Nanoparticles (Oxford AQA IGCSE Chemistry)

Nanoparticles

• Nanoscience refers to structures that are 1–100 nm in size, of the order of a few hundred atoms.

• Particles can be placed into one of three categories according to their diameter:

  • Coarse particles (also called particulate-matter or dust)

  • Fine particles

  • Nanoparticles

• Nanoparticles are between 1 and 100 nanometres in size and usually contain only a few hundred atoms

  Atoms and simple molecules are around 100 times larger than this

  Nanoparticles are much smaller than fine particles which have diameters of between 100 and 2500 nm

  The research into the production and application of nanoparticles is called nanoscience

Surface to Volume Ratio

• One of the most interesting features of nanoparticles is their very high surface area to volume ratio

• As particles decrease in size, their surface area increases in relation to their volume

• As the side of a cube decreases by a factor of 10, the surface area to volume ratio increases by a factor of 10

• This is why nanoparticles may have properties different from those for the same materials in bulk

• It may also mean that smaller quantities are needed to be effective than for materials with normal particle sizes

• Fullerenes (nanoparticles made of carbon) behave very differently to larger compounds of carbon like diamond and graphite

• The surface area to volume ratio is an important feature in catalysis and surface chemistry

  • The higher the ratio then the more surface area is available for reaction, hence the better the catalyst

Applications of Nanoparticles

• The main industrial application of nanoparticles is in catalysis due to their high surface area to volume ratios

• Titanium dioxide is a good example of how the same chemical has different properties in bulk and nanoparticle form

• Titanium dioxide in nanoparticle form is used in sunscreens as it blocks UV light but leaves no white marks on the skin while also providing better coverage than other suncreams

• The same chemical in bulk form is used as a white pigment in paints

• Fullerenes are used in medicine and drug design as they are more easily absorbed than other particles and can deliver drugs to target areas more effectively

• Fullerenes are also used in electronic circuitry and as coatings for artificial limbs and joints

• Nanoparticles of silver are sprayed onto the fibres of medical clothing and surgical masks which gives them the flexibility of a material but with the added benefit of the antibacterial properties of silver metal