Chapter 3
Introduction to Nanophysics
1
Chapter 3
Introduction to Nanophysics
The Study of Matter in terms
of Energy and Forces:
•Forces and Interactions
•A Closer Look at Fluidics
•The Wave Nature of Light
•Practical Applications
2
Introduction to Nanophysics
Section 1: Forces and Interactions
Forms of Energy
Electrical Forces
Quantum Physics
The Polar Nature of Water
3
Chapter 3 | Section 1
Forces and Interactions
Chapter 3 | Section 1
Energy is Required or Released when Particles Interact with Forces
Energy Vocabulary
− Mechanical work (w): force applied over a distance
− Heat (q): change in thermal energy reservoir during a physical, chemical, or
biological process (q=ΔH when pressure is constant)
− Entropy (S): measure of the number of ways objects can interact
− Gibbs free energy (ΔG)
• Relationship among enthaply (ΔH), entropy (ΔS), temperature (T)
− ΔG = ΔH – TΔS
− ΔG < 0 spontaneous process (additional energy not required)
− ΔG = 0 equilibrium situation
− ΔG > 0 non-spontaneous process
At the nanoscale, energy can flow between internal energy, in the
form of chemical bonds, and useable energy or heat (ΔH).
4
Forces and Interactions
Four Fundamental Forces Act Upon All Matter
Gravity
Electromagnetic
Weak Nuclear
Strong Nuclear
5
Chapter 3 | Section 1
Forces and Interactions
Relative Influence of Forces Changes with Scale
6
Chapter 3 | Section 1
Forces and Interactions
Forces in a Hydrogen Atom
7
Chapter 3 | Section 1
Forces and Interactions
Electrical Forces
Atoms and Molecules
− Electrostatic interactions
• Chemical bonds
• Hydrogen bonds
− Polarizability
• Van der Waals interactions
Electromagnetic Radiation
− X-rays
− UV rays
Physiological Electrical Signals
− Nervous system (e.g., brain, nerves)
− Muscles (e.g., heartbeat)
8
Chapter 3 | Section 1
Forces and Interactions
Quantum Physics Model of Matter
Matter Is Composed of Atoms and Molecules
− Atoms are composed of elementary particles
− Molecules are composed of atoms
Electrostatic Interactions Predominate
− Within molecules and atoms
− Among molecules and atom
Quanta
− Electrons are confined to regions of space; therefore
their energy is restricted to discrete values
− Transitions between energy levels occurs in discrete
increments
9
Chapter 3 | Section 1
Forces and Interactions
Quantum Physics Model of Matter
Atoms Are Composed of Elementary Particles
− Central nucleus with two particle types:
• Neutrons (no charge)
• Positively charged protons
− Negatively charged electrons found around and
about the nucleus
Electrons Are In Constant Motion
− Individual electrons localized into regions of space
with defined energy
− Electron transitions occur in defined increments
(energy is quantized)
Fluctuating, Non-Uniform Charge Distribution
Surrounds the Atom
10
Chapter 3 | Section 1
Forces and Interactions
Quantum Physics Model of Matter
Molecules Are Composed of Atoms
− Relative location of atomic nuclei give shape to
the molecule
Electrons Are In Constant Motion
− Electrons are shared among atoms in the molecule
in covalent bonds
− Covalent bonds between nuclei have shapes,
locations, energies
• σ-bonds, π-bonds
• molecular orbitals
Fluctuating, Non-Uniform Charge Distribution
Surrounds the Molecule
11
Chapter 3 | Section 1
Forces and Interactions
Quantum Physics Model of Matter
Electrostatic Interactions
− A predominant force among molecules
− Origin: fluctuating, non-uniform charge
distribution surrounding the molecule
12
Chapter 3 | Section 1
Forces and Interactions
Water Molecule
10 Electrons
− 8 from O
− 1 from each H
10 Protons
− 8 from O nucleus
− 1 from each H nucleus
13
Chapter 3 | Section 1
Forces and Interactions
Water Molecule
Electric Dipole
Partial Negative Charge at Oxygen Apex
Partial Positive Charge at Hydrogens
14
Chapter 3 | Section 1
Introduction to Nanophysics
Section 2: A Closer Look at Fluidics
Cohesion and Surface Tension
Hydrophobicity
Adhesive Forces and Capillary Action
Viscosity
Laminar and Turbulent Flow
15
Chapter 3 | Section 2
A Closer Look at Fluidics
Cohesion and Surface Tension
Properties of Liquids
− Liquid molecules move (Brownian motion)
− Liquid phase molecules are attracted to:
• Each other (cohesion)
• Surrounding surfaces (adhesion)
• Surrounding atmosphere
Surface Tension
− Measures the difference between a liquid
molecule’s attraction to other liquid
molecules and to the surrounding fluid
(above)
16
Chapter 3 | Section 2
A Closer Look at Fluidics
Cohesion and Surface Tension
17
Chapter 3 | Section 2
A Closer Look at Fluidics
Chapter 3 | Section 2
Surfaces
Hydrophilic Surface
18
Hydrophobic Surface
A Closer Look at Fluidics
Cohesion and Surface Tension
19
Chapter 3 | Section 2
A Closer Look at Fluidics
Chapter 3 | Section 2
Contact Angle
Hydrophilic Surface
20
Hydrophobic Surface
Super Hydrophobic Surface
A Closer Look at Fluidics
Chapter 3 | Section 2
Super Hydrophobic Surface
Lotus Leaf
21
A Closer Look at Fluidics
Adhesive Forces and Capillary Action
22
Chapter 3 | Section 2
A Closer Look at Fluidics
Fluid Flow in Channels
Laminar Flow
− Molecules moving in one direction,
longitudinally
Turbulent Flow
− Molecules moving in random directions
with net longitudinal flow
23
Chapter 3 | Section 2
A Closer Look at Fluidics
Chapter 3 | Section 2
Viscosity Coefficient η
Viscosity
− Fluid “thickness”
− Quickness or slowness of fluid flow
− Measure of force applied to cross-sectional area of fluid for a period of
time
Volume of Fluid Flowing through a Pipe
Velocity of a Sphere Falling through the Fluid
24
A Closer Look at Fluidics
Laminar and Turbulent Flow
25
Chapter 3 | Section 2
A Closer Look at Fluidics
Forces Acting on Pen Tip in DPN
26
Chapter 3 | Section 2
Introduction to Nanophysics
Section 3: The Wave Nature of Light
Electromagnetic Radiation, Wavelengths, and Energy
Reflection, Refraction, and Wave Interference
Diffraction and Diffraction Gratings
Nanoscale Diffraction with X-rays
27
Chapter 3 | Section 3
The Wave Nature of Light
Electromagnetic Spectrum
28
Chapter 3 | Section 3
The Wave Nature of Light
Young’s Double Slit Experiment
29
Chapter 3 | Section 3
The Wave Nature of Light
Chapter 3 | Section 3
Young’s Double Slit Experiment, Continued
Particle
30
Wave
The Wave Nature of Light
Chapter 3 | Section 3
Young’s Double Slit Experiment, Continued
n λ = d sin θ ≈ d (x / L)
TOP
FRONT
n=2
θ
x
d
n=1
L
31
n=2
The Wave Nature of Light
Chapter 3 | Section 3
Reflective Diffraction
n∙λ = d∙(sin θi + sin θd)
32
The Wave Nature of Light
Chapter 3 | Section 3
X-Ray Diffraction
Bragg law: n∙λ = 2∙d∙sin θ
33
Introduction to Nanophysics
Section 4: Practical Applications
Keeping Things Clean
A Miniature Laboratory
Protein Sensors
Light Under Control
34
Chapter 3 | Section 4
Practical Applications
Chapter 3 | Section 4
Keeping Things Clean
Lotus Leaf
35
Practical Applications
Keeping Things Clean
36
Chapter 3 | Section 4
Practical Applications
A Miniature Laboratory
37
Chapter 3 | Section 4
Practical Applications
Chapter 3 | Section 4
Protein Sensor Concept
Idea
− Create a visible light diffraction grating with known periodicity and ridge
height
− Coat grating surface with an affinity label for a target protein
− Characterize the diffraction wavelength at specific viewing angles
− Expose coated grating to biological sample containing target protein; isolate
protein coated diffraction grating
− Monitor changes in wavelength as a function of protein binding
Technological Challenges
− Ridge material compatibility (substrate, affinity label, target protein solutions)
− Detecting small changes in diffraction wavelength
− Cost effectiveness
38
Practical Applications
Chapter 3 | Section 4
Protein Sensors
Lipid Grating Biosensor
− Illuminate a nanotechnology grating with white light. Detect intensity
changes in the diffracted light upon analyte binding with 5 nm detection
limits
Grating Fabrication with Dip Pen Nanolithography
Enabling DPN Technology
− Multilayer phospholipid ink
• Self-assembling phospholipid (e.g., DOPC)
• Biofunctional phospholipid affinity label for analyte
− Precision patterning on PMMA substrates
• 500 to 700 nm ridge spacing, ≤ 80 nm ridge height
39
Practical Applications
Light Under Control
Photonic Crystals
− 1-D to 3-D nanoscale voids for storage
of photons
Active Research Areas
− Materials for information storage
devices
− Read/write mechanisms
40
Chapter 3 | Section 4