C3.8 Fullerenes and Graphene

A free GCSE Combined Science: Trilogy lesson for AQA (8464) from OBA School: graphene, buckminsterfullerene and carbon nanotubes: their structures, properties and uses. Watch the video, read the explanation and worked examples, then try the revision questions. You can work through the full lesson, with every video, practice quizzes and printable worksheets with mark schemes, in our free online course.

What you will learn

• Describe the structure of graphene and explain its properties
• Describe fullerenes as hollow molecules of carbon, including buckminsterfullerene, C₆₀
• Describe carbon nanotubes and calculate a length-to-diameter ratio
• Link the properties of graphene, fullerenes and nanotubes to their uses

Key words

• Graphene: A single layer of graphite, one atom thick, made of carbon atoms in hexagonal rings.
• Fullerene: A molecule of carbon atoms with a hollow shape (a cage or tube), based on hexagonal rings, sometimes with rings of 5 or 7 atoms.
• Buckminster- fullerene: The first fullerene discovered: C₆₀, a hollow sphere-shaped molecule.
• Carbon nanotube: A cylindrical fullerene with a very high length-to-diameter ratio.

Three more forms of carbon

Diamond and graphite are not the only forms of pure carbon. Scientists have made graphene and a family of hollow molecules called fullerenes. In all of them, each carbon atom forms 3 covalent bonds, like in graphite.

The first fullerene was made by chance in 1985. Tests showed that all 60 carbon atoms in the new molecule were identical, with no “end” atoms, so chemists suggested a closed cage of hexagons and pentagons. Since then, fullerenes shaped like rugby balls, tubes and even balls inside balls have been made.

Graphene

Graphene is a single layer of graphite. It is a giant covalent structure only one atom thick.

• very strong for its mass; Reason strong covalent bonds between every atom in the layer; Use composites, e.g. light, strong materials
• conducts electricity and heat very well; Reason each carbon has one delocalised electron that can move across the layer; Use electronics, e.g. flexible screens, faster computer chips and sensors
• almost transparent and very light; Reason it is only one atom thick; Use touchscreens, solar cells

Worked example: how many layers in a graphite flake?

The layers in graphite are about 0.34 nm apart. A flake of graphite is 0.102 mm thick.
0.102 mm = 0.102 × 10⁶ nm = 102 000 nm
Number of layers = 102 000 ÷ 0.34 = 300 000

Answer: about 300 000 layers of graphene

Fullerenes and buckminsterfullerene

Fullerenes are molecules of carbon atoms with hollow shapes. Their structure is based on hexagonal rings, but they can also have rings of 5 (or 7) carbon atoms, which let the sheet curve round.

The first fullerene discovered was buckminsterfullerene, C₆₀. It is a hollow sphere made of 20 hexagons and 12 pentagons, rather like a football.

• C₆₀ is a simple molecule, so it has weak intermolecular forces. It has a much lower melting point than diamond or graphite, and it is slippery.
• Uses: as lubricants; as catalysts (large surface area); to deliver drugs into the body, because other molecules can be carried inside the hollow cage.

Carbon nanotubes

Carbon nanotubes are cylindrical fullerenes: like a sheet of graphene rolled into a tube. They are only a few nanometres wide but can be many micrometres long, so they have a very high length-to-diameter ratio.

• very high tensile strength (hard to snap) → used to reinforce materials, e.g. sports equipment like tennis rackets and bike frames
• conduct electricity and heat → used in electronics and nanotechnology

Worked example: length-to-diameter ratio

A nanotube has a diameter of 2.5 nm and a length of 4.0 µm.
Use the same units: 4.0 µm = 4.0 × 1000 nm = 4000 nm
ratio = length ÷ diameter = 4000 ÷ 2.5 = 1600

Answer: 1600 (no units: it is a ratio)

Maths: 1 µm = 1000 nm = 10⁻⁶ m · 1 nm = 10⁻⁹ m. Always change both lengths into the same unit before dividing.

Common mistakes

• Saying fullerenes are giant structures. Fullerenes are molecules; graphene is a giant covalent layer.
• Saying C₆₀ has a very high melting point like diamond. Only weak intermolecular forces are overcome when it melts or sublimes.
• Forgetting to convert µm to nm before working out a length-to-diameter ratio.
• Saying graphene conducts because of ions. It has delocalised electrons, like graphite.

Revision questions

Try these, then check your answers below each one.

Question 1. Why does buckminsterfullerene, C₆₀, have a much lower melting point than diamond? (Choose from: It is made of molecules with weak intermolecular forces between them, Its covalent bonds are weak, It contains delocalised electrons, It is made of ions.)

Answer: It is made of molecules with weak intermolecular forces between them

Working: C₆₀ is a simple molecule. Melting only overcomes the weak forces between molecules; no covalent bonds are broken.

Question 2. True or false? Graphene is a single layer of graphite, one atom thick.

Answer: True

Working: True. Graphene is one layer of carbon atoms in hexagonal rings.

Question 3. Give the molecular formula of buckminsterfullerene.

Answer: C₆₀

Working: C₆₀ – a hollow sphere of 60 carbon atoms.

Related lessons

• Previous lesson: C3.7 Giant Covalent Structures
• Next lesson: C3.9–10 Bonding in Metals and Giant Metallic Structures
• In this chapter: C3.1 States of Matter
• In this chapter: C3.2 Atoms Into Ions
• In this chapter: C3.3 Ionic Bonding

Continue in the full course

This lesson is section C3.8 (AGCSC2008) of our free GCSE Combined Science course for AQA. In the full course you get every video for this section, a self-marking practice quiz, a printable worksheet with a mark scheme, chapter tests, and your progress saved. Go to the full GCSE Combined Science course.