Synthesizing Gold Nanoparticle DimersRyan Miller, Yan Zhou, Peng Zhang

Department of ChemistryUniversity of Cincinnati, Cincinnati, Ohio 45220

BACKGROUND

The research involving gold dimers has been increasing significantly in recent

years. A dimer is formed when two metal particles are close together and have

a combined surface plasma resonance. This will greatly enhance the

molecule’s electric field. This enables a great increase in Raman and

photoluminescence signals. The goal of this experiment is to synthesize gold

dimers using a new method. Testing the results required the use of Surface-

Enhanced Raman Spectroscopy (SERS) to produce a qualitative result.

OBJECTIVES

Find the right procedure for synthesizing gold dimers

Use SERS in order to test if the procedure produced the desired dimers

Take pictures of the gold dimers

RESULTS (continued)

Acetone and TTCA Controls

CONCLUSION

The PMMA method was successful in producing the desired gold

dimers. The method involved self-assembly of the gold particles on a

PMMA template. The gold dimers produced allowed for a greatly

enhanced SERS signal. With high plasmonic enhanced optic properties,

the gold dimers may be useful in studies involving solution based SERS

and plasmonic applications.

REFERENCES

Zhong, Lu B., Jun Yin, Yu-Ming Zheng, Qing Lu, and Gang-Hong Luo. "Self-Assembly of Au Nanoparticles on PMMA

Template as Flexible,." Analytical Chemistry 86 (2014): 6262.

THANKS

Support from the Chemistry Department, University of

Cincinnati is appreciated.

ILLUSTRATIONS

TTCA

RESULTS Raman Microscope Raman Spectrum

TTCA Conjugated Gold Nanoparticles on PMMA Template

TTCA Conjugated Gold Dimers on PMMA Template

TTCA Conjugated Gold Dimers

PROCEDURE & MATERIALS 7.5 mL of freshly prepared Au NPs suspension is transferred to a glass vial, followed by

addition of 4.5 mL of toluene with 4mg of PMMA

4 mL of ethanol is injected into the Au NPs suspension using a mechanical syringe pump with a feeding rate of 10 mL/h.

The glass vial is placed in the hood for 24h. A thin PMMA template will be formed on the top of the aqueous solution after the evaporation of toluene. The self-assembled Au NPs layer will be fixed on the newborn PMMA template.

A pair of tweezers is used to retrieve the prepared Au NPs/PMMA film onto a glass slide.

Rinse the PMMA film with water to remove any free Au NPs.

The link molecule (also used as Raman probe) is added by rinsing the PMMA film with a Trithiocyanuric acid solution(TTCA, 1uM in ethanol). Rinse the PMMA film to remove unbinding TTCA molecules.

The Au NP dimers will be formed by adding another portion of Au NPs suspension onto the prepared TTCA-conjugated Au NPs/PMMA film. Rinse the film with water to remove any free Au NPs.

Dissolve the prepared Au dimers/PMMA film in acetone. The final product is collected by centrifuging the solution at 6000rpm.

The product is measured using a Raman microscope (pictured below) at wavelengths of

633 nm and 785 nm.

Using the instruments microscope and Transmission Electron Microscopy (TEM), the results are photographed.

Poly(methyl methacrylate) (PMMA)Trithiocyanuric Acid (TTCA)

Preparation of Gold Nanoparticles in PMMA

Ethanol

Gold NPs

Toluene & PMMA

PMMA & Au Film

Conjugation of Gold Dimers on PMMA Template

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Inte

nsity

Raman shift(cm-1)

PMMA@Au@TTCA

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B

Raman shift(cm-1)

Acetone

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B

Raman shift(cm-1)

TTCA

979

TEM Image of Gold Dimers and Single Atoms

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nsity

Raman shift(cm-1)

Spot 1 Spot 2

975 1355

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nsity

Raman shift(cm-1)

spot 1 spot 2

975 1355

PMMA

Au