lecture 6 -- synthesis of nanomaterials

8/15/2019 Lecture 6 -- Synthesis of Nanomaterials

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Synthesis of Nanomaterials

Junior Research Seminar

Spring 2004

4 May 2004

Junior Research Seminar: Nanoscale Patterning and Systems

Teri W. Odom


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Zero Dimensional (0D) Growth


Teri W. Odom


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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 surfacesE.W. Meijer, Chem. Rev. 99, 1665 (1999)

R. Crooks, Acc. Chem. Res. 34, 181 (2001)


Teri W. Odom


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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

• Examples: MS nanoclusters – CdS, ZnS, SnS, Ag2S

Calzeferri (U. Bern), J. Phys. Chem. B 103, 6397 (1999)

Zeolite-OH + M(CH3)2 Zeolite-O-M(CH3) + CH4

Zeolite-O-M-SH + CH4

Repeat

H2S


Teri W. Odom


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Arrested Precipitation: General Approach

C.B. Murray (IBM)


Teri W. Odom


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Arrested Precipitation

Strong reducing agent

Metal salts and stabilizers

(metal halides + inert solvent

+ R3P + long chain acids)

~200-250 C

• Aqueous reduction of metal

salts (Ag, Au) in the presence of

citrate ions

– Chemisorption of organic ligandsfor handling

– Distribution varies > 10%

• II-VI ME nanocrystals (NCs) (M =

Zn, Cd, Hg; X = S, Se, Te)

– Metal alkyls + organophosphine

chalcogenides

– Phosphine binding to M

controlled by temperature

– Ostwald ripening allows for size-

selective aliquots; growth time for

1-2 nm NCs in minutes

Schmid G. 1992. Chem. Rev. 92:1709–27


Teri W. Odom


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Size-Dependent Properties:

Metall ic Particles

200 nm

Au Spheres

~100 nm

Ag Nanoprisms

~100 nm

Ag Spheres

~80 nm

Ag Spheres

~40 nm

Au Spheres

~50 nm

Ag Spheres

~120 nm

200nm


Teri W. Odom


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A. L ibchaber (NEC) Science 298, 1759 (2002)

A.P. Alivisatos (U.C. Berkeley), Science 281, 2013 (1998)

10 µm

Size-Dependent Properties:

Semiconducting Particles


Teri W. Odom


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One Dimensional (1D) Growth

Adapted after Y. Xia et al ., Adv. Mat . 15, 353 (2003)


Teri W. Odom


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Electrodeposition within Nanoporous Membranes

• Alumina, polycarbonate tracketched, and si lica membranes

• 5-10 m thick with pore sizesdown to 10 nm

M. Natan (Penn State), Science 294, 137 (2001)


Teri W. Odom

http://www.sciencemag.org/content/vol294/issue5540/images/large/se3819799003.jpeghttp://www.sciencemag.org/content/vol294/issue5540/images/large/se3819799003.jpeghttp://www.sciencemag.org/content/vol294/issue5540/images/large/se3819799003.jpeghttp://www.sciencemag.org/content/vol294/issue5540/images/large/se3819799003.jpeg


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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)


Teri W. Odom


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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


Teri W. Odom


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Laser-assisted Catalytic Growth

(1) Pulsed laser; (2) Focusing lens; (3) Composite target; (4) Furnace; (5) Cold f inger; (6) Pump system

C.M. Lieber (Harvard), Science 279, 208 (1998)

Examples: InP, GaAs, InAs (Au colloids); GaN (Fe colloids)


Teri W. Odom


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Chemical Vapor Deposition (CVD)

1 m


Teri W. Odom


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Solution-based growth

• Dissolution of anisotropic crystalstructures

– Dissolve inorganicmetallopolymers in polarsolvents such as dimethyl

sulfoxide (DMSO) to formhexagonally close packed,linear chains ~2 nm in diameter

– Example: Mo6Se6 wires

• Other methods to obtain

anisotropy?

– Reduction of an acid or salt inelevated temperatures andexploit Ostwald ripening

– Decomposition of precursors in

the presence of capping ligands(followed by fractionation forsize distribution)

– Example: BaTiO3 and SrTiO3(perovskite) nanostructures

H. Park (Harvard), J. Am. Chem. Soc. 124, 1186 (2002)

F. diSalvo (Cornell), Science 273, 792 (1996)

P. Yang, Adv. Mat. 12, 1526 (2000)


Teri W. Odom


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Assembly of 0D nanoparticles

• Organization of CdTenanoparticles into wires

– Removal of stabilizer

– Assembly over a week in the dark

• Recrystallization

– Ostwald ripening with Cd2+ andTe2- ions

– Diffusion of CdTe particles

N.A. Koltov (Okla. State), Science 297, 237 (2002)


Teri W. Odom


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Zero dimensional structures

Three dimensional structures

One dimensional structures

Chemical approaches to nanostructures


Teri W. Odom


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Three dimensional (3D) nanostructures

• Polymer emulsif ication

– 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 Auoccurred along the crystal facets in

an order commensurate with their free

energies: {110} > {100} > {111}

3Ag(s) + HAuCl4(aq)

Au(s) + 3AgCl(aq) + HCl(aq)

Y. Xia (U. Wash.), Science 298, 2176 (2002); Nano. Lett., 2, 481 (2002)


Teri W. Odom


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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)


Teri W. Odom


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3D nanostructures: NC superlattices

• CdSe colloidal crystals

– Introduce non-solvent to cause

aggregation and precipitation

– Slow destabilization by

evaporation from a mixture ofsolvents can result in ordered

superlattices

C.B. Murray, Annu. Rev. Mater. 30, 545 (2000)


Teri W. Odom


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Lab 7: Synthesis of Nanomaterials

• Gold colloids

• CdSe nanocrystals


Teri W. Odom


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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


Teri W. Odom

http://www.mrsec.wisc.edu/EDETC/cineplex/gold/index.htmlhttp://www.mrsec.wisc.edu/EDETC/cineplex/gold/gold3.htmlhttp://www.mrsec.wisc.edu/EDETC/cineplex/gold/index.htmlhttp://www.mrsec.wisc.edu/EDETC/cineplex/gold/index.html


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Gold Particles as a Chemical Sensor

– Take a UV-Vis absorbance

spectrum of the Au colloid

solution.

– Place 3 mL of the Aucolloid 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 asthe salt solution is added.

– Add 5-10 drops 1M

sucrose to the second vial

dropwise.


Teri W. Odom

lecture 6 -- synthesis of nanomaterials

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