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1 Introduction to Nanotechnology Prof.P. Ravindran, Department of Physics, Central University of Tamil Nadu, India & Center for Materials Science and Nanotechnology, University of Oslo, Norway http://folk.uio.no/ravi/cutn/teaching.html P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 2 What is nanotechnology? Nanotechnology is the ability to create and manipulate atoms and molecules on the smallest of scales. ‘Nano’ comes from the Greek word for dwarf. A nanometer (nm) is one-billionth of a metre, smaller than the wavelength of visible light and a hundred-thousandth the width of a human hair. Nanotechnology deals with anything measuring between 1 and 100 nm. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 3 Nanoworld Nano means ‘dwarf ‘in Greek Nano = 1 billionth 1nm = 10-9m smallest thing visible to human eye; 10,000nm diameter Nano world – world of atoms and molecules in nanoscale P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 How big is that? P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 4 5 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 P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 6 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 P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 The Scale of Things -- Nanometers and More Things Natural 7 Things Manmade 10-2 m 1 cm 10 mm Head of a pin 1-2 mm Ant ~ 5 mm Dust mite 200 mm 10-4 m Fly ash ~ 10-20 mm The Microworld Human hair ~ 10-50 mm wide 1,000,000 nanometers = 1 millimeter (mm) Microwave 10-3 m 10-5 m 0.01 mm 10 mm O -6 Red blood cells Pollen grain 1,000 nanometers = 1 micrometer (mm) Visible 10 m ATP synthase 10-8 m 0.1 mm 100 nm 0.01 mm 10 nm 10-9 m P O O O O O O O O O O O O O O O O O O O O O O S S S S S S S S Zone plate x-ray “lens” Outermost ring spacing ~35 nm Combine nanoscale building blocks to make novel functional devices, e.g., a photosynthetic reaction center with integral semiconductor storage Ultraviolet The Nanoworld 10-7 m ~10 nm diameter 21st Century Challenge 0.1 mm 100 mm Infrared Red blood cells with white cell ~ 2-5 mm MicroElectroMechanical devices 10 -100 mm wide Nanotube electrode Nanotube transistor Soft x-ray 1 nanometer (nm) DNA ~2-1/2 nm diameter Atoms of silicon spacing ~tenths of nm 10-10 m 0.1 nm Quantum corral of 48 iron atoms on copper surface positioned one at a time with an STM tip Corral diameter 14 nm Carbon nanotube ~2 nm diameter Office of Basic Energy Sciences Office of Science, U.S. DOE Version 03-05-02 8 Introduction Concept of sizes 1 nm = 10 -9 m (one billionth) length of linear chain consisting of 10 H atoms or 5 Si atoms P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 9 What is Nanotechnology? Nanotechnology can be defined as being concerned with materials and systems whose structures and components exhibit novel and significantly improved physical, chemical and biological properties, phenomena and processes due to their nanoscale size. For example, new properties of nanomaterials include low melting points or high catalytical activity etc. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 Richard P. Feynman http://www.feynmanonline.com/ The Feynman Lectures on Physics “There is plenty of room at the bottom.” December, 1959, exposition of just how much might be achieved by focusing on the enormous gap between the nano world and the big world. •This talk was a social function—an after dinner talk. •Replication of machines, each smaller than parent. •Information on head of pin and in head of pin. Who knows the word “pin”? P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 10 11 1/16”=1.5875 mm = 1,587,500 nm =15,875,000 Å 1/32”=0.79375 mm =793,750 nm =7,937,500 Å Pin head volume: 1.6 × 1018 Å3 Age of universe in seconds: ~3 x 1017 P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 12 Visual approach: simply shrink the text. This requires the text to be reduced by 25,000 times. Each letter then would then be several tens of atoms large. “…there is no question that there is enough room on the head of a pin to put all of the Encyclopedia Britannica.” P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 Nonomaterial Nanotechnology is the production of functional materials and structures in the range of 0.1 to 100 nanometers physical or chemical methods One hydrogen atom is 0.1 to 0.2 nm and of a small bacterium about 1,000 nm 13 Nanotechnologies are predicted to revolutionize: (a) the control over materials properties at ultrafine scales; and (b) the sensitivity of tools and devices applied in various scientific and technological fields. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 Nanomaterials It studies materials with morphological features on the nanoscale, and especially those that have special properties stemming from their nanoscale dimensions. A bulk material should have constant physical properties regardless of its size, At the nanoscale this is often not the case. Size- dependent properties are observed such as quantum confinement in semiconductor particles, and superparamagnetism in magnetic materials, etc.. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 14 Example The bending of bulk copper (wire, ribbon, etc.) occurs with movement of copper atoms/clusters at about the 50 nm scale. Copper nanoparticles smaller than 50 nm are considered super hard materials that do not exhibit the same malleability and ductility as bulk copper. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 15 16 Classifications of Nanotechnology-1 According to the growth media, Vapor phase growth includes laser reaction pyrolysis for nanoparticle synthesis and atomic layer deposition (ALD) for thin film deposition Liquid phase growth includes colloidal processing for the formation of nanoparticles and self-assembly of monolayers Solid phase growth includes phase segregation to make metallic particles in glass matrix and two-photon-induced polymerization for the fabrication of three-dimensional photonic crystals Hybrid growth includes vapor-liquid-solid (VLS) growth of nanowires P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 17 Classifications of Nanotechnology-2 According to the form of products, Nanoparticles by means of colloidal processing, flame combustion and phase segregation Nanorods or nanowires by template-based electroplating, solution-liquid-solid growth (SLS), and spontaneous anisotropic growth Thin films by molecular beam epitaxy (MBE) and atomic layer deposition (ALD) Nanostrucutred bulk materials including photonic bandgap crystals by self-assembly of nanosized particles P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 18 Femme Nanotechnology: BIG picture Nanooptics Nanomagnetism Nanotechnology covers various research areas fields contributing to nanotechnology development P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 19 Properties of Nano Greatly increased surface area per unit mass Changes chemical reactivity Changes in surface charge Modified electronic characteristics (RCEP 2008) P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 20 Nano Gold Lycurgus Cup (4th century AD), 165mm tall, with decorations in very intense red color achieved by gold and silver nanoparticles contained in the glassy phase. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 21 P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 22 The Lycurgus Cup is a 4th-century Roman glass cage cup made of a dichroic 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 material. The particles are only about 70 nanometers across Dichroic glass: glass containing multiple micro-layers of metals or oxides which give the glass dichroic optical properties. It has a particular transmitted color and a completely different reflected color P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 23 P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 24 Emergence of Nanotechnology-1 What’s not new? The study of biological systems and the engineering of many materials such as colloidal dispersions, metallic quantum dots, and catalysts have been in the nanometer regime for centuries. Thousand years ago, Chinese used Au nanoparticles as an inorganic dye to introduce red color into ceramic porcelains. In 1857, Faraday prepared Au colloids that was stable for almost a century before being destroyed during World War II. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 25 Emergence of Nanotechnology-2 What’s new? Our ability to image, engineer, and manipulate systems in the nanometer scale and understanding of atomic scale interactions. e.g. Discovery of STM, SPM, AFM techniques P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 Moore’s Law 26 Development of nanotechnology is driven at least partly by the ever shrinking of devices in the semiconductor industry and supported by the availability of characterization manipulation techniques in the nanometer level. 50 nm 1-5 nm 1950 1960 Dimensions of transistors halves every 18 months 1M Transistors per chip 1μm 1 st integrated circuit Moore’s Law Trend Line 1 st transistor Transistor Size 1 cm 1970 1980 1990 2000 2010 2020 P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 and 27 Capability of Nanotechnology High Strength Material (>10 GPa) Autonomous Spacecraft (40% less mass) Bio-Inspired Materials and Processes Multi-Functional Materials Revolutionary Aircraft Concepts (30% less mass, 20% less emission, 25% increased range) Reusable Launch Vehicle (20% less mass, 20% less noise) Adaptive SelfRepairing Space Missions P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 28 Then there are dreams… Library of Congress • • • • Library of Congress inside a sugar cube Bottom-up manufacturing Materials (100x) stronger but lighter than steel Speed and efficiency of computer chips & transistors • Nano contrast agents for cancer cell detection • Contaminant removal from water & air • Double energy efficiency of solar cells P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 Library of Congress? 29 Carbon Nanotubes (CNTs) CNTs can span 23,000 miles without failing due to its own weight. CNTs are 100 times stronger than steel. Many times stiffer than any known material Conducts heat better than diamond Can be a conductor or insulator without any doping. Lighter than feather. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 30 Nanomaterials Applications There are a number of products available that are already benefiting from nanotechnology. Using sunscreen as an example, many of them contain nanoparticles of zinc oxide or titanium oxide. Older sunscreen formulas use larger particles, which is what gives most sunscreens their whitish color. Smaller particles are less visible, so when the sunscreen is rubbed into the skin, it doesn't leave a whitish tinge. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 31 Other applications include: • • • • • • mobile phone touch screens; cosmetics; tennis rackets; bicycles; fabric; computer technology. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 32 ‘Nano’ foods now All foods contain nanoparticles. Examples of foods that contain nanoparticles include milk and meat. Milk contains caseins, a form of milk protein present at the nanoscale. Meat is made up of protein filaments that are much less than 100nm thin. The organisation and change to the structures of these affects the texture and properties of the milk or meat. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 Uses for nanotechnology in food Food packaging applications e.g. plastic polymers containing or coated with nanomaterials for improved mechanical or functional properties; Nanocoatings on food contact surfaces for barrier or antimicrobial properties; Nano-sized agrochemicals (a chemical used in agriculture, such as a pesticide or a fertilizer.); Nanosensors for food labelling. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 33 34 Nanofood examples Nanoparticles are being used to deliver vitamins or other nutrients in food and drinks without affecting the taste or appearance. These nanoparticles encapsulate the nutrients and carry them through the stomach into the bloodstream. Nanoparticle emulsions are being used in ice cream and various spreads to improve the texture and uniformity. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 35 Nanofood examples New developments in nanoscience and nanotechnology will allow more control and have the potential of increased benefits. These include: • • • • healthier foods (e.g. lower fat, lower salt) with desirable sensory properties; ingredients with improved properties; potential for removal of certain additives without loss of stability; smart-aids for processing foods to remove allergens such as peanut protein. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 36 Nano-packaging examples Researches have produced smart packages that can tell consumers about the freshness of milk or meat. When oxidation occurs in the package, nanoparticles indicates the colour change and the consumer can see if the product is fresh or not. Incorporation of nanoparticles in packaging can increase the barrier to oxygen and slow down degradation of food during storage. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 37 Nanopackaging examples Bottles made with nanocomposites minimise the leakage of carbon dioxide out of the bottle. This increases the shelf life of fizzy drinks without having to use heavier glass bottles or more expensive cans. Food storage bins have silver nanoparticles embedded in the plastic. The silver nanoparticles kill bacteria from any food previously stored in the bins, minimising harmful bacteria. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 1959: Richard P. Feynman; Plenty of room at the bottom As soon as I mention this, people tell me about miniaturization, and how far it has progressed today. They tell me about electric motors that are the size of the nail on your small finger. And there is a device on the market, they tell me, by which you can write the Lord's Prayer on the head of a pin. But that's nothing; that's the most primitive, halting step in the direction I intend to discuss. It is a staggeringly small world that is below. In the year 2000, when they look back at this age, they will wonder why it was not until the year 1960 that anybody began seriously to move in this direction. Why cannot we write the entire 24 volumes of the Encyclopedia Brittanica on the head of a pin? He discussed a "great future" in which "we can arrange the atoms the way we want." Feynman's "great future" arrived in 1989 with the discovery of ways to manipulate atoms with the Scanning Tunneling Microscope. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 38 39 Nano in nature Gecko feet are covered with nano-size hairs that use intermolecular forces, allowing the lizards to stick firmly to surfaces. By replicating this scientists have developed an adhesive that can seal wounds or patch a hole caused by a stomach ulcer. The adhesive is elastic, waterproof and made of material that breaks down as the injury heals. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 40 Ultra‐sticky Feet From Nature: Geoko Number Of Spatula In A Foot ~1 Billion Intermolecular Force Is Resposible For The Strong Binding With Surfaces A Gecko Can Lift 130 Kg Weigth SPATULA P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 41 Gecko feet: biology Millions of hairs called setae Fiber radius is nanometer-scale Adhesion due to van der Waals and capillary forces P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 42 From Nature: Peacock Feathers NANOPHOTONIC CRYSTALS P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 43 Applications of nanotechnology Agriculture Processing Products Nutrition New pesticides Microencapsulation of flavours/aromas UV protection Neutraceuticals Genetic engineering Gelation agents Antimicrobials Nutrient delivery Identity preservation Nano emulsions Condition and abuse monitors Mineral/vitamin fortification Sensors to measure soil conditions Anti-caking High barrier plastics Drinking water purification Sanitation of equipment Security/anti counterfeiting Sensory characteristics of supplements Contaminant sensors P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 44 The future of nanotechnology in Food Research is being carried out to develop nanocapsules containing nutrients that would be released when nanosensors detect a deficiency in your body. Nanomaterials are being developed to improve the taste, colour, and texture of foods. For example “interactive” foods are being developed that would allow you to choose which flavour and colour a food has! P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 Nanoscience and Nanotechnology The nanoscale is not just another step towards miniaturization. It is a qualitatively new scale where materials properties depend on size and shape, as well as composition, and differ significantly from the same properties in the bulk. “Nanoscience” seeks to understand these new properties. “Nanotechnology” seeks to develop materials and structures that exhibit novel and significantly improved physical, chemical, and tribiological properties and functions due to their nanoscale size. The goals of nanoscience and nanotechnology are: to understand and predict the properties of materials at the nanoscale to “manufacture” nanoscale components from the bottom up to integrate nanoscale components into macroscopic scale objects and devices for real-world uses P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 45 46 Zhao, S., Ramakrishnan, G., Shen, P., Su, D., Orlov, A. "The first experimental demonstration of the beneficial effects of sub-nanometer platinum particles for photocatalysis", Chemical P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 Engineering Journal, 217, 266–272, 2013. 47 New membranes for filtering out water pollutants Ramakrishnan, G., Dwivedi, G., Sampath, S., Orlov, A. "Development and optimization of novel plasma sprayed ceramic microfiltration membranes", Journal of Membrane Science, 2015, 489, 106. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 48 P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 49 P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 50 P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 51 P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 52 Treated PURETI Clean was sprayed on the concrete flooring of SunLife Stadium in Miami, FL in a 2 step process. The bio-grime accumulated on the right over the course of just 6 weeks while row stayed clean. P.Ravindran, Nanomaterials and Nanotechnology, Springthe 2016:treated Introduction to Nanotechnology -1 Untreated 53 Water Droplets on “Nanoseal” Treated Wood Nanoparticles adhere directly to the substrate molecules (molecular bonding) and assemble into an invisible ultra-thin nanoscopic mesh providing a long lasting, selfcleaning, hydrophobic surface. The wood is protected against decay, fungi and rot. It is dimensionally and UV stable. It will not wear off and cannot be removed by water, normal cleaning agents or high pressure equipment. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 54 Wood Surface Repels Water Droplets Water droplets rest on a wood surface impregnated with BASF’s “Lotus Spray” The surface is superhydrophobic . Thus contact area between the surface of the wood and the water is reduced to a minimum, and the adhesive forces are greatly decreased making the water drops assume a globular form. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 Nanocare revolutionizes fabric technology This Lee Performance Khaki Pant features Nanocare fabric Product Features: * Nanocare fabric repels liquids* Wrinkle free Lee Nanocare khaki pant fabric * Stain resistant Nano-CareTM fabrics sold since Nov. 2001, incorporate “nanowhiskers” into the fabric to make it stain-resistant to waterbased liquids such as coffee and wine. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 55 Nanomaterials in action… Wilson Double CoreTM tennis ball has clay nanoparticles embedded in the polymer lining of its inner wall, which slows the escape of air from the ball making it last twice as long. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 56 Carbon nanotube stabilizers in Tennis rackets increase torque and flex resistance P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 57 58 DoD Focused Areas in Nano * NANOELECTRONICS/NANOPHOTONICS/NANOMAGNETICS Network Centric Warfare Information Dominance Uninhabited Combat Vehicles Automation/Robotics for Reduced Manning Effective training through virtual reality Digital signal processing and LPI communications * NANOMATERIALS “BY DESIGN” High Performance, Affordable Materials Multifunction, Adaptive (Smart) Materials Nanoengineered Functional Materials Reduced Maintenance costs * BIONANOTECHNOLOGY - WARFIGHTER PROTECTION Chemical/Biological Agent detection/destruction Human Performance/Health Monitor/Prophylaxis P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 Why we are interested in “nano-material”? 59 Expecting different behavior of electrons in their transport (for electronic devices) and correlation (for optoelectronic devices) from conventional bulk material. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 Physical properties of nanomaterials 60 Nanomaterials may have a significantly lower melting point or phase transition temperature and appreciably reduced lattice constants, due to a huge fraction of surface atoms in the total amount of atoms Mechanical properties of nanomaterials may reach the theoretical strength, which are one or two orders of magnitude higher than that of single crystals in the bulk form. The enhancement in mechanical strength is due to the reduced probability of defects. Optical properties of nanomaterials can be significantly different from bulk crystals. E.g. The optical absorption peak of a semiconductor nanoparticle shifts to short wavelength, due to an increased band gap. The colour of metallic nanoparticles may change with their sizes due to surface plasmon resonance. Electrical conductivity decreases with a reduced dimension due to increased surface scattering. However, electrical conductivity of nanomaterials could also be enhanced appreciably, due to the better ordering in microstructure, e.g. polymeric fibrils. Magnetic properties of nanostructured materials are distinctively different from that of bulk materials. Ferromagnetism of bulk materials disappears and transfers to superparamagnetism in the nanometer scale due to the huge surface energy. Self-purification is an intrinsic thermodynamic property of nanostructures and nanomaterials. Any heat treatment increases the diffusion of impurities, intrinsic structural defects and dislocations, and one can easily push them to the nearby surface. Increased perfection would have appreciable impact on the chemical and physical properties. For example, chemical stability would be enhanced. Properties of nanostructured materials are size dependant. Properties can be tuned simply by adjusting the size, shape or extent of agglomeration. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 Properties of a material vary with the size of the material (Bulk) Gold is a shiny yellow metal Nanoscopic gold, i.e. clusters of gold atoms measuring 1 nm across, appears red Bulk gold does not exhibit catalytic properties Au nanocrystal is an excellent low temperature catalyst. Therefore, if we can control the processes that make a nanoscopic material, then we can control the material’s properties. Therefore, if we can control the processes that make a nanoscopic material, then we can control the material’s properties. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 61 62 P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 63 Stages from free-space to nano-material Free-space SchrÖdinger equation in free-space: 2 ( ) r ,t i r ,t 2m0 t Solution: k e i ( k r Et / ) 1 2 2 |k | k 2l / L, l 1,2,3,... E 2m0 Electron behavior: plane wave 63 P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 64 Stages from free-space to nano-material Bulk semiconductor SchrÖdinger equation in bulk semiconductor: 2 [ V0 (r )] r ,t i r ,t 2m0 t e2 V0 (r ) V0 (r lR) V0 (r ) r Solution: 2 2 |k | i ( k r Et / ) E nk e nk 2meff Electron behavior: Bloch wave 64 P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 65 Stages from free-space to nano-material Nano-material SchrÖdinger equation in nano-material: 2 [ V0 (r ) Vnano (r )] r ,t i r ,t 2m0 t with artificially generated extra potential contribution: Vnano (r ) Solution: nk e iEt / Fn ,k (r ) nk 65 P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 66 Stages from free-space to nano-material Electron behavior: Quantum well – 1D confined and in parallel plane 2D Bloch wave Quantum wire – in cross-sectional plane 2D confined and 1D Bloch wave Quantum dot – all 3D confined – discrete energy levels 66 P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 67 A summary on electron behavior Free space – plane wave with inherent electron mass – continued parabolic dispersion (E~k) relation – density of states in terms of E: continues square root dependence Bulk semiconductor – plane wave like with effective mass, two different type of electrons identified with opposite sign of their effective mass, i.e., electrons and holes – parabolic band dispersion (E~k) relation – density of states in terms of E: continues square root dependence, with different parameters for electrons/holes in different band P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 68 A summary on electron behavior Quantum well – discrete energy levels in 1D for both electrons and holes – plane wave like with (different) effective masses in 2D parallel plane for electrons and holes – dispersion (E~k) relation: parabolic bands with discrete states inside the stop-band – density of states in terms of E: additive staircase functions, with different parameters for electrons/holes in different band Quantum wire – discrete energy levels in 2D cross-sectional plane for both electrons and holes – plane wave like with (different) effective masses in 1D for electrons and holes – dispersion (E~k) relation: parabolic bands with discrete states inside the stop-band – density of states in terms of E: additive staircase decayed functions, with different parameters for electrons/holes in different band P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 A summary on electron behavior Quantum dot – discrete energy levels for both electrons and holes – dispersion (E~k) relation: atomic-like k-independent discrete energy states only – density of states in terms of E: -functions for electrons/holes P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 69 Nanoscale: High Ratio of Surface Area to Volume P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 70 71 Dimensions of Materials P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 72 Size – Dependent Properties • Nanoscale sizes can lead to different physical and chemical properties - Optical properties - Bandgap - Melting point - Surface reactivity • Even when such nanoparticles are consolidated into macroscale solids, new properties of bulk materials are possible. - Example: enhanced plasticity P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 73 Melting Point The melting point of gold particles decreases dramatically as the particle size gets below 5 nm P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 Source: Nanoscale Materials in Chemistry, Wiley, 2001 74 Modifications due to : Quantum confinement Quantum size effect Energy bands and electronic transition Charge quantization P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 Nanostructures Dimension and Confinement STRUCTURE SPATIAL DIMENSION CONFINEMENT DIMENSION Bulk 3 0 Surface/ Film (Quantum Well) 2 1 Nanotubes, -wires (Quantum wire) 1 2 Nano-particles, clusters (Quantum dots) 0 3 P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 75 Nanomaterials 76 This includes subfields which develop or study materials having unique properties arising from their nanoscale dimensions. Interface and Colloid Science has given rise to many materials which may be useful in nanotechnology, such as carbon nanotubes and other fullerenes, and various nanoparticles and nanorods. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 77 Nanomaterials Development of applications incorporating semiconductor nanoparticles to be used in the next generation of products, such as display technology, lighting, solar cells and biological imaging. Nanoscale materials can also be used for bulk applications; most present commercial applications of nanotechnology are of this flavor. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 Nanomaterials Nanoscale materials are sometimes used in solar cells which combats the cost of traditional Silicon solar cells Progress has been made in using these materials for medical applications. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 78 The first “proof of principle” that atoms could be precisely positioned by man made tool took place in 1989 when scientists at IBM manipulated 35 xenon atoms to form the letters IBM. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 79 CLASSIFICATION OF NANOPARTICLES P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 8 0 81 Nanoparticle A sub-classification of ultrafine particles with lengths in two or three dimensions greater than 1 nanometer (nm) and smaller than about 100 nm, and which may or may not exhibit sizerelated intensive properties. Natural nanoparticles: Particles with one or more dimensions at the nanoscale originating from natural processes, e.g. soil colloids. Engineered nanoparticles: Less frequently also “manufactured nanoparticles”- Nanoparticles manufactured to have specific properties or a specific composition. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 Size-related intensive properties Physical or chemical properties of a particle that change as a particle size falls below a certain threshold (surface charge, conductivity, color, etc.). P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 82 Agglomerate A group of particles held together by relatively weak forces. Ultrafine particles: Term frequently used by those dealing with industrial products, aerosols and air pollution, and referring to particulate matter smaller than 2.5 micrometer. P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 83 Nano is different 84 Gold is noble ...but nano-gold is a superb catalyst. Left: Jewel from Malia, Crete, Greece (ca. 1800 BC); Right: CO oxidation on Au nanoparticle (Remediakis, Lopez, Nørskov, Angew. Chem. (2005)). See also: “Making Gold Less Noble”, Mavrikakis et al., Catal. Lett. (2000). P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 TOOLS IN NANOTECHNOLOGY • Two tools for measurement at nano scale – STM (Scanning Tunneling Microscope) – AFM (Atomic Force Microscope) P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1 85