Chapter 3
Why Properties Change on the Nanoscale:
An Introduction to Nanoscale Physics
NANO 101
Introduction to Nanotechnology
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The Original Physics
• Classical physics
• Largely developed by Isaac Newton (late 1600s)
• Action = reaction
• Still relevant to our world today
• Doesn’t explain observations of atoms, molecules,
subatomic particles….
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Quantum Mechanics
“I think I can safely say that nobody understands
quantum mechanics”
- Richard Feynman, The Character of Physical Law
(1965)
“For those who are not shocked when they first
come across quantum theory cannot possibly
have understood it.”
- Nils Bohr
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Quantum Mechanics
• Explains phenomena not explained by Classical
Mechanics (early 1900s)
• Based on probability and statistics
• Correspondence Principle – not one or the other
Components:
•
•
•
•
•
Electromagnetic Waves
Photoelectric Effect
Atomic Orbitals
Wave-Particle Duality
Uncertainty Principle
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Electromagnetic Radiation
• Speed of light = 3.0 x 108 m/s = 670 million mph
• Frequency (f): number of cycles/second (s-1 = Hz)
• Wavelength ():
• distance between 2 identical spots on wave
• crest to crest
c 
wavelength
f
c  
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http://www.andor.com/library/
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Light is a Wave
Waves can interfere constructively or
destructively
Double slit experiment shows wave
like nature
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Photoelectric Effect
e-
e-
e-
e- e-
• Light as a wave:
– Energy of emitted electrons should be proportional to intensity
of incident light
– An electron should be emitted eventually if light of a low
frequency is shone at a high intensity for a long period of time
– There should be a lag time associated with lights of lower
frequency
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Photoelectric Effect
e-
e-
e-
e- e-
• Einstein - Light as a particle:
– Energy of light is proportion to its frequency
– Light of a lower frequency will never have enough energy to
eject an electron
– Increasing intensity increases amount of electrons ejected but
not their energy
– No lag time associated with transfer of energy from particle to
electron
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Light is a Particle: Photons
Light “particles”
Discrete (not continuous)
fixed quantity bundles of energy
E photon  hf
h  Planck' s constant
 6.626 10 34 J  s
What is the E of one photon of microwave radiation
with a wavelength of 1.20 cm?
c  f
c  
C = 3 x 108 m/s
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The Double Slit Experiment
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Wavelength of an Electron
h

mv
h = 6.626 x 10-34 J s
m = mass
v = velocity
What is the wavelength of :
Usain Bolt (m = 94 kg) running the 100 meter dash at avg speed of 25 mph
1 mile = 1.61 km
An electron (m = 9.1x10-31 kg) in a TEM accelerated at 3 x 108 m/s
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Heisenberg Uncertainty Principle
Impossible to know exact position and momentum of a particle
at same time
h
x  mu 
4
∆x: uncertainty in position
m: mass
∆u: uncertainty in speed
h: Planck’s constant

Why can we be certain about larger particles (i.e. baseball)?
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Heisenberg Uncertainty Principle
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h
x  mu 
4
• A radar gun measures Felix Hernandez’s fastball
at 94 mph ± 0.1 mph, what is the uncertainty in
position?
– A baseball weights ~ 145 
g
– 1 mile = 1.61 km
• What is the uncertainty in position of one of the
electrons that make up the baseball?
– An electron weight 9.1 x 10-31 kg
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• Reminder: HW#2: 2.1, 3.8, 3.10abd, 3.20, 3.21
• Electrons have particle and wave like properties
• Atoms are the building blocks - > Chemistry and
Nanotechnology
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Models of the Atom
J.J. Thomson
Rutherford
Proton
Neutron
Current model
Electron
Charge
Mass
(kg)
Location
~1.673*10-27 ~1.675*10-27 ~9.11*10-31
nucleus
nucleus
“clouds”
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Schrodinger Equation
• Electrons as standing waves
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Where are electrons?
• Cloud around nucleus
• Each e- is associated with a
specific energy
• Always some uncertainty
Atomic Orbital:
• volume of space where an e- is most likely to be found
• each orbital can hold a maximum of 2 e• orbitals closer to the nucleus have lower energy
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Quantum Numbers
Each atomic orbital can be described by three numbers:
(n, l, ml)
1. Principal quantum number (n)
•
Energy level, shells
•
Probable distance from nucleus
2. Angular momentum quantum number (l)
•
•
Subshells, sublevels
Shape
3. Magnetic quantum number (ml)
•
Orientation
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Orbital Shapes
p orbitals
s orbitals
http://www.800mainstreet.com/33/0003-004b-location-electron.htm
http://library.tedankara.k12.tr/chemistry/vol3/Wave%20
functions%20 and%20probability%20distributions/z51.htm
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More Orbital Shapes
d orbitals
f orbitals
http://int.ch.liv.ac.uk/Lanthanide/Ln_Chemistry_folder/
Miscellaneous%20folder/Miscellaneous.html#f_orbitals
http://www.geo.arizona.edu/xtal/geos306/fall06-1.htm
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Quantization of Energy
Atoms can only contain certain amount of energy
(discrete values – not continuous)
White light is a continuous spectrum
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Quantization of Energy
Atoms can only contain certain amount of energy
(discrete values – not continuous)
E  nhf
Electrons in an atom move
between energy states
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Quantization of Energy
Atoms can only contain certain amount of energy
(discrete values – not continuous)
E  nhf
Electrons in an atom move
between energy states
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Chapter 3 Overview
• Electrons in atoms are found in orbitals.
• Each orbital has an energy level and sublevel (shape)
• The closest energy level to the nucleus is the ground
state; higher levels are excited states
• Electrons can act like particles or waves (double-slit expt)
• Radiation can act like energy or waves (photoelectric
effect; photons are packets of light energy)
• Atoms emit or absorb photons when their electrons
change energy levels
• The Uncertainty Principle states that the more you know
an object’s position, the less you know its momentum
(and visa versa).
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Langmuir Film/Self Assembled
Monolayer
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Langmuir-Blodgett Technique
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Fatty Acids
Lauric acid
Stearic acid
Pentadecanoic acid
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Lycopodium Powder
-Very
hydrophobic
-Help to see the monolayer
-Very fine powder
Primary use of lycopodium powder (not in this lab)
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For Thursday
• No food or drink in lab
• Bring a print out of lab sheet
• Record all significant figures from measurements
• Potential for lab based question on quiz
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