Sizes of particles
- Nanoscience is the study of structures 1–100 nm in size, of the order of a few hundred atoms. 1 nm = 1 × 10⁻⁹ m.
- Nanoparticles are smaller than fine particles (PM2.5), which have diameters between 100 and 2500 nm (1 × 10⁻⁷ m to 2.5 × 10⁻⁶ m).
- Coarse particles (PM10), often called dust, have diameters between 1 × 10⁻⁵ m and 2.5 × 10⁻⁶ m.
Surface area to volume ratio
- As the side of a cube decreases by a factor of 10, its surface area to volume ratio increases by a factor of 10.
- Nanoparticles have a very high surface area to volume ratio.
- This means they can have different properties from the same material in bulk, and smaller quantities are needed to be effective.
Uses
- Medicine: delivering drugs to specific cells in the body.
- Electronics, cosmetics and sunscreens (which give better skin coverage), deodorants, and catalysts (a large surface area speeds up reactions).
- Silver nanoparticles are antibacterial and used in some fabrics and wound dressings.
Risks
- Nanoparticles may be absorbed into the body or pass into cells, and their long-term effects on health and the environment are not yet fully known.
- More research is needed, and some people think products containing nanoparticles should be clearly labelled.
Key terms
- Nanoparticle
- A particle between 1 nm and 100 nm in size.
- Nanometre
- One billionth of a metre (1 × 10⁻⁹ m).
- Nanoscience
- The study of structures between 1 nm and 100 nm in size.
- Fine particles
- Particles 100–2500 nm across (PM2.5).
- Coarse particles
- Particles 2500 nm to 10 000 nm across (PM10), often called dust.
- Surface area to volume ratio
- The surface area of an object divided by its volume.
- Bulk material
- A large amount of a material, not in nanoparticle form.