Carbon atoms in nanotubes, like those in buckyballs, have the ability to covalently bond to other atoms or molecules creating a new molecule with customized properties. Bonding an atom or molecule to a nanotube to change its properties is called functionalization.
Electrons in carbon nanotubes can only be at certain energy levels, just like electrons in atoms. A nanotube is metallic if the energy level that allows delocalized electrons to flow between atoms throughout the nanotube referred to as the conduction band is right above the energy level used by electrons attached to atoms the valance band.
In a metallic nanotube, electrons can easily move to the conduction band. A nanotube is semiconducting if the energy level of the conduction band is high enough so that there is an energy gap between it and the valance band. In this case, additional energy, such as light, is needed for an electron to jump that gap to move to the conduction band. While there is no gap between the valance and conduction bands for armchair nanotubes which makes them metallic , an energy gap does exist between the valance and conduction bands in about two thirds of zigzag and chiral nanotubes — which makes them semiconducting.
Most current production processes for nanotubes create both metallic and semiconductor nanotubes. Researchers at Rice University have hit on a way to control this process. They take short lengths of nanotubes of the type they want and attach nanocatalyst particles typically a metal such as nickel to one end. These nanotubes are placed in the reaction chamber and act like seeds. New, long, nanotubes are grown from these seeds, kind of like nanotube cloning. Nanotube Applications.
Nanotube Discovery. The bonding also explains the hardness of diamond and its high melting point. Significant quantities of energy would be needed to separate atoms so strongly bonded together. Graphite contains layers of carbon atoms.
Graphite is black, shiny and opaque. It is not transparent. It is also a very slippery material. It is used in pencil leads because layers easily slide onto the paper, leaving a black mark. It is a component of many lubricants , for example bicycle chain oil. Graphite is insoluble in water. It has a high melting point and is a good conductor of electricity, which makes it a suitable material for the electrodes needed in electrolysis. Each carbon atom is bonded into its layer with three strong covalent bonds.
Weak intermolecular forces exist between buckyballs. These need little energy to overcome, so substances consisting of buckyballs are slippery and have lower melting points than graphite or diamond.
The ball structure means that this type of fullerene structure can be used to carry small molecules. This can be used to carry medical drugs into the body. Graphene and fullerenes Nanoparticles have very small sizes and large surface area to volume ratios. Graphene Graphene is an allotrope of carbon.
Fullerenes A fullerene is a molecular allotrope of carbon. Nanotubes A nanotube resembles a layer of graphene, rolled into a tube shape. Nanotubes can be several millimetres long but only a few nanometres wide Nanotubes can be added to other materials, for example in sports equipment, to make them stronger.
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