Graphene and fullerenes (AQA GCSE Chemistry Combined Science): Revision Notes
Graphene and fullerenes
Carbon can form many different structures beyond the simple covalent compounds we usually think about. Two important forms are graphene and fullerenes, which have unique properties that make them very useful in modern technology.
What is graphene?
Graphene is an incredibly thin sheet of carbon atoms. Think of it as taking graphite (like in a pencil) and peeling off just one single layer. This layer is only one atom thick, making it the thinnest material possible.
Graphene is literally the thinnest material that can exist - being just one atom thick means you could stack 3 million layers and they would still be thinner than a human hair!
Structure of graphene
The structure of graphene gives it its remarkable properties:
- Each carbon atom connects to three other carbon atoms through strong covalent bonds
- The atoms arrange themselves in a flat honeycomb pattern
- The structure forms hexagonal rings across the entire sheet
- Even though it's only one atom thick, the covalent bonds make it incredibly strong
Key properties of graphene
Electrical properties:
- Graphene conducts electricity because it has delocalised electrons
- These electrons can move freely across the sheet
- This makes graphene behave like a semiconductor
The delocalised electrons in graphene can move at speeds close to the speed of light, making it one of the fastest conducting materials known to science.
Physical properties:
- Extremely strong due to the covalent bonding
- Very lightweight because it's so thin
- Flexible and can bend without breaking
Uses of graphene
Electronics: Because graphene conducts electricity well, it's perfect for making electronic devices like computer chips and touchscreens.
Strong materials: Graphene can be mixed with other materials to create composites. These composites are both strong and light, making them ideal for sports equipment or aircraft parts.
What are fullerenes?
Fullerenes are hollow structures made entirely of carbon atoms. Unlike graphene's flat sheet, fullerenes form three-dimensional shapes that look like cages or balls.
Structure of fullerenes
- Carbon atoms bond together to form hollow shapes
- Most commonly form spheres, but can also make other shapes
- The structure is based on carbon hexagons, similar to graphene
- Can also include five-carbon and seven-carbon rings
- The most famous fullerene is called buckminsterfullerene (), which contains 60 carbon atoms in a ball shape
Buckminsterfullerene () was the first fullerene discovered and earned its discoverers the Nobel Prize in Chemistry. It's named after architect Buckminster Fuller because its structure resembles his geodesic dome designs.
Carbon nanotubes - a special type of fullerene
Carbon nanotubes are cylindrical fullerenes that look like tiny tubes. These structures have some amazing properties:
Carbon nanotubes can be thought of as graphene sheets rolled into tubes, combining the best properties of both flat and curved carbon structures.
- Shape: Very long compared to how wide they are (like extremely thin straws)
- Strength: Have very high tensile strength, meaning they're hard to pull apart
- Conductivity: Excellent at conducting both electricity and heat
Uses of fullerenes and nanotubes
Medicine: Fullerenes can carry drugs inside their hollow structure and deliver them to specific parts of the body.
Lubricants: The round shape of fullerenes makes them roll easily, so they work well as lubricants in machinery.
Catalysts: Fullerenes can provide a surface for chemical reactions to happen more easily.
Electronics: Like graphene, carbon nanotubes conduct electricity well and are used in electronic devices.
Advanced materials: Nanotubes can be added to materials like tennis racket frames to make them stronger without adding much weight.
Practical applications
Real-World Application: Water Purification
Graphene's ability to let small molecules through (like water) but block larger ones (like salt) makes it useful for water purification systems. This happens because the holes in graphene's structure are just the right size - water molecules can pass through, but salt ions cannot.
This selective permeability could revolutionise desalination technology, making clean drinking water more accessible worldwide.
Real-World Application: Sports Equipment
Carbon nanotubes are particularly valuable in sports equipment because they provide strength without adding weight. A tennis racket reinforced with nanotubes won't break easily but won't be too heavy to swing quickly.
This same principle is applied in:
- Bicycle frames
- Golf club shafts
- Baseball bats
- Racing car components
Key Points to Remember:
- Graphene is a single layer of carbon atoms arranged in hexagons - it's incredibly thin but very strong
- Fullerenes are hollow, cage-like structures made of carbon atoms
- Carbon nanotubes are cylinder-shaped fullerenes that are extremely strong and conduct electricity well
- Both materials are used in electronics because they conduct electricity through delocalised electrons
- These carbon structures are revolutionising technology, from better electronics to stronger, lighter materials