 Hello everyone, myself, Ms. Dr. Tejasvis Rirangagharge working as assistant professor in the Department of Humanities and Science, Balchan Institute of Technology, Soolapur. I welcome all of you in the session of physics. In this session, we will study about nanotechnology. At the end of session, students will be able to understand the term nanoscience, nanotechnology, nanomaterials and classification of nanomaterials. These are the content of the session. In the recent years, nanotechnology has become one of the most important field in physics, chemistry, biology, engineering and technology. It is likely to be provided the change in the direction of technological advances. Nanotechnology mainly consists of processing of separation, consolidation and deformation of materials by one atom or molecule. The design, characterization, production and application of structures, device and system under control manipulation of size and shape at nanometer scale produces at least one novel characteristic. The word nano means extremely small. A nanometer is one thousand millionth of a meter. These are the convergence. Atoms are extremely small and diameter of single atom can vary from 0.1 to 0.5 nanometer depending upon the type of element. These are the some examples regarding the nanometer scale. For example, the red blood cell has approximate 7000 nanometer wide, one carbon atom approximate 0.15 nanometer in diameter and a water molecule is almost 0.3 nanometer across. Pause the video and think for a while. One angstrom in it is equal to how much nanometer? The word nanotechnology is new, but the existence of nanostructures and nano devices is not new. Such structures have existed on the earth as long as life itself. In the 4th century, A.D. Roman, the glass maker, were fabricating the glasses containing nano-sized metals. The Lycurgus Cup exhibited in the British Museum in London is belongs to that example. This cup is made from soda lime glass containing silver and gold nanoparticles. In this reflected light, the cup appears green and when light source is placed inside the cup it transmits the red light. The glass is found to be contained 70 nanometer particles when studied under transmission electron microscopy. The beautiful colors of windows are due to the presence of metal nanoparticles in the glass materials. Significance of nanotechnology? Many properties of solids depends on the size of material and many properties of the materials may changes at micrometer or nanometer range. Nanomaterials have relatively large surface area which makes the material more chemically reactive which affect their strength and electrical properties. Quantum effect begin at nanoscale which affect the optical, electrical and magnetic behavior of material. If a size or one of the dimensions of nanomaterial is smaller than its critical value then nanomaterial exhibits the properties which are different from the corresponding bulk material. Now let us see what are the nanomaterials? Nanomaterials are those materials which have structured components with a size less than 100 nanometer at least in one dimension. What is nanoscience? Nanoscience is the study of phenomenon and manipulation of materials at atomic, molecular or micromolecular scales where properties differ significantly from those at large scale. Let us see what is nanotechnology? Nanotechnology is the design, characterization, production and application of structures, device and system by controlling their shape and size at nanometer scale. The nanomaterials are classified into two different types as fullerine and nanoparticles. A fullerine is a molecule entirely composed of carbon is in the form of helospere, ellipsoid or tube. Spherical fullerine are also called as buckyballs and cylindrical are called as carbon nanotubes or bucky tubes. Fullerine are similar structure, I like that of graphite, but they contain pentagonal rings. The first fullerine was Buckminster fullerine C60. Nanoparticles are sized between 100-100 nanometers which are available in different forms that is clusters, metal nanoparticles, collides, nanocrystals and quantum dots etc. Nanopowders are agglomerates of nanoparticles or nanoclusters. Nanometer sized single crystal or single domain particles are called nanocrystals. When nanoparticles are suspended in form in the liquid phase it is called as nanocolides. Because of their small size nanoparticles have high surface to volume ratio which results in high reactivity and they also exhibits the quantum confinement effect. Depending upon the dimensions the nanoparticles are divided as zero dimensional nanoscale, these are the spears or clusters, these are also called as quantum dots. The one dimensional nanoparticles that is the nanofibers, nanowires or nanorawds, the two dimensional particles that is the thin metal plates, the three dimensional nanoparticles that is the bulk materials. We are interested in the nanoscale materials because at this scale the properties of the material are very much different than the large scale material. Two principal factors which cause the properties of nanomaterials to differ significantly from other material that is increased relative surface ratio, surface to volume ratio and quantum confinement effect. These two factors enhances the properties such as reactivity, strength and electrical characteristics. Let us see in detail one by one. Consider a sphere having a radius r, its surface area 4 pi r square, its volume 4 third pi r cube, its surface to volume ratio is 3 by r, when radius of sphere decreases its volume, surface to volume ratio increases. Let us see this effect in detail with example. Consider for a one cubic volume as shown in figure having a surface area 6 meter square. When the surface area is divided into 8 pieces, its surface area is 12 meter square. When the same volume is divided into 27 pieces, its surface area is 18 meter square. Thus when the given volume is divided into smaller pieces, surface area increases. Hence as particle size decreases, a greater proportion of atoms are found at the surface compared to those inside. Hence nanoparticles have much greater surface area per given volume compared with large particles. It makes the material more reactive. As growth and catalytic chemical reactions occurs at the surface, the nanoparticles form will be much more reactive than the larger particles. Also this affect their strength or electrical properties. Now let us see the second effect that is the quantum confinement effect. When the dimensions of material is of order of mean free path of electron, then energy level of electron changes and this effect is known as quantum confinement effect. When material is sufficiently small, typically 10 nanometer or less, then organization of energy levels into which electrons can climb or fall the changes. This concept can be studied with the help of the energy level diagram. When the atoms are isolated, the energy levels are discrete. When very large number of atoms are closely packed to form a solid, the energy levels are split and forms a band. The nano materials represent the intermediate stage of energy when the dimensions of potential well or potential boxes are of order d Broglie wavelength of electron, then energy levels of electron changes. This effect is known as quantum confinement effect. When material is sufficiently small of order 10 nanometer or less, organization of energy levels of electron can changes. This effect can change or affect the optical, electrical and magnetic behavior of material. Hence these two effect affect the properties of the material at nanometer scale. The increase in surface to volume ratio and the quantum confinement effect, splitting of energy levels become more useful in the quantum in the nano scale range. These are the references used, thank you.