Selective fluorometric “Turn-off” sensing for Hg2+ with pyrazoline compound and its application in real water sample analysis

Article abstract of DOI:10.1016/j.ica.2019.119288

In this study, a new pyrazoline derivative (4-(3-phenyl-3a,4-dihydroindeno[1,2-c]pyrazol-2(3H)-yl)benzenesulfonamide, K1) was described as fluorescent probe for fluorometric detection of Hg²⁺. This fluorescence probe had a high selectivity only

Full text of DOI:10.1016/j.ica.2019.119288

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Research paper
Selective fluorometric “Turn-off” sensing for Hg2+ with pyrazoline compound
and its application in real water sample analysis
Ebru Bozkurt, Halise Inci Gul
PII:
S0020-1693(19)31355-6
https://doi.org/10.1016/j.ica.2019.119288
ICA 119288
DOI:
Reference:
Inorganica Chimica Acta
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5 September 2019
15 November 2019
15 November 2019
Please cite this article as: E. Bozkurt, H.I. Gul, Selective fluorometric “Turn-off” sensing for Hg2+ with pyrazoline
compound and its application in real water sample analysis, Inorganica Chimica Acta (2019), doi: https://doi.org/
10.1016/j.ica.2019.119288
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Selective fluorometric “Turn-off” sensing for Hg2+ with pyrazoline
compound and its application in real water sample analysis
Ebru Bozkurta* and Halise Inci Gulb
aProgram of Occupational Health and Safety, Erzurum Vocational Training School, Ataturk
University, 25240 Erzurum, Turkey
bDepartment of Pharmaceutical Chemistry, Faculty of Pharmacy, Ataturk University, 25240
Erzurum, Turkey
*Corresponding Author. Tel: +90(442)231 2667; Fax #: +90(442)231 2503
e-mail: ebrubozkurt@atauni.edu.tr (Ebru Bozkurt)
1

Abstract
In this study, a new pyrazoline derivative (4-(3-phenyl-3a,4-dihydroindeno[1,2-
c]pyrazol-2(3H)-yl)benzenesulfonamide, K1) was described as fluorescent probe for
fluorometric detection of Hg2+. This fluorescence probe had a high selectivity only toward Hg2+
ion in the 19 metal ions (Li+, Na+, K+, Ag+, Mg2+, Ca2+, Ba2+, Cd2+, Zn2+, Cu2+, Hg2+, Cr2+, Pb2+,
Fe2+, Mn2+, Co2+, Fe3+, Al3+ and Cr3+). It was observed that Hg2+ ions significantly decrease the
fluorescence intensity of K1, but the fluorescence intensity of K1 did not changed in the
presence of the other metal ions. Limit of detection (LOD) value was calculated as 0.16 µM for
Hg2+ while the binding constant was calculated as 4.69x105 M-2 via fluorescence measurements.
The values obtained by this study were very good compared to our previous Hg2+ sensor study
which was realized with a different pyrazoline compound. The interaction between of K1 and
Hg2+was not interfered by the presence of other metal ions. In addition, the type of interaction
was reversible. It was found that the relative standard deviations (RSD) of three measurements
were less than 15% with the real sample tests performed in the tap water and its response time
was less than 0.5 min. In conclusion, the new pyrazoline derivative K1 is a highly selective and
sensitive fluorescence probe for the detection of Hg2+ ion and it has a great chance for practical
application.
Keywords: Pyrazoline; Fluorometric; Turn off; Hg2+ ions.
2

1. Introduction
Detection of heavy metal ions is very important since they cause serious damage to the
environment and human health. Mercury is one of the most toxic and polluting heavy metal
used in many industrial products such as batteries, paints and electrical equipment. Therefore,
it causes pollution in the atmosphere and surface waters. As a result, it has serious damage to
the central nervous system and endocrine system in human through the food chain [1]. So,
selective and sensitive detection studies for Hg2+ are quite important.
In recent years, the detection of Hg2+ ions by using new fluorescence probes is a very
popular research area since fluorometric detection is a very sensitive, low-costly method in
addition to getting the response quickly and compared to traditional methods such as high-
performance liquid chromatography (HPLC), inductively coupled plasma mass spectrometry
(ICP-MS) and atomic absorption/emission spectrometry (AAS/AES) [2]. Organic dyes such as
rhodamine, fluorescein and coumarin derivatives are fluorescence probes commonly used in
detection of Hg2+ ions [3-5]. So, it is an attractive and important field development of new
fluorometric sensors for the detection of Hg2+ ion.
Pyrazoline derivatives are among the outstanding compounds since they are non-toxic
bioactive compounds in addition to their strong fluorescence properties. Therefore, these
compounds have widely been used as fluorometric ion sensor [6], hole-transport material in
optoelectronic applications [7]. They are also interesting and attractive pharma core in
medicinal chemistry since they have wide range of bioactivities such as anticancer and carbonic
anhydrase inhibiting properties [8-10]. In recent years, ion detection studies with pyrazoline
derivatives have become widespread due to their high selectivity and sensitivity [11].
In the present study, we have been investigated the effects of nineteen metal ions (Li+,
Na+, K+, Ag+, Mg2+, Ca2+, Ba2+, Cd2+, Zn2+, Cu2+, Hg2+, Cr2+, Pb2+, Fe2+, Mn2+, Co2+, Fe3+, Al3+
and Cr3+) on the absorption and fluorescence properties of the novel pyrazoline derivative
compound K1 having the chemical structure 4-(3-phenyl-3a,4-dihydroindeno[1,2-c]pyrazol-
3

2(3H)-yl)benzenesulfonamide by using UV-Vis absorption and steady-state fluorescence
measurements. These obtained results presented that K1 is a sensor with high selectivity and
sensitivity for the detection of Hg2+ compared to the other relevant metal ions. Real sample test
realized for the possibility application of K1 to determine practical use.
2. Experimental
2.1. Materials
Ethanol and LiCl, NaCl, AgCH3COO, MgCl2.6H2O, CaCl2.2H2O, BaCl2.2H2O, CdCl2,
ZnCl2.H2O, CuCl2.2H2O, HgCl2, CrCl2, Pb(CH3COOH)2.3H2O, FeSO4.7H2O, MnCl2.4H2O,
CoCl2.6H2O, FeCl3, AlCl3 and CrCl3 as the metal ion sources and ethylene diamine tetra acetic
acid (EDTA) were obtained from Sigma and pH buffer solutions purchased from Fluka. Stock
solution of freshly synthesized [12] and prepared K1 was solved in ethanol at 1.0x10-3 M.
Certain amount of K1 in aqueous solution was made ready from its stock solution by
evaporating ethanol. For all measurements, the final concentration of K1 was 10 µM. All the
experiments were performed at room temperature.
2.2. Apparatus
1
For K1, H and 13C NMR spectra were recorded on Varian 400 and Bruker 400
instruments in DMSO-d6. UV-Vis absorption and fluorescence spectra of K1 were recorded
with Perkin Elmer Lambda 35 UV/VIS Spectrophotometer and Shimadzu RF-5301PC
spectrofluorophotometer, respectively. For the steady-state fluorescence measurements, sample
solutions were excited at 350 nm and fluorescence intensities were recorded between 360 nm
and 650 nm. FTIR measurements of the samples of K1 were recorded with Vertex 80/80v FTIR
spectrometer [13].
4

Fluorescence quantum yields of samples were calculated by using Parker-Rees equation.
2
−푂퐷
푟
퐷
휂
1−10
1−10
푆
푠
∅푠 = ∅푟 ( ) ( ) (
)
(1)
2
−푂퐷
푠
퐷
푟
휂
푟
where D is the integrated area under the corrected fluorescence spectrum, n is the refractive
index of the solution, and OD is the optical density at the excitation wavelength (λexc= 350 nm).
The subscripts s and r refer to the sample and reference solutions, respectively [14]. Quinine
sulphate in 0.5 M H2SO4 solution was used as the reference. The fluorescence quantum yield
of quinine sulphate is 0.54 in 0.5 M H2SO4 solution [15].
2.3. Synthesis
of
4–(3-Phenyl)-3a,4-dihydro-3H-indeno[1,2-c]pyrazol-2-yl)
benzenesulfonamide (K1)
The compound K1 was synthesized and characterized as described in our previous study
[12]. The synthesis of the compound K1 has been summarized in Scheme 1. Briefly, aqueous
solution of sodium hydroxide (10% w/v, 10 mL) was added into the ethanol (6 mL) solution of
1-indanone (20 mmol) and benzaldehyde (20 mmol). Then, to obtain the starting compound
chalcone the mixture was stirred overnight at room temperature and then it was poured on ice-
water (100 mL) in the beaker. The mixture was neutralized with hydrochloric acid (10% w/v,
10 mL). The colored precipitate formed was filtered and crystallized from water ethanol to
1
obtain chalcone compound 1. Chemical structure of the compound 1 was confirmed by H
NMR, 13C NMR, HRMS and the literature reported melting points of the compound. Data are
not presented here. The solution of 2–(benzylidene)-2,3-dihydro-1H-inden-1-one (1, 1.00
mmol) and 4-hydrazinobenzensulfonamide hydrochloride (1.10 mmol) in ethanol (50 mL) was
heated (100⁰C, 200 Watt, 3 barr, 20 min). Reaction was monitored by TLC. When the reaction
was stopped, the volume of the reaction mixture was concentrated to the half and the precipitate
5

formed was filtered, washed with cold ethanol, and dried. Then compound was purified by
crystallization from ethanol to obtain K1. Chemical structure of the compound K1 was
13
1
confirmed by 1H NMR, C NMR, and HRMS. M.p. 243–246⁰C. Yield: 8.4% H NMR (400
MHz, CDCl3 , ppm) δ 7.76 (d, 1H, Ar-H, J=8.4 Hz), 7.67 (d, 2H, Ar-H, J=9.1 Hz), 7.34–7.19
(m, 6H, Ar-H), 7.03 (bs, 4H, Ar-H), 5.59 (d, 1H, C3 -H, J=10.9 Hz), 4.28–4.21 (m, 1H, C3a -
13
H), 2.91 (dd, 1H, C4 -Ha, J=15.9, 8.7 Hz), 2.17 (dd, 1H, C4 -Hb, J=15.9, 7.6 Hz); C
NMR (100 MHz, CDCl3 , ppm) δ 163.9, 151.7, 148.1, 134.3, 131.0, 130.7, 129.8, 128.9,
128.4, 128.3, 127.9, 127.3, 126.6, 122.9, 112.5, 67.5, 55.2, 29.9; Mass spectrum: 390.12
(M+ +1); HRMS (ESI-MS) Calc.: 390.1276 for C22 H20 N3 O2 S [M+H]+ , found: 390.1281.
2.4. The sensing of metal ion
1.0x10-2 M stock solutions of all metal ions (Li+, Na+, K+, Ag+, Mg2+, Ca2+, Ba2+, Cd2+,
Zn2+, Cu2+, Hg2+, Cr2+, Pb2+, Fe2+, Mn2+, Co2+, Fe3+, Al3+ and Cr3+) were prepared in pure water.
Then, 10 µL of metal ion solution was added to 5 ml water solution of K1 having 10 μM
concentration at room temperature. The spectroscopic changes of K1 were recorded by
absorption and fluorescence measurements. In addition, special series of water solutions of Hg2+
ion with different concentrations (0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 4.0, 6.0, 8.0, 10,
20, 30, and 40 µM) were also prepared since only Hg2+ decreased the fluorescence intensity of
K1 among 19 metal ions. The absorption and fluorescence measurements were taken for each
solution containing Hg2+ ions. The detection limit for Hg2+ was determined with the
fluorescence data. For this purpose, 3s/k equation was used. Where s is the standard deviation
of blank, k is the slope of the fit line in fluorescence titration experiment. Moreover, the
following Benesi-Hildebrand equation was used to calculate the binding constant:
1
1
1
=
+
(2)
+ 푛
퐹−퐹
퐾 (퐹
−퐹 )[푀 ]
퐹
−퐹
0
퐴
푚푎푥
0
푚푎푥 0
6

where F0, F, and Fmax are the fluorescent intensity of molecule in which F0 is in the absence of
metal ion, F is at a certain concentration of metal ion, Fmax is at a complete interaction
concentration of metal ion. [M+] is the concentration of Hg2+, n is the binding stoichiometry for
dye and metal ion [16].
2.5. Testing real sample
Tap water was used for real sample tests. After filtration, 2.5 ml of tap water was put
into 5 ml volumetric flask containing 10 μM K1. Then 5 μl, 10 μl and 15 μl stock solutions of
Hg2+ were added on K1 solution. The mixture was diluted to 5 ml with distilled water and the
fluorescence spectra were recorded between 360 nm and 650 nm at 350 nm excitation
wavelength.
3. Result and Discussion
3.1. The photo-physical behavior of K1 and the effect of metal ions
The K1 studied here was synthesized according to literature procedure [12] and it was
summarized in Scheme 1.
The optical behavior of the K1 in water was determined by taking UV-Vis absorption
and fluorescence spectra (Fig. 1). The K1 exhibited two absorption bands at 278 nm and 363
nm and relatively high intensity fluorescence band at 464 nm (Fig. 1).
The effects of several alkali, alkaline-earth and heavy/transition metal ions (Li+, Na+,
K+, Ag+, Mg2+, Ca2+, Ba2+, Cd2+, Zn2+, Cu2+, Hg2+, Cr2+, Pb2+, Fe2+, Mn2+, Co2+, Fe3+, Al3+, and
Cr3+) on the optical properties of the K1 were studied. For this, solutions containing 20 μM
metal ions were added into the K1 (10 μM) aqueous solution. Then, at room temperature
absorption and fluorescence measurements were taken for the solutions mentioned above. It
was observed that the absorption spectrum of the K1 did not changed in the presence of the
metal ions (Fig. 2). However, the fluorescence intensity of K1 significantly decreased only in
7

the presence of Hg2+ ion (Fig. 3a). As shown in Fig. 3b, the color of the solution changed in the
presence of Hg2+ ion, while other metal ions did not cause a significant change in solution color.
The fluorescence quantum yields of K1 in the presence and absence of metal ions were
calculated by using Eq. (1) (Table 1). The calculated fluorescence quantum yield value of K1
in the presence of Hg2+ ion was 0.05. This value was 8.6 times smaller than the value in pure
water. This reduction in the quantum yield of K1 supported that Hg2+ reduced the fluorescence
intensity of K1. The calculated fluorescence quantum yield values of the K1 in the presence of
other metal ions rather than Hg2+ were almost the same with the value of K1 in pure water
(0.43).
3.2. Detection of Hg2+ by using K1
In order to detect mercury ions, the fluorescence intensity of K1 (10 µM) was
determined in the presence of Hg2+ ions in different concentrations (0-40 µM) (Fig. 4). As
shown in Fig. 4, while the fluorescence band maximum (λmax) was not changed compared to
pure water’s (464 nm); the fluorescence intensity of K1 decreased as Hg2+ ion concentration
increased. This finding was in accordance with the literature [2, 17]. The linear relationship
between the fluorescence intensity of K1 and the Hg2+ ion concentration was presented in Fig.
5. The detection limit (LOD) of Hg2+ was determined as 0.16 µM by using Fig. 5. LOD value
was very low in the present study compared to our previous Hg2+ sensor study which was
realized with a different pyrazoline compound [11]. Having low LOD value is a very good
parameter for the development of fluorescence sensor.
Job's plot analysis was used to determine the stoichiometry of interaction between K1
and Hg2+. The interaction ratio between K1 and Hg2+ was found as 2:1 according to the results
obtained (Fig. 6). The binding constant of Hg2+ was calculated as 4.69x105 M-2 with the slope
of graph which was drawn using Eq. (2). This value is greater than the Hg2+ sensor studies in
the literature [18, 19]. This is also good parameter for this type of fluorescence sensor studies.
8

This value was also higher than our previous report obtained with a different pyrazoline
compound [12].
Competition studies were carried out to determine the selectivity of K1 against Hg2+.
For this purpose, fluorescence measurements of K1 solutions were taken by adding Hg2+ ion in
the presence of competitive metal ions (Li+, Na+, K+, Ag+, Mg2+, Ca2+, Ba2+, Cd2+, Zn2+, Cu2+,
Cr2+, Pb2+, Fe2+, Mn2+, Co2+, Fe3+, Al3+ and Cr3+). As seen in Fig. 8, the presence of competitive
ions in the medium did not affect the selectivity of K1 to Hg2+ ion. This is a very good result
for the selective detection of Hg2+ ion without interaction with other ions.
Reversible behavior is a preferable property for the fluorescence sensors. Reversible
behavior of K1 against Hg2+ ion was investigated by fluorescence measurements using EDTA.
When EDTA was added to the K1 solution in the presence of Hg2+ ion, it was observed that K1
could return to the fluorescence intensity in the absence of Hg2+ (Fig. 9). This result showed
that K1 was a sensor with recycling capability via Hg2+ “OFF” and EDTA “ON” system. It
means that K1 is a reversible fluorescence sensor.
Shortness of response time (SRT) of a sensor is one of the important features that was
desired. So, the change in the interaction of K1 and Hg2+ ion with time was evaluated (Fig. 10).
It was found that the fluorescence intensity of K1 decreased within 0.5 minute (min) and then
remained fixed from 1 min to 10 min. The rapid and stable response of K1 to Hg2+ ion is a very
important result for the detection of Hg2+ ion in fluorescence sensor studies. Although, SRT is
an important parameter, it was not considered in studies in this area [20-22]. So, this study
makes a valuable contribution to the fluorescence sensor studies by this respect.
3.3. pH profiles of K1
The effect pH on the Hg2+ detection with K1 was evaluated at different pH values (pH
2-12) by taken fluorescence spectra (Fig. 11). As shown in Fig. 11, the fluorescence intensity
9

of K1 decreased in the presence of Hg2+ ions in the pH range of 7-12. This result shows that
this new sensor can be used for neutral water samples and biological applications at
physiological pH.
3.4. Hg2+ ion sensing mechanism
FTIR measurements were used to determine the interaction between K1 and Hg2+. The
FTIR spectra for K1 (black color, Fig. 12) and K1+Hg2+ (red color, Fig. 12) were given in Fig.
12. According to Fig. 12, the K1 gave the peaks at 1310 (C-N stretching vibration), 1429 (C-C
stretching vibration), 1736 (C=N stretching vibration), 2915 (C-H stretching vibration), and
3439 (N-H stretching vibration) cm-1. In the presence of Hg2+, the peaks at 1310 (C-N stretching
vibration) and 3439 (N-H stretching vibration) cm-1 disappeared. This suggested that the
decrease in fluorescence intensity of K1 was due to electrostatic interactions between K1 and
Hg2+ ions. The proposed interaction mechanism for K1 and Hg2+ was shown in Scheme 2.
1
To determine the interaction mode of Hg2+ metal ions with K1, H NMR titration was
1
also performed in the absence and presence of Hg2+ in DMSO-d6 (Fig. 13). According to H
NMR of the K1 without Hg2+, proton signals of SO2NH2 group was seen at 7.00 ppm as a
singlet. With increasing amount of Hg2+, the appearance of the proton signals of the SO2NH2
changed. It was observed that proton of the SO2NH2 group of the K1 and shifted to upfield and
its shape changed to a broad singlet from sharp singlet while its intensity was decreasing. This
supports suggested the interaction mechanism of the K1 with Hg2+ (Scheme 2) by FTIR.
3.5. Real sample tests
The real sample performance of our novel sensor K1 was investigated. In our
experimental design for this purpose it was used tap water and pure water mixture in 1:1 volume
ratio. Three K1 solutions at 10 µM were prepared by using this water mixture. After that 10
μM, 20 μM and 30 μM Hg2+ ions were added into K1 solutions which have constant
10

concentration as 10 µM. then the fluorescence measurements were taken and the results were
presented in Table 2. Hg2+ concentrations were detected as 7.3 μM, 21.9 μM and 29.5 μM for
10 μM, 20 μM and 30 μM Hg2+ solutions, respectively. The relative standard deviation (RSD)
of three measurements was less than 15%. Recovery was between 72.7% and 109.6%. These
results are quite satisfactory for the analytical applications of K1.
3.6. Comparison with other Hg2+ sensors
The comparison of the fluorescent sensor K1 used in our study with other Hg2+ sensors
in the literature were given in Table-3. The value of the detection limit obtained in this study
was found to be significantly better than many studies in literature and also our previous study’s
[1, 2, 11, 22-29].
4. Conclusions
In this study, the ability of new pyrazoline derivative K1 to be a metal ion sensor was
investigated. Based on this target, the effects of 19 different metal ions on the optical behavior
of K1 were studied in pure water by using UV-Vis absorption and steady-state fluorescence
measurements. The fluorescence intensity of K1 only changed significantly in the presence of
Hg2+ ion, while other metal ions had no effect on the absorption spectrum of K1. So, the next
part of our studies was continued with Hg2+ ion. The LOD value for Hg2+ ion was calculated as
0.16 µM using the linear reduction of fluorescence intensity of K1 depending on increasing
concentrations of Hg2+ ion. This value was found to be quite low compared to many other
studies reported including in our previous study. Interaction ratio of K1 and Hg2+ was
determined as 2:1 by Job's method. The interaction between of K1 and Hg2+ did not interfere
from the presence of other metal ions and the type of interaction was reversible. The interaction
mechanism of Hg2+ with K1 was estimated with the FT-IR measurements. Real sample
experiments were performed in tap water for possible practical application of K1.
11

In conclusion, the new pyrazoline derivative K1 is a highly selective and sensitive
fluorescence probe for the detection of Hg2+ ion and it has a great chance for practical
application.
Acknowledgment
The authors thank to Dr. Mehtap Tugrak for kind contributions during synthesis and NMR
studies of compound.
12

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FIGURE and SCHEME CAPTIONS
Scheme 1. The general synthesis and molecular structure of K1.
Fig. 1. Absorption and fluorescence spectra of K1 in water (λexc=350 nm).
Fig. 2. Absorption spectra of K1 in the absence and presence of 20 µM metal ions in water.
Fig. 3. (a) Fluorescence spectra of K1 in the absence and presence of 20 µM metal ions in water
(λexc=350 nm). (b) Photographs of K1 in the presence of metal ions under UV. B; includes only
K1 while the others contain K1 and a metal ion.
Fig. 4. Fluorescence spectra of K1 with the increasing concentration of Hg2+ (λexc=350 nm).
Fig. 5. Change fluorescence intensity of K1 with the increasing concentration of Hg2+.
Fig. 6. Job’s plot of K1 with Hg2+ in water.
Fig. 7. Benesi-Hildebrand plot based on a 1:2 association stoichiometry between Hg2+and K1.
Fig. 8. Metal ion selectivity profiles of K1 in the presence of various metal ions in water. Red
bars represent the fluorescence intensity of K1 in the presence of 20 µM of metal ion. Blue
bars represent the fluorescence intensity in the presence of various metal ions after the
addition of Hg2+.
Fig. 9. Fluorescence spectra of K1 in the presence of 20 µM Hg2+ ion and EDTA in water
(λexc=350 nm).
Fig. 10. Fluorescence enhancing profile of addition Hg2+ (20 µM) to K1 (10 µM) in water from
0.5 min to 10 min.
Fig. 11. Fluorescence (at 464 nm) of K1 (10 µM) and K1 (10 μM) + Hg2+ (20 µM) at different
pH (2-12).
Fig. 12. FTIR spectra of K1 and Hg2+
Scheme 2. The proposed mechanism of interaction between K1 and Hg2+
Fig. 13. 1H NMR spectra of K1 (10 µM); K1 (10 µM) + Hg2+ (20 µM) in DMSO-d6
14

Reagents and conditions.
(i) aq. NaOH 10%, EtOH, r.t, 12 h; (ii) 4-
hydrazinobenzensulfonamide hydrochloride, EtOH, 100 ºC, 200 Watt, 3 barr, 20'.
Scheme 1.
Fig. 1.
15

Fig. 2.
Fig. 3a.
Fig. 3b.
16

Fig. 4.
Fig. 5.
17

Fig. 6.
Fig. 7.
18

Fig. 8.
Fig. 9.
19

Fig. 10.
Fig. 11.
20

Fig. 12.
Scheme 2.
21

Fig. 13
22

TABLES
Table 1. The fluorescence quantum yield values of K1 in the absence and presence of 20 µM
metal ions in water.
Table 2. Determination of Hg2+contents in tap water samples (n=3).
Table 3. Comparison of some Hg2+ selective chemosensors.
23

Table 1.
Media
Φf
Media
Cu2+
Φf
Pure water
0.43
0.25
Na+
Li+
Hg2+
Cr2+
Pb2+
Fe2+
Mn2+
Co2+
Fe3+
Al3+
0.33
0.33
0.31
0.32
0.31
0.31
0.31
0.32
0.35
0.05
0.28
0.28
0.21
0.22
0.31
0.21
0.27
0.30
K+
Ag+
Mg2+
Ca2+
Ba2+
Cd2+
Zn2+
Cr3+
Table 2.
Hg2+ spiked
Hg2+ found
(µM)
7.3
Samples
Recovery (%) RSD (%)
(µM)
10
20
72.7
109.6
98.3
11.0
5.6
2.1
1
2
3
21.9
29.5
30
24

Table 3.
Ref
Binding
Constant
(M-1)
Detection
Limit
(µM)
Response
Time
(min)
-
Sensing
Ions
4.19 × 105
0.18
Hg2+
Hg2+
[1]
[2]
-
0.50
-
[11]
(Our previous work)
[22]
8.06x104
14.54
Hg2+
1.0
3.00x109
2.5 × 104
4.71 × 10−10
-
0.39
2.00
0.33
1.21
10.00ꢀ
0.53
1.84
Hg2+
Ag+, Hg2+
Hg2+
Hg2+, I-
Hg2+
Cu2+,Hg2+
Cu2+,Hg2+
-
-
-
-
-
-
-
[24]
[25]
[26]
[27]
[28]
[29]
M
1.7ꢀ×ꢀ104
-
1.61ꢀ×ꢀ104
K1
(This work)
4.69x105 M-2
0.16
Hg2+
0.5
25

Highlights
 A new pyrazoline derivative (K1) was synthesized for Hg2+ ion sensing based on
fluorometric detection.
 The possibility of practical uses of K1 as selective fluorometric “turn-off” was reported.

K1 seemed a highly selective and sensitive fluorescence probe for the detection of Hg2+
ion.
26

GRAPHICAL ABSTRACT
27