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Nano means ‘dwarf ‘in Greek Nano = 1 billionth 1nm = 10 -9 m smallest thing visible to human eye; 10,000nm diameter Nano world – world of atoms and molecules.

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Presentation on theme: "Nano means ‘dwarf ‘in Greek Nano = 1 billionth 1nm = 10 -9 m smallest thing visible to human eye; 10,000nm diameter Nano world – world of atoms and molecules."— Presentation transcript:

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2 Nano means ‘dwarf ‘in Greek Nano = 1 billionth 1nm = m smallest thing visible to human eye; 10,000nm diameter Nano world – world of atoms and molecules

3 How big is that?

4 Nanotechnology is the manipulation of matter on an atomic and molecular scale Materials, devices, and other structures with at least one dimension sized from 1 to 100 nanometres Nanoparticles: one of the dimensions is less than 100nm Eg: DNA (2.5nm), Hb (6.5nm), viruses (10-100nm) Nanostructures: at least one dimension roughly between 1nm and 100nm Exhibit novel physical, chemical and biological properties

5 Nanotechnology: fabrication of nanostructures Create new materials, machines, and devices to change the mode of our living and work Deliberate design, construction, characterization and utilization of functional structures, devices and systems through the control of matter at nanometre dimensions. Design, assemble and build well defined intricate structures by putting atoms or molecules at predesigned position using direct mechanical control & extended to even macroscopic scales Aim: to learn to exploit the exceptional properties of nanostructures

6 Professor Geoffrey Ozin (University of Toronto).Geoffrey OzinUniversity of Toronto

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8 The Lycurgus Cup is a 4th-century Roman glass cage cup made of a dichroic glassRoman glass cage cupdichroic glass red when lit from behind and green when lit from in front The dichroic effect is achieved by making the glass with tiny proportions of nanoparticles of gold and silver "dispersed" (the technical term in chemistry) in colloidal form throughout the glass materialnanoparticlescolloidal The particles are only about 70 nanometers acrossnanometers Dichroic glass: glass containing multiple micro-layers of metals or oxides which give the glass dichroic optical properties.glassdichroic It has a particular transmitted color and a completely different reflected color

9 Nanofabrication: preparation of nanomaterials Top-down method  Offers reliability of the product  Involve high energy usage

10 Bottom-up method 1.Positional assembly  Move atom one by one into required specific arrangement using nanoprobe of an AFM  Allows control over individual atom during construction  Laborious, time cosuming, get few grams of matreial  Not used to create complex nanostructures

11 Bottom-up method 2. Self-assembly  Atoms and molecules spontaneously arrange themselves into final product  Preferred method for making large nanostructure arrays like computer memories  Advantage: Assemble large structures Eg:- Crystal growth carried out for semiconductor industry chemical synthesis of nanomatrerials

12 AFM

13 Quantum size effect As the system size approaches quantum mechanical length (nano), there is a modification of the properties of the system ie: the properties of nanostructured materials are different from that of corresponding bulk materials

14 A metal with bulk properties is reduced to a nanostructure size of the metallic particle < de Broglie wavelength of electrons Boundaries of the particle confine the electrons into a localized state: Particle in 1D box – Quantum confinement Material does not exhibit bulk metallic behaviour: most of the electrons are tightly bounded or localized –quantum size effect Electronic and optical properties are tunable via particle size

15 Classification of inorganic nanomaterials A)Commercial classification B) Based on nanoscale dimensionality 1. Carbon based 2. Metal based 3. Dendrimers 4. Nanocomposites

16  Carbon based nanomaterials Composed of carbon Hollow spheres, ellipsoid – fullerenes Tubes – carbon nanotubes  Metal based nanomaterials Metals in nano scale range (nanoAu, nanoAg, …), Metal oxide nanopowders (SiO 2, TiO 2, Al 2 O 3, Fe 3 O 4, Fe 2 O 3 ) Semiconductor nanocrystals or quantum dots (CdTe, GaAs, etc)

17  Dendrimers Nanosize polymers built from branched units Tree-like structure Interior: cavities and surface: numerous chain ends Tailored for a specific chemical function Applications: Drug delivery, Gene Delivery, Sensors, Blood substitution, nanoparticles eg:-Poly(propylene imine)

18  Nanocomposites Composites: materials made from two or more constituent materials with significantly different physical or chemical propertiesmaterialsphysicalchemical properties produce a material with characteristics different from the individual components Two components: Matrix & Reinforcing filler Matrix: polymers,metals and ceramics, cement Filler: Fiber, metals, polymers asphalt concrete bitumen

19 At least one of the components in nanoscale range exhibit overall best properties of each component Reinforcing phase has exceptionally high surface to volume ratio and/or its exceptionally high aspect ratio aspect ratio: ratio of the width of a shape to its height  Nanocomposites

20 Behavior dependent on: – properties of components – Interaction between them – Distribution of filler on matrix Nanofillers: nanosized clays, carbon fibers, CNT, fullerenes, metalsetc. Applications: nonlinear optics, batteries, sensors, catalysis  Nanocomposites

21 Fullerenes Molecule composed entirely of pure carbon in the form of a hollow sphere, ellipsoid, sphereellipsoid Spherical fullerenes are also called buckyballs Discovered (1985) by Richard Smalley, Robert Curl, and Harold Kroto ( 1996 chemistry Nobel Prize)Richard SmalleyRobert CurlHarold Kroto Carbon-60 (C 60 ) : Buckminster fullerene Diameter: 1nm 20 hexagons & 12 pentagons C 70, C 76, C 80, etc - fullerenes Applications: Ball bearings, drug delivery vehicles, in electronic circuits. Richard Buckminster Fuller

22 B) Based on nanoscale dimensionality Based on the number of dimensions which lie within the nanoscale 1.Nanosystems confined in one dimension – Materials with 1 dimension within the nanoscale range (thickness) – Extended in other two dimensions – nanolayers – Thin films, surface coatings

23 2. Nanosystems confined in two dimensions – 2 dimensions are in the nano scale range - Width & thickness – Nanowires & nanotubes – Nano wires: ultra fine wires or linear array of dots – Depending upon the starting materials- different optical, electronic and mechanical properties – Applications: electronics, sensors, optical components & displays, polymer composites. – Eg: semiconductor wires fromsilicon, gallium notride, indium phosphide, …. 1.Nanosystem confined in three dimension

24 Nanotubes – Tubular carbon nano structures (diameter is in nanoscale) – Eg: Carbon nanotubes Carbon nanotubes  discovered by Sumio Iijima (1991) with the help of an electron microscope  Just like rolled graphene sheets  C- sp 2 hybridisation  some are closed at one or both the ends and some are open  Closed tubes: caps are pentagon lattices 

25  Each C-atom bonded to other three – hexagonal lattice  Two types: single walled & Multi walled  Armchair  Chiral  Zig zag

26 Synthesis of CNTs  Arch discharge methode – 1 st successful method for small scale production – graphote anode (6mm) & cathode(9mm) placed in an inert environment (He/ Ar at 500mm Hg) – Strong current (~100A) passed between anode & cathode – Produce an electric arc that evaporates the C-atoms of graphite – The C-atoms condense on the surface of the electrodes and results in NTs – Fe or Co catalyst – SWNT – No catalyst -- MWNT

27  Laser Ablation method (1995)  carbon is evaporated at high temp. from graphite target using powerful & focused laser beam  Nts are collected on a cooled substrate at the end of the chamber 1.25cm 2.5cm 50 cm 99.99% Ar 500mm Hg Quartz tube Graphite target Furnace temp—1200 o C laser frequency- 10Hz

28  Chemical vapour deposition (CVD)  catalyst such as Ni or Fe is deposited onto substrate (porous alumina or quartz)surface by thermal evaporation  Hydrocarbons (ethylene, acetylene) or CO is pumped slowly into the reactor at furnace temp of 500 – 1200 o C  Carbon dissociate from the feedstock & diffuses onto the catalyst  Atoms arrange themselves into nanotubes on the substrate

29 Nanosystems confined in three dimensions o All the three dimensions in nanoscale range o Metal & metal oxide nano particles, quantum dots, fullerenes, dendrimers Quantum dot : nanocrystals of semiconductor materials Small enough to display quantum mechanical properties in electronic & optical processes Quantum confined in 3 diensions Applications: in transistors, solar cells, LED, and diode lasers. due to their excellent fluorescent properties used as fluorescent probe in biomolecular & cellular imaging

30 Properties of CNTs  Mechanical properties Very high mechanical strength & tough Flexible & elastic Light weight (density 1/4 th of steel) Tensile Strength >100 times that of steel Young’s modulus > 5 times that of steel

31  Conductivity Thermal & electrical conductors (thermal conductivity >10 times that of Ag) Conductivity varies with diameter & helicity of the tube lattice Slight change in these parameters can cause a shift from metallic to semiconducting state

32 Applications of CNTs Reinforced fillers in nanocomposites, sensors, nanoelectronics & high resolution display devices Quantum wires from CNTs carrying electricity 1000s of miles at faster rate and more economically Negligible energy loss: Superior heat conductance & nanoscale properties Replace Si (semiconducting channel) in Field Effect Transistors : CNT- FET High current carrying capacity & structural & thermal stability: Used as interconnect in IC in place of Cu

33 Nano fibers

34 Oxide nanoparticles Preparation Spray drying Precipitation Sol-gel process

35 Q A nanowire is a nanostructure, with the diameter of the order of a nanometer (10 −9 meters). It can also be defined as the ratio of the length to width being greater than 20. Alternatively, nanowires can be defined as structures that have a thickness or diameter constrained to tens of nanometers or less and an unconstrained length. At these scales, quantum mechanical effects are important — which coined the term "quantum wires". Many different types of nanowires exist, including metallic (e.g., Ni, Pt, Au), semiconducting (e.g., Si, InP, GaN, etc.), and insulating (e.g., SiO 2, TiO 2 ). Molecular nanowires are composed of repeating molecular units either organic (e.g. DNA) or inorganic (e.g. Mo 6 S 9-x I x ). nanometersquantum wiresNiPtAuSiInPGaN SiO 2TiO 2Molecular nanowiresDNA

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