Size of Nanoparticles

Specification Point 9.35C:
  • Compare the size of nanoparticles with the sizes of atoms and molecules
  • Nanoparticles are between 1 and 100 nanometres (nm) in size and usually contain only a few hundred atoms.
  • One nanometre is one billionth of a metre, so 1 nm = 1 x 10-9 m.
  • Atoms and simple molecules are around 100 times smaller than this.
  • Nanoparticles are much smaller than fine particles which have diameters of between 100 and 2500 nm.

Nanoparticle Scale, Edexcel GCSE Chemistry

Diagram showing the size of nanoparticles relative to other objects and substances

Uses

Specification Point 9.36C:
  • Describe how the properties of nanoparticulate materials are related to their uses including surface area to volume ratio of the particles they contain, including sunscreens
  • Nanoparticles have different properties than the chemicals from which they are made.
  • Fullerenes for example, which are nanoparticles made of carbon, behave very differently to larger compounds of carbon.
  • One of the most interesting features of nanoparticles is their very high surface area to volume ratios.
  • As particles decrease in size, their surface area increases in relation to their volume.
  • 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.
  • The ratio is calculated using the following formula:

Surface Area - Volume Ratio, Edexcel GCSE Chemistry

Example

A scientist develops two nanoparticles of different shapes and sizes. One is cube shaped and has sides of 8 nm and the other is spherically shaped and has a diameter of 6 nm. Determine which nanoparticle would make the most effective catalyst.

For the Cube

A cube has six faces, so the surface area = 6 x 8 x 8 = 384 nm2

Volume = 8 x 8 x 8 = 512 nm3

Surface area to volume ratio = 384 ÷ 512 = 0.75

For the Sphere

Surface area = 4πr2 = (4)(3.14)(32) = 113.04 nm2

Volume sphere eq

Surface area to volume ratio = 113.04 ÷ 112.75 = 1.00

The sphere has a higher surface area to volume ratio than the cube hence it would be the more effective catalyst.

  • 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.
  • The same chemical in bulk form is used as a white pigment in paints.
  • Fullerenes are used in the 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.

Risks

Specification Point 9.37C:
  • Explain the possible risks associated with some nanoparticulate materials
  • The use of nanoparticles in science is in its early stages so there are still a lot of unknown factors and potential risks.
  • In particular there is a lack of understanding on how they may affect health.
  • Although there haven’t been any serious shortterm side effects, there could be longterm side effects which we haven’t detected yet as they haven’t been in use long enough.
  • Even a small amount of toxicity in a particular nanoparticle would be multiplied due to the high surface area to volume ratio.
  • This coupled with the fact that they are not easily disposed of by the body are a cause for caution in the medical application of nanoparticles.

Edexcel GCSE Chemistry Notes

Share with friends

Want to aim for a Level 9?

See if you’ve got what it takes. Test yourself with our topic questions.

Morgan Curtin Chemistry

Author: Morgan

Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.