Gold nanoparticles modified by new conjugated S=C=N terminal and its biological imaging application

Article abstract of DOI:10.1016/j.dyepig.2017.02.004

Gold nanostructures had recently become the most interesting areas of scientific endeavor. Herein, a novel nanostructure material was designed by S1 (2, 2': 6′, 2″-terpyridyl derivative Zn(SCN)₂ complex) modified gold nanoparticles with obvious improving two photon absorption (TPA) cross section (σ), the fluorescence intensity, lifetime, fluorescence quantum yield due to the enhancement of intramolecular charge transfer (ICT) process. Compared with R1 (3-([2, 2': 6′, 2″-terpyridin]-4'-yl) -9-hexyl-9H-carbazole), a conjugated ligand of carbazolyl styryl terpyridine derivatives, capping with Ag nanoparticles, photon induced electron transfer (PET) process led to the fluorescence quenching. The ¹H NMR study on the coordination reaction mechanism provided a new insight into the great mystery of nanoscience. Other related characterizations, such as IR and Far IR, could also prove the interaction of Au NPs and S1. The composite material with good nonlinear optical properties had potential applications in?vitro cellular imaging.

Full text of DOI:10.1016/j.dyepig.2017.02.004

Accepted Manuscript
Gold nanoparticles modified by new conjugated S=C=N terminal and its biological
imaging application
Anran Wang, Wan Sun, Cong Wang, Min Xu, Xin Lu, Xiaohe Tian, Shengli Li, Jieying
Wu, Yupeng Tian
PII:
S0143-7208(16)31249-9
10.1016/j.dyepig.2017.02.004
DYPI 5778
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 24 November 2016
Revised Date: 30 December 2016
Accepted Date: 2 February 2017
Please cite this article as: Wang A, Sun W, Wang C, Xu M, Lu X, Tian X, Li S, Wu J, Tian Y, Gold
nanoparticles modified by new conjugated S=C=N terminal and its biological imaging application, Dyes
and Pigments (2017), doi: 10.1016/j.dyepig.2017.02.004.
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ACCEPTED MANUSCRIPT
Change PET to ICT through conjugated S=C=N modified by Gold nanoparticles
Gold nanostructures had recently become the most interesting areas of scientific
endeavor. Herein, a novel nanostructure material was designed by S1 (2, 2': 6',
2
''-terpyridyl derivative Zn(SCN) complex) modified gold nanoparticles with
2
obvious improving two photon absorption (TPA) cross section (σ), the fluorescence
intensity, lifetime, fluorescence quantum yield due to the enhancement of
intramolecular charge transfer (ICT) process. Compared with R1 (3-([2, 2': 6',
2
''-terpyridin]-4'-yl) -9-hexyl-9H-carbazole), a conjugated ligand of carbazolyl styryl
terpyridine derivatives, capping with Ag nanoparticles, photon induced electron
1
transfer (PET) process led to the fluorescence quenching. The H NMR study on the
coordination reaction mechanism provided a new insight into the great mystery of
nanoscience. Other related characterizations, such as IR and Far IR, could also prove
the interaction of Au NPs and S1. The composite material with good nonlinear optical
properties had potential applications in vitro cellular imaging.

ACCEPTED MANUSCRIPT
Gold nanoparticles modified by new conjugated S=C=N terminal and
its biological imaging application
‡
a
‡a
a
a
a
b
a
Anran Wang , Wan Sun , Cong Wang , Min Xu , Xin Lu , Xiaohe Tian , Shengli Li* ,
a
a
Jieying Wu , Yupeng Tian*
a
Department of Chemistry, Anhui Province Key Laboratory of Functional Inorganic
Materials, Anhui University, Hefei 230039, China;
b
School of Life Science, Center for Stem Cell Research and Translational Medicine. Anhui
University, Hefei 230039, China
†
‡
Electronic Supplementary Information (ESI) available: See DOI: 10.1039/x0xx00000x
These authors contributed equally.
Abstract
Gold nanostructures had recently become the most interesting areas of scientific
endeavor. Herein, a novel nanostructure material was designed by S1 (2, 2': 6',
2
''-terpyridyl derivative Zn(SCN) complex) modified gold nanoparticles with
2
obvious improving two photon absorption (TPA) cross section (σ), the fluorescence
intensity, lifetime, fluorescence quantum yield due to the enhancement of
intramolecular charge transfer (ICT) process. Compared with R1 (3-([2, 2': 6',
2
''-terpyridin]-4'-yl) -9-hexyl-9H-carbazole), a conjugated ligand of carbazolyl styryl
terpyridine derivatives, capping with Ag nanoparticles, photon induced electron
1
transfer (PET) process led to the fluorescence quenching. The H NMR study on the
coordination reaction mechanism provided a new insight into the great mystery of
nanoscience. Other related characterizations, such as IR and Far IR, could also prove
the interaction of Au NPs and S1. The composite material with good nonlinear optical
properties had potential applications in vitro cellular imaging.
Keywords: Gold nanoparticles; Two sulfur-terminal Zn(SCN)2 complexes;
Two-photon excited fluorescence; Biological imaging
1

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1
. Introduction
Design of chromophore-functionalized gold nanoparticles (NPs) with novel
optical and physical properties had emerged as one of the most interesting areas of
scientific endeavor over the past decades [1-5]. Carefully selecting the organics and
metal species, tuning and optimizing their optical and plasmonic properties by a
variation of their size, shape, surrounding environment and suited stabilizing agent
could contribute to obtain Au NPs with high stability and overcome the limitations of
fluorescence resonance energy transfer (FRET) and nonradiative electron transfer
from photo-excited dye molecules to Au NPs relative to traditional quenchers [6-10].
Earlier, Li et al [11], Ray et al [12], Dana et al [13] and Ming et al [14] had reported
the reason of emission enhancement of fluorophore in the presence of metal NPs due
to the local electric field increasing when the metal surface plasmon band located
between the absorption and emission band of the fluorophore [15]. This theory guided
to improve for our earlier investigations that the fluorescence quenching had been
demonstrated by energy and electron transfer between Ag NPs and terpyridine
derivatives [16]. Two sulfur-terminal Zn(SCN) complexes containing terpyridine
2
group were chosen to be capped with gold nanoparticles according to the hard and
soft acid-base theory.
Metal NPs had gained high interests in the field of nanomedicine such as
biosensing, bioimaging and recently therapy [17-19]. Metal NPs were generally
synthesized by a simple method using small organic molecules, polymeric or
biological templates to stabilize them in solution [20]. Metal NPs exhibited
molecular-like properties [21-22],
long-lifetime fluorescence in the
red-near-infrared region and large two-photon excitation. These properties
made them highly suitable for in vitro and in vivo imaging [23-27]. What’s
more, the Au NPs capped with nonlinear optical materials exhibited more
superior properties at the nonlinear optical fields and the cellular level with
high permeability and low toxicity due to near-infrared radiation when
compared with the pure metal NPs capped with polymeric or common
2

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molecular [28-31]. Although the mechanism of the fluorescent enhancing was
not fully understood, recent findings tended to confirm a coefficient
contribution of quantum confinement in the metal core and ligand-to-metal
charge transfer in the core-shell structure [32-34].
In the present investigation, to see the plasmon-exciton coupling effect and
charge delocalization form of the photo-excited dye molecules on Au NP
surface, two sulfur-terminal metal complexes containing terpyridine were
chosen which had the relatively strong gold-thiolate (Au-S) bond and good
NLO properties. Finally, a novel Au-complex composite material had been
obtained with longer fluorescent lifetime, larger two-photon absorption (TPA)
coefficient (β), TPA cross section (σ), nonlinear refractive index (γ) and third
(3)
order nonlinear optical susceptibility (χ ) than the original complex. The
further application was explored in cell imaging. The NLO material could be
effectively penetrated into cellular cytoplasm with phenomenon in two-photon
fluorescence microscopy towards HepG2 cells in vitro
.
2
. Experimental section
2
.1 Measurements and methods
All chemicals were purchased as reagent grade and used without further
purification. The solvents were dried and distilled according to standard
-1
procedures. IR spectra (4000-400 cm ), in KBr pressed pellets, were recorded
1
on a Nicolet FT-IR 170 SX spectrophotometer. H-NMR spectra were
performed on a Bruker 500Hz Ultrashield spectrometer and reported as parts
per million (ppm) from TMS (δ). Coupling constants J are given in Hertz.
UV-vis absorption spectra were measured on a UV-265 spectrophotometer. The
fluorescence spectra in solution were performed with an F-4500 fluorescence
-5
spectrophotometer. The concentration of sample solution was 1.0×10 M. The
morphologies were obtained on transmission electron microscope (TEM,
JEM-2100). Fluorescence lifetime measurements were carried out using an
HORIBA FluoroMax-4P fluorescence spectrometer equipped with a
3

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time-correlated single-photon counting (TCSPC) card. NLO properties were
measured by a femtosecond laser pulse and Ti: 95 sapphire system (680~1080
nm, 80 MHz, 140 fs, Chameleon II) as the light source, and all measurements
were carried out at room temperature. Zeta Potentials were measured by using a
o
zeta sizer ((Nano ZS90, Malvern Instruments, UK)) at a temperature of 25 C.
2
2
.2 Synthetic procedures
.2.1. Synthesis of R1
The preparation of 3-([2, 2': 6' ,2''-terpyridin]-4'-yl)-9-hexyl-9H-carbazole
(
R1) was carried out according to the reported article of previous work [35], as
shown in Scheme 1 and the relative characterizations were examined to meet
the purity requirement.
2
.2.2. Synthesis of R1-Ag NPs
Sodium borohydride were known to be strong reducing agents and suitable
for metal ion reduction. The R1-Ag NPs were obtained by the reduction of
AgNO with NaBH in DMF solution using R1 as the stabilizing agent
3
4
(
Scheme 1). In more detail, R1 power (0.0964 g, 0.2 mmol) was first dissolved
in DMF (100 mL). Then, AgNO (0.1265 g, 0.5mmol) dissolved in DMF (50
3
mL) was added into the solution with magnetic stirring at room temperature for
+
+
3
0 min. In this step, Ag ions and R1 formed translucent R1-Ag sol, and the
mixture color changed from colorless to brilliant yellow. Next, 12 mL freshly
prepared DMF solution containing 0.01M NaBH was added into the above sol
4
and instantly a pale yellow solution generated. Sequentially, the mixtures were
+
stirred for another 60 min. The color change indicated that the Ag irons were
reduced. Finally, the products were collected by centrifugation of the
precipitate, washed with distilled water-DMF mixture several times and then
dried in vacuum oven.
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2
.2.3. Synthesis of 3-([2, 2':6', 2''-terpyridin]-4'-yl)-9-hexyl-9H-carbazole Zn (SCN) 2
complex (S1)
As shown in Scheme 2, R1 (0.193 g, 0.4 mmol) was dissolved in 5 mL
CH Cl , in which 10 mL CH OH containing Zn(SCN) (0.073 g, 0.4 mmol)
2
2
3
2
was added with refluxing at 70°C for 2h. Cooled to the room temperature,
bright yellow product was crystallized from the filtered solution. 1H NMR
(
DMSO-d6, 400 MHz) (ppm): 0.82(m, 3H), 1.30(d, 6H), 1.82(s, 2H), 4.49(m,
2
4
H), 7.33(m, 1H), 7.55(m, 2H), 7.69(m, 1H), 7.86-7.96(m, 3H), 8.33-8.43(m,
H), 8.84(s, 2H), 9.06(s, 1H), 9.13-9.18(m, 3H). MS (GCT-MS),
C35H30ZnN6S2: 662.13, found: 603.18 [M+]. The crystal structure of S1 was
shown in Figure. S1
.
2
.2.4 Synthesis of S1-Au NPs
In a typical reaction, as shown in Scheme 2, the following conditions were
-6
used to prepare the Au NPs. An amount of 326 ꢀL (7.92×10 mol) of 24.3 mM
tetrachloroauric(III) acid (HAuCl ·3H O) stock solution and the desired molar
4
2
concentration of S1 were dissolved in 25 mL DMF. The mixture was then
stirred at room temperature for 1 h, which was based on the anticipated
minimum time necessary to promote precursor formation (see below). An
-5
amount of 72 ꢀL (6.3×10 mol) of 880 mM sodium borohydride (NaBH ) stock
4
solution in DMF was added over 30 min with vigorous stirring. To prepare
different size of nanoparticles, the molar concentration of HAuCl was fixed
4
and the amount of S1 was varied. With the following addition of reducing agent,
the color of the mixture immediately changed to brown or red depending on the
nanoparticle size. The mixture was then left stirring for at least 3 h and it
1
gradually progressed to final appearance. H NMR (DMSO-d6, 400 MHz)
(
ppm): 0.82(m, 3H), 1.30(d, 6H), 1.82(s, 2H), 4.49(m, 2H), 7.33(m, 1H),
7
9
.55(m, 2H), 7.69(m, 1H), 7.86-7.96(m, 3H), 8.33-8.43(m, 4H), 8.90(s, 2H),
.04-9.06 (d, 2H), 9.17-9.21(d, 2H).
5

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Scheme 1 Synthetic route for R1, R1-Ag NPs.
Scheme 2 Synthetic route for S1, S1-Au NPs
3
. Results and discussion
.1 Characterizations of R1, S1, R1-Ag NPs and S1-Au NPs
These common characterizations of TEM XRD, DLS
3
1
，
, H NMR , IR
and Far-IR of R1, S1, R1-Ag NPs and S1-Au NPs were shown in Supporting
information.
3
.2. Absorption and emission spectroscopy of R1-Ag NPs
The absorbance properties of R1 and R1-Ag NPs were first studied. As
shown in Figure. 1, two major absorption bands in the range of 250~500 nm
were observed. The ligand peaks 309 nm and 360 nm could be assigned to π–π*
transition and ICT, blue shifted to 294 nm and 338 nm for the modified NPs,
respectively. Localized surface plasma resonance (LSPR) band of Ag
nanoparticles located at about 400nm and red shifted with the time, indicating
that the electrons of silver nanoparticles (Ag NPs) transferred to ligand and led
to density increasement of R1.
The fluorescence emission peak of R1 displayed at 428 nm (Figure. 1).
Meanwhile, the emission peak of R1-Ag NPs shifted to 525 nm and quenched,
suggesting that there was a fast energy transfer and electron transfer from Ag
NPs to ligand R1. It was different with our assumption, so the S1-Au NPs
composite was designed and their optical properties were described below
according to Anger’s theory.
Fig. 1. UV-vis spectrograms and fluorescence spectra of R1, R1-Ag NPs
3
.3 Absorption spectroscopy of S1-Au NPs
Prior to demonstrate the excited state behavior, it was necessary to
examine the ground state interaction between S1 and Au NPs. Figure. S8
6

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showed the absorption spectra of S1-Au NPs, in which the localized surface
plasmon resonance (LSPR) band located at about 530 nm and red shifted with
the increase of the ratio. The band at 393 nm was assigned to ICT of S1-Au
NPs, red shifted imperceptibly when compared with free S1 (390 nm), due to
their strong coupling with surface plasmon of Au Nanoparticles [36].
The time-dependent UV-vis absorption spectrum for S1-Au NPs with the
ratio 1:1 was shown in Figure. 2. The peak of ICT decreased and red shifted.
The LSPR band enhanced with time increasing, showing the composite process
of S1 and gold particles. S1 perfectly composited with gold nanoparticles [37].
Fig. 2. Time-dependent UV-vis absorption spectra for S1-Au NPs (S1: Au=1:1)
3
.4. Emission spectroscopy of S1-Au NPs
To investigate the molecular interaction and plasmonic resonances of Au
NPs, emission spectroscopy had been carried out for S1-Au NPs. Figure. 3
showed the emission spectra of S1 with Au NPs in different concentration.
-5
-1
Here, the concentration of S1 was 1×10 mol⋅L , the molar concentration of
HAuCl was fixed and the amount of S1 was varied. The concentration of
4
S1-Au NPs was determined by the ratio. It was interesting to see that, in the
presence of 1:1, the emission peak at 541 nm was enhanced and blue shifted to
5
20nm, even part of spectral overlap between the molecular emission and
absorption of the surface plasmon. Energy transfer might take place in the
S1-Au NPs system, and the emission enhancement of fluorophore could
proceed in the presence of metal NPs. It proved the reason was the enhanced
local electric field, while the surface plasmon band of nano metal particles lied
in between the absorption band and emission band of the fluorophore [11].
The different emission peaks of S1-Au NPs located at 532 nm, 519 nm,
5
04 nm and 503 nm, respectively, with the ratio increase of S1 to Au. S1-Au
NPs composites were excited at 400 nm with blue region of the plasmon band.
7

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So emission enhancement could not be attributed to optical enhancement [38].
To understand the reason of emission intensity increment of S1 on Au NPs,
surface time-resolved emission had been studied and described in the next
section.
Fig. 3. Fluorescence spectra of S1-Au NPs (S1: Au =1:0.1, 1:1, 1:50, 1:500, 1:5000) and S1
3
.5. Time-resolved emission spectroscopy of S1-Au NPs
Figure. 4 showed the fluorescence decay of S1 and S1-Au NPs, and the
solid samples were dissolved in DMF. The average emission lifetime of S1 was
.51 ns, attributed to the lifetime of ICT state. The emission decay lifetime of
S1-Au NPs was 5.08ns could also be traced derived from the ICT process.
Meanwhile, the luminescence quantum yields (QY) were shown in Table 1
2
.
QY of S-Au NPs was enhanced from 9.77% to 23.32%. From luminescence
quantum yields and time-resolved emission studies, it was confirmed that there
was no energy transfer from photo-excited S1 to Au NPs. This indicated a
drastic increment of emission due to the ICT effect of S1 on Au NPs surface.
Further, the ability of Au NPs to store and transfer electrons increased the
attenuation number and extended the decay time. The coupled effect for surface
plasmon could lead to enhancing the stability of the excited state and
decreasing the total radiation attenuation rate [39].
Fig. 4. The fluorescence lifetime of S1 and S1–Au NPs
Table 1. Single-photon-related photo physical properties of R1, R1-Ag NPs, S1 and S1-Au
NPs
3
.6. Solvation effect of S1-Au NPs
8

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Significantly, the S1-Au NPs could easily disperse in common organic
solvents and exhibit a strong solvent-resolved fluorescence. Figure. 5 showed
the emission spectra of S1-Au NPs in seven solvents with different polarities.
The emission maximum displayed an obvious red shift upon increasing the
solvent polarity. There may be great changes in the molecular geometry of the
excited states before fluorescence emission. The fluorescence deviation in
solution could be attributed to the dipolar interaction between the solute and the
local solvent.
Fig. 5. Normalized fluorescence spectra of S1 (left) and S1-Au NPs (right) in different solvents
3
.7. Nonlinear optical properties of S1 and S1-Au NPs
In the linear absorption spectra (see Figure. 2), it was discovered that
there was no linear absorption in the wavelength range 680-910 nm for the
two-photo materials. Therefore, any emission induced by excitation at this
wavelength range should be derived from multiphoton absorption process.
By the open and closed Z-scan test methods, the nonlinear refractive index
(
γ), nonlinear absorption coefficient (β), TPA cross section (σ) and third order
(3)
nonlinear susceptibility (χ ) were shown in Table S1. and Figure. 6a, b. The
calculation process was given in S2. It was shown that the TPA cross section
(
σ) enhanced from 13368.5 GM to 16298.01 GM without the influence of pure
nano gold ( σ=2874.2 GM, Figure. S9, Table S1.). The third order nonlinear
(3)
-12
-11
susceptibility (Re (χ )[esu]) enhanced from 1.24× 10 to 1.24× 10 , for the
increased chromophore density in the complex shell might lead to increasing
the σTPA [40]. In view of the above advantages, it could be concluded that the
coupling interactions and the corresponding exciton plasmon interactions
between the Au and S1 had significant contribution to the enhancement of TPA
[
41], which stimulated the research to further explore its potential application in
biological imaging. Figure. 6c reported the optical limiting (OL) measurements
9

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for the S1-Au NPs, carried out with 790 nm laser pulses. When the input energy
2
reached about 0.48 J/cm , the transmitted energy started to deviate from the
normal line and exhibits a typical limiting effect. The damaging threshold was
2
0
.98 J/cm , suggesting that this composite was a good candidate compared to
C , which was considered as one of the best optical limiting materials [42].
60
Fig. 6. Open (a), closed (b) aperture Z-scan curves, optical limiting (c) of S1 and S1-Au NPs in
-3
-1
DMF (c = 1.0 ×10 mol⋅L )
3
.8. Application in bioimaging
Before exploring the biological applications, cytotoxicity of the
nanoparticles were measured toward the live human hepatocellular liver
carcinoma cells (HepG2) by MTT assay shown in Figure. S10. The result
indicated that the concentration from 10 to 100 mg/L of S1 and S1-Au NPs
exhibited low cytotoxicity.
As shown in Figure. 7, one- and two-photon fluorescent confocal
microscopy of HepG2 cells labeling with S1 and S1-Au NPs were captured. A
bright-field image of each cell was taken immediately prior to one- and
two-photon microscopy (2 PM) imaging. One-photon images of HepG2 cells
incubated with 20 mg/L S1 (λ = 540 nm) and S1-Au NPs (λ = 520 nm),
ex
ex
respectively. After 30 min of incubation, washed by PBS buffer, all the
emission wavelengths were from 500 to 560 nm. Two- photon images of S1
and S1-Au NPs (λ = 800 nm, λ = 540-600 nm) were obtained by the same
ex
em
process. The results indicated that the free complex S1 did not enter the cell and
S1-Au NPs evenly into the cells. The luminescence located in cell cytosol,
supposing that the S1-Au NPs permeated the phospholipids bilayer of cellular
membrane and bounded with cellular cytosol organelle. The colocalization
imaging and 3D image of S1-Au NPs (Figure. 7) could detect more clearly the
cellular targeted situation.
1
0

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Fig. 7. One- and two-photon fluorescence microscopy image of HepG2 cells incubated
with S1, S1-Au NPs (scale bar: 20ꢀm); two-photon fluorescence colocalization
imaging (bar: 5ꢀm) and 3D image of S1-Au NPs incubated with Syto9 (commercial
dyes) (λ =488 nm, λ =550 nm).
ex
em
4
. Conclusion
We designed and characterized the two-photon chromophore-functionalized gold
nanostructure, which one-photon fluorescence intensity enhancing approximately 26
times than the original dye. By studying the time-dependent absorption and
time-resolved emission decay of the free complex and S1-Au NPs, the reason why
fluorescence enhancement for S1-Au NPs is coupled effect of local electric field
enhancement and surface plasmon of Au nanoparticles. The corresponding exciton
plasmon interactions between the components S1 and Au NPs led to a larger TPA
cross section in the near-IR region. The decorated gold nanoparticles could effectively
penetrate into living cells and stained with cytosol, indicating that the composite
might be a potential excellent material in bioimaging applications.
Acknowledgments
This work was supported by a grant for the National Natural Science
Foundation of China (21271004, 51372003, 21271003, 51432001, 21101001),
the Anhui Provincial Natural Science Foundation (1308085MB24) and
Scientific Innovation Team Foundation of Educational Commission of Anhui
Province of China (KJ2012A025, 2006KJ007TD).
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Table 1 Single-photon-related photo physical properties of R1, R1-Ag NPs, S1 and
S1-Au NPs
[
a]
[b]
[c]
compound solvent λmax
τ
λmax
Φ
R1
DMF
DMF
309,
57
4.98
428
3.69
--
3
R1-Ag
NPs
294,
338,
4.83
520
4
20
S1
DMF
DMF
318,
90
2.51
5.08
541
520
9.77
3
S1-Au
NPs
329,
393,
23.32
5
30
[
a] Peak position of the absorption band; [b] Peak position of single-photon
fluorescence, excited at the absorption maximum; [c] Quantun yields determined by
using fluorescein as standard.

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Scheme 1 Synthetic routes for R1 and R1-Ag NPs.
Scheme 2 Synthetic routes for S1 and S1-Au NPs.

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Figure 1 UV-vis absorption spectra and fluorescence spectra of R1 and R1-Ag NPs.
Figure 2 Time-dependent UV-vis absorption spectra for S1-Au NPs (S1: Au=1:1).
Figure 3 Fluorescence spectra of S1-Au NPs (S1: Au =1:0.1, 1:1, 1:50, 1:500,
:5000) and S1.
1

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Figure 4 The fluorescence lifetimes of S1 and S1–Au NPs.
Figure 5 Normalized fluorescence spectra of S1 (left) and S1-Au NPs (right) in
different solvents.

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Figure 6 Open (a), closed (b) aperture Z-scan curves, optical limiting (c) of S1 and
-3
-1
S1-Au NPs in DMF (c = 1.0 ×10 mol⋅L )
Figure 7 One- and two-photon fluorescence microscopy image of HepG2 cells
incubated with S1 and S1-Au NPs, respectively (scale bar: 20ꢀm); two-photon
fluorescence colocalization imaging (bar: 5ꢀm) and 3D image of S1-Au NPs
incubated with Syto9 (commercial dyes) (λ =488 nm, λ =550 nm).
ex
em

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1
. A novel nanostructure material was designed and synthesized by S1 (2, 2': 6',
2
''-terpyridyl derivative Zn(SCN) complex) modified gold nanoparticles
2
2
. The coordination reaction mechanism was also studied between Au NPs and the
1
free ligand by the H NMR.
3
. Linear absorption and emission spectra had been systematically investigated.
. The composite material with good nonlinear optical properties had potential
applications in vitro cellular imaging.
4