Thiolate-protected Ag clusters: Mass spectral studies of composition … · 2013-07-30 · 8 1000...

1

Electronic Supplementary Information (ESI) for:

Thiolate-protected Ag32 clusters: Mass spectral studies

of composition and insights into the Ag-thiolate

structure from NMR

T. Udayabhaskararao, M. S. Bootharaju, and T. Pradeep*

DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence (TUE), Department of Chemistry,

Indian Institute of Technology Madras, Chennai-600 036, India

*E-mail: [email protected]

Contents

Number Description Page number

S1 Schematic of synthetic process 2

S2 UV-vis spectra 3

S3 Luminescence spectra 4

S4 CD spectrum of Ag32SG19 5

S5 Comparison of UV-vis data 6

S6 MS/MS spectrum of glutathione 7

S7 ESI MS of Ag32SG19 8

S8 ESI MS of Au25SG18 9

S9 Luminescence spectra of Ag@MPG 10

S10 ESI MS of Ag32MPG19 11

S11 XPS 12

S12 FTIR 13

S13 EDAX 14

S14 XRD 15

S15 TEM, effect of electron beam irradiation 16

Electronic Supplementary Material (ESI) for NanoscaleThis journal is © The Royal Society of Chemistry 2013

mailto:[email protected]

2

NaBH4(s)

25 mg

Ground Ground

10 mL H2O

AgNO3 (s) + GSH (s)

23 mg 200 mg

Ag(I)SG +

excess GSH

Reaction mixture

I) II) III)

IV)

Electronic Supplementary Information 1

Scheme S1. Photographs representing the changes at various stages during the synthesis of Ag32SG19 clusters.

Photograph I is the initial mixture of silver nitrate and glutathione (both are colorless solids). Grinding the above for

10 minutes leads to the formation of an Ag(I)SG thiolate (photograph II). This thiolate shows a featureless spectrum

in its UV-vis profile (measured in water, data not shown). To this mixture, NaBH4(s) was added and ground

(photograph III). A 10 mL of distilled water was added to the above mixture (photograph IV). This solution contains

mixture of clusters which shows distinct peaks as shown in Figure 1a.


3

300 450 600 750 900

Ab

sorb

ance

(a.

u.)

Wavelength (nm)

b

a


Figure S2. UV-vis absorption spectra of (a) the as-synthesized crude cluster, CC and (b) the solution obtained after

keeping the crude cluster overnight at ambient conditions (giving aged crude, ACC). The spectrum of ACC is

comparable to cluster 3 (trace 3, shown in Figure 1), except for the feature at 420 nm.


4

400 480 560 640 720

In

ten

sity

(a.

u.)

Wavelength (nm)

2 nd

3 rd

Aged crude

λemi680

λemi670

λexc 420λexc 500

λexc 420λexc 490


Figure S3. Photoluminescence spectra of clusters extracted from 2nd and 3rd bands of gel electrophoresis of CC.

ACC also shows luminescence similar to cluster 3.


5

300 450 600 750-10

0

10

20

30

40

Ab

sorb

ance

(a.

u.)

Inte

nsi

ty (

md

eg)

Wavelength (nm)

a

bc


Figure S4. CD spectra of GSH (a) and Ag32SG19 (b) compared with the absorption of ACC solution (c).


6

a) b) c) d)

a) b)

Wavelength (nm)

400 600 800 1000

A

/nm

Ab

sorb

ance

Wavelength (nm)

d)


Figure S5. Absorption spectra of -SG protected Ag clusters (marked in green ellipse) from various groups, Kitaev et

al.1 (a), Bigoni et al.2 (b) and Pradeep et al.3 (c), compared with the present cluster (d). Spectra a, b and c are

reprinted from references 1, 2 and 3, respectively.


7

100 150 200 250 300

m/z

-H2O

-H2O

-NH

3

-H2O

-NH

3-H

2O

-H2O

-NH

3-C

O

-gly

cin

e

-C5H

8O3N

(SG–H)-

-C5H8O3N

176 178m/z


Figure S6. MS/MS spectrum of m/z 306 peak (anoin of glutathione) in the negative mode. Apart from the common

H2O and NH3 losses, one prominent loss is due to C5H8O3N.


8

1000 2000 3000 4000

m/z

400 600 800 1000 1200

m/z[A

g3S

G2]

-

[Ag

2SG

2]-

[Ag

2SG

]-

[Ag

SG

]-


Figure S7. ESI MS of Ag32SG19 measured in the negative mode in the range of m/z 500-4000. The peaks of interest

given in main text are in the marked region. Inset shows the ESI MS at the low mass region (m/z 400-1200). Peaks

at m/z 936, 828, 522 and 414 are assigned to [Ag3SG2-H]-, [Ag2SG2-H]-, [Ag2SG-H]- and [AgSG-H]-, respectively.


9

1000 1200 1400 1600 1800

Inte

nsi

ty

m/z

[Au25SG18-nH]q-

6-7-8-9- =q


Figure S8. ESI MS of Au25SG18, measured under the same conditions as in the case of Ag32SG19. Spectrum shows

the multiply charged species of [Au25SG18-nH]q- (where q= 6, 7, 8 and 9), which are labeled. The optimized conditions

for this measurement are reported in the instrumentation section.


10


Figure S9. Photoluminescence spectra of Ag@MPG clusters in water at room temperature.

400 500 600 700 800 900

Inte

nsi

ty

Wavelength (nm)


11

900 950 1000 2000 2500 3000

m/z

[Ag

27(M

PG

-H) 1

6Na x

H16

-x]3-

[Ag

32(M

PG

-H) 1

9Na x

H16

-x]3-

+

[Ag

5(M

PG

) 3-H

]-

[Ag

4(M

PG

) 3-H

]-

[Ag

4(M

PG

) 3-2

H+

Na]

-

× 5

i

ii

iii

a)

1020 1024 1028 1032

m/z912 915 918 921 924

m/z

i iiiii

933 936 939 942 945

m/z


Figure S10. a) ESI MS of Au32MPG19, measured in the negative mode in the range of m/z 900-3200. All the peaks

are marked with their respective ions. Sodium adduct of Ag27MPG16 is obtained due to the loss of Ag5MPG3 species

(iii) from [Ag32(MPG-H)19NaxH16-x]3-. Mass spectrum in the range m/z 1000-3200 is enhanced for 5 times in the

vertical axis. Labels i, ii and iii are [Ag4MPG3-H]-, [Ag4MPG3-H+Na]- and [Ag5MPG3-H]-, respectively. Simulated

spectra for i, ii and iii, depicted with lines match well with the experiment.


12

366 369 372 375

Co

un

ts

Binding energy (eV)

3d3/2

3d5/2

Ag 3d

160 162 164 166

2p1/2

2p3/2 S 2p

Co

un

ts

Binding energy (eV)

0 300 600 900

Co

un

ts

Binding energy (eV)

Ag

3pO

1s

Na

KL

L

N 1

sA

g 3

d

S 2

s

S 2

p

C 1

s

A

b

a

b

a

b

a

B C


Figure S11. XPS survey spectra, Ag 3d and S 2p regions (A, B and C, respectively) of the crude and Ag32SG19

clusters (traces a and b, respectively). The Ag:S atomic ratio is 1:0.57±0.03 for Ag32SG19 which matches with the

expected value 1:0.59.


13

3500 3000 2500 2000 1500 1000 500

Tra

nsm

itta

nce

%

Wavenumber (cm-1)

GSH

Ag32

SG19


Figure S12. FTIR spectra of GSH and Ag32SG19. The S−H stretching feature at 2572 cm-1 in GSH is absent in cluster

which is in agreement with the XPS data. GSH features in the region 2000-500 cm-1 confirm the presence of SG

protection of the cluster.


14

Ag L

C KO K

S KSEM

N K

Ag L

C KO K

S KSEM

N K

a) b) c)

d) e) f)


Figure S13. SEM-EDAX spectrum of Ag32SG19. (a) SEM image of the Ag32SG19 cluster aggregate from which the

EDAX spectrum is taken. Elemental maps of (b) Ag Lα, (c) S Kα, (d) O Kα, (e) C Kα and (f) N Kα are shown. Si Kα is

due to the substrate used. Ag:S atomic ratio measured is 1:0.56±0.03 which matches with the expected value of

1:0.59 for Ag32SG19.


15

20 40 60 80

(222)(311)(220)

(200)

(111)

Inte

nsi

ty (

a. u

.)

2 (degree)

b

a


Figure S14. Comparison of the X-ray diffraction patterns of glutathione protected silver nanoparticles (Ag@SG NPs)

and Ag32SG19 clusters (traces a and b, respectively). Nanoparticles show peaks corresponding to Ag planes (111),

(200) (220), (311) and (222) whereas Ag32SG19 shows a broad peak around 2θ ≈ 38o.


16

10 nm 10 nm

A) B)


Figure S15. TEM images of the Ag32SG19 before (A) and after electron beam irradiation for 5 min (B). Both are from

the same regions of the grid. QCs are strongly sensitive to electron beam exposure and they convert gradually to

larger aggregates or nanoparticles during TEM examination.

References

(1) N. Cathcart and V. Kitaev, J. Phys. Chem. C 2010, 114, 16010.

(2) S. Kumar, M. D. Bolan and T. P. Bigioni, J. Am. Chem. Soc. 2010, 132, 13141.

(3) T. Udayabhaskararao, B. Nataraju and T. Pradeep, J. Am. Chem. Soc. 2010, 132, 16304.


Thiolate-protected Ag clusters: Mass spectral studies of composition … · 2013-07-30 · 8 1000...

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Transcript of Thiolate-protected Ag clusters: Mass spectral studies of composition … · 2013-07-30 · 8 1000...