Nanoscience and Technology and its description
- 1. Nanoscience and Technology (3170509) Introduction and classification
- 2. Introduction • The word ‘nano’ is to a Greek prefix meaning dwarf or something very small and depict one billionth (10–9 ) of a unit. • Nanotechnology is a technology that deals with small structures or small sized materials. The typical dimension spans from sub nanometer to several hundred nanometers. • One nanometer is approximately the length equivalent to ten hydrogen or five silicon atoms aligned in a line. • Small features permit more functionality in a given space. • Materials in the micrometer scale mostly exhibit physical properties the same as that of bulk form; however, materials in the nanometer scale may exhibit physical properties distinctively different from that of bulk.
- 3. What is nano era • Traditionally, civilizations were named after the metals or materials used. Thus, we have the Stone Age, Bronze Age and Iron. The current age is driven by the applications of silicon and other advanced materials. • The coming decades could well be dominated by nanotechnology (‘Nano Age’), a deviation from the practice of identification of an era based on materials to one based on technology. • New technologies require new materials with superior physical, chemical and mechanical properties. Materials science and engineering have provided us materials with widely varying properties made by changing the composition or altering the microstructure using thermochemical- mechanical methods.
- 4. What is nano era • Consequently, micro structural engineering and the study of structure–property correlation have become very important. The mechanism by which ultrafine microstructures affect the properties of solids could be better understood after the advent of the theory of lattice defects and dislocation theory, and the availability of advanced high-resolution microscopy techniques such as electron, atomic force and field ion microscopy. • These developments have helped in understanding the correlation between the structure and properties of solids.
- 5. zero-dimensional nanostructures or nano materials
- 7. Difference from bulk material • Material in this size range exhibits some remarkable specific properties; a transition from atoms or molecules to bulk form takes place in this size range. • Crystals in the nanometer scale have a low melting point (the difference can be as large as 1000°C) and reduced lattice constants(the lattice constant, or lattice parameter, refers to the physical dimension of unit cells in a crystal lattice. Lattices in three dimensions generally have three lattice constants, referred to as a, b, and c.), since the number of surface atoms or ions becomes a significant fraction of the total number of atoms or ions and the surface energy plays a significant role in the thermal stability. • Crystal structures stable at elevated temperatures are stable only at much lower temperatures in nanometer sizes, so ferroelectrics and ferromagnetics may lose their ferro electricity and ferromagnetism when the materials are shrunk to the nanometer scale. • Bulk semiconductors become insulators when the characteristic dimension is sufficiently small (in a couple of nanometers). Although bulk gold does not exhibit catalysis properties, Au nanocrystal demonstrates to be an excellent low temperature catalyst.
- 8. Definition • The study of microstructures of materials using electron microscopy and the growth and characterization of thin films as nanotechnology. • A bottom-up approach in materials synthesis and fabrication, such as self- assembly or bio mineralization to form hierarchical structures like abalone shell is nanotechnology. • Drug delivery, e.g., putting drug inside carbon nano tubes, is considered as nanotechnology. • Micro electromechanical systems (MEMS) and lab-on-a-chip are considered as nanotechnology. • More futuristic or science fiction-like opinions are that nanotechnology means “something very ambitious and startlingly new, such as miniature submarines in the bloodstream, smart self-replication nano robots monitoring our body, space elevators made of nano tubes and the colonization of space”.
- 9. Definition • Nanotechnology can be understood as a technology of design, fabrication, and applications of nanostructures and nanomaterials. • Nanotechnology also includes fundamental understanding of physical properties and phenomena of nano materials and nanostructures. Study on the fundamental relationships between physical properties and phenomena and material dimensions in the nanometer scale, is also referred to as nanoscience. • In the United States, nanotechnology has been defined as being “concerned with materials and systems whose structures and components exhibit novel and significantly improved physical, chemical and biological properties, phenomena and processes due to their nanoscale size” • Nanomaterials may be classified as those materials which have at least one of their dimensions in the nanometric range, below which there is significant variation in the property of interest compared to microcrystalline materials.
- 10. Definition • Nanostructured materials are those with at least one dimension falling in nanometer scale, and include nanoparticles (including quantum dots, when exhibiting quantum effects), nano rods and nano wires, thin films, and bulk materials made of nano scale building blocks or consisted of nano scale structures. Many technologies have been explored to fabricate nanostructures and nano materials. • Definition of nanotechnology to date appears on the NASA website:…the creation of functional materials, devices and systems through control of matter on the nanometer length scale (1–100 nm), and exploitation of novel phenomena and properties (physical, chemical, biological) at that length scale.
- 11. CLUSTERS AND MAGIC NUMBERS • When atoms come together, they initially form two-dimensional clusters. When more atoms join the cluster, they become three-dimensional with topographically close-packed arrangements, before taking up a crystal structure. It has been found that clusters of certain critical sizes, i.e., clusters with a certain number of atoms in the group, are more stable than others. Such clusters are stabilized either by geometric or electronic considerations. • Magic number is defined as the number of atoms in the clusters of critical sizes with higher stability. This effect was initially observed in gaseous metal atoms, in the early 1980s. Subsequently, a similar effect was also noticed during the condensation of atoms from a vapour phase on a substrate surface, for example, during thin film deposition. • Magic numbers based on electronic shells were first observed in mass spectra of alkali metal clusters. The stability of such clusters as a function of the size did not follow a continuous function. It was seen that for some specific number of atoms in the cluster (N), N = 2, 8, 20, 40, 58, 92, etc., the free energy is lower, resulting in stabilization of the cluster.
- 12. CLUSTERS AND MAGIC NUMBERS • Small clusters of atoms behave quite differently from bulk materials. Studies indicate that bulk properties are scalable only up to a certain critical grain size and below this limit, the behavior of small clusters of atoms cannot be predicted on the same mechanistic or heuristic basis. Recent work has shown that atomic clusters containing certain magic numbers of atoms have quite distinct behavior. For example, when 60 carbon atoms come together, the structure of carbon has unique icosahedral symmetry (crystal possessing 20 regular triangular faces) and such clusters are now widely referred to as fullerenes and have exceptional properties. • Krypton, being a noble gas, does not form strong chemical bonds with other atoms as well as with itself. However, Lethbridge and Stace of University of Sussex have succeeded in synthesizing clusters of krypton atoms with icosohedral symmetry. This was possible by allowing sudden expansion of krypton gas through a small orifice in a vacuum chamber. So far, clusters of 147 and 309 atoms have been detected with mass spectrography. There are models to suggest that the magic numbers of 13, 55, 147, 309, 561and 923 would have higher stability.
- 14. NANO MATERIAL HISTORY • Nanomaterials have been produced and used by humans for hundreds of years. • However, the understanding of certain materials as nanostructured materials is relatively recent, made possible by the advent of advanced tools that are capable of resolving information at nano scale.
- 15. NANO MATERIAL HISTORY • the beautiful ruby red colour of some ancient glass paintings is due to gold and silver nanoparticles trapped in the glass matrix. • The colours of stained glass panels depend on the particle size of gold and silver nanoparticles introduced into them. Such colloids were made even in the 11th century when medieval artisans mixed gold chloride with glass.
- 16. NANO MATERIAL HISTORY • The decorative glaze or metallic film known as ‘luster’, found on some medieval pottery, contains metallic spherical nanoparticles dispersed in a complex way in the glaze, which gives rise to special optical properties. The techniques used to produce these materials were a closely guarded secret, and are not completely understood even now.
- 17. NANO MATERIAL HISTORY • Carbon black is a nanostructured material that is used in car tyres to increase the • life of the tyre and impart black colour. This material was discovered in the 1900s.
- 18. NANO MATERIAL HISTORY • Fumed silica, a component of silicon rubber, coatings, sealants and adhesives, is also a nanostructured material. It became commercially available in the 1940s.
- 19. NANO MATERIAL HISTORY • Steel (an alloy of iron and carbon) is believed to have been first prepared in India about 1500 years ago and is popularly known as wootz (India): • This steel was used . to make swords, which were so strong and sharp that they could easily cut a helmet into two pieces. • Very recently, high-resolution electron microscopy of such a steel (picked up from a museum) showed the presence of carbon nanotubes in them, which has surprised scientists. • People now believe that the high strength of these steels may be due to the presence of these carbon nanotubes, which are known for their exceptionally large Young’s modulus.
- 20. NANO MATERIAL HISTORY • Supported lipid bi layer formation on a surface covered with nanoparticles of different sizes. Trans membrane pores (or holes) are formed around particles of approximately 1 to 20 nm diameter. • The 3D figures shown here are the adapted representation of the series of tapping mode atomic force microscopy images recorded under liquid buffer medium.