📖 In-Depth Theory
What Are Nanoparticles?
NANOPARTICLES are particles with dimensions in the range of 1 to 100 NANOMETRES (nm).
1 nm = 1 × 10⁻⁹ m
Nanoparticles contain a few hundred to a few thousand atoms — much smaller than bulk materials, but larger than individual atoms or molecules.
At this tiny scale, materials can have VERY DIFFERENT properties compared to the same material in bulk (large) form. For example:
Gold in bulk: yellow, does not react with most chemicals, melts at 1064°C.
Gold nanoparticles: red/purple colour, much higher reactivity, much lower melting point.
This is because nanoparticles have an enormous SURFACE AREA TO VOLUME RATIO compared to bulk material — a much greater proportion of atoms are on the surface and available for reactions.
Larger surface area → higher reactivity, faster catalyst action, different optical properties.
Carbon Nanostructures — Graphene and Fullerenes
GRAPHENE:
A SINGLE LAYER of graphite — a flat sheet of carbon atoms arranged in a hexagonal lattice, just ONE ATOM THICK.
Properties:
Extremely strong (one of the strongest materials ever tested).
Very lightweight — just one atom thick.
Excellent electrical conductor — delocalised electrons (as in graphite).
Almost transparent.
Potential uses: flexible electronics, touchscreens, ultralight composite materials, medical sensors.
FULLERENES:
Carbon molecules where atoms form hollow SPHERES, TUBES or other shapes.
BUCKMINSTERFULLERENE (C₆₀) — also called 'buckyballs':
60 carbon atoms arranged in a sphere (like a football — hexagons and pentagons).
Hollow structure.
Fairly stable, can enclose other atoms or molecules inside the cage.
Uses: drug delivery (molecules placed inside for targeted medicine), lubricants, catalysis.
CARBON NANOTUBES:
Rolled-up sheets of graphene forming hollow cylindrical tubes.
Very strong and stiff along the tube axis.
Excellent electrical conductors (delocalised electrons).
Uses: reinforcing composite materials, electronics, future nanotechnology.
Uses and Risks of Nanoparticles
USES OF NANOPARTICLES:
SUNSCREEN: Titanium dioxide (TiO₂) nanoparticles — transparent (unlike bulk TiO₂ which is white) but still absorb UV radiation effectively.
ANTIBACTERIAL products: Silver nanoparticles — high surface area → high reactivity against bacteria. Used in wound dressings, socks, food packaging.
CATALYSIS: High surface area makes nanoparticles extremely effective catalysts.
DRUG DELIVERY: Nanoparticles can carry drugs directly to target cells (e.g. tumour cells).
COATINGS: Self-cleaning glass, water-repelling fabrics.
ELECTRONICS: Used in transistors, sensors, LEDs.
POTENTIAL RISKS:
Nanoparticles are so small they can:
Pass through cell membranes — may cause unknown biological effects.
Be inhaled into the lungs and bypass normal defence mechanisms.
Persist in the environment — may accumulate in food chains.
Interact unexpectedly with biological systems — long-term effects not fully understood.
The same properties that make nanoparticles useful (small size, high reactivity, ability to penetrate membranes) also make them potentially hazardous.
More research is needed to fully understand the health and environmental impacts — this is an area of active scientific investigation.
⚠️ Common Mistake
Nanoparticles are NOT the same as atoms or small molecules — they contain hundreds to thousands of atoms. The key reason nanoparticles have different properties is their enormous SURFACE AREA TO VOLUME RATIO — a much greater fraction of their atoms are on the surface, making them much more reactive than the same material in bulk form.