NANOCUBE SYNTHESIS

AND DIMER

FORMATION

JASON MCHANN

2/05/2015

UNIVERSITY OF UTAH

THE END GOAL

REAL-TIME MOLECULAR

DETECTION

Gold nanocluster and pH indicator

(4-mercapto benzoic acid) Single

plasmonic nanoparticles for

biosensing, Takumi et al.

Functionalizing metallic nano

structures with environmentally

sensitive molecules allows for single

molecule detection.

Example: Disassociation of 4-MBA

carboxyl group causes a shift in

adsorbed spectra. Thus intracellular

detection of pH gradients is possible.

As a specific frequency of light is absorbed into the

resonance of plasmons, the transmitted and reflected

spectrum is altered.

Ref: nanocomposix.com

ENHANCEMENT FACTOR

• Raman scattering a LOW probability

phenomena that is enhanced with

particle geometry.

• Geometry results in hotspots in areas of

small radius

Rycenga et al.

WHAT ARE NANO ANTENNA?

1. WHEN LIGHT INTERACTS WITH THE SURFACE OF A METAL, ITS ENERGY IS TRANSFERRED TO THE

FREE ELECTRONS ON THE SURFACE. THESE FREE ELECTRONS COLLECTIVELY OSCILLATE AS A

PLASMON

2. WHEN THE OSCILLATION IS RESTRICTED TO A DOMAIN COMPARABLE TO THE WAVELENGTH

USED TO EXCITE IT, THEN IT IS A LOCALIZED SURFACE PLASMON(LSP).

3. THE ELECTRIC FIELD OF THE SURFACE IS GREATLY EFFECTED BY PLASMONS AND PROXIMITY TO

OTHER OBJECTS CAN RESULT IN RESONANCE.

4. RESONANCE RESULTS IN ENHANCEMENT OF ELECTRIC FIELDS DUE TO GEOMETRY AND AREAS

OF HEIGHTENED ELECTRIC FIELDS ARE KNOWN AS NANO ANTENNA.

5. RAMAN SCATTERING IS THEORIZED TO BE THE RESULT OF LIGHT INTERACTING WITH

RESONATING PLASMONS TO EMIT RADIATION.

POLYPOL SYNTHESIS OF NANOCUBES

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PVP

AgNC

PVP Monomer

111.139 g/mol

NANO CUBE SYNTHESIS

• Very straight forward reaction

with many sensitive variables.

REAGENTS

Ethylene Glycol: Heat to 150-160 c is necessary for equilibrium shift to favor formation of acetaldehyde. Purity of low metallic ion concentration is important as it is competes with

sulfur ions.

Sodium Hydrosulfide: Initiator that dramatically decreases reaction time 10 fold. Acutuallymolar concentration is difficult to know because it is an unknown hydrate. Suggest moving to

Sodium sulfide. Ratio of sodium sulfide to silver nitrate is 1:10,000.(Panfilova)

PVP: Poly vinyl pyrrolidone. Regardless of molecular weight of polymer, it needs to exist in

reaction in a ratio of 1:1.9-2.25 silver ions per repeating unit of PVP (C6H9NO).

Silver Trifluoroacetate: Source of silver ions for reaction. Use of silver nitrate has been more

widely used, but it is sensitive to heat.

E. V. Panfilova et al, “Study of polypol synthesis reaction parameters controlling high yield of silver nanocubes.”

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2Cl / O

PUBLISHED DATA OF REAGENT VARIATION

E. V. Panfilova et al, “Study of polypol synthesis reaction parameters controlling high yield of silver nanocubes.”

2006

Altering sodium sulfide from 26-32uM

concentration in reaction vessle

Altering Silver:PVP ratio (0.77, 1.155,

1.5, 2.3, .7)

Results of varying NaSH were inconclusive due to incorrect PVP concentration.

1.5mL 2/3/15

1.5mL 1/24/15

1.7mL 2/3/15 1.9mL 2/3/151.25mL 1/24/15

Larger Size Distribution Rare cube formationLarge Shape Distribution 35-45% Yield

Notice over passivation decreases particle size

DIMERIZING

Hydrophobic Sonication

in Ethanol

1. PVP Ag Nanocubes

2. Deposition to substrate

3. Functionalize with

hydrophobic ligand

4. Release from substrate in

ethanol

5. Wash and storage

1) PDMS stamp hydrophobic octadecanethiol (ODT) on to top face of cube for 10

seconds.

2) Allow 5 minutes reaction time.

3) Rinse with toluene(???)

4) Sonicate in hydrophilic 16-mercaptohexandecanoic acid (MHA)

5) Wash in ethanol.

POLY DIMETHYLSILOXANE - PDMS

• Biologically inert. Food additive.

• Resistant to polar solvents, swells with

non polar.

• Two part polymer.

• Elasticity can by tuned by mixing ratio.

• Easy to make and inexpensive

FUNNEL OF LOVE

1. Create a disperse monolayer at the

surface of a filled funnel.

2. Slowly drain fluid from funnel, thereby

reducing surface area.

3. Cubes should form compact monolayer.

The current procedure is

extremely crude as a true

monolayer is not being formed

prior to stamping. Rather 3D

structures are dominating the

surface preventing single face

functionalization.

More commonly we see this…

NEXT…

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THANK YOU

PROFESSOR MICHAEL HOEPFNER

& MICHAEL COTTAM

FUNCTIONALIZATION OF SILVER SURFACE

• Stabilizing PVP must be removed in order

to functionalize surface.

• Thiol-terminated molecules for a stronger

covalent bond with silver than PVP and

will irreversibly replace PVP.

• If a specific percentage of replaced PVP

is required, this can be accomplished by

use of low thiol concentration and

monitoring change in SERS spectrum.