1. NANOMATERIALS

2. INTRODUCTION  Nanomaterials means particles of Very minute size.  In recent years, NANOMATERIALS has become one of the most important and exciting fields of research in physics, chemistry, biology, medicine, engineering and technology.  The word Nano has a Greek origin meaning Dwarf (small).  Technically, the prefix Nano means ‘’one billionth‘’ part of a unit or 10 to the power of -9 and nanometer means 10 to the power of -9 meter, a unit of length.  A nanometer is used to measure things that are very small such as atoms and molecules. 1 nm equal to 10 power -9 meter 1 ns equal to 10 power -9 seconds and so on…. For example: Hydrogen atom is equal to 0.1 nm Red blood cell is equal to 500 nm in size Visible colour wavelength is equal to 400 to 700 nm  when ‘nano’ prefix is used with science and technology it becomes a new field of science.

3. NANOSCIENCE Nanoscience is the study of fundamental particles of molecules and structure with the size nearly 1nm to 100nm and the structures which are of 1nm to 100 nm are called as nanostructures. or It is the study of phenomena and manipulation of materials at atomic, molecule and macromolecular scales. NANOTECHNOLOGY Nanotechnology is the design, characterization, production and application of structures devices and systems.The work is done by controlling shape and size at the nanometer scale or In other words, the technology of design, synthesis, characterization and applications of materials on nanoscale is called nanotechnology

4. HISTORY  First Professor Norio Taniguchi Of Japan in 1974 used the word nanotechnology to describe the extension of traditional silicon machining down into region smaller than one micron.  Next, Richard Feynman, in his famous speech discussed the possibility of Manipulating and controlling things on molecular scale in order to achieve electronic and mechanical system with atomic sized compliments  An American engineer Eric Drexler have speculated extensively about the laboratory synthesis of machines at the molecular level via manipulation techniques and producing Components much smaller than any microprocessor which has been called molecular nanotechnology

6. NANOPARTICLES  Nanoparticles are the particles that have sizes approximately between 1nm and 10nm.  They are available in different forms such as clusters, colloids, metal and Semiconductor nanoparticles, quantum dots etc.  Nanoparticles may exhibit size-related properties, which differ from those observed in bulk materials.  They have greater scientific applications as they could effectively form a bridge between the bulk materials and atomic or molecular structures.  Nano particles have shown important applications in various day to day usable products.

7. Applications of Nanoparticles Nanoparticles are :  Used in displays that are cheaper, larger, brighter and more efficient.  Used in renewable energy ultrahigh performance solar cells.  Used in antibacterial silver coating on wound dressing.  Used to improve efficiency of coolant in transformers.  Particles have also been attached to textile fibers to create smart and functional clothing.  These particles are frequently used in anti-reflection coating and to make light based sensors for cancer diagnosis.  The microchip and its revolutionary applications in computing, communications, consumer electronics and medicine.

8. METAL NANOCLUSTERS  A group of nano particles of different sizes is called a cluster.  Nanometer sized metal clusters have attracted much attention from scientists and engineers because they display specific physical and chemical properties that the bulk materials do not possess.  Metal nanoclusters can be synthesized from a)S-Block metals like Alkali & Alkaline elements. b)Metals of covalent character. c)Transition metals.

9.  Metal nanoclusters formed from S-Block metals (i.e.., alkali and alkaline earth metals) where the bonding between the atoms is metallic involving mainly the valance s- orbitals.  Metals like aluminum, whose bonding has some covalent character and  Transition metals that have greater degree of covalency and directionality in the bonding involving the valance d-orbital can also form nanoclusters.

10. Cont… Nanoclusters have a high percentage of items on the surface so that rearrangement of atoms lower the surface energy by forming additional surface bonds.

11. PROPERTIES OF NANOCLUSTERS:  Properties of nanoclusters depends on their size.  This size dependence may enable cluster based materials to be produced with novel optical magnetic or electronic properties.  Metal clusters that are generally supported by an inert oxide substrate can themselves be used as very finely dispersed metal for catalysis applications.

12. SYNTHESIS OF METAL NANOCLUSTERS Metallic nanoclusters were synthesized using many processes and they are:  simple chemical bath deposition method  Ionized cluster beam deposition method  photolytic method  ultrafast lasers and electron pulse radiolysis method

13.  Firstly, a simple chemical bath deposition can be used to synthesize gold nano clusters stabilized by thiol (molecules containing Sulphur) molecules, which contain a long hydrocarbon chain and Sulphur group. The Sulphur atom binds strongly to the gold atom on the particle’s Surface, from which the long carbon chain extends. A long chain is important because it prevents particles from aggregating in an organic solvent.  Secondly, Ionized cluster beam deposition, a physical vapor process has recently received a great deal of attention as promising method for synthesizing high-quality metal Nanoclusters at low-temperature.

14.  The figure shows the transmission electron microscope (TEM) picture of gold nanoclusters grown by ionized cluster beam deposition method.  Among numerous methods for preparation of metal clusters, photolytic method is very popular because of easing in preparation of nano clusters of Narrow size distribution. In addition complimentary techniques, such as ultrafast lasers and electron pulse radiolysis can be employed in combination for preparation of metal nanoclusters

15. APPLICATIONS OF METAL NANOCLUSTERS  used as a catalyst in certain chemical reactions  silver Nanoclusters are used in photography.  Also the interaction between energetic metal clusters and surfaces are of growing scientific interest because of the potential importance for applications such as surface metallization, surface cleaning, precision machining and Cluster fusion.

16. SEMICONDUCTOR NANOPARTICLES  Semiconductor nano particles are particles with diameter is in the range of 1 to 20nm.  This nano particles play a significant role in the technological development in the future.  The reduction in the dimensions of particles to such small values results in physical properties that differ completely from those of corresponding bulk material.  This unique physical properties give rise to many potential application is in areas such as catalysis electronics luminescence nonlinear optics optoelectronics and solar energy conversion.

17. cont….  There are two fundamental factors related to size of the individual nanocrystals for the existence of this unique properties.  The first is the large surface to volume ratio that is as the size of the particle become smaller, the ratio of the number of surface atoms to those in the interior increases so that more atoms reside on the surface. This leads to the surface area playing a dominant role in the properties of materials.  The second factor is the actual size of the particle.As the size of solid become smaller the band gradually becomes larger because of quantum confinement effects, particularly at the national level. This is a consequence of the confinement of an electron in a box giving rise to discrete energy levels rather than a continuous band as in the corresponding bulk materials. also there is a change in the electronic properties of the material with the decrease in the size of the solid from macro to nano scale.

18.  Cadmium chalcogens (CdX,withX= sulphide, selenide, Telluride) are the well- studied semiconductors in nanoparticle form. These were probably the first materials used to demonstrate quantum size effects corresponding to change in the electronic structure with particle size i.e.., the increase of the energy bandgap with the decrease in the size of the particles.  Figure shows a picture of cadmium selenide nanoparticles dissolved in toluene, exhibiting different colors when exposed to an ultraviolet lamp.

19. Cont…. The three noticeable Colors  blue at 481 nm,  green at 520 nm and  orange at 612 nm are due to variation of the energy bandgap with particle size, smaller the particle size, the shorter the emitted wavelength of light.  The liquid with blue colour has the smaller particle size while the liquid with orange colour has the largest side size.

20. PREPARATION OF SEMICONDUCTOR NANOPARTICLES  Generally the method of Nanoparticle preparation and the particle size determines particle physical and electronic properties of the Semiconductor nano particles produced.  There are number of methods for the preparation of nano particles, the main method of preparation of Semiconductor nano particles was the classical collide chemistry, involving controlled precipitation from colloidal solutions.  For example the preparation of nano particles of cadmium selenite involves the reaction between aqueous solutions of CdSO4 and (NH4)2S.  In this reaction the particle size is determined by altering the pH of the solution  A recent method for preparing Semiconductor nanoparticles is to use organometallic and/or metal organic compounds under anaerobic conditions.  The preparation of CdSe and ZnSe nanoparticles involves the use of dimethylcadmium or dimethylzinc and selenium containing particle dissolve in TOPO(tri-n-octylphosphine oxide). varying the temperature and size of the reaction controls the particle size.

21. APPLICATIONS OF SEMICONDUCTOR NANOPARTICLES  The research on Semiconductor nano particles has led to the fabrication of number of devices.  Electroluminescence Devices were initially developed from the dispersion of CdSe nanoparticles with a conducting polymer as the capping agent.  Replacing the polymer with a layer of CdS has produced the device with an increased deficiency and lifetime by factors of 8 and 10 respectively

22. CARBON NANOMATERIALS  Carbon can born to itself to form extremely strong 2D sheets.  It exists in different from such as Diamond, Graphite, carbon clusters and carbon nanotubes. Recently these forms have attracted much attention due to their extraordinary behavior when the size of the material goes down to nanoscale.  These nano structures are made from 2D carbon sheets that have rolled and folded into a diverse range of 3D structures.  Among these nano structures the most famous are the ball shaped carbon cluster known as fullerene and the cylindrical shaped nano tubes. Other shapes such as carbon nanocones, nanohorns are also possible.  Carbon nano materials can be classified as 1.carbon clusters or fullerene, 2.carbon nano tubes, 3.graphines.

23. CARBON CLUSTERS OR FULLERENE  Fullerenes are molecules that are composed of entirely carbon in the form of clusters.  They were discovered in 1985 by curl, smalley and kroto.  It consists of carbon atoms in clusters containing 60,70,76,78,84,240, and 540 in number.  The cluster with 60 carbon atoms is called as C 60 Fullerenes-They may take the shape of a hallow sphere, ellipsoide, tube or plane.

24. STRUCTURE OF C 60 AND C 70 MOLECULES:  These cluster were named as Fullerenes after Richard Buckminster Fuller, an architect known for the design geodesic domains.

25. SYNTHESIS OF CARBON CLUSTERS  Fullerenes occur in nature only in small amounts. Currently Different techniques are available for producing them in greater values.  The modern technique uses a Benzene flame to produce fullerenes.  Catalytic chemical vapor deposition from ethanol vapor are is used.  A common methods is to pass more current between two graphite electrodes in an inert atmosphere. The resulting carbon plasma arc between the two electrodes cools in to sooty residue. From this soot, fullerenes can be isolated.  Each fullerenes consist of twenty Hexagonal and twelve Pentagonal rings forming a close cage like structure.  Each carbon atom is bonded by three other SP2 hybridization.

26. PROPERTIES OF FULLERENES  These are harder than diamond, stable and reactive at times.  They are Sparingly soluble in many solvents and soluble in toluene and carbon disulphide. APPLICATIONS OF FULLERENES  These are used as excellent solid lubricants.  These have lot of potential in medicine and the studies are under progress for their use in binding specific antibiotics to target bacteria and even certain cancer cells like melanoma.  There electrical properties helps us to use them in electronic filed ranging from data storage to production of solar cells.

27. CARBON NANOTUBES  The large cylinder tube like structures made of carbon nanoparticles are called ‘carbon nanotubes’.  Carbon nanotubes (CNTs) were first observed by Sumio Ijima in 1991.  The molecular structure of graphite is a planar network of interconnected hexagonal rings of carbon atoms.  In the normal graphite, these planar sheets of carbon are stacked one over the other so that they can be used as a lubricant.  When the planar graphite sheet is rolled into a cylinder and their edges are joined together to form into a tube. This cylindrical tube like structure made up of carbon are called as CARBON NANOTUBES.  The sheet determines whether a CNT is metallic or semiconductor in nature.

28. TYPES OF NANOTUBES  Nanotubes commonly exists in two main types, 1.Single walled nanotube(SWNT) 2.Multi walled nanotube (MWNT) Both these structures are typically a few nanometers in diameter and could extend from over several micrometers to centimeters in length.

29.  Single walled nanotube(SWNT): Depending on the cross-sectional structure, SWNT exists in 3 structures: Zigzag Armature chiral

30. Multi walled nanotube (MWNT): It consists of multiple layers of carbon nanoparticles in tube shape with complex arrays. The MWNT can have either a regular layering or random layering of carbon nanotubes.

31. SYNTHESIS OF CARBON NANOTUBES  Carbon nanotubes can be synthesized using three main techniques: 1.Laser evaporation 2.Carbon arc 3.Chemical vapor deposition

32. Properties of carbon nanotubes  These have high electrical conductivity.  These are stable at high temperature, in varied environment and are corrosion resistant.  These are good thermal conductors along the tube, but good insulators laterally to the tube axis.

33. APPLICATIONS OF CARBON NANOTUBES  STRUCTURAL: Use of carbon nanotubes increase the tensile strength halt crack propagation in concrete buildings.  CHEMICAL: Nanotube membranes have been effectively used for water filtration.  AUTOMOBILE: CNTs are used as a filter to reinforce car tyres.  ELECTROMAGNETIC: Thin sheet made using nanotubes are more stronger and lighter than steel that could be effectively used as heat sinks for electronic chip boards and a back light for LCD screens.  BIOMEDICAL: Nano crystalline zirconia is hard,wear resistant, bio-corrosion resistant and bio-compatible and can be used as body implants and silicon carbide is one of the best material for artificial heart.