1 Ibid p.19
2 Ibid p.21
(ii) Quantum Dots (QDs) QDs are nanocrystals made up of a few hundreds atoms of semiconductor materials. These are tiny inorganic crystals that create light when stimulated with photons or electrons. The properties of QDs can be applied in transistors, solar cells, LEDs, laser diodes, medical imaging and diagnostics, quantum computing etc.2
(iii) Dendrimers These are nanosized polymers unit. There are numerous chain ends which are located on the surface of dendrimers which can be used for various functions such as enhanced chemical reactivity, catalysis etc. The dendrimers can be used as nanoscale carrier molecules for targeted drug delivery and also for water filtration.
(i) Fullerene or Buckyball It is also known as Carbon 60 (C60). It is a three dimensional structure of carbon atoms which is arranged in sphere about 1 nm in diameter with a pattern of hexagons and pentagons similar to a soccer ball. It acts like a semiconductor. The physical properties of fullerene include high hardness and the ability to withstand great pressure. Fullerene finds its uses in lubricants, drug delivery ,electronic circuits, solar cells, sensors etc.
(c) Nanomaterials in Three Dimensional Nanomaterials that are nanoscale in three dimensions are categorized as three dimensional nanomaterials. Nanocrystalline materials made up of nano meter sized grains, also fall in to this category.
(iii) Nanowires These are self-assembled linear arrays of dots or fine wire like structures which can be made from a wide range of materials. Their optical, magnetic and electrical properties are remarkable which can be utilized in high density data storage, electronic nano devices, quantum devices etc.
(ii) Inorganic Nanotubes These are two dimension layered solids such as tungsten sulphide, molybdenum disulphides etc. They occur in mineral deposits of natural origin. They exhibit high crystallinity, good uniformity and dispersion, high impact resistance with enhanced thermal, mechanical and electrical properties.
(i) Carbon Nanotubes (CNTs) CNTs are tubular cylinders of carbon atoms that have extraordinary mechanical, electrical, thermal, optical and chemical properties. These are categorized as single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs). These are extended tubes of rolled graphene sheets with diameter in nanometers and length in micrometers or centimeters. The CNTs are mechanically very strong, flexible and good conductors. They are now being used extensively in sensors, display devices, nano electronics etc.
Nanomaterials that are nanoscale in two dimensions are categorized as two dimensional nanomaterials. Nanofilms, nanolayers and nanocrystals are the example of two dimensional nanomaterials and they exhibit novel electrical and mechanical properties due to their plate like structure and shape.
(b) Nanomaterials in Two Dimensional
Thin films and surfaces are some of the examples of nanomaterials in one dimension. The thin films are used in fuel cells, solar cells, electronic industry, pharmaceuticals, optics, electronic devices, sensors and bio-devices due to their unique properties and large surface areas.
(a) Nanomaterials in One Dimension
Nanomaterials are not only just miniaturization of materials, but a production approach to produce nanoscales structures to exploit the novel properties of materials which are not exhibited at the bulk state. At nanoscale unique optical, magnetic, electrical and other properties emerge. These properties have the potential to lead to new applications in medical science, electronics, manufacturing, industry, social and human engineering. Nanomaterials can have spherical, tubular and irregular shapes. They can be classified based on their existence in one dimension, two dimensions or three dimensions.1