commercial nanoparticles are the smallest particles of matter with size less than 100 nm. They have unique physical and chemical properties due to their small size.
They may be spherical, elliptical or plate-like, and the shape can influence the performance of the material. They can be made from inorganic or polymeric materials. They often have a core particle which is protected by several monolayers of inert material, such as silica. Then they can be functionalised by attaching a linear linker molecule that has reactive groups on both ends to allow it to bind other moieties, such as biocompatibles (dextran or antibodies) or fluorescent dyes, or polymeric materials.
Controlling the size and shape of the NPs makes it possible to create new types of materials. For example, nano-titanium dioxide is used in paint to make it self-cleaning – a coating that repels water and dirt, just like the water beads that form on waterproof clothing. The reactivity of noble metals NPs is also exploited in catalytic processes to destruct organic pollutants.
NPs are able to penetrate into cells, where they have an effect on molecular processes inside the cell. They can then be targeted by drugs or used as probes to deliver chemicals to tumours and other cellular structures. The healthcare sector is currently working on many such applications.
Most of these applications rely on quantum size effects – for example, gold nanoparticles have dramatically different malleability and ductility than bulk copper. However, it should be borne in mind that the value of the final product does not always reflect the value of the nanoparticles within it. A Mercedes car that features a scratchfree paint finish with nano-particles, for example, contributes only a tiny fraction of its price to the so-called “nanotechnology market”.