Nanoscience and Materials

1983$3995

1992$1400

2002$480

2009$199

These advances in technology would not have been possible without nanotechnology.

Nokia Morph : The Next Generation of Mobile Phones?

What affects our choice of materials?

• What do they have in common?

– Both are forms of carbon.

• How are they different?

– Appearance, hardness, conductivity.

Diamond and Graphite

• Both are forms of carbon.

• However, changes in the arrangement of the atoms at the nanoscale cause these materials to behave differently.

• Within diamond, every carbon atom is bonded to 4 other carbon atoms.

• Within graphite, every carbon atom is bonded to 3 other carbon atoms.

Why do they behave differently?

This structure is known as a tetrahedron.

The 4 bonds to the central carbon atom spread out evenly, so the base structure of diamond is a 3-D shape.The structure builds up because every carbon atom is bonded to another 4 carbon atoms.

Diamond

The bonds to the central carbon atom in graphite spread out evenly, so the base structure is a 2-D shape (has length and width but no height).

The structure of graphite sheets builds up because every carbon atom is bonded to 3 other carbon atoms.

Bonds to 3 C atoms.

The hexagonal pattern in which the atoms are arranged can now be seen.

Graphite

• As the structure continues to build up, it remains 2- Dimensional (flat).

• A 3-D shape is formed by the layering down of a number of these 2-D structures (called Graphite sheets) on one another.

Sheets of graphite in pencil lead – taken in CRANN using a SEM.

Graphite

• Very weak forces - means that sheets can be peeled off easily.

• This is why graphite is soft and a useful material for pencils.

• These layers are kept together by a force of attraction known as Van Der Waals forces.

Van der Waals forces

•This means that a single layer of graphite is very strong.

•In 2004, a single layer of graphite was isolated for the first time.

•This single layer of graphite is known as Graphene, and consists of a sheet of carbon atoms, just one atom thick.

However, the bonds IN the graphite sheet are very strong due to their partial double bond nature.

Graphene

• One of the strongest materials known - 200 times stronger than steel, but still bendable!

• Excellent electric conductor.

• Transparent.

• Impermeable - substances as small as helium (He) atoms cannot pass through the hexagonal patterns.

Graphene: amazing properties

• How do we isolate graphene from graphite?

+ =

• In CRANN scientists have isolated graphene sheets using soap!

• Why isolate graphene? What could it be used for?

Isolating graphene

• Electronics devices – used to make transistors and display screens e.g. e-paper, smart phones, transparent loudspeakers.

• Extremely sensitive sensors for gases and diseases. • Stronger, lighter materials, e.g. household products, sports,

transport.• Invisibility cloaks!

Graphene will change the world around us!

• Apart from graphene, other “layered” materials can be split into single layered “nanosheets”.

• Offering a whole range of new “super” materials.• Can be metallic, semiconducting or insulating, depending on their

chemical composition.• Uses – added to plastic to make strong materials; supercapacitors,

thermoelectric devices.

Other “super” materials

• A form of carbon with a cylindrical nanostructure.• Walls consist of one-atom thick sheet of carbon.• Discovered in 1991.

Carbon nanotubes

• Nanotubes can be imagined as rolled up sheets of graphene.

• The graphene sheet can be rolled in 3 different ways to form different types of nanotubes.

• These subtle differences cause the nanotubes to have different electrical properties.

Carbon nanotubes

• Mechanical - nanotubes have a very high strength to weight ratio; they are at least 100 times stronger than steel but only one sixth as heavy.

• Electrical - nanotubes in the Armchair configuration conduct electricity very well; nanotubes in the Zigzag and Chiral configuration are semi-conductor materials.

Properties of nanotubes

• Electronics– nanotube transistors for use in computers and phones?

• Reinforce plastics and concrete structures e.g. aircraft and bridges.

• Energy– hydrogen fuel cells?• Sports industry to create robust,

lightweight equipment.

Some possible uses of CNTs

• Could carbon nanotubes be the ideal material for a cable that would extend all the way to outer space because of their high strength to weight ratio?

Space elevator - Royal Society Christmas Lecture [12 min YouTube]

Space elevator

• Nanowires e.g. silver could be used in flexible electronic display panels like e-paper.

• Nanoparticles e.g. zinc, titanium have made suncreams “invisible”.

Network of silver nanowires. e-paper.

More nanomaterials

• Nanoelectronics in mobile phones, e-readers, notebooks.

• In clothing, to repel dirt and water.

• Cosmetics and sunscreens.

• In tennis rackets and bicycle frames.

• Socks – silver nanoparticles to keep your feet cleaner!

• Coatings on cars and sunglasses to make them anti-misting and scratch-proof.

• In paints to make them anti-microbial.

Nanotechnology is already here!

• When choosing a material, its properties, performance and cost need to be considered.

• There are different forms of carbon which differ in the arrangement of carbon atoms at the nanoscale.

– Diamond.

– Graphite (and graphene).

– Carbon nanotubes (CNTs).

– Buckyballs.

• A lot of research is being conducted with graphene and CNTs for their commercial application, particularly in:

– Electronics.

– Energy- thermo-electrics, supercapacitors.

– Reinforcing materials to make them stronger and lighter.

• Nanomaterials are becoming more common in everyday use.

Summary