Nanotechnology

A material with

• any external dimension in the nanoscale (size range from approximately $1 – 100\text{ nm}$).
• having internal structure or surface structure in the nanoscale.

At nanoscale, materials exhibit very unusual and very interesting properties. For example, graphene has very high young’s modulus and very high carrier mobility.

Nomenclature

Nano-object

An object with any external dimension is in the nanoscale.

Examples: carbon nanotube, bucky ball.

Nano-structured material

A material where its internal or surface structure is in the nanoscale.

Examples: $\ce{TiO2}$ nanotube films. $$

Nano in nature

• Lotus leaves being super-hydrophobic
• Gecko adhesive system

Nano-science

Study of structures and materials on the nanoscale.

Nanotechnology

Development of materials and devices by exploiting the characteristics of particles on the nanoscale.

Applications

• Nanoscale transistors
  • Higher-performance
  • Improved energy efficiency
• Magnetic data storage
  • High data density and data capacity
  • Ultra compact
• Nano-medicine and drug delivery
• Energy storage

Preparation of nanomaterials

Top-down approach

Nanoscale dimensions are created using larger components, by externally controlled devices.

Examples: Lithography, Etching techniques.

Photolithography

Can be used to create nanoscale patterns in thin films or bulk substrates.

The steps:

1. Coat $\ce{Si}$ wafer with a photosensitive material. A material which changes its properties when exposed to electromagnetic radiation
2. Add a mask and use an EM radiation.
3. Developer solution removes either reacted or unreacted material.
4. The silicon wafer is etched to transfer the pattern onto silicon wafer.
5. Photosensitive material is removed.

Bottom-up approach

Molecular components arrange themselves into more complex nano materials/objects.

Examples: Molecular self-assembly, Chemical vapour deposition