Graphene is a one atom thick membrane, a sheet of carbon atoms arranged in tightly bound hexagons. Graphene is almost unbreakable, tougher than a diamond, and stretchable like a rubber (Palmer, 2012). Graphene was discovered in 2004 by two University of Manchester scientists; a Russian-Dutch scientist Andre Geim and a Russian-British scientist Konstantin Novoselov shared the 2010 Nobel Prize for physics for studying behavior of this one atom thick sheet of carbon (Nobleprize, 2010). According to Geim & Novoselov (2007), graphene is a flat monolayer of carbon atoms tightly packed into a two-dimensional (2D) honeycomb lattice, and is a basic building block for graphitic materials of all other dimensionalities. It can be wrapped up into 0D fullerenes, rolled into 1D nanotubes, or stacked into 3D graphite. Geim and Novoselov were praised for playfulness of their approach that involved producing flakes of graphene using sticky tape: they extracted the material from a piece of graphite that can be found in ordinary pencils using adhesive tape, and repeating the tape-trick until they got miniscule flakes of graphene. Three million sheets of graphene loosely held together on top of each other produce 1mm of graphite. Scientists are able to fabricate molecule-scale structures and devices in graphene with atomic precision (Russo & Golovchenko, 2012). Gardener & Golovchenko (2012) demonstrate that the ice-assisted e-beam lithography can be used to pattern very thin materials deposited on substrate surfaces. The procedure can be performed in situ in a modified scanning electron microscope. A low energy focused electron beam can locally pattern graphene coated with a thin ice layer. Moreover, photons, x-rays generated by atoms may also come back (which is used in X-ray spectroscopy). The scanning probe tools use the nanoscale probe (a small, sharp tip on the end of a lever that is dragged across a nanoscale object) for the scanning probe microscopy. Nanoscale beams or probes interact with a nano material generating signals that can be processed by a computer into pictures. Examples of such tools are the atomic force microscope AFM that measures forces between atoms; and scanning tunneling microscope STM that uses quantum mechanical tunneling between atoms of the probe and atoms on the scanned surface. The nano-scale tips on scanning probe microscopes (SPMs) allow us to even “see” atoms (PennState modules, 2009). Atoms on the probed surface may be arranged by an STM into a quantum corral, which is about 14 nm in diameter. Christopher Lutz, Donald Eigler, and Michael Crommie demonstrated for the first time the quantum corral in 1993 by using an elliptical ring of iron atoms on a copper surface (Ball, 2009). The STM tunneling current can be turned by a computer into a false color STM image of the quantum corral (PennState modules, 2009).
A carbon nanotube is a molecule of carbon in form of a hollow cylinder. A carbon nanotube has a diameter of around one or two nanometers; they can be seen using a scanning tunneling microscope. One nanometer (nm) is one billionth, or 10−9 of a meter. Typical carbon-carbon bond has the length about 0.12-0.15 nm; a DNA double helix has a diameter around 2 nm. Nanotubes and fullerenes are present in structures such as inorganic carbon, DNA, and cell membranes. Both carbon nanotubes and graphene products (such as graphene foams, nanowires, sieves, graphite nanoparticles, or porous carbon) are offered for sale online.
Carbon nanotubes have the nanoscale cross-section areas but they may be many micrometers up to centimeters long. This shapes cause unusual chemical bonding and physical properties, such as great strength: carbon nanotubes are the strongest known materials. Carbon nanotubes may form single wall and multi-wall structures. Nanotube sheets are 250 times stronger than steel and 10 times lighter; they are also stretchable. Many magazines quoted in 2008 James Hone, Columbia University saying, “It would take an elephant, balanced on a pencil, to break through a sheet of graphene the thickness of Saran Wrap [cling film].” As claimed by Richard Van Noorden (2011), “According to the Nobel Prize committee, a hypothetical one-metre-square hammock of perfect graphene could support a four-kilogram cat – the hammock would weigh 0.77 milligrams, less than a cat’s whisker, and would be virtually invisible.”
The cylindrical structures of carbon nanotubes have exceptional electrical and thermal properties along with superior mechanical strength. The fabrication of carbon nanotubes serves a variety of applications. Carbon nanotubes are used in the production of memory chips, batteries, and many consumer products such as tennis rackets, badminton rackets, bicycles, compounds to manufacture cars and airplanes, and so forth. Carbon nanotubes distributed on small cement grains provide superior strength of concrete. New methods for producing carbon nanotubes are capable of reducing their price.
The nanoscale world: metric measures
The developments in nanoscale and molecular-scale technologies allow researching the nanoscale objects: liquid crystals, soft matter, nanoshells, and carbon nanotubes. In order to discuss soft matter and liquid crystals we need to discuss the metric measurements and some metric prefixes (prefixes for other multiples, such as 104, 105, 10-4, and 10-5), as well as metric conversions.
– A macro-scale comprises visible objects with sizes of a millimeter or more
(1 millimeter, 1 mm = 1/1,000 meter – 1×10-3 m)
For example, a human hair is about 10-4 m wide (about 100,000 nanometers wide).
– A micro-scale relates to objects with sizes about a micrometer to about 1/10 of a millimeter
(1 micrometer, 1 µm = 1/1,000,000, one millionth of a meter – 1×10-6 m)
For example, red blood cells may have a size of several µm; bacteria may be about 1 µm large.
– A nano-scale encompasses a range of subjects from about a nanometer to about 1/10 of micrometer
(1 nanometer, 1 nm = 1/1,000,000,000, one billionth of meter – 1×10-9 m).
For example, a virus is about 10-7 m; a DNA is about 10-8 m; molecular structures are about 10-9 m;
– A pico-scale is a size range of single atoms, both found in nature (and represented in the periodic table) and atoms man-made in accelerators for nuclear technology
(1 ångström or angstrom (symbol Å) = 1 x 10-10 meters).
For example, a helium atom has a diameter of about 0.1 nm.
One nano is 10-9 meter; that means one-billionth of a meter. That means the size of a nanometer is to the size of a meter like a marble compared to the size of Earth. Many familiar objects are millions of nanometers big: a human nail on a little finger is about ten million nanometers across and a human hair is about 80,000 nanometers wide. A dollar bill is 100,000 nanometers thick. A small reptile gecko can cling upside down to the pane of glass because it has millions of microhairs on its toes; each hair is split into hundreds of tips 200 nanometers wide, which form nanohairs on its microhairs).
Tools for examining nanostructures
Developments in technology, especially advances in microscopy and spectroscopy (recording how matter interacts with or emits electromagnetic radiation) provide opportunities for discoveries in a nano scale, which in turn cause that new epistemologies evolve allowing us to see the world in a changed way. Tools are needed to determine the size, shape, and physical structure, to know the composition of chemical elements and the physical and chemical properties. Generally, tools are based on electron beams; they produce images using electrons, inform about composition using x-ray photons, or they are the scanning probe tools. Beams of electrons can be transmitted through the specimen (which is used in transmission electron microscopy, TEM or field emission transmission electron microscopy, or FE-TEM in case of quantum mechanical tunneling), bounced back (backscattered, as used in scanning electron microscopy, SEM (the 1986 Nobel Prize in Physics for Gerd Binnig and Heinrich Rohrer), or FE-SEM in case of quantum mechanical tunneling), or knocked back from an atom and come as the secondary electrons.
Scientists are working on imaging (with the use of computed tomography such as soft x-ray tomography, and also cryogenic light microscopy) and visualization of small particles in cells in order to know how nanoparticles interact, undergo changes, and deliver drugs into the intended inside targets or only to a cell membrane (Challenges, 2012: Gerry McDermott). Researchers work on obtaining temporal resolution to monitor ongoing processes. Tools that enable obtaining atomic resolution images that clearly delineate the atoms in polymer-capped platinum and palladium nanoparticles include neutron- and x-ray-based microscopy and analytic electron microscopy (Challenges, 2012: Doug Ray). They reveal atomic structure and speciation of elements. It is possible to count atoms, see lattices and clusters, to correlate particle size with atom count in various types of particle morphologies, and thus understand structural defects and disorders. Combined data from microscopy and spectroscopy provide information how bond distances change with temperature: they contract as temperature rises when particle diameter riches sizes as small as 1 nanometer (Challenges, 2012: Ralph Nuzzo). Nanoscale-sized catalysts and catalytic technologies are important in refineries, automobile catalytic converters, and in developing catalytic fuel cells for powering laptops. Catalyst designers work on gold nanoparticles on a titanium dioxide that catalyze oxidation of (CO) carbon monoxide. They become able to control the features of catalysts by design (Challenges, 2012: Abhaya Datye).