29: Nanotechnology. What is Nanotechnology? Properties Control and Understanding. Nanomaterials

Transcription

1 29: Nanotechnology What is Nanotechnology? Properties Control and Understanding Nanomaterials Making nanomaterials Seeing at the nanoscale Quantum Dots Carbon Nanotubes Biology at the Nanoscale Some Applications Are there any concerns? Reading: Ch Ch

2 Announcements Lab 6 Report: Due Wednesday Thursday Lab 7: Silver Nanoprisms Student Activity Day Friday: Literature Discussion Problem Set 12 due Sunday night SuperLab Report Due: Friday, May 16, 5pm Analyses to do: Magnetic susceptibility, CV, chromatography, Mass spec, AAS Report Due: Friday, May 16, 5pm Final Exam: Wed, May 14, 11:00am 1:30pm Course Evaluations: open until Mon, May 19

3 What Nano is NOT Tata Nano car available in India Apple s ipod nano

4 Nano is... why computers are so fast! The number of transistors on a chip doubles about every two years, G. Moore, Intel Founder (1965) 1971:4004 Processor (2300 t s) 2004: Itanium 2 Processor (592 billion t s)

5 Nano is... A Possible Cure for Cancer Detection: Quantum Dots Anti-Tumor Silica-Gold Nanoshells nm N. Halas, J. West (Rice University); Hirsch, et al. PNAS. 100:13549 (2003) Early tumor detection, studied in mice I. Nanoparticles absorb in near-ir, body does not II.NPs coated with targeting-molecules III.NPs Transport into cells IV. Localized heat (ΔT > 30 C) kills cells

6 What is Nanotechnology? A definition (in 3 parts): 1. The control and understanding of material 2. On the scale of about nm 3. Where materials often exhibit unique or enhanced properties

7 Nano IS Small kilometer km 1,000 1X103 meter m 1 1X10 millimeter mm 1/1,000 1X10-3 micrometer μm 1/1,000,000 1X10-6 nanometer nm 1/1,000,000,000 1X10-9 kilometer pm 1/1,000,000,000,000 1X10-12

8 But just HOW small? meter 1 decimeter centimeter micrometer millimeter Nanoscale objects are 1,000 times SMALLER!!!

9 Things on the Nanoscale Viruses 3-50 nm DNA 2.5 nm Nanotube ~1 nm Atoms <1 nm

10 Properties: Between Atoms and Macrosize I. Properties can change depending on the size/surface area: A. Optical (e.g. color, transparency) B. Electrectromagnetic (e.g. conductivity) C. Physical (e.g. hardness, melting point) D. Chemical (e.g. reactivity, reaction rates) II. Particles may act like big atoms and exhibit quantum effects IBM Almaden research laboratory Courtesy D. Carnahan, NanoLabs Inc.

11 Surface Area I. II. Making smaller means surface to volume ratio increases Nanoparticles have HUGE surface area per mass 1 g = surface area of a football field Percent of atoms on surface in an iron particle Source:

12 Intermediate Properties Nano scale: Superparamagnetic No Magnetic Field Applied Field Atomic scale: Paramagnetic Macro scale: Ferromagnetic

13 Optical Properties Example Gold I. Bulk gold appears yellow in color II. Nanosized gold appears red in color A. Plasmon resonance : Size of molecular orbitals restricted by particle size, unlike band structure in bulk gold B. Color from e- transitions between particle-orbitals Bulk gold looks yellow 12 nanometer gold particles look red Sources:

14 Making Nanomaterials Top-Down vs Bottom-Up

15 Bottom-Up Synthesis M + reductant M cap Murray et al. Annu. Rev. Mater. Sci. 30, 545 (2000)

16 Bottom-up: Directed SelfAssembly Block Co-polymers: hydrophilic region Nanotechnology s self-assembly hydrophobic region Lipid Bi-layer: Nature s self-assembly Charged / hydrophilic region Hydrophobic region Paul Nealey, U. of Wisconsin

17 Bottom-up: Template-Directed Synthesis Reverse-micelle creates nano-size reaction vessel Array of nanowells for synthesizing quantum dots

18 Top-Down Polymer layer Metal layer Substrate Templating 4. Acid wash 5. Dissolve polymer 3.

19 Using Light to See The naked eye can see to about 20 microns Light microscopes let us see to about 1 micron Bounce light off of surfaces to create images Light microscope (magnification up to 1000x) Sources: to see red blood cells (400x)

20 Using Electrons to See Scanning electron microscopes (SEM) see down to about 10 nm Bounce electrons off of surfaces to create images Higher resolution due to small size of electrons (4000x) Greater resolution to see things like blood cells in greater detail Sources:

21 Scanning-Tunneling Microscope (STM) I. Tip to Sample distance ~ 10Å. Current varies exponentially to distance. II. Bias voltage used to measure electron density of a particular energy level

22 Scanning-Tunneling Microscope About 25 nanometers

23 Atomic Force Microscope (AFM)

24 Scanning Probe Images AFM imaging of DNA STM imaging of CNTs Lieber J. Phys. Chem. B 2000, 104, A.A. Baker, University of Bristol

25 See and Create Nanolithography creates tiny patterns atom by atom Mona Lisa, 8 microns tall, created by AFM nanolithography Transporting molecules to a surface by dip-pen nanolithography Sources:

26 Nanomaterials: Types 0-D (nanoparticles, quantum dot, nanocrystals) 1-D (nanotubes, nanowires) 2-D (Surfaces) Si NW CNT

27 0-D: Nanoparticles Inorganic crystals roughly nm in diameter in all dimensions Semiconductors: CdSe, ZnS, GaAs, Si, Metals: Au, Ag, Co, Fe, Ni Oxides: ZnO, Fe3O4...

28 Nanomaterials: Quantum Dots Semiconductors: CdSe, ZnS, GaAs... Size controls emission of light Quantum effect CdSe nanocrystals with different diameters (Bawendi Group)

29 1-D: Carbon Nanotubes Roll-up graphene sheet SWNT Diameter and roll-up vector affect properties of nanotubes: Conducting, non-conducting, semi-conducting Magnetic properties Strength Lieber J. Phys. Chem. B 2000, 104, 2794.

30 Bottom-up Controlled Assembly Fe-nanoparticle catalyst controls and encourages growth of nanotubes Amelinckx et al. Science 265, 635 (1994)

31 Carbon Nanotubes Ren ZF. Et.al Science, 1998, 282, 1102.