chapters 4 and 5 introduction to nanophysics and nanochemistry:the nanoscopic and macroscopic worlds
TRANSCRIPT
Chapters 4 and 5
Introduction to Nanophysics and Nanochemistry:The nanoscopic and macroscopic worlds
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What does history have to do with science?
Those who cannot learn from history are doomed to repeat it.
George Santayana
The Nanoscopic World: Introduction
2
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What is science?
A search for truth
(and what is truth?)
A methodical form to seek knowledge
A coherent body of knowledge in a certain area
A way to increase the knowledge of humanity
An experience that increases our awareness of the way things are
The Nanoscopic World: Introduction
3
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What is science?
“We find ourselves in a bewildering world. We want to make sense of what we see around us and to ask: What is the nature of the universe? What is our place in it and where did it and we come from? Why is it the way it is?”
From A Brief History of Time
by Stephen Hawkins
The Nanoscopic World: Introduction
4
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How does it work?
from Thomas Kuhn in The Structure of Scientific Revolution
Paradigm: “… accepted examples of scientific practice [that] provide models from which spring particular coherent traditions of scientific research.”
“… normal-scientific research is directed to the articulation of those phenomena and theories that the paradigm already supplies.”
“New and unsuspected phenomena, …are repeatedly uncovered by scientific research… “
“… characteristic shifts in the scientific community’s conception of its legitimate problems and standards… [did not occur] from some methodologically lower to some higher type.“
“…considerations that lead can lead scientist to reject an old paradigm in favor of a new… appeal to the individual’s sense of the appropriate and the aesthetic.”
The Nanoscopic World: Introduction
5
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How we go about it?
Underlying principles
Matter is composed of atoms and molecules.
Atoms differ by their atomic number; molecules differ by the atoms that form them and by their molecular structure.
The behavior of matter depends on the physical and chemical properties of the atoms and molecules that compose it.
The Nanoscopic World: Introduction
6
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How did the Greeks go about it?
:
Greek word meaning indivisible.
Democritus
All that exists is atoms in the void.
Plato
Atoms have different geometries that give a substance its characteristics.
The Nanoscopic World: Introduction
7
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Table of elements
Moderns
The Nanoscopic World: Introduction
Greeks
8
Earth Wind
Fire Water
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Processes
Greeks• Substances are made of
combinations of the four elements
• Substances behave according to the combination of the four elements
• The elements move according to their nature
The Nanoscopic World:
Inrtoduction
Moderns• Substances are made of
elements in the periodic table
• Substances behave according to the elements that compose them
• Energies and forces determine the movement and reactivity of the elements
9
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Agenda
Introduction
The Nanoscopic World−Matter and energy−Atoms−Nanoscale particles
The Macroscopic World−Intermolecular forces−Properties of liquids−Applications
The Nanoscopic World:
Introduction
10
The Nanoscopic World:
Matter and Energy
Introduction to Nanophysics and Nanochemistry
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The Nanoscopic World:
Matter and Energy
12
What is matter?
?
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How do we perceive matter?
States (or phases) of matter: Solid, liquid, gaseous
Classification of matter:
The Nanoscopic World:
Matter and Energy
13
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Explanation of matter
States (or phases) of matter:
The Nanoscopic World:
Matter and Energy
14
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Explanation of matter
Classification of matter
The Nanoscopic World:
Matter and Energy
15
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Definitions
What is energy?
Capacity to perform work.
What is work?
Force applied through a distance.
What is force?
Exerted energy.
Mass times acceleration.
The Nanoscopic World:
Matter and Energy
16
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Mechanical energy
For a moving object
Kinetic Energy
K = ½mv2
Potential Energy (Work)
U (or V) = - W =
Law of conservation of energy
K + U = 0
E = K + U
The Nanoscopic World:
Matter and Energy
17
2
1
x
xF(x)dx
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1st Law of Thermodynamics
Change in energy of a system of particles
E = q + w
w: work
w =
q: heat transferred
Heat
Kavg = (3/2)RT
The Nanoscale World:
Matter and Energy
18
V2
V1p(V)dV
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Electromagnetic spectrum
The Nanoscopic World:
Matter and Energy
19
= c/: wave length: frecuencyc: constant of the speed of light
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Theories of light
Interference
The Nanoscopic World:
Matter and Energy
20
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Properties of light
Diffraction
The Nanoscopic World:
Matter and Energy
21
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Properties of light
Reflection diffraction
The Nanoscopic World:
Matter and Energy
22
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Properties of light
X-ray diffraction
The Nanoscopic World:
Matter and Energy
23
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Theories of light
Light particles
The Nanoscopic World:
Matter and Energy
24
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Theories of light
Light particles
The Nanoscopic World:
Matter and Energy
25
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Theories of light
Photoelectric effect
Energy of a photon
Ef = h
h: constante de Planck
Kinetic energy of the electron
Ke = h -
: Binding energy of electron to the metal
Relativistic effects
Ef = h = mc2
The Nanoscopic World:
Matter and Energy
26
The Nanoscopic World:
Atoms
Introduction to Nanophysics and Nanochemistry
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Atom structure
Bohr atom
The Nanoscopic World:Atoms
28
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Wave particle duality
Interference
The Nanoscopic World:
Atoms
29
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Wave particle duality
De Broglie relation
Wave properties
For light
For an electron
The Nanoscopic World:
Atoms
30
2f mc
hchE
c
mch
mvh
mch
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Modern model of the atom
31
The Nanoscopic World:
Atoms 14
Helium Atom−2 Neutrons and 2 protons in the nucleus
−2 Electrons moving about the nucleus
An Element Is an Atom with a Unique Chemical Identity
The Presence of 2 Protons in the Nucleus Is Unique to the Helium Atom−# Neutrons changes — helium isotopes
−# Electrons changes — helium ions
−# Protons changes — not helium!
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Ions
The Nanoscopic World:
Atoms
32
Net charge = # of protons - # of electrons
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Mathematics of the atom
Schödinger equation
One dimension
Operators
Hamiltonian
Simplified equation
The Nanoscopic World:
Atoms
33
(x)E(x)Vdx
(x)dm8π
h2
2
2
2
ˆ
(x)E(x)V(x)K ˆˆ
VKH ˆˆˆ
EH
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Atomic Spectra
The Nanoscopic World:
Atoms
34
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Interpretation of atomic spectra
The Nanoscopic World:
Atoms
35
Energy levels
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Atomic orbitals
• Electron probability density
The Nanoscopic World:
Atoms
36
Region around a nucleus where the probability of finding an electron is 90%
Orbital:
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Atomic orbitals
37
The Nanoscopic World:
Atoms 14
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Electron configuration
The Nanoscopic World:
Atoms
38
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Periodic Table of the Elements
39
The Nanoscopic World:
Atoms 14
Metals NonmetalsMetalloids
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Periodic Trends: Atomic Number (Number of Protons in Nucleus)
40
The Nanoscopic World:
Atoms 14
Increasing atomic number
Incr
easi
ng a
tom
ic n
um
ber
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Periodic Trends: Atomic Size
41
The Nanoscopic World:
Atoms 14
Increasing atomic size
Incre
asin
g a
tom
ic size
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Periodic trends: Ionization energy
The Nanoscopic World:
Atoms
42
Increasing ionization energy
Incr
easi
ng ioniz
ati
on
en
erg
y
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Periodic Trends: Electronegativity
43
The Nanoscopic World:
Atoms 14
Increasing electronegativity
Incr
easi
ng
ele
ctro
negati
vit
y
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Molecular Geometry
The Nanoscopic World:
Atoms
44
The Nanoscopic World:
Nanoscale particles
Introduction to Nanophysics and Nanochemistry
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Agenda
The Nanoscopic World:
Introduction
46
Introduction
The Nanoscopic World−Matter and energy−Atoms−Nanoscale particles
The Macroscopic World−Intermolecular forces−Properties of liquids−Applications
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Refresher
The Nanoscopic World:
Nanoscale particles
47
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
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Ionic compounds
The Macroscopic World:
Nanoscale particles
48
Na + ½ Cl2 → [ Na+ + Cl– ] → NaCl
Ca + Cl2 → [ Ca+2 + Cl– + Cl– ] → CaCl2
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Covalent bond formation
The Macroscopic World:
Atoms
49
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Molecules
The Macroscopic World:
Nanoscale particles
50
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
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Polymers
The Macroscopic World:
Nanoscale particles
51
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Dendrimers
The Macroscopic World:
Nanoscale particles
52
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SAM
Self-Assembled Monolayers
The Macroscopic World:
Nanoscale particles
53
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Metal nanoparticles
The Macroscopic World:
Nanoscale particles
54
Properties
− 1 to >100 nm
− Uniform size distribution
− Easily modified surface properties
Gold particles
− Are red, not gold
− Inert in biological organisms
− Can be functionalized with SAM
Silver nanoparticles
− have antibacterial effect
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Metal nanoparticles
The Macroscopic World:
Nanoscale particles
55
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Quantum dots
The Macroscopic World:
Nanoscale particles
56
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Energy level revisited
The Macroscopic World:
Nanoscale particles
57
Semiconductors
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Carbon allotropes
The Macroscopic World:
Nanoscale particles
58
Carbon Nanotube
C60
Fullerene
The Macroscopic World:
Intermolecular Forces
Introduction to Nanophysics and Nanochemistry
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Polarity of bonds
The Macroscopic World:
Intermolecular forces
60
Electronegativity−3.5 Oxygen
−2.1 Hydrogen
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Polarity
The Macroscopic World:
Intermolecular forces
61
Dipole
Ions
Induced Dipole
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Intermolecular forces
The Macroscopic World:
Intermolecular forces
62
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The Macroscopic World:
Intermolecular forces
63
Hydrogen bonding
Ice
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Hydrogen bonding in DNA
The Macroscopic World:
Intermolecular forces
64
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Energetics
The Macroscopic World:
Intermolecular forces
65
Energy of interaction− 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): 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).
The Macroscopic World:
Properties of liquids
Introduction to Nanophysics and Nanochemistry
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Liquids
The Macroscopic World:
Properties of liquids
67
Properties of Liquids− Brownian motion
− Cohesion and adhesion forces
− Interaction with surfaces
− Surface tension
− Capillary action
− Fluidity
− Viscosity
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Forces of interaction
The Macroscopic World:
Properties of liquids
68
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Surfaces
The Macroscopic World:
Properties of liquids
69
Hydrophilic Surface Hydrophobic Surface
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Liquid surfaces
Surface Tension− Measures the difference between a liquid molecule’s attraction to other
liquid molecules and to the surrounding fluid (above).
The Macroscopic World:
Properties of liquids
70
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Capillary action
The Macroscopic World:
Properties of liquids
71
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To flow or not to flow
The Macroscopic World:
Properties of liquids
72
Viscosity−Resistance to flow
−Quickness or slowness of fluid flow
Volume of Fluid Flowing through a Pipe
Velocity of a Sphere Falling through the Fluid
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Fluidity
The Macroscopic World:
Properties of liquids
73
Laminar Flow− Molecules moving in one direction,
longitudinally
Turbulent Flow− Molecules moving in random directions
with net longitudinal flow
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Fluidity
The Macroscopic World:
Properties of liquids
74
The Macroscopic World:
Applications
Introduction to Nanophysics and Nanochemistry
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Cleaning up
The Macroscopic World:
Applications
76
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Carbon nanotubes
The Macroscopic World:
Applications
77
Exploring Uses− Enclose atoms and molecules
− Enclose other carbon nanotubes
− Application in batteries for electric vehicles
− Used as a “frictionless” axle and bearing in a nanomotor
− Changeable electric properties
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Solar cells
The Macroscopic World:
Applications
78
Current and Potential Applications− Alternatives to silica
− Improve efficiency in light absorbance
− Thin and flexible films
− Cost reduction
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Miniature laboratory
The Macroscopic World:
Applications
79
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Nanocatalyst
The Macroscopic World:
Applications
80
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Nanocatalyst
The Macroscopic World:
Applications
81
Encapsulated Enzyme Particles−Isolatable
−Enhanced stability• From thermal denaturation• From proteolytic enzymes
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Drug delivery
The Macroscopic World:
Applications
82
β-cyclodextran camptothecin
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Protein sensors
The Macroscopic World:
Applications
83
Process− 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
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Biological sensor
The Macroscopic World:
Applications
84
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Other apps
The Macroscopic World:
Applications
85
Photonic Crystals− 1-D to 3-D nanoscale voids for
storage of photons
Active Research Areas− Materials for information storage
devices
− Read/write mechanisms