1. Chapter 4 Nanomaterials & Bonding
Introduction to Nanotechnology

2. Quiz Wednesday MC/Short Answer (10 questions, 30 pts)
Free Response (3 questions, 24 pts)
Calculations (3 questions, 21 pts)
Formula sheet, similar to extra practice
Bring a scientific calculator, not a cellphone, graphing calculators are okay
You will have 2 hrs, shouldn’t take the entire time.

3. Materials Matter with a useful purpose Matter is…
Anything that has mass and occupies space
Made up of atoms and/or molecules
To make molecules and solids – need chemical bonds

4. Models of the Atom J.J. Thomson Rutherford Current model Proton
Neutron
Electron
Charge
Mass
(kg)
~1.673*10-27
~1.675*10-27
~9.11*10-31
Location
nucleus
“clouds”
Diameter of one atom: 0.1 – 0.5 nm
(Carbon atom: 0.15 nm)

5. Covalent Bonding Minimum energy: Separation between atoms when bonded
Attractive and repulsive forces cancel out
Binding Energy
Separation between atoms when bonded
Interatomic distance
Bond length
Energy
Interatomic Distance

6. Covalent Compounds Atoms share electrons to form molecules H + H H H
Bonding electrons F + F F F F2
Lone pair electrons
Covalent bonds usually between nonmetal + nonmetal

7. Ionic Bonding Forms salts Transfer of electrons
Electrostatic attraction
No sharing of electrons
Non-Metal:
Accepts electron
Sodium
Metal:
Donates electrons
Fluorine
anion
cation

8. Ionic solids Examples: NaCl (table salt), (NH₄)₂CO₃ Properties:
High melting point
Very hard
Poor conductivity
Water soluble
NaCl

9. Organic Compounds C-C bond length ~ 0.15 nm C-H bond length ~ 0.11 nm
Simplest organic molecule: methane CH4
Octane end H to end H = 1.6 nm

10. Covalent Solids
Examples: Diamond, Graphene, Silicon carbide, Boron Nitride
Properties:
Hard
High melting point
Low conductivity (graphene is exception)
Diamond = carbon molecular solid
SiC in bulletproof vests

11. Ionic/Covalent Scale
Electronegativity – How much an atom wants to gain electrons.
Same electronegativity
Very different electronegativity

12. Sea of valence electrons
Metallic Bonding
Atom cores
Sea of valence electrons
Electrical Conductors
Thermal Conductors
Ductile materials

13. Intermolecular Forces
Van der Waals forces
dipole-dipole
if between H & N, O, F
hydrogen bond
dipole-induced dipole
induced dipole-induced dipole
(London Dispersion forces) H O H H O O H H H
All intermolecular forces are weaker than bonds (ionic, covalent, metallic)

14. Graphite Intramolecular vs intermolecular
Solid lines = covalent bonds = intramolecular foce
Dotted lines = Van der Waals forces = intermolecular force

15. Strength of London Dispersion
Propane
Octane
Paraffin

16. Quiz Wednesday MC/Short Answer (10 questions, 30 pts)
Free Response (3 questions, 24 pts)
Calculations (3 questions, 21 pts)
Formula sheet, similar to extra practice
Bring a scientific calculator, not a cellphone, graphing calculators are okay
You will have 2 hrs, shouldn’t take the entire time.

17. Small Structures Particles Wires Films, Layers, Coatings
Porous Materials
Small Grained Materials
Molecules

18. Particles Small particles are mostly surface
Bulk solids typically < 1% surface atoms
Small nanoparticles can have ~90% surface atoms
Van der Waals forces dominates
Mostly interparticle interactions (fewer bonds)
More reactive
Useful as catalysts
Source: Younan Xia, Washington University
Source: Seoul National University

19. Wires / Tubes Electronics Optics Strength-based applications
Source: Evans Group, University of Leeds
Source: Science Buzz, Science Museum of Minn.
Electronics
Optics
Strength-based applications
Can characterize by aspect ratio (length/(width or diameter))

20. Films, Layers, Coatings
Surface is where all interactions and reactions take place.
Self-Assembled Monolayers:
Ordered arrangement of molecules that occurs spontaneously
tail
backbone
head

21. Molecular Self Assembly
Mechanisms for much chemistry
Happens due to:
Intermolecular interactions
Hydrogen bonding
hydrophobicity and hydrophilicity
Solvency
“like dissolves like”
Specific covalent reactions
Functionalization
Ex. Thiols and coinage metals

22. Looking Ahead
Lab #1 due Thursday 4/23
Homework #3 due Monday 4/27

23. Pre-Lab for Thursday Bottom – up Nanoparticle Synthesis
Starting with molecular precursors
Chemistry! Will build the nanoparticles
Comprehensive 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 °C
Product: stable, uniform, ~20 nm particles

24. Gold NP Biosensors

25. Make a salt or sugar sensor
What type of bonds hold the citrate to the gold nanoparticle?
What is the difference between sugar dissolved in water and salt dissolved in water?
Dalton Trans., 2014,43,
Observe color visually
Observe color with spectrometer