Nanomaterials
Imagine being able to see the microscopic structure of a material and noticing that it is composed of many periodic patterns of atoms or molecules on the order of 100 nm or less.
The shape and size of those tiny patterns can affect the physical properties of the material that contains them. For example, gold nanoparticles that differ only in their size and shape interact with light differently than do larger bits of gold. The result is that gold nanoparticles display different colors from the one we normally associate with gold.
In “nanomaterials,” the size and shape of the very small domains that compose the bulk material affect its properties. The physical properties (such as color or electrical conductivity) depend on the size and shape of the nanoscale domains are often a result of surface and interface interactions between the domains and the surrounding media.
Image Credit: NASA Ames Center for Nanotechnology
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 diameter 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.
Carbon Nanotubes
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
Graphene is a one atom thick, two dimensional material which consists of carbon atoms densely packed into a honeycomb-like crystal lattice.
Inorganic Nanowires
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.
Dendrimers
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
Nanoparticles (sized between 1 and 100 nanometers) are considered a bridge between bulk materials and atomic or molecular structures.
Quantum Dots
AFM-deposited Cr nanodot. James E. Morris & Hui She (2004)
Pattern of Hexagon nano geometry 6 sided polygon structure like allotropes of carbon nanotube. Image credit: Quality Stock Arts/bigstock.com
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Nanoscale Properties