Carbon Nanomaterials

Carbon has a variety of electron orbits (sp, sp², sp³ hybrid) characteristics, and the anisotropy of sp2 leads to crystal anisotropy and the anisotropy of the arrangement. Therefore, carbon materials with carbon as the sole constituent element have various properties. The research of carbon nanometer technology has been paid much attention, and various carbon nanometer crystals, needles, rods and barrels emerge in an endless stream.

Applications:

Carbon nanomaterials, with their unique low-dimensional structure, exotic electrical, mechanical properties and quantum size effects, have shown many excellent properties in the fields of energy, environment, biology, medicine, information, aerospace and microwave absorption, with broad application prospects.

• Electrochemical sensors: Carbon nanomaterials have good electrical conductivity, biocompatibility, electrocatalytic performance, and large specific surface area. The electrochemical sensor constructed by carbon nanomaterials can not only increase the specific surface area of the working electrode, but also speed up the electron transfer rate, improve electrode stability, and enhance the sensitivity of detection. In addition, most carbon nanomaterials have the characteristics of doping and adsorption, which makes it easy to functionalize or combine with other nanomaterials, thereby enriching the active groups on the surface and increasing the dispersion and stability of carbon nanomaterials.
• Improvement of agricultural environment: Carbon nanomaterials are widely used in agricultural nanotechnology, especially in the improvement of agricultural ecological environment, such as applying carbon nanomaterials to pesticides and fertilizers. Among agricultural inputs, the utilization rate can be improved, and the problem of environmental pollution caused by its abuse and loss can be greatly reduced. In the treatment of heavy metal ions and organic pollutants in soil and water, carbon nanomaterials have broad application prospects. In addition, carbon nanomaterials can be used to prepare high-sensitivity sensors to quickly and easily detect pollutants (pesticides, heavy metals, organics, etc.) in the agricultural environment to achieve timely detection of pollution and pollution control.
• Rubber material: Nano filler has a large specific surface area and a strong force with the rubber interface. Nano filler/rubber composite materials have more excellent physical properties, thermal conductivity, electrical conductivity and gas/liquid barrier properties than traditional rubber materials. The use of nano filler modified rubber is one of the development trends of the rubber industry.
• Architectural waterproof coating: Architectural waterproof coating is a liquid polymer synthetic material with no fixed shape at room temperature. It can form a tough waterproof coating on the wall surface through the evaporation of solvent or the evaporation of water. Carbon nanomaterials are added to the waterproof coating in the form of slurry to improve the performance of the coating. The carbon nanomaterial slurry is a system in which carbon nanomaterials, solvents, and other additives are mixed. Since the carbon nanomaterials are dispersed in the state rather than dissolved, the slurry is a colloid or suspension. The addition of carbon nanomaterials can improve the water resistance and penetration resistance of the coating.
• Biomedicine: Among the carbon nanomaterials, especially the carbon nanotubes, it can effectively solve the problems of tissue repair, nerve defects and motor skills. It also plays an important role in carrying bio-specific molecules and transporting drugs.

Classification:

Figure 1. Three important carbon nanomaterials.

• Carbon nanotubes: Carbon nanotubes are one-dimensional nanomaterials with light weight, perfect hexagonal structure connection, and many abnormal mechanical, electrical and chemical properties. According to the number of layers of graphene sheets, it can be divided into single-wall carbon nanotubes and multi-wall carbon nanotubes. Compared with the two, single-walled carbon nanotubes have fewer defects and higher uniformity.
• Carbon fiber: Carbon fiber is a new type of high-strength and high-modulus fiber material with a carbon content of more than 95%, which has excellent physical properties such as strong tensile strength of carbon material, soft workability of fiber, high modulus, low density and small linear expansion coefficient.
• Carbon nanosphere: This is the general term for a class of spherical nanomaterials composed of carbon elements, and the first to be discovered is fullerene. Fullerenes are a general term for a series of atomic clusters composed of pure carbon, which are conjugated olefins with closed hollow spherical structures composed of non-planar five-membered rings and six-membered rings.

Production Processes:

• Graphite arc method: The carbon nanomaterial prepared by this method has the advantages of high yield, high purity and short preparation time. The graphite arc method is especially suitable for the preparation of single-wall or multi-wall carbon nanotubes. The changes in the synthesis process parameters have a huge impact on the preparation of carbon nanomaterials, such as the use of different reaction chambers, the difference of the inert medium filled, the diameter of the anode and the composition, the proportion of the mixed metal catalyst added, etc., and have an influence on the purity, yield and properties of the material.
• Pyrolysis polymer method: This method prepares carbon nanomaterials by pyrolyzing certain polymers or metal organics. The heat treatment temperature is the key. The decomposition of the polymer breaks the carbon bonds and reorganizes the carbon to form carbon nanomaterials. The leading factor for producing carbon nanomaterials by this method is to select the appropriate heat treatment temperature, metal catalyst, pyrolysis atmosphere, etc., according to the selected gasification pyrolysate in order to increase the yield and prepare the nanomaterials with the required purity.

References:

1. François Perreault, Andreia Fonseca de Faria, Menachem Elimelech. Environmental applications of graphene-based nanomaterials [J]. Chem. Soc. Rev.,2015, 44, 5861-5896.
2. Deep Jariwala, Vinod K. Sangwan,za Lincoln J. Lauhon,a Tobin J. Marksab, Mark C. Hersam. Carbon nanomaterials for electronics, optoelectronics, photovoltaics, and sensing [J]. Chem. Soc. Rev.,2013, 42, 2824-2860.
3. Li Chaoxu, Mezzenga Raffaele. The interplay between carbon nanomaterials and amyloid fibrils in bio-nanotechnology [J]. Nanoscale, 2013, 5, 6207-6218.