Chapter 3 Introduction to Nanophysics

1. Chapter 3 • Introduction to Nanophysics

2. Chapter 3 Introduction to Nanophysics • Forces and Interactions • A Closer Look at Fluidics • The Wave Nature of Light • Practical Applications

3. Introduction to Nanophysics • 1 • 3 Section 1: Forces and Interactions • Forms of Energy • Electrical Forces • Quantum Physics • The Polar Nature of Water

4. Forces and Interactions • 1 • 3 Four Fundamental Forces Act Upon All Matter • Gravity • Electromagnetic • Weak Nuclear • Strong Nuclear

5. Forces and Interactions • 1 • 3 Relative Influence of Forces Changes with Scale

6. Forces and Interactions • 1 • 3 Forces in a Hydrogen Atom

7. Forces and Interactions • 1 • 3 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. Forces and Interactions • 1 • 3 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).

9. Forces and Interactions • 1 • 3 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

10. Forces and Interactions • 1 • 3 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

11. Forces and Interactions • 3 • 1 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

12. Forces and Interactions • 1 • 3 Quantum Physics Model of Matter • Electrostatic Interactions • A predominant force among molecules • Origin: fluctuating, non-uniform charge distribution surrounding the molecule

13. Forces and Interactions • 1 • 3 Water Molecule • 10 Electrons • 8 from O • 1 from each H • 10 Protons • 8 from O nucleus • 1 from each H nucleus

14. Forces and Interactions • 1 • 3 Water Molecule • Electric Dipole • Partial Negative Charge at Oxygen Apex • Partial Positive Charge at Hydrogens

15. Introduction to Nanophysics • 2 • 3 Section 2: A Closer Look at Fluidics • Cohesion and Surface Tension • Hydrophobicity • Adhesive Forces and Capillary Action • Viscosity • Laminar and Turbulent Flow

16. A Closer Look at Fluidics • 2 • 3 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

17. A Closer Look at Fluidics • 2 • 3 Cohesion and Surface Tension

18. A Closer Look at Fluidics • 2 • 3 Surfaces Hydrophilic Surface Hydrophobic Surface

19. A Closer Look at Fluidics • 2 • 3 Cohesion and Surface Tension

20. A Closer Look at Fluidics • 2 • 3 Contact Angle Hydrophilic Surface Hydrophobic Surface Super Hydrophobic Surface

21. A Closer Look at Fluidics • 2 • 3 Super Hydrophobic Surface Lotus Leaf

22. A Closer Look at Fluidics • 2 • 3 Adhesive Forces and Capillary Action

23. A Closer Look at Fluidics • 2 • 3 Fluid Flow in Channels • Laminar Flow • Molecules moving in one direction, longitudinally • Turbulent Flow • Molecules moving in random directions with net longitudinal flow

24. A Closer Look at Fluidics • 2 • 3 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

25. A Closer Look at Fluidics • 2 • 3 Laminar and Turbulent Flow

26. A Closer Look at Fluidics • 2 • 3 Forces Acting on Pen Tip in DPN

27. Introduction to Nanophysics • 3 • 3 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

28. The Wave Nature of Light • 3 • 3 Electromagnetic Spectrum

29. The Wave Nature of Light • 3 • 3 Young’s Double Slit Experiment

30. The Wave Nature of Light • 3 • 3 Young’s Double Slit Experiment, Continued Wave Particle

31. The Wave Nature of Light • 3 • 3 Young’s Double Slit Experiment, Continued nλ = d sin θ ≈ d (x / L) TOP FRONT n = 2 x θ d n = 1 n = 2 L

32. The Wave Nature of Light • 3 • 3 Reflective Diffraction n∙λ = d∙(sinθi+ sinθd)

33. The Wave Nature of Light • 3 • 3 X-Ray Diffraction Bragg law: n∙λ = 2∙d∙sinθ

34. Introduction to Nanophysics • 4 • 3 Section 4: Practical Applications • Keeping Things Clean • A Miniature Laboratory • Protein Sensors • Light Under Control

35. Practical Applications • 4 • 3 Keeping Things Clean Lotus Leaf

36. Practical Applications • 4 • 3 Keeping Things Clean

37. Practical Applications • 4 • 3 A Miniature Laboratory

38. 4 • 3 • Practical Applications 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

39. Practical Applications • 4 • 3 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

40. 4 • 3 • 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