Understanding the Structure of Carbon Nanotubes


Since carbon nanotubes were discovered on accident by Sumio Iijima in 1991 during another experiment, hundreds of studies have been started and dedicated to achieving a better understanding of the structure of carbon nanotubes.

But why would science expend so much effort on understanding an element that is already being used in the production of materials for space shuttles and strengthening plants, and that is being considered for an array of other uses? Is it possible that there are still mysteries locked within the structure of carbon nanotubes that will open more doors for its use and everyday applications? The answer is: probably.

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Although the structure of carbon nanotubes has been extensively studied by researchers and scientists in a wide variety of fields including materials science, architecture, agriculture and engineering, the full implications of this tiny microscopic wonder are still locked away in its unique natural creation, varied structural components and its ability to be both immensely flexible as well as incredibly strong.

But before delving into the actual structural components that make up this small scientific wonder, it’s important to lay groundwork for understanding exactly what it is that makes carbon nanotubes so unique. The structure of carbon nanotubes is easily explained for the untrained through a simple setup using post-its and paper cups.

In this method, the “experimenter” is asked to test the strength of a stack of post-its (akin to graphite) that have made a bridge across two paper cups. Then, in the same “experiment”, the method changes and the experimenter is asked to roll the post-it stacks (akin to carbon nanotubes) and perform the test again.

Naturally it is assumed through this test that the rolled post-its will hold more pennies before buckling—if they buckle at all—than the flat stacks of post-its. For those untrained in science, this is an incredibly easy way to understand how the structure of a carbon nanotube—although the nanotube is made of simple graphite—changes the structural strength and abilities of the graphite immensely.

This test is so simple and correct, in fact, that it should help any reader or researcher begin to understand and identify the more complex nature of carbon nanotubes.

Carbon nanotubes appear to be sheets of graphite cells that have been mended together to look almost like a latticework fence and then rolled up in a tube shape. Although this is a simple explanation for the look of the structure of carbon nanotubes, this is not how carbon nanotubes are created, nor does it explain their immense strength or other incredible structural abilities.

Carbon nanotubes are typically around two millimeters in length or less (with some being only a nanometer in length) but have the capability, if formed correctly, of being more than one hundred times stronger than steel.

Carbon nanotubes are capable of being formed in either single walled structures, also known as Single Walled Carbon Nanotubes (SWCNTs) and multiple walled structures, also known as Multi-Walled Carbon Nanotubes (MWCNTs). Each structure of carbon nanotubes has its own set of properties that make it appropriate for different uses across science, architecture, geology, agriculture and engineering, among the many fields carbon nanotubes have become useful for.

Single walled carbon nanotubes have electric properties that are not present in multiwalled carbon nanotubes due to the makeup of their structure. These single walled structures can be used in large quantities for thermal purposes—or in other words, to help produce heat. Additionally, the electric properties of these macro miniature carbon nanotubes make them perfect for engineering electronics to even smaller than their current “nano” sized status.

Although they do not share the same electric properties in the structure of carbon nanotubes as single walled carbon nanotubes, multi walled carbon nanotubes have their place in science and exhibit several properties that are more useful that single walled carbon nanotubes for a variety of applications. For instance, the makeup of multi walled carbon nanotubes makes them perfect for use in the medical field.

The medical field utilizes multi walled carbon nanotubes in the production of sensors for medical diagnostics. Biosensors are able to detect microscopic amounts of biological or chemical agents, which help to diagnose an illness much quicker—these same types of sensors are being used in the military to protect soldiers as they move through hostile territories. Multi walled carbon nanotubes are used for these purposes because of their electrochemically advanced properties, which are due in part to their double or multi walled structures.

In addition to the two different basic structures, there are three different types of carbon nanotubes that are possible. These three types of carbon nanotubes are armchair carbon nanotubes, zigzag carbon nanotubes and chiral carbon nanotubes.

The difference in these types of carbon nanotubes are created depending on how the graphite is “rolled up” during its creation process. Science has found ways to recreate these natural processes and man-made nanotubes are being produced at faster and faster paces each and every day. Each structure of carbon nanotubes in these three varities is different and has different implications for science.

However, determining their exact physical properties and the entire scope of the implications for science and other fields is incredibly difficult because, although science is able to recreate these nanotubes, seeing them under a microscope is difficult—in past because they are so small, and also due to the structure of carbon nanotubes. It is interesting that the very thing scientists wish to examine about carbon nanotubes is the thing that stands in the way of them making discoveries and gaining an understanding about the implications of carbon nanotubes for everyday living.

In Microscopy, many new scanning force techniques are being developed by scientists for nanoscale inspection.  Scanning force microscopes top the list of the best microscopes ever to be developed to date and further developments in this field only strengthen its place in the nanosciences.  The Atomic Force Microscope is used to identify and characterize individual nanotubes.  Due to its nature, the Atomic Force Microscope tip has incorporated the carbon nanotube for use in imaging high aspect ratio features for industrial applications.

The structure of carbon nanotubes is still a mystery in many ways because carbon nanotubes are a tiny, yet complex natural occurrence that cannot be completely controlled, but only harnessed by today’s science. Although science has an understanding of the physical properties of carbon nanotubes at a base level, there is more to discover about the structural implications of carbon nanotubes, not only for science but for everyday living as well.

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