chem nanoparticles

What are fullerenes?

Allotropes of carbon made of sp² hybridised atoms forming covalent structures with delocalised electrons.

What type of bonding is in fullerenes?

Covalent bonding with delocalised electrons.

What is sp² hybridisation?

A carbon forms 3 sigma bonds and has 1 electron in a p orbital for delocalisation.

Describe the structure of buckminsterfullerene (C60).

A spherical molecule made of 60 carbon atoms arranged in 12 pentagons and 20 hexagons.

What type of structure is buckminsterfullerene?

Simple molecular (discrete molecules).

What holds buckminsterfullerene molecules together?

Weak London dispersion forces.

Why does buckminsterfullerene have a low melting point?

Because only weak intermolecular forces exist between molecules.

What are delocalised electrons in C60?

Electrons spread over the whole molecule, not fixed between two atoms.

Why is C60 a poor conductor?

Electrons are delocalised only within each molecule, not between molecules.

What are sigma bonds?

Strong covalent bonds formed by head-on overlap of orbitals along the bond axis.

What is the role of sigma bonds in C60?

They form the strong framework of the molecule.

Describe the structure of carbon nanotubes.

Cylindrical tubes of carbon atoms arranged in hexagons (rolled graphene).

What type of structure are nanotubes?

Giant covalent structure.

Why are nanotubes very strong?

Strong covalent bonds extend throughout the structure.

Why do nanotubes conduct electricity?

Delocalised electrons move along the tube.

Compare buckminsterfullerene and nanotubes (structure).

C60 is simple molecular; nanotubes are giant covalent.

Compare buckminsterfullerene and nanotubes (properties).

C60 is soft and low melting; nanotubes are strong and high melting.

What is zinc oxide made of?

Zn²⁺ and O²⁻ ions.

What type of bonding is in ZnO?

Mainly ionic with some covalent character.

Why is ZnO slightly covalent?

Electrons are partly shared due to polarisation and moderate electronegativity difference.

What is the lattice structure of ZnO?

Giant ionic lattice (wurtzite structure).

Describe coordination in ZnO.

Each ion is surrounded by 4 oppositely charged ions (tetrahedral).

Does bonding change in nanoscale ZnO?

No, bonding stays the same but surface properties change.

What is surface area to volume ratio?

The amount of surface area compared to volume.

Why do nanoparticles have higher SA:V?

Smaller size increases proportion of surface atoms.

Why is high SA:V important?

More atoms are exposed for reactions or interactions.

What is a band gap?

The energy difference between valence and conduction bands.

What is a wide band gap?

A large energy gap requiring high-energy radiation (UV) to excite electrons.

Why is ZnO good for sunscreen?

It absorbs UV but not visible light due to its wide band gap.

Why are ZnO nanoparticles transparent?

They do not scatter visible light strongly due to small size.

Why is non-nano ZnO white?

Larger particles scatter visible light.

Advantages of nanoscale ZnO

Transparent, better UV absorption, spreads easily.

Disadvantages of nanoscale ZnO

More reactive, possible ROS formation, safety concerns.

Advantages of non-nanoscale ZnO

Stable, less reactive, well-established safety.

Disadvantages of non-nanoscale ZnO

White appearance, less cosmetic appeal.

What evidence shows ZnO nanoparticles are safe?

Studies show they do not penetrate beyond outer skin layer.

Do ZnO nanoparticles enter bloodstream?

Only extremely small amounts (

Overall safety conclusion for ZnO nanoparticles

Considered safe on intact skin by scientific consensus.

What is a catalyst?

A substance that increases reaction rate without being used up.

Where do catalytic reactions occur?

On the surface of the catalyst.

Why are nanocatalysts more effective (1)?

Higher surface area to volume ratio.

Why are nanocatalysts more effective (2)?

More active sites for reactions.

Why are nanocatalysts more effective (3)?

Surface atoms are more reactive (low coordination).

Why are nanocatalysts more effective (4)?

Shorter diffusion distances.

Why do surface atoms have fewer neighbours?

They are on the outside and not surrounded on all sides.

What does low coordination mean?

Atoms have fewer neighbouring atoms.

Why does low coordination increase reactivity?

Atoms are less stable and more likely to react.

Function of platinum nanoparticles

Provide surface for redox reactions converting harmful gases (e.g. CO to CO₂).

Function of gold nanoparticles

Provide reactive surface to catalyse reactions like CO oxidation at low temperatures.

Why is gold reactive as nanoparticles but not bulk?

Higher surface atoms and lower coordination increase reactivity.

What is adsorption in catalysis?

Reactants attach to catalyst surface.

How do catalysts lower activation energy?

They weaken bonds and allow easier reaction pathways.