Spring 2009 EE 710: Nanoscience and Engineering

Transcription

1 Spring 2009 EE 710: Nanoscience and Engineering Part 13: Gold Colloids and NanoBioTechnology Images and Charts taken from: Hornyak, et.al, Introduction to Nanoscience, CRC press, 2008 Chapter 12 And Various Refereed Sources Instructor: John D. Williams, Ph.D. Assistant Professor of Electrical and Computer Engineering Associate Director of the Nano and Micro Devices Center University of Alabama in Huntsville 406 Optics Building Huntsville, AL Phone: (256) Fax: (256)

2 Gold ldcolloids Introduction to Nanoscience: Chapter 12 2

3 Gold Colloid Formation Turkevitch Route HAuCl 4 + (C 6 H 5 O 7 )Na 3 Au o + oxidized products Approx 5*10 6 mol of HAuCl 4 is dissolved in 19 ml of DI water and heated to boiling 1 ml of 0.5% sodium citrate is added with constant stirring for 30 min Solution undergoes color chagnes from yellow to clear to grey, purple, deep purple and finally ruby red. Water is able to maintain the level of solution to 20 ml Brust route HAuCl 4 + [CH 3 (CH2) 7 ] 4 NBr(TOAB) + Toluene+ BaBH 4 Au o Start with an emulsion of water and toluene 40* mol of tt tetraoctylammonium tl bromide (TOAB) is added d to 80 ml of water 9.0*10 4 mol of HAuCl 4 in 30 ml of water is added to the TOAB solution and stirred vigorously for 10 min Aqueous phase is clear and the organic phase is orange Sodium Borohydride is added dropwise to the mixture and the color changes from orange to white to purple to dark red Solution is then stirred for 24 hrs to insure clusters are monodispersed The organic phase is then washed with sulfuric acid to neutralize the solution TOAB is not considered to be a strong ligand and will readily undergo ligand exchange with stronger ligands like thiols that covalently bind to the gold clusters. 3

4 Gold 55: AuCl[P(C 6 H 5 ) 3 ]+B 2 H 6 Au 55 [P(C 6 H 5 ) 3 ] 12 Cl 6 +H 3 B P(C 6 H 5 ) 3 Gaseous diborane is passed through a warm 150 ml solution of benzene containing 3.94 g of AuCl[P(C 6 H 5 ) 3 ] Diborane is the best reducing agent but it also acts as a Lewis acid that binds phosphines Process limits the amount of free ligand available at any time during the course of the reaction Excess ligand concentration leads to smaller complexes and clusters which are undesirable Temperature is raised to 50oC after 40 min, and the colorless solutions turns brown Upon cooling a dark precipitate settles to the bottom of the now colorless solution The precipitate is filtered and rinsed with dichloromethane and filtered again through a Celite to remove unwanted solids (colloidal gold) The product is reprecipitated slowly in 250 ml of pentane to ensure that the phosphine ligands that saturate the Au 55 cluster Overall yield of the process is 29%. The cluster is 2.1 nm in diameter (Au55 is 1.4 nm) The Au55 product is a dark brown powder that is soluble in dicholoromethane and pyridine and insoluble in petroleum ether, benzene and alcohols. In air the ligand stabilized cluster decomposes to a solid gold amalgam and reverts back to its precursor state Spectroscopy shows that Au55 has 13 central atoms, 24 uncoordinated d peripheral atoms, 12 atoms coordinated d to phosphine ligands and 6 atoms coordinated to chlorine 4

5 Attaching Au55 to DNA Triphynlphosphine ligands of the cluster undergo ligand exchange readily in phase transfer reactions AuCl[P(C 6 H 5 ) 3 ]+B 2 H 6 Au 55 [P(C 6 H 5 ) 3 ] 12 Cl 6 +H 3 B P(C 6 H 5 ) 3 JDW UAH t ill ECE S i

6 Interesting Au 55 Ligand Replacement Directly ties Au 55 nanoparticles to a silicon quantum dot!!! Au 55 [P(C 6 H 5 ) 3 ] 12 Cl 6 +12T 8 OOS SH Au 55 [T 8 OOS SH] 12 Cl 6 +12PPh 3 Product shows increased activation energy and electron tunneling at 0.26eV vs. 0.16eV for Au 55 6

7 Large Scale Surfaces Generated from Boron Ligand Groups Au 55 [P(C 6 H 5 ) 3 ] 12 Cl 6 +Na 2 [B 12 H 11 SH] Au 55 [(B 12 H 11 SH) Na 2 ] 12 Cl 6 Na+ ion makes the system water soluble so clusters can be dissolved and spun onto metallic or glass surfaces at will Self organization is a function of concentration at the surface and film thickness 7

8 Interdigitated Au 55 Systems Note throughout these discussions Sulfur or Phosphorous were used in every experiment to bind to the Au nanoparticle. 8

9 Semiconductor Quantum Dot Formation Inverse Micelle Technology Semiconductor dots are polar and bind well to thiol (sulfur) based chemistries Clusters are formed by chemically creating nanoparticles in nonpolar solutions. HOW?!?!? Use polar side of the ligand to bind polar precursors together into a micelle withthe the nonpolarterminals displayed outward into the nonpolar solvent Reactants then produce a semiconductor nanoparticle + secondary product that can be extracted t using alternate t ligand chemistry Resulting product is stable and can be spun onto a surface and self ordered 9

10 Nanobiotechnology 10

11 Cell Membrane Each structure within the cell is separated by a membrane (a lipid phospholipid bilayer) Protein fused into these structures regulate g the flow of chemical species (thus energy and information) throughout all of biology 11

12 Molecular Motors: Turning the ATP motor Richard L. Cross Nature 427, (29 January 2004) doi: /427407b ATP Motors 12

13 ATP Rotary Motor Device Fabricated on Silicon by Carlos Montemagno at Cornellin

14 Myosin Motors Model for Processive Motion of Mammalian Myosin V ovies/actin_myosin_gif.html anim.gif graz.ac.at/~hadley/nanoscience/week6/mt Gliding_low.gif R. Vale, The Journal of Cell Biology Volume 163, Number 3, 2003, pp

15 14 different families of kinesin motors exist within known mammalian biological systems. Each family contains several variants Kinesin Motors Double strand attached to two heavy terminal activated by ATP When activated, can be used to move larger molecules up and down a filament Can also be used to move filaments. Example: Separation of chromosome microtubules during mitosis Motion of microtubules wrt w.r.t. the cell membrane is how cilia and flagelum are used to move cells 15

16 Dynein Motors a&rls=org.mozilla:en US:official&channel=s&hl=en&q=dynein+motor&um=1&ie=UTF 8&ei=7x_eSc6lH i l &hl & i & UTF i S CrtgfYn4WSAQ&sa=X&oi=video_result_group&resnum=4&ct=title# 16