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Younan Xia Department of Chemistry University of Washintgon Seattle, Washington 98195

Nanostructured Materials. Younan Xia Department of Chemistry University of Washintgon Seattle, Washington 98195 E-mail: xia@chem.washington.edu. What Are Nanostructures?. “These days, you can’t swing a dead cat without hitting something with the word ‘nano’ on it.”.

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Younan Xia Department of Chemistry University of Washintgon Seattle, Washington 98195

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  1. Nanostructured Materials Younan Xia Department of Chemistry University of Washintgon Seattle, Washington 98195 E-mail: xia@chem.washington.edu

  2. What Are Nanostructures? “These days, you can’t swing a dead cat without hitting something with the word ‘nano’ on it.” C&EN News, 2003, April 28, p. 27 Molecular Nano Meso H-atom benzene buckyball soap molecules micelles dendrimers Q-dots hemoglobin viruses carbon nanotubes gold nanoparticles bacteria dusts blood cells hairs colloidal particles

  3. Make It Smaller! First Planar IC First Transistor (1958, Fairchild) (1947, Bell Lab) 180 nm

  4. Moore’s Law: Smaller Is Better! Peercy, Nature 2000, 406, 1023

  5. Types of Nanostructured Materials (1D) (2D) (0D) Joannopoulos et al., Photonic Crystals, 1995

  6. Why Does Size Matter?

  7. Dependence of Surface Area on Size no change in volume r r R r r volume = 4pR3/3 = N 4pr3/3 N = R3/r3 new surface/old surface = N 4pr2/4pR2 = R/r when R=1 mm and r=10 nm, the ratio is 100

  8. Pressure in A Droplet versus Size Pout Pin Young-Laplace Eq. r DP=Pin - Pout = 2g/r for water, g=7x10-2 N/m when r=1 mm, DP=1.4x105 N/m2 or 1.4 atm when r=100 nm, DP=1.4x106 N/m2 or 14 atm when r=10 nm, DP=1.4x107 N/m2 or 140atm

  9. Quantum Confinement: Particle in A Box DE = (n22 - n12)h2/8mL2

  10. Q-Dots: Tuning of Property by Size Alivisatos, MRS Bulletin 1995, August, 23

  11. Q-Dots: Same Substance, Different Colors Alivisatos (UC Berkeley), Bawendi (MIT), Brus (Columbia)

  12. Q-Dots: Superior Fluorescent Markers Superior Brightness Incredible Photostability Multi-Color Capability Single Excitation Source http://www.qdots.com

  13. Quantized Conductance of Electrons metal A L G Ohm’s Law 2e2/h ~ 1/13 kW G = I/v =s(A/L) A van Houten et al., PhysicsToday 1996, July, 22

  14. Metal-Insulator-Metal Junction I Al Al Al2O3 A 0 d V Q = CV C = e0eA/d = 8.85x10-12 Fm-1 8 (10x10 nm2/1nm) = 7.08x10-18 F @100 mV, Q=7.08x10-19 c, or ~4 electrons @25 mV, Q=7.08x10-19 c, or ~1 electron @10 mV, Q=7.08x10-19 c, or ~0.4 electron

  15. Coulomb Blockade and Staircase I -e/2C 0 V e/2C Barner & Ruggerio, Phys. Rev. Lett. 1987, 59, 807

  16. Different Approaches to Nanostructures Top-Down Bottom-Up Ozin, Adv. Mater. 1992, 4, 612

  17. Contact Mode Photolithography photon chrome photoresist quartz substrate substrate

  18. Non-Contact Mode: Projection

  19. Resolving Power (d) of An Optical Lens Limit placed by diffraction d = 0.61 l / NA NA: the numerical aperture of a lens, and NA = n sina; n: the refractive index of the medium above the sample a: the acceptance angle lens a in air, n=1, dmax = 0.61 l for visible light, ~300 nm sample when a=45 degrees, d ~ l

  20. Electron-Beam Lithography Resolution: 1-3 nm l=h/(2meV)1/2 100 kV, l=4 pm FEI Siron XL 30 UW NanoTech Center

  21. Soft Lithography: An Alternative Strategy Whitesides & Love, Sci. Am. 2001, 285(3), 38 Xia & Whitesides, Angew. Chem. 1998, 37, 551

  22. Bottom-Up Approach: Chemical Synthesis UW Bagley Hall, Room 16

  23. Q-Dots Made by Arrested Precipitation Whitesides & Love,Sci. Am. 2001, 283(3), 38 Alivisatos, MRS Bulletin 1995, August, 23 Bawendi et al.,J. Am. Chem. Soc. 1993, 115, 8706

  24. Anisotropic Growth Induced by Structure • Intrinsic Optical Chirality • Highest Photoconductivity • (s = 8x104 S/cm for t-Se) • Piezoelectric & Nonlinear • Optical (NLO) Properties • Thermoelectric Properties • Useful Catalytic Properties • (Halogenation, Oxidation) • Reactivities to Form Other • Functional Materials such • as CdSe, CuSe, and Ag2Se Trigonal Selenium (t-Se) Se Spiral Chain

  25. Synthesis of Uniform Nanowires of t-Se 100 oC 100 oC a-Se R.T. a-Se DG t-Se (t-Se) t-Se a-Se Gates, Yin & Xia, J. Am. Chem. Soc. 2000, 122, 12582

  26. Various Stages of Nanowire Growth Gates, Mayers, Cattle & Xia, Adv. Func. Mater. 2002, 12, 219

  27. Formation of Uniform Silver Nanowires AgNO3 + HO(CH2)2OH PtCl2 XRD (PVP) PVP:Ag=1:1 160-180 oC Sun, Gates, Mayers & Xia, Nano Lett. 2002, 2, 165

  28. One-Dimensional Photonic Crystals Plane-Wave-Expansion-Method (PWEM)

  29. Photonic Band Structures of 1-D Systems Band Gap w=(c/e1/2)k

  30. Opals and Self-Assembly of Colloids Sanders, Nature 1964, 204, 1151

  31. Crystallization of Spherical Colloids Lu, Yin, Gates & Xia, Langmuir 2001, 17, 6344

  32. Photonic Band Structure and Spectra Photonic Band Structure Trans./Refl. Spectra Xia, Gates & Li, Adv. Mater. 2001, 13, 415

  33. Inverse Opal and Photonic Properties Remove Template (n2/n1 = 3.0) Xia, Gates, Yin & Lu, Adv. Mater. 2000, 12, 693

  34. Diffusion Coefficient (D) versus Size Random-Walk Eq. Stokes-Einstein Eq. <d2>1/2 = (2Dt)1/2 D = kBT/6phr • for cells, r is around 10 mm • for bacteria, r is around 1 mm • for viruses, r is around 10 nm (0.01 mm)

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