Nanoparticles
nanoscienceThe study of structures between 1 and 100 nanometres (nm) in size. is the study of structures that are between 1 and 100 nanometres (nm) in size. Most nanoparticlesTiny particles which are between 1 and 100 nanometres (nm) in size. are made up of a few hundred atomThe smallest part of an element that can exist..
Learn more on nanoparticles in this podcast.
Listen to the full series on 大象传媒 Sounds.
Comparing sizes
The table shows the sizes of nanoparticles compared to other types of particles.
| Particle | Diameter |
| Atoms and small molecules | 0.1 nm |
| Nanoparticles | 1 to 100 nm |
| Fine particles (also called particulate matter - PM2.5) | 100 to 2,500 nm |
| Coarse particles (PM10, or dust) | 2500 to 10,000 nm |
| Thickness of paper | 100,000 nm |
| Particle | Atoms and small molecules |
|---|---|
| Diameter | 0.1 nm |
| Particle | Nanoparticles |
|---|---|
| Diameter | 1 to 100 nm |
| Particle | Fine particles (also called particulate matter - PM2.5) |
|---|---|
| Diameter | 100 to 2,500 nm |
| Particle | Coarse particles (PM10, or dust) |
|---|---|
| Diameter | 2500 to 10,000 nm |
| Particle | Thickness of paper |
|---|---|
| Diameter | 100,000 nm |
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.
Worked example answer
Round each number to 1 significant figure:
30 nm and 0.3 nm
Number of times larger 鈮 \(\frac{30}{0.3}\) = 100
The nanoparticle is about 100 times larger than the zinc atom. This is an example of an order of magnitudeAn order of magnitude estimate approximates a number to the nearest power of ten. calculation.
Surface area to volume ratios
Nanoparticles have very large surface areaThe total area of all sides on a 3D shape. to volumeThe volume of a three-dimensional shape is a measure of the amount of space or capacity it occupies, eg an average can of fizzy drink has a volume of 330 ml. ratios compared to the same material in bulk, as powders, lumps or sheets.
For a solid, the smaller its particles, the greater the surface area to volume ratio. If the length of the side of a cube gets 10 times smaller, the surface area to volume ratio gets 10 times bigger.
Worked example
A cube-shaped nanoparticle has sides of 10 nm. Calculate its surface area to volume ratio.
Worked example answer
Surface area = 6 脳 10 脳 10 = 600 nm2 (remember that a cube has six sides)
Volume = 10 脳 10 脳 10 = 1000 nm3
Surface area to volume ratio = \(\frac{600}{1000}\) = 0.6