-
Chemically Modified Nanofoci Unifying Plasmonics and Catalysis
Yueliang Wang,† Lingling Fang,† Ming Gong,‡ and Zhaoxiang
Deng*,†
†CAS Key Laboratory of Soft Matter Chemistry, Hefei National
Research Center for Physical Sciences at the Microscale, Department
of Chemistry, University of Science and Technology of China, Hefei,
Anhui 230026, China ‡Engineering and Materials Science Experiment
Center, University of Science and Technology of China, Hefei, Anhui
230027, China Email: [email protected]
Experimental Details
Chemicals Chloroauric acid tetrahydrate (HAuCl4∙4H2O),
hexachloroplatinic acid hexahydrate (H2PtCl6·6H2O),
hydrogen peroxide, hydrochloric acid, Polyvinylpyrrolidone
(K30), and sodium borohydride (NaBH4) were obtained from Sinopharm
Chemical Reagent Co., Ltd. (Shanghai, China). Fish sperm DNA
(FSDNA) and sodium citrate tribasic dihydrate were bought from
Sigma. Bis (p-sulfonatophenyl) phenylphosphine dihydrate
dipotassium salt (BSPP) and sodium tetrachloropalladate trihydrate
(Na2PdCl4∙3H2O) were obtained from Strem Chemicals (Newburyport,
MA, USA). 4-nitrophenol (4-NTP) and 4-aminothiophenol (4-ATP) were
purchased from J&K Chemicals (Beijing, China). AgNO3 was a
product from Bio Basic Inc. (BBI, Canada). All reagents were used
as received without further purifications. DNA sequences
DNA oligonucleotides were custom-synthesized by Sangon
Bioengineering Technology and Services Co., Ltd. (Shanghai, China)
and purified by PAGE (unmodified DNA) or HPLC (thiolated DNA). All
DNA oligos were subject to a molecular weight verification by
MALDI-TOF mass spectroscopy. Following are the sequences (5’-3’) of
the DNA oligonucleotides used in this work (Note: underlined
sequences in sDNA and sDNAc are complementary to each other; sDNA
and sDNAc were modified versions of a sequence used in: Nano
Letters 2001, 1, 32)): sDNA (89 bases):
HS-5’GCAGTAACGCTATGTGACCGAGAAGGATTCGCATTTGTAGTCTTGAGCCCGCACGAAACCTGGACACCCCTAAGCAACTCCGTATCAGA3’
sDNAc (89 bases):
HS-5’GCAGTAACGCTATGTGACCGAGAAGGATTCGCATTTGTATCTGATACGGAGTTGCTTAGGGGTGTCCAGGTTTCGTGCGGGCTCAAGAC3’
AuNPs: AuNPs with different diameters of 23, 30, and 43 nm were
synthesized through a seeded-growth described in a previous
publication. [N. G. Bastús, J. Comenge, V. Puntes, Langmuir 2011,
27,
Electronic Supplementary Material (ESI) for Chemical
Science.This journal is © The Royal Society of Chemistry 2019
-
11098-11105]. The as-obtained citrate-capped nanoparticles were
incubated overnight with Bis (p-sulfonatophenyl)phenylphosphine
dihydrate dipotassium salt (BSPP) (0.5 mg/mL for 23 and 30 nm
AuNPs, 1 mg/mL for 43 nm AuNPs) at room temperature to accomplish a
ligand exchange. The BSPP-decorated AuNPs were collected by
centrifugation and redispersed in 0.5 mL of deionized H2O.
AIS-assembled AuNP dimers: The BSPP-capped AuNPs were added to a
0.5TBE (pH 8.0; 44.5 mM Tris, 1 mM EDTA, 44.5 mM boric acid) buffer
supplemented with 11 mM AgNO3 and 2 μg/μL FSDNA at room temperature
for 1 min. The resulting discrete AuNP clusters were further
isolated by agarose gel electrophoresis to obtain dimeric
assemblies in purified form. g-dimers and s-dimers: A 20 μL
solution of 38.8 mM sodium citrate and different volumes of 1 mM
HAuCl4 or AgNO3 were added to1 mL boiling water containing 0.1 nM
AuNP dimers. The solution was kept boiling in a 125oC oil bath, and
maintained under this condition for 20 min to obtain gold and
silver modified dimers with different junction widths. Pt-s-dimers:
To 4 mL of boiling water containing 0.1 nM s-dimers (made from 35
nm AuNPs and pre-incubated with 0.1% PVP) was added 20 L of a 20 mM
H2PtCl6 solution. The resulting mixture was stirred for 2 min in a
115oC oil bath, followed by an addition of 20 L of an aqueous PVP
solution (20 %). After a 20 min incubation with PVP, the solution
was centrifuged at 2390 g to precipitate the Pt-s-dimers, which
were then redispersed in water for further use. Pd-s-dimers: An 80
L solution containing 2.5 mM Na2PdCl4 was added to a 4mL solution
containing 0.1 nM s-dimers (made from 35 nm AuNPs and pre-incubated
with 0.1% PVP). The solution was stirred for 10 min
in an ice-water bath to obtain Pd-s-dimers. Afterwards,
20 L of a PVP aqueous solution (20 %) was introduced for an extra
protection of the products. After a 20 min incubation with PVP, the
solution was subjected to a centrifugation at 2390 g. The
precipitated Pd-s-dimers were redispersed in water for further use.
DNA-monofunctionalized 5 nm AuNPs: BSPP-capped 5 nm AuNPs
synthesized by a sodium citrate/tannic acid method (Eur. J. Cell
Biol. 1985, 38, 87-93) were combined with 5’-thiolated DNA stands
at a molar ratio of 1:0.6 (AuNP:DNA) in 0.5TBE (pH 8.0)
supplemented with 100 mM NaCl. After a 2h incubation at 20oC, the
mixture was purified by 3% agarose gel electrophoresis to obtain
monovalent DNA-AuNP conjugates. DNA multifunctionalized g-dimers:
G-dimers made from 23 nm AuNPs were combined with 5’-thiolated DNA
stands at a molar ratio of 1:500 in 250 μL of a 0.5TBE (pH 8.0)
buffer. 3.75 μL of NaNO3 (1 M) was added to this solution every 3
hours for 23 times. The final solution was centrifuged at 6120 g
with the solid pallet redispersed in the 0.5TBE buffer. This
process was repeated 3 times to remove unbound DNA stands.
DNA-directed core-satellite assemblies between g-dimers and AuNPs:
DNA-multifunctionalized g-dimers and DNA-monofunctionalized 5 nm
AuNPs bearing complementary DNA sequences were combined at a molar
ratio of 1:500 in 0.5TBE containing 150 mM NaNO3. The mixture was
kept at 37oC for 24 h to form core-satellite assemblies via DNA
hybridization. 0.6% agarose gel electrophoresis was employed to
isolate the products.
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H2O2 etching of s-dimers: Different amounts of H2O2 were added
to a 30 L solution of 1 nM 30 nm s-dimer buffered with 0.1TBE (pH
8.0) for a 20 s etching. 4-NTP decorated CMNFs: A 1 μL aqueous
droplet containing appropriate amounts of 4-NTP was added
separately to 100 μL solutions of 0.2 nM AIS-assembled AuNP dimers
(35 nm) and CMNF structures (s-dimers, Pt-s-dimers, Pd-s-dimers)
followed by a 30 min adsorption. Free unbound 4-NTP in excess was
removed by centrifugation at 2390 g with the precipitates being
redispersed in deionized water. Catalytic NaBH4 reduction of 4-NTP:
1 μL of 50 mM NaBH4 was combined with the 4-NTP-decorated Au
nanodimers and CMNFs (0.2 nM) to initiate a hydrogenation of 4-NTP
to form 4-ATP. TEM characterizations: TEM imaging was conducted on
a Hitachi HT7700 transmission electron microscope operated at an
electron acceleration voltage of 100 kV. An aqueous sample droplet
was pipetted on a carbon-coated copper grid, followed by a removal
of the liquid after a 10 min deposition. Spectroscopic
characterizations: UV-vis extinction spectra were recorded on a
Hitachi U-2910 spectrophotometer. Raman spectra were measured
for liquid samples in a low-volume quartz cuvette at room
temperature with a portable Raman spectrometer (Ocean Optics)
equipped with a Maya 2000 CCD detector and a 671 nm laser. Energy
dispersive X-ray spectroscopic (EDX) analysis: EDX element analysis
of a sample was conducted on a JEM-2100F field emission
transmission electron microscope operated at an electron
acceleration voltage of 200 kV.
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Supporting figures
16 18 20 22 24 26 28 30 320
10
20
30
40(b) (c) 42.8±3.1 nm 30.2±2.2 nm
Cou
nt
Diameter / nm
22.9±2.3 nm (a)
22 24 26 28 30 32 34 36 38 400
10
20
30
40
50
Cou
nt
Diameter / nm36 40 44 48 52 56
0
5
10
15
20
25
30
Cou
nt
Diameter / nm Figure S1. Statistical diameter
distributions of as-synthesized 23, 30, and 43 nm AuNPs used
throughout our experiments.
Figure S2. Agarose gel electrophoretic purifications of
Ag+-soldered Au nanoparticle dimers with different diameters of 23
nm (a), 30 nm (b), and 43 nm (c). The bands marked by arrows are
dimeric products which can be eluted from the gels.
-
400 600 800 1000
0.0
0.2
0.4
0.6
0.8
1.0
400 600 800 1000
0.0
0.2
0.4
0.6
0.8
1.0
400 600 800 1000
0.0
0.2
0.4
0.6
0.8
1.0 (c)(b)N
orm
aliz
ed E
xtin
ctio
n
Wavelength / nm
23 nm AuNPS 23 nm dimers
(a)
Nor
mal
ized
Ext
inct
ion
Wavelength / nm
30 nm AuNPs 30 nm dimers
Nor
mal
ized
Ext
inct
ion
Wavelength / nm
43 nm AuNPs 43 nm dimers
500 550 600 650 700 7500.0
0.2
0.4
0.6
0.8
1.0 Gap size (diameter)
0.65 nm (23 nm) 0.8 nm (30 nm) 0.9 nm (43 nm)
Nor
m. e
xtin
ctio
n cr
oss
sect
ion
Wavelength /nm
(d)
E
Figure S3. Normalized extinction spectra of (a) 23, (b) 30 and
(c) 43 nm gold nanoparticles along with their dimers assembled by
Ag+ soldering. (d) Simulations of the coupling-induced longitudinal
plasmon (BDP) resonances of the dimers indicated gap separations of
(a) 0.65 nm, (b) 0.8 nm, and (c) 0.9 nm for the 23-43 nm dimers,
respectively. Light polarization was along the dimer axis. The
simulations were carried out by a MESME algorithm developed by
Prof. García de Abajo (F. J. Garcia de Abajo, Phys. Rev. Lett.
1999, 82, 2776; F. J. Garcia de Abajo, Phys. Rev. B 1999, 60,
6086).
-
Figure S4. TEM images of gel-isolated dimeric clusters of AuNPs
with different diameters of 23 nm (a), 30 nm (b), and 43 nm
(c).
400 500 600 700 800 900 1000 1100
0.00.20.40.60.81.01.21.41.61.8
400 500 600 700 800 900 1000 1100
0.00.20.40.60.81.01.21.41.61.8
Nor
mal
ized
Ext
inct
ion
Wavelength / nm
L-AA 25 oC SC 125 oC
(a) (b)Ag
Nor
mal
ized
Ext
inct
ion
Wavelength / nm
SC 85 oC SC 125 oC
Ag
FigureS5. Extinction spectral characterizations revealing the
critical role of reaction temperature in the formation of a silver
conductive junction inside the nanogap of a strongly coupled gold
nanodimer. Silver reductions by (a) L-ascorbic acid (L-AA) at 25C
and (b) sodium citrate (SC) at 85C resulted in plasmon peaks around
400 nm (characteristic of silver nanophases) and weak, broadened
CTP peaks around 650-700 nm (related to silver junctions) due to an
over-deposition of silver outside of the nanogaps. In contrast, the
silver deposition with SC as a reductant in a 125C oil bath
produced a very sharp CTP peak at 650 nm with unresolvable plasmon
signal for the silver phase, indicating a highly preferential
silver deposition in the nanogap region. Dashed profiles show the
extinction spectra of the AIS-assembled gold nanodimer with a subnm
interparticle gap, featuring a BDP resonance at the long wavelength
side of the spectra. CTP positions are marked with triangle
symbols. Please see the following TEM images showing the typical
sample morphologies achieved in the 25C and 85C reactions.
-
FigureS6. TEM image showing typical Ag-deposited dimers at 25C
with L-AA as the reducing agent. A large portion of the structures
were unsuccessful, mainly including (1) gap-retained dimers, (2)
asymmetrically deposited dimers, and (3) CTP dimers with very thick
Ag layer around the individual particles (not gap-preferred) (note
that not all of them were marked). This result forms a sharp
contrast to Figure 3 where the reaction was conducted in a 125C oil
bath with citrate as the reductant.
-
FigureS7. TEM image showing typical Ag-deposited dimers at 85C
with SC as the reducing agent. A large portion of the structures
were unsuccessful, mainly including (1) gap-retained dimers, (2)
asymmetrically deposited dimers, (3) CTP dimers with very thick Ag
layers around the individual particles (not gap-preferred), and (4)
dissociated dimer assemblies (note that not all of them were
marked). This result forms a sharp contrast to Figure 3 where the
reaction was conducted in a 125C oil bath with citrate as the
reductant.
-
0 2 4 6 8 10 12 14 16 180
10
20
30
40
Cou
nt
CJ width
7.5±2.3 nm10 μM
(a1)
6 9 12 15 18 21 240
1020304050 15.9±1.8 nm
30 μM
Cou
nt
CJ width
(a2)
20 22 24 26 28 30 32 34 36 3805
1015202530 27.9±2.0 nm
80 μM
Cou
nt
CJ width
(a3)
3 6 9 12 15 18 210
1020304050 12.0±2.8 nm
10 μM
Cou
nt
CJ width
(b1)
12 15 18 21 24 27 30 3305
10152025
CJ width
22.5±2.9 nm60 μM
Cou
ntCJ width
(b2)
24 27 30 33 36 39 42 45 480
10
20
3032.9±3.0 nm120 μM
Cou
nt
(b3)
12 15 18 21 24 27 30 3305
10152025303540
19.3±3.6 nm20 μM
Cou
nt
CJ width
(c1)
24 27 30 33 36 39 420
5
10
15
20
25(c2) 31.6±3.4 nm
60 μMC
ount
CJ width
(c3)
30 35 40 45 50 55 60 650
10
20
30
4046.2±4.8 nm100 μM
Cou
nt
CJ width Figure S8. Statistical charts showing as-measured CJ
widths for g-dimers made of different AuNPs (a-c corresponding to
23, 30, and 43 nm AuNPs, respectively; 1-3 correspond to different
HAuCl4 concentrations as marked on each panel). Multiple TEM images
of the samples were used for the analyses.
18 21 24 27 30 330
10
20
30
40
Cou
nt
Diameter / nm
24.5±2.6 nm10 μM
(a1)
18 21 24 27 30 33 36 390
10
20
30
40
Diameter / nm
(a2) 27.0±2.6 nm30 μM
Cou
nt
21 24 27 30 33 36 39 420
10
20
30 (a3) 30.7±3.9 nm80 μM
Cou
nt
Diameter / nm
24 27 30 33 36 39 42 450
10
20
30
4033.3±3.2 nm10 μM
Cou
nt
Diameter / nm
(b1)
27 30 33 36 39 42 4505
10152025 35.0±2.8 nm
60 μM
Cou
nt
Diameter / nm
(b2)
30 33 36 39 42 45 48 510
5
10
15
20 39.9±4.1 nm120 μM
Cou
nt
Diameter / nm
(b3)
35 40 45 50 550
10203040506070 44.3±3.9 nm
20 μM
Cou
nt
Diameter / nm
(c1)
35 40 45 50 55 60 6505
1015202530 48.8±5.4 nm
60 μM
Cou
nt
Diameter / nm
(c2)
40 45 50 55 60 65 700
10
20
30
40 54.2±5.2 nm100 μM
Cou
nt
Diameter / nm
(c3)
Figure S9. Statistical charts showing the diameters of the
gold-deposited AuNPs in as-formed g-dimers. Panels a-c correspond
to 23, 30, and 43 nm diameters of original AuNPs. 1-3 correspond to
different HAuCl4 concentrations as marked on each panel. Multiple
TEM images of the samples were used for the analyses.
-
3 6 9 12 15 18 210
10
20
30
Cou
nt
CJ width
10.3±1.6 nm10 μM
(a1)
3 6 9 12 15 18 21 240
10
20
3013.2±2.5 nm20 μM
Cou
nt
CJ width
(a2)
9 12 15 18 21 24 270
10
20
30
40 18.1±2.0 nm40 μM
Cou
nt
CJ width
(a3)
6 9 12 15 18 210
5
10
15
20 11.7±2.7 nm10 μM
Cou
nt
CJ width
(b1)
5 10 15 20 25 30 350
10
20
3019.6±4.7 nm30 μM
Cou
ntCJ width
(b2)
15 18 21 24 27 30 3305
1015202530 24.5±2.6 nm
50 μM
Cou
nt
CJ width
(b3)
6 9 12 15 18 210
10
20
3012.5±2.1 nm10 μM
Cou
nt
CJ width
(c1)
10 15 20 25 30 35 400
10
20
30 24.6±2.7 nm25 μM
Cou
nt
CJ width
(c2)
20 30 40 50 600
5
10
15
20
2541.7±5.5 nm90 μM
Cou
nt
CJ width
(c3)
Figure S10. Statistical charts showing as-measured CJ widths for
s-dimers made of different AuNPs (a-c corresponding to 23, 30, and
43 nm AuNPs, respectively; 1-3 correspond to different AgNO3
concentrations as marked on each panel). Multiple TEM images of the
samples were used for the analyses.
20 22 24 26 28 3005
1015202530
Cou
nt
Diameter / nm
24.7±3.5 nm10 μM
25.6±2.7 nm20 μM
26.1±1.2 nm40 μM
(a1) (a2)
20 22 24 26 28 30 3205
1015202530
Cou
nt
Diameter / nm22 24 26 28 30 32
05
10152025
Cou
nt
Diameter / nm
(a3)
24 27 30 33 36 39 4205
10152025
Cou
nt
Diameter / nm
31.9±2.9 nm10 μM
(b1)
27 30 33 36 39 42 4505
1015202530
Cou
nt
Diameter / nm
34.2±3.1 nm22 μM
35.3±3.2 nm50 μM
(b2) (b3)
(c1) (c2) (c3)
27 30 33 36 39 4205
1015202530
Cou
nt
Diameter / nm
30 35 40 45 50 55 6005
1015202530
Cou
nt
Diameter / nm
44.4±4.5 nm10 μM
46.4±4.8 nm25 μM
49.1±4.8 nm90 μM
35 40 45 50 550
8
16
24
32
Cou
nt
Diameter / nm35 40 45 50 55 60 65
05
10152025
Cou
nt
Diameter / nm
Figure S11. Statistical charts showing the diameters of the
silver-deposited AuNPs in as-formed s-dimers. Panels a-c correspond
to 23, 30, and 43 nm diameters of original AuNPs. 1-3 correspond to
different AgNO3 concentrations as marked on each panel. Multiple
TEM images of the samples were used for the analyses.
-
Figure S12. EDX analysis showing the Au and Ag element profiles
along the dimer axis of a 30 nm s-dimer, indicating an enriched
distribution of Ag in the gap region.
Figure S13. Photographs of as-formed g-dimers after reacting
with different amounts of HAuCl4. The control samples were original
Ag+-soldered dimers. These pictures show a clear color transition
and a good water solubility of the products.
Figure S14. Photographs of as-formed s-dimers after reacting
with different amounts of AgNO3. The control samples were original
Ag+-soldered dimers. These pictures show a clear color transition
and a good water solubility of the products.
-
Figure S15. Agarose gel electropherograms of as-formed g-dimers
after reacting with different amounts of HAuCl4. The control
samples were original Ag+-soldered dimers. These data show a good
purity and colloidal stability of the samples.
Figure S16. Agarose gel electropherograms of as-formed s-dimers
after reacting with different amounts of AgNO3. The control samples
were original Ag+-soldered dimers. These data show a good purity
and colloidal stability of the samples.
-
400 500 600 700 800 900 1000 1100
0.0
5.0k
10.0k
15.0k
20.0k
25.0k
400 500 600 700 800 900 1000 1100
0.0
10.0k
20.0k
30.0k
40.0k
50.0k
400 500 600 700 800 900 1000 1100
0.0
20.0k
40.0k
60.0k
80.0k
100.0k
400 500 600 700 800 900 1000 1100
0.0
5.0k
10.0k
15.0k
20.0k
25.0k
30.0k
35.0k
400 500 600 700 800 900 1000 1100
0.0
10.0k
20.0k
30.0k
40.0k
50.0k
60.0k
70.0k
400 500 600 700 800 900 1000 1100
0.0
20.0k
40.0k
60.0k
80.0k
100.0k
Ext
inct
ion
cros
s se
ctio
n /n
m2
Wavelength /nm
30.7 nm (27.9) 19.1 nm (15.9) 12.5 nm (7.5)
(a1)
(a2)
(a3)
(b1)
(b2)
(b3)
Ext
inct
ion
cros
s se
ctio
n /n
m2
Wavelength /nm
39.9 nm (32.9) 24.7 nm (22.5) 14.2 nm (12.0)
Ext
inct
ion
cros
s se
ctio
n /n
m2
Wavelength /nm
54.2 nm (46.2) 37.6 nm (31.6) 17.6 nm (19.3)
Ext
inct
ion
cros
s se
ctio
n /n
m2
Wavelength /nm
18.8 nm (18.1) 15.4 nm (13.2) 13.0 nm (10.3)
Ext
inct
ion
cros
s se
ctio
n /n
m2
Wavelength /nm
26.7 nm (24.5) 21.7 nm (19.3) 14.8 nm (11.7)
Ext
inct
ion
cros
s se
ctio
n /n
m2
Wavelength /nm
47.1 nm (41.7) 29.9 nm (24.6) 17.5 nm (12.5)
Figure S17. BEM calculated theoretical CTP profiles of
different g-dimers (a) and s-dimers (b) based on two simplified
models shown above. Light polarizations were along the dimer axes.
Different CJ widths were adopted during the calculations to fit
experimentally observed CTP positions (see Figure 4). The values in
brackets are measured CJ widths based on TEM data, which show a
good consistency with simulated ones.
-
300 400 500 600 700 800 900 1000 1100
0
20000
40000
60000
80000
100000
120000
140000Ag
Ext
inct
ion
cros
s se
ctio
n /n
m2
Wavelength /nm
Au
42.5 nm
40.0 nm
85.0 nm
19.3 nm
42.5 nm
Figure S18. BEM calculated theoretical extinction profiles
of different CTP dimers. Light polarizations were along the dimer
axes. From the bottom up in the schematic drawings are: a 40 nm
g-dimer bearing a 1.25 nm thick gold coating and a 19.3 nm wide Au
CJ (blue curve), a 42.5 nm AuNP dimer connected by a 19.3 nm thick
Ag CJ (green curve), a 40 nm s-dimer bearing a 1.25 nm thick Ag
coating and a 19.3 nm wide Ag CJ (red curve), and a 42.5 nm AgNP
dimer connected by a 19.3 nm wide Ag CJ (black curve).
400 500 600 700 800 900 1000 1100
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Nor
mal
ized
Ext
inct
ion
Wavelength / nm
0 1.7 2.7 3.3 6.7 50 100
[H2O2] / 102 μM:
Figure S19. Normalized extinction spectra of s-dimers
prepared from 40 nm AuNP dimers after an etching by different
concentrations of H2O2.
-
Figure S20. (a) Photographs of H2O2-etched s-dimers synthesized
from 40 nm AuNP dimers. (b) Agarose gel electrophoretic data
showing a good purity and colloidal stability the H2O2-etched
s-dimers shown in (a). The samples from left to right correspond to
increased H2O2 concentrations.
Figure S21. TEM images of s-dimers prepared 40 nm AuNP dimers
after an etching by different concentrations of H2O2.
400 600 800 1000 1200
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
400 600 800 1000 1200
0.00.20.40.60.81.01.21.41.61.8
400 600 800 1000 1200
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Nor
mal
ized
Ext
inct
ion
Wavelength / nm
s-dimers s-dimers + H2O2
(a) (b) (c)
Nor
mal
ized
Ext
inct
ion
Wavelength / nm
s-dimers Pt-s-dimers Pt-s-dimers + H2O2
Nor
mal
ized
Ext
inct
ion
Wavelength / nm
s-dimers Pd-s-dimers Pd-s-dimers + H2O2
Figure S22. UV-visible extinction spectra of 30 nm s-dimers (a),
Pt-s-dimers (b), and Pd-s-dimers (c) before and after a silver
etching by H2O2. The negligible spectral changes for the
Pt-s-dimers and Pd-s-dimers after the H2O2 etching indicate minimal
silver residuals after the Pt and Pd displacements. CTP positions
are marked with triangle symbols.
-
Figure S23. Pt-s-dimers (a) and Pd-s-dimers prepared by Galvanic
displacements of s-dimers with minimum Ag deposition.
400 600 800 1000
0.0
0.2
0.4
0.6
0.8
1.0
1.2
400 600 800 1000
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Nor
mal
ized
Ext
inct
ion
Wavelength / nm
dimers s-dimers Pt-s-dimers
(a) (b)N
orm
aliz
ed E
xtin
ctio
n
Wavelength / nm
dimers s-dimers Pd-s-dimers
Figure S24. Normalized extinction spectra of Pt-s-dimers
(a) and Pd-s-dimers (b) prepared by Galvanic displacements of 35 nm
s-dimers with minimum Ag depositions. The weakened and redshifted
CTP peaks for the Pt-s-dimers and Pd-s-dimers compared to
corresponding s-dimers were a result of silver replacement.
-
1000 1200 1400 1600 18001000 1200 1400 1600 18001520 1600
Inte
nsity
/ a.
u.
Raman Shift / cm-1
C4-NTP= 250 μM(a)
Reaction tim
e / min
0
2610141820222426
0
Reaction tim
e / 10s2
6
10
1416182024
(b) (c)C4-NTP= 100 μM
Figure S25. Time-course SERS spectra measured on 35 nm
Pd-s-dimers showing the catalytic conversion from 4-NTP to 4-ATP
after being reduced by NaBH4. The 4-NTP-decorated Pd-s-dimers were
prepared in the presence of 250 μM (a) and 100 μM (b) 4-NTP
molecules. The catalytic conversion was obvious at a low 4-NTP
coverage (panels b and c in contrasting to panel a). Panel c is a
zoom-in view of the marked part in panel b.
1000 1200 1400 1600 18000
1k
2k
3k
4k
Inte
nsity
Raman Shift / cm-1
4-ATP
4-NTP
× 5
Figure S26. SERS spectra of chemically pure 4-NTP and
4-ATP molecules adsorbed on strongly coupled AuNP (30 nm in
diameter) dimers obtained by AIS. The concentrations of 4-NTP and
4-ATP were 10-5 M.
-
0.0
0.2
0.4
0.6
0.8
1.0
1.2
400 600 800 10000.0
0.2
0.4
0.6
0.8
1.0
1.2
400 600 800 1000 400 600 800 1000 400 600 800 1000
Original 4-NTP adsorbed After reaction
(a1) 10 μM 10 μM Original 4-NTP adsorbed After reaction
(b1) Original 4-NTP adsorbed After reaction
(c1) 500 μM Original 4-NTP adsorbed After reaction
(d1)
Original 4-NTP adsorbed After reaction
Nor
mal
ized
Ext
inct
ion
(a2) 2 μM 2 μM Original 4-NTP adsorbed After reaction
Wavelength / nm
(b2)
dimers s-dimers Pt-s-dimers Pd-s-dimers
Original 4-NTP adsorbed After reaction
(c2) 250 μM
250 μM
Original 4-NTP adsorbed After reaction
(d2) 100 μM
Figure S27. Normalized extinction spectra of AuNP dimers and
different CMNFs before and after the SERS measurements. The slight
changes to the BDP peaks were a result of 4-NTP and NaBH4
treatments that slightly altered the dielectric environments and
gap separations of the nanofoci.
-
Figure S28. TEM images of AuNP dimers (a), s-dimers (b),
Pt-s-dimers (c), and Pd-s-dimers (d) after interacting with 4-NTP
and NaBH4. These samples corresponded to the data in Figure 6.
-
1000 1200 1400 1600 1800 1000 1200 1400 1600
Inte
nsity
/ a.
u.
Raman Shift / cm-1
Illumination Tim
e / min
20181614121086420
Inte
nsity
/ a.
u.
(a) (b1)
(b2)
(b3)
Raman Shift / cm-1
Original 1 min
Original 8 min
×5
Original 6 min
×5
Figure S29. Evidences in support of the fact that only
chemical catalysis was responsible for the conversion from 4-NTP to
4-ATP in the plasmonic hotspot of CMNFs. (a) Unvaried SERS signals
of 4-NTP molecules adsorbed on Pt-s-dimers for different
irradiation times of the 671 nm excitation laser in the absence of
the chemical reductant NaBH4. (b) Under a constant laser
illumination for relatively short time of 10 s during each
measurement, a prolonged incubation with NaBH4 increased the yield
of 4-ATP. Shadowed peaks correspond to characteristic vibrations of
4-NTP (grey and cyan) and 4-ATP (red). A complete conversion of
4-NTP into 4-ATP happened after an 8-min reaction as judged by the
disappearance of 4-NTP signals. Because homogeneous solution-based
samples were employed for the SERS measurements, any light-induced
processes would be invisible due to a rapid diffusion of the CMNFs
carrying the product molecules out of the laser focusing point.
These results clearly indicate that the conversion from 4-NTP to
4-ATP was due to chemical catalysis, not related to the laser
irradiation during SERS measurements.
-
1000 1200 1400 1600 1800 1000 1200 1400 1600 1800 1000 1200 1400
1600 1800
Illumination Tim
e / min
6050403020100
(d) 671 nm
6050403020100
Illumination Tim
e / min
(e) 671 nm
6050403020100
Illumination Tim
e / min
(f) 671 nm
Inte
nsity
/ a.
u.
6040200
Illumination Tim
e / min
(a) 532 nmdimers s-dimers Pt-s-dimers
6040200
Illumination Tim
e / min
(b) 532 nm
6040200
Illumination Tim
e / min
(c) 532 nm
Illumination Tim
e / min
6050403020100
(g) 671 nm
Raman Shift / cm-1
Illumination Tim
e / min
6050403020100
(h) 671 nm
Illumination Tim
e / min
6050403020100
(i) 671 nm
Figure S30. SERS spectra showing plasmon-driven dimerizations of
4-NTP into DMAB (4,4'-dimercaptoazobenzene) in the hotspots of gold
nanodimers, s-dimers, and Pt-s-dimers. (a-c) Irradiation by a 532
nm laser (unmatched with the hotspot resonance) did not generate a
DMAB product, as evidenced by SERS measurements with a 671 nm laser
at a lowered (10%) intensity and shortened (40 s) overall
illumination time to alleviate its plasmon effect. (d-i)
Irradiation by a 671 nm laser at 45% (d-f) and 100% (g-i) of its
full power led to clearly observable Raman signals (marked with
green shadowed areas) of DMAB. The yield of DMAB was explicitly
related to the laser intensity. The effectiveness of the 671 nm
laser for the plasmon-driven reaction is well-understood
considering the significantly red-shifted hotspot LSPR. Note that
the CMNFs were deposited on a quartz substrate for the SERS
measurements in order to avoid a quick diffusion of the DMAB
products out of the laser focus points.
-
Figure S31. TEM images of DNA-linked 23 nm AuNP dimers before
(a) and after (d) an AIS treatment, and the corresponding gold (b,
e) and silver (c, f) modified nanodimers (i.e. g-dimers and
s-dimers) prepared from (a) and (b) in the absence (b, c) and
presence (e, f) of the AIS treatment. Insets show photographs of
corresponding solutions.
400 600 800 1000 1200
0.0
0.2
0.4
0.6
0.8
1.0
1.2
400 600 800 1000 1200
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Nor
mal
ized
Ext
inct
ion
Wavelength / nm
DNA-linked dimers DNA-linked dimers@Au Soldered dimers Soldered
dimers@Au
(a) (b)
Nor
mal
ized
Ext
inct
ion
Wavelength / nm
DNA-linked dimers DNA-linked dimers@Ag Soldered dimers Soldered
dimers@Ag
Figure S32. UV-visible extinction profiles of DNA-linked
23nm AuNP nanodimers, their AIS-treated structures, along with the
gold (a) and silver (b) modified samples (i.e. g-dimers and
s-dimers) based on the DNA-linked dimers with or without the AIS
treatment. The AIS-treated dimers show a new resonance peak
corresponding to the BDP mode. CTP peaks generated after a metal
filling of the interparticle gaps are marked with triangle
symbols.
-
Figure S33. (a) Gel electrophoretic data showing a successful
high density DNA functionalization of g-dimers, and their assembly
with 5 nm AuNPs to form core-satellite structures. Lanes 1-5
correspond to 5 nm AuNPs (lane 1), ssDNAc mono-conjugated 5 nm
AuNPs (lane 2), g-dimers (lane 3), ssDNA multi-functionalized
g-dimers (lane 4), and DNA-directed core-satellite assemblies (lane
5). (b) TEM images showing the as-formed core-satellite structures
with g-dimers cores (prepared from 23 nm AuNPs) and 5 nm AuNP
satellites.