Nanotechnology and nanomaterial

copyright goes to Sir harshad patel sir,professor of institute of reserch and developement of nfsu gujrat

1. NANOTECHNOLOGY NANOMATERIAL http://primaxstudio.com/stuff/scale_of_universe/index.php

2. History of NANO • Tools 2,000,000 B.C. • Metallurgy 3600 B.C. • Steam power 1764 • Mass production 1908 • Automation 1946 • Sixth industrial revolution NOW – Moving from micrometer scale to nanometer scale devices

3. Milestone 1959 R. Feynman Delivers “ Plenty of Room at the Bottom” 1974 First Molecular Electronic Device Patented 1981 Scanning Tunneling Microscopic (STM) 1985 Fullerene 1986 Atomic Force Microscopy (AFM) Invented 1987 First single-electron transistor created 1991 Carbon Nanotubes Discovered 2000 US Launches National Nanotechnology Initiative 2002 INDIA NSNTI Centre Established

4. Macro structures are defined as visually observable and easily measurable sys-tems. Standards have been developed to determine the physical and chemical properties of parts or equipment with macro size. If the materials are structural load-carrying elements, the mechanical properties that define the behavior of the material under the load become very important. The priorities according to the material selection and characterization can be listed as follows: a)Durability b)Wear resistance c)Corrosion resistance d)High/low temperature resistance e)Ability to be shaped f)Compatibility with assembly techniques g)Appearance/brightness h)Biocompatibility

5. In the broadest sense, the term "technology" is defined as "application information covering the construction methods, tools, instrument and equipment used in an industry, and their ways of use" It can also be defined as all of the equipment, all the information pertaining to these devices, developed by humankind in order to facilitate life, speed up production, change existing structures and conduct research. This definition is expressed as nanotechnology if it is applied to a dimension that is defined as one billionth of meter. How did this adventure that can change from meter to millimeter, millimeter to micrometers, micrometers to nanometers had started? 1 m = 10 3 mm = 10 6 μm = 10 9 nm Keywords: Macro, Micro, Nano Abbrevisions: Meter (m), Milimeter (mm), Nanometer (nm)

6. What is Nanomaterial? One billion nanometers equals one meter i.e. 1000000000 nm = 1meter i.e. 1nm=10 -9 m Nanomaterials are commonly defined as materials with an average grain size less than 100 nanometers . i.e. structural features in between those of atoms and bulk materials. Properties of materials of nanometric dimensions are significantly different from those of atoms as well as those of bulk materials. New tools for characterization and manipulation

7. Nanotechnology… Nanotechnology is the study, design, creation, synthesis, manipulation, and application of functional materials, devices, and systems through control of matter and energy at the nanometer scale (1–100 nanometers, one nanometer being equal to 1 × 10 −9 of a meter). Exploitation of novel phenomena, including the properties of matter , energy , and information at the molecular, atomic, and sub atomic levels.

8. Nanotechnology? Nanotechnology is the creation of functional materials, devices and systems through control of matter on the nanometer length scale (1-100 nanometers ) and exploitation of novel phenomena and properties which arise because of the nanometer length scale: • Physical • Chemical • Electrical • Mechanical • Optical • Magnetic

9. Comparisons The average width of a human hair is on the order of 100,000 nanometers A single particle of smoke is in the order of 1,000 nanometers .

10. FACTOR ...or in full ... or in words SI  PREFIX SI  SYMBOL 1,0E+24 1,0E+21 1,0E+18 1,0E+15 1,0E+12 1,0E+9 1,0E+6 1,0E+3 1,0E+2 1,0E+1 1,0E-1 1,0E-2 1,0E-3 1,0E-6 1,0E-9 1,0E-12 1,0E-15 1,0E-18  1,0E-21 1,0E-24 1 000 000 000 000 000 000 000 000 1 000 000 000 000 000 000 000 1 000 000 000 000 000 000 1 000 000 000 000 000 1 000 000 000 000 1 000 000 000  1 000 000 1 000 100 10 0,1 0,01 0,001 0,000 001 0,000 000 001 0,000 000 000 001 0,000 000 000 000 001 0,000 000 000 000 000 001 0,000 000 000 000 000 000 001 0,000 000 000 000 000 000 000 001 septillion sextillion quintillion quadrillion trillion billion million thousand hundred ten tenth hundredth thousandth millionth  billionth  trillionth  quadrillionth quintillionth sextillionth septillionth yotta - zetta - exa - peta - tera - giga - mega- kilo- hecto - deca - deci - centi - milli - micro- nano- pico - femto - atto -  zepto - yocto - Y Z E P T G M k h da d c m µ n p f a  z y

11. SI prefixes Prefix Symbol 1000 m 10 n Decimal Short scale Long scale Since [n 1] Yotta Y 1000 8 10 24 1000000000000000000000000 Septillion Quadrillion 1991 Zetta Z 1000 7 10 21 1000000000000000000000 Sextillion Trilliard 1991 Exa E 1000 6 10 18 1000000000000000000 Quintillion Trillion 1975 Peta P 1000 5 10 15 1000000000000000 Quadrillion Billiard 1975 Tera T 1000 4 10 12 1000000000000 Trillion Billion 1960 Giga G 1000 3 10 9 1000000000 Billion Milliard 1960 Mega M 1000 2 10 6 1000000 Million 1960 Kilo K 1000 1 10 3 1000 Thousand 1795 Hecto H 1000 2/3 10 2 100 Hundred 1795 Deca Da 1000 1/3 10 1 10 Ten 1795 1000 10 1 One – Deci D 1000 −1/3 10 −1 0.1 Tenth 1795 Centi c 1000 −2/3 10 −2 0.01 Hundredth 1795 Milli m 1000 −1 10 −3 0.001 Thousandth 1795 Micro μ 1000 −2 10 −6 0.000001 Millionth 1960 Nano n 1000 −3 10 −9 0.000000001 Billionth Milliardth 1960 Pico p 1000 −4 10 −12 0.000000000001 Trillionth Billionth 1960 Femto f 1000 −5 10 −15 0.000000000000001 Quadrillionth Billiardth 1964 Atto a 1000 −6 10 −18 0.000000000000000001 Quintillionth Trillionth 1964 Zepto z 1000 −7 10 −21 0.000000000000000000001 Sextillionth Trilliardth 1991 Yocto y 1000 −8 10 −24 0.000000000000000000000001 Septillionth Quadrillionth 1991 ^ The metric system was introduced in 1795 with six prefixes. The other dates relate to recognition by a resolution of the CGPM .

12. Hindi (transliteration) Indian figure Power notation English figure Short scale English ( long scale English) एक ( ek) 1 10 1 one दस ( das) 10 10 1 10 ten सौ ( sau) 100 10 2 100 hundred सहस्र ( sahasra) / हज़ार ( hazaar) 1,000 10 3 1,000 one thousand लाख ( lakh / lac) 1,00,000 10 5 100,000 one hundred thousand करोड़ ( crore) 1,00,00,000 10 7 10,000,000 ten million अरब ( arab) 1,00,00,00,000 10 9 1,000,000,000 one billion (one milliard) खरब ( kharab) 1,00,00,00,00,000 10 11 100,000,000,000 one hundred billion (one hundred milliard) नील ( neel) 1,00,00,00,00,00,000 10 13 10,000,000,000,000 ten trillion (ten billion) पद्म ( padma) 1,00,00,00,00,00,00,000 10 15 1,000,000,000,000,000 one quadrillion (one billiard) शङ्ख ( shankh) 1,00,00,00,00,00,00,00,000 10 17 100,000,000,000,000,000 one hundred quadrillion (one hundred billiard) महाशङ्ख ( maha shankh / ald / udpadha) 1,00,00,00,00,00,00,00,00,000 10 19 10,000,000,000,000,000,000 ten quintillion (ten trillion) (ank / maha udpadha) 1,00,00,00,00,00,00,00,00,00,000 10 21 1,000,000,000,000,000,000,000 one sextillion (one trilliard) (jald / padha) 1,00,00,00,00,00,00,00,00,00,00,000 10 23 100,000,000,000,000,000,000,000 one hundred sextillion (one hundred trilliard) (madh) 1,00,00,00,00,00,00,00,00,00,00,00,000 10 25 10,000,000,000,000,000,000,000,000 ten septillion (ten quadrillion) (paraardha) 1,00,00,00,00,00,00,00,00,00,00,00,00,000 10 27 1,000,000,000,000,000,000,000,000,000 one octillion (one quadrilliard) (ant) 1,00,00,00,00,00,00,00,00,00,00,00,00,00,000 10 29 100,000,000,000,000,000,000,000,000,000 one hundred octillion (one hundred quadrilliard) (maha ant) 1,00,00,00,00,00,00,00,00,00,00,00,00,00,00,000 10 31 10,000,000,000,000,000,000,000,000,000,000 ten nonillion (ten quintillion) (shisht) 1,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,000 10 33 1,000,000,000,000,000,000,000,000,000,000,000 one decillion (one quintilliard) (singhar) 1,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,000 10 35 100,000,000,000,000,000,000,000,000,000,000,000 one hundred decillion (one hundred quintilliard) (maha singhar) 1,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,000 10 37 10,000,000,000,000,000,000,000,000,000,000,000,000 ten undecillion (ten sextillion) (adant singhar) 100,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,000 10 41 100,000,000,000,000,000,000,000,000,000,000,000,000,000 one hundred duodecillion (one hundred sextilliard )

13. Why Nanotech? A small science with a huge potential Nanotechnology exploits benefits of ultra small size, enabling the use of particles to deliver a range of important benefits… Small particles are ‘invisible’ : Transparent Coatings/Films are attainable Small particles are very weight efficient: Surfaces can be modified with minimal material. - By patterning matter on the nano scale, it is possible to vary fundamental properties of materials without changing the chemical composition

14. Let’s have a glance on how nanotechnology can impact our lives: Faster and more powerful computers, which consume less power. Modern computers have longer-lasting batteries . Circuits, which are made from carbon nanotubes, aim to maintain computer power. People get access to much faster, more accurate, and functional medical diagnostic equipment . Have you heard about the technology called “ Lab-on-a-chip ”, which enables testing in real time and speeds up delivery of urgent medical care? All nanomaterial surfaces, which are used for producing modern implants resist any kind of infection . Pharmaceutical products contain nanoparticles, which improve their absorption within our bodies. They are also used to deliver chemotherapy drugs to the affected cancer cells ( targetd drug delivery ). Nanotechnology helps to improve vehicle fuel efficiency . The vehicle parts which are made from nanocomposite materials are lighter, stronger, and more chemically resistant comparing to metal. Nanoparticles in fabrics are stain, water, and flame resistance . They do not increase such properties of fabrics as weight, thickness, or stiffness . ...

15. ... Water filters (15-20 nanometers) are able to remove all viruses and bacteria . This is an innovative cost-efficient water treatment systems. Many countries need urgently to get the quality of drinking water improved Carbon nanotubes make our sports equipment stronger and the weight of it lighter . Modern sunscreens , which are made from nanoparticles, absorb light more efficiently, including the dangerous ultraviolet range. Cosmetics industry suspend and encapsulate various ingredients into nanospheres and nanoemulsions. Specialists claim that they help increase their penetration into our skin. You might not know but many cosmetic products use nanomaterials in some forms. For example, L’Oreal has developed an anti-wrinkle cream , which contains polymer nanocapsules for better delivery of active ingredients into deeper layers of skin. Drink bottles are also made from plastics, which contains nanoclays. It gives good resistance to permeation by oxygen and moisture. In medicine, nanosensors help to identify particular cells/substances in the body. We start using cheap, lightweight solar plastics, which makes solar energy widely available. Nanoparticles can clean up toxic chemical spills, as well as air-borne pollutants. Specialists claim that nanomaterials may be used in space exploration.

16. Approaches • Top-down – Breaking down matter into more basic building blocks. Frequently uses chemical or thermal methods. • Bottoms-up – Building complex systems by combining simple atomic-level components.

17. Applications of Nanomaterials Nano materials or nano crystals provide large surface area. Hence they act as better catalysts. Tumors can be detected and located with incredible accuracy. Nano shells can float through the body attaching only to cancer cells. When excited by a laser beam, they give off heat and there by destroy tumor. Now borns will have their DNA mapped quickly. Nano technology will enable the delivery of right amount of medicines to the exact spot of the body. Nano technology can create biocompatible joint replacements and artery stents that will last life of the patients. Hence these need not be replaced every few years.

18. Extra bouncy tennis balls – Wilson Sporting Goods uses nano -size material to coat their Official Davis Cup Double Core ball.  The tiny particles form a molecular barrier that traps air molecules.  This method is being studied for use on tires. Transparent sunscreen – nanopowder absorbs sunlight, doesn’t appear white on your skin. Easy clean bathrooms – A thin film coating of transparent nanoparticles for bathroom surfaces, the dirt can’t get stick to it. Antibacterial dressings – Silver has been used for years as an antibacterial agent, but in a nanocluster form it kills bacteria faster and reduced inflammation. 

19. DIFFERENT KINDS OF NANOMATERIALS Nanomaterials are made from any major class of engineering materialdmetals, semiconductors, ceramics, organics, polymers, and even materials derived from living organisms that are considered to be “soft matter”. Nanocomposites containing nanomaterials incorporated into larger scale bulk materials can demonstrate superior mechanical, electrical, thermal, and optical properties. Within our synthetic domain, nanomaterials can be clas_x0002_sified as zero-dimensional (0D), one-dimensional (1D), or two-dimensional (2D) and the three-dimensional (3D) nano_x0002_material.

20. Zero-Dimensional and Larger SphericalNanomaterials Examples of 0D materials are QDsdspherical materials in which there is spatial (electron) confinement in the x, y, and z directions. In order to qualify as a QD,all three dimensions must be within the small end ofthe nanoscale. Physical properties of 0D materials are intermediate between those of the macroscopic form(continuous properties) and the molecular or even atomic forms (discrete properties). In other words, the physiochemical properties of 0D materials lie at the bulkequantum scale boundary. Larger particles such as colloids are not considered to be QDs per se but still exhibit remarkable properties due to extrinsic size factors, rather than intrinsic size factors that are due toquantum effects. QDs are usually made of metals,metal oxides, or semiconductor materials, although the fullerene C60 molecule is considered by some to be a QD.

21. One-Dimensional Nanomaterials 1D materials are called quantum wires. Materials designated as nanofibers, nanobelts, nanorods, and nanoribbons are considered to be 1D nanomaterials. Electron confinement for 1D materials is along the x and y transverse dimensions. Along the longitudinal axis of the wire, there is no electron confinement and the material can display bulk behavior. Carbon nanotubes are made purely of carbon atoms in a hexagonal configuration like graphite, rolled into a tube, and serve as a reasonably good example of a 1D nanomaterial. Physical properties such as heat transfer and electrical conductivity along the x and y transverse coordinates demonstrate confined (discrete) behavior.

22. Two-Dimensional Nanomaterials 2D nanomaterials are considered to be quantum wells, or in generic terms, as thin films. In 2D materials,there is electron confinement only in one direction. Ultrafine chitin nanofibers (CNFs) can be made into membrane structures when incorporated into biopolymers. Applications of CNF-biopolymers include serving as templates in tissue development and skin regeneration. Membranes, not necessarily of nanoscale thickness, have been applied successfully as transdermal drug delivery vehicles, an important mode of drug transport. CNF-reinforced chitosan films for use as wound medicaments showed enhanced healing ca_x0002_pacity due to the synergistic reaction between chitosan salts and the CNF

23. 3D Nanostructures Graphite structures, Crystals etc

24. Different types of Nanomaterial • Nanopowder – Building blocks (less than 100 nm in diameter) for more complex nanostructures. • Nanotube – Carbon nanotubes are tiny strips of graphite sheet rolled into tubes a few nanometers in diameter and up to hundreds of micrometers (microns) long. – The Strongest Material

25. Nanopowders • Advanced nanophase materials synthesized from nanopowders have improved properties. • Such as increased stronger and less breakable ceramics. They may conduct electrons, ions, heat, or light more readily then conventional materials. • Exhibit improved magnetic and catalytic properties.

26. Size-dependent properties • Surface to volume ratio - A 3 nm iron particle has 50% atoms on the surface - A 10 nm particle has 20% on the surface - A 30 nm particle has only 5% on the surface

27. Percentage of Surface Atoms

28. • Recently, there has been an explosion of research on the nanoscale behavior - Nanostructures through sub-micron self assembly creating entities from “bottom-up” instead of “top-down” - Characterization and applications - Highly sophisticated computer simulations to enhance understanding as well as create ‘designer materials’ • 1959 Feynman Lecture “There is Plenty of Room at the Bottom” provided the vision of exciting new discoveries if one could fabricate materials/devices at the atomic/molecular scale. • Emergence of instruments in the 1980s; STM, AFM providing the “eyes”, “fingers” for nanoscale manipulation, measurement… STM Image of Highly Oriented Pyrolytic Graphite Nano Revolution

29. Nanoelectronics and Related Structural Applications Sensors, NEMS Organic Inorganic Bio Materials Applications

30. Components

31. Examples of Nanomaterials Zinc Oxide Copper Oxide Aluminium Silver Carbon Nanotubes

32. Carbon Nanotubes - CNT SEM images. Diameter range: 5nm - 15 nm Carbon nanotubes are molecular-scale tubes of graphitic carbon. Their name is derived from their size, since the diameter of a nanotube is on the order of a few nanometers while they can be up to several millimeters in length .

33. Carbon Nanotubes Properties Everything changes at nanometer scale! Physical properties Applications Mechanical strength, toughness Chemical bonding, reactivity Thermal insulators, conductors Electrical conductivity Optical absorption, reflectivity high strength low weight composites chemical and biological sensors and receptors high power or high temperature application Microelectronics high bandwidth fibers or waveguides

34. The strongest and most flexible molecular material because of C-C covalent bonding Young’s modulus of over 1 TPa vs. 70 GPa for Aluminum, 700 GPA for C-fiber Maximum strain ~10% much higher than any material Carbon Nanaotubes Properties

35. Diodes and transistors for Computing Capacitors Data Storage Field emitters for instrumentation Flat panel displays CNT Application: Electronics

36. CNT based microscopy: AFM, STM… Nanotube sensors: force, pressure, chemical… Biosensors Molecular gears, motors Batteries, Fuel Cells: H 2 , Li storage Biomedical - Drug delivery - DNA sequencing - Artificial muscles, bone replacement, bionic eye, ear... Carbon nanotubes Application: Sensors, Bio Conventional silicon or tungsten tips wear out quickly. CNT tip is robust, offers amazing resolution.

37. CNT Interconnects CNT advantages: Small diameter Highly conductive along the axis High mechanical strength

38. 3+ 2+ e 3+ 2+ CNT DNA Sensor Using Electrochemical Detection Carbon nanotube array electrode functionalized with DNA/RNA probe as an ultrasensitive sensor for detecting the hybridization of target DNA/RNA from the sample.

39. Zinc Oxide Nanowires

40. Nanolasers . Light emission from a semiconductor nanowire-typically 10-100 nanometers wide and a few micrometers long-functions as a laser. Lasers made from arrays of these wires have many potential applications in communications and sensing

41. Macromolecule Nano-material

42. SEM & TEM Images of silica

43. Nano Chemistry is the study of materials of the size 1 to 100 nm rang e. Nanotechnology is the understanding and control of matter at dimensions of roughly 1 to 100 nm, where unique phenomena enable novel applications. 1 nm = 10 -9 = I billionth of a meter Limit of eye’s ability to see = 10,000 nm Diameter of Hair = 75,000 nm DNA width = 2 nm H-atom = 0.1 nm Bucky ball = 1 nm Carbon nanotube = 1.3 nm E. Coli bacteria = 2,000 nm

44. Bucky Ball

45. Classification Of Nanomaterials 1. Carbon Based Nanomaterials 2. Nano Composites 3. Metals & Alloys 4. Biological Nanomaterials 5. Nano -Polymers 6. Nano -Glasses 7. Nano -Ceramics

46. Carbon Based Nanomaterials The materials in which the “ Nanocomponent ” is pure carbon. Example: Carbon Nanotubes (CNT) are sheets of graphite rolled up to make a tube. Due to the large surface area, CNT are interesting media for electrical energy storage. The excellent electrical and mechanical properties of carbon nanotubes like electrical conductivity, heat transmission capacity. Heat stability, high strength or low density make them good candidates for use as fillers and many other applications. Carbon nanotubes and polymers can form foams. Carbon black is currently the most widely used carbon nanomaterial, it has found application in car tyres, antistatic textiles and is used for colour effects.

47. Nano polymers Nano polymers are nano structured polymers. This occurs during polymerization, in which many monomer molecules link to each other. Polymerization

48. Cytochrome C is a globular protein with 104 amino acids in one protein chain and an iron-containing heme group. Biological nanomaterials

49. Carbon Nano tubes A carbon nanotube is a structure which seems to be formed by rolling a sheet of graphite into the shapes of a cylindrical tube. Nanotubes are categorized as single-walled nanotubes (SWNT) and multi-walled nanotubes (MWNT). Single-walled nanotubes have a diameter of close to 1 nm, with a tube length that can be many millions of times longer. The structure of a SWNT can be conceptualized by wrapping a one-atom-thick layer of graphite called graphene in to a seamless cylinder. Multi-walled carbon nanotubes consist of multiple concentric nanotube cylinders. Based on the orientations of lattices, nanotubes are of three different types-Armchair, Zigzag and Chiral.

50. High pressure carbon monoxide deposition CO C + O C + C Carbon Nanotube High pressure Temperature, Fe Fe-cluster CO C + O C + C + C

51. In this method, carbon monoxide gas and small clusters of iron atoms are heated in chamber under pressure. Carbon monoxide molecules settle on iron clusters and breaks in to carbon and oxygen atoms. Iron acts as catalyst for breaking CO. One carbon atom binds with other carbon atom to start the nanotube lattice. Oxygen atoms give carbon dioxide (CO 2 ) with CO.

52. 2. Chemical Vapour Deposition CH 4 C + 2 H 2 Iron catalyst Heat CH 4 C + 2H 2

53. In this method, a hydrocarbon like methane is led in to a heated chamber containing a subtract coated with iron catalyst. Due to high temperature in the chamber C-H bonds breaks and carbon atoms are formed. They bind together forming carbon nanotubes.

54. 3. Plasma process In this method methane gas which is the source of carbon is passed through a plasma torch. Carbon atoms formed combine to form carbon nanotubes.

55. Properties of Carbon Nanotubes Carbon nanotubes are very strong. Their tensile strength is 100 times greater than that of steel of the same diameter. Young’s modulus is about 5 times higher than for steel. They have high thermal conductivity-more than 10 times that of silver. They conduct electricity better than metals. Electron travelling through a carbon nanotube behaves like wave travelling through a smooth channel. This movement of electrons within a nanotube is called “ballistic transport”. They are light weight, density about one fourth of steel. They are sticky due to Van der Waal’s force of attraction.

56. Applications of Carbon Nanotubes They are strengtheners of composite materials. They act as molecular size test tubes or capsules for drug delivery Depending on their size, they act as electrical conductors or semiconductors. They are used as tips for analysis of DNA and proteins by atomic force microscopy.

57. Nanomaterials as Catalysts Physical, chemical and biological properties of materials differ with respect to the individual atoms or molecules present in the material or the size of fundamental particle. Nanomaterials based catalysts are usually heterogeneous. Because of the small size of the particles, it can give maximum surface area exposed to reactant, allowing more reactions to occur. Macromolecule Nano particle

58. Some famous catalysts TiO 2 , ZrO 2 , Al 2 O 3

59. STM image of a quantum corral of 48 Fe atoms placed in a circle of 7.3 nm [IBM Research].

60. Various Nanomaterials and Nanotechnologies • Nanocrystalline materials • Nanoparticles • Nanocapsules • Nanoporous materials • Nanofibers • Nanowires • Fullerenes • Nanotubes • Nanosprings • Nanobelts • Dendrimers • • Molecular electronics • Quantum dots • NEMS Nano-optics • Nanomagnetics • Nanofabrication • Nanolithography • Nanomanufacturing • Nanomedicine • Nano-biomaterials • •

61. Weight efficient and Uniform coverage • Large spherical particles do not cover much surface area • Nanoparticles Equal mass of small platelet particles provides thorough coverage (1 x 10 6 times more)

62. Surface to Bulk Atom Ratio • Spherical iron nanocrystals •

63. Size Dependence of Properties • In materials where strong chemical bonding is present, delocalization of valence electrons can be extensive. The extent of delocalization can vary with the size of the system. • Structure also changes with size • The above two changes can lead to different physical and chemical properties, depending on size - Optical properties - Bandgap - Melting point - Specific heat - Surface reactivity - - • Even when such nanoparticles are consolidated into macroscale solids, new properties of bulk materials are possible. - Example: enhanced plasticity

64. Size effect Two types.. Relatively larger nanostructures Specific size effects (e.g. magic numbers of atoms in metal clusters, quantum mechanical effects at small sizes)

65. In a metal, the quasi-continuous density of states in the valence and the conduction bands splits into discrete electronic levels, the spacing between these levels and the band gap increasing with decreasing particle size In the case of semiconductors, the phenomenon is slightly different, since a band gap already exists in the bulk state. However, this band gap also increases when the particle size is decreased and the energy bands gradually convert into discrete molecular electronic levels. Size quantization effect. Electronic state transition from bulk metal/semiconductor to small cluster.

66. What Are Quantum Dots? QDs are the class of materials in which quantum confinement effects can be evidenced. They are very small semiconductor crystals on the order of nanometer size, containing merely a hundred to a thousand atoms. As a result, they tightly confine electrons or electron-hole pairs called “excitons” (explained in the next section) in all three dimensions. QDs are a subgroup in the family of nanomaterials, which comprises metals, insulators, semiconductors, and organic materials. Specifically, the term “quantum dot” refers only to semiconductor nanocrystals, whereas any other inorganic material in the nano regime is referred to as a “nanocrystal.”

67. QDs exhibit electronic properties intermediate to those of bulk semiconductors and isolated molecules. The optoelectronic properties are determined by their size and shape and alter as a function of these variables. For example, when QDs are excited by a photon of energy hν (where ν is the frequency of the incident photon) those of comparatively larger size, at around 5–6 nm, emit energy in the wavelength of orange or red. The smaller QDs emit shorter wavelengths in the blue or green range. As a consequence, these properties can be specifically tuned to have a desired output by altering the dot size and shape.

68. Fig. illustrates the variation in the bandgap of QDs as size varies. QDs can be made from single-element materials, such as silicon or germanium, or from compound semiconductors, such as CdSe, PbSe, CdTe, and PbS. QDs are also sometimes referred to as “artificial atoms,” as these materials exhibit discrete electronic states as seen in atoms and molecules.

69. Because of their unique properties, QDs find applications in many fields, including solar cells, LEDs, transistors, displays, laser diodes, quantum computing, and medical imaging. Particularly, QDs are significant for optoelectronic applications due to their precisely tunable bandgap and emission color. QDs are expected to deliver very high-efficiency solar cells, and have also proved to be superior to traditional organic dyes used in modern biological analysis.

70. If the particle size is less than the De Broglie wavelength of the electrons, the charge carriers may be treated quantum mechanically as "particles in a box", where the size of the box is given by the dimensions of the crystallites. In semiconductors, the quantization effect that enhances the optical gap is routinely observed for clusters ranging from 1 nm to almost 10 nm. Metal particles consisting of 50 to 100 atoms with a diameter between 1 and 2 nm start to loose their metallic behaviour and tend to become semiconductors. Particles that show this size quantization effect are sometimes called Q-particles or quantum dots

71. Size dependence of the melting temperature of CdS nanocrystals

72. Applications and Technology Development ( i ) Production of nanopowders of ceramics and other materials, (ii) nanocomposites, (iii) development of nanolectrochemical systems (NEMS), (iv) Applications of nanotubes for hydrogen storage and other purposes, (v) DNA chips and chips for chemical/biochemical assays, (vi) gene targeting/drug targeting and (vii) nanoelectronics and nanodevices . The last one, which is probably the most challenging area, includes new lasers, nanosensors , nanocomputers (based on nanotubes and other materials), defect-free electronics for future molecular computers, resonant tunnelling devices, linking of biological motors with inorganic nanodevices .

73. Nanoelectronics The multidisciplinary area of nanoelectronics has two objectives: ( i ) utilization of a single nanostructure (e.g. nanocrystal , quantum dot, nanotube) for processing electrical, optical or chemical signals, and (ii) utilization of nanostructured materials involving assemblies of nanostructures for electronic, optoelectronic, chemical and other applications. While it is often difficult to make distinctions between the two, the first category is specifically intended to obtain single-electron devices and the second category is for the purpose of miniaturization in information storage

74. Other Aspects Consolidated nanostructures employing both ceramic and metallic materials are considered important in creating new generations of ultrahigh-strength, tough structural materials, new types of ferromagnets , strong and ductile cements, and new biomedical implants. Typical of the nanostructured hard materials are Co/WC and Fe/ TiC nanocomposites. Nanoparticle -reinforced polymers are being considered for automotive parts. Besides high strength materials, dispersions and powders as well as large bodies of novel morphologies are being produced. Coatings with highly improved features resulting from the incorporation of nanoparticles are being developed.

75. Nano electro mechenical systems (NEMS) are likely to augment the already established micro analogue, MEMS. A related aspect pertains to molecular motors. Molecular motors are responsible for DNA transcription, cellular transport and muscle contraction. It can be used in artificial biological devices that are powdered by ATP. Organic chemists are synthesizing molecules (e.g., rotaxanes ) capable of various kinds of motions at the nanolevel . Using molecular motors as nanomachines and interfacing them with inorganic energy sources and other nanodevices would be of great interest.

76. DNA chips and microarrays represent a technology with applications in diagnostics and genetic research. DNA chips and arrays are devices wherein different DNA sequences are arrayed on a solid support, the arrays generally having 100 to 100,000 different pixels (DNA sites) on the chip surface. The chips will be useful in genomic research, drug discovery, forensics and different types of detection and diagnostics. Electronically active DNA microarrays and electronically directed DNA self-assembly technology could be of value in photonic and electronic devices and other areas.

77. Semiconductor nanocrystals are being used as fluorescent biological labels. sensors based on nanotechnology will revolutionize health care, climate control and detection of toxic substances. nanochips to carry out complete chemical analysis. Such nano-total analysis systems will have to employ new approaches to valves, pipes, pumps, separations and detection. the use of nanoparticles of TiO2 and other nanomaterials for environmental cleansing processes and of nano-porous solids for sorption, are examples of the applications of nanotechnology for the protection and improvement of the environment. The use of nanoporous polymers for water purification and purification of liquids by photocatalysis of nanoparticles of TiO2 are two other examples.