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Chapter 3 Introduction to Nanophysics. Chapter 3. Introduction to Nanophysics. Forces and Interactions A Closer Look at Fluidics The Wave Nature of Light Practical Applications . Introduction to Nanophysics. 1. 3. Section 1: Forces and Interactions. Forms of Energy Electrical Forces - PowerPoint PPT Presentation
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Chapter 3Introduction to Nanophysics
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Introduction to Nanophysics
Chapter 3
Forces and InteractionsA Closer Look at FluidicsThe Wave Nature of LightPractical Applications
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Chapter
Section 1: Forces and Interactions
Introduction to Nanophysics 13
Forms of EnergyElectrical ForcesQuantum PhysicsThe Polar Nature of Water
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Four Fundamental Forces Act Upon All Matter
Forces and Interactions 13
GravityElectromagneticWeak Nuclear Strong Nuclear
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Relative Influence of Forces Changes with Scale
Forces and Interactions 13
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Forces in a Hydrogen Atom
Forces and Interactions 13
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Electrical Forces
Forces and Interactions 13
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)
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Energy is Required or Released when Particles Interact with Forces
Forces and Interactions 13
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).
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Quantum Physics Model of Matter
Forces and Interactions 13
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
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Quantum Physics Model of Matter
Forces and Interactions 13
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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Quantum Physics Model of Matter
Forces and Interactions 3 1
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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Quantum Physics Model of Matter
Forces and Interactions 13
Electrostatic Interactions − A predominant force among molecules− Origin: fluctuating, non-uniform charge
distribution surrounding the molecule
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Water Molecule10 Electrons− 8 from O − 1 from each H
10 Protons− 8 from O nucleus− 1 from each H nucleus
Forces and Interactions 13
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Water MoleculeElectric DipolePartial Negative Charge at Oxygen ApexPartial Positive Charge at Hydrogens
Forces and Interactions 13
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Section 2: A Closer Look at Fluidics
Introduction to Nanophysics 23
Cohesion and Surface TensionHydrophobicityAdhesive Forces and Capillary ActionViscosityLaminar and Turbulent Flow
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Cohesion and Surface Tension
A Closer Look at Fluidics 23
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
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Cohesion and Surface Tension
A Closer Look at Fluidics 23
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Surfaces
A Closer Look at Fluidics 23
Hydrophilic Surface Hydrophobic Surface
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Cohesion and Surface Tension
A Closer Look at Fluidics 23
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Contact Angle
A Closer Look at Fluidics 23
Hydrophilic Surface Hydrophobic Surface Super Hydrophobic Surface
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Super Hydrophobic Surface
A Closer Look at Fluidics 23
Lotus Leaf
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Adhesive Forces and Capillary Action
A Closer Look at Fluidics 23
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Fluid Flow in Channels
A Closer Look at Fluidics 23
Laminar Flow− Molecules moving in one direction,
longitudinally
Turbulent Flow− Molecules moving in random
directions with net longitudinal flow
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Viscosity Coefficient η
A Closer Look at Fluidics 23
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
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Laminar and Turbulent Flow
A Closer Look at Fluidics 23
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Forces Acting on Pen Tip in DPN
A Closer Look at Fluidics 23
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Section 3: The Wave Nature of Light
Introduction to Nanophysics 33
Electromagnetic Radiation, Wavelengths, and EnergyReflection, Refraction, and Wave InterferenceDiffraction and Diffraction GratingsNanoscale Diffraction with X-rays
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Electromagnetic Spectrum
The Wave Nature of Light 33
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Young’s Double Slit Experiment
The Wave Nature of Light 33
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Young’s Double Slit Experiment, Continued
The Wave Nature of Light 33
Particle Wave
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Young’s Double Slit Experiment, Continued
The Wave Nature of Light 33
n λ = d sin θ ≈ d (x / L)
TOP FRONT
x
n = 2
n = 1
n = 2L
dθ
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Reflective Diffraction
The Wave Nature of Light 33
n∙λ = d∙(sin θi + sin θd)
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X-Ray Diffraction
The Wave Nature of Light 33
Bragg law: n∙λ = 2∙d∙sin θ
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Section 4: Practical Applications
Introduction to Nanophysics 43
Keeping Things CleanA Miniature LaboratoryProtein SensorsLight Under Control
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Keeping Things Clean
Practical Applications 43
Lotus Leaf
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Keeping Things Clean
Practical Applications 43
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A Miniature Laboratory
Practical Applications 43
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Protein Sensor Concept
43Practical Applications
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
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Protein Sensors
Practical Applications 43
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 NanolithographyEnabling 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
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Light Under Control
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Photonic Crystals− 1-D to 3-D nanoscale voids for
storage of photons
Active Research Areas− Materials for information storage
devices− Read/write mechanisms
Practical Applications
