Supporting Information Silver Nanoclusters Surface Motifs ...S1 Supporting Information Surface...
Transcript of Supporting Information Silver Nanoclusters Surface Motifs ...S1 Supporting Information Surface...
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Supporting Information
Surface Motifs Regulated Aggregation Induced Emission in Gold-
Silver Nanoclusters
Dipankar Baina,Subarna Maitya, and Amitava Patraa,b*
a,bSchool of Materials Sciences, Indian Association for the Cultivation of Science,
Kolkata 700 032, India
bInstitute of Nano Science and Technology, Habitat Centre, Sector 64, Phase 10,
Mohali 160062, India
*Author to whom correspondence should be addressed. Electronic mail: [email protected]
Telephone: (91)-33-2473-4971. Fax: (91)-33-2473-2805
Electronic Supplementary Material (ESI) for ChemComm.This journal is © The Royal Society of Chemistry 2020
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Experimental Section
Chemicals and methods:
Chemicals: Tetrachloroauric acid trihydrate (HAuCl4·3H2O), silver nitrate (AgNO3), N-(2-
Mercaptopropionyl)glycine, glutathione reduced (GSH), were purchased from Sigma-Aldrich.
Other chemicals such as sodium borohydride (NaBH4), sodium hydroxide granules (NaOH),
methanol, and ethanol were purchased from Merck. High purity water (∼18.2 MΩ) was used
throughout the experiment. All the chemicals of highest purity grade were used without further
purification.
Methods:
Synthesis of mono-metallic and bi-metallic nanoclusters:
Luminescent gold and gold-silver alloy nanoclusters were synthesized by two step synthesis. In
the first, polydisperse non luminescent Au nanoclusters were synthesized using N-(2-
mercaptopropionyl)glycine (MPGH) as capping agent. Then, glutathione (GSH) assisted ligand
exchange process was employed to prepare fluorescent Au and AuAg alloy cluster.
MPG-protected non luminescent Au NCs:
In a typical synthesis, 4 mL of 25mM HAuCl3.3H2O was added to a 100 mL MeOH in 200 mL
conical flask at 0°C (ice bath). Then, 160 mg of MPGH ligand was added to the reaction mixture
and the reaction was allowed to stirrer for 30 minutes. After that, freshly prepared ice cold NaBH4
(200 mg, in 20 mL water) was rapidly injected in to the reaction mixture under vigorous stirring,
and a black particles were formed immediately. The reaction was further allowed to stirring for
another 30 minutes for complete reduction. Finally, the black precipitate was collected by
centrifugation at 10000 rpm for 10 minutes. The particles washed at least two times with
methanol/water (3:1) mixture to remove the excess salts, precursor. Then, the particles was kept
overnight at room temperature to obtain dry polydisperse nanoclusters. The as prepared non
luminescent Au NCs were dissolved in water for further experiment.
Glutathione directed synthesis of Au and AuAg alloy nanoclusters:
Red emitting Au NCs were prepared from as-prepared polydisperse Au NCs; typically 1.25 mL
MPG capped Au NCs added to 8.75 mL deionized water. Then excess glutathione (307 mg) was
added to the reaction mixture and stirred at 55°C. The reaction was monitored using absorption
and photoluminescence (PL) spectroscopy, the reaction is completed within 18 hours. The as-
prepared Au NCs emits red color under the exposures of UV lamp (365 nm). For bi-metallic AuAg
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NCs synthesis different amount of AgNO3 (25 mM) was added during the ligand exchange process.
The emission maxima of AuAg NCs are changed with varying the concentration of Ag+ ion.
Typically, strong red emitting NCs (r-AuAg) is obtained when 100 µL Ag+ was added and yellow
emitting NCs (y-AuAg) was obtained upon addition of 200 µL of Ag+. The synthesis scheme of
mono-metallic Au NCs and bi-metallic AuAg NCs is illustrated in scheme 1.
Scheme 1. Schematic representation of the synthesis of Au and AuAg nanoclusters with tunable
emission
Instrumentation
The optical absorption spectra were taken with a UV-vis spectrophotometer (Shimadzu) using a
cuvette with a path length of 1 cm at room temperature. The PL spectra of all of the samples were
taken with a Fluoro Max-P (HORIBA JobinYvon) luminescence spectrophotometer. The
transmission electron microscopy (TEM) was performed on a JEOL-JEM-2100F transmission
electron microscopy system at an accelerating voltage of 200 kV. The samples for TEM analysis
were prepared by drop casting of NCs solution onto a copper grid covered by a carbon film. The
X-ray photoelectron spectroscopy (XPS) (Omicron Nanotechnology instrument) study was carried
out to determine the binding energy. Raman spectra were recorded by using Horiba JobinYvon,
(T64000 model) instrument by exciting the samples at 632 nm laser beam. Fourier-transform
infrared (FTIR) spectroscopy analyses were performed on a SHIMADZU made FTIR-8300
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spectrometer using KBr pellets. The zeta potential and dynamic light scattering (DLS) sizes were
measured with a Malveron Zetasizer instrument. For the time correlated single photon counting
(TCSPC) analysis, the samples were excited at 415 nm using a Spectra LED light source for the
measurement of phosphorescence lifetimes. The typical full width at half-maximum (FWHM) of
the system response using a liquid scatter was about 90 ps. The fluorescence decays were collected
on a Hamamatsu MCP photomultiplier. Equation (1) is used to analyze the experimental time-
resolved fluorescence decays, P(t):
n
iii tbtP )/(exp)( (1)
Here, n is the number of emissive species, b is the baseline correction (“DC” offset), and αi and τi
are, respectively, the pre-exponential factor and the excited-state fluorescence decay time
associated with the ith component. The average decay time, < τ >, is calculated from following
equation.24
(2)
n
iii
1
Where and is contribution of the decay component. iii / i
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(B)(A)
200 300 400 500 600 700 8000.0
0.3
0.6
0.9
1.2
Abso
rpba
nce
Wavelength (nm)
(C)
Fig. S1. TEM images of MPG-capped Au NCs with scale bar (A) 50 nm, (B) 20 nm and (C)
absorption spectra Au NCs and inset shows the digital picture of NCs powder.
4000 3500 3000 2500 2000 1500 1000 500
-S-H bond
Wavenumber (cm-1)
Tran
smitt
ance
(%)
GSH (A)
4000 3500 3000 2500 2000 1500 1000 500
No -S-H bond
Wavenumber (cm-1)
(B)
Tran
smitt
ance
(%)
Au-GSH
Fig. S2. FTIR spectrum of (A) glutathione (GSH), and (B) bimetallic AuAg NCs capped by GSH.
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Increasing Ag ratio in Au Ag NCs (Au:Ag)
(B)AuNC r-AuAg y-AuAg
a b c d e f
500 550 600 650 700 7500.0
2.0x105
4.0x105
6.0x105
8.0x105
1.0x106
1.2x106
1.4x106
a b c d e fPL
Inte
nsity
(a.u
)
Wavelength (nm)
(A)
Ag ratio in
AuAg NCs increases
Fig. S3. (A)Tuning of emission wavelength of Au NCs with different Au/Ag molar ratio (a) 1:0,
(b) 1:0.14, (c) 1:0.71, (d) 1:0.98, (e) 1:1.36 and (d) 1:1.51 and (B) Digital picture of corresponding
NCs under UV-light excitation (365 nm).
0 5 10 15 20 25 3005
101520253035
Num
ber
(%)
Size (nm)
Size = 11.7 nm
r-AuAg NCs(B)
0 5 10 15 20 25 300
5
10
15
20
25
30
35
Num
ber
(%)
Size (nm)
(C) y-AuAg NCs
Size = 11.1 nm
0 5 10 15 20 25 30
0
5
10
15
20
25
Num
ber
(%)
Size (nm)
(A) Au NCs
Size= 13.7 nm
Fig. S4. DLS size distribution plot of (A) Au NCs, (B) r-AuAg NCs and (C) y-AuAg NCs.
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500 550 600 650 700 750 8000.0
2.0x105
4.0x105
6.0x105
8.0x105
1.0x106
PL In
tens
ity (a
.u)
Wavelength (nm)
pH=1 pH=3 pH=5 pH=7r-AuAg NCs
Fig. S5. Absorption spectra of (a) Au NCs, (b) r-AuAg NCs and (c) y-AuAg NCs and inset shows
the zoomed view.
Fig. S6. PL spectra of r-AuAg NCs at different pHs under 400 nm excitation wavelength.
300 400 500 600 7000.0
0.2
0.4
0.6
c
b
Abs
orba
nce
Wavelength (nm)
a300 400 500 600 700 800 900
0.00
0.01
0.02
0.03
0.04
0.05
c
b
Abs
orba
nce
Wavelength (nm)
a
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600 700 8000.0
3.0x105
6.0x105
9.0x105
1.2x106
PL In
tens
ity (a
.u)
Wavelength (nm)
340 nm 360 nm 380 nm 400 nm 420 nm 440 nm
(A)
500 600 700 8000.0
2.0x105
4.0x105
6.0x105
8.0x105
PL In
tens
ity (a
.u)
Wavelength (nm)
340 nm 360 nm 380 nm 400 nm 420 nm 440 nm
(B)
Fig.S7. Excitation wavelength dependent emission spectra of (A) r-AuAg NCs and (B) y-AuAg
NCs
550 600 650 700 750 8000.0
2.0x105
4.0x105
6.0x105
8.0x105
1.0x106
PL In
tens
ity (a
.u)
Wavelength (nm)
GSH AuAg NCs
(A) (B)
AuAg NCs GSH
Fig. S8. Emission spectra of (A) AuAg NCs and control experiment without metal precursor, and
(B) digital picture of control reaction and AuAg NCs under UV-light excitation (365 nm)
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500 600 700 8000.0
2.0x105
4.0x105
6.0x105
8.0x105
1.0x106
PL In
tens
ity (a
.u)
Wavelength (nm)
Ag-GSH complex AuAg NCs
Fig. 9. Emission spectra of AuAg NCs and Ag-GSH complex.
80 82 84 86 88 90 92
Au0
AuI
AuI
Au0
4f5/2
Inte
nsity
(a.u
)
Binding Energy (eV)
(A) 4f7/2
80 82 84 86 88 90 92
4f5/2
4f7/2
AuI
AuI
Au0
Au0
Inte
nsity
(a.u
)
Binding Energy (eV)
(B)
80 82 84 86 88 90 92
4f7/2
4f5/2
AuI
Au0
AuI
Au0
Inte
nsity
(a.u
)
Binding Energy (eV)
(C)
364 368 372 3761.0x104
1.5x104
2.0x104
2.5x104
3.0x104
3d3/2
Inte
nsity
(a.u
)
Binding Energy (eV)
3d5/2(D)
Fig. S10. X-ray photoelectron spectra of Au-4f of (A) Au NCs, (B) r-AuAg NCs and (C) y-AuAg
NC. (D) XPS spectrum of Ag-3d in y-AuAg NCs, dotted line indicates position of Ag(0).
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KCl
AuAg NC AuAg NC
Fig. S11. No Ag+ ion is present in AuAg NCs as there is no precipitation of AgCl after addition of
KCl solution.
(B)(A)
Fig. S12. AFM images of (A) r-AuAg NCs and (B) y-AuAg NCs
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Fig. S13. UV-Vis absorption spectra of (A) r-AuAg and (B) y-AuAg NC with (a) fv=0%, (b)
fv=60% and (c) fv=90% ethanol/water mixture.
500 550 600 650 700 7500
1x105
2x105
3x105
4x105
5x105
Inte
nsity
(a.u
)
Wavelength (nm)
0 10 20 30 40 50 60 70 80 90
(C)
0
90
X 12
600 700 8000
1x105
2x105
3x105
PL In
tens
ity
Wavelength (nm)
0 10 20 30 40 50 60 70 80 90
(B)
0
90
X 4
500 600 7000
1x105
2x105
3x105
No ProminentChangePL
Inte
nsity
(a.u
.)
Wavelength (nm)
0 10 20 30 40 50 60 70 80 90
(A)
Fig. S14. PL spectra of (A) Au NCs, (B) r-AuAg NCs and (C) y-AuAg NCs in water-EtOH mixture
with volume fraction (fv) = 0-90%.
300 400 500 6000.0
0.2
0.4
0.6
0.8
1.0 a b c
Abs
orba
nce
Wavelength (nm)
(B)
300 400 500 6000.00
0.25
0.50
0.75
1.00
Abs
orba
nce
Wavelength (nm)
a b c
(A)
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200 300 400 500 600 700 8000.0
0.3
0.6
0.9
1.2
Nor
mal
ized
Inte
nsity
Wavelength (nm)
195 nm(B)
400 500 600 700 8000.0
0.3
0.6
0.9
1.2N
orm
aliz
ed In
tens
ity
Wavelength (nm)
307 nm(A)
Fig. S15. Stokes shift of (A) r-AuAg NCs and (B) y-AuAg, respectively.
10 20 30 40100
101
102
103
b
Cou
nts (
log)
Time (s)
a
(B)
10 20 30 40
100
101
102
103
Cou
nts (
in lo
g)
Time (s)
(A)
Fig. S16. Time resolved decay curves of (A) Au NCs and (B) r-AuAg NCs (a) fv=0% and (b) fv=
60 % ethanol (λex=415 nm).
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Table 1: Time-resolved fluorescence data of Au NCs, AuAg NCs at different emission
wavelengths
Systems Excitation(Wavelength)
Emission(Wavelength)
s) s) s) <>s)
Au NCs 400 7351.34
(0.52)2.69
(0.32)5.39
(0.16)2.42
Red-AuAg NCs400
674 1.23(0.48)
2.47(0.36)
4.95(0.16)
2.27
Red-AuAg NCs(in 60% Ethanol)
400620 1.36
(0.48)2.78
(0.33)5.57
(0.19) 2.62
Yellow-AuAgNCs
400 574 0.53(0.60)
2.14(0.40)
----- 1.17
Yellow-AuAgNCs
(in 60% Ethanol)
400564 1.15
(0.55)2.31
(0.10)4.62
(0.35)2.48