A New Reactive 1,8-Naphthalimide Derivative for Highly Selective and Sensitive Detection of Hg2+

Article abstract of DOI:10.1007/s10895-017-2061-y

A 1,8-naphthalimide derivative with a reactive aliphatic hydroxyl was designed and synthesized as a fluorescent probe. Its structure was characterized by IR, ¹H NMR, ¹³C NMR, LC-MS and HPLC. The probe showed high selectivity and sensitivity to Hg²⁺ over other metal ions such as Pb²⁺, Na⁺, K⁺, Cd²⁺, Cr³⁺, Zn²⁺, Cu²⁺, Ni²⁺, Ca²⁺, Fe³⁺, Fe²⁺, Co²⁺, Mn²⁺ and Mg²⁺ in MeCN/H₂O (15/85, v/v). The increase in fluorescence intensity was linearly proportional to the concentration of Hg²⁺ in the range of 18–40?μM with a detection limit of 1.38?×?10^?7?mol/L. The probe could work in a pH span of 4.3–9.0 and respond to Hg²⁺ quickly with strong anti-interference ability. Job’s plot suggested a 1:2 complex of the probe and Hg²⁺.

Full text of DOI:10.1007/s10895-017-2061-y

J Fluoresc
DOI 10.1007/s10895-017-2061-y
ORIGINAL ARTICLE
A New Reactive 1,8-Naphthalimide Derivative for Highly
2+
Selective and Sensitive Detection of Hg
1
,2
1,2
1,2
3
1,2
Feng Lv & Yufen Chen & Tengxuan Tang & Yuhua Chen & Dongmei Xu
Received: 26 October 2016 /Accepted: 2 March 2017
#
Springer Science+Business Media New York 2017
Abstract A 1,8-naphthalimide derivative with a reactive ali-
Introduction
phatic hydroxyl was designed and synthesized as a fluorescent
1
13
2+
probe. Its structure was characterized by IR, H NMR,
C
Hg is a kind of common heavy metal pollutant which can
spread in the air, soil and water, accumulate in human body
through food chain accumulation and cause a lot of health
problems [1, 2]. Therefore, it is very important to detect the
NMR, LC-MS and HPLC. The probe showed high selectivity
2
+
2+
and sensitivity to Hg over other metal ions such as Pb ,
+
+
2+
3+
2+
2+
2+
2+
3+
2+
2+
Na , K , Cd , Cr , Zn , Cu , Ni , Ca , Fe , Fe , Co ,
2
+
2+
2+
Mn and Mg in MeCN/H O (15/85, v/v). The increase in
presence of Hg . As being highly sensitive, simple, cheap as
2
fluorescence intensity was linearly proportional to the concen-
well as on-site and timely, fluorescent probe has been of great
2
+
tration of Hg in the range of 18–40 μM with a detection
concern in the detection of heavy metal ions [3–5].
limit of 1.38 × 10− mol/L. The probe could work in a pH
7
In the detection of Hg , fluorescent probe has a sustained
2+
2
+
2+
span of 4.3–9.0 and respond to Hg quickly with strong anti-
interference ability. Job’s plot suggested a 1:2 complex of the
development. Fluorophores of Hg fluorescent probe can be
rhodamine [6–9], dansyl chloride [10–12], quinoline [13, 14],
coumarin [15, 16], BODIPY [17, 18], fluorescein [19, 20] or
2
+
probe and Hg .
1,8-naphthalimide [21], and the recognition groups connected
to the fluorophores are the myriads of changes but mainly
hetero atom groups containing N, O, S atoms.
.
.
Keywords Fluorescent probe Naphthalimide
2
+
.
Phenyl isothiocyanate Hg
1,8-Naphthalimide derivatives have strong electron-
withdrawing imide group and strong electron donating
group at C-4 of the naphthalene ring. This kind of structure
tends to form electron transfer and produces rich optical
phenomena. Several 1,8-naphthalimide-based fluorescent
Electronic supplementary material The online version of this article
doi:10.1007/s10895-017-2061-y) contains supplementary material,
which is available to authorized users.
2
+
(
sensors for Hg have been reported. However, they most-
ly exist shortcomings, such as complex structure and diffi-
cult synthesis [22, 23], high solvent content of the test
system [24, 25], poor anti-jamming [26, 27], and incom-
plete performance study [28, 29].
*
*
Yuhua Chen
chenyh@suda.edu.cn
Dongmei Xu
High selectivity is crucial to fluorescent probe, while water
solubility can improve the probe’s availability. In this paper,
we use 4-bromine-1,8-naphthalic anhydride as fluorophore
precusor, ethanol amine as water solubility and reactivity pro-
vider, hydrazine monohydrate as bridge and phenyl isothiocy-
anate as receptor to construct a new fluorescent probe. As
expected, the probe has satisfactory water solubility and high
xdm.sd@163.com
1
2
College of Chemistry, Chemical Engineering and Materials Science,
Soochow University, Suzhou, Jiangsu 215123, China
Jiangsu Key Laboratory of Advanced Functional Polymer Design
and Application, Soochow University, Suzhou, Jiangsu 215123,
China
2
+
3
selectivity toward Hg . In addition, the hydroxyl in ethanol
amine provides the probe reactivity which can be used for the
College of Pre-clinical Medical and Biological Science, Soochow
University, Suzhou 215123, China

J Fluoresc
further modification of the probe itself and other materials.
Exceptionally, this hydroxyl also can participate in the recog-
nition of Hg .
Probe Synthesis
2
+
2-(2-(2-hydroxyethyl)-1,3-dioxo-2,3-dihydro-1H-benzo[de]-
isoquinolin-6-yl)-N-phenylhydrazine-1-carbothioamide
(HTUN) was synthesized by three-step reactions between 4-
bromo-1,8-naphthalic anhydride, ethanol amine, hydrazine
monohydrate and phenyl isothiocyanate, as shown in
Scheme 1.
Experimental
Materials
Intermediate N-hydroxyethyl-4-bromine-1,8-
naphthalimide (HBN) was obtained as a milky white solid
with a yield of 85.6% according to reference [30]. Based on
reference [31], HBN reacted with hydrazine hydrate to get
intermediate N-hydroxyethyl-4-diazanyl-1,8-naphthalimide
(HHN) with a yield of 89.0%. Phenyl isothiocyanate
(0.108 mL, 0.91 mmol) and HHN (0.15 g, 0.55 mmol) were
added in 20 mL absolute ethanol. Then the mixture was stirred
and heated to reflux for 24 h. After cooled to room tempera-
ture, filtered and the filter cake was washed with absolute
4
-bromine-1,8-naphthalic anhydride (98%) was purchased
from Anshan HIFI Chemical Co., Ltd., phenyl isothiocyanate
98%) was bought from Yake Chemical Reagent Co., Ltd.,
ethanol amine, NH NH ·H O (85%), the solvents and metal
(
2
2
2
ions of chloride and nitrate, such as NaCl, KCl, MgCl , CaCl ,
2
2
CrCl ·6H O, MnSO ·H O, FeCl ·6H O, FeCl ·7H O, CoCl ·
3
2
4
2
3
2
2
2
2
6
H O, Ni(NO ) ·6H O, CuCl ·2H O, HgCl , Pb(CH COO) ,
2 3 2 2 2 2 2 3 2
Zn(NO ) ·6H O, CdCl ·2.5H O, were provided by
3
2
2
2
2
Sinopharm Chemical Reagent Co., Ltd. All of the reagents
in this paper were the best commercial products and they were
used without further purification. The solvents used in synthe-
sis were analytical grade, others were spectroscopic grade.
ethanol (2 mL × 3). The probe (HTUN) was achieved as a
1
brown powder (0.156 g). Yield: 69.6%. H NMR (DMSO-d ,
6
400 MHz, δ ppm): 10.11 (s, 2H), 9.86 (s, 1H), 8.69 (d,
J = 8 Hz, 1H), 8.48 (d, J = 6.8 Hz, 1H), 8.42 (d, J = 8.8 Hz,
1H), 7.77 (t, J = 7.6 Hz, 1H), 7.43 (d, J = 6.4 Hz, 2H), 7.31 (t,
J = 7.4 Hz, 2H), 7.15 (t, J = 7 Hz, 1H), 6.98 (d, J = 8.4 Hz, 1H),
Deionized water (H O) was used in the experiments unless
2
specified otherwise.
4
.81 (t, J = 5.6 Hz, 1H), 4.13 (t, J = 6.4 Hz, 2H), 3.60 (t,
1
3
J = 6.2 Hz, 2H) (Fig. S1). C NMR (DMSO-d , 300 MHz,
6
Apparatus
δ ppm): 42.007, 58.419, 105.921, 112.107, 119.887, 122.352,
1
25.344, 125.827, 126.599, 128.504, 129.411, 131.349,
Infrared (IR) spectra were measured on a TENSOR27 spec-
trometer (Bruker Optics Co., Germany). LC-mass was per-
formed on an Agilent 1200/6220 spectrometer (Agilent Co.,
134.152, 139.562, 150.321, 163.624, 164.303, 181.828
−1
(Fig. S2). IR (KBr pellet, cm ): 3524, 3234, 3152, 2968,
2893, 1689, 1650, 1587, 1537 (Fig. S3). LC-Mass: m/z:
1
+
+
USA) unless otherwise specified. H NMR spectra were re-
407.1197 ([M + H] ), 429.1007 ([M + Na] ) (Fig. S4).
Purity from HPLC: 99.7% (Fig. S5).
corded on a 400 MHz Varian Unity Inova spectrometer
1
3
(
3
Varian Co., USA). C NMR spectra were obtained on a
00 MHz Varian Unity Inova spectrometer (Varian Co.,
Methods
USA). High performance liquid chromatography (HPLC)
was measured on an Waters 1525 HPLC (Waters Co., USA),
using C18 column (150 mm × 4.6 mm × 5.0 μm) and
UV-Vis Absorption and Fluorescence Test
HTUN was dissolved in MeCN to form a 1 × 10− M stock
3
MeCN/H O (50/50,v/v) as an eluent (the total flux was
2
−2
1
mL/min), and the detection wavelength was 392 nm.
solution. Metal salts were dissolved in H O to get 1 × 10
M
2
2
+
Fluorescence spectra were recorded on a F-2500 spectrofluo-
rometer (Hitachi Co., Japan). pH values were measured with
precision pH test paper (Shanghai Sanaisi Reagent Co., Ltd.,
China). All the detections were carried out at 25 °C unless
otherwise specified.
stock solutions. For the detection of Hg , stock solution of
HTUN (100 μL) and one of the ion stock solution (40 or
100 μL) were added in a 10 mL volumetric flask and diluted
to 10 mL with CH CN and H O to form MeCN/H O (15/85,
3
2
2
v/v) solutions. In fluorescence titration experiments, 100 μL
Scheme 1 Synthetic route
of HTUN

J Fluoresc
2
+
2
4000
4000
000
2000
Pb
1
1
0
0
0
.6
.2
.8
.4
.0
3
+
Cu
1
000
0
3
000
2
+
Fe
0
2
4
2
+
-5
[Hg ] /10 mol/L
2
+
Ni
3+ 2+
Fe ,Zn ,Mn
2+
,
3
Cr ,Co
+
2+
2000
,
2+
+
blank,Na ,K ,
+
2
+
Cd ,Hg
2+
Mg ,Ca
2+
HTUN HTUN
2
+
/
Hg
1
000
0
3
00
450
Wavelength /nm
Fig. 1 UV–vis absorption spectra of HTUN with different ions. Solvent:
MeCN/H O (15/85, v/v), concentration: 10 μM for HTUN, 100 μM for
600
5
00
600
700
2
various ions
Wavelength /nm
Fig. 3 Fluorescence spectra of HTUN with different concentration of
2
+
stock solution of HTUN was mixed with a certain amount of
2
Hg . Solvent: MeCN/H O (15/85, v/v), concentration: 10 μM for
2+
2+
HTUN, from bottom to top, the equiv. of Hg : 1.4, 0.2, 1.0, 0.4, 0.8,
.2, 1.6, 0.6, 0, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2,
.4, 4.6, 4.8, λex: 400 nm, slit width: 5 nm. Inset: the relationship between
the maximal fluorescence intensity F and the concentration of Hg
the Hg stock solution and diluted to 10 mL with CH CN and
3
1
4
H O. The spectra were recorded at 30 min after the mixing. pH
2
was adjusted by 0.1 M HCl and 0.1 M NaOH aqueous solu-
tions. For fluorescence measurements, excitation wavelength
was 400 nm. The excitation and emission slits were set at
2+
5
nm respectively.
2
2
1
800
100
400
2
+
Testing Hg in Spiked Environmental Water
1
mL pond water (after filtration) or tap water from Dushu
Lake Campus of Soochow University was added in 10 mL
volumetric flask, then 20 (or 30) μL stock solution of Hg ,
00 μL stock solution of HTUN and 1.4 mL acetonitrile were
2
+
1
introduced. The mixture was diluted to volume with deionized
water and the fluorescence spectra were recorded. The con-
7
00
0
2
+
centration of Hg was given by the linear relationship be-
tween the maximal fluorescence intensity of the solution and
2
+
the concentration of Hg .
Fig. 4 Effects of coexisting ions on the fluorescence maxima of
Calculation of the Detection Limit and Association Constant
2+
HTUN/Hg . Solvents: MeCN/H
2
O (15/85, v/v), concentration: 10 μM
2+
for HTUN, 40 μM for Hg , λex: 400 nm, slit width: 5 nm, grey column:
2+
2+
The detection limit was calculated by 3S/k [32], in which S is
the standard deviation of five times blank measurement, k is
the slope of the linear fit line in the titration experiment.
HTUN/Hg , slash column: HTUN/Hg /other ion
2800
2100
1400
2
800
100
2+
Hg
2+
HTUN/Hg
2
2+
2+
2+
Co ,Zn ,Fe ,Mn
2+
,
2+
Mg ,Pb ,K ,blank,
2+
+
2
+
+
2+
Cd ,Na ,Ca ,Cr
3+
,
1400
2
+
3+
Ni ,Fe ,Cu
2+
,
700
700
0
HTUN
24 32
450
525
600
675
0
Wavelength /nm
0
8
16
Time /min
Fig. 2 Fluorescence spectra of HTUN with different ions. Solvent:
MeCN/H O (15/85, v/v), concentration: 10 μM for HTUN, 40 μM for
various ions, λex: 400 nm, slit width: 5 nm
2
+
2
2
Fig. 5 Time response of HTUN and HTUN/Hg . Solvents: MeCN/H O
2
+
(15/85, v/v), concentration: 10 μM for HTUN, 40 μM for Hg

J Fluoresc
2
2
1
800
100
400
2
1
100
400
2+
HTUN/Hg
7
00
0
7
00
HTUN
-
700
0
3.0
6.0
pH
9.0
12.0
0.0
0.3
2+
0.6
0.9
2+
[
Hg ]/([HTUN]+[Hg ])
Fig. 6 Effects of pH on the fluorescence maxima of HTUN and
2+
2+
Fig. 7 Job’s plot for Hg versus HTUN. Solvents: MeCN/H
2
O (15/
85,v/v), total concentration ([HTUN] + [Hg ]): 50 μM, F and F : the
maximal fluorescence intensity with and without Hg , respectively, λex
00 nm, slit width: 5 nm
HTUN/Hg . Solvents: MeCN/H
2
O (15/85, v/v), concentration: 10 μM
for HTUN, 40 μM for Hg , pH: 2.7, 3.5, 4.3, 5.5, 6.0, 7.5, 8.5, 9.0, 10.5,
1.0 and 12.5, λex: 400 nm, slit width: 5 nm
2+
2+
0
2+
:
1
4
2
+
The association constant for HTUN and Hg was obtained
from nonlinear fitting of the fluorescence titration data with
the UV-vis absorption spectra of HTUN were of little value to
the detection of metal ions.
Benesi-Hildebrand Eq. (1) [33]. Where I is the fluorescent
Then, the fluorescence response of HTUN (10 μM) to var-
ious metal ions (40 μM) was examined in the same medium.
As could be seen in Fig. 2, the fluorescence intensity of the
0
intensity of HTUN at 527 nm, I and I denote the values at a
max
2
+
certain concentration of Hg and at a complete-interaction
2
+
2+
2+
+
concentration of Hg . [Hg ] is the concentration of Hg ,
probe solution remained basically invariant when added Na ,
2
+
+
2+
2+
2+
2+
3+
3+
2+
2+
2+
n is the binding stoichiometry for Hg and HTUN, and Ks is
the association constant.
K , Ca , Mg , Mn , Co , Cr , Fe , Fe , Ni , Cu ,
2
+
2+
2+
Cd , Zn and Pb . However, a significant fluorescence en-
hancement accompanied by a green color emerged soon after
Hg was added into the system. The results implied the spe-
1
1
1
2+
¼
Â
à þ
ð1Þ
n
2þ
I−I0
KsðImax−I Þ Hg
Imax−I0
2+
0
cific selectivity of the probe towards Hg .
2
+
Fluorescence Titration with Hg
In order to investigate the possibility of HTUN used as a
Results and Discussion
Response of HTUN to Hg
2
+
fluorescent probe for Hg , titration experiment was done
and the results shown in Fig. 3. It could be seen that the
fluorescence intensity increased linearly with the concentra-
2
+
2
+
tion of Hg in the range of 18–40 μM with a correlation
The UV-vis absorption response of HTUN (10 μM) to various
metal ions (100 μM) was measured in MeCN/H O (15/85,
coefficient (R) of 0.99194 (Inset in Fig. 3), accompanied by
2
v/v) medium. The results were shown in Fig. 1, with the ad-
dition of different metal ions, the UV-vis absorption spectra of
2
400
2000
1
1
500
000
2
+
2+
2+
HTUN solutions exhibited some complicacy. Fe , Ni , Cu
5
2
+
and Pb made the UV-vis absorption spectra change obvious-
ly, but these changes mostly located in the ultraviolet region.
1800
5
00
0
+
+
2+
2+
4
2
3
Na , K , Ca and Mg induced spectral changes in the vis-
ible region, however, the changes were similar and small. So
1
200
6
00
0
2
+
Table 1 Recovery of Hg in pond water and tap water (n = 3)
1
2+
2+
Sample
Hg
Hg
Recovery /%
RSD /%
added /μM
found /μM
4
50
525
600
675
Pond water 1
Pond water 2
Tap water 1
Tap water 2
20
30
20
30
20.7
30.9
20.9
29.9
103.5
103
0.4
0.8
0.8
0.8
Wavelength /nm
2+
2+
Fig. 8 Fluorescence spectra of HTUN, HTUN/Hg and HTUN/Hg /
EDTA in MeCN/H O (15/85, v/v), concentration: 10 μM for HTUN,
40 μM for Hg , 40, 80 or 120 μM for EDTA. λex: 400 nm, slit width:
nm
104.5
99.7
2
2+
5

J Fluoresc
Scheme 2 Sensing mechanism
reported by Yan et al. (a) and
Mohammad et al. (b)
(
a)
(b)
enhanced green fluorescence. The detection limit evaluated
was superior to that of the HTUN solution under the same
−7
from this fluorescence titration was 1.38 × 10 mol/L. The
conditions in the pH range of 4.3–9.0, so HTUN could signal
2
+
2+
results show that HTUN can quantitatively trace Hg in
Hg over a wide pH range.
MeCN/H O (15/85, v/v).
2
2
+
Determination Hg in Spiked Environmental Water
Anti-Jamming Performance
2
+
We used HTUN to detect the concentration of Hg in spiked
tap water or pond water. The results were showed in Table 1,
+
In order to study the anti-interference ability of HTUN, Na ,
2
+
2+
2+
2+
+
2+
2+
2+
2+
3+
2+
Mg , Fe , Ca , Zn , K , Mn , Cd , Pb , Co and Cr
(
the found concentration of Hg was close to that of the added
Hg , the recovery is between 99.7 and 104.5% and the rela-
tive standard deviation (RSD) of three measurements less than
0.8%. These results showed that HTUN could be used to
2
+
3+
2+
2+
40 μM), Cu , Fe and Ni (20 μM) were added to the
2
+
MeCN/H O (15/85, v/v) solution of HTUN (10 μM)/Hg
2
(
40 μM) individually and the fluorescence spectra were re-
2
+
corded. As shown in Fig. 4, no significant fluorescence vari-
ation was detected upon adding the above ions. These results
indicated that HTUN exhibited high anti-jamming ability for
analysis of Hg in environmental water.
2+
the detection of Hg in MeCN/H O (15/85, v/v).
Sensing Mechanism
2
2
+
Time Dependence of the Detection
To understand the sensing mechanism of HTUN for Hg ,
Job’s plot experiment was conducted. The result was shown
in Fig. 7, the maximum of fluorescence enhancement reached
2
+
The time response of HTUN to Hg was investigated and the
2
+
2+
result was illustrated in Fig. 5. After the addition of Hg , the
fluorescence intensity of the solution increased rapidly, the
maximal fluorescent intensity was got at about 20 min after
when the mole fraction of Hg was 0.67, indicating a 1:2
2
+
stoichiometric ratio of HTUN to Hg , the binding constant
8
−2
evaluated by Benesi-Hildebrand method was 1.78 × 10 M .
To further research the sensing mechanism, we carried out
reversibility experiment. As shown in Fig. 8, HTUN solution
2
+
adding Hg , and then tended to be stable. While the fluores-
2
+
cence intensity of the HTUN solution without Hg was al-
most unchanged during the testing time. These results showed
that HTUN had a fast response to Hg .
emitted weak fluorescence in MeCN/H O (15/85, v/v) (line
1); after the addition of Hg , fluorescence intensity of the
2
2
+
2+
solution enhanced obviously (line 5); while 40 (line 2), 80
pH Dependence of the Detection
(line 3) and 120 μM (line 4) of EDTA half quenched the
2
+
fluorescence intensity of the HTUN/Hg solution. These re-
2
+
In order to study the practicability of HTUN in acid and alkali
media, the effects of pH on the fluorescence intensity of
sults indicated that the process of HTUN recognizing Hg
was partially reversible.
2
+
HTUN and HTUN/Hg were investigated. As shown in
Yan et al. [34] reported that the carbonyl oxygen and hy-
droxyl group of 1,8- naphthalimide could be combined with
2
+
Fig. 6, fluorescence intensity of the HTUN/Hg solution
Scheme 3 Sensing mechanism reported by Zhenyu et al.

J Fluoresc
Scheme 4 Proposed sensing
mechanism of HTUN for Hg
2+
3
+
1
Au to form a five-membered ring (Scheme 2a). Mohammad
et al. [35] disclosed that the carbonyl oxygen of 1,8-
To further validate the hypothetical mechanism, H NMR
2+
spectra of HTUN and HTUN/Hg were analyzed in DMSO-
d6, as shown in Fig. 10. Compared with HTUN, the peak at
10.11 ppm (j) corresponding to the NH in thiourea transferred
to 10.17 ppm and greatly weakened, the peak at 9.86 ppm (i)
assigned to the NH connected to the naphthalene ring almost
disappeared, these changes were consistent with the hypothesis
+
naphthalimide could be combined with Ag to form a six-
membered ring (Scheme 2b). Our team [36] found that thio-
urea structure could combine with Hg and then lose HgS to
form a three-membered ring (Scheme 3).
Taking into account of the partial reversibility and the 1:2
stoichiometric ratio of HTUN to Hg , as well as those report-
2
+
2
+
2+
that S atom combined with Hg and then HgS removed.
ed in the literature [34–36], we speculated that one of the two
Especially the emergence of a new peak at 1.65 ppm classified
as peak of H in NH indicated the formation of the three-
membered ring. Hydroxyl proton peak at 4.81 ppm (a) disap-
peared, and the proton peak (b) intensity of the ethylidene con-
nected to hydroxyl group was significantly decreased, which
suggested the complexation of O atom in hydroxyl with Hg .
Chemical shifts of H in benzene and naphthalene ring from
6.98–8.69 ppm moved to 6.95–8.88 ppm, accompanied by a
2
+
Hg ions was expectedly combined with the S atom in thio-
urea followed by irreversible cleavage of HgS to form a three-
2
+
membered ring, while the other Hg ion was reversibly
bound by the O atoms in hydroxyl and carbonyl beyond our
design, as shown in Scheme 4.
2+
In order to verify the binding mechanism of HTUN and
2
+
2+
Hg , HTUN/Hg solution was analyzed by mass spectrom-
etry (MS). As shown in Fig. 9, peaks at m/z 854.9561 and
2
+
+
8
2
31.3978 belonged to [HTUN + 2Hg +2Na ] and [HTUN +
2
+
+
Hg +Na ] respectively, which proved the 1:2 stoichiometry
ratio of HTUN and Hg . Peaks at m/z 675.6757, 516.7509
and 475.3473 corresponded to [HTUN’ + Hg +H O +
CH CN], [HTUN’ + K +Na +2CH CN] and [HTUN’ +
3 3
2
+
2
+
2
+
+
2
+
+
Na +K +CH CN] respectively. These results supported the
3
proposed mechanism.
675.6757
10000
516.7509
5000
475.3473
854.9561
831.3978
0
400
500
600
700
800
900
m/z
1
2+
Fig. 10 H NMR spectra of HTUN and HTUN/Hg in DMSO-d
6
2
+
Fig. 9 Mass spectrum of HTUN/Hg
(400 MHz)

J Fluoresc
7.
8.
9.
Liu WM, Chen JH, Xu LW, Wu JS, Xu HT, Zhang HY, Wang PF
increase of peak numbers and a decrease of the peak intensity,
these changes might be caused by the events of the complexing
2
+
(
2012) Reversible Boff-on^ fluorescent chemosensor for Hg
based on rhodamine derivative. Spectrochim. Acta Part A 85:38–42
2+
of Hg and HTUN as well as the following reactions.
Li M, Jiang YH, Zhang D, Ding PG, Wang ZJ, Ye Y, Zhao YF
1
2+
The analytical results of MS and H NMR spectra demon-
(2014) A novel colorimetric and off-on fluorescent sensor for Hg
2
+
and its application in live cell imaging. J Lumin 148:219–224
strate the recognition mechanism of HTUN to Hg .
Li XT, Yin Y, Deng JJ, Zhong HX, Tang J, Chen Z, Yang LT, Ma LJ
3
+
(
2016a) A solvent-dependent fluorescent detection method for Fe
2+
and Hg based on a rhodamine B derivative. Talanta 154:329–334
Conclusions
10. Tharmaraj V, Pitchumani K (2012) An acyclic, dansyl based color-
imetric and fluorescent chemosensor for Hg(II) via twisted intramo-
lecular charge transfer (TICT). Anal Chim Acta 751:171–175
In conclusion, a new fluorescent probe (HTUN) was success-
fully synthesized based on 1,8-naphthalimide, ethanol amine,
hydrazine hydrate and phenyl isothiocyanate. HTUN shows
high selectivity and high sensitivity to Hg over other metal
ions in MeCN/H O (15/85, v/v). In the Hg concentration
1
1. Kumar A, Kim HS (2015) N-(3-Imidazolyl)propyl dansylamide as
2
+
a selective Hg sensor in aqueous media through electron transfer.
Spectrochim. Acta Part A 148:250–254
2
+
12. Zhou S, Zhou ZQ, Zhao XX, Xiao YH, Xi G, Liu JT, Zhao BX
2+
(
2015) A dansyl based fluorescence chemosensor for Hg and its
2
+
2
application in the complicated environment samples. Spectrochim.
Acta Part A 148:348–354
range of 18–40 μM, the fluorescence intensity of the solution
2
+
increases linearly with the Hg concentration. The detection
13. Wang K, Yang LX, Zhao C, Ma HM (2013) 4-(8-Quinolyl)amino-
7-nitro-2,1,3-benzoxadiazole as a new colorimetric probe for rapid
2
+
−7
limit of Hg is 1.38 × 10 mol/L. HTUN can be used in the
2
+
and visual detection of Hg . Spectrochim. Acta Part A 105:29–33
range pH 4.3–9.0, and has a fast response and a strong anti-
interference. HTUN can effectively detect Hg in pond water
and tap water. HTUN combines with Hg at a 1:2 M ratio and
the binding constant is 1.78 × 10 M . One of the two Hg
ions is expectedly bound by the sulfur atom in the thiourea
unit of HTUN and followed by the irreversible reaction of
removing HgS, and another Hg is unexpectedly combined
with hydroxyl and carbonyl oxygen atoms in the imide side of
HTUN reversibly. In addition, the aliphatic hydroxy at imide
side affords HTUN’s reactivity which can be used for self-
modification or modifying other materials.
1
4. Chebrolu LD, Thurakkal S, Balaraman HS, Danaboyina R (2014)
2
+
2+
2+
Selective and dual naked eye detection of Cu and Hg ions using
a simple quinoline-carbaldehyde chemosensor. Sens. Actuators B
204:480–488
2
+
8
−2
2+
1
5. Ma WH, Xu Q, Du JJ, Song B, Peng XJ, Wang Z, Li GD, Wang XF
2+
(2010) A Hg -selective chemodosimeter based on desulfurization
of coumarin thiosemicarbazide in aqueous media. Spectrochim.
Acta Part A 76:248–252
2
+
1
1
1
6. Yu SY, Wu SP (2014) A highly selective turn-on fluorescence
chemosensor for Hg(II) and its application in living cell imaging.
Sens. Actuators B 201:25–30
7. Kao SL, Wu SP (2015) A fluorescent turn-on probe for Hg(II)
2
based on an NTe chelating motif and its application in living cell
imaging. Sens. Actuators B 212:382–388
8. He T, Lin CL, Gu ZY, Xu LN, Yang AL, Liu YY, Fang HJ, Qiu HY,
Zhang J, Yin SC (2016) Sensing behavior and logic operation of a
Acknowledgements This work was supported by the National Natural
Science Foundation of China (21074085), the Priority Academic
Program Development of Jiangsu Higher Education Institutions, and
the State and Local Joint Engineering Laboratory for Novel Functional
Polymeric Materials.
2+
2+
colorimetric fluorescence sensor for Hg /Cu ions. Spectrochim.
Acta Part A 167:66–71
19. Shen W, Wang L, Wu M, Bao XF (2016) A fluorescein derivative
2+
+
FLTC as a chemosensor for Hg and Ag and its application in
living-cell imaging. Inorganic Chem Commun 70:107–110
2
0. Piyanuch P, Watpathomsub S, Lee VS, Nienaber HA,
2+
Wanichacheva N (2016) Highly sensitive and selective Hg
-
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