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Electronic Supplementary Information

Gold Microsheets Having Nano/Microporous Structures

Fabricated by Ultrasonic-Assisted Cyclic Galvanic Replacement

Prompong Pienpinijtham,* Prasert Sornprasit, Kanet Wongravee, Chuchaat Thammacharoen,

and Sanong Ekgasit

Sensor Research Unit, Department of Chemistry, Faculty of Science,

Chulalongkorn University, 254 Phyathai Road, Patumwan, Bangkok 10330, Thailand.

Telephone/Fax: +662 218 7585

*Corresponding author: prompong.p@chula.ac.th

Fig. S1 Solution-exposed side SEM micrograph of Galvanized layer reveals the grain

boundary between particles and the microchannel with the size of 0.5–1 µm

inside particles.

Electronic Supplementary Material (ESI) for RSC Advances.This journal is © The Royal Society of Chemistry 2015

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50 µm

1 µm

5 µm

0.2 µm

Fig. S2 SEM micrographs of Galvanized layer after NH3 treatment.

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B1

B2(Au)

B3(Ag)

B4(Cl)

3μm

3μm

3μm

3μm

A2(Au)

A1

A3(Ag)

A4(Cl)

3μm

3μm

3μm

3μm

Before NH3 treatment After NH3 treatment

Fig. S3 EDS mapping images reveal the distribution of Au, Ag, and Cl in Galvanized

layers (A) before and (B) after NH3 treatments.

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Fig. S4 The proposed formation mechanism of Au/AgCl micro/nanocomposites on a sacrificed Ag

surface. (A) A clean Ag surface. (B) Rapid epitaxial growth of Au film on a clean Ag

surface. (C) Precipitation and formation of AgCl precipitates on a Au film. (D) The

formation of interpenetrated Au/AgCl nanocomposites. (E) The development of AgCl

underlayer.

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0.0 0.1 0.2 0.3 0.4 0.50

50

100

150

200

250

num

ber

pore size (m)

Fig. S5 Pore size distribution of the synthesized nano/microporous Au microsheets.

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0 5 10

keV

Element Atom content(%)

Au

Ag

Cl

19.86

44.96

35.17

Element Atom content(%)

Au

Ag

Cl

96.26

3.74

0

400 Counts

200 Counts

Inte

nsity

(Cou

nts)

A: before NH3 treatment

B: After NH3 treatment

Fig. S6 EDS spectra of Galvanized flakes (A) before and (B) after NH3 treatments.

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Table S1. SEM micrographs (back scattering mode) of Galvanized flakes produced with

additional NaCl before and after NH3 treatments.

Addition of NaCl

NH3 treatment

Before After

0.0 M

0.1 M

0.5 M

1.0 M

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Table S2. SEM micrographs (back scattering mode) of residual Ag plates in NaCl-added

synthesis before and after NH3 treatments.

Addition of NaCl

NH3 treatment

Before After

0.1 M

0.5 M

1.0 M

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1×10-5 M CV on Nano/Mircoporous Gold Microsheets1×10-6 M CV on Nano/Mircoporous Gold Microsheets1 M CV on glass slide

2000 cps

Inte

nsity

(cps

)

Raman shift (cm-1)500 1000 1500 2000 2500

Fig. S7 SERS and normal Raman spectra of crystal violet (CV).

All spectra in Figure S6 were collected by DXR Raman microspectrometer (from

Thermo Scientific) using 50X objective lens with a spot size of ~1 m. Diode laser of 532-

nm excitation wavelength at 1.0 mW was employed to irradiate a sample. The exposure time

was 1 second with 8 exposure numbers. To prepare a sample for SERS measurement, a 5 L

of CV solution with different concentrations was drop-dried on nano/microporous Au

microsheets. Normal Raman spectrum was collected from a drop-dried film of 5 L of 1 M

CV solution.

The enhancement factor of a SERS substrate can be calculated using the following

equation, , where ISERS and IRaman are the integrated intensities of the ))((ads

neat

Raman

SERS

NN

IIEF

strongest bands in the SERS spectrum and that of the corresponding bands in the Raman

spectrum, respectively, and Nneat and Nads are the number of molecules in the cross section of

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the laser beam from the drop-casted sample and the number of adsorbed molecules on the

gold film in the cross section of the laser beam, respectively. However, it is difficult to

measure the roughness of Au microsheets. Then, Nads cannot be determined and EF cannot be

calculated using this equation directly. To obtain approximated EF of our synthesized Au

microsheets, the roughness of Au microsheets is neglected and the term can be ads

neat

NN

considered as the ratio of concentrations between sample solutions for normal Raman and

SERS measurements. The peak at 1181 cm-1 was used as reference peak to calculate EF.

Therefore, EF of our Au microsheets is {(137774.156 counts)/(2250.345 counts)}×{(1

M)/(10-6 M)} = 6.1 × 107.