A dual-excitation fluorescent probe EuIII-dtpa-bis(HBT) for hydrazine detection in aqueous solutions and living cells

Article abstract of DOI:10.1039/c9nj03972d

Based on the esterification of 2-(2-hydroxyphenyl)benzothiazole (HBT) and a rare-earth metal ion complex Eu^III-dtpa, a novel dual-excitation fluorescence probe, Eu^III-dtpa-bis(HBT), was developed for the detection of hydrazine (N₂H₄). The structure of dtpa-bis(HBT) was characterized via FT-IR and NMR, and its optical properties were studied via UV-vis absorption and fluorescence spectroscopy. Influencing factors including solution acidity, interfering substances and N₂H₄ concentrations were considered for the detection of N₂H₄ using Eu^III-dtpa-bis(HBT). Eu^III-dtpa-bis(N₂H₄) and HBT emit significant fluorescence at 470 nm (λ_ex = 270 nm) and 480 nm (λ_ex = 325 nm), respectively. The detection limit of Eu^III-dtpa-bis(HBT) with N₂H₄ was 0.283 μM (14 ppb) and 0.182 μM (9 ppb) upon excitation at 270 nm and 325 nm, which is close to and lower than the EPA standard (10 ppb), respectively. The mechanism for the detection of N₂H₄ by Eu^III-dtpa-bis(HBT) was deduced from the experimental results and theoretical calculations. Also, cytotoxicity and cell imaging experiments of Eu^III-dtpa-bis(HBT) were performed. The experimental results showed that the fluorescent probe Eu^III-dtpa-bis(HBT) can be applied to detect N₂H₄ in aqueous solution and living cells.

Full text of DOI:10.1039/c9nj03972d

NJC
View Article Online
View Journal | View Issue
PAPER
A dual-excitation fluorescent probe
EuIII-dtpa-bis(HBT) for hydrazine detection
in aqueous solutions and living cells
Cite this: New J. Chem., 2019,
43, 16478
Wenfang Liu,ab Bingqiang Wang,d Haishuang Jia,a Jun Wang *a and
Youtao Song*c
Based on the esterification of 2-(2-hydroxyphenyl)benzothiazole (HBT) and a rare-earth metal ion complex
EuIII-dtpa, a novel dual-excitation fluorescence probe, EuIII-dtpa-bis(HBT), was developed for the detection of
hydrazine (N2H4). The structure of dtpa-bis(HBT) was characterized via FT-IR and NMR, and its optical properties
were studied via UV-vis absorption and fluorescence spectroscopy. Influencing factors including solution acidity,
interfering substances and N2H4 concentrations were considered for the detection of N2H4 using EuIII-dtpa-
bis(HBT). EuIII-dtpa-bis(N2H4) and HBT emit significant fluorescence at 470 nm (lex = 270 nm) and
480 nm (lex = 325 nm), respectively. The detection limit of EuIII-dtpa-bis(HBT) with N2H4 was 0.283 mM
(14 ppb) and 0.182 mM (9 ppb) upon excitation at 270 nm and 325 nm, which is close to and lower than
the EPA standard (10 ppb), respectively. The mechanism for the detection of N2H4 by EuIII-dtpa-bis(HBT)
was deduced from the experimental results and theoretical calculations. Also, cytotoxicity and cell imaging
experiments of EuIII-dtpa-bis(HBT) were performed. The experimental results showed that the fluorescent
probe EuIII-dtpa-bis(HBT) can be applied to detect N2H4 in aqueous solution and living cells.
Received 31st July 2019,
Accepted 26th September 2019
DOI: 10.1039/c9nj03972d
rsc.li/njc
spectrophotometry7,8 and electrochemical analysis.9–16 Although
these methods can be used effectively and accurately to detect
Introduction
Hydrazine (N2H4) is a colorless oily liquid and has a pungent N2H4, they often need special equipment, complex sample
odor, which is similar to that of ammonia. It is widely used in processing and handling and are time-consuming. Therefore,
catalysts, pharmaceutical intermediates, emulsifiers, dyes and the development of convenient, rapid and economical N2H4
agriculture.1 In addition, N2H4 is often used as a high-energy detection methods is still required. Recently, detection methods
propellant for missiles, rockets and satellites due to its high based on fluorescence technology have aroused extensive attention
energy density.2 However, N2H4 is also a potentially carcinogenic owing to its high selectivity, operation simplicity and real-time
toxin. The kidneys, liver, lungs and central nervous system are analysis. N2H4 is usually detected using some fluorescent probes
severely damaged when N2H4 is inhaled via the skin, mouth and containing dicyano,17,18 phthalaldehyde,19,20 aldehyde21 and
nose. Obviously, if N2H4 is mishandled during its manufacture, aliphatic groups.22–26 N2H4 can also be detected through the
use, and transportation, it will not only threaten human health, Gabriel reaction27–31 and hydrazinolysis.32–35 However, when
but also cause serious pollution to the environment. Therefore, it these probes are used to detect N2H4, only a single excitation
is of great significance to establish convenient and effective wavelength can be used to give the responses, which is easily
methods for the detection of N2H4 to control environmental disturbed by some external factors. Therefore, more precise
pollution and ensure human health.
fluorescence probes need to be developed to overcome the
In general, the traditional methods for detecting N2H4 disadvantages of a single excitation wavelength.
include titration,3 chemiluminescence,4,5 liquid chromatography,6
As is known, aminopolycarboxylic acids as chelating agents
can coordinate with rare-earth metal ions, forming fluorescent
probes.36–38 In general, most of the rare-earth metal ions can
form nine-coordination compounds with aminopolycarboxylic
acid ligands.39,40 However, dtpa, as an octadentate ligand, can
only provide eight coordination atoms to combine with rare
earth metal ions. A water molecule as a ninth ligand together
with dtpa can coordinate with rare earth metal ions, forming
nine-coordinate complexes. Rare earth metal ions are widely
a College of Chemistry, Liaoning University, Shenyang, Liaoning Province, 110036,
China. E-mail: wangjun888tg@126.com, wangjun891@sina.com
b Department of Chemistry, Baotou Teachers’ College, Baotou, Inner Mongolia,
014030, China
c College of Environment, Liaoning University, Shenyang, Liaoning Province,
110036, China. E-mail: ysong_tg@126.com
d School of Chemistry and Material Science, Shanxi Normal University, Linfen,
Shanxi Province, 041000, China
16478 | New J. Chem., 2019, 43, 16478--16489 This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2019

View Article Online
Paper
NJC
used in many fields owing to their unique optical properties, calculated via the DFT method. The experimental results indicate
such as large Stokes displacement, long fluorescence life and that the fluorescent probe EuIII-dtpa-bis(HBT) can be applied to
stable optical properties.41,42 In addition, in a previous study, a detect N2H4 in aqueous solutions and living cells.
new rare earth metal ion complex-derived dual-excitation
fluorescence probe, Tb3+-dtpa-bis(fluorescein), was obtained.
The formation and fracture of the ester bonds of Tb3+-dtpa with
Experimental
Reagents and instruments
fluorescein led to the fluorescence response changes of Tb3+
-
dtpa-bis(fluorescein), realizing the dual-excitation detection of
N2H4.43 Based on this, it can be expected that 2-(2-hydroxy-
benzene)benzothiazole (HBT) can also be utilized for designing
novel dual-excitation fluorescence probes based on the hydra-
zinolysis mechanism. Because HBT is easily excited by light, its
photoisomerization from the enol form to the keto form occurs
by ESIPT, and thus its fluorescence wavelength obviously
increases, which results in a large Stokes shift. Therefore,
2-(2-hydroxybenzene)benzothiazole (HBT) is often applied as
the fluorescence group in fluorescence probes owing to its
stable optical performance, large Stokes shift, high absorption
coefficient and high fluorescence quantum yield.44–46 In this work,
based on the combination of HBT and the EuIII-dtpa complex,
a novel dual-excitation fluorescence probe with two signals,
EuIII-dtpa-bis(HBT), was designed and developed (Scheme 1).
Firstly, dtpa-bis(HBT) was synthesized through the esterifi-
cation of dtpa and HBT, and then Eu(NO3)3 solution was added
to the dtpa-bis(HBT), forming EuIII-dtpa-bis(HBT), and the
formed ester bonds can act as recognition sites for N2H4. After
adding N2H4 to EuIII-dtpa-bis(HBT), the ester bonds were
destroyed, forming EuIII-dtpa-bis(N2H4) and HBT, which are
both fluorescent compounds. EuIII-dtpa-bis(N2H4) and HBT
displayed significant fluorescence at 470 nm (lex = 270 nm)
and 480 nm (lex = 325 nm), respectively. The fluorescence
intensities of EuIII-dtpa-bis(HBT) is closely related to the
concentration of N2H4. EuIII-dtpa-bis(HBT) was used to detect
N2H4 with a low LOD (0.283 mM and 0.182 mM). The frontier
molecular orbital energies of dtpa-bis(HBT) and HBT were
All reagents were obtained from commercial sources (analytical
purity, Shanghai Aladdin Biochemical Technology, China). The
water used in the experiments was ultra-pure (18.3 MO cm). The
actual water samples came from reservoirs, tap water and
drinking water. Fourier transform infrared (FT-IR) spectra were
obtained on an IRAffinity-1, Japan. 1H NMR and 13C NMR spectra
were measured on a Bruker AVANCE NEO with DMSO-d6 as the
solvent and TMS as the internal standard. UV-vis absorption
spectra were measured on a Cary 50, Varian, USA. Fluorescence
spectra were measured on a Cary 300, Varian, USA. All fluorescence
imaging experiments were performed on a BIO-RADiMark,
ShangHai.
Synthesis of EuIII-dtpa-bis(HBT)
Diethylenetriamine pentaacetic acid dianhydride (dtpaa).
The synthesis of dtpaa was carried out in the absence of water
through the improvement of previous methods.47–49 The procedure
is described in Scheme 1. Briefly, 7.8015 g dtpa (20.00 mmol) was
dissolved in a round-bottom flask with acetic anhydride (8.0 mL,
80.00 mol) and pyridine (10.0 mL, 0.12 mol), which was heated and
stirred for 24 h at 65 1C. After the solution cooled to room
temperature, the residual solvent was removed using a rotary
evaporator. The product was obtained by vacuum filtration and
washing with acetyl oxide and anhydrous diethyl ether, respectively,
and then dried in under vacuum (6.3758 g, 81%). All experiments
were performed at room temperature (25.00 Æ 0.02 1C). FT-IR
(KBr, cmÀ1) of dtpaa: 1642.41, 1772.10, 1821.08, 2341.42, 2820.47
1
and 2979.80. H-NMR (ppm, 400 MHz, DMSO, d) of dtpa: 2.45
(t, 8H), 3.30 (s, 10H) and 11.01 (s, 3H). 1H-NMR (ppm, 400 MHz,
DMSO, d) of dtpaa: 2.59 (t, 4H), 2.74 (t, 4H), 3.30 (s, 2H), 3.70
(s, 8H) and 11.01 (s, 1H).
Synthesis of dtpa-bis(HBT)
dtpa-bis(HBT) was synthesized through the improvement of the
previous synthesis methods.43,50,51 In the absence of water,
1.9678 g dtpaa (5.56 mmol) was dissolved in DMF (20.0 mL)
and TEA (2.33 mL), respectively, and stirred constantly until
colorless at 50 1C. Next, 2.4981 g HBT dissolved in DMF (20.0 mL)
was added to the above solution of dtpaa dropwise. Finally,
the mixture was heated for 24 h at 100 1C and then was left to
stand overnight. The residual solvent was removed using a rotary
evaporator. The product was obtained by vacuum filtration and
washing with ice-water and anhydrous diethyl ether, respectively,
and then dried under vacuum (3.2574 g, 73%). All experiments are
were performed at room temperature (25.00 Æ 0.02 1C). FT-IR
(KBr, cmÀ1): 851, 1150, 1253, 1401, 1623, 1794, 3008, 3301. 1H NMR
(ppm, 400 MHz, DMSO, d): 11.64 (s, 9H), 8.30–8.23 (m, 5H), 8.15
(dd, J = 13.8, 7.9 Hz, 2H), 8.06 (d, J = 8.1 Hz, 2H), 8.00–7.82 (m, 16H),
Scheme 1 Synthetic route for EuIII-dtpa-bis(HBT) complex.
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2019 New J. Chem., 2019, 43, 16478--16489 | 16479

View Article Online
NJC
Paper
7.51–7.35 (m, 3H), 7.35–7.17 (m, 2H), 7.08 (t, J = 12.2 Hz, 2H).
13C NMR (ppm, 100 MHz, DMSO, d): 165.75 (s), 134.67 (s),
132.95 (s), 129.00 (s), 126.94 (s), 125.57 (s), 122.52 (d, J = 12.2 Hz),
120.23 (s), 118.76 (s), 117.45 (s), 40.50 (d, J = 20.9 Hz).
Preparation of EuIII-dtpa-bis(HBT)
0.1010 g dtpa-bis(HBT) (0.125 mmol) and 0.0558 g Eu(NO3)3Á6H2O
(0.125 mmol) were dissolved in 60 mL buffer solution (pH = 7.50),
and stirred for 3.0 h at 100 1C. Then the mixture was cooled to
room temperature. The obtained EuIII-dtpa-bis(HBT) solution
was transferred to a 250 mL volumetric flask and was diluted
with buffer solution. The 0.5 mM EuIII-dtpa-bis(HBT) solution
was stored in a cool, dry place. All experiments were performed
at room temperature (25.00 Æ 0.02 1C).
Preparation of real samples
In this experiment, the actual water samples came from reservoir
exit water, reservoir middle water, tap water and drinking water
as research objects. Deionized water was used as the control
group. Firstly, sixteen 50 mL volumetric flasks were divided into
three groups of five. 5.00 mL EuIII-dtpa-bis(HBT) (0.5 mM)
reserve solution was added to each of the above volumetric
flasks. Then the reserve solution of N2H4 in different concentra-
tions was also added to the above three groups of volumetric
flasks. These solutions were calibrated with four real water
samples and deionized water to 50 mL. All the experiments were
performed at room temperature (25.00 Æ 0.02 1C).
Cytotoxicity assay
Initially, BV2 cells were inoculated in 24-well plates, and then
the cells were grown in an incubator (37 1C, 5% CO2 and 95%
air) containing EuIII-dtpa-bis(HBT) with concentrations ranging
from 0– 100 mM for 24 h. Then, 15 mL MTT was added to each
well and further cultured for 4.0 h.52–54 Finally, the BV2 cells in
the 24-well plates were treated with DMSO, and then the culture
plates were stirred for 10 min. Cell survival was observed with a
LEICA DMI8 fluorescence microscope.
Fluorescence microscopy
BV2 cells were cultivated under the above conditions. The cell
images were recorded under a confocal laser scanning micro-
scope in the blue channel. One group of cells was treated with
30 mM EuIII-dtpa-bis(HBT) solution for 3.0 h and the other
group was treated with 30 mM EuIII-dtpa-bis(HBT) + N2H4
solution for 3.0 h. Before the fluorescence imaging, the cells
were washed twice with PBS buffer (pH = 7.2). A fluorescence
microscope (Leica DMI8) was used to detect the results.
Fig. 1 Infrared spectra of dtpa (a), HBT (b), dtpa-bis(HBT) (c) and dtpa-
bis(N2H4) (d).
Results and discussion
1
FT-IR, H and 13C-NMR of dtpa-bis(HBT)
The FT-IR spectra of dtpa, HBT, dtpa-bis(HBT) and dtpa-bis(N2H4) (1752 cmÀ1) (Fig. 1(a)). This is because the formation of the
were examined. As shown in Fig. 1(c), the stretching vibra- ester bond provides an electron donor group for the CQO
tion peak of CQO in dtpa-bis(HBT) was located at 1749 cmÀ1
,
bond, causing the CQO vibration peak to shift to a shorter
which displays a slight blue-shift compared with that of dtpa wavenumber. The asymmetric stretching vibration peak of
16480 | New J. Chem., 2019, 43, 16478--16489 This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2019

View Article Online
Paper
NJC
Fig. 3 UV-vis absorption spectra of HBT, EuIII-dtpa-bis(HBT) and EuIII-
dtpa-bis(HBT) + N2H4 in aqueous solution ([EuIII-dtpa-bis(HBT)] = 50 mM,
[N2H4] = [HBT] = 100 mM, [Tris–HCl/DMSO] = 10 mmol LÀ1, pH = 7.50,
v
(water)/v(DMSO) = 9 : 1 and Tsolu = 25.00 Æ 0.02 1C).
compared with that (3.30 ppm) of the –CH2 near the carboxyl in
dtpa. This is due to the formation of ester bonds between dtpaa and
HBT, causing changes in the chemical displacements. Generally, the
signal peaks at 172.43 ppm belong to the carbon atoms of –COOH in
dtpa.38 As shown in Fig. 2(b), for the synthesized dtpa-bis(HBT),
an obvious signal peak appears at 165.75 ppm, which is assigned
to the carbon atoms of the –CQO in the ester groups. The
appearance of these two characteristic signals (at d = 4.05 ppm in
1H-NMR and at d = 165.75 ppm in 13C-NMR) demonstrates that
dtpa-bis(HBT) was successfully synthesized.
Spectroscopic properties of EuIII-dtpa-bis(HBT)
The UV-vis absorption spectra of HBT, EuIII-dtpa-bis(HBT) and
EuIII-dtpa-bis(HBT) + N2H4 solutions are presented in Fig. 3.
Fig. 2 1H NMR (a) and 13C NMR (b) spectra of dtpa-bis(HBT) in DMSO-d6.
C–O–C in dtpa-bis(HBT) is located at 1254 cmÀ1, corresponding The EuIII-dtpa-bis(HBT) solution at 220 nm has a weak absorp-
to dtpa (1352 cmÀ1) (Fig. 1(a)). Also, the symmetrical stretching tion band. However, after the addition of N2H4, the absorption
vibration peak at 1151 cmÀ1 is ascribed to the C–O–C of dtpa- band of the EuIII-dtpa-bis(HBT) solution was obviously
bis(HBT), corresponding to dtpa (1242 cmÀ1) (Fig. 1(a)). In enhanced. The results show that hydrazinolysis occurred
addition, the stretching vibration peak at 851 cmÀ1 belongs between EuIII-dtpa-bis(HBT) and N2H4, following the formation
to the C–H of the aromatic groups in dtpa-bis(HBT). It displays of HBT and the EuIII-dtpa-bis(N2H4) complex.
a slight red-shift compared with that of HBT (817 cmÀ1
)
The fluorescence spectra of the HBT, EuIII-dtpa-bis(HBT) and
(Fig. 1(b)). Because the hydroxyl in HBT is connected with the EuIII-dtpa-bis(HBT) + N2H4 solutions were determined upon excita-
electron-withdrawing –COO– group, the electrons are deflected, tion at 270 nm and 325 nm. As can be seen in Fig. 4(a), the HBT
making the vibration peak of O–H bond move to a longer solution at 470 nm (lex = 270 nm) has a strong fluorescence emission
wavenumber. The shifts of these characteristic peaks prove peak, but EuIII-dtpa-bis(HBT) only shows a weak fluorescence emis-
that dtpa-bis(HBT) was successfully synthesized by esterifica- sion peak. This is because EuIII-dtpa and HBT are coupled by an
tion between dtpaa and HBT. Furthermore, as shown in ester bond to form EuIII-dtpa-bis(HBT) with weak fluorescence.
Fig. 1(d), the stretching vibration peak at 3419 cmÀ1 is assigned However, after N2H4 was added to the EuIII-dtpa-bis(HBT) solution,
to the N–H in dtpa-bis(N2H4). Also, the stretching vibration the EuIII-dtpa-bis(HBT) + N2H4 solution at 470 nm (lex = 270 nm)
peak at 1660 cmÀ1 is assigned to the CQO of the amide groups displayed a strong fluorescence emission peak, which is due to the
in dtpa-bis(N2H4), which presented a blue-shift compared with fractured ester bonds in EuIII-dtpa-bis(HBT), releasing the HBT with
that of dtpa (1752 cmÀ1) (Fig. 1(a)). This demonstrates that that strong fluorescence. Therefore, EuIII-dtpa-bis(HBT) can be applied to
dtpa-bis(N2H4) was generated through the hydrazinolysis detect N2H4 upon excitation at 270 nm.
between dtpa-bis(HBT) and N2H4.
Analogously, as shown in Fig. 4(b), the EuIII-dtpa-bis(HBT)
The components and structure of dtpa-bis(HBT) were con- solution at 480 nm (lex = 325 nm) also has a weak fluorescence
1
firmed further by 1H and 13C NMR. In the H-NMR in Fig. 2(a), emission peak, and the HBT solution at 480 nm (lex = 325 nm)
the –CH2 protons near the ester groups in dtpa-bis(HBT) has a strong fluorescence emission peak. However, the EuIII-
appeared at d = 4.05 ppm, which displays obvious displacements dtpa-bis(HBT) + N2H4 solution at 480 nm (lex = 325 nm) showed
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2019 New J. Chem., 2019, 43, 16478--16489 | 16481

View Article Online
NJC
Paper
solution (a-1) showed obvious blue fluorescence, but the EuIII-
dtpa-bis(HBT) solution (a-2) did not emit fluorescence.
After N2H4 was added to the EuIII-dtpa-bis(HBT) solution, the
EuIII-dtpa-bis(HBT) + N2H4 solution (a-3) displayed obvious
blue fluorescence. This is because the ester bonds were cleaved
by N2H4, releasing the HBT fluorophore and generating
EuIII-dtpa-bis(N2H4). However, under visible light, the HBT (b-1),
EuIII-dtpa-bis(HBT) (b-2) and EuIII-dtpa-bis(HBT) + N2H4 solutions
(b-3) were colorless. Therefore, based on the phenomena of the
HBT, EuIII-dtpa-bis(HBT) and EuIII-dtpa-bis(HBT) + N2H4 solutions
under ultraviolet-light, EuIII-dtpa-bis(HBT) can detect N2H4 as a
dual-excitation fluorescence probe.
The effect of pH on EuIII-dtpa-bis(HBT) for the detection of
N2H4
The fluorescence responses were studied in EuIII-dtpa-bis(HBT)
solution and EuIII-dtpa-bis(HBT) + N2H4 mixed solution in the
pH range of 2.00 to 11.00. As shown in Fig. 6(a), upon excitation
at 270 nm, for the EuIII-dtpa-bis(HBT) solution, the fluores-
cence response did not change much with an increase in the
pH value. In contrast, for the EuIII-dtpa-bis(HBT) + N2H4
solution, the fluorescence responses significantly increased
with an increase in pH in the range of 2.00 to 6.00. However,
when pH = 7, the fluorescence response reached the maximum,
and then the fluorescence responses did not change even with a
further increase in pH. The experimental results show that
under weakly alkaline conditions, hydrazinolysis is occurred
Fig. 4 Fluorescence spectra ((lex = 270 nm) (a) and (lex = 325 nm) (b)) of
EuIII-dtpa-bis(HBT) in the absence and presence of hydrazine (N2H4)
in aqueous solution ([EuIII-dtpa-bis(HBT)] = 50.0 mM, [N2H4] = [HBT] =
100.0 mM, [Tris–HCl/DMSO] = 10 mmol LÀ1, pH = 7.50, v(water)/v(DMSO)
9 : 1 and Tsolu = 25.00 Æ 0.02 1C).
=
a strong fluorescence emission peak after the addition of N2H4 to
the EuIII-dtpa-bis(HBT) solution. Thus, N2H4 can be detected by
EuIII-dtpa-bis(HBT) (lex = 325 nm) due to the cleavage of the ester
bonds. In summary, the two fluorescence peaks for the synthesized
EuIII-dtpa-bis(HBT) appear at 470 nm (lex = 270 nm) and 480 nm
(lex = 325 nm). Thus, based on the above experimental results, EuIII-
dtpa-bis(HBT) has the potential to detect N2H4 at two different
excitation wavelengths (lex = 270 nm and 325 nm).
To compare the fluorescence changes in the EuIII-dtpa-
bis(HBT) solution in the presence and absence of N2H4, images
of HBT (1), EuIII-dtpa-bis(HBT) (2) and EuIII-dtpa-bis(HBT) +
N2H4 (3) were photographed under ultraviolet light and visible
light, as shown in Fig. 5. Under ultraviolet light, the HBT
Fig. 6 Fluorescence intensities ((lex = 270 nm and lem = 470 nm) (a) and
(lex = 325 nm and lem = 480 nm) (b)) of EuIII-dtpa-bis(HBT) and EuIII-dtpa-
bis(HBT) + N2H4 at different pH values (2.00–11.00) ([EuIII-dtpa-bis(HBT)] =
Fig. 5 Fluorescence pictures ((ultraviolet-light) (a) and (visible-light) (b)) of
HBT (1), EuIII-dtpa-bis(HBT) (2) and EuIII-dtpa-bis(HBT) + N2H4 (3) ([HBT] =
[EuIII-dtpa-bis(HBT)] = [EuIII-dtpa-bis(HBT) + N2H4] = 50.0 mM, [Tris–HCl/
DMSO] = 10 mmol LÀ1, pH = 7.50, v(water)/v(DMSO) = 9:1 and = 25.00 Æ 0.02 1C).
50.0 mM, [N2H4] = 100.0 mM, [Tris–HCl/DMSO] = 10 mmol LÀ1, v(water)
/
v(DMSO) = 9 : 1 and Tsolu = 25.00 Æ 0.02 1C).
16482 | New J. Chem., 2019, 43, 16478--16489 This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2019

View Article Online
Paper
NJC
between N2H4 and EuIII-dtpa-bis(HBT), releasing the HBT fluoro-
phore and producing EuIII-dtpa-bis(N2H4).
Similar results were also obtained upon excitation at
325 nm, as shown in Fig. 6(b). The fluorescence responses of
the EuIII-dtpa-bis(HBT) solution were almost unchanged in the
pH range of 2.00–11.00. For the EuIII-dtpa-bis(HBT) + N2H4
solution, the fluorescence responses were enhanced with an
increase in pH in the range of 2.00 to 6.00. However, when
pH = 7, the fluorescence response reached the maximum, and
then the fluorescence responses hardly changed even when the
pH was further increased. Apparently, the optimum pH for the
detection of N2H4 using EuIII-dtpa-bis(HBT) is weak alkalinity
upon excitation at both 270 nm and 325 nm.
The selectivity of EuIII-dtpa-bis(HBT) for N2H4
It is known that it is of great significance to study the selectivity
of a fluorescent probe for the target. Thus, to demonstrate the
selectivity of EuIII-dtpa-bis(HBT) to N2H4, the effects of various
interferents on the fluorescence responses of EuIII-dtpa-
bis(HBT) were investigated. As shown in Fig. 7(a-1), upon
excitation at 270 nm, EuIII-dtpa-bis(HBT) only showed a weak
fluorescence emission peak. After adding N2H4, the fluores-
cence response of EuIII-dtpa-bis(HBT) at 470 nm (lex = 270 nm)
was significantly enhanced, and little effect on the fluorescence
responses of EuIII-dtpa-bis(HBT) was observed upon the addition
of other interferents. This is because hydrazinolysis occurred
between N2H4 and EuIII-dtpa-bis(HBT), releasing HBT and pro-
ducing EuIII-dtpa-bis(N2H4), which are both strong fluorescent
compounds. The more intuitive comparisons can be seen in
Fig. 7(a-2), where in the presence and absence of interferents, no
obvious changes were observed for the detection of hydrazine
using EuIII-dtpa-bis(HBT).
Similar results were also obtained upon excitation at
325 nm, as shown in Fig. 7(b). For the EuIII-dtpa-bis(HBT)
solution, a weak fluorescence response was displayed at
480 nm (lex = 325 nm). However, after the addition of N2H4,
the fluorescence response of the EuIII-dtpa-bis(HBT) + N2H4
solution at 480 nm (lex = 325 nm) was enhanced. This is
because the hydrazinolysis of EuIII-dtpa-bis(HBT) occurs in
the presence of N2H4 and the HBT fluorophore is released,
resulting in an increase in the fluorescence response. However,
after adding other interferents, all the fluorescence responses
of the EuIII-dtpa-bis(HBT) solutions at 480 nm barely changed.
The corresponding histogram is shown in Fig. 7(b-2), where the
fluorescence responses of the EuIII-dtpa-bis(HBT) solutions in
the presences of various interferents were almost equal to that
of the EuIII-dtpa-bis(HBT) solution. However, after adding
N2H4, the fluorescence response of the EuIII-dtpa-bis(HBT)
solution was different from that of the others. Thus, these
results show that EuIII-dtpa-bis(HBT) can be used to detect
N2H4 specifically upon excitation at 279 nm and 325 nm.
Fig. 7 Fluorescence spectra ((lex = 270 nm) (a-1) and (lex = 325 nm) (b-1))
and corresponding histograms ((lem = 470 nm) (a-2) and (lem = 480 nm)
(b-2)) of EuIII-dtpa-bis(HBT) in aqueous solution in the presence of inter-
ferents (green bars) and N2H4 (blue bar) ([EuIII-dtpa-bis(HBT)] = 50.0 mM,
[interferent] = 100.0 mM and [N2H4] = 100.0 mM, [Tris–HCl/DMSO] =
10 mmol LÀ1, pH = 7.50, v(water)/v(DMSO) = 9 : 1 and Tsolu = 25.00 Æ 0.02 1C).
The anti-interference ability of EuIII-dtpa-bis(HBT) for N2H4
The anti-interference ability of EuIII-dtpa-bis(HBT) for various
interferents that widely coexist with N2H4 in aqueous solutions was solution, a weak fluorescence response was displayed at 470 nm
tested. As can be seen from Fig. 8(a-1), for the EuIII-dtpa-bis(HBT) (lex = 270 nm). The addition of N2H4 caused a dramatic
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2019 New J. Chem., 2019, 43, 16478--16489 | 16483

View Article Online
NJC
Paper
Fig. 9 Fluorescence spectra ((lex = 270 nm) (a-1) and (lex = 325 nm) (b-1)) of
EuIII-dtpa-bis(HBT) in aqueous solutions with different concentrations of hydra-
zine (N2H4) ranging from 0.00 Â 10À5 mol LÀ1 to 10.00 Â 10À5 mol LÀ1 and the
linear responses of the corresponding fluorescence intensities (lem = 470 nm
(a-2) and lem = 480 nm (b-2)) as a function of hydrazine (N2H4) concentration
Fig. 8 Fluorescence spectra ((lex = 270 nm) (a-1) and (lex = 325 nm) (b-1)) and
corresponding histograms ((lem = 470 nm) (a-2) and (lem = 480 nm) (b-2)) of
EuIII-dtpa-bis(HBT), EuIII-dtpa-bis(HBT) + N2H4 and EuIII-dtpa-bis(HBT) + N2H4 +
L (L is various interferents (green bars) or N2H4 (blue bar)) ([EuIII-dtpa-bis(HBT)] =
50.0 mM, [interferent] = 100.0 mM, [N2H4] = 100.0 mM, [Tris–HCl/DMSO] =
10 mmol LÀ1, pH = 7.50, v(water)/v(DMSO) = 9:1 and Tsolu = 25.00 Æ 0.02 1C).
(0.25–75 mM) ([EuIII-dtpa-bis(HBT)] = 50.0 mM, [Tris–HCl/DMSO] = 10 mmol LÀ1
pH = 7.50, v(water)/v(DMSO) = 9:1 and Tsolu = 25.00 Æ 0.02 1C).
,
fluorescence response for EuIII-dtpa-bis(HBT), but no prominent
fluorescence responses of EuIII-dtpa-bis(HBT) + N2H4 were observed detection of N2H4 using EuIII-dtpa-bis(HBT) in the presence and
after adding other interferents. A more intuitive comparison for the absence of other interferents can be seen in Fig. 8(a-2). The above
16484 | New J. Chem., 2019, 43, 16478--16489 This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2019

View Article Online
Paper
NJC
results indicate that EuIII-dtpa-bis(HBT) possesses strong anti-
interference ability toward N2H4 in the presence of interferents
upon excitation at 270 nm.
Similarly, as shown in Fig. 8(b-1), upon excitation at 325 nm, for
the EuIII-dtpa-bis(HBT) solution, a weak fluorescence response was
displayed at 480 nm (lex = 325 nm). For EuIII-dtpa-bis(HBT) + N2H4
solution, the fluorescence response at 480 nm (lex = 325 nm)
increased obviously. However, the fluorescence responses of the
EuIII-dtpa-bis(HBT) + N2H4 solutions containing interferents were
almost unchanged. The more intuitive comparisons in Fig. 8(b-2)
show that the fluorescence response of EuIII-dtpa-bis(HBT) + N2H4
is consistent with that of the EuIII-dtpa-bis(HBT) + N2H4 solutions
containing different types of interferents. This demonstrates
that the EuIII-dtpa-bis(HBT) (lex = 325 nm) also has strong anti-
interference ability as fluorescence probe for the detection of
N2H4.
Fig. 10 Reaction mechanism of EuIII-dtpa-bis(HBT) and hydrazine (N2H4).
N2H4, releasing the HBT fluorophore and producing EuIII-dtpa-
bis(N2H4), which are both strong fluorescence compounds. For
the detection of N2H4, the EuIII-dtpa-bis(HBT) solution shows
excellent anti-interference ability due to the complementary of
its two different excitation wavelengths. Therefore, EuIII-dtpa-
bis(HBT) as a dual-excitation fluorescence probe can be applied
to detect N2H4.
Effect of N2H4 concentration on the fluorescence responses of
EuIII-dtpa-bis(HBT)
The fluorescence responses of EuIII-dtpa-bis(HBT) are closely
related to the N2H4 concentration. Therefore, it was necessary
to study the relationship between the N2H4 concentration and
the fluorescence responses of EuIII-dtpa-bis(HBT). As shown in
Fig. 9(a-1) and (b-1), the fluorescence responses of EuIII-dtpa-
Detection of N2H4 in real water samples
To evaluate the feasibility of EuIII-dtpa-bis(HBT) in actual water
samples, reservoir exit water, reservoir middle water, tap water
and drinking water were selected as research objects, and the
concentration of N2H4 in the real samples was detected via the
standard addition method. As shown in Fig. 11(a-1), for EuIII-
dtpa-bis(HBT), a weak fluorescence response was displayed at
470 nm (lex = 270 nm).
bis(HBT) solution at 470 nm (lex = 270 nm) and 480 nm (lex
=
325 nm) both increased gradually, respectively, with an increase
in N2H4 concentration. In addition, as shown in Fig. 9(a-2) and
(b-2), excellent linear relationships between the fluorescence
responses of EuIII-dtpa-bis(HBT) and N2H4 concentration were
obtained in the range of 0.25 mM to 75 mM. The corresponding
linear equations were y = 13.207x + 61.172 (R2 = 0.9949) and
y = 45.909x + 132.66 (R2 = 0.9829), respectively.
After different water samples were added to EuIII-dtpa-
bis(HBT), almost the same fluorescence responses were
obtained for the same concentration of N2H4. However, they
all presented a good upward gradient with an increase in the
concentration of N2H4 in the range of 0.2–1.0 mM. More
detailed descriptions are shown in Fig. 11(a-2), where the
fluorescence responses of the EuIII-dtpa-bis(HBT) solutions
containing the same concentration of N2H4 in four water
samples were the same and close to that of the control water
The detection limit of EuIII-dtpa-bis(HBT) for N2H4 was
about 14 ppb (0.283 mM) (lex = 270 nm) and 9 ppb (0.182 mM)
(lex = 325 nm) based on the formula LOD = 3s/s.55 Compared
with other methods (Table 1), the obtained low detection limit
and wide detection range indicate EuIII-dtpa-bis(HBT) can be
successfully applied for the quantitative analysis of N2H4.
Mechanism of EuIII-dtpa-bis(HBT) for N2H4 detection
Fig. 10 displays two weak fluorescence responses for EuIII-dtpa- samples. Therefore, the N2H4 in the actual water samples (lex
=
bis(HBT) at 470 nm (lex = 270 nm) and 480 nm (lex = 325 nm). 270 nm) could be specifically detected using EuIII-dtpa-
After the addition of N2H4, strong fluorescence responses of bis(HBT). As can be seen from Fig. 11(b-1), the fluorescence
EuIII-dtpa-bis(HBT) were observed at 470 nm (lex = 270 nm) and responses of the EuIII-dtpa-bis(HBT) solutions at 480 nm (lex
=
480 nm (lex = 325 nm). The sensing mechanism is due to the 325 nm) increased gradually with an increase in the concen-
occurrence of hydrazinolysis between EuIII-dtpa-bis(HBT) and tration of N2H4 in the four water samples. As shown in
Table 1 Comparison of the proposed method with other reported methods
Analytical method
LOD (mol LÀ1
)
Linear range (mol LÀ1
)
Ref.
Electrodepositing
0.50 Â 10À6
2.00 Â 10À7
1.56 Â 10À7
0.10 Â 10À6
0.08 Â 10À6
2.50 Â 10À6 to 5.00 Â 10À4
5.00 Â 10À7 to 1.00 Â 10À4
—
14
4
8
15
Chemiluminescence
Spectrophotometry
Square wave voltammetry
Electrochemical
0.30 Â 10À6 to 7.00 Â 10À4
2.00 Â 10À6 to 4.00 Â 10À5
2.50 Â 10À5 to 7.50 Â 10À5
2.50 Â 10À5 to 7.50 Â 10À5
16
Fluorescent probe
2.83 Â 10À7 (lex = 270 nm)
1.82 Â 10À7 (lex = 325 nm)
This work
This work
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2019 New J. Chem., 2019, 43, 16478--16489 | 16485

View Article Online
NJC
Paper
Table 2 Determined results of the hydrazine (N2H4) content in the four
water samples with three different concentrations (lex = 270 nm). (Sample
1: tap water, sample 2: drinking water, sample 3: reservoir exit water and
sample 4: reservoir middle water)
Sample
Added (mol LÀ1
)
Found (mol LÀ1
)
Recovery (%)
Sample-1-1
Sample-1-2
Sample-1-3
Sample-2-1
Sample-2-2
Sample-2-3
Sample-3-1
Sample-3-2
Sample-3-3
Sample-4-1
Sample-4-2
Sample-4-3
2.00 Â 10À5
5.00 Â 10À5
10.00 Â 10À5
2.00 Â 10À5
5.00 Â 10À5
10.00 Â 1À0À5 5
2.00 Â 10
2.01 Â 10À5
4.45 Â 10À5
10.27 Â 1À0À5 5
1.92 Â 10À5
4.92 Â 10À5
9.93 Â 10À5
1.98 Â 10
101
89
103
96
98
99
99
95
98
102
95
5.00 Â 10À5
10.00 Â 1À0À5 5
2.00 Â 10
4.75 Â 10À5
9.81 Â 10À5
2.04 Â 10À5
4.74Â 10À5
9.73 Â 10À5
5.00 Â 10À5
10.00 Â 10À5
97
Fig. 11(b-2), the detection effectiveness of the EuIII-dtpa-
bis(HBT) solutions containing the same concentration of
N2H4 in the four different water samples were consistent with
that of the control samples. There were differences in the
fluorescence responses of EuIII-dtpa-bis(HBT) with a gradual
increase in the concentration of N2H4. Therefore, EuIII-dtpa-
bis(HBT) can be used to detect N2H4 in various water samples
upon excitation at 270 nm and 325 nm.
The results of recovery rates tests using the standard addi-
tion method are shown in Tables 2 and 3. Good recovery rates
were achieved in the range of 87% to 102% for the four
different water samples. Therefore, this proves that EuIII-dtpa-
bis(HBT) can quantitatively detect a trace amount of N2H4 in
actual water samples upon excitation at 270 nm and 325 nm.
Theoretical calculation
To demonstrate the sensing mechanism of EuIII-dtpa-bis(HBT)
for N2H4, the frontier molecular orbital energies of dtpa-
bis(HBT) and HBT were calculated using the DFT-B3LYP/6-
31G method. Because EuIII-dtpa-bis(HBT) contains the rare
earth metal Eu3+ ion, it has a complicated composition and
structure. Since the fluorescence change mainly occurs in the
dtpa-bis(HBT) part, only the frontier molecular orbitals of dtpa-
Table 3 Determined results of hydrazine (N2H4) content in the four water
samples with three different concentrations (lex = 325 nm). (Sample 1: tap
water, sample 2: drinking water, sample 3: reservoir exit water and sample
4: reservoir middle water)
Sample
Added (mol LÀ1
)
Found (mol LÀ1
)
Recovery (%)
Fig. 11 Fluorescence spectra ((lex = 270 nm) (a-1) and (lex = 325 nm)
Sample-1-1
Sample-1-2
Sample-1-3
Sample-2-1
2.00 Â 10À5
5.00 Â 10À5
10.00 Â 10À5
2.00 Â 10À5
5.00 Â 10À5
10.00 Â 10À5
2.00 Â 10À5
5.00 Â 10À5
10.00 Â 10À5
2.00 Â 10À5
5.00 Â 10À5
10.00 Â 10À5
2.03 Â 10À5
4.91 Â 10À5
10.14 Â 1À0À5 5
1.74 Â 10À5
5.05 Â 10
102
98
101
87
101
96
99
96
100
97
93
95
(b-1)) and corresponding histograms ((lem = 470 nm) (a-2) and (lem
=
480 nm) (b-2)) of EuIII-dtpa-bis(HBT) in aqueous solutions with different
concentrations of hydrazine (N2H4) in four water samples (sample 1:
tap water, sample 2: drinking water, sample 3: reservoir exit water and Sample-2-2
Sample-2-3
Sample-3-1
Sample-3-2
Sample-3-3
Sample-4-1
Sample-4-2
Sample-4-3
9.58 Â 10À5
1.98 Â 10À5
4.78 Â 10À5
10.04 Â 1À0À5 5
1.94 Â 10À5
4.65 Â 10
sample 4: reservoir middle water) (c0, c1, c2 and c3: blank groups with
corresponding concentrations of hydrazine in purified water [EuIII-dtpa-
bis(HBT)] = 50.0 mM, [Tris–HCl/DMSO] = 10 mmol LÀ1, pH = 7.50, v(water)
v(DMSO) = 9 : 1 and Tsolu = 25.00 Æ 0.02 1C).
/
9.54 Â 10À5
16486 | New J. Chem., 2019, 43, 16478--16489 This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2019

View Article Online
Paper
NJC
Fig. 12 HOMO–LUMO energy levels and interfacial plots of the molecular
orbitals for dtpa-bis(HBT) and HBT.
bis(HBT) were calculated. As can be seen in Fig. 12, the energy
differences between the HOMO and LUMO of dtpa-bis(HBT)
and HBT were 4.1033 eV and 3.1210 eV, respectively. Because
hydrazinolysis occurred between dtpa-bis(HBT) and N2H4, the
energy difference (3.1210 eV) between the HOMO and LUMO of
produced HBT became lower than that (4.1033 eV) between
HOMO and LUMO of dtpa-bis(HBT). It can be seen that the
decrease in the energy gap values of HBT compared with that of
dtpa-bis(HBT) confirm that HBT is more easily released and
emits strong fluorescence.
Fig. 14 Bright-field image (1) and fluorescence image (blue light channel)
(2) of BV2 cells in the presence of EuIII-dtpa-bis(HBT) (a) and EuIII-dtpa-
bis(HBT) + N2H4 (b) ([EuIII-dtpa-bis(HBT)] = [EuIII-dtpa-bis(HBT) + N2H4] =
30 mM, [Tris–HCl/DMSO] = 10 mmol LÀ1, pH = 7.50, v(water)/v(DMSO) = 9 : 1
and Tsolu = 25.00 Æ 0.02 1C).
EuIII-dtpa-bis(HBT) (30 mM), which grew normally. However, the
size and shape of this group of BV2 cells were different from the
other group of BV2 cells that were treated with EuIII-dtpa-
bis(HBT) + N2H4 (30 mM) (in Fig. 14(b-1)). This suggests that
the presence of N2H4 affects the normal growth of cells to some
extent. As can be seen from Fig. 14(a-2), the BV2 cells were
treated with EuIII-dtpa-bis(HBT) (30 mM), which exhibited
almost no fluorescence in the blue channel. However, in
Fig. 14(b-2), the BV2 cells that were treated with EuIII-dtpa-
bis(HBT) + N2H4 exhibited obvious blue fluorescence in the
blue channel. Thus, these results demonstrate that EuIII-dtpa-
bis(HBT) can be applied to detect N2H4 in living cells.
Cytotoxicity assay
It is great significance to study the cytotoxicity of the fluores-
cent probe for detecting intracellular N2H4 in practical applica-
tions. Thus, the effects of different concentrations of EuIII-dtpa-
bis(HBT) on its cytotoxicity were investigated via the MTT assay
on BV2 cells. As shown in Fig. 13, the EuIII-dtpa-bis(HBT)
solution exhibited low toxicity to the BV2 cells. Even at a
concentration of EuIII-dtpa-bis(HBT) solution of up to 0.5 mM,
the survival rate of BV2 cells was 89%. Therefore, demonstrates
that EuIII-dtpa-bis(HBT) as a dual-excitation fluorescence probe
is a potential substance for cell imaging.
Conclusion
Cellular imaging
In this work, EuIII-dtpa-bis(HBT) as a dual-excitation fluorescence
probe, was developed for N2H4 sensing. In weakly alkaline
conditions, after N2H4 was added to EuIII-dtpa-bis(HBT), its ester
bonds were cleaved, releasing the HBT fluorophore and producing
EuIII-dtpa-bis(N2H4), which are both fluorescent compounds. HBT
and EuIII-dtpa-bis(N2H4) both show relatively strong fluorescence
responses at 480 nm (lex = 325 nm) and 470 nm (lex = 270 nm),
respectively. Good linear relationships were obtained between the
fluorescence responses of EuIII-dtpa-bis(HBT) and N2H4 concentra-
tions (0.25–75 mM) with the limit of detection of 14 ppb (0.283 mM)
and 9 ppb (0.182 mM), respectively. The theoretical calculation
results indicated that HBT is more easily released and emits strong
fluorescence. The cytotoxicity and cellular imaging experiments
demonstrated that EuIII-dtpa-bis(HBT) can also react with N2H4 in
living cells.
The cellular imaging of the detection of N2H4 in living cells by
EuIII-dtpa-bis(HBT) was evaluated. As shown in Fig. 14(a-1),
in the bright field, one group of BV2 cells were treated with
Conflicts of interest
Fig. 13 Calculated viability of BV2 cells in the presence of EuIII-dtpa-
bis(HBT) by MTT assay.
There are no conflicts to declare.
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2019 New J. Chem., 2019, 43, 16478--16489 | 16487

View Article Online
NJC
Paper
21 J. Wu, J. Pan, Z. Ye, L. Zeng and D. Su, Sens. Actuators, B,
2018, 274, 274–284.
22 Y. Qian, J. Lin, L. Han, L. Lin and H. Zhu, Biosens. Bioelec-
tron., 2014, 58, 282–286.
23 M. G. Choi, J. Hwang, J. O. Moon, J. Sung and S. K. Chang,
Org. Lett., 2011, 135, 5260–5263.
24 Y. Hao, Y. Zhang, K. Ruan, W. Chen, B. Zhou, X. Tan,
Y. Wang, L. Zhao, G. Zhang, P. Qu and M. Xu, Sens.
Actuators, B, 2017, 244, 417–424.
25 S. Goswami, S. Das, K. Aich, B. Pakhira, S. Panja, S. K.
Mukherjee and S. Sarkar, Org. Lett., 2013, 15, 5412–5415.
26 X. Jin, C. Liu, X. Wang, H. Huang, X. Zhang and H. Zhu,
Sens. Actuators, B, 2015, 216, 141–149.
27 W. D. Wang, Y. Hu, Q. Li and S. L. Hu, Inorg. Chim. Acta,
2018, 477, 206–211.
28 L. Cui, C. Ji, Z. Peng, L. Zhong, C. Zhou and L. Yan, Anal.
Chem., 2014, 86, 4611–4617.
29 M. V. R. Raju, E. C. Prakash, H. C. Chang and H. C. Lin, Dyes
Pigm., 2014, 103, 9–20.
Acknowledgements
The authors greatly acknowledge the National Science Foundation
of China (21371084 and 31570154), Key Laboratory Basic Research
Foundation of Liaoning Provincial Education Department
(L2015043), Liaoning Provincial Department of Education Innova-
tion Team Projects (LT2015012) and Undergraduate Teaching
Reform Projects of Liaoning University (JG2016YB0034) for finan-
cial support. The authors also thank our colleagues and other
students for their participating in this work.
Notes and references
1 H. Lv, H. Sun, S. Wang and F. Kong, Spectrochim. Acta, Part
A, 2018, 196, 160–167.
2 S. D. Zelnick, D. R. Mattie and P. C. Stepaniak, Aviation,
2003, 74, 1285–1291.
3 Z. K. He, B. Fuhrmann and U. Spohn, Anal. Chim. Acta, 2000,
409, 83–91.
4 A. Safavi and M. A. Karimi, Talanta, 2002, 58, 785–792.
5 A. Safavi, G. Absalan and F. Bamdad, Anal. Chim. Acta, 2008,
610, 243–248.
30 X. Dai, Z. Y. Wang, Z. F. Du, J. Y. Miao and B. X. Zhao, Sens.
Actuators, B, 2016, 232, 369–374.
31 B. Li, Z. He, H. Zhou, H. Zhang, W. Li, T. Cheng and G. Liu,
Dyes Pigm., 2017, 146, 300–304.
32 Q. Wu, J. Zheng, W. Zhang, J. Wang, W. Liang and
F. J. Stadler, Talanta, 2019, 195, 857–864.
6 A. Salimi, L. Miranzadeh and R. Hallaj, Talanta, 2008, 75,
147–156.
33 F. Takashi, S. Satoshi and M. Atsushi, Biochem. Biophys. Res.
Commun., 2004, 317, 77–83.
34 Y. Hao, Y. Zhang, K. Ruan, W. Chen, B. Zhou, X. Tan,
Y. Wang, L. Zhao, G. Zhang, P. Qu and M. Xu, Sens.
Actuators, B, 2017, 244, 417–424.
35 Z. Lu, X. Shi, Y. Ma, W. Fan, Y. Lu, Z. Wang and C. Fan, Sens.
Actuators, B, 2018, 258, 42–49.
36 X. Jiang, F. Tian, F. Yang, X. Dou, J. Wang and Y. Song, Sens.
Actuators, B, 2017, 238, 605–612.
7 P. Wuamprakhon, A. Krittayavathananon, N. Ma,
N. Phattharasupakun, T. Maihom, J. Limtrakul and
M. Sawangphruk, J. Electroanal. Chem., 2018, 808, 124–132.
8 D. Kosyakov, A. Amosov, N. Ul’yanovskii, A. Ladesov,
Y. Khabarov and O. Shpigun, J. Anal. Chem., 2017, 72,
171–177.
9 R. B. Channon, M. B. Joseph, E. Bitziou, A. W. T. Bristow,
A. D. Ray and J. V. Macpherson, Anal. Chem., 2015, 87,
10064–10071.
37 F. Tian, X. Jiang, X. Dou, Q. Wu, J. Wang and Y. Song,
Spectrochim. Acta, Part A, 2017, 179, 194–200.
38 F. Yang, Z. Yu, X. Li, P. Ren, G. Liu, Y. Song and J. Wang,
Spectrochim. Acta, Part A, 2018, 203, 461–471.
10 J. R. Stetter, K. F. Blurton, A. M. Valentine and K. A.
Tellefsen, J. Electrochem. Soc., 1978, 125, 1804–1807.
11 J. W. Mo, B. Ogorevc, X. Zhang and B. Pihlar, Electroanalysis,
2015, 12, 48–54.
´
39 S. Benazeth, J. Purans, M. C. Chalbot, M. K. Nguyen-Van-
12 Z. Feng, D. Li, L. Wang, Q. Sun, P. Lu, P. Xing and M. An,
Electrochim. Acta, 2019, 304, 275–281.
13 D. M. Nguyen and Q. B. Bui, J. Electroanal. Chem., 2019, 832,
444–452.
14 G. Wang, C. Zhang, X. He, Z. Li, X. Zhang, W. Lun and
B. Fang, Electrochim. Acta, 2010, 55, 7204–7210.
15 A. Benvidi, P. Kakoolaki, H. R. Zare and R. Vafazadeh,
Electrochim. Acta, 2011, 56, 2045–2050.
16 T. Pal, S. Dutta, C. Ray, S. Mallick, S. Sarkar and A. Roy, RSC
Adv., 2015, 5, 51690–51700.
17 Y. Liu, D. Ren, J. Zhang, H. Li and X. F. Yang, Dyes Pigm.,
2019, 162, 112–119.
18 X. Zheng, S. Wang, H. Wang, R. Zhang, J. Liu and B. Zhao,
Spectrochim. Acta, Part A, 2015, 138, 247–251.
19 W. Xu, W. Liu, T. Zhou, Y. Yang and W. Li, J. Photochem.
Photobiol., A, 2018, 356, 610–616.
Duong, L. Nicolas, F. Keller and A. Gaudemer, Inorg. Chem.,
1998, 37, 3667–3674.
40 N. Sakagami, J. I. Homma, T. Konno and K. I. Okamoto, Acta
Crystallogr., 1997, 53, 1378–1381.
41 J. Massue, S. J. Quinn and T. Gunnlaugsson, J. Am. Chem.
Soc., 2008, 130, 6900–6901.
42 M. Zhang, Z. B. Qu, H. Y. Ma, T. Zhou and G. Shi, Chem.
Commun., 2014, 50, 4677–4679.
43 X. Li, Z. Yu, N. Li, H. Jia, H. Wei, J. Wang and Y. Song, Dyes
Pigm., 2019, 162, 281–294.
44 M. Zhang, Z. Qu, C. M. Han, L. F. Lu, Y. Y. Li, T. Zhou and
G. Shi, Chem. Commun., 2014, 50, 12855–12858.
45 J. E. Kwon and S. Y. Park, Adv. Mater., 2011, 23, 3615–3642.
46 J. Ma, J. Zhao, P. Yang, D. Huang, C. Zhang and Q. Li, Chem.
Commun., 2012, 48, 9720–9722.
´
`
47 J. M. Couchet, J. Azema and P. Tisnes, Inorg. Chem. Com-
20 Y. Zhang, Y. Huang, Y. Yue, J. Chao, F. Huo and C. Yin, Sens.
Actuators, B, 2018, 273, 944–950.
mun., 2003, 6, 978–981.
16488 | New J. Chem., 2019, 43, 16478--16489 This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2019

View Article Online
Paper
NJC
48 E. Debroye, S. V. Eliseeva, S. Laurent, L. V. Elst, S. Petoud, R. N. 52 S. Wang, N. Li, W. Pan and B. Tang, TrAC, Trends Anal.
Muller and T. N. Parac-Vogt, Eur. J. Inorg. Chem., 2013, 2629–2639. Chem., 2012, 39, 3–37.
49 H. H. Shi and Y. S. Yang, J. Alloys Compd., 1994, 207-208, 53 C. Sun, Y. Wu, P. Wang, G. Zhou, X. Zong, B. Chen and M. Ji,
29–32. J. Sol-Gel Sci. Technol., 2014, 71, 211–216.
50 A. Bertin, T. Muller, J. L. Gallani and D. Felder-Flesch, 54 Z. Li, W. Zhang, C. Liu, M. Yu, H. Zhang, L. Guo and L. Wei,
Tetrahedron Lett., 2007, 48, 4699–4702. Sens. Actuators, B, 2017, 241, 665–671.
51 C. Jolley, F. R. Burnet and P. J. Blower, Appl. Radiat. Isot., 55 G. L. Long and J. D. Winefordner, Anal. Chem., 1983, 55,
1996, 47, 623–626. 712A–724A.
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2019 New J. Chem., 2019, 43, 16478--16489 | 16489