Free Fullerenes: Structure, Properties And Applications Report Example

Introduction

In 1970, Osawa, a Japanese scientist, have predicted the existence of a new allotrope of the carbon element, which according to him, would be composed of 60 atoms of carbon. Indeed, in 1985, Sir Harold W. Kroto of the United Kingdom together with Richard E. Smalley and Robert F. Curl, Jr., of the United States discovered the another allotrope of carbon in a research facility of Rice University. Consequently, because of the geodesic structure of the element, they named the newly discovered carbon element as ‘buckminsterfullerene,’ after Buckminster Fuller, the American architect who invented the geodesic dome. Because of their pioneering work in fullerenes, the trio was awarded the Nobel Prize in 1996. Before the discovery of fullerenes, it is believed that carbon has three natural occurring allotropes. The first two are elemental carbon allotropes, the diamond and the graphite while the third one are amorphous carbons, or carbon compounds that does not follow a rigid crystalline structure and has short range structural order such as coal and soot. Although carbon, as an important life element, has been extensively studied, the discovery of fullerenes revolutionized the chemical synthesis of elemental carbon and has led to the discovery and synthesis of several carbon allotropes. Currently, there is a growing family of carbon allotropes that includes hybrids of fullerene, nanotubes and graphene. The discovery of fullerenes is still a work in progress. As stated by Hirsch, “Keeping in mind the numerous possible carbon modifications and the number of scientists investigating this challenge, these revelations have certainly not come to an end”.

Structure

The first fullerene that was discovered by Croto, Smalley and Curl was a molecule composed of 60 carbon atoms (C60) that are arranged in a sphere resembling that of a soccer ball. In general, carbon atoms bonds in three distinct configurations, the sp3, sp2 and sp1 configurations. Fullerenes uses sp2 wherein “three identical co-planar trigonally directed sp2 orbitals are formed with each orbital being separated by an angle of 120˚. Just like the modern soccer ball, the C60 is composed of a network of symmetrical truncated icosahedron, composed of 12 pentagons and 20 hexagons. The structure of the fullerene is based on the theorem of Leonhard Euler wherein it states that “a spherical surface built up from pentagons and hexagons must have exactly 12 pentagons”. The figure below shows a graphic representation of fullerene C60.
Figure 1. The symmetrical truncated icosahedron structure of buckminsterfullerene (C60).
Theoretically, fullerenes can take several structures depending on the conditions of its synthesis. The many ways that carbon atoms can bond with each other led scientists to theorize that carbon has many other allotropes. According to Hirsch, there are several ways of deriving fullerenes and their hybrids because of the many ways that carbon can bond with its own molecule as well as with other molecules that are introduced during synthesis. Smaller fullerenes, or fullerenes with lesser atoms as well as higher fullerenes or fullerenes with more than 60 carbon atoms, can also be synthesized.

Properties

Fullerenes have many properties that fascinate scientists and engineers. In general, fullerenes are stable carbon molecule although it can bond with neighboring atoms because of its weak ‘van der Waals’ bond. Unlike carbon compounds that have edges that bond with other elements, fullerenes are chemically inert and do not rely on other atoms to tie up its bonds. Due to its atomic sp2 configuration, fullerenes, such as C60, “behaves like an electron deficient alkenes and reacts readily with electron rich species”. Structural integrity is also one of the significant properties of fullerenes. Because of their geodesic structure, fullerenes are extremely strong molecules and are able to resists huge pressures. According to research, fullerenes will bounce back to its shape after being subjected to a pressure of 3,000 atmospheres. However, because of their weak external bond, fullerenes are not stable in solid form and is soluble in water. Fullerenes also have endohedral and exohedral properties. Endohedral fullerenes are those that can be introduced with different atoms inside the carbon framework while exohedral fullerenes are those that are modified externally. It is also found that fullerenes have photovoltaic properties when combined with other molecules. As observed by Hirsch, “For example, the exohedral covalent binding of organic donor molecules such as porphyrins has attracted a lot of attention, to simulate natural photosynthesis or to transform light into chemical energy”.

Applications

Even before the discovery of fullerenes, the carbon element and its compounds has been known to be one of the hardest materials on earth and has been extensively used in various engineering applications. Upon its discovery, it is found that the extremely strong molecular configuration of fullerenes makes it a desirable quality for lubricant applications. Fullerenes are also being developed in the tire industry as a chemical additive in polymers for increasing the strength of tires. Also, its photovoltaic properties can be utilized further for possible solar energy applications. According to research, fullerenes are being investigated to function as electron acceptors in solar cells. And since fullerenes react with electron rich molecules, it can be utilized as an anti-oxidant to capture free radicals that are desirable for human health. The endohedral property of fullerenes is also viewed with much excitement as to its practical applications. Accordingly, it can be used to trap drug molecules inside and designed to have some triggering mechanism as it is released inside the body. There are enormous ways on how fullerenes can be utilized and applied in scientific and engineering applications. The most recent of which is the development of Nano science and nanotechnology. Nano materials made of fullerene and its hybrids are characterized by their excellent conductivity as well as their strength. Engineered nanotubes and fullerene are currently being developed as semiconductors and transistors in molecular level. When fully developed, this could revolutionize the field of physical sciences especially in medical and engineering disciplines.

References

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