# Nanoparticles

are structures, 1-100 nanometres (nm) in size, that usually contain only a few hundred . This means that nanoparticles are around 100 times larger than atoms and simple .

1 nm is 1 x 10-9 m (or 0.000,000,001 m).

Buckminsterfullerene, with the formula C60, is a nanoparticle:

## Small size

Some of the of nanoparticles depend on their very small size.

### Worked example

A zinc oxide nanoparticle has a diameter of 32 nm. The diameter of a zinc atom is 0.28 nm. Estimate how many times larger the nanoparticle is compared to a zinc atom.

To help with this estimate, round each number to 1 :

30 nm and 0.3 nm

Number of times larger ≈

The nanoparticle is about 100 times larger than the zinc atom.

The symbol ≈ is used to show that the answer is approximate.

## Surface area to volume ratios

Some of the properties of nanoparticles depend on their large to ratios. For solid substances, the smaller its , the greater the surface area to volume ratio.

### Worked example

A cube-shaped nanoparticle has sides of 10 nm. Calculate its surface area to volume ratio.

Surface area = 6 × 10 × 10 = 600 nm2 (remember that a cube has six sides)

Volume = 10 × 10 × 10 = 1000 nm3

Surface area to volume ratio =

= 0.6

Question

A cube-shaped nanoparticle has sides of 1 nm. Calculate its surface area to volume ratio.

Surface area = 6 × 1 × 1 = 6 nm2

Volume = 1 × 1 × 1 = 1 nm3

Surface area to volume ratio =

= 6