1. ZeroG and Sticky Nano Property #1&2:
All things stick to each other at the nanoscale.
Gravity can be completely ignored Forget Gravity.
Objects tend to stick
Objects don’t fall. No gravity

2. Why no Gravity??
All objects in the universe are subject to gravitational force
The Gravitational force is proportional to mass.
The masses of atoms,molecules and other nano objects are vanishingly small.

3. An individual water molecule weighs
18 amu or 18 g/mol.
18 g/mol / (6*1023 atoms/mol) = 3 * g
Or 7* pounds
lbs.
This weight is billions of times lower than the other forces acting on the water molecule.
Why no Gravity??
H20 Weight = 3*10-22 N
Van der Waals Forces : – N
Covalent Bonds: ~10-9 N
Gravitational Force Between two carbon atoms ~10-42N

4. Why no Gravity?? An individual water molecule weighs
18 amu or 18 g/mol.
What is this weight in grams?
In pounds ?

5. Gr. weak, Stickiness Strong
Forces between atoms and molecules dominate.
Electrostatic and “Steric” in origin.

6. _ + + + _ + Electrostatic Forces Opposite Charges Attract
Electric Charges: Positive and Negative + + _
Opposite Charges Attract
Like Charges Repel. +

7. Atoms Bohr Model Electrons electrical charge= -e
Protons electrical charge= +e
Neutrons
Bohr Model

8. Its Very Sticky down there
How sticky is it?
Our intuition based on our macroscopic world fails us here. In general objects don’t stick in our daily lives.
Its Very Sticky down there

9. Stickiness = Bonding Chemical and Physical Many types of bonding
Two main categories:
Chemical and Physical
Chemical Bonds are very strong (intra-molecular)
Physical Bonds are much weaker (inter-molecular)

10. Chemical Bonds “Molecule” A group of atoms connected by chemical bonds
Atoms interact chemically to form molecules
“Molecule”
A group of atoms connected by chemical bonds
Atom 2
Atom 1
They share / trade electrons
Molecule

11. Chemical Bonds
Water
Carbon nanotubes
Gold nanocluster
Protein

12. Chemical Bonds Covalent Bonds Ionic Bonds Metallic Bonds
Different Types of Chemical Bonds
Covalent Bonds
Ionic Bonds
Metallic Bonds

13. Chemical Bonds 1: Covalent Bonds
Atoms SHARE electrons
strc.herts.ac.uk/bio/markr/ biology/day1.htm

14. Electronic Orbitals: The wave mechanical model of atoms

15. S-Orbital
D-Orbital
F-Orbital
P-Orbital

16. S-Orbital
P-Orbital
D-Orbital
F-Orbital

17. Chemical Bonds 2: Ionic Bonds
Atoms TRADE electrons

18. Ionic Bonds
Atoms TRADE electrons
WEAK in WATER

19. Chemical Bonds 3: Metallic Bonds
Atoms DONATE MOBILE electrons
electron
Atom

20. Physical or Intermolecular Bonds
Interactions between molecules
Molecules interact but remain independent. No “sharing” of electrons.

21. Physical Bonds Van der Waals Hydrogen Bonds Hydrophobic Interactions
Different Types of Physical Bonds
Van der Waals
Hydrogen Bonds
Hydrophobic Interactions

22. Physical Bonds are Electrostatic in origin
Nano Object
Neutral Charge: equal positive and negative charge
An object of neutral charge can be polarized. - +

23. Van der Waals forces : Polarizability 1
Polarized Object
Polarized Object
Dipole- Dipole interaction. Attractive. Sticky

24. Van der Waals forces : Polarizability 2
Polarized Object
Polarizable Object
Dipole-Induced Dipole Interaction
Attractive. Sticky.

25. Van der Waals forces : Polarizability 3
Polarizable Object
Polarizable Object
Induced Dipole- Induced Dipole Interaction. Attractive. Sticky.

26. Van der Waals Bonding dipole - dipole dipole - induced dipole
Different Types of Physical Bonds
dipole - dipole
dipole - induced dipole
induced dipole – induced dipole

27. Hydrogen Bonding + _ Water Hydrogens have a slight positive charge H O
Oxygen has a slight negative charge

28. Hydrogen Bonding O H _ + O H _ + O H _ +
Hydrogen Bond

30. Hydrogen Bonding: DNA
Base Pairing

31. Hydrophobic Bonding

32. Micelles/Detergents/Fatty Acids
Hydrophillic
water
Hydrophobic
water
water
water
water
water

33. Micelles/Detergents/Fatty Acids
water
water
water
water
water

34. Micelles/Detergents/Fatty Acids
water
water
water
water
water

35. Micelles/Detergents/Fatty Acids
Hydrophillic
water
Hydrophobic
water
water
oil
water
water
water

36. Micelles/Detergents/Fatty Acids
water
water
water
oil
water
water

37. Bond Energies How strong are these bonds force-wise?
Bond Energies kJ/mol* eV/bond E/kBT
Covalent/Ionic Bonds
Van der Waals Bonds ~
Hydrogen Bonds
Hydrophobic Bonds ~
Avidin Biotin ~
* 1kJ/mol = 0.24 kcal/mol
How strong are these bonds force-wise?
It depends but roughly speaking…
Covalent ~ 1000pN Non-Covalent pN

38. x
Potential Energy x Eb

39. Bond Energies How strong are these bonds force-wise?
Bond Energies kJ/mol* eV/bond E/kBT
Covalent/Ionic Bonds
Van der Waals Bonds ~
Hydrogen Bonds
Hydrophobic Bonds ~
Avidin Biotin ~
* 1kJ/mol = 0.24 kcal/mol
How strong are these bonds force-wise?
It depends but roughly speaking…
Covalent ~ 1000pN Non-Covalent pN

40. An individual water molecule weighs
18 amu or 18 g/mol.
18 g/mol / (6*1023 atoms/mol) = 3 * g
Or 7* pounds
lbs.
This weight is a hundred trillion times smaller than the bond force of an individual hydrogen bond.
Why no Gravity??
H20 Weight = 3*10-25 N
Van der Waals Forces : – N
Covalent Bonds: ~10-9 N

41. How does bond energy relate to the rupture force of a bond?x
Potential Energy x Eb
It Depends . . .

42. x Eb Effects of thermal energy on Bond Strength
Thermal Energy affects the Dissociation Constant and Bond Strength.
Thermal Energy aids the dissociation of a bond.
Potential Energy x Eb
kBT

43. Bond Strength: Boltzman Factor
What is the probability that a bond will spontaneously dissociate????
kT at room temperature = meV
P=e-Eb/kT
The rate of dissociation
rd = w e-Eb/kBT
Rate of dissociation
Attempt frequency
Vibrational frequency of bond or
inverse relaxation time
Probability per attempt