Chapter 4 Nanomaterials & Bonding NANO 101 Introduction to Nanotechnology 1.
Post on 04-Jan-2016
Chapter 4Nanomaterials & BondingNANO 101Introduction to Nanotechnology1Quiz WednesdayMC/Short Answer (10 questions, 30 pts)Free Response (3 questions, 24 pts)Calculations (3 questions, 21 pts)Formula sheet, similar to extra practiceBring a scientific calculator, not a cellphone, graphing calculators are okayYou will have 2 hrs, shouldnt take the entire time.
2MaterialsMatter with a useful purpose
Matter isAnything that has mass and occupies spaceMade up of atoms and/or moleculesTo make molecules and solids need chemical bonds
3Models of the AtomJ.J. Thomson4RutherfordCurrent model ProtonNeutronElectronChargeMass(kg)~1.673*10-27~1.675*10-27~9.11*10-31LocationnucleusnucleuscloudsDiameter of one atom: 0.1 0.5 nm(Carbon atom: 0.15 nm)4Covalent BondingMinimum energy: Attractive and repulsive forces cancel outBinding Energy
Separation between atoms when bonded Interatomic distanceBond length
Energyhttp://voh.chem.ucla.edu/vohtar/winter02/20A/lecture5.htmInteratomic Distance5Covalent CompoundsAtoms share electrons to form molecules 6HH+HHHHH2FF+FFFFF2Lone pair electronsCovalent bonds usually between nonmetal + nonmetalBonding electronsIonic BondingForms saltsTransfer of electronsElectrostatic attractionNo sharing of electrons
Non-Metal:Accepts electronSodiumMetal: Donates electronsFluorineanioncation7
Ionic solidsExamples: NaCl (table salt), (NH)COProperties:High melting pointVery hard Poor conductivity Water soluble
Organic CompoundsC-C bond length ~ 0.15 nmC-H bond length ~ 0.11 nmSimplest organic molecule: methane CH4Octane end H to end H = 1.6 nm
Covalent SolidsExamples: Diamond, Graphene, Silicon carbide, Boron Nitride
Properties:HardHigh melting pointLow conductivity (graphene is exception)10
SiC in bulletproof vests
Diamond = carbon molecular solidIonic/Covalent ScaleElectronegativity How much an atom wants to gain electrons.11
Same electronegativityVery different electronegativityMetallic Bonding Atom cores
Sea of valence electronsElectrical Conductors
Ductile materials12Van der Waals forcesdipole-dipoleif between H & N, O, Fhydrogen bond
induced dipole-induced dipole (London Dispersion forces)
All intermolecular forces are weaker than bonds (ionic, covalent, metallic)13GraphiteIntramolecular vs intermolecularSolid lines = covalent bonds = intramolecular foceDotted lines = Van der Waals forces = intermolecular force14
Strength of London DispersionPropane
Quiz WednesdayMC/Short Answer (10 questions, 30 pts)Free Response (3 questions, 24 pts)Calculations (3 questions, 21 pts)Formula sheet, similar to extra practiceBring a scientific calculator, not a cellphone, graphing calculators are okayYou will have 2 hrs, shouldnt take the entire time.
16Small StructuresParticlesWiresFilms, Layers, CoatingsPorous MaterialsSmall Grained MaterialsMolecules17
ParticlesSmall particles are mostly surfaceBulk solids typically < 1% surface atomsSmall nanoparticles can have ~90% surface atoms
Van der Waals forces dominates Mostly interparticle interactions (fewer bonds)
More reactiveUseful as catalysts
Source: Younan Xia, Washington University
Source: Seoul National UniversityWires / Tubes
19Source: Evans Group, University of LeedsSource: Science Buzz, Science Museum of Minn.ElectronicsOpticsStrength-based applicationsCan characterize by aspect ratio (length/(width or diameter))Films, Layers, Coatings20
Surface is where all interactions and reactions take place.
Self-Assembled Monolayers: Ordered arrangement of molecules that occurs spontaneously
tailbackboneheadhttp://phys.org/news85328131.html#nRlvMolecular Self AssemblyMechanisms for much chemistry
Happens due to:Intermolecular interactionsHydrogen bondinghydrophobicity and hydrophilicitySolvency like dissolves likeSpecific covalent reactionsFunctionalizationEx. Thiols and coinage metalsLooking AheadLab #1 due Thursday 4/23Homework #3 due Monday 4/2722Pre-Lab for ThursdayBottom up Nanoparticle SynthesisStarting with molecular precursorsChemistry! Will build the nanoparticlesComprehensive study on synthesis and properties of colloidal gold published by Faraday (1857)
Classic method (1985, Turkevich)Precursor: dilute chlorauric acid (HAuCl4)Reducing agent: sodium citrate (NaC6H5O7)Reaction temperature: 100 CProduct: stable, uniform, ~20 nm particles
23Gold NP Biosensors24
Make a salt or sugar sensor
25What type of bonds hold the citrate to the gold nanoparticle?What is the difference between sugar dissolved in water and salt dissolved in water?
Observe color visuallyObserve color with spectrometer
http://www.cytodiagnostics.com/store/pc/Gold-Nanoparticle-Properties-d2.htmDalton Trans., 2014,43, 5054-5061