Chapter 4 Nanomaterials & Bonding NANO 101 Introduction to Nanotechnology 1.

Download Chapter 4 Nanomaterials & Bonding NANO 101 Introduction to Nanotechnology 1.

Post on 04-Jan-2016

215 views

Category:

Documents

1 download

TRANSCRIPT

Slide 1

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

5

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

8

NaCl

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

Thermal Conductors

Ductile materials12Van der Waals forcesdipole-dipoleif between H & N, O, Fhydrogen bond

dipole-induced dipole

induced dipole-induced dipole (London Dispersion forces)

OIntermolecular Forces13HHOHHOHH

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

Octane

Paraffin

15

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

18

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

Recommended

View more >