHs can increase the pore volume of the interior and the gap significantly and can be used to store supercritical methane. In addition, CNHs can also be used to adsorb liquids such as water, benzene and ethanol.

(2) Catalyst carrier

Unique structure of CNHs can enhance the durability of the catalyst. The Pd-CNHs can obtain the Pd-CNHs with an average size of 2.3 nm, and the gas phase reaction of H2-O2 and some liquid reaction, such as coupling reaction, which have good catalytic ability. The particle size of Pt particles synthesized by CNHs is only about 2 nm, and it has good dispersibility. Pt-CNHs as the electrode of fuel cell have very good activity and stability.

(3) Drug carrier

CNHs have a large specific surface area and numerous angular voids that can adsorb large amounts of molecules. Compared with CNTs, SWCNHs have smaller pore size and are suitable for adsorption of relatively small molecules. CNHs do not use metal catalysts to avoid cytotoxicity caused by metal impurities. CNHs are assembled into micron-like bundles or form spherical aggregates that enhance the permeability and retention of drugs under passive tumor targeting conditions, and tend to be enriched near tumor tissue to provide a higher resistance to tumor.

(4) Electrochemical applications

CNHs can be used as electrode materials in electrochemical sensors. CNHs modified glassy carbon electrode on the uric acid, dopamine and ascorbic acid and other good electrocatalytic performance; CNHs directly grown on the carbon fiber can be made of independent electrodes for lithium-ion batteries; through the opening of large size nano-window, CNHs can be built a high-capacitance supercapacitor in an organic solvent.

(5) Other applications

Tubular carbon material can absorb the light in the near infrared region so the cells can be killed by local photothermal therapy; CNHs and metal oxide composite materials can also be used for lithium ion battery anode material to improve the performance of the battery; and CNHs doped MgB2 will have magnetic properties, making it a new superconducting material.

by Jemma