lecture 2 nanomaterils.pdf
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(2) Approaches to Nanoscale Structures. Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(3) Chemical approaches to nanostructures Zero dimensional structures. One dimensional structures. Three dimensional structures. Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(4) Zero Dimensional (0D) Growth. Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(5) Nanoparticle Growth within Dendrimers •. Polymer macromolecules (poly (amido amine)) bind limited numbers of metal ions (Cu, Ag, Au, Pt, Pd) – Driving force for encapsulation includes electrostatics, steric confinement, covalent bonds – Reducing agent causes the metal ions to coalesce – Nanoparticles as small as 1 nm. •. Useful composite material – Metal particles not aggregated – Dendrimer branches control access of other molecules – Terminal groups on dendrimer can be used to control solubility, linking to surfaces. R. Crooks, Acc. Chem. Res. 34, 181 (2001) E.W. Meijer, Chem. Rev. 99, 1665 (1999). Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(6) Reverse Micelles •. Spherical water in oil droplets – surfactant is sodium bis(2-ethylhexyl) sulfosuccinate) Na(AOT) – Size of “water content” depends on relative surfactant concentration. •. Reduction of metal ions or precipitation forms particles – Semiconductor particles (CdS) from 1 - 4 nm – Metals from 1 - 12 nm. M.P. Pileni, J. Phys. Chem. 97, 6961 (1993). M.P. Pileni (France) Langmuir, 13, 3266 (1997) Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(7) Cluster Growth within a Zeolite •. Zeolite-OH + M(CH3)2 – – – –. Intercalation of M ion into zeolite by ion exchange Activation of M+ loaded zeolite Reaction of activated M+ with H2S Zeolite Y high dielectric, aluminosilicate host. Zeolite-OH + M(CH3)2. Zeolite-O-M(CH3) + CH4 H2S. Zeolite-O-M-SH + CH4 Repeat. •. Examples: MS nanoclusters – CdS, ZnS, SnS, Ag2S Calzeferri (U. Bern), J. Phys. Chem. B 103, 6397 (1999). Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(8) Arrested Precipitation: General Approach. C.B. Murray (IBM) Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(9) Arrested Precipitation •. Aqueous reduction of metal salts (Ag, Au) in the presence of citrate ions. Strong reducing agent. – Chemisorption of organic ligands for handling – Distribution varies > 10%. •. II-VI ME nanocrystals (NCs) (M = Zn, Cd, Hg; X = S, Se, Te) – Metal alkyls + organophosphine chalcogenides. ~200-250 C. – Phosphine binding to M controlled by temperature – Ostwald ripening allows for sizeselective aliquots; growth time for 1-2 nm NCs in minutes. Metal salts and stabilizers (metal halides + inert solvent + R3P + long chain acids). Schmid G. 1992. Chem. Rev. 92:1709–27 Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(10) Size-Dependent Properties: Metallic Particles. Ag Nanoprisms Au Spheres Au Spheres ~100 nm ~50 nm ~100 nm 200nm. 200 nm. Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom. Ag Spheres Ag Spheres Ag Spheres ~80 nm ~40 nm ~120 nm.
(11) Size-Dependent Properties: Semiconducting Particles. 10 µm A. Libchaber (NEC) Science 298, 1759 (2002) A.P. Alivisatos (U.C. Berkeley), Science 281, 2013 (1998) Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(12) Chemical approaches to nanostructures Zero dimensional structures. One dimensional structures. Three dimensional structures. Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(13) One Dimensional (1D) Growth. Adapted after Y. Xia et al., Adv. Mat. 15, 353 (2003) Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(14) Electrodeposition within Nanoporous Membranes • •. Alumina, polycarbonate track etched, and silica membranes 5-10 µm thick with pore sizes down to 10 nm. M. Natan (Penn State), Science 294, 137 (2001) Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(15) Templating against Existing 1D Nanostructures GaN from ZnO Nanowires. P. Yang, Nature 422, 599 (2003). TiC nanorods from MWNTs. C.M. Lieber, Chem. Mater., 8, 2041 (1996) Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(16) Templating vs. Other Approaches? •. Nanoscale structures generated by templating methods are typically not crystalline – Number of defects is larger – Critical dimension (confined dimension) is larger; quantum size effects usually not observed – Monodispersity is limited by the structure of template – Free-standing, 1D structures are difficult to obtain. •. What are the requirements for a general, synthetic approach to nanowires? – Anisotropic growth – Equilibrium constraints – Control of catalyst size. Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(17) Laser-assisted Catalytic Growth. (1) Pulsed laser; (2) Focusing lens; (3) Composite target; (4) Furnace; (5) Cold finger; (6) Pump system. C.M. Lieber (Harvard), Science 279, 208 (1998). Examples: InP, GaAs, InAs (Au colloids); GaN (Fe colloids) Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(18) Chemical Vapor Deposition (CVD). 1 µm. Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(19) Solution-based growth •. •. Dissolution of anisotropic crystal structures – Dissolve inorganic metallopolymers in polar solvents such as dimethyl sulfoxide (DMSO) to form hexagonally close packed, linear chains ~2 nm in diameter – Example: Mo6Se6 wires Other methods to obtain anisotropy? – Reduction of an acid or salt in elevated temperatures and exploit Ostwald ripening – Decomposition of precursors in the presence of capping ligands (followed by fractionation for size distribution) – Example: BaTiO3 and SrTiO3 (perovskite) nanostructures. F. diSalvo (Cornell), Science 273, 792 (1996) P. Yang, Adv. Mat. 12, 1526 (2000). H. Park (Harvard), J. Am. Chem. Soc. 124, 1186 (2002) Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(20) Assembly of 0D nanoparticles •. Organization of CdTe nanoparticles into wires – Removal of stabilizer – Assembly over a week in the dark. •. Recrystallization – Ostwald ripening with Cd2+ and Te2- ions – Diffusion of CdTe particles. N.A. Koltov (Okla. State), Science 297, 237 (2002) Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(21) Chemical approaches to nanostructures Zero dimensional structures. One dimensional structures. Three dimensional structures. Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(22) Three dimensional (3D) nanostructures •. Polymer emulsification – Reducing agent is also the solvent – In the presence of a capping reagent and different ratios of seed source, different types of structures – Example: reduction of silver nitrate by ethylene glycol in the presence of poly(vinyl pyrrolidone). •. Replacement reactions – Conversion of one metal to one with a higher reduction potential – Example: Replacement of Ag with Au occurred along the crystal facets in an order commensurate with their free energies: {110} > {100} > {111}. Y. Xia (U. Wash.), Science 298, 2176 (2002); Nano. Lett., 2, 481 (2002) Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom. 3Ag(s) + HAuCl4(aq). Au(s) + 3AgCl(aq) + HCl(aq).
(23) 3D nanostructures: DNA-based assembly •. Au nanostructures assembled by DNA hybridization –. Functionalize large and small Au particles with different DNA strands. –. Introduce a linker strand that contains complementary sequence to those on large and small Au particles. C.A. Mirkin, Inorg. Chem. 39, 2258 (2000) Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(24) 3D nanostructures: NC superlattices •. CdSe colloidal crystals – Introduce non-solvent to cause aggregation and precipitation – Slow destabilization by evaporation from a mixture of solvents can result in ordered superlattices. C.B. Murray, Annu. Rev. Mater. 30, 545 (2000) Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(25) Lab 7: Synthesis of Nanomaterials • Gold colloids • CdSe nanocrystals. Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(26) Synthesis of CdSe Nanoparticles • CdO + oleic acid + octadecene • Heat to 250° C to dissolve the CdO • Selenium + octadecene + tributylphosphine • Heat to 150° C to dissolve the selenium • Transfer Se solution to the Cd solution • Take aliquots. http://www.mrsec.wisc.edu/EDETC/cineplex/CdSe/index.html Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(27) Synthesis of Colloidal Gold – Make HAuCl4 solution in water and pour into a beaker. • Weigh the HAuCl4 using a teflon-wrapped spatula • Heat the solution to boiling on a hot plate.. – Add Na3C6H5O7 to the Au solution in the beaker. – Let the solution boil.. http://www.mrsec.wisc.edu/EDETC/cineplex/gold/index.html Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
(28) Gold Particles as a Chemical Sensor – Take a UV-Vis absorbance spectrum of the Au colloid solution. – Place 3 mL of the Au colloid solution in each of three glass vials. Add 3 mL of water to dilute the colloid solution. – Add 5-10 drops 1M NaCl to the first vial dropwise. Record what happens as the salt solution is added. – Add 5-10 drops 1M sucrose to the second vial dropwise. Junior Research Seminar: Nanoscale Patterning and Systems Teri W. Odom.
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