Highly Reproducible and Sensitive Surface-Enhanced Raman Scattering from

Colloidal Plasmonic Nanoparticle via Stabilization of Hot Spots in Graphene Oxide

Liquid Crystal

Arindam Saha, Sharbari Palmal and Nikhil R. Jana,*

Centre for Advanced Materials, Indian Association for the Cultivation of Science,

Kolkata-700032, India

*Corresponding author. E-mail: camnrj@iacs.res.in. Telephone: +91-33-24734971. Fax:

+91-33-24732805.

Figure S1. Optical property and TEM images of different plasmonic nanoparticles.

Electronic Supplementary Material (ESI) for NanoscaleThis journal is © The Royal Society of Chemistry 2012

Figure S2: Colloidal Ag@Au based SERS of malachite green and methylene blue using

graphene oxide (GO) induced controlled aggregation and salt induced uncontrolled

aggregation; showing that signal remains stable with time for GO but for salt (NaCl) it

decreases with time. Colloidal Ag@Au, Raman probe and GO/salt are mixed together

and SERS signal is collected after 5 mins (blue), 5 hrs (pink) and 2 days (black).

0

500

1000

500 1000 1500

0

500

1000

1500

2000

2500

500 1000 1500

0.1 nM malachite green 0.1 nM malachite greenGO salt

0

500

1000

1500

2000

500 1000 1500

0

500

1000

1500

2000

2500

3000

500 1000 1500

1 nM methylene blue 1 nM methylene blueGO salt

Raman shift (cm-1)

Inte

nsi

ty

Raman shift (cm-1)

Raman shift (cm-1)Raman shift (cm-1)

Inte

nsi

ty

Inte

nsi

tyIn

ten

sity

Electronic Supplementary Material (ESI) for NanoscaleThis journal is © The Royal Society of Chemistry 2012

Figure S3. Different colloidal particle based SERS via GO induced controlled

aggregation showing stable SERS signal for various colloidal particles.

Electronic Supplementary Material (ESI) for NanoscaleThis journal is © The Royal Society of Chemistry 2012

Figure S4: Raman probe concentration dependent SERS signal for 4-mercaptopyridine

(A) and rhodamine 6G (B) in GO-Ag@Au based method, showing that 4-

mercaptopyridine can be detected upto picomolar concentration and rhodamine 6G can

be detected upto nanomolar concentration.

Figure S5. Dependence of SERS signal of rhodamine 6G (1 nM) due to change of

mixing sequence showing that signal is independent of mixing sequence for GO but

varies for salt. The red curve is obtained when colloidal Ag@Au is first mixed with

GO/salt and then Raman probe is added, while in black curve colloidal Ag@Au is mixed

with Raman probe and then GO/salt is added. In all cases SERS signals are collected after

5 mins of mixing all reagents.

Electronic Supplementary Material (ESI) for NanoscaleThis journal is © The Royal Society of Chemistry 2012

Figure S6. SERS of anionic fluorescein (1 nM) using GO-diamine or salt-diamine,

showing that signal remains stable with time for GO-diamine but decreases with time

when salt-diamine is used. Here diamine induces aggregation of anionic particles.

Colloidal Ag@Au, diamine and GO/salt are mixed together and SERS signal was

collected after 5 mins (blue), 5 hrs (pink) and 3 days (black).

Figure S7. Dependence of SERS signal of 1 µM rhodamine 6G on the amount of GO

(left panel) and Ag particle (right panel), showing that enhancement depends on the

optimum amount of GO and Ag particle. Colloidal Agcit, GO and rhodamine 6G are

mixed together and SERS signal was collected after 5 mins.

0

500

1000

1500

2000

2500

500 1000 1500

0

200

400

600

500 1000 1500

Raman Shift (cm-1)

Inte

nsi

ty

salt-diamine GO-diamine

Inte

nsi

ty

Raman Shift (cm-1)

Electronic Supplementary Material (ESI) for NanoscaleThis journal is © The Royal Society of Chemistry 2012

Figure S8: Raman probe dependent plasmon coupling: UV-Visible spectra of

Ag@Au in presence of GO and different concentrations of 4-mercaptopyridine (MPy)

(A) and rhodamine 6G (Rh6G) (B). With increasing probe concentrations plasmon peak

at ~ 410 nm decreases and coupled plasmon at ~ 700-730 nm increases, which indicates

probe dependent aggregation of Ag@Au particles. C) Fluorescence spectra of rhodamine

6G quenches in presence of Ag@Au and GO.

Figure S9: TEM images of aggregates formed for Ag@Au-rod, Agcit and Ag-plate

nanoparticles as plasmonic particles in presence of 10-7

M rhodamine 6G as Raman probe

and GO. Dimer to tetramer aggregates has been observed on GO surface. Red arrows

showing the graphene oxide and red circles indicate the particle aggregates.

Electronic Supplementary Material (ESI) for NanoscaleThis journal is © The Royal Society of Chemistry 2012

Figure S10: Representative TEM images aggregated Ag@Au obtained in presence of

GO and varying concentration of 4-mercaptopyridine. Some of these TEM images have

been used to prepare distribution of particle aggregation shown in Figure 5. A) 0.0 M 4-

mercaptopyridine -- showing mainly isolated Ag@Au, B) 10-9

M 4-mercaptopyridine ---

showing mainly dimmer, trimer and tetramer, (C) 10-7

M 4-mercaptopyridine – showing

aggregates of 5-10 particles and (D) 10-5

M 4-mercaptopyridine --- showing large

aggregates of >10 particles.

Electronic Supplementary Material (ESI) for NanoscaleThis journal is © The Royal Society of Chemistry 2012

Figure S11. XRD spectra of graphene oxide under SERS condition using 10-10

M 4-

mercaptopyridine and Ag@Au nanoparticles. The sharp peak at 90

indicates ordered GO

with interlayer spacing of ~ 25 A0.

Figure S12. SERS spectra of 10-4

M rhodamine 6G and 10-5

M 4-mercaptopyridine

obtained by depositing Raman probe and plasmonic particle (Ag@Au) on GO film.

SERS signals found stable over time though the sensitivity is poor.

10 20 300

1000

2000

3000

4000

5000

Inte

nsi

ty

2

1000 1500 2000

0

250

500

750

1000

10-4

M Rh6G in film

Ra

ma

n i

nte

nsi

ty (

a.u

.)

Wavenumber (cm-1

)

after 5 minutes

after 5 hours

after 2 days

1000 1500 2000

0

100

200

300

400

10-5M 4-MPy in film

Ra

ma

n i

nte

nsi

ty (

a.u

.)

Wavenumber (cm-1

)

after 5 minutes

after 5 hours

after 2 days

1000 1500 2000

0

250

500

750

1000

10-4

M Rh6G in film

Ra

ma

n i

nte

nsi

ty (

a.u

.)

Wavenumber (cm-1

)

after 5 minutes

after 5 hours

after 2 days

1000 1500 2000

0

100

200

300

400

10-5M 4-MPy in film

Ra

ma

n i

nte

nsi

ty (

a.u

.)

Wavenumber (cm-1

)

after 5 minutes

after 5 hours

after 2 days

Electronic Supplementary Material (ESI) for NanoscaleThis journal is © The Royal Society of Chemistry 2012

Figure S13. SERS peak assignment details of different biomolecules: Tyrosine: 565 cm-

1 (ring deformation), 802 cm

-1 (tyrosine doublet), 900 cm

-1 (ring stretching), 1100 cm

-1

(amine group vibration), 1472-1500 cm-1

(CH2 deformation). Histidine: 656 cm-1

(ring

vibration), 800 cm-1

(C-H out of plane vibration), 853 cm-1

(C-C vibration, ring

vibration), 924 cm-1

(C-H in plane vibration), 1009 cm-1

(C-H in plane vibration), 1176

cm-1

(C-H stretching, N-H vibration), 1322 cm-1

(C=N vibration), 1575 cm-1

(C=C

stretching). Folic Acid: 1571 cm-1

(aromatic ring stretching), 1439 cm-1

(coupled ring

stretching), 1022 cm-1

(amine group vibration), 757 cm-1

(C-H vibration). Thiamine: 572

cm-1

(out of plane N-H deformation), 704 cm-1

(C-H deformation), 746 cm-1

(pyrimidine

ring breathing vibration), 1208 cm-1

(C-H bending and N-C-N stretching). Adenine:

727cm-1

(ring stretching), 1328 cm-1

(ring breathing). Biotin: 686 cm-1

(N-H wagging),

1026 cm-1

(C-H in plane bending), 1250 cm-1

(C-O stretching, C-C stretching, O-H in

plane bending), 1309 cm-1

(C-C stretching, C-H out of plane bending, CH-CH2

deformation).

a

b c

d

a

b

cd

a

b

ab

ab

c

d

500 1000 1500 2000

b

ac

ccd

adenine

thiamine

biotinIn

ten

sity

Raman shift (cm-1)

a

b c

d

a

b

cd

a

b

cd

a

b

ab

ab

ab

c

d

500 1000 1500 2000

b

ac

ccd

b

ac

ccd

ac

ccd

adenine

thiamine

biotinIn

ten

sity

Raman shift (cm-1)

a

b

cd

a

b

c

d

e

e

a

ab

b

c

c

d

d

e

e

f fg

g

h

h

a

a

b b bc

d

d

500 1000 1500 2000

tyrosine

histidine

folic acid

Inte

nsi

ty

Raman shift (cm -1)

a

b

cd

a

b

c

d

e

e

a

ab

b

c

c

d

d

e

e

f fg

g

h

h

a

a

b b bc

d

d

500 1000 1500 2000

tyrosine

histidine

folic acid

Inte

nsi

ty

Raman shift (cm -1)

Electronic Supplementary Material (ESI) for NanoscaleThis journal is © The Royal Society of Chemistry 2012

Procedure for the Enhancement Factor (EF) calculation:

EF has been calculated from the ratio of SERS intensity (ISERS) and Raman intensities (IR)

with respect to their respective concentration used for SERS (CSERS) and Raman (CSERS)

measurements using following equation: EF = ISERS/IR X CR/CSERS

Bulk Raman has been measured by preparing a concentrated solution of respective

molecules. The most intense SERS peak with lowest detectable concentration and their

corresponding peak in bulk Raman were used for comparison. Table 1 summarizes the

EF value and some of the SERS spectra that were used for EF calculation are shown in

Figure S8.

Table 1. EF values obtained using colloidal Au@Ag and GO along with other conditions

of measurements.

2.68 X 10919151010-81026 cm-1Folic acid

7.27 X 1081210-187310-81087 cm-1Tyrosine

5.3 X 10816185110-7800 cm-1Histidine

3.2 X 1086010-119010-9730 cm-1Adenine

HCl

1.91 X 10935167010-8750 cm-1Thiamine

HCl

1.52 X 10930145710-81026 cm-1Biotin

1.73 X 1093010-152010-9945 cm-1Fluorescein

1.15 X 10108310-196010-101170 cm-1Malachite

Green

Oxalate

2.1 X 1098510-1178310-91620 cm-1Methylene

Blue

1.14 X 10913010-1148610-91500 cm-1Rhodamine

6G

3.4 X 10123410-1117710-121100 cm-14-mercapto

pyridine

EFBulk

intensity

Bulk

concentrati

on (M)

SERS

intensity

SERS

concentrati

on (M)

SERS peak

position

Molecule

under study

2.68 X 10919151010-81026 cm-1Folic acid

7.27 X 1081210-187310-81087 cm-1Tyrosine

5.3 X 10816185110-7800 cm-1Histidine

3.2 X 1086010-119010-9730 cm-1Adenine

HCl

1.91 X 10935167010-8750 cm-1Thiamine

HCl

1.52 X 10930145710-81026 cm-1Biotin

1.73 X 1093010-152010-9945 cm-1Fluorescein

1.15 X 10108310-196010-101170 cm-1Malachite

Green

Oxalate

2.1 X 1098510-1178310-91620 cm-1Methylene

Blue

1.14 X 10913010-1148610-91500 cm-1Rhodamine

6G

3.4 X 10123410-1117710-121100 cm-14-mercapto

pyridine

EFBulk

intensity

Bulk

concentrati

on (M)

SERS

intensity

SERS

concentrati

on (M)

SERS peak

position

Molecule

under study

Electronic Supplementary Material (ESI) for NanoscaleThis journal is © The Royal Society of Chemistry 2012

Figure S14. The SERS and Raman spectra that are used for SERS EF calculation.

500 1000 1500 20000

300

600

900

1200

4-mercaptopyridine

Inte

nsi

ty (

a.u

.)

Raman shift (cm-1)

Raman (0.1M)

SERS (10-12

M)

500 1000 1500 20000

300

600

900

1200

1500

Rhodamine 6G

Inte

nsi

ty (

a.u

.)

Raman shift (cm-1)

Raman (0.1M)

SERS (10-9

M)

500 1000 1500 20000

300

600

900

1200

1500

1800 Methylene Blue

Inte

nsi

ty (

a.u

.)

Raman shift (cm-1

)

Raman (0.1M)

SERS (10-9

M)

500 1000 1500 20000

250

500

750

1000Malachite Green Oxalate

Inte

nsi

ty (

a.u

.)

Raman shift (cm-1

)

Raman (0.1M)

SERS (10-10

M)

500 1000 1500 20000

100

200

300

400

500

600

Fluorescein

Inte

nsi

ty (

a.u

.)

Raman shift (cm-1

)

Raman (0.1M)

SERS (10-9M)

500 1000 1500 20000

100

200

300

400

500

600 Biotin

Inte

nsi

ty (

a.u

.)

Raman shift (cm-1)

Raman (1M) X 4

SERS (10-8

M)

500 1000 1500 20000

100

200

300

400

500

600

700

Thiamine

Inte

nsi

ty (

a.u

.)

Raman shift (cm-1

)

Raman (1M) X 4

SERS (10-8

M)

500 1000 1500 20000

50

100

150

200

250

Adenine

Inte

nsi

ty (

a.u

.)

Raman shift (cm-1

)

Raman (0.1M)

SERS (10-9

M)

500 1000 1500 20000

150

300

450

600

Folic Acid

Inte

nsi

ty (

a.u

.)

Raman shift (cm-1

)

Raman (1M)

SERS (10-8

M)

500 1000 1500 2000 25000

200

400

600

800

1000Histidine

Inte

nsi

ty (

a.u

.)

Raman shift (cm-1

)

Raman (1M) X 10

SERS (10-7

M)

500 1000 1500 20000

200

400

600

800

1000

Tyrosine

Inte

nsi

ty (

a.u

.)

Raman shift (cm-1)

Raman (0.1M) X 10

SERS (10-8

M)

Electronic Supplementary Material (ESI) for NanoscaleThis journal is © The Royal Society of Chemistry 2012