zerog and sticky nano property #1&2: all things stick to each other at the nanoscale. gravity...
TRANSCRIPT
ZeroG and StickyNano 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
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.
Why no Gravity??
An individual water molecule weighs
18 amu or 18 g/mol.
18 g/mol / (6*1023 atoms/mol) = 3 * 10 -23 g
Or 7* 10-26 pounds
0.00000000000000000000000007 lbs.
This weight is billions of times lower than the other forces acting on the water molecule.
H20 Weight = 3*10-22 N
Van der Waals Forces : 10-12 – 10-10 N
Covalent Bonds: ~10-9 N
Gravitational Force Between two carbon atoms ~10-42N
Why no Gravity??
An individual water molecule weighs
18 amu or 18 g/mol.
What is this weight in grams?
In pounds ?
Gr. weak, Stickiness Strong
Forces between atoms and molecules dominate.
Electrostatic and “Steric” in origin.
Electrostatic Forces
Opposite Charges Attract
Like Charges Repel.
Electric Charges: Positive and Negative + _
+ +
+ _
Atoms
Bohr Model
Electrons electrical charge= -e
Protons electrical charge= +e
Neutrons
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
Stickiness = BondingMany types of bonding
Two main categories:
Chemical and Physical
Chemical Bonds are very strong (intra-molecular)
Physical Bonds are much weaker (inter-molecular)
Chemical BondsAtoms interact chemically to form molecules
Atom 1 Atom 2
Molecule
“Molecule”A group of atoms connected by chemical bonds
They share / trade electrons
Chemical BondsWater
Protein
Carbon nanotubes
Gold nanocluster
Chemical BondsDifferent Types of Chemical Bonds
• Covalent Bonds
• Ionic Bonds
• Metallic Bonds
Chemical Bonds 1: Covalent Bonds
Atoms SHARE electrons
strc.herts.ac.uk/bio/markr/ biology/day1.htm
Electronic Orbitals: The wave mechanical model
of atoms
S-Orbital
P-Orbital
D-Orbital F-Orbital
S-Orbital
P-Orbital
D-Orbital F-Orbital
Chemical Bonds 2:Ionic Bonds
Atoms TRADE electrons
Ionic BondsAtoms TRADE electrons
WEAK in WATER
Chemical Bonds 3: Metallic Bonds
Atoms DONATE MOBILE electrons
Atom
electron
Physical or Intermolecular BondsInteractions between molecules
Molecules interact but remain independent. No “sharing” of electrons.
Physical BondsDifferent Types of Physical Bonds
• Van der Waals
• Hydrogen Bonds
• Hydrophobic Interactions
Physical Bonds are Electrostatic in origin
Nano Object
Neutral Charge: equal positive and negative charge
An object of neutral charge can be polarized. +-
Van der Waals forces : Polarizability 1
Polarized Object
Polarized Object
Dipole- Dipole interaction. Attractive. Sticky
Van der Waals forces : Polarizability 2
Polarized Object
Polarizable Object
Dipole-Induced Dipole InteractionAttractive. Sticky.
Van der Waals forces : Polarizability 3
Polarizable Object Polarizable Object
Induced Dipole- Induced Dipole Interaction. Attractive. Sticky.
Van der Waals BondingDifferent Types of Physical Bonds
• dipole - dipole
• dipole - induced dipole
• induced dipole – induced dipole
Hydrogen Bonding
WaterO
H H
_
+ +
Hydrogens have a slight positive charge
Oxygen has a slight negative charge
Hydrogen Bonding
O
H
H
_
+
+ O
H
H
_
++
O
H
_
+
Hydrogen Bond
Hydrogen Bonding: DNA
Base Pairing
Hydrophobic Bonding
Micelles/Detergents/Fatty AcidsHydrophillic
Hydrophobic
water
water
water
water
water
water
Micelles/Detergents/Fatty Acids
water
water
water
water
water
Micelles/Detergents/Fatty Acids
water
water
water
water
water
Micelles/Detergents/Fatty AcidsHydrophillic
Hydrophobic
water
water
water
water
water
water
oil
Micelles/Detergents/Fatty Acids
oil
water
water
water
water
water
Bond EnergiesBond Energies kJ/mol* eV/bond E/kBT
Covalent/Ionic Bonds 200-500 2-5 100-200
Van der Waals Bonds ~1 0.01 0.4
Hydrogen Bonds 10-40 0.1-0.4 5-15
Hydrophobic Bonds ~10 0.1 5
Avidin Biotin ~80-100 1 40
* 1kJ/mol = 0.24 kcal/mol
How strong are these bonds force-wise?It depends but roughly speaking…
Covalent ~ 1000pN Non-Covalent 50-200pN
Pot
enti
al E
nerg
y
xEb
x
0
Bond EnergiesBond Energies kJ/mol* eV/bond E/kBT
Covalent/Ionic Bonds 200-500 2-5 100-200
Van der Waals Bonds ~1 0.01 0.4
Hydrogen Bonds 10-40 0.1-0.4 5-15
Hydrophobic Bonds ~10 0.1 5
Avidin Biotin ~80-100 1 40
* 1kJ/mol = 0.24 kcal/mol
How strong are these bonds force-wise?It depends but roughly speaking…
Covalent ~ 1000pN Non-Covalent 50-200pN
Why no Gravity??
An individual water molecule weighs
18 amu or 18 g/mol.
18 g/mol / (6*1023 atoms/mol) = 3 * 10 -23 g
Or 7* 10-26 pounds
0.00000000000000000000000007 lbs.
This weight is a hundred trillion times smaller than the bond force of an individual hydrogen bond.
H20 Weight = 3*10-25 N
Van der Waals Forces : 10-12 – 10-10 N
Covalent Bonds: ~10-9 N
How does bond energy relate to the rupture force of a bond?
Pot
enti
al E
nerg
y
xEb
x
0
It Depends . . .
Effects of thermal energy on Bond StrengthP
oten
tial
Ene
rgy
xEb
kBT
Thermal Energy affects the Dissociation Constant and Bond Strength.
Thermal Energy aids the dissociation of a bond.
0
Bond Strength: Boltzman FactorWhat is the probability that a bond will spontaneously dissociate????
P=e-Eb/kTkT at room temperature = 0.025 meV
The rate of dissociation
rde-Eb/kBT
Attempt frequencyVibrational frequency of bond orinverse relaxation time
Probability per attempt
Rate of dissociation