A sensitive OFF-ON-OFF fluorescent probe for the cascade sensing of Al3+and F?ions in aqueous media and living cells

Article abstract of DOI:10.1039/d0ra02848g

A simple Schiff-base ligand 2-hydroxy-1-naphthaldehyde semicarbazone (HNS) was synthesized and characterized. Based on the combined effect of inhibition of CH-N isomerization and chelation-enhanced fluorescence (CHEF),HNSfunctions as a fluorescence “turn on” sensor for Al³⁺in buffered aqueous media. Based on the strong affinity of Al³⁺to F^?ions, thein situgenerated Al³⁺-HNScomplex can also be utilized as an effective chemosensor for F^?sensing by metal displacement approach, ensuing quenching of fluorescence by the reversible return ofHNSfrom Al³⁺-HNScomplex. Thus a method using a single probe for the detection of both Al³⁺and F^?ions is developed. The system exhibits high selectivity and sensitivity for Al³⁺and F^?ions and the detection limits were found to be as low as 6.75 × 10^?8M and 7.89 × 10^?7M, respectively. Furthermore, the practical applicability of this probe has been examined in living cells.

Full text of DOI:10.1039/d0ra02848g

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PAPER
A sensitive OFF–ON–OFF fluorescent probe for the
cascade sensing of Al3+ and Fꢀ ions in aqueous
media and living cells†
Cite this: RSC Adv., 2020, 10, 21629
b
Lingjie Hou,ac Wenting Liang,
Shaomin Shuang
Chenhua Deng,ac Caifeng Zhang,ac Bo Liu,d
*
b
b
*
and Yu Wang
A simple Schiff-base ligand 2-hydroxy-1-naphthaldehyde semicarbazone (HNS) was synthesized and
characterized. Based on the combined effect of inhibition of CH]N isomerization and chelation-
enhanced fluorescence (CHEF), HNS functions as a fluorescence “turn on” sensor for Al3+ in buffered
aqueous media. Based on the strong affinity of Al3+ to Fꢀ ions, the in situ generated Al3+–HNS complex
can also be utilized as an effective chemosensor for Fꢀ sensing by metal displacement approach,
ensuing quenching of fluorescence by the reversible return of HNS from Al3+–HNS complex. Thus
a method using a single probe for the detection of both Al3+ and Fꢀ ions is developed. The system
exhibits high selectivity and sensitivity for Al3+ and Fꢀ ions and the detection limits were found to be as
low as 6.75 ꢁ 10ꢀ8 M and 7.89 ꢁ 10ꢀ7 M, respectively. Furthermore, the practical applicability of this
probe has been examined in living cells.
Received 28th March 2020
Accepted 26th May 2020
DOI: 10.1039/d0ra02848g
rsc.li/rsc-advances
uorescent probes for Al3+ contain nitrogen–oxygen-rich coor-
dination environments which provide a hard-base environment
for the hard-acid Al3+. These probes, however, have some limi-
tations such as poor water solubility and tedious synthetic
procedure, which limited their practical applications. Thus,
only few examples of Al3+ probes can be used for cell imaging
and biological samples.5,8,9,12–15 Overall, it is still highly desirable
to develop novel uorescent probes for Al3+ which satises
several parameters viz. easy and economical synthetic proce-
dure, moderate water solubility and being suitable for cell
imaging studies.
Moderate uoride for human has good performance in the
treatment of osteoporosis and the prevention of dental caries.
However, excess presence of for human body may lead to dental
uorosis, skeletal uorosis, osteoporosis, and osteosclerosis.20
Thus, the development of an efficient Fꢀ uorescent sensor is
1. Introduction
Aluminum is the most abundant metal in the Earth's crust and
is extensively used in every sphere of life from utensils to
medicine. But aluminum in excessive amounts not only
hampers plant growth but damages the human nervous system
and has been reported to induce Alzheimer's disease, Parkin-
son's disease and amyotrophic lateral sclerosis, etc.1 Therefore,
detection of Al3+ ions in natural environment and living
organisms is of vital importance for human health. In this
context, the development of uorescence based probes attrac-
ted more attention because of the simplicity and high sensitivity
of uorescence assays. However, the lack of spectroscopic
characteristics and poor coordination ability of Al3+ (ref. 2)
make it very challenging to develop a highly selective sensing
system for Al3+
.
quite important.21–23 Interestingly, emissive probꢀe
+
Al3+
Up to now, several uorescent probes for Al3+ have been
complexes can serve as anion sensors, especially to F .24–29 And
these sensors that are capable of detecting Al3+ and Fꢀ sequen-
tially by uorescence OFF–ON–OFF signaling response are highly
effective when compared with the one-to-one probes.30–32
designed by various workers.3–19 And the structures of most
aDepartment of Chemistry, Taiyuan Normal University, Jinzhong 030619, P. R. China
bDepartment of Chemistry, Institute of Environmental Science, Shanxi University,
Taiyuan 030006, P. R. China. E-mail: liangwt@sxu.edu.cn; wangyu1168@sxu.edu.cn
cHumic Acid Engineering and Technology Research Center of Shanxi Province, Jinzhong
030619, P. R. China
dNational Institutes for Food and Drug Control, Beijing 100050, P. R. of China
† Electronic supplementary information (ESI) available: 1H NMR spectrum, 13C
NMR spectrum and HRMS spectrum of HNS. Job's plot for HNS and Al3+
complexation in EtOH/H2O. Benesi–Hildebrand plot from uorescence titration
data of HNS with Al3+. FTIR spectra of HNS and Al3+–HNS complex. 1H NMR
spectrum, 13C NMR spectrum, and HRMS spectrum of Al3+–HNS complex aer
adding Fꢀ. See DOI: 10.1039/d0ra02848g
With these considerations in mind, we herein report an
easily synthesizable Schiff base receptor 2-hydroxy-1-
naphthaldehyde semicarbazone (HNS), which commendably
supports the idea of the sequential sensing property for Al3+ and
Fꢀ in aqueous media and live cells. 2-Hydroxynaphthalene was
selected as a signaling moiety for its low uorescence quantum
yield,33 short uorescence lifetime,34 good binding sites and low
cost. The binding of Al3+ with the phenolic –OH group and
Schiff base nitrogen atoms of HNS would inhibit the cis–trans
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isomerization around C]N and increase the rigidity of the 8 mL of ethanol. The solution was neutralized to pH 7.0 with
molecular assembly to produce signicant uorescence 1.0 M of NaOH and then was mixed with the ethanol solution of
enhancement, which shows a selective sensing property for Al3+ 2-hydroxy-1-naphthaldehyde (200 mg, 1.16 mmol). The mixture
in buffered aqueous media. Further, the formed Al3+–HNS was heated under reux for 4 h and then cooled to room
complex can be utilized for the sensitive detecting of uoride temperature. Saturated sodium chloride solution was added
owing to the strong binding affinity of Al3+ for Fꢀ ions.35 Hence, dropwise and the precipitated solid was ltered off, washed with
the gradual addition of Fꢀ ions into a mixture of HNS and Al3+ cold water and dried under vacuum and recrystallized from
ions releases HNS, and shows uorescence quenching. Thus, ethanol to give the product as a light-yellow solid (170 mg, 64%
a single-probe sensory system was developed to detect both Al3+ yield). IR nmax (KBr): 3450, 3350, 1670, 1602, 1431, 1189 cmꢀ1. 1H
cation and Fꢀ anion with good detection reversibility, which NMR (DMSO-d6) d: 6.37 (s, 2H, NH2), 7.20 (d, 1H, ArH), 7.34
would greatly decrease the cost for detection. What's more, (t, 1H, ArH), 7.52 (t, 1H, ArH), 7.85 (t, 2H, ArH), 8.38 (d, 1H, ArH),
detection of intracellular Al3+ and Fꢀ in live SiHa cells by uo- 8.86 (s, 1H, NH), 10.22 (s, 1H, CH]N), 11.24 (s, 1H, OH). 13C
rescence imaging has been demonstrated in this study.
NMR (DMSO-d6): 161.51, 161.31, 145.24, 136.86, 136.74, 134.12,
133.38, 132.95, 128.72, 127.51, 123.87, 115.25. HRMS (ESI): calcd
for C12H12N3O2 (HNS + H) 230.0930, found 230.0927.
2. Experimental
2.1 Chemicals and instrumentation
2.3 Cell imaging study
2-Hydroxy-1-naphthaldehyde (98%) was purchased from Energy
Chemical (Shanghai, China). Aminourea hydrochloride was
purchased from Aladdin Reagent Co. (Shanghai, China). All the
other chemical reagents were of analytical grade and used as
received without further purication. Stock solutions of metal
ions were prepared by dissolving their nitrates in water and
stock solutions of anions were prepared from the correspond-
ing sodium salts. Hexamethylenetetramine–HCl buffer solution
of pH 5.3 was prepared by mixing appropriate ratios of
0.01 mol Lꢀ1 hexamethylenetetramine and 0.1 mol Lꢀ1 HCl
solutions. Double distilled water was used throughout. All the
solutions have been stocked in the plastic centrifugal tubes.
The UV absorption spectra were recorded on a Puxi TU-1901
UV-vis absorption spectrophotometer (China). Fluorescence
measurements were performed on a LS-55 spectrouorimeter
(PerkinElmer, USA). The samples were excited at 390 nm. The
excitation and emission slits were set at 6 and 4 nm, respec-
tively. IR spectra were taken as KBr pellets on a TENSOR II
infrared spectrometer (Bruker, Germany). 1H-NMR spectra were
In vitro experiments were performed using SiHa cells. SiHa cells
were cultured in DMEM medium, which was supplemented
with 10% fetal bovine serum (FBS) in an atmosphere of 5% CO2
at 37 ꢂC. Immediately before the experiments, the cells were
incubated with 50 mL HNS (10ꢀ3 M, ethanol solution) in 1 mL
0.1 M sterile PBS buffer for 30 min at room temperature. Aer
incubation, the cells were washed with PBS buffer and incu-
bated with Al3+ (100 mM) for additional 10 min at room
temperature. Finally, the cells treated with HNS and Al3+ were
further incubated with NaF (500 mM) for another 10 min. The
uorescence intracellular images were obtained using an
Olympus FV1000 confocal microscope (Tokyo, Japan) with
a 40ꢁ objective (excited at 405 nm).
3. Results and discussion
3.1 Spectral characteristics of HNS and HNS–Al3+
HNS could be dissolved in water when 10% (v/v) of ethanol was
added. So, the spectroscopic properties of HNS were investi-
gated in an ethanol–water (1 : 9, v/v) solution at pH 5.3. As
shown in Fig. 1a, the absorption spectrum of HNS exhibits
structured absorption spectrum corresponding to the p–p*
transitions of naphthalene unit observed in naphthalene
derivatives.36 Upon addition of increasing amounts of Al3+, the
longest-wavelength absorption band red shied from 348 nm to
381 nm. The presence of two clear isosbestic points (330 and
363 nm) indicates the formation of a complex between HNS and
¨
recorded on a DRX-300 spectrometer (Fallenden, Switzerland).
The pH measurements were carried out on a pHS-3C acid-
ometer (Shanghai Precision & Scientic Instrument Co., Ltd,
China). High resolution mass spectra (HRMS) were obtained on
a Bruker micrOTOF-Q III mass spectrometer. The uorescence
intracellular images were obtained using an Olympus FV1000
confocal microscope (Tokyo, Japan) with a 40ꢁ objective
(excited at 405 nm).
Al3+
.
2.2 Synthesis of 2-hydxoxy-1-naphthaldehyde semicarbazone
(HNS)
Fig. 1b shows the changes in the emission intensity of HNS
upon gradual increase of [Al3+]. HNS shows very weak broad
emission in the range from 400 nm to 550 nm with a maximum
at 449 nm on excitation at 390 nm. Upon addition of Al3+, HNS
shows large uorescence enhancement, accompanied with
a blue-shi of emission maxima from 449 nm to 441 nm. The
results suggest that Al3+ most likely forms stable uorescent
complex with HNS. Schiff-bases usually have low emission due
to the isomerization reaction around the imine linkage C]N.37
This isomerization, however, is inhibited by the binding of Al3+
ions leading to uorescence switching of the receptor. In
Scheme 1 shows the facile one step synthesis of the ligand HNS.
Aminourea hydrochloride (259 mg, 2.32 mmol) was dis-solved in
Scheme 1 The synthesis of probe HNS.
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Al3+. In order to obtain a higher signal-to-noise, pH ¼ 5.3 with
hexamethylenetetramine–hydrochloric acid buffer solution was
chosen throughout the experiment.
Selectivity of HNS as the uorescence chemosensor for Al3+
was studied in the presence of various competing metal ions.
Under the same conditions as used above for Al3+, we tested the
uorescence responses of HNS toward other metal ions such as
Pb2+, Na+, Cd2+, K+, Mg2+, Cu2+, Co2+, Zn2+, Ni2+, Hg2+, Ca2+, Fe3+
and In3+. As shown in Fig. 3a, signicant spectral changes were
observed only in the case of Al3+. In contrast, treatment with
other metal ions resulted in no signicant changes, demon-
strating that HNS is highly selective for Al3+ over competing
metal ions. Furthermore, it was observed that the emission
intensity of the Al3+–HNS complex was not remarkably affected
by most coexistent metal ions except Cu2+ and Fe3+ (Fig. 3b).
Cu2+ showed complete quenching in fact, where luminescence
was even less than that of HNS alone. A similar phenomenon
was previously reported by Jang et al.38 Thus HNS can be applied
as an effective uorescent sensor for Al3+ in the presence of
most competing metal ions.
Based on the uorometric spectra studies, a calibration
curve was constructed by plotting the values of F ꢀ F0 against
Al3+ concentration (inset of Fig. 1b). A good linear relationship
between F ꢀ F0 and the concentration of Al3+ could be obtained
in the range of 0.8–8 mM (R2 ¼ 0.9834). The limit of detection
was measured to be 6.75 ꢁ 10ꢀ8 M (signal to noise ratio of 3 : 1),
which is satisfactory to the Al3+ detection in drinking water
Fig. 1 (a) UV/vis spectra of HNS (40 mM) in the presence of different
concentrations of Al3+ (0–10 equiv.) and (b) fluorescence titration
spectra of HNS (4 mM) upon the addition of Al3+ ions (0–8 equiv.) in
EtOH/H2O (1 : 9, v/v, pH 5.3). The inset in (b) shows the fluorescence
intensity of HNS as a function of Al3+ ion concentration) indicates the
formation of a complex between HNS and Al3+
.
within World Health Organization (WHO) limit (200 mg Lꢀ1
,
7.41 mM).39 In terms of sensitivity, the detection limit of the
proposed method is better than or comparable to those of
addition, the chelation of HNS with Al3+ increases the rigidity of
the molecular assembly, resulting in enhancement of emission
intensity ascribed as CHEF.
3.2 Fluorescence sensing of Al3+
Optimization of pH on the efficiency of the sensor was essential.
Fluorescence pH titrations were carried out for this purpose.
Fig. 2 clearly demonstrates that at the pH range from 4.2 to 5.4,
the HNS–Al3+ system showed maximum emission intensity but
decrease outside this range. Most plausibly, breakage of imine
linkage of HNS at too low pH prevents coordination of Al3+ while
at high pH values OHꢀ may succeed against HNS in binding to
Fig. 3 (a) Fluorescence spectra changes of HNS (4 mM) in the presence
of various metal ions (8 mM) in EtOH/H2O (1 : 9, v/v, pH 5.3). (b)
Fig.
2
Effect of pH on fluorescence intensity of the Al3+–HNS Fluorescence intensities of HNS (4 mM) at 441 nm (I441 nm) upon
complex in EtOH/H2O (1 : 9, v/v), [HNS] ¼ 4 mM, [Al3+] ¼ 20 mM.
addition of Al3+ in the presence of interfered metal ions.
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previously reported Schiff base probes for Al3+ detection.8,9,15 of deprotonation during the coordination to metal ions. The
The relative standard deviation for ve repeated measurements amino proton peak (Hb) at around 6.37 ppm became broader,
of 8.0 ꢁ 10ꢀ6 M of Al3+ was 1.08%, which illustrated that the indicating the coordination of the amino nitrogen to Al3+
.
response of HNS toward Al3+ was highly reproducible. It should Meanwhile, the imine proton peak (Hc) at around 10.22 ppm
be noted that this switch on sensing process could be easily became less intense and slightly downeld shied by 0.02 ppm,
observed by the naked eye. As shown in Fig. 7, HNS alone only supporting the coordination of the imine nitrogen to Al3+. The
1
exhibited very weak uorescence, but gave a strong blue uo- overall changes in H NMR spectra indicate the complexation
rescence in the presence of Al3+
.
between Al3+ and HNS through amino-N, azomethine-N and
phenolic-OH. Based on the Job's plot, IR spectra, mass spectra
and NMR titration, we proposed a rational coordinated mode
that aluminium ion is hexa-coordinated with two tridentate
ligand HNS shown in Fig. 5.
3.3 Binding mode of HNS with Al3+
A Job plot obtained from emission data showed a 2 : 1 stoichi-
ometry of the complex formed between HNS and Al3+
(Fig. S4a†), which was corroborated by the mass spectra of Al3+
–
3.4 Fluorescence sensing of Fꢀ
HNS complex. The HRMS spectrum showed a peak at m/z
483.1361 corresponding to 2HNS + Al3+–2H+ [calcd, m/z:
483.1345] (Fig. 4), indicating that the binding of Al3+ to HNS
induced deprotonation of the phenolic –OH group of HNS.
Based on a 2 : 1 binding mode, the association constant (K) was
evaluated from the Al3+ ions titration curve (Fig. S4b†) using the
modied Benesi–Hildebrand method19 and was found to be
The sensor Al3+–HNS for uoride detection was prepared in situ
by addition of 2.0 equiv. of Al3+ to C2H5OH/H2O (1 : 9, v/v)
solution of HNS. The Fꢀ sensing property of Al3+–HNS was
then evaluated by uorescence titration experiments and the
results were depicted in Fig. 6. As shown in Fig. 6a, the uo-
rescent intensity at 441 nm can be signicantly quenched by Fꢀ
ions. The quenching effect of Fꢀ on the uorescence emission
of the system is concentration dependent. There is a good linear
relationship (R2 ¼ 0.9957) between the uorescence intensity
and Fꢀ concentration in the range of 0.8–20 mM. Thus, probe
HNS could not only act as a sensor for Al3+ but also for Fꢀ in
a successive manner.
1.14 ꢁ 104 Mꢀ1
.
Further evidence for the Al3+ coordination was obtained
from the FT-IR and NMR spectral studies. In the IR spectrum of
Al3+–HNS complex shown in Fig. S5,† the sharp peaks at
3450 cmꢀ1 and 3350 cmꢀ1 may be attributed to N–H stretching
of –CONH2 group of HNS. On co-ordination with Al3+ ions, these
peaks became a broad band, indicating that the primary amide
participated in the binding with Al3+. In addition, the stretching
vibration band of C]N at 1603 cmꢀ1 shied to a lower
frequency by 31 cmꢀ1, clearly indicating the coordination of
imine nitrogen atom of HNS to aluminium ion.
Interferences from common anions have also been studied
under the same conditions as used above for Fꢀ. Out of the
tested anions, signicant quenching was observed only in case
of uoride (Fig. 6b). Furthermore, the other coexistent anions
had a small and negligible effect on the emission intensity of
the system, suggesting the high selectivity of the Al3+–HNS
1H NMR spectroscopy was used to ascertain the binding
mode of HNS to Al3+. 1H NMR spectra of HNS were recorded in
DMSO-d6 with increasing concentrations of Al3+ (as its nitrate
salt). Signicant spectral changes were observed as shown in
Fig. 5. Aer addition of Al3+, the Ha protons of the phenolic
hydroxyl progressively disappeared, suggesting the occurrence
ensemble for Fꢀ over other anions. The detection limit of Al3+
–
HNS complex as a uorescent sensor for the analysis of Fꢀ was
obtained from a plot of uorescence intensity as a function of
Fig. 5 Top: Binding mode of Al3+–HNS system. Bottom: 1H NMR
spectra of HNS in the presence of different concentrations of Al
(NO3)3$9H2O in d6-DMSO: (1) HNS only; (2) HNS + Al3+ (0.25 equiv.)
and (3) HNS + Al3+ (0.5 equiv.) (4) HNS + Al3+ (1 equiv.).
Fig. 4 The ESI-MS spectra of Al3+–HNS complex.
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Fig. 7 UV/vis spectra of HNS (40 mM) in the presence of Al3+ (4 equiv.)
and Al3+ (4 equiv.) + Fꢀ (8 equiv.). Inset: the visual change exhibited for
HNS in the presence of Al3+ and Fꢀ under UV light.
HNS + Al(NO3)3 (2.0 equiv.) + NaF (8.0 equiv.) (Fig. S7†). The
peak of 2HNS + Al3+–2H+ [calcd, m/z: 483.1345] at m/z ¼
483.1355 became very weak and the peak at m/z ¼ 230.0924
corresponded to [HNS + H+] (230.0930) displayed a prominent
peak, which further proved that the [Al3+–HNS] complex
released the free HNS by addition of Fꢀ. The overall changes in
Fig. 6 (a) Fluorescent emission spectra of Al3+–HNS in the presence
of different concentrations of Fꢀ in ethanol/water ¼ 1 : 9 at pH 5.3.
[HNS] ¼ 4 ꢁ 10ꢀ6 M, [Al3+] ¼ 8 ꢁ 10ꢀ6 M, and (b) competitive signaling
of fluoride ions by Al3+–HNS in the absence (the twill) and presence
(the black) of other anions as background in ethanol/water ¼ 1 : 9 (pH
¼ 5.3). [HNS] ¼ 4 ꢁ 10ꢀ6 M, [anions] ¼ 8 ꢁ 10ꢀ5 M.
1
UV-vis spectra, H NMR spectra and HRMS analysis conrmed
the dissociation between Al3+ and HNS, meanwhile, indirectly
demonstrated the higher binding affinity of Al3+ toward Fꢀ
compared to that with HNS.
the concentration of the different amounts of Fꢀ added. It was
found that Al3+–HNS has a detection limit of 7.89 ꢁ 10ꢀ7 M for
Fꢀ, which is much lower than the maximum contaminant level
dened by the U.S. Environmental Protection Agency
(4.0 mg Lꢀ1, 211 mM).40
3.5 Cellular imaging by uorescence microscopy
To demonstrate the potential of HNS to image Al3+ in living
matrices, we carried out the experiments in SiHa cells. First, an
MTT assay in SiHa cells has been performed to explore the
cytotoxicity of HNS (Fig. S8†). The result conrmed that the HNS
has no signicant cytotoxicity on SiHa cells at a low concen-
tration. As shown in Fig. 8, the cells showed no detectable
uorescence upon incubation only with HNS (50 mM) for
30 min. However, bright blue uorescence was observed aer
the cells were incubated with receptor HNS (50 mM) and Al3+
(100 mM) simultaneously. Cells were subsequently incubated
with a 500 mM solution of Fꢀ for 10 min under the same
conditions, whereupon a signicant decrease in the uores-
cence was observed. During the whole process, the cells
remained in good cell morphological state, demonstrating the
low cytotoxicity of the probe further. These results demonstrate
that HNS has good cell-membrane permeability and can be
used for sequential detection of Al3+ and Fꢀ in an in vitro
cellular system.
This phenomenon can be supposed that the Al3+ has been
captured by Fꢀ ions from the [Al3+–HNS] complex to form a new
more stable complex AlF3 and resulted in the release of free
HNS (Scheme 2). To elucidate the nature of the strong binding
1
of Fꢀ to Al3+, the UV-vis spectra, H NMR spectra and HRMS
experiments have been conducted respectively. As shown in
Fig. 7, toward adding Fꢀ, the characteristic band at 381 nm of
[Al3+–HNS] complex is disappeared, while the absorption
1
response is recovered to the original state of free HNS. The H
NMR spectrum of [Al3+–HNS] complex has been investigated in
absence and in presence of Al3+ in DMSO-d6 (Fig. S6†). The
broader amino proton peak (Hb) at around 6.37 ppm became
sharp and the imine proton peak (Hc) at around 10.22 ppm
became recovered, indicating the dissociation of the Al3+ to HNS
aer adding Fꢀ. This was further conrmed by HRMS studies of
4. Conclusions
In conclusion, we have developed an “off–on” type chemosensor
HNS for Al3+ in weak acid aqueous solution. The receptor
showed a high sensitivity for Al3+ detection at concentrations
ranging from 0.8 mM to 8 mM with a detection limit of 67.5 nM.
Moreover, uorescence of the Al3+$HNS complex was drastically
quenched by Fꢀ via Al3+ displacement. Thus the Al3+$HNS
ensemble represents itself as an effective chemosensor for Fꢀ
Scheme 2 Probable sensing mechanism for Al3+ and Fꢀ by HNS.
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Fig. 8 Fluorescence images of SiHa cells treated with HNS, Al3+ and
Fꢀ. (Left) Bright field image; (middle) fluorescence image; (right)
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too. The detection limit of Fꢀ is quite low (0.789 mM) using this
ensemble. Furthermore, HNS has been utilized successfully for
sequential detection of Al3+ and Fꢀ ions in living cells. These
merits of HNS, i.e., requiring facile one-step synthesis, working
in aqueous media, possessing low detection limits, displaying
high selectivity, and being suitable for monitoring Al3+ in living
cell, make HNS a promising candidate as a chemosensor for
Al3+ and Fꢀ ions.
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Conflicts of interest
There are no conicts to declare.
˘
22 M. Bineci, M. Baglan and S. Atılgan, Sens. Actuators, B, 2016,
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This work was nancially supported by the National Natural 23 Y. Wang, Y. F. Song, L. Zhang, G. G. Dai, R. F. Kang,
Science Foundation of China (No. 21976113), the Natural
Science Foundation of Shanxi Province (No. 201801D221142,
W. N. Wu, Z. H. Xu, Y. C. Fan and L. Y. Bian, Talanta,
2019, 203, 178.
201801D221059), the Scientic and Technologial Innovation 24 X. Y. Sun, L. L. Wu, J. S. Shen, X. G. Cao, C. Wen, B. Liu and
Programs of Higher Education Institutions in Shanxi (No.
2019L0787) and Beijing Natural Science Foundation (No.
7194337).
H. Q. Wang, RSC Adv., 2016, 6, 97346.
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