Notes that will help you understanding concepts in easiest way., Schemes and Mind Maps of Chemistry

Download Notes that will help you understanding concepts in easiest way. and more Schemes and Mind Maps Chemistry in PDF only on Docsity! Dr. Nidhi Jain Bharati Vidyapeeth’s College of Engineering Lavale, Pune INTRODUCTION In simple, any physical substance with structural dimensions between 1- 100nm can be defined as NANOMATERIAL • Nano materials “NANO” +”MATERIALS” “dwarf”=quantum Why is nanoscience attracting so much interest? ● The fundamental properties of matter change at the nanoscale. ● The properties of atoms and molecules are not governed by the same physical laws as larger objects, but by “quantum mechanics”. Image: Fanny Beron, École Polytechnique de Montréal, Canada Mr Miguel Ângel Fernández Vindel, Universidad Autonomade Madrid/Spain What’s interesting aboutnanoscale? ● The physical and chemical properties of nanoparticles can be quite different from those of larger particles of the same substance. ● Altered properties can include but are not limited to colour, solubility, material strength, electrical conductivity, magnetic behavior, mobility (within the environment and within the human body), chemical reactivity and biological activity. Image: C. Menozzi, G.C. Gazzadi, S3 (INFM- CNR), Modena. Artwork:Lucia Covi What is so special aboutnanotechnology? ● it is an incredibly broad, interdisciplinary field. It requires expertise in physics, chemistry, materials science, biology, mechanical and electrical engineering, medicine, and their collective knowledge. ● it is the boundary between atoms and molecules and the macro world, where ultimately the properties are dictated by the fundamental behavior of atoms. ● it is one of the final great challenges for humans, in which the control of materials at the atomic level is possible. What is nanoscalescience? ● The study of objects and phenomena at a very small scale, roughly 1 to 100 nanometers (nm) ● We define nanoscience as the study of phenomena and manipulation of materials at atomic, molecular and macromolecular scales, where properties differ significantly from those at a larger scale; ● and nanotechnologies as the design, characterisation, production and application of structures, devices and systems by controlling shape and size at the nanometer scale. What is nanotechnology? The design, characterization, production,and application of structures, devices, and systems by controlled manipulation of size and shape at the nanometer scale (atomic, molecular, and macromolecular scale) that produces structures, devices,and systems with at least one novel/superior characteristic or property. at Historical milestones There’s Plenty of Room at the Bottom: An Invitation to Enter a New Field of Physics “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 Richard Feynman Wonder why it was not until the year 1960 that anybody began Cal Tech, 1959 seriously to move in this direction. Why cannot we write the entire 24 volumes of the Encyclopedia Brittanica on the head of a pin?” This goal requires patterning at the 10 nanometer scale. Fig shows the eg of a cubic crystal n =atoms along an edge and N= total noof atoms in the cluster N. N=n3 atoms means n=2 N=8. The smallest cube has 8 atoms and each of them is at the surface ,while the next larger cube has 27 atoms with 1 at the center.For larger cube the dispersion scales 1/N1/3 ,which is proportional to1/d. Quantum confinement effect in materials with delocalized electrons Atoms have there well known atomic orbitals.The core of the orbitals are confined to a relatively small volume and remain localised.Each of the N atoms contributes with its atomic state to a band so that although the width of the band increases slightly .whenmore atom is added,thedensityof the statewithintheband is basically proportional to theno ofatom withan ensemblewithextended bandstructure. Thus the density of state is very large for a bulk amount of matter but low for small clusters • However, some intervals of energy contain no orbitals, called band gap. E g Absorption and emission occur at specific wavelengths, which are related to QD size. • Two principal factors cause the properties of nanomaterials todiffer significantly from Bulk materials: • Increased relative surface area • Quantum effects. These factors can change or enhance properties such as reactivity, strength and electrical characteristics. Surface Effects • As a particle decreases in size, a greater proportion of atoms are found at the surface compared to those inside. For example, a particle of • Size-30 nm-> 5% of its atoms on its surface • Size-10 nm->20% of its atoms on itssurface • Size-3 nm-> 50% of its atoms on itssurface • Nanoparticals are more reactive than large particles (Catalyst) Classification Classification is based on the number of dimensions, which are not confined to the nanoscale range (<100 nm). (1) zero-dimensional (0-D), (2) one-dimensional (1-D), (3) two-dimensional (2-D), and (4) three-dimensional (3-D). 0-D All dimensions (x,y,z) at nanoscale ossee 4e= 0 nm s $8.8. Nanoparticles 1-D Two dimensions (x.y) at nanoscale, other dimension (L) is not ti | GY > aoe d<100 IM Lu am Nanowires, nanorods, and nanotubes 2-D One dimension (t) at nanoscale, other two dimensions- (Lx+Ly ) are not Ly Ly ] t<100nm Nanocoatings and nanofilms 25 /  Electrons confinement © For 0-D nanomaterials the electrons are fully confined. © For 3-D nanomaterials the electrons are fully delocalized. © In 1-D and 2-D nanomaterials, electron confinement and delocalization coexist. ® The effect of confinement on the resulting energy states can be calculated by quantum mechanics, as the “particle in the box” problem. An electron is considered to exist inside of an infinitely deep potential well (region of negative energies), from which it cannot escape and is confined by the dimensions of the nanostructure. 26  Quantum effects © The overall behavior of bulk cry stalline materials changes when the dimensions are teduced to the nanoscale. ® For 0-D nanomaterials, where all the dimensions are at the nanoscale, an electron is confined in 3-D space. No electron delocalization (freedom to move) occurs. e For 1-D nanomaterials, electron confinement occurs in 2-D, whereas delocalization takes place along the long axis of the nanowire /rod/tube. ® In the case of 2-D nanomaterials, the conduction electrons will be confined across the thickness but delocalized in the plane of the sheet. 27  Two-dimensional nanomaterials Two of the dimensions are not confined to the nanoscale. 2-D nanomaterials exhibit plate-like shapes. Two-dimensional nanomaterials include nanofilms, nanolayers, and nanocoatings. e 2-D nanomaterials can be: Amorphous or crystalline Made up of various chemical compositions Used as a single layer or as multilayer structures Deposited on a substrate Integrated ina surrounding matrix material Metallic, ceramic, or polymeric 30 7 : Ce a Three-dimensional nanomaterials Bulk nanomaterials are materials that are not confined to the nanoscale in any dimension. These materials are thus characterized by having three arbitrarily dimensions above 100 nm. aterials possess a nanocrystalline structure or involve the Material talline structt lve th presence of features at the nanoscale. In terms of nanocrystalline structure, bulk nanomaterials can be composed ofa multiple arrangement of nanosize crystals, most typically in different orientations. With respect to the presence of features at the nanoscale, 3-D nanomaterials can contain dispersions of nanoparticles, bundles of nanowires, and nanotubes as well as multinanolayers.  Se a a a aD Three-dimensional space showing the relationships among O-D, 1-D, 2-D, and 3-D nanomaterials. 0-D: All dimensions at the nanoscale 1-D: Two dimensions at the nanoscale. one dimension at the macroscale 2-D: One dimension at the nanoscale, two dimensions at the macroscale 3-D: No dimensions at the nanoscale, all dimensions at the macroscale a Carbon e Carbon is a basic element of life ¢ Carbon is special because of its ability to bond to many elements in many different ways e It is the sixth most abundant element in the universe ¢ The most known types of carbon materials: diamond; graphite; fullerenes; and carbon nanotubes 35  Carbon materials 2s and 2p electrons available for bonding pure forms of the same element that differ in structure. os + e foe by sate | 2% 5% dy = 0.357 nm - : e ° - Diamond Graphite Chain sp* (3D) 1332 cm* sp? (2D) 1582 cmt sp' (1D) 1855 cm~ 36  i DIAMOND - chemical bonding is purely covalent - highly symmetrical unit cell - extremely hard - low electrical conductivity - high thermal conductivity (superior) - optically transparent - used as gemstones and industrial grinding, machining and cutting 109.5° = ae 37  Graphene Graphene is an one-atom-thick planar sheet of sp*-bonded carbon atoms that are densely packed ina honeycomb crystal lattice. It can be viewed as an atomic-scale chicken wire made of carbon atoms and the bonds The carbon-carbon bond length in graphene is about 0.142 nm. Graphene is the basic structural element of some carbon allotropes including graphite, carbon nanotubes and fullerenes. 40 mA  o = = O —_ © _>—$$$$ Grnpihime (tytn! top), a pane of carbae atoms tat secembles chicken sfaohece sheets. Véhen graphene < wrapped into co umded forms, !ulle snes wine, ¢ the hatic huileiing nlack of all the “granitic” materials depicted pult They incude hoveycomter cylindels known 4s carbon nanotubes below, Graptite (oocttam sow ar tefr), the man Comporent of pencil “lead,” horton row at center) and socoe ball-shaped motecu'es called buckyhalis 68 cumb’y sobstance that resembles 2 layer cake of weak y bonded Dorm row at ight), 2s well as vartous Shapes that con bine the twe forms. Graphene Graphene physically acts as a 2-Dimensional material(one atom thick . This leads to many properties that are electrially beneficial, such as high electron moblity and lowered power usage. Graphene is currently in its infant stages and is undergoing many applications and studies. • • • • • • • Introduction What is Graphene Methods of preparation Electrical Properties Mechanical Strength Optical Properties Applications Devices • What is Graphene 2-dimensional, crystalline allotrope of carbon • Allotrope: property of chemical elements to exist in two or more forms • Single layer of graphite • Honeycomb (hexagonal) lattice http://upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Graphen.jpg/750px-Graphen.jpg • • • • Graphene vs Other Allotropes Graphene - Top Left Graphite - Top Right Nanotube - Bottom Left Fullerene - Bottom Right http://graphene.nus.edu.sg/content/graphene • • • Electrical Properties Best electrical conductor on earth Graphene electrons are like photons mobility due to lack of effective electron and hole mass Unique arrangement of the carbon atoms allows its electron to easily travel to extremely high velocity without significance chance of scattering • • • • • • Mechanical Strengths Bond length is .142 nm long = very strong bond Strongest material ever discovered ultimate tensile strength of 130 gigapascals compared to 400 megapascals for structural steel Very light at 0.77 milligrams per square metre, paper is 1000 times heavier Single sheet of graphene can cover a whole football field while weighing under 1 gram Also, graphene is very flexible, yet brittle (preventing structural use) • • • Optical Properties Absorbs 2.3% white light Optical electronics absorb <10% white light Highly conductive • Strong and flexible http://en.wikipedia.org/wiki/File:Graphene_visible.jpg Photograph of graphene in transmitted light. * Optical Electronics (touch screen, LTD, OLED) . Composites - Energy storage Devices htto:/www.simplifysimple. com/index .php?news&nid=15 The-new-look-of-phones Summary Graphene, a singular layer of graphite, has been discovered to have unique properties. The high mobility and ability to travel short distances without scattering makes it one of the best materials for electrical applications. Graphene's mechanical and optical properties also allow its use to go beyond electrical applications. Presentation On Carbon Nanotubes 1. WHAT IS A CARBON NANOTUBE ? 2. DISCOVERY OF CARBON NANOTUBES. 3. TYPES OF CARBON NANOTUBES. 4. PROPERTIES OF CARBON NANOTUBES. 5. PROBLEMS RELATED TO CARBON NANOTUBES. 6. SYNTHESIS OF CARBON NANOTUBES. 7. POTENTIALAPPLICATION OF CNT. #A Carbon Nanotube is a tube-shaped material, made of carbon, having a diameter measuring on the nanometre scale. #Carbon Nanotubes are formed from essentially the graphite sheet and the graphite layer appears somewhat like a rolled-up continuous unbroken hexagonalmesh and carbonmolecules at the apexes of the hexagons. #Their name is derived from their long, hollow structure with the walls formed by one atom thick sheets of carbon, called graphene. (a) Armchair, (b,c) zig-zag and (d) chiral tube; (a) metallic, (b) small gap semiconductor, and (c,d) semiconductor. Diameter :- 1 nanometer Band gap :- 0-2ev Their electrical conductivity can show metallic or semiconducting behaviour. A scanning tunnelling microscopy image of SWNT Multi-walled nanotubes (MWNT) consist of multiple rolled layers (concentric tubes) of graphene. Interlayer distance :- 3.4 Å Toxicity:- Under some conditions, nanotubes can cross membrane barriers, which suggests that if raw materials reach the organs they can induce harmful effects such as inflammatory and fibrotic reactions. Crystallographic defect:- As with any material, the existence of a crystallographic defect affects the material properties. Defects can occur in the form of atomic vacancies. There are three methods using which we can produce carbon nanotubes. 1. ARC DISCHARGE METHOD :- 3. CHEMICAL VAPOR DEPOSITION (CVD) :- Wii eer le eT ett) ™ » F Ae N, nee oven . Aine - What are they? • Quantum dots are semiconductor nanocrystals. • They are made of many of the same materials as ordinary semiconductors, Ex.- CdSe, CdS, GaAs,GaP (mainly combinations of transition metals and/or metalloids). • Unlike ordinary bulk semiconductors, which are generally macroscopic objects, quantum dots are extremely small, on the order of a few nanometers (2-10 nm, 10-50 atoms). • They are very nearly zero-dimensional in comparison to bulk semiconductor. OpticalAbsorption  Optical Absorption is a technique that allows one to directly probe the band gap.  The band gap edge of a material should be blue shifted if the material is confined.  Here I present the optical absorption of Ge quantum dots in a SiO2 matrix.  As the dot decreases in size there is a systematic shift of the band gap edge toward shorter wavelengths. 2 5 . a oe vf 8 _— i ot << = x = nme —_ ee” f OS = . ZA =e eo — — wn as A => sourqiosqy Wavelength(nm) Optical Storage • Quantum dots have been an enabling technology for the manufacture of blue lasers. • The high energy in a blue laser allows for as much as 35 times as much data storage than conventional optical storage media. • Less affected by temperature fluctuations, which reduces data errors. • This technology is currently available in new high- definition DVD players, and will also be used in Light Emitting Diodes Light Emitting Diodes.. • Quantum Light Emitting Diodes (QLEDs) are superior to standard LEDs in the same ways the quantum dots are superior to bulk semiconductors. • The tunability of QDs gives them the ability to emit nearly any frequency of light - a traditional LED lacks this ability. • Traditional bulbs may be replaced using QLED technology, since QLEDs can provide a low-heat, full-