New switch on fluorescent probe with AIE characteristics for selective and reversible detection of mercury ion in aqueous solution

Article abstract of DOI:10.1016/j.ab.2019.113403

A new tetraphenylethylene derivative based fluorescenct probe (probe 2) was synthesized in a simple two-step process for selectively switch on and reversible detection of Hg²⁺ in aqueous solution based on aggregation-induced emission phenomenon

Full text of DOI:10.1016/j.ab.2019.113403

AnalyticalBiochemistry585(2019)113403
Contents lists available at ScienceDirect
Analytical Biochemistry
journal homepage: www.elsevier.com/locate/yabio
New switch on fluorescent probe with AIE characteristics for selective and
reversible detection of mercury ion in aqueous solution
Yanglei Yuana, Xin Chena, Qing Chenb, Guoyu Jiangc,d, Hongmei Wanga,∗, Jianguo Wangc,d,∗∗
a Department of Applied Chemistry, China Agricultural University, Beijing, 100193, PR China
b College of Resource and Environmental Science, China Agricultural University, 100193, Beijing, China
c College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot, 010021, PR China
d Key Laboratory of Organo-Pharmaceutical Chemistry, Gannan Normal University, Ganzhou, 341000, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords:
Mercury
Fluorescent probe
Aggregation-induced emission
Switch on
A new tetraphenylethylene derivative based fluorescenct probe (probe 2) was synthesized in a simple two-step
process for selectively switch on and reversible detection of Hg2+ in aqueous solution based on aggregation-
induced emission phenomenon. Probe 2 exhibited weak emission in aqueous solution due to the fast non-ra-
diative decay of the excited singlet state facilitated by the free rotation of four phenyl rotors. While after co-
ordination with Hg2+, the Hg2+-promoted aggregation formation will occur and restrict the intramolecular
rotation, which blocks the non-radiative pathways and opens up the emission channel, resulting in the switch on
response of probe 2 toward Hg2+. Probe 2 exhibited high sensitivity and good selectivity toward Hg2+ with a
detection limit of 45.4 nM. Moreover, the detection can be reversible by subsequent addition of S2- into the
detection system, which may be applied in the removal of toxic Hg2+ from water. Elsevier B.V. All rights
reserved.
Reversible detection
1. Introduction
chromatography (GC), high performance liquid chromatography
(HPLC), inductively coupled plasma mass spectrometry (ICP MS), X-ray
As a heavy and transition metal ion, mercury (Hg2+) is considered
to be highly toxic and dangerous to human health and the environment
[1]. Environmental Hg2+ can be easily converted by aerobic organisms
to more toxic methylmercury, which can readily enter biological
membranes due to their lipid solubility, leading to sever neurotoxicity
to many eukaryotes including fish, animals and finally humans through
food-chain accumulation [2]. Nowadays, Hg2+ has severely con-
taminated water, air, land and the food chain due to man-made activ-
ities [3]. And long expose to high levels of Hg2+ may results in lasting
and highly harmful effects in biological systems, causing various dis-
eases including cognitive and motion disorders, language, hearing, vi-
sion and hair loss, prenatal neutron and brain damage, Minamata dis-
ease and even death [4,5]. Due to the high threat of Hg2+ to human
beings, the maximum allowed amount of Hg2+ in drinking water
(2 ppb, ca. 10 nM) was set by the U.S. Environmental Protection Agency
(EPA) [6], which also manifested the great significance of developing
reliable methods for the highly sensitive and selective detection of
Hg2+ in aqueous solutions.
fluorescence spectrophotometry, atomic absorption spectroscopy
(AAS), and neutron activation analysis [7–11], may greatly suffer from
costly and complicated equipments, long data acquisition time and/or
the involvement of skilled personnel. Fluorescent probes, featured with
the unique advantages of high specificity and sensitivity, simple op-
eration, non-invasiveness and applicability to real-time and online
bioimaging, have aroused great interest in the rapid and convenient
assay of various analytes, especially biologically relevant species
[12–21]. A large number of fluorescent probes have already been re-
ported in recent years to realize the easy and quick sensing of Hg2+
[22–27]. However, the OFF response could not be differentiated with
the false signal induced by quenching of Hg2+. Moreover, most fluor-
escent probes for Hg2+ were fabricated based on traditional aggrega-
tion-caused quenching (ACQ) fluorophores, which may also bring about
interference from the quenching of emission in high concentration so-
lutions or after they accumulated in cells [28,29].
To prevail the ACQ effect, the concept of aggregation-induced
emission (AIE) was put forward by Tang et al., in 2001 [28,29]. The AIE
Luminogens (AIEgens) exhibit opposite emission behaviours compared
Traditional detection methods for Hg2+
,
such as gas
∗ Corresponding author.
∗∗ Corresponding author. College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot, 010021, PR China.
E-mail address: whmd@cau.edu.cn (H. Wang).
https://doi.org/10.1016/j.ab.2019.113403
Received 23 April 2019; Received in revised form 19 August 2019; Accepted 20 August 2019
Availableonline26August2019
0003-2697/©2019ElsevierInc.Allrightsreserved.

Y. Yuan, et al.
AnalyticalBiochemistry585(2019)113403
formation will occur and restrict the intramolecular rotation, which
blocks the non-radiative pathways and opens up the emission channel,
resulting in the switch on response of probe 2 toward Hg2+. Probe 2
exhibited high sensitivity and good selectivity toward Hg2+ with a
detection limit of 45.4 nM. What's more, the detection can be reversible
by subsequent addition of S2- into the detection system, which may be
applied in the removal of toxic Hg2+ from water.
2. Experimental
2.1. General information
Scheme 1. Schematic representation of switch on and reversible detection of
Hg2+ by probe 2 in aqueous solutions.
All solvents were purified and dried following standard procedures
unless special statements. Other chemical reagents were commercial
available and used as received.
to traditional ACQ fluorophores, that is, they are weakly or non-emis-
sive in solution but give bright emission in the aggregation and solid
state. The AIE mechanism has mainly been attributed to the restriction
of intramolecular motion (RIM), which blocks the non-radiative path-
ways and opens up the emission channel in the aggregation state
[30–34]. By now, numerous fascinating AIE probes for various biolo-
gical-relevant species such as, metal ions, proteins, DNA, enzymes, have
been fabricated through well tuning of the aggregation/disaggregation
conditions of AIEgens [30–34]. In fact, a number of fluorescent probes
for Hg2+ have been developed based on AIEgens [35–45]. However,
most of the AIE sensors still exist some drawbacks such as low sensi-
tivity, switch off response and poor practicability which required a
much high content of organic solvents in aqueous solutions to afford
proper handling of the detection process [46–53]. Fluorescent probes
with the features of rapid, sensitive, highly selective and reversible
detection of Hg2+ in aqueous solution through a switch on mode is still
in high demand.
Herein, we designed a new AIE fluorescent probe (probe 2 in
Scheme 1) for switch on and reversible detection of Hg2+ in aqueous
solution. As shown in Scheme 1, we chose 2-(aminooxy)acetic acid as a
chelator for Hg2+. The reaction between 2-(aminooxy)acetic acid and
4-(1,2,2-triphenylvinyl)benzaldehyde (shown in Scheme 2) can easily
afford a Schiff base compound 2 with high yield (92%). Fortunately,
probe 2 was rendered some water solubility due to the presence of
carboxylic acid group, which is favorable for its application in biolo-
gical and environmental samples. Moreover, the emission of probe 2 in
aqueous solution was very weak due to the rotation of phenyl rings.
While after coordinated with Hg2+, the Hg2+-promoted aggregation
1H NMR spectra were obtained on a Brucker DMX-300MHz spec-
trophotometer. High resolution mass spectra were obtained on Brucker
APEX IV (7.0 T) FT_MS. UV–Vis absorption spectra and fluorescence
emission spectra were recorded on a Shimadzu UV-1601PC spectro-
photometer and a Hitachi F-4500 fluorescence spectrophotometer, re-
spectively. Dynamic light scattering (DLS) experiments were carried out
with Malvern Instrument (Nano Series). Confocal fluorescence imaging
experiments were performed with an Olympus FV-1000 laser scanning
microscopy system, based on an IX81 (Olympus, Japan) inverted mi-
croscope. The microscope was equipped with 375 nm (CW) laser lines
and UPLSAPO 60x/N.A 1.42 objective. Images were collected and
processed with Olympus FV10-ASW Ver.2.1b software.
2.2. Synthesis
2.2.1. Compound 2-b
To a THF solution (100 mL) of diphenylmethane (18.0 g, 107 mmol)
at 0 °C was added a solution of n-BuLi in hexane (2.5 M). The mixture
was stirred for 30 min to result in an orange solution of 2-a. To the
solution of 2-a, (4-bromophenyl) (phenyl)methanone (26.1 g,
100 mmol) was added at 0 °C. After that, the mixture was continuously
stirred at room temperature for another 6 h. Saturated NH4Cl was
added to quench the reaction. The reaction mixture was filtered under
reduced pressure and the resultant was dried to obtain compound 2-b.
Compound 2-b (36.0 g, 84 mmol) was dissolved in 10 mL of toluene and
p-toluenesulfonic acid was added as a catalyst. The reaction mixture
was refluxed overnight and purified by silica chromatography using
ethyl acetate and petroleum ether (1/100, v/v) as the eluent. Yield:
Scheme 2. Synthetic route of probe 2.
2

Y. Yuan, et al.
AnalyticalBiochemistry585(2019)113403
96%.
3. Results and discussion
To a solution of compound 2-c in 15 mL of THF at −78 °C, n-BuLi
(3 mL, 1.6 M, 4.86 mmol) in hexane (3 mL) was added dropwise. The
mixture was stirred at −78 °C for 2 h before quickly adding anhydrous
DMF (1.1 mL, 14.56 mmol). The mixture was stirred at temperature for
another 6 h. The mixture was washed with brine and extracted with
dichloromethane twice. The organic layer was combined and dried over
anhydrous Na2SO4, filtered and evaporated. The residue was subjected
to column chromatography with ethyl acetate/petroleum ether (95/5,
v/v) as eluent to obtain compound 2-d as a solid. Yield: 45%. 1H NMR
(300 MHz, CDCl3) δ 9.92 (s, 1H), 7.64 (d, J = 8.3 Hz, 2H), 7.23 (d,
J = 8.2 Hz, 2H), 7.17–7.10 (m, 9H), 7.09–7.02 (m, 6H). 13C NMR
(75 MHz, CDCl3) δ 191.51, 150.22, 142.73, 142.68, 142.58, 139.46,
133.99, 131.62, 130.97, 130.95, 130.91, 128.83, 127.62, 127.61,
127.43, 126.73, 126.57, 126.54.
3.1. Synthesis and characterization
Probe 2 can be easily prepared and purified according to reported
method (Scheme 2) [54]. The chemical structures of probe 2 and in-
termediate compounds were confirmed by standard spectroscopy
methods with satisfactory results. Details of synthesis and character-
ization can be found in Figs. S4–S8 in the supplementary materials.
3.2. The AIE behavior of probe 2
The AIE properties of probe 2 was confirmed in ethanol/water
mixtures with different water volume fractions (fw). Results from Fig. S1
in the supplementary materials showed that the emission of probe 2
was very weak in ethanol and increased slowly until fw reached 70%.
Then the emission intensified swiftly, especially when fw was beyond
80%. As water is a poor solvent for probe 2, the addition of water will
induce the formation of probe 2 aggregates, and thus turned on the
emission. As a result, probe 2 features the unique AIE characteristics.
Moreover, the behavior of probe 2 in high concentration solutions also
confirmed its AIE feature. As depicted in Fig. S2, the emission intensity
of probe 2 in pure water gradually enhanced as its concentration in-
creased. Again, with water as a poor solvent for probe 2, the con-
centration increase will induce the formation of more and more ag-
gregates, which blocked the non-radiative decay pathway, and turned
on the emission, similar to those of reported TPE derivatives [30–34].
2.2.2. Compound 2
Compound 2-d (0.30 g, 0.80 mmol) and 2-(aminooxy)acetic acid
(0.115 g, 1.26 mmol) was added to 30 mL redistilled 1,4-dioxane in
order. The reaction mixture was refluxed for 2.5 h. After cooling to
room temperature, the mixture was washed with brine and extracted
with ethyl acetate twice. The organic layer was combined and dried
over anhydrous Na2SO4, filtered and evaporated. The residue was
subjected to column chromatography with ethyl acetate/petroleum
ether (1/20–1/2, v/v) as eluent. Compound 2 was obtained as a light
yellow solid. Yield: 92%. 1HNMR (300 MHz, CDCl3) δ 8.11 (s, 1H), 7.32
(d, J = 8.3 Hz, 2H), 7.15–7.08 (m, 9H), 7.07–6.98 (m, 8H), 4.73 (s, 2H);
13C NMR (75 MHz, DMSO) δ 174.87, 150.46, 146.02, 143.25, 143.18,
143.09, 141.76, 139.99, 131.55, 131.14, 131.10, 129.05, 127.66,
127.59, 127.50, 126.60, 126.45, 77.05. HRMS m/z calculated for
3.3. The spectra response of probe 2 toward Hg2+
To validate our initial design concept for switch on detection of
Hg2+, the spectra response of probe 2 toward Hg2+ were first recorded
in ethanol/water mixture (3/7, v/v). As depicted in Fig. 1A, probe 2
was weakly emissive in the absence of Hg2+. While after the addition of
Hg2+, the blue emission was greatly switched on with a peak centered
at 478 nm, due to the Hg2+-promoted aggregation formation. The
emission intensity gradually enhanced with increasing aliquots of
Hg2+. Moreover, a good linearity was found between the emission in-
tensity of probe 2 and the concentration of Hg2+ with a range of
15–45 μM (Fig. 1B). The limit of detection was thus calculated to be
45.4 nM, based on the 3σ/B rule (where σ is the standard deviation of
blank measurements and B is the slop of the linear equation) [54]. The
detection mechanism was proposed as shown in Scheme 1. In the ab-
sence of Hg2+, probe 2 can be well dissolved in ethanol/water mixture
C
29H24NO3+: [M+H]+ 434.1751, found 434.1754.
2.3. Determination of the detection limit of probe 2 toward addition of
Hg2+
Based on the linear fitting in Fig. 1B, the detection limit (C) is es-
timated as follows:
C = 3σ/B
Where σ is the standard deviation obtained from three individual
fluorescence measurements (I478 nm) of probe 2 (25 μM) without Hg2+
and B is the slope obtained after linear fitting the titration curves within
certain ranges.
(3/7, v/v), without forming aggregates. While after addition of Hg2+
,
the –CH]N and –OH group can coordinate with Hg2+, resulting in
2
+
Hg2+ complex with poor water solubility. And as a result,
Fig. 1. (A) Fluorescent emission spectra of
probe 2 (25.0 μM in ethanol/water mixture,
3/7, v/v) before and after addition of dif-
ferent
concentrations
of
Hg2+
(0.0–52.0 μM). Inset: fluorescent photo-
graphs of probe 2 before and after addition
of 50.0 μM Hg2+ taken under 365 nm UV
irradiation. (B) The plot and linear fitting of
fluorescence intensity of probe 2 (25.0 μM)
at 478 nm as a function of the concentration
of
Hg2+
.
Excitation
wavelength
(λex = 330 nm).
3

Y. Yuan, et al.
AnalyticalBiochemistry585(2019)113403
Fig. 2. Fluorescence microscope images of probe 2 (25.0 μM) in H2O/EtOH mixture in the absence (A and B) and presence (C and D) of Hg2+ (50.0 μM). Scale bar
represents 20 μm. Excitation was set at 405 nm.
Fig. 3. (A) DLS data of probe 2 before and
after addition of 50.0 μM Hg2+
.
(B)
Fluorescence intensity at 478 nm of probe 2
(black bars) and probe 2 + Hg2+ (red bars)
at different pH value in buffered solution.
λ
ex = 330 nm. (For interpretation of the re-
ferences to colour in this figure legend, the
reader is referred to the Web version of this
article.)
aggregation will occur and turn on the emission. To confirm the pro-
posed detection mechanism, both fluorescence imaging and dynamic
light scattering (DLS) experiments were carried out. As illustrated in
Fig. 2, the solution of probe 2 exhibited negligible emission before the
addition of Hg2+. However, in the presence of Hg2+, light blue emis-
sive dots can be clearly observed in the fluorescence imaging. DLS data
also indicated the formation of 20–200 nm aggregates for the mixed
solution of probe 2 and Hg2+ (Fig. 3A). To ascertain the actual binding
stoichiometry of the probe 2-Hg2+ conjugate, a Job's plot analysis was
conducted. As shown in Fig. S3, the emission intensity changes at
478 nm versus the mole fraction of Hg2+ was measured. The maximum
emission intensity change was observed at a mole fraction of about
0.33, which supported a 2:1 complex formed between probe 2 and
Hg2+. According to these result, the detection mechanism was pro-
posed as shown in Scheme 1.
Hg2+ was also evaluated, as the pH values in different samples to be
tested may vary drastically. As shown in Fig. 3B, the fluorescence in-
tensity of probe 2 is stable within a wide pH range from 1.0 to 13.0.
However, the response of probe 2 toward Hg2+ showed the highest
sensitivity in pH 3.0–9.0. More acidic or alkaline media would result in
poor fluorescence response, probably due to the poor coordination
ability of probe 2 with Hg2+ in strong acidic conditions, or the for-
mation of Hg(OH)2 at basic pHs [41].
3.5. Selectivity
To check the specificity of probe 2 toward Hg2+, we then evaluated
the responses of probe 2 toward common metal ions in parallel under
the same conditions. As exhibited in Fig. 4, the addition of Hg2+ in-
duced a prominent enhancement of the PL intensity, while other metal
ions including Ag+, Au3+, Ba2+, Ca2+, Cd2+, Co2+, Cr3+, Cu2+, Fe2+
,
3.4. pH effect
Fe3+, K+, Li+, Mg2+, Mn2+, Na+, Ni2+, Pd2+, Pt2+, Rh3+, Zn2+, Zr4+
caused no changes, except for Pb2+, which lead to a small emission
enhancement. The high sensitivity of probe 2 toward Hg2+ might be
The influence of pH on the properties of probe 2 and its response to
4

Y. Yuan, et al.
AnalyticalBiochemistry585(2019)113403
Fig. 4. (A) Fluorescent photographs of
probe 2 (25.0 μM, H2O/EtOH = 7/3) before
and after addition of various common metal
ions taken under 365 nm UV irradiation. (B)
The fluorescence spectra of probe 2 in the
presence of various common metal ions. (C)
The fluorescence intensity changes of probe
2 at 478 nm in the presence of various
common metal ions. a: blank; b: Ag+; c:
Au3+; d: Ba2+; e: Ca2+; f: Cd2+; g: Co2+; h:
Cr3+; i: Cu2+; j: Fe2+; k: Fe3+; l: Hg2+; m:
K+; n: Li+; o: Mg2+; p: Mn2+; q: Na+; r:
Ni2+; s: Pb2+; t: Pd2+; u: Pt2+; v: Rh3+; w:
Zn2+; x: Zr4+. The concentration of Hg2+
and Pb2+ is 50.0 μM, while concentrations
of other metal ions are 100 μM,
λ
ex = 330 nm.
4. Conclusion
Table 1
Detection of Hg2+ in tap water.
We have successfully established a switch on and reversible fluor-
escent probe for the sensitive detection of Hg2+ in aqueous solution
based on the unique AIE behaviour of a tetraphenylethylene derivative
(probe 2). Probe 2 exhibited high sensitivity and good selectivity to-
ward Hg2+ with a detection limit of 45.4 nM. The reversibility of probe
2 toward Hg2+ detection may also extend the application of probe 2 to
the removal of toxic Hg2+ from tap water or environmental samples.
Method
ICP-MS
Probe 2
Added (μM)
Detected (μM)
Recovery (%)
RSD (%)
0
Not detected
30.17
Not detected
30.93
/
/
2.6
/
30.00
0
30.00
100.6
/
103.1
1.1
due to the fact that mercury ion has a higher binding affinity and faster
chelating kinetics with N and O functional groups in probe 2 than Pb2+
and other metal ions [27]. These results demonstrated a good se-
Acknowledgments
lectivity of probe 2 toward Hg2+
.
This work was supported by China Agriculture Research System
(CARS-23-B16), The National Key R&D Program of China
(2016YFD0801006), National Natural Science Foundation of China
(21663005 and 21871060), and the Natural Science Foundation of
Jiangxi Province (2018ACB21009, 20181BAB213007).
3.6. Analysis of Hg2+ in real sample
The fluorescent probe 2 has been validated for practical application
in the determination of Hg2+ ion content in tap water. Control ex-
periments show that no Hg2+ was detected in tap water. When Hg2+
was added, fluorescence spectra were recorded and the contents of
Hg2+ ions were recovered using the linear equation obtained from Fig.
S4. Table 1 presents the results and good recoveries were obtained. In
order to demonstrate the accuracy of this method, the results were
compared to those obtained by ICP-MS. As shown in Table 1, results
obtained by probe 2 agrees well with those obtained by ICP-MS, in-
dicating that the proposed method can be used to analyze Hg2+ accu-
rately.
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://
doi.org/10.1016/j.ab.2019.113403.
References
[1] E.M. Nolan, S.J. Lippard, Tools and tactics for the optical detection of mercuric ion,
Chem. Rev. 108 (9) (2008) 3443–3480.
[2] M. McNutt, Taming a mercurial element, Science 341 (6153) (2013) 1442–1443.
[3] J. Qiu, Tough talk over mercury treaty, Nature 493 (2013) 144–145.
[4] F. Wang, S.W. Nam, Z. Guo, S. Park, J. Yoon, A new rhodamine derivative bearing
benzothiazole and thiocarbonyl moieties as a highly selective fluorescent and col-
orimetric chemodosimeter for Hg2+, Sens. Actuators B Chem. 161 (1) (2012)
948–953.
3.7. Reversibility
[5] B. Weiss, Why methylmercury remains a conundrum 50 years after minamata,
Toxicol. Sci. 97 (2) (2007) 223–225.
[6] Mercury Update: Impact on Fish Advisories, EPA, Office of Water, Washington, DC,
2001, pp. 1–10 EPA Fact Sheet EPA-823-F-01-011.
[7] M. Wang, W. Feng, J. Shi, F. Zhang, B. Wang, M. Zhu, B. Li, Y. Zhu, Z. Chai,
Development of a mild mercaptoethanol extraction method for determination of
mercury species in biological samples by HPLC–ICP-MS, Talanta 71 (5) (2007)
2034–2039.
[8] N. Demuth, K.G. Heumann, Validation of methylmercury determinations in aquatic
systems by alkyl derivatization methods for GC analysis using ICP-IDMS, Anal.
Chem. 73 (16) (2001) 4020–4027.
The reversibility of the detection process was further investigated by
the addition of S2- to the probe 2 + Hg2+ complex. Owing to the much
stronger binding affinity of Hg2+ to S2-, S2−can deplete Hg2+ from
probe 2 + Hg2+ complex, releasing free probe 2, which recovers its
weak emission (Fig. S5 in supplementary information). The reversibility
of probe 2 toward Hg2+ detection may expand the application of probe
2 to the removal of toxic Hg2+ from environmental samples.
[9] I. Narin, M. Soylak, L. Elci, M. Doğan, Determination of trace metal ions by AAS in
5

Y. Yuan, et al.
AnalyticalBiochemistry585(2019)113403
natural water samples after preconcentration of pyrocatechol violet complexes on
derivative, Chem. Commun. 53 (32) (2017) 4505–4508.
an activated carbon column, Talanta 52 (6) (2000) 1041–1046.
[10] H. Zheng, B. Jia, Z. Zhu, Z. Tang, S. Hu, Determination of trace amounts of Pb, Cd,
Ni and Co by wavelength-dispersive X-ray fluorescence spectrometry after pre-
concentration with dithizone functionalized graphene, Anal. Methods 6 (21) (2014)
8569–8576.
[35] Z. Ruan, Y. Shan, Y. Gong, C. Wang, F. Ye, Y. Qiu, Z. Liang, Z. Li, Novel AIE-active
ratiometric fluorescent probes for mercury(II) based on the Hg2+-promoted de-
protection of thioketal, and good mechanochromic properties, J. Mater. Chem. C 6
(4) (2018) 773–780.
[36] X. Ou, X. Lou, F. Xia, A highly sensitive DNA-AIEgen-based “turn-on” fluorescence
chemosensor for amplification analysis of Hg2+ ions in real samples and living cells,
Sci. China Chem. 60 (5) (2017) 663–669.
[11] E. Witkowaska, K. Szczepaniak, M. Biziuk, Some applications of neutron activation
analysis, J. Radioanal. Nucl. Chem. 265 (1) (2005) 141–150.
[12] B. Dong, X. Song, X. Kong, C. Wang, N. Zhang, W. Lin, Two-photon red-emissive
fluorescent probe for imaging nitroxyl (HNO) in living cells and tissues, J. Mater.
Chem. B 5 (26) (2017) 5218–5224.
[37] Y. Chen, W. Zhang, Y. Cai, R.T.K. Kwok, Y. Hu, J.W.Y. Lam, X. Gu, Z. He, Z. Zhao,
X. Zheng, B. Chen, C. Gui, B.Z. Tang, AIEgens for dark through-bond energy
transfer: design, synthesis, theoretical study and application in ratiometric Hg2+
sensing, Chem. Sci. 8 (3) (2017) 2047–2055.
[38] A. Chatterjee, M. Banerjee, D.G. Khandare, R.U. Gawas, S.C. Mascarenhas,
A. Ganguly, R. Gupta, H. Joshi, Aggregation-induced emission-based chemodosi-
meter approach for selective sensing and imaging of Hg(II) and methylmercury
species, Anal. Chem. 89 (23) (2017) 12698–12704.
[39] X. Wen, Z. Fan, A novel ‘turn-on’ fluorescence probe with aggregation-induced
emission for the selective detection and bioimaging of Hg2+ in live cells, Sens.
Actuators B Chem. 247 (2017) 655–663.
[40] L. Liu, G. Zhang, J. Xiang, D. Zhang, D. Zhu, Fluorescence “Turn on” chemosensors
for Ag+ and Hg2+ based on tetraphenylethylene motif featuring adenine and thy-
mine moieties, Org. Lett. 10 (20) (2008) 4581–4584.
[41] L.N. Neupane, E.-T. Oh, H.J. Park, K.-H. Lee, Selective and sensitive detection of
heavy metal ions in 100% aqueous solution and cells with a fluorescence chemo-
sensor based on peptide using aggregation-induced emission, Anal. Chem. 88 (6)
(2016) 3333–3340.
[42] N. Zhao, J.W.Y. Lam, H.H.Y. Sung, H.M. Su, I.D. Williams, K.S. Wong, B.Z. Tang,
Effect of the counterion on light emission: a displacement strategy to change the
emission behaviour from aggregation-caused quenching to aggregation-induced
emission and to construct sensitive fluorescent sensors for Hg2+ detection, Chem.
Eur J. 20 (1) (2014) 133–138.
[13] K. Hanaoka, K. Kikuchi, S. Kobayashi, T. Nagano, Time-resolved long-lived lumi-
nescence imaging method employing luminescent lanthanide probes with a new
microscopy system, J. Am. Chem. Soc. 129 (44) (2007) 13502–13509.
[14] S. Gan, J. Zhou, T.A. Smith, H. Su, W. Luo, Y. Hong, Z. Zhao, B.Z. Tang, New
AIEgens with delayed fluorescence for fluorescence imaging and fluorescence life-
time imaging of living cells, Mater. Chem. Front. 1 (12) (2017) 2554–2558.
[15] D. Wu, A.C. Sedgwick, T. Gunnlaugsson, E.U. Akkaya, J. Yoon, T.D. James,
Fluorescent chemosensors: the past, present and future, Chem. Soc. Rev. 46 (23)
(2017) 7105–7123.
[16] Y. Fang, W. Shi, Y. Hu, X. Li, H. Ma, A dual-function fluorescent probe for mon-
itoring the degrees of hypoxia in living cells via the imaging of nitroreductase and
adenosine triphosphate, Chem. Commun. 54 (43) (2018) 5454–5457.
[17] X. Hou, J. Peng, F. Zeng, C. Yu, S. Wu, An anthracenecarboximide fluorescent probe
for in vitro and in vivo ratiometric imaging of endogenous alpha-L-fucosidase for
hepatocellular carcinoma diagnosis, Mater. Chem. Front. 1 (4) (2017) 660–667.
[18] C.-J. Zhang, X. Cai, S. Xu, R. Zhan, W. Jien, B. Liu, A light-up endoplasmic reticulum
probe based on a rational design of red-emissive fluorogens with aggregation-in-
duced emission, Chem. Commun. 53 (78) (2017) 10792–10795.
[19] H. Xu, Q. Li, L. Wang, Y. He, J. Shi, B. Tang, C. Fan, Nanoscale optical probes for
cellular imaging, Chem. Soc. Rev. 43 (8) (2014) 2650–2661.
[20] P. Verwilst, H.S. Kim, S. Kim, C. Kang, J.S. Kim, Shedding light on tau protein
aggregation: the progress in developing highly selective fluorophores, Chem. Soc.
Rev. 47 (7) (2018) 2249–2265.
[43] H. Zhou, J. Mei, Y.-A. Chen, C.-L. Chen, W. Chen, Z. Zhang, J. Su, P.-T. Chou,
H. Tian, Phenazine-based ratiometric Hg2+ probes with well-resolved dual emis-
sions: a new sensing mechanism by vibration-induced emission (VIE), Small 12 (47)
(2016) 6542–6546.
[44] Y. Jiang, Y. Chen, M. Alrashdi, W. Luo, B.Z. Tang, J. Zhang, J. Qin, Y. Tang,
Monitoring and quantification of the complex bioaccumulation process of mercury
ion in algae by a novel aggregation-induced emission fluorogen, RSC Adv. 6 (102)
(2016) 100318–100325.
[45] R. Zhang, P. Li, W. Zhang, N. Li, N. Zhao, A highly sensitive fluorescent sensor with
aggregation-induced emission characteristics for the detection of iodide and mer-
cury ions in aqueous solution, J. Mater. Chem. C 4 (44) (2016) 10479–10485.
[46] G. Huang, G. Zhang, D. Zhang, Turn-on of the fluorescence of tetra(4-pyr-
idylphenyl)ethylene by the synergistic interactions of mercury(II) cation and hy-
drogen sulfate anion, Chem. Commun. 48 (60) (2012) 7504–7506.
[47] W. Fang, G. Zhang, J. Chen, L. Kong, L. Yang, H. Bi, J. Yang, An AIE active probe for
specific sensing of Hg2+ based on linear conjugated bis-Schiff base, Sens. Actuators
B Chem. 229 (2016) 338–346.
[21] S. Uno, M. Kamiya, A. Morozumi, Y. Urano, A green-light-emitting, spontaneously
blinking fluorophore based on intramolecular spirocyclization for dual-colour
super-resolution imaging, Chem. Commun. 54 (1) (2018) 102–105.
[22] G. Chen, Z. Guo, G. Zeng, L. Tang, Switching specific biomolecular interactions on
surfaces under complex biological conditions, Analyst 140 (21) (2015) 5400–5443.
[23] N. Kumar, V. Bhalla, M. Kumar, Resonance energy transfer-based fluorescent probes
for Hg2+, Cu2+ and Fe2+/Fe3+ ions, Analyst 139 (3) (2014) 543–558.
[24] J. Du, M. Hu, J. Fan, X. Peng, Fluorescent chemodosimeters using “mild” chemical
events for the detection of small anions and cations in biological and environmental
media, Chem. Soc. Rev. 41 (12) (2012) 4511–4535.
[25] H.N. Kim, W.X. Ren, J.S. Kim, J. Yoon, Fluorescent and colorimetric sensors for
detection of lead, cadmium, and mercury ions, Chem. Soc. Rev. 41 (8) (2012)
3210–3244.
[26] A. Badiei, B.V. Razavi, H. Goldooz, G.M. Ziarani, F. Faridbod, M.R. Ganjali, A novel
fluorescent chemosensor assembled with 2,6-bis(2-benzimidazolyl)pyridine-func-
tionalized nanoporous silica-type SBA-15 for recognition of Hg2+ ion in aqueous
media, Int. J. Environ. Res. 12 (1) (2018) 109–115.
[27] G. Shiravand, A. Badiei, G.M. Ziarani, Carboxyl-rich g-C3N4 nanoparticles: synth-
esis, characterization and their application for selective fluorescence sensing of
Hg2+ and Fe3+ in aqueous media, Sens. Actuators B Chem. 242 (2017) 244–254.
[28] D. Ding, K. Li, B. Liu, B.Z. Tang, Bioprobes based on AIE fluorogens, Acc. Chem. Res.
46 (11) (2013) 2441–2453.
[29] Y. Zhao, R.T.K. Kowk, J.W.Y. Lam, B.Z. Tang, A highly fluorescent AIE-active
theranostic agent with anti-tumor activity to specific cancer cells, Nanoscale 8 (25)
(2016) 12520–12523.
[48] K. Ma, X. Li, B. Xu, W. Tian, A sensitive and selective “turn-on” fluorescent probe for
Hg2+ based on thymine-Hg2+-thymine complex with an aggregation-induced
emission feature, Anal. Methods 6 (7) (2014) 2338–2342.
[49] M.T. Gabr, F.C. Pigge, A turn-on AIE active fluorescent sensor for Hg2+ by com-
bination of 1,1-bis(2-pyridyl)ethylene and thiophene/bithiophene fragments,
Mater. Chem. Front. 1 (8) (2017) 1654–1661.
[50] Q. Lin, X.-M. Jiang, X.-Q. Ma, J. Liu, H. Yao, Y.-M. Zhang, T.-B. Wei, Novel bispillar
[5]arene-based AIEgen and its' application in mercury(II) detection, Sens. Actuators
B Chem. 272 (2018) 139–145.
[51] M. Shyamal, S. Maity, A. Maity, R. Maity, S. Roy, A. Misra, Aggregation induced
emission based “turn-off” fluorescent chemosensor for selective and swift sensing of
mercury (II) ions in water, Sens. Actuators B Chem. 263 (2018) 347–359.
[52] Y. Li, Y. Liu, H. Zhou, W. Chen, J. Mei, J. Su, Ratiometric Hg2+/Ag+ probes with
orange red-white-blue fluorescence response constructed by integrating vibration-
induced emission with an aggregation-induced emission motif, Chem. Eur J. 23 (39)
(2017) 9280–9287.
[30] Z. He, C. Ke, B.Z. Tang, Journey of aggregation-induced emission research, ACS
Omega 3 (3) (2018) 3267–3277.
[31] J. Mei, N.L.C. Leung, R.T.K. Kwok, J.W.K. Lam, B.Z. Tang, Aggregation-induced
emission: together we shine, united we soar!, Chem. Rev. 115 (21) (2015)
11718–11940.
[32] M. Gao, B.Z. Tang, Fluorescent sensors based on aggregation-induced emission:
recent advances and perspectives, ACS Sens. 2 (10) (2017) 1382–1399.
[33] J. Shi, Y. Li, Q. Li, Z. Li, Enzyme-responsive bioprobes based on the mechanism of
aggregation-induced emission, ACS Appl. Mater. Interfaces 10 (15) (2018)
12278–12294.
[34] G. Jiang, G. Zeng, W. Zhu, Y. Li, X. Dong, G. Zhang, X. Fan, J. Wang, Y. Wu,
B.Z. Tang, A selective and light-up fluorescent probe for β-galactosidase activity
detection and imaging in living cells based on an AIE tetraphenylethylene
[53] H.-B. Cheng, Z. Li, Y.-D. Huang, L. Liu, H.-C. Wu, Pillararene-based aggregation-
induced-emission-active supramolecular system for simultaneous detection and
removal of mercury(II) in water, ACS Appl. Mater. Interfaces 9 (13) (2017)
11889–11894.
[54] G. Jiang, J. Wang, Y. Yang, G. Zhang, Y. Liu, H. Lin, G. Zhang, Y. Li, X. Fan,
Fluorescent turn-on sensing of bacterial lipopolysaccharide in artificial urine
sample with sensitivity down to nanomolar by tetraphenylethylene based ag-
gregation induced emission molecule, Biosens. Bioelectron. 85 (2016) 62–67.
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