1. Nanotechnology Dr.S.Sanyasi Raju Dr.S.Sanyasi Raju Reader in Physics Reader in Physics M.R.College(Autonomus) M.R.College(Autonomus) VIZIANAGARAM VIZIANAGARAM

2. Nanotechnology refers broadly to a field of applied science applied science applied science and technology whoseapplied science unifying theme is the control of matter on molecularmolecular the molecular level in scales smallermolecular micrometre micrometre than 1 micrometre, normally 1 to 100 nanometers,micrometre and the fabrication of devices within that size range.

3. The The term nano comes from a Greek word meaning dwarf. Nanotechnology Nanotechnology is science and engineering at the scale of atoms and molecules Materials Materials at the nanoscale are typically between 0.1 and 100 nanometres (nm) in size 1nm is one billionth of a metre (10-9 m).

4. Most Most atoms are 0.1 to 0.2 nm wide Strands Strands of DNA are around 2 nm wide, Red Red blood cells are around 7000 nm in diameter Human Human hairs are typically 80,000 nm across. Ananometre is also about the length human fingernails grow by each second.

5. Materials Materials of this size can display strikingly different physical and chemical properties, compared with larger particles of the same material. These These properties are largely due to two factors Smaller Smaller particles have a relatively larger surface area, compared with their volume, making them much more chemically reactive In In addition - at scales below 100 nm - the weird quantum effects of the atomic world start to take hold. Quantum Quantum effects can change the optical, electronic or magnetic qualities of materials in unpredictable ways.

6.   Materials reduced to the nanoscale can suddenly show very different properties compared to what they exhibit on a macroscale, enabling unique applications.   For instance, opaque substances become transparent (copper); inert materials become catalysts (platinum);   Stable materials turn combustible (aluminum); solids turn into liquids at room temperature (gold);   Insulators become conductors (silicon).   A material such as gold, which is chemically inert at normalgold scales, serve as a potent chemical catalyst at nanoscalescatalyst   Much of the fascination with nanotechnology stems from these unique quantum and surface phenomena that matter exhibits at the nanoscale.

7. Construction at the nanoscale presents a unique set of challenges Devices at the 1 nm to 100 nm scale are difficult to assemble using traditional methods. Nanodevices are often too big and complex to be manufactured by chemists, yet too small to be pieced together by engineers. So far, most nanomaterials and devices have been manufactured in one of two ways:  Bottom-up Bottom-up approaches rely on building nanodevices brick by brick - or molecule by molecule - rather like putting together a house or a car. In the "top-down" approach, nano-objects are constructed from larger entities without atomic-level control Simpler nanoparticles, such as titanium dioxide or iron oxide used for cosmetics, can be made via chemical synthesis.

8. Nanotechnology Nanotechnology in consumer devices and other applications right now now : Computer Computer hard drives Car Car parts and catalytic converters Scratch- Scratch- and wear-resistant paints and coatings Sunscreens Sunscreens (titanium dioxide nanoparticles are transparent, yet absorb UV light at the same time) Metal Metal cutting tools Antibacterial Antibacterial bandages incorporating silver nanoparticles Nanofilm-coated Nanofilm-coated "self-cleaning" windows and Stain-resistant Stain-resistant fabrics

9.   Atom-thick carbon transistor could succeed silicon   Graphene makes graphite when stacked in layers, and carbon nanotubes when rolled into a tube.

10. Size matters when it comes to graphene circuits   When it comes to using nanoscopic ribbons of graphenegraphene to make electronic circuits, researchers have discovered that size really does matter.   Supercomputer simulations of quantum mechanical behaviour suggest that not just the width, but also the length, of these atom-thin sheets of carbon determines whether they will act as a conductor or a semiconductor   A finding that could prove helpful for harnessing graphene's unique electronic properties.   Nanoribbons are long, thin strips of graphene that are etched from graphene sheets using electron-beam lithography.

11.   Because graphene can be either a conductor or semiconductor, and because it can transport electrons long distances with little scattering, it could be an ideal material for nanoelectronic devices.   Some researchers think that they might be able to make entire integrated circuits using only components made out of graphene.   Graphene was first produced in the lab in 2004 by repeatedly peeling off successive layers off of graphite – a process known as "mechanical exfoliation".

12.   Graphene also conducts electricity faster than most materials since electrons can travel through in straight lines between atoms without being scattered.   This could ultimately mean faster, more efficient electronic components that also require less power.

13.   Buckminsterfullerene C 60, also known as the buckyball, carbon structuresfullerenes carbon structuresfullerenes is the simplest of the carbon structures known as fullerenes.carbon structuresfullerenes   Members of the fullerene family are a major subject of research falling under the nanotechnology umbrella.

14.  reconstructionAu (100)  Image of reconstruction on a clean Au (100) surface, reconstructionAu100reconstructionAu100 scanning tunnelingmicroscopy scanning tunnelingmicroscopy as visualized using scanning tunneling microscopy.scanning tunneling microscopy atoms atoms The individual atoms composing the surface are visible.atoms

15. The World's Smallest Car The World's Smallest Car The World's Smallest Car The World's Smallest Car

16. THIS YEAR NOBLE PRIZE IN PHYSICS WAS AWARDED TO ALBERT FERT OF FRANCE AND PETER GRINBERG OF GERMANY FOR THEIR PIONEERING WORK ON GIANT MAGNETO RESISTENCE (GMR)

17. THIS NANOTECHNOLOGY MINIATURISED THE HEAD THAT READS THE HARD DISK THAT STORES GIGA BYTES OF INFORMATION, BE IT SCIENTIFIC DATA OR MUSIC, IN A JIFFY.

18. MAGNETORESISTANCE (MR) IS CHANGE IN THE RESISTANCE TO FLOW OF CURRENT IN A CONDUCTOR, WHEN PLACED IN A MAGNETIC FIELD THE CONDUCTOR IN THIS CASE MUST BE A MAGNET LIKE Fe, Co, OR Ni AN INCREASE IN RESISTANCE WAS NOTICED WHEN THE CONDUCTING OF ELECTRIC CURREENT WAS PARALLAL TO THE MAGNETIC FIELD RESISTANCE DECREASES WHEN THE MAGNETIC FIELD IS APPLIED IN TRANSVERSE DIRECTION BUT THIS CHANGE IS MINIMAL

19. IN GMR METHOD, FERT AND GRUNBERG SANDWITCHRD A LAYER OF NON MAGNETIC METAL Cr A LAYER OF NON MAGNETIC METAL Cr BETWEEN THE TWO LAYERS OF MAGNETIC METAL IRON THESE LAYERS ARE A FEW NANOMETERS THICK ONLY The TECHNIQUQ USED IS MOLECULAR BEAM EPITAXY (IN EARLY 70S) LATER TECHNIQUES USED ARE SPUTTERING, LASER ABLATION AND CHEMICAL VAPOUR DEPOSITION

20. THE TWO MAGNETIC LAYERS ARE MAGNETISED IN THE SAME DIRECTION IN ONE CASE AND IN OPPOSITE DIRECTION IN ANOTHER CASE THE RESISTANCE TO FLOW OF ELECTRONS IN ANOTHER CASE THE RESISTANCE TO FLOW OF ELECTRONS THROUGH THE SANDWITCH WAS MUCH HIGHER IN THE SECOND CASE THA N IN THE FIRST THIS IS DUE TO ELECTRONS HAVING ANTI PARALLAL SPINS THIS DIFFERENTIAL FLOW OF CURREENT DUE TO OPPOSITE MAGNETIC FIELDS IS CALLED GMR

21. Grunsberg obtained a change of resistance of 10% WITH THREE LAYERS FERT CREATED A SANDWITCH OF30 LAYERS OF Fe AND OBSERVED A 50% CHANGE IN RESISTANCE IRON AND CHROMIUM HAVE MATCHING LATTICE PARAMETERS-fcc STRUCTURE Latest Co-Ge LAYERS ARE USED FOR TUNNELING MAGNETORESISTANCE ( TMR ) TMR TECHNOLGY IS ALREADY IN USE IN MAGNETIC ACCESS MEMORIES ( MRAM ) FOR LAPTOPS SOON TMR WILL REPLACE GMR ALSO THE DISCOVERY OF GMR HAS OPENED A NEW FIELD OF SCIENCE CALLAD MAGNETOELECTRONICS OS SPINTRONICS

23.   So what are the real risks - does nanotechnology pose a threat to human health or the environment?   Nanoparticles such as buckyballs and carb nanotubes are already with us - and one concern is that they might present different dangers to bulk versions of the same materials.   Some environmental groups are worried that these materials are now going into our bodies and the environment with little knowledge about their long-term effects.   Some groups have called for a moratorium on research until we know more.   While these nanoparticles might present a risk, we just do not know if we would ever be exposed to enough of them to cause harm

24.   Aside from the health risks, some commentators have expressed concern about the potential ethical and social effects the wider use of nanotechnologies might have on society.   For example nanotech could change the fundamental nature of what it means to be human. We may develop technologies to prolong our life, improve endurance or even make us a little bit smarter.