Views: 4 Author: Site Editor Publish Time: 2023-05-06 Origin: Site
Fullerenes are allotropes of carbon whose molecules consist of carbon atoms joined by single and double bonds to form a closed or partially closed network with fused rings of five to seven atoms.Molecules can be hollow spheres, ellipsoids, tubes, or many other shapes and sizes.Graphene (isolated atomic layers of graphite) is a planar grid of regular hexagonal rings and can be seen as an extreme member of this family.Fullerenes with closed-lattice topology are informally represented by their empirical formula Cn, usually written Cn, where n is the number of carbon atoms.However, for certain values of n, more than one isomer may exist.
The family is named after the most famous member, buckminsterfullerene (C60), which in turn is named after buckminsterfuller. Blocked fullerenes, especially C60, are also informally known as buckyballs because of their resemblance to the Football Association standard ball ("soccer football"). Nested closed fullerenes are named bucky onions.Cylindrical fullerenes are also known as carbon nanotubes or buckytubes.The bulk solid forms of pure or mixed fullerenes are called fullerenes.
Fullerenes have been predicted for some time, but they were not discovered in nature and in outer space until their accidental synthesis in 1985.The discovery of fullerenes greatly expanded the number of known carbon allotropes, which were previously limited to graphite, diamond, and amorphous carbons such as soot and charcoal .They have been the subject of intensive research, both in chemistry and in technical applications, especially in the fields of materials science, electronics and nanotechnology.
There are two main families of fullerenes with distinct properties and applications: closed buckyballs and open cylindrical carbon nanotubes.However, hybrid structures exist between these two classes, such as carbon nanobuds nanotubes covered by a hemispherical mesh—or larger “bucky buds.”
Buckminsterfullerene is the smallest fullerene molecule, containing pentagonal and hexagonal rings, where no two pentagons share an edge (which could be unstable, like pentadiene).It is also the most common in terms of natural occurrence, as it can often be found in soot.
The empirical formula of Buckminsterfullerene is C
60, its structure is a truncated icosahedron, similar to a united soccer ball consisting of twenty hexagons and twelve pentagons, each polygon has a carbon atom at its vertex and each polygon has an edge There is a key.The van der Waals diameter of the buckminsterfullerene molecule is about 1.1 nanometers (nm).The core diameter of the buckminster fullerene molecule is about 0.71 nm.Buckminsterfullerene molecules have two bond lengths.The 6:6 ring bond (between the two hexagons) can be considered a "double bond" and is shorter than the 6:5 ring bond (between the hexagon and the pentagon). Its average bond length is 1.4 Å.
Another fairly common fullerene has the empirical formula C70.But fullerenes with 72, 76, 84 or even up to 100 carbon atoms are usually obtained.The smallest possible fullerene is dodecahedral C20.There is no fullerene with 22 vertices.The number of different fullerene C2n increases with n = 12, 13, 14,roughly proportional to n9 (sequence A007894 in OEIS). For example, there are 1812 non-isomorphic fullerenes C60.Note that there is only one form of C60, buckminsterfullerene, without a pair of adjacent pentagons (the smallest such fullerene).To further illustrate the growth, there are 214,127,713 non-isomorphic fullerenes C200 of which 15,655,672 have no adjacent pentagons. Optimized structures of many fullerene isomers published and listed online.
Heterofullerenes have heteroatoms replacing carbons in cage or tube structures.Discovered in 1993 they greatly expand the entire class of fullerenes and can have dangling bonds on their surface.Notable examples include boron, nitrogen (azafullerenes), oxygen and phosphorus derivatives.
Carbon nanotubes are cylindrical fullerenes.These carbon tubes are usually only a few nanometers wide, but they can vary in length from less than a micron to several millimeters.They usually have closed ends, but can also be open.There are also cases where the tube reduces in diameter before closing.Their unique molecular structure results in extraordinary macroscopic properties, including high tensile strength, high electrical conductivity, high ductility, high thermal conductivity, and relative chemical inertness (because it is cylindrical and "planar" that is, it has no "exposed" atoms are easily substituted).One proposed use of carbon nanotubes, developed by researchers at Rensselaer Polytechnic Institute in 2007, is in paper batteries. Another highly speculated use in space technology is the production of high-strength carbon cables needed for space elevators.