Ion sensing of sister sensors based-on calix[4]arene in aqueous medium and their bioimaging applications

Article abstract of DOI:10.1016/j.dyepig.2020.108741

Here, sister calix[4]arene derivatives containing two NBD (7-nitro-benzofurazan) units in 1,3-(distal) derivatives (sensors 4&8) were prepared and characterized by ¹H, ¹³C NMR, FTIR, elemental analysis, and fluorescence spectroscopy. The ion binding properties of multi-channel sensors 4&8 were performed in the presence of various cations and anions. Both sensor compounds, 4&8, showed “on–off” type fluorescence response towards Cu²⁺ cation and H₂PO₄^?&F^? anions with high selectivity in aqueous solution (CH₃CN/H₂O, 4/1, v/v). The connected spectroscopic parameters were investigated as the complex stoichiometry, binding constant etc. for a better result. Moreover, the lowest detection limit of 4 for sensing Cu²⁺ and H₂PO₄^?&F^? were obtained 2.4 × 10^?8, 9.1 × 10^?7, 9.7 × 10^?7 mol/L respectively. the lowest detection limit of Cu²⁺ and H₂PO₄^?&F^? by 8 was obtained as 2.9 × 10^?8, 9.7 × 10^?7, 8.9 × 10^?7 mol/L respectively. The confocal microscope was performed to investigate the sensor properties of 4&8 towards ions on living cells. Sensors 4 and 8 showed fluorescence properties on the A549 cell line, while it was observed to turn off the fluorescence intensity in cells treated with H₂PO₄^?, F^? and Cu²⁺ ions. Besides, compounds 4 and 8 can be used to identify H₂PO₄^?, F^? and Cu²⁺ ions in living cells.

Full text of DOI:10.1016/j.dyepig.2020.108741

Dyes and Pigments 184 (2021) 108741
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: http://www.elsevier.com/locate/dyepig
Ion sensing of sister sensors based-on calix[4]arene in aqueous medium and
their bioimaging applications
,
,*
Malak Alizadaa, Alev Gula, Mehmet Oguza b, Ahmed Nuri Kursunlua, Mustafa Yilmaza
a Department of Chemistry, University of Selcuk, Campus, 42031, Konya, Turkey
b Department of Advanced Material and Nanotechnology, Selcuk University, 42031, Konya, Turkey
A R T I C L E I N F O
A B S T R A C T
Keywords:
Calix[4]arene
NBD
Here, sister calix[4]arene derivatives containing two NBD (7-nitro-benzofurazan) units in 1,3-(distal) derivatives
(sensors 4&8) were prepared and characterized by 1H, 13C NMR, FTIR, elemental analysis, and fluorescence
spectroscopy. The ion binding properties of multi-channel sensors 4&8 were performed in the presence of various
cations and anions. Both sensor compounds, 4&8, showed “on–off” type fluorescence response towards Cu2+
cation and H2POꢀ4 &Fꢀ anions with high selectivity in aqueous solution (CH3CN/H2O, 4/1, v/v). The connected
spectroscopic parameters were investigated as the complex stoichiometry, binding constant etc. for a better
result. Moreover, the lowest detection limit of 4 for sensing Cu2+ and H2PO4ꢀ &Fꢀ were obtained 2.4 × 10ꢀ 8, 9.1
× 10ꢀ 7, 9.7 × 10ꢀ 7 mol/L respectively. the lowest detection limit of Cu2+ and H2POꢀ4 &Fꢀ by 8 was obtained as
2.9 × 10ꢀ 8, 9.7 × 10ꢀ 7, 8.9 × 10ꢀ 7 mol/L respectively. The confocal microscope was performed to investigate
the sensor properties of 4&8 towards ions on living cells. Sensors 4 and 8 showed fluorescence properties on the
A549 cell line, while it was observed to turn off the fluorescence intensity in cells treated with H2POꢀ4 , Fꢀ and
Cu2+ ions. Besides, compounds 4 and 8 can be used to identify H2POꢀ4 , Fꢀ and Cu2+ ions in living cells.
Colorimetric
Fluorescent
Bioimaging
1. Introduction
activation of dioxygen, which is essential for the survival of all living
organisms. On the other hand, the abnormal levels of it can lead to some
Recently, the design and synthesis of multifunctional chemo-sensors
for the recognition of one or more ionic and neutral analytes have
received considerable attention owing to their low cost, simplicity of
instruments, high sensitivity and efficiency in comparison with the
previous single-target chemical-sensors [1–11]. Some cations and an-
ions can be detected by various techniques such as electrochemical
methods, atomic spectroscopy, ion-selective electrodes, anodic stripping
voltammetry (ASV), mass spectrometry (MS), inductively coupled
plasma mass spectroscopy (ICP-MS), total reflection X-Ray fluorimetry
(TXRF), voltammetry, atomic absorption spectroscopy (AAS), induc-
tively coupled plasma atomic emission spectrometry (ICP-AES) and
surface-enhanced Raman scattering and so forth [12–16]. Among
different techniques for recognition both cations and anions, the fluo-
rogenic and colorimetric analysis methods have received remarkable
attention due to their easy operation, remote control, instant response
time, the multiplicity of measurable parameters and so on [17–19].
Among the varied essential metal ions in human bodies, Cu2+ ion plays
critical roles as a catalytic cofactor in diverse enzyme activities. Besides,
it has multiple functions that various physiological processes like
diseases such as the increase in blood pressure, vomiting, lethargy,
neurotoxicity, acute hemolytic anemia and neurodegenerative [20–24].
Fluoride is biologically an important anion due to its effects on the
human body. The lack or excess of fluoride in the human body can lead
to severe health risks like dental caries and osteoporosis [25–27].
Similarly, phosphates necessary for the continuation of life are an
indispensable constituent of two major biopolymers DNA and RNA play
important roles as receptors in biological systems. They are found in the
structure of some drugs such as chemotherapeutic and antiviral forms
[28–30].
Calixarenes are known as one of the important classes of supramo-
lecular compounds that have received more attention in sensor chem-
istry [31–37]. Calixarenes have exceptional properties owing to the
flexible template, their 3D structure, easy chemical modifications and
they demonstrate various structural conformation providing perfect
cavities with special shapes and sizes for different ions [38–40]. They
have some important properties like low cytotoxicity, biocompatibility
in several bioimaging applications like cell imaging, zebrafish, etc. They
are commonly used for promising materials for many sensor
* Corresponding author.
E-mail address: myilmaz42@yahoo.com (M. Yilmaz).
https://doi.org/10.1016/j.dyepig.2020.108741
Received 24 April 2020; Received in revised form 23 July 2020; Accepted 24 July 2020
Available online 20 August 2020
0143-7208/© 2020 Elsevier Ltd. All rights reserved.

M. Alizada et al.
Dyes and Pigments 184 (2021) 108741
Scheme 1. The synthesis route of sensors 4 and 8.
applications owing to their perfect sensitive and selective abilities
[41–43].
in aqueous solution and living system [44–48]. Because of the biological
roles along with the associated harmful effects, the synthesis of efficient
multifunctional colorimetric and fluorogenic chemo-sensors for the
detection of two or more cation and anion have become a highly hot
topic of interest to many scientists in the worldwide [49–53]. In this
work, based on the above all these ideas, we have been focusing on
synthesizing two new NBD bearing calix[4]arene derivatives to
Otherwise, the color-changing based on synthetic chemical probes
can be observed by the naked eye in daylight or longwave light. Such as
thiadiazole, NBD-chloride (4-chloro-7-nitro benzofurazan), phenol-
phthalein, Bodipy, rhodamines, quinolone derivatives, and acridine-
based on sensors are commonly used for the recognition of metal ions
2

M. Alizada et al.
Dyes and Pigments 184 (2021) 108741
Fig. 1. (a) Fluorescence spectra of sensor 4 [a), b)] & 8 [c), d)] (5.0
μ
M) recorded in CH3CN/H2O (4/1,v/v) in the presence of various cations (Na+, Mg2+, Ca2+
,
Fe2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Hg2+, Al3+, Cr3+, Ag+, Pb2+) and anion (Fꢀ , Clꢀ , Brꢀ , Iꢀ , H2PO4ꢀ , HPO42ꢀ , PO34ꢀ , HSOꢀ4 , SO42ꢀ , NOꢀ3 , CH3COOꢀ ) (20.0 equiv.)
(longwave: 365 nm).
investigate their both cations and anions detection studies and their cell
imaging application in A549 cell line.
2.2. The preparing of compounds
The precursors 1–3 and 5–7 were synthesized by using known pro-
cedures [54–56]. As shown in Scheme 1, the hydrazide derivative of
calix[4]arene were synthesized from the reaction between the ester
derivative of calix[4]arene and hydrazine hydrate according to the
literature [57]. Target calix[4]arene derivatives (4, 8) as shown in
Scheme 1 were synthesized according to the methods given below.
2. Experimental section
2.1. Materials, methods, and instruments
The perchlorate salts all of the metal ions (Na+, Mg2+, Ca2+, Fe2+
,
Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Hg2+, Al3+, Cr3+, Ag+, Pb2+) and the
tetrabutyl ammonium salts of all the anions (Fꢀ , Clꢀ , Brꢀ , Iꢀ , H2PO4ꢀ ,
HPO24ꢀ , PO43ꢀ , HSO4ꢀ , SO42ꢀ , NO3ꢀ , CH3COOꢀ ) were procured from
Sigma-Aldrich. Other materials and reagents used for the experiments
were supplied from different commercial sources (Merck, Alfa-Aeser,
Acros). All the solvents used were analytical reagent grade and were
distilled and dried before use. The 1H NMR/13C NMR UV–vis and fluo-
rescence spectra were performed with Varian NMR Spectrometer (400
MHz), Shimadzu 1700 UV–Vis spectrophotometer and Perkin Elmer LS
55 spectrometer, respectively. Also, infrared spectra were measured
using a Bruker FTIR instrument and Elemental analyses were performed
on a Leco CHNS-932 analyzer.
2.3. Synthesis of NBD bearing calix[4]arene derivatives (4 and 8)
Precursor 3 or 7 (0.25 mmol) and 4-chloro-7-nitro benzofurazan
(0.55 mmol) was dissolved in dichloromethane (50 mL), and Na2CO3
(1.37 mmol) was added to it. The reaction was stirred at room tem-
perature for 6 h. The reaction was checked by TLC using ethyl acetate:
petroleum ether (40:60). The solvent was evaporated under reduced
pressure and the remaining solid was washed several times in diethyl
ether and dried under N2. Brick-color solid product was obtained.
Characterization of Compound 4: Mp: 161–163 ◦C; Yield: 85%;
FTIR (ATR): 1317 cmꢀ 1 (NO2) and 1525 cmꢀ 1 (NO2), 1H NMR (400
MHz, DMSO): δ (ppm) 1.13 (s, 18H, But), 1.17 (s, 18H, But), 3.81 (bs,
4H, ArCH2Ar), 4.26 (bs, 4H, ArCH2Ar), 4.86 (bs, 4H-OCH2CO), 7.36 (s,
8H, Ar-H), 8.02 (bs, 2H, Ar-HNBD), 8.41–8.54 (m, 2H, –CONH), 8.67 (bs,
3

M. Alizada et al.
Dyes and Pigments 184 (2021) 108741
Fig. 2. The I0/I ratios of sensor 4 [a), b), c)] & 8 [d), e), f)] (5
μ
M) against the various concentration graph of Cu2+ cation and H2PO4ꢀ &Fꢀ anions (1
μM, 2 μM, 3 μM,
4 μM, 5 μM, 6 μM, 7 μM 8 μM, 9 μM and 10 μM (λemmax = 560; λex = 460 nm in CH3CN/H2O (4:1)).
Cal. for (%) C60H66N10O12; H, 5.94; C, 64.39; N, 12.51. Found: H, 6.23;
C, 64.56; N, 12.77.
Table 1
The binding constants R2 values and of anion&cation.
Characterization of Compound 8: Mp: 114–116 ◦C; Yield: 75%;
FTIR (ATR): 1320 cmꢀ 1 (NO2) and 1519 cmꢀ 1 (NO2). 1H NMR (400
MHz, DMSO): δ (ppm) 3.51 (bs, 4H, ArCH2Ar), 4.28 (bs, 4H, ArCH2Ar),
4.90 (s, 4H-OCH2CO), 6.83 (s, 2H, Ar-H), 6.61 (s, 2H, Ar-H), 7.07–7.16
(m, 8H, Ar-H), 7.92 (bs, 2H, Ar-HNBD), 8.31(bs, 2H, NH-CO), 8.67 (bs,
2H, Ar-HNBD), 11.29 (s, 2H, -OH). 13C NMR (100 MHz, DMSO):δ (ppm)
167,71, 152.62, 150.03, 143.83, 142.94, 135.95, 134.04, 131.01,
129.22, 128.00, 73.56, 55.39, 31.16. Analytical Cal. for (%)
Sensor
Anion&cation
KSV
R2
4
Cu2+
4.7 × 105
1.7 × 105
1.9 × 105
0.9797
0.9924
0.9917
Fꢀ
H2POꢀ4
8
Cu2+
3.1 × 105
0.2 × 105
0.18 × 105
0.9775
0,9934
0,9928
Fꢀ
H2POꢀ4
C44H34N10O12; H, 3.83; C, 59.06; N, 15.65. Found: H, 4.07; C, 59.24; N,
15.79.
2H, Ar-HNBD), 11.06 (s, 2H, -OH). 13C NMR (100 MHz, DMSO):δ (ppm)
167,80, 150.04, 143.86, 142.28, 136.00, 133.45, 133.00, 131.01,
129.26, 127.56, 126.05, 73.58, 34.55, 34.12, 31.82, 31.33. Analytical
4

M. Alizada et al.
Dyes and Pigments 184 (2021) 108741
Fig. 3. Job’s plot for interaction of sensor 4 [a), b), c)] & 8 [d), e), f)] (5.0
μ
M) with Cu2+ cation and H2POꢀ4 &Fꢀ anions at 560 nm, respectively.
2.4. Cell culture and confocal microscope imaging
3. Results and discussion
Human lung cancer (A549) cells were obtained from American Type
Culture Collection, (ATCC), Rockville, MD, USA, and cultured MEM
Eagle with Earle’s BSS with 10% fetal bovine serum (FBS) and 1% an-
tibiotics (penicillin and streptomycin) at 37 ◦C and 5% CO2. The medium
was changed every 24 h and sub-cultured when the cells reached
80–90% growth. A549 cells were seeded on 6 well plates on the slide as
15 × 104. After 24 h for confocal imaging, the cells were treated with the
3.1. Synthesis and characterization of NBD bearing calix[4]arene probes
(4,8)
This study aims to synthesis two new NBD appended calix[4]arene
derivatives to detect Cu2+, Fꢀ , and H2POꢀ4 as colorimetric and fluoro-
metric (Scheme 1). In this regard, calix[4]arene derivatives (compounds
1, 2, 3, 5, 6 and 7) were synthesized according to previously reported
methods [54–57]. Then, the NBD was reacted with calix[4]arene de-
rivatives (3 and 7) in dichloromethane to synthesize compounds 4 and 8
as calix[4]arene-amide derivatives (Scheme 1). The structures of all the
calixarenes were characterized by spectroscopic methods like FT-IR, 1H
NMR, 13C NMR, elemental analysis (Supporting information,
Figs. S1–S14). The formation of 4 was confirmed by the appearance of
the characteristic nitro and amide bands at 1317&1525 cmꢀ 1 and 1696
cmꢀ 1, respectively (Fig. S3). In 1H NMR of 4, the peaks at 8.02&8.67,
1.13&1.17 and 4.86 ppm assign to new two aromatic protons, two t-butyl
medium and 50 μM of compounds 4 and 8 for 1 h. After the incubation,
the medium was removed and washed three times with PBS buffer to
remove compounds 4 and 8 present in the cells. Cells treated with
compounds 4 and 8 were treated with 100
μ
M H2POꢀ4 , Fꢀ , Cu2+ for 1 h
and the medium was removed and washed 3 times with PBS buffer.
Finally, the slide preparation was performed, and the image was ob-
tained with a confocal microscope (Nikon/A1R1).
5

M. Alizada et al.
Dyes and Pigments 184 (2021) 108741
Fig. 4. Schematic representation of complex formation between sensor 4&8 and ions.
Fig. 5. Confocal microscopy images of A549 cells: a) bright field image of living A549 cells; b) cells treated with compound 4 (20
μ
M); c) A549 cells treated with 4
for 1 h, then treated with H2POꢀ4 (50
μ
M) for 1 h; d) A549 cells treated with 4 for 1 h, then treated with Fꢀ (50
μM) for 1 h; e) A549 cells treated with 4 for 1 h, then
treated with Cu2+ (50
μM) for 1 h.
groups and -OCH2 units, respectively (Fig. S9). The carbon signal of the
carbonyl groups was observed at 167.7 ppm in the 13C NMR spectrum
(Fig. S10). In the FT-IR spectrum of 8, the stretching bands at 1320 cmꢀ 1
and 1519 cmꢀ 1 were attributed to N=O vibration in NO2 fragments.
Moreover, the specific N-C=O stretching bands of 8 unit appeared
around 1686 cmꢀ 1 (Fig. S6). The protons of -OCH2 units and NBD groups
appeared at 4.90 and 7.92&8.67 ppm; the carbon signals of amide
groups were also observed at 167.6 ppm that all data confirmed to the
structure of 8 (Figs. S13 and S14).
The cation&anion binding affinities of 4 and 8 were investigated in
the presence of various cations (Na+, Mg2+, Ca2+, Fe2+, Fe3+, Co2+
,
Ni2+, Cu2+, Zn2+, Hg2+, Al3+, Cr3+, Ag+, Pb2+) and anions (Fꢀ , Clꢀ , Brꢀ ,
6

M. Alizada et al.
Dyes and Pigments 184 (2021) 108741
Fig. 6. Confocal microscopy images of A549 cells: a) bright field image of living A549 cells; b) cells treated with compound 8 (20 μM); c) A549 cells treated with 8
for 1 h, then treated with H2POꢀ4 (50
μ
M) for 1 h; d) A549 cells treated with 8 for 1 h, then treated with Fꢀ (50
μM) for 1 h; e) A549 cells treated with 8 for 1 h, then
treated with Cu2+ (50
μM) for 1 h.
Iꢀ , H2PO4ꢀ , HPO24ꢀ , PO34ꢀ , HSO4ꢀ , SO42ꢀ , NOꢀ3 , CH3COOꢀ ) by using fluo-
higher sensitivity for Cu2+ cation. This status can be explained that the
complex interaction between ligand and the metal ion is stronger as to
the weak intermolecular interaction between ligand and anion. Namely,
the coordination between 4&8 and Cu2+ cation is more stable.
On the other hand, the binding constants of 4&8 toward ions were
calculated by using Stern-Volmer equation as shown in Table 1. Sensor 4
has the best Ksv value for Cu2+ cation in parallel with the concentration
studies.
rescence spectroscopy in CH3CN/H2O (4/1, v/v) solution at 5.0 μM
concentration. The sister sensors, 4 and 8, exhibited the emission
maximum around 560 nm excited at 460 nm. As can be seen in Fig. 1,
both sensors gave a similar result that H2POꢀ4 &Fꢀ and Cu2+&Hg2+
quenched to the intensities of 4 and 8. The color of the solutions in both
sensors changed from green to colorless under longwave light in pres-
ence of Cu2+&Hg2+ cations. The intensities of fluorescence were
significantly quenched by Cu2+ ion, indicating effective complexation
with this cation. The strong quenching effect can be explained that the
multi donor atoms on NBD fragments of sensors easily coordinated with
Cu2+ ion and almost 20-folds quenching was observed. Similarly,
H2POꢀ4 &Fꢀ anions were captured by the NBD arms of sensors depending
on multi inter-molecular interactions and hydrogen bonds. H2POꢀ4 &Fꢀ
anions caused a 4-folds quenching effect while other anions revealed an
insignificant response. Moreover, the fluorescence wavelengths of sister
sensors shifted slightly to blue or red in the presence of both Cu2+ cation
and H2POꢀ4 &Fꢀ anions. These changes can be attributed to an internal
charge transfer between ligands and ions. According to our reference, a
fluorescent sensor prepared with 4-nitrobenzofurazan, we preferred to
pH study range as pH: 7 due to ideal conditions [58]. All spectroscopic
measurements carried out at pH: 7.
To illuminate complex stoichiometry, Job plot technique was used.
As known, Job plot technique is used to determine the complex stoi-
chiometry of a binding event that the absorbance against the mole
fraction is obtained with a plotted graph. When the absorbance reaches a
maximum in the graph, the analyte/ligand ratio can be determined. As
the graphs; the complex formations were determined as 2:1 for all
ligand-anion&cation pairs (Fig. 3).
As understood from Fig. 4, it was thought that the nitrogen atoms on
NBD units of 4&8 play an important role in capturing Cu2+ cation and
H2POꢀ4 &Fꢀ anions. So, these atoms act electron donors to Cu2+ while
they interact with H2POꢀ4 &Fꢀ anions in the hydrogen bond principle.
The experiments on the competing ions were carried out in the
presence of the Cu2+ cation, H2PO4ꢀ and Fꢀ anions (5 × 10ꢀ 6 M) mixed
with (Na+, Mg2+, Ca2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Hg2+, Al3+
Cr3+, Ag+, Pb2+) (Fꢀ , Clꢀ , Brꢀ , Iꢀ , H2PO4ꢀ , HPO24ꢀ , PO43ꢀ , HSO4ꢀ , SO24ꢀ
,
,
To observe the fluorescence quenching of 4 and 8 towards Cu2+
cation and H2POꢀ4 &Fꢀ anions, the fluorescence experiments with
increasing concentrations of ions were performed, respectively
(Fig. S16). As shown in Fig. 2, all graphs presented a linear curve that
fluorescence intensity of sensors was gradually quenched upon the
enhancing of ion concentration. When the ion sensitivity of 4 and 8
compared, I0/I ratios show that the ion sensitivity of sensor 4 is higher
for towards Cu2+ cation and H2POꢀ4 &Fꢀ anions. Otherwise, when the
cation&anion sensitivity of 4 and 8 compared, both sister sensors have a
NOꢀ3 , CH3COOꢀ ) at 5 × 10ꢀ 6 M concentration. The results were given
the fluorescence intensities of sensor 4&8 as a table (Table S1).
Accordingly, these results confirm that sensor 4&8 can behave as a se-
lective fluorescent sensor towards both Cu2+ cation and H2PO4ꢀ /Fꢀ an-
ions in the presence of other competing metal ions.
To confirm better the complexation between 4&8 and Fꢀ , 1H NMR
experiments were performed out in the absence and presence of this
anion in DMSO‑d6 (Fig. S15). The addition of 2.0 equivalents of Fꢀ to
7

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Dyes and Pigments 184 (2021) 108741
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solutions of the probes 4&8 resulted in significant spectral changes.
Signals belong to phenolic -OH observed at 11.06 and 11.29 ppm for
4&8, the amide signals at 8.49 and 8.31 ppm were disappeared.
On the other hand, it was performed the fluorescence imaging
studies with confocal microscopy to control the biological applications
of compounds 4 and 8 in the A549 cell line. By keeping the compounds 4
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and 8 concentration stable (20
μM), a decrease was observed due to
H2PO4ꢀ , Fꢀ , Cu2+ (50
μM) ions in intracellular orange fluorescence
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emission resulting from the complex formation with compounds 4 and 8.
As shown in Figs. 5 and 6, the control group of A549 cells (Figs. 5a-6a)
was observed orange fluorescence when the lung cancer cell line was
treated only with compounds 4 and 8 (Figs. 5b-6b). Fluorescence in-
tensity decreased in cells treated with H2POꢀ4 , Fꢀ , Cu2+ (Fig. 5c-d-e/6c-
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4. Conclusion
In conclusion, the synthesis and spectroscopic properties of sister
calix[4]arene derivatives containing two NBD having cone conforma-
tion, sensor 4 and 8, for multi-analyte sensing were reported. Both sister
sensors, 4 and 8, showed the fluorescence quenching process for the
sensitive recognition of Cu2+ cation and H2PO4ꢀ &Fꢀ anions in CH3CN/
H2O (4/1, v/v), respectively. Interaction of sensors 4&8 with ions
induced completely quenching of fluorescence intensity through a 1:2
(ligand:ion) binding mode. Also, the confocal microscope imaging was
performed to identify H2POꢀ4 , Fꢀ , Cu2 ions in compounds 4 and 8 in
living cells. The utility of compounds 4 and 8 as a bio-analytical mo-
lecular tool was successfully illustrated by fluorescence monitoring of
H2POꢀ4 , Fꢀ , Cu2+ ions in biological processes. As a result, it was observed
that the A549 cells treated with H2POꢀ4 , Fꢀ , Cu2+ ions turn off the
fluorescent intensity. The use of both sister sensors, 4 and 8 to recognize
Cu2+ cation and H2POꢀ4 &Fꢀ anions will enormously extend ion types by
the various derivatives of calix[4]arene having multi-donor atoms.
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Declaration of competing interest
[22] Jiao Y, Zhou L, He H, Yin J, Gao Q, Wei J, et al. A novel rhodamine B-based “off-
on’’fluorescent sensor for selective recognition of copper (II) ions. Talanta 2018;
184:143–8.
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
[23] Feng S, Gao Q, Gao X, Yin J, Jiao Y. Fluorescent sensor for copper (II) ions based on
coumarin derivative and its application in cell imaging. Inorg Chem Commun
2019;102:51–6.
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integrating a smartphone with the colorimetric response from a NBD-
benzimidazole based dyad. Phys Chem Chem Phys 2019;21(22):11839–45.
[25] Li J, Lin H, Cai Z, Lin H. A novel coumarin-based switching-on fluorescent and
colorimetric sensor for Fꢀ . J Lumin 2009;129(5):501–5.
Acknowledgments
We thank the Research Foundation of Selcuk University for financial
support (Project Number: 19201072) of this work.
[26] Wu Y-C, You J-Y, Jiang K, Xie J-C, Li S-L, Cao D, et al. Colorimetric and ratiometric
fluorescent sensor for Fꢀ based on benzimidazole-naphthalene conjugate:
reversible and reusable study & design of logic gate function. Dyes Pigments 2017;
140:47–55.
Appendix A. Supplementary data
[27] Sivaraman G, Chellappa D. Rhodamine based sensor for naked-eye detection and
live cell imaging of fluoride ions. J Mater Chem B 2013;1(42):5768–72.
[28] Ojida A, Mito-Oka Y, Sada K, Hamachi I. Molecular recognition and fluorescence
sensing of monophosphorylated peptides in aqueous solution by bis (zinc (II)ꢀ
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the highly selective recognition of Fe3+ in aqueous solution and H2PO4ꢀ in
acetonitrile solution. Tetrahedron Lett 2018;59(11):1059–64.
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.dyepig.2020.108741.
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