Imagine being able to see the microscopic structure of a material, and noticing that it is composed of many periodic patterns on the order of 100 nm or less.
The shape and size properties of those tiny patterns can affect the physical properties of the material that they are part of. For example, solutions of gold nanoparticles that differ only in their size and shape properties at the nanoscale interact with light differently. The result is different colors.
In “nanomaterials,” the size and shape of the very small domains that compose the bulk material affect its properties. The dependence of the physical property (such as color or conductivity) on the size and shape of the nanoscale domains is often a result of surfaceand interface interactions.
Materials that are comprised of many small structures often have a very large surface area. The reason is that the surface areas of the many small structures together contribute to a very large surface area of the bulk material. For example, if a piece of material the size of a shoe box were to be split up into 2 nm spheres, these spheres would contribute to a surface area of the shoe box that correspond to the area of 10,000 football fields. It is not surprising that when the surface area is so large, the physical properties are dominated by surface interactions.
Nanomaterials come in many varieties. A few examples of materials that exhibit interesting properties on the nanoscale are carbon nanotubes, inorganic nanowires, dendrimers, nanoparticles, graphene, and quantum dots.
A carbon nanotube (CNT) is a tubular form of carbon with a diameter as small as 0.4 nm and length from a few nanometers up to a millimeter.
Graphene is a one atom thick, two dimensional material which consists of carbon atoms densely packed into a honeycomb-like crystal lattice.
Inorganic nanowires may have diameters of 1-50 nm and any desirable length, perhaps up to a micrometer. They offer interesting electronic, optical and other properties, and may be used in the future to link tiny components into small scale circuits.
Whereas typical polymers run like linear chains, dendrimers are tree-like polymers. They branch out from a central core, exhibiting a dense surface surrounding a relatively hollow core. They are a series of chemical shells built on a small core molecule.
Nanoparticles (sized between 1 and 100 nanometers) are considered a bridge between bulk materials and atomic or molecular structures.
AFM-deposited Cr nanodot. James E. Morris & Hui She (2004)