Fluorescence turn-on chemosensor for highly selective and sensitive detection and bioimaging of al3+ in living cells based on ion-induced aggregation

Article abstract of DOI:10.1021/ac504153c

Herein, a new fluorescence turn-on chemosensor 2-(4-(1,2,2-triphenylvinyl)phenoxy)acetic acid (TPE-COOH) specific for Al³⁺ was presented by combining the aggregation-induced-emission (AIE) effect of tertaphenylethylene and the complexation capability of carboxyl. The introduction of carboxylic group provides the probe with good water-solubility which is important for analyzing biological samples. The recognition toward Al³⁺ induced the molecular aggregation and activated the blue fluorescence of the TPE core. The high selectivity of the probe was demonstrated by discriminating Al³⁺ over a variety of metal ions in a complex mixture. A detection limit down to 21.6 nM was determined for Al³⁺ quantitation. Furthermore, benefiting from its good water solubility and biocompatibility, imaging detection and real-time monitoring of Al³⁺ in living HeLa cells were successfully achieved. The AIE effect of the probe enables high signal-to-noise ratio for bioimaging even without multiple washing steps. These superiorities make this probe a great potential for the functional study and analysis of Al³⁺ in complex biosystems.

Full text of DOI:10.1021/ac504153c

Letter
pubs.acs.org/ac
Fluorescence Turn-On Chemosensor for Highly Selective and
Sensitive Detection and Bioimaging of Al3+ in Living Cells Based on
Ion-Induced Aggregation
Shilang Gui,† Yanyan Huang,‡ Fang Hu,‡ Yulong Jin,‡ Guanxin Zhang,‡ Liushui Yan,*,† Deqing Zhang,*,‡
and Rui Zhao*,‡
†School of Environment and Chemical Engineering, Nanchang Hangkong University, Nanchang 330063, China
‡Beijing National Laboratory for Molecular Sciences, CAS Key Laboratories of Analytical Chemistry for Living Biosystems and
Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
S
* Supporting Information
ABSTRACT: Herein, a new fluorescence turn-on chemosensor 2-
(4-(1,2,2-triphenylvinyl)phenoxy)acetic acid (TPE-COOH) spe-
cific for Al3+ was presented by combining the aggregation-induced-
emission (AIE) effect of tertaphenylethylene and the complexation
capability of carboxyl. The introduction of carboxylic group
provides the probe with good water-solubility which is important
for analyzing biological samples. The recognition toward Al3+
induced the molecular aggregation and activated the blue
fluorescence of the TPE core. The high selectivity of the probe
was demonstrated by discriminating Al3+ over a variety of metal
ions in a complex mixture. A detection limit down to 21.6 nM was
determined for Al3+ quantitation. Furthermore, benefiting from its
good water solubility and biocompatibility, imaging detection and real-time monitoring of Al3+ in living HeLa cells were
successfully achieved. The AIE effect of the probe enables high signal-to-noise ratio for bioimaging even without multiple
washing steps. These superiorities make this probe a great potential for the functional study and analysis of Al3+ in complex
biosystems.
fluorescence probes,11,18 which severely prevents their further
luminum, the most abundant metal of the Earth’s crust,
Aplays an important role in alimentary production,
application in environmental and biological systems.
pharmaceutical drugs, as well as the aerospace industry.1
Recently, fluorogens with an aggregation-induced emission
(AIE) effect have attracted remarkable research attention.19−21
Nowadays, because of acidic rain and human activities in the
environment, increasing exposure to free aluminum ions (Al3+)
Their unique fluorescence behavior makes them nonemissive or
weakly fluorescent in free solution but become highly emissive
poses a severe threat to biospheres and human health.2,3
Excessive intake of Al3+ has been demonstrated to cause a wide
range of diseases by accumulating in different organs of living
organisms.4 The deleterious effect of Al3+ toward the central
nervous system further makes the population at high risk for
various neurodegenerative diseases.5,6 In this regard, detection
of Al3+ in living biosystems is of great importance, not only for
monitoring aluminum contamination but also for under-
standing its biological functions.
upon aggregation.22,23 Benefiting from such activatable
fluorescence signal, chemo- and biosensors have been
developed for analyzing various species including ions,24,25
DNA,26 proteins,27 and cancer cells.28,29 As Al3+ is concerned,
Dong and colleagues designed a benzoate-based AIE probe.30
Tang and co-workers used pyridinyl-functionalized tertaphenyl-
ethylene for the sensing of trivalent ions including Cr3+, Fe3+,
and Al3+.31 However, these reported AIE fluorogens usually
work in pure organic or organic-aqueous solvents (with high
content of organic reagents), resulting in the insufficient
biocompatibility.32 Hence, novel AIE probes with high
selectivity and sensitivity is highly desirable for Al3+
quantitation and bioimaging.
Fluorescent chemosensors are receiving considerable atten-
tion owing to their rapidity, convenience, and sensitivity for
analysis.7−10 Several molecular probes based on fluorescence
off-on and/or ratiometric strategy have been reported.11−14
Nevertheless, effective design of an Al3+-specific fluorescence
sensor is still challenging, arising from relative weak
coordination and strong hydration abilities of Al3+.4 The
detection of Al3+ can be easily interfered with by the matrix,
leading to limited selectivity and sensitivity.15−17 Moreover,
poor water-solubility is another obstacle of many existing
Received: November 4, 2014
Accepted: January 20, 2015
© XXXX American Chemical Society
A
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Letter
1
Herein, a new AIE fluorescence probe 2-(4-(1,2,2-
triphenylvinyl)phenoxy)acetic acid (TPE-COOH) was pre-
sented with the above desired properties for Al3+ analysis. The
introduction of a carboxyl group into tertaphenylethylene not
only significantly enhanced the water-solubility, more impor-
tantly, it also enabled the specific complexation of Al3+. The
mechanism investigation demonstrated that the particular
molecular structure of TPE-COOH gives rise to the high
selectivity toward Al3+. Taking advantage of the AIE effect,
fluorescence turn-on bioimaging of Al3+ in living cells confirms
the great potential of the probe in analyzing living biosystems.
94% and characterized by H NMR, 13C NMR, HRMS, and
HPLC (Figures S-1−S-3, Supporting Information).
Scheme 1. Chemical Structures and Synthetic Routes to
TPE-COOH
EXPERIMENTAL SECTION
■
Fluorescence Turn-On Sensing of Al3+. The AIE
behavior of TPE-COOH was first verified by measuring its
fluorescence spectra in different mixed solvents (Supporting
Information, Figure S-4). With the attempt for the fluorescence
turn-on sensing of Al3+ in biological samples, TPE-COOH itself
should be fluorescence-silent in aqueous environment and
becomes strongly emissive while coexisting with Al3+. By using
the biological compatible DMSO as the additive, a nonemissive
TPE-COOH solution was obtained even when the water
content was as high as 98% (Figure 1a). Upon the addition of
Al3+, the expected blue fluorescence was switched on with a 52-
fold enhanced fluorescence intensity at 470 nm. Such blue
fluorescence can be detected by the naked-eye under UV light
(Figure 1a, insert). Correspondently, DLS analysis shows that
large aggregates were formed with an average diameter of 210
nm (Figure S-5, Supporting Information). Such nanoaggregates
were also clearly observed by transmission electron microscopy
(TEM) (Figure 1a, Figure S-6 in the Supporting Information).
These results suggest that Al3+ ions can initiate the aggregation
of TPE-COOH and result in the significant fluorescence
emission.
Synthesis of TPE-COOH. 4-(1,2,2-Triphenylvinyl)phenol
(compound 1) was prepared according to the reported
procedures,33 which was allowed to react with methyl
bromoacetate in the present of K2CO3 to obtain methyl 2-(4-
(1,2,2-triphenylvinyl)phenoxy)acetate (compound 2) in 82%
yield. The methanol solution (10 mL) of compound 2 (420.0
mg, 1.0 mmol) was mixed with NaOH aqueous solution (1 mL,
2.0 M) and stirred at room temperature. After 3 h, white crystal
solid was precipitated in the mixture. TPE-COOH (381.8 mg,
1
0.94 mmol) was obtained through filtration. H NMR (400
MHz, CD3OD); δ 7.05 (m, 9H), 6.98 (m, 6H), 6.88 (d, J = 8.8
Hz, 2H), 6.66 (d, J = 8.8 Hz, 2H), 4.43 (s, 2H). 13C NMR (75
MHz, CD3OD, δ): 173.0, 157.0, 144.0, 143.9, 140.6, 140.3,
136.5, 132.1, 131.0, 127.4, 127.3, 126.1, 126.0, 125.9, 113.5,
65.6. HRMS (MALDI): calcd for C28H22O3 [M], 406.1569;
found, 406.1567.
General Procedure for Fluorescence Measurement.
Stock solutions of various metal ions (0.25 mM) were prepared
with ultrapure water, respectively. A stock solution of TPE-
COOH (1 mM) was prepared with DMSO. For a typical
detection, TPE-COOH solution was mixed with the stock
solution of one metal ion, followed by the dilution with
appropriate amounts of water or water/acetonitrile. After the
incubation at room temperature for 30 min, the corresponding
fluorescence spectrum was recorded; the excitation wavelength
was 310 nm and the emission was collected from 350 to 600
nm.
To investigate such an Al3+-induced fluorescence turn-on
phenomenon, the chelation effect was first examined. The
competitive binding assay was carried out by incubation of Al3+
and TPE-COOH with a typical chelating reagent EDTA. As
shown in Figure 1a, the existence of EDTA almost completely
disabled the fluorescence emission, owing to the coordination
ability of the four carboxylates in EDTA toward Al3+. The
strong coordinative EDTA occupied the sites on Al3+ and thus
blocked the binding of TPE-COOH to Al3+. To confirm this, a
structural analogue TPE-N3, which has the same tertaphenyl-
ethylene core but is substituted with an azide group, was used
as a control. Without the carboxyl group, TPE-N3 cannot
interact with Al3+ and no fluorescence change was detected
after Al3+ treatment (Figure S-7 in the Supporting Informa-
tion). This result clearly demonstrates the important role of the
carboxyl group on TPE-COOH for Al3+ binding.
Fluorescence Imaging of Al3+ in Living Cells. The
adherent HeLa cells were washed with HEPES buffer three
times and first loaded with Al3+ (50 μM in culture media) at 37
°C for 60 min. After removal of free Al3+ by washing the cells
with HEPES buffer, TPE-COOH (20 μM in HEPES containing
2% DMSO) was added to stain the cells for 30 min. The
fluorescence images were collected directly by an Olympus
FV1000-IX81 confocal-laser scanning microscope without
further washing steps.
Selectivity of the Probe toward Al3+. To study the
selectivity of the probe, 15 metal ions with different valences
were examined as the alternative of Al3+ for the incubation with
TPE-COOH. As shown in Figure S-8 (Supporting Informa-
tion), none of these ions can turn on the fluorescence of TPE-
COOH under the same conditions, except Pb2+. The
fluorescence variation caused by Pb2+ was 57% of that induced
by Al3+. To eliminate the interference from Pb2+, acetonitrile
was chosen as the mask reagent based on its coordination
ability toward heavy metal ions.35,36 To acquire ideal mask
efficiency, the content of acetonitrile was optimized as 5%
(Figure S-9 in the Supporting Information). Under this
condition, only Al3+ can induce distinct blue fluorescence,
RESULTS AND DISCUSSION
■
Design and Synthesis. Given that oxygen can provide a
hard-base environment for the hard-acid Al3+,34 a carboxylic
group was introduced to functionalize TPE. The oxygen donor
sites of the carboxyl group were expected to induce the binding
of the probe toward Al3+. Furthermore, the molecular
aggregation effect of TPE structure was anticipated to reinforce
the stability of the complex and provide activitable fluorescence
for Al3+ sensing. The chemical structure of the target probe
TPE-COOH and its synthetic process are depicted in Scheme
1. After purification, TPE-COOH was obtained with a yield of
B
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Figure 1. (a) Fluorescence spectra of TPE-COOH (20 μM, DMSO/H2O = 2:98) in the absence and presence of Al3+ (10 μM), and fluorescence
spectrum for the mixture of TPE-COOH, Al3+, and EDTA. Inset: photographs of (1) TPE-COOH, (2) TPE-COOH + Al3+ solutions taken under
UV light, and (3) TEM image of nanoaggregates (scale bar, 200 nm). (b) Photographs of TPE-COOH (20 μM) aqueous solutions (2% DMSO, 5%
CH3CN) added with the individual metal ion under UV light; (c) fluorescence intensity of the above metal ion-added TPE-COOH solutions; (d)
fluorescence spectra of TPE-COOH (20 μM) aqueous solutions (2% DMSO, 5% CH3CN) in the presence of various metal ions (Ba2+, Fe2+, Ca2+,
Mg2+, Cr3+, Li+, Zn2+, Hg2+, Pb2+, Na+, Ag+, Fe3+, K+, Ni2+, and Cu2+) with and without Al3+ (each 10 μM).
1
Figure 2. (a) Fluorescence spectra of TPE-COOH (20 μM) upon addition of different amounts of Al3+. (b) H NMR spectra of TPE-COOH
without and with AlCl3·6H2O in DMSO-d6/D2O; insert: possible binding mode between TPE-COOH and Al3+.
1
while TPE-COOH still remains fluorescence silence after
incubating with the other metal ions (Figure 1b,c).
complex. To better understanding their binding behavior, H
NMR and FT-IR characterization were performed. In 1H NMR
spectra (Figure 2b), as Al3+ contents increased, the methylene
protons shifted downfield from 4.347 to 4.376 ppm, suggesting
that the electron deficient Al3+ probably binds the carboxyl
group on TPE-COOH and withdraws electron density from the
adjacent methylene. It is also noticeable that with an increased
amount of Al3+, signals of all TPE-COOH protons diminished.
This phenomenon is consistent with the formation of
nanoaggregates between TPE-COOH and Al3+, which thus
reduced the content of free TPE-COOH in solution. In FT-IR
spectra (Figure S-12 in the Supporting Information), the band
broadening and shifts of −COOH stretching vibrations toward
low wavenumber further confirmed the binding effect of Al3+
on the carboxyl group. On the basis of these results, coordinate
bonds were formed between the carboxylic groups of four TPE-
COOH molecules and a central Al3+ (Figure 2b). The resultant
spatial structure may just fit the ion size of Al3+ and thus leads
to the selective fluorescence turn-on of the probe.
Furthermore, to verify the ability of the probe to discriminate
Al3+ in complex samples, Al3+ was analyzed in the mixture of
the above 15 metal ions. Without any pretreatment, the mixed
ion solution containing Al3+ releases significant fluorescence,
while fluorescence signal from the solution only consisting of
15 control ions is negligible (Figure 1d). These results clearly
indicate the high selectivity of TPE-COOH for Al3+ over other
species, which can facilitate the practical detection of Al3+ in
complex biological samples.
Sensitive Quantitation of Al3+. The dependence of
fluorescence emission of TPE-COOH on the concentration
of Al3+ was investigated by incubation with Al3+ at
concentrations ranging from 0.1 to 50 μM. As shown in Figure
2a, the fluorescence at 470 nm enhances gradually as the Al3+
concentration increases. A linear range for Al3+ detection can be
determined within 0.1−5 μM (R2 = 0.9953) (Figure S-10,
Supporting Information). The detection limit of TPE-COOH
toward Al3+ is calculated to be 21.6 nM (signal/noise = 3:1),
which was much lower than many previously reported
fluorescence probes.12,16,17,32,34,37 Such high sensitivity is
enough to satisfy the U.S. EPA and FDA guidelines of 7.41
μM Al3+ for bottled drinking water. The feasibility of the probe
for the quantitative determination of Al3+ in aqueous samples
was verified by testing bottled drinking water (Supporting
Information).
Imaging Detection of Al3+ in Living Cells. The good
stability of the fluorescence switched on by Al3+ in the pH
range of 3.0−7.4 provides the probe with good suitability for
the application in bioimaging of living cells (Figure S-13,
Supporting Information). As shown in Figure 3a, no back-
ground fluorescence was observed from HeLa cells themselves,
suggesting that autofluorescence from the cells can be avoided
under this condition. For the Al3+-loaded HeLa cells, a strong
blue fluorescence was detected after incubation with TPE-
COOH (Figure 3b), demonstrating the membrane penetra-
According to Job’s Plot analysis (Figure S-11 in the
Supporting Information), Al3+ and TPE-COOH forms a 1:4
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fluorescence turn-on response to Al3+ allows the imaging
detection and real-time monitoring of Al3+ in living HeLa cells
with a high signal-to-noise ratio.
ASSOCIATED CONTENT
* Supporting Information
■
S
Additional details of a complete description of chemicals,
materials, instrumentation, method, characterization, and
quantitation determination results. This material is available
free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Authors
■
*Phone: 86-10-62557910. Fax: 86-10-62559373. E-mail:
zhaorui@iccas.ac.cn.
*E-mail: yanliushui@nchu.edu.cn.
*E-mail: dqzhang@iccas.ac.cn.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work is supported by grants from the National Natural
Science Foundation of China (Grants 21135006, 21375134,
21321003, and 21475140), Ministry of Science and Technology
of China (Grant 2015CB856303), and ICCAS (Grant CMS-
PY-201308).
Figure 3. CLSM images of HeLa cells (a) without any treatment, (b)
after sequentially incubated with Al3+ (50 μM) and TPE-COOH (20
μM in HEPES containing 2% DMSO), (c) only treated with TPE-
COOH (20 μM in HEPES containing 2% DMSO). Upper panel, blue
channel with excitation at 405 nm; lower panel, bright field. (d)
Monitoring of the binding process of TPE-COOH to Al3+-loaded cells.
Scale bar: 20 μm.
REFERENCES
■
(1) Sen, S.; Mukherjee, T.; Chattopadhyay, B.; Moirangthem, A.;
Basu, A.; Marek, J.; Chattopadhyay, P. Analyst 2012, 137, 3975−3981.
(2) Hornung, V.; Bauernfeind, F.; Halle, A.; Samstad, E. O.; Kono,
H.; Rock, K. L.; Fitzgerald, K. A.; Latz, E. Nat. Immunol. 2008, 9, 847−
856.
(3) Kochian, L. V. Annu. Rev. Plant. Phys. 1995, 46, 237−260.
(4) Verstraeten, S.; Aimo, L.; Oteiza, P. Arch. Toxicol. 2008, 82, 789−
802.
(5) Perl, D. P.; Brody, A. R. Science 1980, 208, 297−299.
(6) Cannon, J. R.; Greenamyre, J. T. Toxicol. Sci. 2011, 124, 225−
250.
(7) Wang, J.; Lin, W.; Li, W. Chem.Eur. J. 2012, 18, 13629−13632.
(8) Zhang, J. Y.; Xing, B. L.; Song, J. Z.; Zhang, F.; Nie, C. Y.; Jiao, L.;
Liu, L. B.; Lv, F. T.; Wang, S. Anal. Chem. 2014, 86, 346−350.
(9) Feng, L. H.; Zhu, C. L.; Yuan, H. X.; Liu, L. B.; Lv, F. T.; Wang,
S. Chem. Soc. Rev. 2013, 42, 6620−6633.
(10) Yuan, L.; Lin, W.; Zheng, K.; Zhu, S. Acc. Chem. Res. 2013, 46,
1462−1473.
bility of TPE-COOH and the complexation with Al3+ inside the
cells. It is noticeable that thanks to the AIE character of TPE-
COOH, a very high signal-to-noise imaging of the cell was
achieved without any washing steps. Moreover, no fluorescence
signal was detected in cells only treated with TPE-COOH
(Figure 3c), clearly demonstrating that Al3+ and its interaction
with TPE-COOH are essential for the fluorescence turn-on.
To monitor the binding process of TPE-COOH to
intracellular Al3+, a time-course assay was performed. Initially,
no fluorescence was detected in Al3+-loaded cells (Figure 3d).
After incubation for 30 min, blue fluorescence signal was
observed inside the cells, suggesting the internalization of TPE-
COOH and its binding to the preloaded Al3+ (Figure 3d). As
the incubation time was prolonged to 60 min, a greatly
intensified fluorescence was identified in the cytoplasm (Figure
3d). With longer incubation, no obvious change in fluorescence
intensity was detected, indicating the saturated binding between
the probe and Al3+. The cytotoxicity of the probe was examined
by the standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetra-
zolium bromide (MTT) assay. After incubation with TPE-
COOH for 16 h, HeLa cells remained >95% viability (Figure S-
14 in the Supporting Information), revealing good biocompat-
ibility of TPE-COOH for bioanalysis.
(11) Cao, L.; Jia, C. M.; Huang, Y.; Zhang, Q.; Wang, N.; Xue, Y. L.;
Du, D. L. Tetrahedron Lett. 2014, 55, 4062−4066.
(12) Fu, Y.; Jiang, X. J.; Zhu, Y. Y.; Zhou, B. J.; Zang, S. Q.; Tang, M.
S.; Zhang, H. Y.; Mak, T. C.W. Dalton Trans. 2014, 43, 12624−12632.
(13) Kang, R. X.; Shao, X. M.; Peng, F. F.; Zhang, Y. L.; Sun, G. T.;
Zhao, W. L.; Jiang, X. D. RSC Adv. 2013, 3, 21033−21038.
(14) Peng, L.; Zhou, Z. J.; Wang, X. Y.; Wei, R. R.; Li, K.; Xiang, Y.;
Tong, A. J. Anal. Chim. Acta 2014, 829, 54−59.
(15) Shellaiah, M.; Wu, Y. H.; Lin, H. C. Analyst 2013, 138, 2931−
2942.
CONCLUSION
■
In this work, a new fluorescence turn-on probe for Al3+ has
been developed based on the AIE effect of tertaphenylethylene
and the recognition ability of carboxyl group. The probe
exhibits good water solubility and high selectivity and sensitivity
for quantitation in an aqueous environment. It is non-
fluorescent in solution, while highly emissive upon targetable
recognition and complexation of Al3+ even in very complicated
mixtures. Taking advantage of the AIE behavior, its
(16) Barba-Bon, A.; Costero, A. M.; Gil, S.; Parra, M.; Soto, J.;
Martinez-Manez, R.; Sancenon, F. Chem. Commun. 2012, 48, 3000−
3002.
(17) Shi, X.; Wang, H.; Han, T.; Feng, X.; Tong, B.; Shi, J.; Zhi, J.;
Dong, Y. J. Mater. Chem. 2012, 22, 19296−19302.
(18) Qin, J. C.; Li, T. R.; Wang, B. D.; Yang, Z. Y.; Fan, L.
Spectrochim. Acta, Part A: Mol. Biomol. Spectrosc. 2014, 133, 38−43.
(19) Ding, D.; Li, K.; Liu, B.; Tang, B. Z. Acc. Chem. Res. 2013, 46,
2441−2453.
D
DOI: 10.1021/ac504153c
Anal. Chem. XXXX, XXX, XXX−XXX

Analytical Chemistry
Letter
(20) Shustova, N. B.; McCarthy, B. D.; Dinca, M. J. Am. Chem. Soc.
2011, 133, 20126−20129.
(21) Hong, Y. N.; Lam, J. W. Y.; Tang, B. Z. Chem. Soc. Rev. 2011, 40,
5361−5388.
(22) Wang, M.; Zhang, G. X.; Zhang, D. Q.; Zhu, D. B.; Tang, B. Z. J.
Mater. Chem. 2010, 20, 1858−1867.
(23) Zhang, G. X.; Hu, F.; Zhang, D. Q. Langmuir 2014,
DOI: 10.1021/la5029367.
(24) Huang, G. X.; Zhang, G. X.; Zhang, D. Q. Chem. Commun.
2012, 48, 7504−7506.
(25) Bian, N.; Chen, Q.; Qiu, X. L.; Qi, A. D.; Han, B. H. New J.
Chem. 2011, 35, 1667−1671.
(26) Wang, M.; Zhang, D. Q.; Zhang, G. X.; Tang, Y. L.; Wang, S.;
Zhu, D. B. Anal. Chem. 2008, 80, 6443−6448.
(27) Shi, H. B.; Liu, J. Z.; Geng, J. L.; Tang, B. Z.; Liu, B. J. Am.
Chem. Soc. 2012, 134, 9569−9572.
(28) Hu, F.; Huang, Y. Y.; Zhang, G. X.; Zhao, R.; Yang, H.; Zhang,
D. Q. Anal. Chem. 2014, 86, 7987−7995.
(29) Huang, Y. Y.; Hu, F.; Zhao, R.; Zhang, G. X.; Yang, H.; Zhang,
D. Q. Chem.Eur. J. 2014, 20, 158−164.
(30) Han, T. Y.; Feng, X.; Tong, B.; Shi, J. B.; Chen, L.; Zhi, J. G.;
Dong, Y. P. Chem. Commun. 2012, 48, 416−418.
(31) Chen, X. J.; Shen, X. Y.; Guan, E. J.; Liu, Y.; Qin, A. J.; Sun, J. Z.;
Tang, B. Z. Chem. Commun. 2013, 49, 1503−1505.
(32) Wei, T.-T.; Zhang, J.; Mao, G.-J.; Zhang, X.-B.; Ran, Z.-J.; Tan,
W.; Yu, R. Anal. Methods 2013, 5, 3909−3914.
(33) Du, X.; Qu, J.; Zhang, Z.; Ma, D.; Wang, Z. Chem. Mater. 2012,
24, 2178−2185.
(34) Jia, T. J.; Cao, W.; Zheng, X. J.; Jin, L. P. Tetrahedron Lett. 2013,
54, 3471−3474.
(35) Xu, K. J.; Hong, M. W.; Zhang, Y. C.; Song, L.; Chai, W. X. Acta
Crystallogr. 2014, 70, 858−861.
(36) Sankaralingam, M.; Balamurugan, M.; Palaniandavar, M.;
Vadivelu, P.; Suresh, C. H. Chem.Eur. J. 2014, 20, 11346−11361.
(37) Samanta, S.; Goswami, S.; Hoque, Md. N.; Ramesh, A.; Das, G.
Chem. Commun. 2014, 50, 11833−11836.
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