Triazole-naphthalene based fluorescent chemosensor for highly selective naked eye detection of carbonate ion and real sample analyses

Article abstract of DOI:10.1016/j.inoche.2021.108883

Herein, the design and synthesis of triazole-naphthalene hybrid for selective colorimetric and fluorometric sensing of carbonate ion has been reported. The probe has been thoroughly characterized by ¹H and ¹³C NMR and HRMS spectroscopy. CK exhibits an excellent selectivity and sensitivity towards carbonate ions over other anions by changes in both UV–Vis absorption spectra and emission spectra. The limit of detection of carbonate ion in absorbance and emission spectra has 7.2 nM and 1.8 μM respectively. The plausible sensing was confirmed with the help of the Job's plot, FTIR, NMR titration and theoretical studies. Also, naked eye detection method of carbonate from colorless to yellow color is the most conspicuous application of probe CK. The receptor CK providing valuable practical sensor for environmental analyses of carbonate ion. Further, we mimic new logic gate circuit by using the sensing performance of carbonate ion with probe.

Full text of DOI:10.1016/j.inoche.2021.108883

Inorganic Chemistry Communications 133 (2021) 108883
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Triazole-naphthalene based fluorescent chemosensor for highly selective
naked eye detection of carbonate ion and real sample analyses
Harikrishnan Muniyasamy, Chithiraikumar Chinnadurai, Malini Nelson,
*
Muniyappan Chinnamadhaiyan, Siva Ayyanar
Supramolecular and Organometallic Chemistry Laboratory, Department of Inorganic Chemistry, School of Chemistry, Madurai Kamaraj University, Madurai 21, India
A R T I C L E I N F O
A B S T R A C T
Keywords:
Herein, the design and synthesis of triazole-naphthalene hybrid for selective colorimetric and fluorometric
sensing of carbonate ion has been reported. The probe has been thoroughly characterized by 1H and 13C NMR
Triazole-naphthalene hybrid
Colorimetric sensor
Carbonate
and HRMS spectroscopy. CK exhibits an excellent selectivity and sensitivity towards carbonate ions over other
anions by changes in both UV–Vis absorption spectra and emission spectra. The limit of detection of carbonate
Real sample analysis
Logic gate
ion in absorbance and emission spectra has 7.2 nM and 1.8 M respectively. The plausible sensing was confirmed
μ
with the help of the Job’s plot, FTIR, NMR titration and theoretical studies. Also, naked eye detection method of
carbonate from colorless to yellow color is the most conspicuous application of probe CK. The receptor CK
providing valuable practical sensor for environmental analyses of carbonate ion. Further, we mimic new logic
gate circuit by using the sensing performance of carbonate ion with probe.
1
. Introduction
Recognition of anions by fluorescent and colorimetric chemosensors
inverse opal photonic crystal polymers in aqueous solution for the visual
detection of carbonate ions. Velmurugan et al. [20] synthesized dipyrene
based fluorescent probe for the dual detection of silver and carbonate
became more prevalent in environmental monitoring, biological sci-
ions with its bioimaging applications. Liu et al. [21] proposed the
cascade recognition for Fe3 and CO
+
2ꢀ
based on asymmetric squaraine
ence, drug delivery and medicinal chemistry [1–4]. Amongst the anions,
3
2
ꢀ
monitoring the occurrence of carbonate ions (CO
3
) befitted more
dye with logic gate applications. Singh et al. [22] designed a chemo-
2
ꢀ
ꢀ
essential for day-to-day life. Because, CO
3
ions are the chief constit-
sensor based on hydrazinyl pyridine for selective detection of F ion in
2
ꢀ
uent in carbon cycle [5] and also it exists predominantly as metal car-
bonates in the environment [6,7]. The extreme level of carbonate anion
also leads to decisive stage [8]. Since there are numerous methods for
carbonate sensing, chemosensing are the most sensible and highly se-
lective method for carbonate sensing [9–12]. Hence, designing a che-
organic media and CO
ated diarylethene based probe for dual recognition of Cu and CO
and its applications. Saleem et al. [24] explained the facile synthesis of
3
in aqueous media. Zhang et al. [23] deliber-
2
+
2ꢀ
3
2
ꢀ
ꢀ
an optical sensor for CO
3
and HCO detection. Apart from these lit-
3
eratures, it is obligatory to construct a chemosensor with simple starting
2
3
ꢀ
2ꢀ
mosensor for the selective detection of CO
anion without any
materials aimed at the efficient detection of CO
3
anion selectively
interferences is an indispensable research area now a days. Furthermore,
most of the chemosensors depends upon photo induced electron transfer
without any competitors. Accordingly, herein we reported newly
intended novel naphthalene and triazole hybrid probe from the simple
Knoevenagel condensation of 2-Hydroxy-naphthalene-1-carbaldehyde
and naphthalene substituted triazole with good yield for the selective
colorimetric sensing of carbonate ion in aqueous medium. The interac-
tion of probe CK with carbonate ion occurs through inhibition of photo
induced electron transfer mechanism. The main advantages of our work
such as metal free probe, simple detection method compared to poten-
tiometric [25] and electrochemical [26], dual detection method
(colorimetric and fluorometric), detection medium is aqueous, naked
(
PET) mechanism which involves enhancement or quenching of fluo-
rescence in turn produces Off-On or On-Off sensing mechanism [13–16].
Till to date, based on PET mechanism for the carbonate sensing were
infrequently described in reports [17]. So, manipulating carbonate
sensor via PET mechanism aroused as an outstanding depiction in che-
mosensor approach. In recent times, Tavallali et al. [18] established
novel use of calmagite as colorimetric anion chemosensor and solid-state
sensor for carbonate ion in running water. Li et al. [19] developed
*
Corresponding author.
E-mail address: drasiva@gmail.com (S. Ayyanar).
https://doi.org/10.1016/j.inoche.2021.108883
Received 24 June 2021; Received in revised form 21 August 2021; Accepted 27 August 2021
Available online 30 August 2021
1
387-7003/© 2021 Elsevier B.V. All rights reserved.

H. Muniyasamy et al.
Inorganic Chemistry Communications 133 (2021) 108883
o
Reagents and condition: (a) N, N-diisopropylethylamine, DMF, 50 C ; (b) K
2
CO
3
, DMF,
o
o
5
0 C; (c) Methanol, Glacial acetic acid, 80 C.
◦
◦
Scheme 1. Schematic representation of the probe synthesis. Reagents and condition: (a) N, N-diisopropylethylamine, DMF, 50 C; (b) K
2
CO
3
, DMF, 50 C; (c)
◦
Methanol, Glacial acetic acid, 80 C.
Fig. 1. (a) Selectivity spectra of CK (10
μ
M) with various anions (5
μ
M) (b) Sensitivity experiment of CK with difference concentration (0.5 to 5.5 M) of car-
μ
bonate ion.
eye detection, probe is applied to real sample analysis, and we have very
low limit of detection range compared to recently published articles. The
application of this carbonate sensor in commercial aspect is proceeding.
JASCO (V-630) and emission was recorded in a JASCO (F-8500). In
addition, the density functional calculation was performed by using the
Gaussian 09 program. The ground-state and excited state geometries
were optimized by using the restricted B3LYP/6–31 g (d, p).
2
. Experimental section
2
.2. UV–visible and emission spectroscopy
2
.1. Materials and methods
The probe was dissolved in acetonitrile solvent and the concentration
All the chemicals and reagents were used in this work are analytical
of the probe solution is 1 mM. 20
μ
L of it was diluted to 2 ml of DD water
grade. hydrazinecarboximidamide, N, N-diisopropylethylamine, sodium
hydroxide, hydrochloric acid, potassium carbonate, 2-hydroxy-1-naph-
thaldehyde purchased from Sigma Aldrich, and all the dry solvent
were purchased from Merck. The 1H and C NMR spectrum were
placed in a 3 ml cuvette and the total concentration of probe were 10 M
μ
for the selectivity, and competitive spectra in absorbance spectroscopy.
UV–Vis spectra were obtained at room temperature. The total concen-
13
tration of probe was 60 M for the selectivity, and competitive spectra in
μ
6
recorded on Bruker Avance 400 MHz in a DMSO‑d solvent using TMS as
emission spectroscopy. Emission spectroscopy were obtained at room
temperature.
an internal standard and chemical shifts are given in ppm (δ-scale) and
coupling constants are given in Hertz (Hz). Column chromatography
was carried out in silica gel (60–120 mesh size) using petroleum ether
and dichloromethane as an eluent. UV–Vis spectrum was recorded in a
2

H. Muniyasamy et al.
Inorganic Chemistry Communications 133 (2021) 108883
0.20
0.15
0.10
0.05
0.00
3
2
2
1
1
00
50
00
50
00
5
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19
2
ꢀ
Fig. 2. Interference study of 1. CK alone (10
μ
M) 2. CK + CO
3
3. CK +
2
2
2
2
2
2
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
2ꢀ
ꢀ
2ꢀ
ꢀ
CO
CO
CO
CO
CO
CO
3
3
3
3
3
3
+CH
3
COO , 4. CK + CO
3
+SCN , 5. CK + CO
3
+Br , 6. CK +
2ꢀ
3
CO 3. CK
Fig. 4. Interference study of 1. CK alone, 2. CK
+
+
ꢀ
2ꢀ
ꢀ
2ꢀ
ꢀ
+Cl , 7. CK
+
CO
3
+F , 8. CK
+
CO
3
+HCO
3
,
9. CK
+
2ꢀ
2ꢀ
ꢀ
2ꢀ
2ꢀ
2ꢀ
ꢀ
CO
CO
3
3
+CH
3
COO , 4. CK + CO
3
+S , 5. CK + CO
3
ꢀ
+HCO
3
6. CK +
2ꢀ
2ꢀ
ꢀ
2ꢀ
ꢀ
+HPO
4
, 10. CK + CO
3
2ꢀ
+NO
3
, 11. CK + CO
3
+N
3
, 12. CK +
ꢀ
2ꢀ
ꢀ
2ꢀ
2ꢀ
ꢀ
+SCN , 7. CK + CO
3
+Br , 8. CK + CO
3
+Cl , 9. CK + CO
3
+F ,
2ꢀ
ꢀ
2ꢀ
2ꢀ
+S
,
13. CK
+
CO
3
+I , 14. CK
+
CO
3
+SO
4
,
15. CK
+
2ꢀ
ꢀ
2ꢀ
ꢀ
2ꢀ
ꢀ
1
0. CK + CO
3
+I , 11. CK + CO
3
+HPO
4
, 12. CK + CO
3
+NO
3
, 13. CK
ꢀ
2ꢀ
2ꢀ
2ꢀ
2ꢀ
+NO
2
, 16. CK + CO
3
+PO
4
, 17. CK + CO
3
+ClO
4
, 18. CK +
2ꢀ
ꢀ
2ꢀ
2ꢀ
2ꢀ
ꢀ
2
+
CO
3
2ꢀ
+N
3
, 14. CK + CO
3
+SO
4
, 15. CK + CO
3
+NO
, 16. CK +
ꢀ
ꢀ
+HSO
3
.UV–vis spectrum, concentration of carbonate ion (5
M).
μ
M) and
2ꢀ
2ꢀ
2ꢀ
2ꢀ
CO
3
+PO
4
, 17. CK + CO
3
+ClO
4
, 18. CK + CO
3
+HSO
3
.concentra-
M).
competitive ion concentration is (5
μ
tion of carbonate ion (30
μ
M) and competitive ion concentration is (30
μ
Fig. 3. Selectivity spectra of the CK (60
μ
M) with various anions (30 M) in
μ
Fig. 5. Fluorescence spectra of CK upon the gradual addition (2.5 to 32.5
μ
M)
fluorescence.
2ꢀ
of CO
3
ion.
2
.3. Synthetic procedure of probe CK
The synthesis of the compound CK started with commercially
available starting material 1 which is treated with hydrazinecarbox-
imidamide in presence of N, N-diisopropylethylamine and dimethyl
◦
formamide solvent at 50 C for 12 hrs, 20 ml of 2 N NaOH solution is
added for further completion of reaction. Then the mixture is filtered
and the filtrate is neutralized with 2 N hydrochloric acid. The obtained
precipitate is filtered, dried and recrystallized from ethanol. Compound
2
2
is obtained as a white solid with 76% yield. To a mixture of compound
◦
, K
2
CO
3
and DMF, 2-chloromethylacetate is added slowly at 50 C and
the solution is stirred constantly for 12 hrs. Then the reaction mixture is
poured into water to get the solid precipitate and the solid is filtered,
dried and recrystallized from ethanol [27]. Compound 3 obtained as a
white solid with 88% yield. A mixture of compound 3 and 2-hydroxy
◦
naphthaldehyde is heated to 80 C for 12 hrs in presence of catalytic
Scheme 2. Plausible sensing mechanism of probe with receptor.
amount of glacial acetic acid and methanol solvent to get the solid
3

H. Muniyasamy et al.
Inorganic Chemistry Communications 133 (2021) 108883
Fig. 6. Job’s plot of carbonate ion in (a) absorbance spectra and (b) emission spectra.
probe 402 nm band was disappeared and new band at 454 nm was
appeared and remaining two * and n- * was slightly bathochromic
shifted and remaining others anions does not have spectral changes
Fig. 1a). Hereafter, we doing the sensitive experiment in absorbance
π-
π
π
(
spectra, the probe CK with incremental addition of carbonate ion, we
observed the gradually decreased of 402 nm band and formation of new
band at 454 nm band. Upon the high concentration of carbonate ion,
4
02 nm band was disappeared and 454 nm band was obtained, and
moreover two isosbestic bands were appeared at 327 and 421 nm, these
bands represent our probe CK and carbonate has strong interaction.
(
Fig. 1b).
In competitive experiments, the probe CK with the presence of car-
bonate and remaining other analyte shows that 454 nm band was
appeared, this studies clearly shows that CK is highly selective carbonate
sensor towards other anions (Fig. 2). Hereafter, we calculated the limit
of detection is 7.2 nM from the absorbance titration spectra (Fig. S4).
Finally, the absorbance response of CK to carbonate was analyzed by the
linear plot (Fig. S5) of Benesi-Hildebrand equation: 1/(A ꢀ A
o
) = 1/{K
2
3
ꢀ
(
A
max ꢀ A
o
) [CO
]} + 1/[Amax ꢀ A
o o
], where A is the absorbance of
probe in the absence of guest (carbonate), A is the absorbance register in
the presence of added analyte, Amax is absorbance in the presence of
added [analyte]max, K is an binding constant. The binding constant of
Fig. 7. FTIR spectra of CK alone and CK with carbonate ion.
ꢀ 2
probe with carbonate is 22.8 × 10 M from the absorbance titration
spectra.
product CK. The product is filtered, washed well with water, dried and
weighed. The yield of compound CK found to be 88%. 1H NMR (400
MHz, DMSO) δ 12.65 (S, 1H), 10.13(S, 1H), 8.62 (d, J = 8 Hz, 1H), 8.38
In addition, we performed reversible experiment for our chemo-
sensor CK. The notable change in the naked eye (colorless to yellow
2
ꢀ
color) of CK has happened after the addition of CO
3
due the formation
complex. Then, the absorbance wavelength retained to the
original basal condition of CK when acetic acid was added to the solu-
(
d, J = 8 Hz, 1H), 8.00 (d, J = 8 Hz, 1H), 7.82 (d, J = 8 Hz, 1H), 7.74 (t, J
2
ꢀ
of CK-CO
3
=
16 Hz, 1H), 7.68(t, J = 16 Hz, 2H), 7.47(d, J = 4 Hz, 1H), 7.38(d, J =
Hz, 3H), 7.04 (d, J = 6 Hz, 1H), 4.11 (dd, 2H), 2.96 (s, 3H) 2.68–2.60
8
2
ꢀ
tion of CK-CO
3
complex, suggesting that the presence of acetic acid
(
m, 1H), 1.19(q, 2H) 0.86(q, 2H). 13C NMR (400 MHz, DMSO) δ 169.02,
brings about the release of free CK and the formation of bicarbonate
anion. The reversible interconversion of CK was repeated several times
with acetic acid, demonstrating that CK can be developed as an excellent
reversible chemosensor for the detection of carbonate anion (Fig. S6).
1
1
1
5
63.29, 162.67, 158.44, 150.77, 142.93, 132.48, 129.04, 128.31,
28.10, 127.62, 127.01, 126.88, 125.51, 124.62, 122.96, 122.72,
19.17, 110.18, 52.98, 33.92, 13.38, 8.07, 7.62. HRMS m/z calcd
08.1569, found 508.1743.
3
. Results and discussion
3
.1. Emission spectra
CK synthesized from the condensation reaction of naphthalene
In Emission spectra, CK shows weak emission at 513 nm in DD water,
substituted triazole and 2-hydroxy-naphthalene-1-carbaldehyde
Scheme 1). After that, our synthesized compound was confirmed by
the 513 nm band represents the photo induced electron transfer from
naphthalene imine moiety to the triazole moiety and C–
(
–
N isomerism
various analytical techniques. Hereafter, we measured the optical
properties of the CK in both absorbance and emission spectroscope in DD
water. In absorbance spectrum, CK shows three absorbance band at 282,
ꢀ
also presented, after that we added various anions such as CH
3
COO ,
ꢀ
ꢀ
2ꢀ ꢀ ꢀ ꢀ ꢀ 2ꢀ ꢀ ꢀ ꢀ
N
3
, HCO
3
, SO
4
, I , SCN , NO , F , S , HPO , Cl , Br emission
3 4
spectra does not change, but after the addition of carbonate ion, the
intensity of 513 nm band has increased and strong fluorescence was
happened. The increasing intensity after addition of carbonate ion to
probe is attributed due to the inhibition of PET process (Fig. 3). Then,
interference studies were carried in the probe alone, probe with
3
38, 402 nm, the 282 and 338 nm band represented as
π
-
π
* and n- *
π
transition respectively. The lower energy band at 402 nm is may be due
to the photo induced electron transfer and C-N isomerism. The probe CK
also has three absorbance band after the addition of carbonate ion,
4

H. Muniyasamy et al.
Inorganic Chemistry Communications 133 (2021) 108883
1
Fig. 8. H NMR titration spectra of CK alone and CK with difference concentration of carbonate ion.
Fig. 9. Optimized structure of (a) CK alone and (b) CK with carbonate ion.
carbonate, and probe with carbonate in presence of another analyte.
From the competitive experiment results shows a characteristic intensity
of 513 nm band does not have drastic changes indicated that CK selec-
tively sense carbonate ion even though presence of other relevant anions
determined from the slope of the plot (Imax ꢀ Imin) / (I ꢀ Imin) vs 1/[C]
2
ꢀ
for CK-CO
3
(Fig. S8). The binding constant of carbonate in CK is 8.3 ×
ꢀ
2
10 M.
(
Fig. 4).
To explore the interaction of CK with carbonate, emission spectra
3
.2. Mechanism of carbonate in CK
variation of CK was investigated by using the titration of different
concentration of carbonate. The probe 513 nm band intensity was
gradually increased by the gradual addition of carbonate ion (Fig. 5).
This emission titration spectra (Fig. S7) helps to calculate the limit of
detection (LOD), we found the LOD of carbonate ion in emission spectra
The sensing mechanism (Scheme 2) of CK with carbonate was
confirmed by jobs plot, FTIR, NMR and DFT studies. Initially, we know
the binding stoichiometric of probe with analyte by using the Job’s plot
analysis. Job‘s plot experiment has been accomplished using UV–visible
and emission spectroscopy (Fig. 6). The Job’s plot results shows that
binding efficiency of receptor CK and carbonate is 2:1 binding stoi-
chiometric. Our probe has hydroxyl group, so that two molecules of
hydroxyl group in CK is interacted with one molecule of the carbonate
ion, this is reason for 2:1 binding ratio of carbonate with probe CK
In FTIR spectra (Fig. 7) shows that CK has stretching frequencies
is 1.8
μM. Benesi-Hildebrand equation are 1/I ꢀ Imin = 1/Imax ꢀ Imin +
(
1/K[C]) (1/Imax ꢀ Imin) where Imin is the emission intensity of CK
without carbonate, I is the emission intensity of CK with the given
concentration of carbonate, Imax is the emission intensity of CK at the
concentration of complete saturation point, K is the binding constant,
[
C] is the concentration of CK. The binding constant value has been
ꢀ 1
3
434, 2932, 1735, 1608 and 1465 cm has naphthalene substituted
5

H. Muniyasamy et al.
Inorganic Chemistry Communications 133 (2021) 108883
Fig. 10. Frontier orbitals of (a) CK alone and (b) CK with carbonate ion.
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
2ꢀ
ꢀ
2ꢀ
ꢀ
ꢀ
2ꢀ
ꢀ
Fig. 11. Photograph of colorimetric response of CK alone and CK with various anions, CH
3
COO , SCN , Br , Cl , F , CO
3
, HCO
3
, HPO
4
, NO
3
, N
3
, S , I
2
ꢀ
and SO
4
. (From left to right).
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
2ꢀ
ꢀ
2ꢀ
ꢀ
ꢀ
2ꢀ
ꢀ
Fig. 12. Photograph of fluorometric response of CK alone and CK with various anions CH
3
COO , SCN , Br , Cl , F , CO
3
, HCO
3
, HPO
4
, NO
3
, N
3
, S , I and
2
ꢀ
SO
4
(From left to right).
O
–
H stretching, aromatic C-H stretching frequency of naphthalene ring,
that stretching frequency behaves like an acidic proton frequency and
–
–
–
–
ester carbonyl C
O stretching frequency, imine C
–
–
N stretching fre-
also carbonate carbonyl C
–
O stretching frequency was formed in the
region of 1467 cm , further more confirmation of new stretching fre-
ꢀ 1
quency, aliphatic C
H stretching frequency respectively. After that
ꢀ 1
interaction between the CK and sodium carbonate, shows that the probe
quency at 848 cm represented C O stretching frequency of carbon-
–
ꢀ 1
CK stretching frequencies were present but in addition to that new broad
ate. The band 588 cm is due to the OH bending of acidic proton. These
studies clearly shows that our naphthalene substituted hydroxyl proton
acts as binding site for carbonate ion.
ꢀ 1
stretching frequency from 2975 to 3458 cm is appeared due to the
carbonate anion interact with hydroxyl proton of naphthalene ring so
6

H. Muniyasamy et al.
Inorganic Chemistry Communications 133 (2021) 108883
Table 1
the reason for colorless to yellow color appearance in the naked eye
system. At the same time, probe with carbonate has enhance the emis-
sion in green color, but remaining others anions does not have emission
under 365 nm UV chamber (Fig. 12).
Truth table for logic circuit.
2
ꢀ
S. No.
CK alone
CO
3
Output
max = 454 nm
λ
1
2
3
4
.
.
.
.
0
0
1
1
0
1
0
1
0
0
0
1
3.4. Real sample analysis
More important study of the practical applicability of probe CK, real
sample analyses were achieved to determine the concentration of car-
bonate ion in the four different water samples. The sample 1 is reverse
osmosis treated water, sample 2 is without treatment reverse osmosis
water (tap water) from the Madurai Kamaraj University, Madurai dis-
trict, Tamil Nadu, India. The sample 3 is collected from Vaigai river,
Madurai district, Tamilnadu, India. The sample 4 is collected from
Thamirabarani at Thoothukudi district, Tamilnadu, India. The water
samples were spiked with standard carbonate at various concentrations
and determined by a standard addition method using the probe CK. We
prepared the stock solution of carbonate ion as different concentration
levels of 20 to 50 M. All the characteristics data are tabulated in the
μ
Table S1. The detection of carbonate ion concentration is very close to
the concentration of added carbonate ions in the sample 1 and sample 2,
but the sample 3 and 4 are slightly difference is due to the interfering of
real ions. Even though, the average recovery of the spiked samples was
found to be 100, 98, 112, 118 for RO, tap, and Vaigai, Thamirabarani
water samples respectively. These results show that the probe CK has
excellent selective and high sensitivity detection of carbonate ion in real
samples with high accuracy.
Fig. 13. Molecular logic circuit.
In addition to that, the interaction between the probe and analyte
was determined by proton NMR titration method. In the Fig. 8. shows
that two singlet peaks in the aromatic region, highly downfield singlet
represented as hydroxyl proton, another one singlet represented as
imine proton, remaining other aromatic protons represents as the two
moiety of naphthalene ring in the probe CK, after that aliphatic peaks in
the highly upfield protons represented the cyclopropane ring protons,
the aliphatic peak at 4.11 ppm represented the methylene proton and
the 2.96 ppm peaks represented the methoxy proton. After that the
addition of the 0.25 equiv. of carbonate ion in to CK probe, the probe
hydroxyl proton peak intensity was decreased and at the same time
remaining other aromatic and aliphatic peaks are upfield and further-
more, the addition of 0.25 equiv. of carbonate ion in to probe-analyte
solution, in this case the hydroxyl proton peak was vanished and
remaining other peak are slightly upfielded. NMR titration studies
clearly shows that our probe hydroxyl proton interacts more with car-
bonate ions when compared to other protons of our probe. Thus, the
binding stoichiometric 2:1 was confirmed by NMR titration studies.
Furthermore, our probe alone and probe with analyte were investi-
gated by Gaussian 09 program with the help of the density functional
theory B3LYP/6.31g (d, p) as basis set. The optimized structure of probe
CK alone and CK with carbonate ion in the Fig. 9. For the probe CK, the
electron density is mainly present in the cyclopropane substituted
naphthalene moiety in the ground state but in the excited state electron
density are transfer from cyclopropane substituted naphthalene to hy-
droxyl substituted naphthalene moiety, it’s due to PET process. Here-
after, probe with analyte shows that the electron density present in the
triazole and hydroxyl substituted naphthalene moiety in the HOMO
state, but in the LUMO state electron density are move to the carbonate
moiety, this transition clearly shows that carbonate ion inhibit the PET
process from the triazole to hydroxyl naphthalene substituted moiety
3
.5. Logic gate
The sensing performance of CK was also examined by logic circuit
model. The presence of probe in the solution denoted as 1, suppose the
absence of probe denoted as 0, like as the same for analyte in the inputs.
Hence the output has 454 nm absorbance band, in the UV–Visible
spectrum shows if probe alone does not form the 454 nm band, if analyte
alone does not form the 454 nm band, the 454 nm will be appeared when
the solution has both probe and carbonate ions so it is denoted as 1 and
other remaining as 0 (Table 1). After that we make the molecular logic
circuit is integrated with the help of various logic gates such as NOT, OR,
EXOR, AND gates. Based on the developing truth table, CK found to
entirely mimic the new logic gate circuit (Fig. 13) for the detection of
carbonate ion.
4
. Conclusion
In summary, we have established a new triazole and naphthalene
hybrid-based sensor for naked eye detection of carbonate ion. The
chemosensor CK exhibits an excellent selectivity and sensitivity towards
carbonate ions over other anions by changes in both UV–Vis absorption
spectra and emission spectra. The detection limit of carbonate ions is 7.2
nM from UV–Visible spectroscope and 1.8
μM from emission spectros-
copy, this is the lowest ever reported in the literature. Moreover, the
plausible sensing mechanism were confirmed by various methods such
Job’s plot, FTIR, proton NMR titration, and theoretical studies. We can
also apply our probe for the naked eye detection of carbonate ion in
solution phase. Furthermore, the probe CK is efficaciously applied in the
analysis of the environment samples for the rapid detection of carbonate
ions. Atlast, we hope that the new probe CK may be beneficial biological
sensor for carbonate ions.
(
Fig. 10).
3
.3. Application
In naked eye study, the probe CK dissolved in aqueous medium, at
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
that same time various anions such as CH
3
COO , F , Cl , Br , I , SCN ,
ꢀ
ꢀ
ꢀ
2ꢀ 2ꢀ
ꢀ
2ꢀ
NO
3
, N
3
, HCO
3
, SO
4
, S , HPO
4
and CO
3
are dissolved in water
CRediT authorship contribution statement
solvent. The addition of the various mono and divalent anions are added
to the probe CK, no color changes was observed except carbonate anion
addition. The probe CK has colorless solution when the addition of
carbonate anion, color changes was observed from colorless to yellow
color in the naked eye system (Fig. 11). The formation of 454 nm band is
Harikrishnan Muniyasamy: Data curation, Validation. Chithir-
aikumar Chinnadurai: Conceptualization, Data curation. Malini
Nelson: Validation, Writing – original draft. Muniyappan Chinna-
madhaiyan: Software, Resources, Validation. Siva Ayyanar:
7

H. Muniyasamy et al.
Inorganic Chemistry Communications 133 (2021) 108883
Supervision, review and editing.
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[
[
Declaration of Competing Interest
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chemical sensors: design features of optical sensors (optodes) based on selective
chromoionophores, Pure Appl. Chem. 61 (1989) 1613–1618.
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.
[
[
[
[
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major research (Grant No. EMR/2015/000969), Council of Scientific
and Industrial Research (CSIR) HRDG, New Delhi (Gant No. 01(2901)/
(
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[
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