Nanotechnologies: 4. How Are Nanoparticles Formed?

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4. How are nanoparticles formed?

• 4.1 How do nanoparticles form in the liquid phase?
• 4.2 How do nanoparticles form in the gas phase?
• 4.3 What are the sources of airborne nanoparticles?

Free nanoparticles are formed through either the breaking down of larger particles or by controlled assembly processes.

Natural phenomena and many human industrial and domestic activities, such as cooking, manufacturing or road and air transport release nanoparticles into the atmosphere.

In recent years, nanoparticles intentionally engineered for advanced technologies and consumer products have become a new source of exposure. At present it is not clear just how significantly human exposure to these engineered nanoparticles has increased, be it in the workplace, or through the use of nanotechnology-based products.

There are two approaches for the manufacturing of nanomaterials:

• The “top-down” approach involves the breaking down of large pieces of material to generate the required nanostructures from them. This method is particularly suitable for making interconnected and integrated structures such as in electronic circuitry.
• In the “bottom-up” approach, single atoms and molecules are assembled into larger nanostructures. This is a very powerful method of creating identical structures with atomic precision, although to date, the man-made materials generated in this way are still much simpler than nature’s complex structures.

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