Nanoparticles and nanotechnology
Chemistry · Key Stage 3 · The School
Just how small
A NANOPARTICLE is between about 1 and 100 nanometres across. A nanometre is one billionth of a metre. Think of it this way: a nanoparticle is to a football roughly as a football is to the whole Earth. At this size, a particle holds just a few hundred to a few thousand atoms. That is nothing like the huge numbers in an everyday object.
Why surface area matters so much here
Shrink a particle, and its SURFACE-AREA-TO-VOLUME RATIO shoots up. That is because surface area shrinks more slowly than volume does, as size drops. At nanoparticle size, a huge share of all the atoms sit right on the surface. They are exposed there, able to react. They are not buried deep inside, cut off from everything around them.
What that changes
With so many atoms on the surface, nanoparticles can react far more easily than the same substance in bulk. They can show different colours too, and different strength or electrical behaviour. Gold nanoparticles are not even gold-coloured. Depending on their exact size, they can look red or purple instead.
Some sports clothing and wound dressings have silver nanoparticles woven in. Their huge surface area makes them very good at killing bacteria. That is a real, useful benefit, backed by real evidence. But the same trait raises a real question too. Most particles this size cannot get inside a human cell. A nanoparticle sometimes can. Could that present a risk nobody fully understands yet? Scientists are still actively researching this. It is not settled either way. The honest answer needs more study, not one confident claim right now.