High-contrast colourimetric probes for fluoride and trace water based on tautomerization of naphthalimide and application in fingerprint imaging

Article abstract of DOI:10.1016/j.saa.2021.119674

Three probes for fluoride ion and trace water based on naphthalimide were designed and synthesized. A new sensing mechanism based on naphthalimide tautomerization induced by fluoride ion and water was explored in the aprotic organic solvent. In the fluori

Full text of DOI:10.1016/j.saa.2021.119674

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 254 (2021) 119674
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
High-contrast colourimetric probes for fluoride and trace water based on
tautomerization of naphthalimide and application in fingerprint imaging
⇑
⇑
Xia Yan, Haichuang Lan , Yang Li, Xiaojing Yan, Qilin Xing, Wen Wang, Jiayu Zhang, Shuzhang Xiao
College of Biological and Pharmaceutical Sciences, China Three Gorges University, Yichang, Hubei 443002, PR China
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
À
When fluoride ion and trace water presented, the chemical probes based on naphthalimide showed sig-
nificant changes in colour, absorption, molecular structure. A new sensing mechanism based on the con-
trollable keto-enol tautomerism was applied for fluoride ion and trace water detection.
ꢀ
ꢀ
ꢀ
The F and H
2
O chemosensor based
on tautomerism as a sensing
mechanism was explored.
The absorption peak in the visible
range of 400–700 nm showed a
significant change.
A sensitivity optimization strategy of
the probe based on tautomerism was
developed.
a r t i c l e i n f o
a b s t r a c t
Article history:
Three probes for fluoride ion and trace water based on naphthalimide were designed and synthesized. A
new sensing mechanism based on naphthalimide tautomerization induced by fluoride ion and water was
explored in the aprotic organic solvent. In the fluoride ion sensing process, the probes exhibited a remark-
able absorption peak centred at 560 nm in the visible range of 400–700 nm. When trace water presented,
the newly formed absorption peak centred at 560 nm gradually disappeared. The sensitive colour varia-
tion of the probe also was used in fingerprint imaging. Accordingly, the significant changes in chemical
shift of dept135 and HNMR spectrum confirmed the structural transformation of the probes with high
contrast. Furthermore, this work also presented an optimization strategy for the sensitivity of the probe
based on regulatory tautomerization.
Received 14 December 2020
Received in revised form 18 February 2021
Accepted 28 February 2021
Available online 9 March 2021
Keywords:
1
Colourimetric
Tautomerization
Fluoride ion
Trace water
Ó 2021 Elsevier B.V. All rights reserved.
Naphthalimide
1
. Introduction
Fluoride ion (F ) as a typical representative has become a hot
porosis with the appropriate dose. However, excessive intake of
fluoride ions may lead to osteoporosis or metabolic disorder of
the immune system [2–4].
À
spot for detection [1]. Fluorine is an essential trace element for
the human body, which can prevent dental caries and treat osteo-
Fluoride can form a strong hydrogen bond with active proton,
and even capture proton aprotic in aprotic organic solvents. It is
due to the extremely electronegative of fluoride [5]. Therefore, flu-
oride receptor units were developed based on the above mecha-
nism. The classical structures have been reported, including urea
⇑
Corresponding authors.
E-mail addresses: haichuanglan@ctgu.edu.cn (H. Lan), shuzhangxiao@ctgu.edu.
[
6], thiourea [7], amine [8], amide [9], pyrrole [10], imidazole
cn (S. Xiao).
https://doi.org/10.1016/j.saa.2021.119674
1
386-1425/Ó 2021 Elsevier B.V. All rights reserved.

X. Yan, H. Lan, Y. Li et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 254 (2021) 119674
[
11], the nitrogenous heterocyclic compound [12], the phenolic
2. Experiments
compounds [13]. Fluoride is an ideal lewis base; therefore, the
acid-base reaction is used for fluoride detection. The organoboron
compound [14], Si-O bonds [15], and Si-C bonds [16] tend to react
with fluoride, which has been reported for fluoride detection in
water. The sensing mechanisms above mentioned all took full
advantage of the properties of fluoride ions and achieved ideal per-
formance in aprotic organic solvents or water.
The fluoride ion probes worked in aprotic organic solvent had
an advantage in trace water detection. The hydrogen bond
between fluoride ion and probes would be broken in the presence
of trace water. The resultant complex formed by fluoride ion and
probe recovered its initial state [17]. Therefore, the consequent
complex would be an excellent secondary probe for trace water.
The low-level water in surroundings played an important role
in biological and chemical processes, environmental systems,
industrial processes and human life. A small amount of water
may determine the germination of life [18]. Trace water may also
quench the reactive organic reaction [19]. Detection of trace water
could be applied to reveal traces of life [20].
2.1. General methods
The spectral-grade solvents used in the test were purchased
À
À
À
commercially and used directly without purification. F , Cl , Br ,
À
2À
À
À
À
3
À
I , SO , NO , H PO , HSO , OAc were obtained by the dissolution
4
3
2
4
of their respective potassium or sodium salts (0.1 mmol) in DMSO
1
13
(10 ml). H NMR (400MHZ) and C NMR (100MH ) spectra were
Z
collected on a Bruker Ultra shied TM 400MHZ Plus with DMSO d6
/CDCl3 as the solvent and tetramethylsilane (TMS) as an internal
standard. UV/vis spectra were measured on a Shimadzu UV-2600
spectrometer. High-resolution mass spectra were collected on a
Bruker Micro TOF II 10,257 instrument. The solvent DMSO, acetoni-
trile was dried by 4A molecular sieve.
2.2. Synthesis
Synthesis of N6: 4-Bromo-1,8-naphthalic anhydride(N7)
(10.0 g, 36.09 mmol) and n-butylamine (2.8 g, 38.2 mmol) were
dissolved in 200 ml ethanol, then 5 ml triethylamine was added
into the system. The mixture was stirred and refluxed for 3 h.
The reaction became a clear brown solution, and then suspension
appeared. Upon cooling, the crystal of the product was formed.
The gathered crystal was purified through recrystallization in etha-
nol to get the grey product N6 (7.2 g), yield, 60% [38].
Synthesis of N5: 4-Bromo-1, 8-naphthalic anhydride (5.0 g,
18.12 mmol) was dissolved in 110 ml ethanol. After refluxing,
3.5 ml triethylamine was added to make the mixture clear, and
then aniline (6.7 g, 72.46 mmol) was added. The mixture was stir-
red and refluxed for 5 h [39]. After cooling, the solid was precipi-
tated and filtered to get a grey product N7(2.8 g), yield, 44%.1H
The colourimetric sensing mechanism as a classical detection
strategy has been strengthened rather than eliminated. It is cur-
rently used in metal ions [21], anions [22], organic molecular
[
23], and biomacromolecule detection [24,25]. Colourimetric
detection can be carried out without a precise instrument and pro-
vides excellent visualization. Therefore, the design of colourimetric
probe needs multifactorial considerations. Excluding the specific
interaction with the target, simple sample preparation, and signif-
icant colour changes in the visual range is necessary [26]. In order
to obtain regular colour change, the tautomerism of chromophores
caused by fluoride ions has come into our view.
The tautomerization of chromophores generally causes clear
and distinct molecular properties. Therefore, the colour change
induced by the tautomerization also shows regularity and signifi-
cant [27–29]. The hydrogen bond is an essential factor for regulat-
ing the tautomerization of chromophores [30]. Therefore, fluoride
and water, as classical hydrogen bond acceptor and donor, are
excellent candidates for controlling the tautomerization. Compar-
ing with forming hydrogen bonds and capturing proton, the tau-
tomerization of chromophores can bring out a more significant
change in molecular structure [31]. And then the absorption or flu-
orescence of the isomerized fluorophore presents a dramatic shift.
Therefore, the tautomerization of chromophores induced by
hydrogen bonds can be used for fluoride and water detection.
Naphthalimides were chosen as chromophores for colourimet-
ric probes, due to its advantageous optical properties, such as
strong absorption in the visible region, high photostability, and
large Stokes shift [32]. The amide as a reaction site for fluoride
was introduced to naphthalimide, obtaining colourimetric fluoride
and water probe [33–35]. The absorption of the probes showed sig-
nificant change due to hydrogen bonding or deprotonation. The
hydrogen bonding and deprotonation only affected the charge dis-
tribution of chromophores in present colourimetric fluoride and
water probes [36,37]. To make better use of hydrogen bonding
and deprotonation, the tautomerization of naphthalimides was
induced in this work. The charge instability naphthalimides with
active proton could take place tautomerization under fluoride
and water. Therefore, the fluoride and water not only affected
the charge distribution of naphthalimides, but also reconstructed
conjugate system. The probes based on the tautomerization show
significant absorption change, exceeding 200 nm. It is uncommon
in colourimetric fluoride and water probes, and the strategy can
be widely used. Furthermore, the tautomerization mechanism of
3
NMR (400 MHz, CDCl ) d 8.75 (d, J = 7.3 Hz, 1H), 8.69 (d,
J = 8.5 Hz, 1H), 8.51 (d, J = 7.9 Hz, 1H), 8.13 (d, J = 7.9 Hz, 1H),
7.98–7.88 (m, 1H), 7.61 (t, J = 7.4 Hz, 2H), 7.54 (t, J = 7.4 Hz, 1H),
7.36 (d, J = 7.3 Hz, 2H).
Synthesis of N4: The synthesis method of N4 is the same as that
of N5, and the yield is 35% [40]. H NMR (400 MHz, CDCl
J = 3.7 Hz, 1H), 8.75 (d, J = 7.3 Hz, 1H), 8.70 (d, J = 8.5 Hz, 1H), 8.50
(d, J = 7.9 Hz, 1H), 8.13 (d, J = 7.9 Hz, 1H), 8.00 (t, J = 6.8 Hz, 1H),
7.96–7.90 (m, 1H), 7.55–7.48 (m, 1H), 7.45 (d, J = 7.9 Hz, 1H).
Synthesis of N3: Under nitrogen atmosphere, a mixture of N-
butyl-4-bromo-1, 8-naphthalimide (N6, 0.5 g, 1.51 mmol), diethyl
malonate (0.36 g, 2.26 mmol), cesium carbonate (2.0 g, 6 mmol),
and catalyst amount of cuprous iodide and L-proline were stirred
in dimethyl sulfoxide (4 ml) at 50 °C for 32 h. After cooling, the
mixture was poured into water (200 ml) to precipitate a solid,
which was filtered to get product (0.30 g), yield, 48%. 1H NMR
1
3
) d 8.78 (d,
3
(400 MHz, CDCl ) d 8.68 (d, J = 7.3 Hz, 1H), 8.66 (d, J = 7.7 Hz,
1H), 8.39 (d, J = 8.5 Hz, 1H), 7.89 (d, J = 7.7 Hz, 1H), 7.87–7.82
(m, 1H), 5.48 (s, 1H), 4.38–4.27 (m, 4H), 4.27–4.17 (m, 2H), 1.75
(dt, J = 15.3, 7.6 Hz, 2H), 1.49 (dq, J = 14.7, 7.4 Hz, 2H), 1.31 (t,
J = 7.1 Hz, 6H), 1.02 (t, J = 7.3 Hz, 3H). C NMR (101 MHz, CDCl )
3
d 167.40, 164.09, 163.82, 136.13, 131.18, 130.80, 130.21, 129.44,
1
3
128.72, 128.41, 127.41, 123.49, 122.98, 62.49, 61.76, 54.96, 40.32,
À
30.20, 20.40, 14.02, 13.86. HRMS(ESI) calcd for [MÀH]
À
C
23
H
24NO
6
: 410.1604; Found: 410.1609 [MÀH] .
Synthesis of N2: Under nitrogen atmosphere, a mixture of N5
(0.5 g, 1.4 mmol), diethyl malonate (0.34 g, 2.1 mmol), cesium car-
bonate (1.86 g, 5.7 mmol), and catalyst amount of cuprous iodide
and L-proline were stirred in dimethyl sulfoxide (4 ml) at 50 °C
for 32 h. After cooling, the mixture was poured into water
(200 ml) to precipitate a solid, which was filtered to get product
1
naphthalimides was explored by absorption and HNMR spectrum.
The sensitive colour variation of the probe also was applied to fin-
gerprint imaging.
N2 (0.50 g), yield, 82%. 1H NMR (400 MHz, CDCl
J = 8.2 Hz, 2H), 8.42 (d, J = 7.8 Hz, 1H), 7.95–7.79 (m, 2H), 7.56
3
) d 8.67 (d,
2

X. Yan, H. Lan, Y. Li et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 254 (2021) 119674
À5
(
s, 2H), 7.49 (s, 1H), 7.31 (d, J = 6.6 Hz, 2H), 5.48 (s, 1H), 4.28 (s, 4H),
(0–4.0) was added to the solution of N1, N2, N3 (10 M), a same
1
3
1
1
1
5
3
.28 (s, 6H). C NMR (101 MHz, CDCl ) d 167.35, 164.48, 164.25,
significant absorption peak centred at 560 nm gradually appeared
in the visible region (400–700 nm). The absorption peak at 265 nm
also dramatically increased, and the peak around 350 nm showed
minor change. Compared to absorption change in the ultraviolet
region, the new peak centred at 560 nm in visible region induced
by fluoride showed supermassive wavelength shift around
200 nm [41]. The new peak centred at 560 nm completely covered
the visual range from 400 nm to 700 nm. The remarkable colour
change from colourless to violet showed the excellent colourimet-
ric performance of these probes. Although the response pattern of
three probes was similar, their sensitive to fluoride was different.
As shown in Figue1d, e, f, the absorption intensity at 560 nm of
N1, N2, N3 versus the concentration of fluoride showed different
linear relationships, and their calibration curve slope was 0.380
(N1), 0.308(N2), 0.276 (N3). The detection limits of N1, N2, and
63.96, 136.63, 135.24, 131.62, 131.23, 129.90, 129.43, 129.08,
28.81, 128.61, 127.51, 126.99, 123.49, 123.07, 120.68, 62.53,
+
5.07, 14.03. HRMS (ESI) calcd for [M+H]
25 6
C H22NO : 432.1447;
+
Found: 432.1442 [M+H] .
Synthesis of N1: The synthesis method of N1 is the same as that
of N2, and the yield is 40%. 1H NMR (400 MHz, CDCl
) d 8.74 (d,
J = 3.4 Hz, 1H), 8.69 (d, J = 7.4 Hz, 1H), 8.66 (d, J = 7.7 Hz, 1H),
8
1
1
6
1
1
1
4
3
.43 (d, J = 8.5 Hz, 1H), 7.95 (t, J = 7.2 Hz, 1H), 7.90 (d, J = 7.7 Hz,
H), 7.85 (t, J = 7.9 Hz, 1H), 7.49–7.43 (m, 1H), 7.40 (d, J = 7.8 Hz,
H), 5.48 (s, 1H), 4.29 (dd, J = 6.9, 2.0 Hz, 4H), 1.28 (t, J = 7.0 Hz,
1
3
3
H). C NMR (101 MHz, CDCl ) d 167.32, 164.11, 163.83, 150.06,
49.41, 138.59, 136.81, 131.57, 131.19, 130.44, 130.07, 129.22,
28.52, 127.51, 126.84, 124.18, 123.43, 122.89, 62.54, 55.06,
+
4.02. HRMS (ESI) calcd for [M+H] C24
33.1394 [M+H] .
H
21
N
2
O
6
: 433.1400; Found:
+
À8
À8
N3 were calculated to be 7.6 Â 10 M(N1), 9.4 Â 10 M (N2),
À7
1
.1 Â 10 M (N3) according to the equation: 3
r/b (r: the stan-
dard deviation of 20 blank samples (10 mol/L of N1, N2, N3), b: cal-
ibration curve slope of N1, N2, N3) [42]. The reason for different
sensitive will be discussed further below.
2
.3. Fingerprint imaging
Test paper incorporated with N3-F was prepared by using qual-
itative filter paper. The filter paper was immersed in the 10 ml
solution of N3 (10 M) with an excess of Fluoride ion (0.1 M) in
À2
3.2.2. Selective
To evaluate the selective of the three probes N1, N2, N3, the
absorption change induced by different anion was recorded. As
dry acetonitrile for 5 min. The wet paper was then allowed to
dry using a hot air gun. This deep purple colour paper incorporated
with N3-F was used for fingerprint imaging.
À
À
À
2À
À
À
À
3
shown in Fig. 2 a, b, c, when Cl , Br , I , SO
4
, NO
3
2
, H PO
4
, HSO
,
À
Ac were present in the solution of three probes, there was an only
slight change in the absorption spectrum. Compared with the sig-
nificant change in absorption induced by the same concentration of
fluoride, the interference of selected competitive anions was little.
3
. Result and discussion
3.1. Synthesis
3
.2.3. Effects of pH
The fluoride probes were usually affected by pH. It is necessary
As shown in Scheme 1, three probes (N1, N2, N3) were prepared
according to the designed rout. The 4-Bromo-1, 8-naphthalic anhy-
dride (N7) was subjected to displacement reaction with n-
butylamine, aniline and 2-aminopyridine to obtain compounds
N6, N5, and N4. Then, the 4-position bromine atom of the com-
pound N4-6 was substituted with diethyl malonate to get the com-
pounds N1, N2 and N3. The detailed synthesis procedures and
characterization information were provided in the experimental
section and supplementary information.
to check the absorption properties of N1, N2, N3 in solution at dif-
ferent pH values (Fig. 3). Three probes N1, N2, N3 in DMSO were
added into different pH solution (0–14). The probe N1 showed
the increased absorption intensity at 470 nm in the basic medium
(
pH = 8–13). The absorption intensity at 470 nm of N2 and N3
changed little in the pH range 0–14.
3.2.4. Sensor mechanism
The three probes (N1, N2, N3) all bore no –OH, =NH group,
3
3
.2. Chemosensing of fluoride
therefore which seemingly can not form hydrogen bonding with
fluoride. However, the keto-enol tautomerism of ethyl acetoacetate
provided a valuable reference [43]. Similarly, the diketone struc-
ture in N1, N2, N3 can also activate methylene proton sufficiently,
showing the tendency of keto-enol tautomerism (Fig. 4). In the
presence of fluoride, the tendency of keto-enol tautomerism was
enhanced due to the hydrogen bonding between fluoride and the
new formed hydroxy. The similar keto-enol tautomerism induced
by solvent polarity has been reported and proved [31]. The conju-
gate system of naphthalimides was extended by the transform of
keto-enol. The significant absorption change centred at 560 nm
revealed the structure transform of N1, N2, N3 (Fig. 1).
.2.1. Spectral characteristics
According to the absorption spectrum, the three probes N1, N2,
N3, showed a similar response to fluoride. As shown in Figue1a, b,
c, the original absorption of N1, N2, N3 only appeared in the non-
visible region (250–400 nm). When different equivalent fluoride
The different sensitive of three probes (Fig. 1 d, e, f) can also be
explained by hydrogen bonding. In the sensing process, N3 was not
assisted by an intramolecular hydrogen bond, N2 was assisted by
the hydrogen bond between the hydroxyl group and the benzene
ring, N1 was also assisted by a hydrogen bond between the hydro-
xyl group and pyridinium nitrogen (Fig. 4 a, b, c). Furthermore, the
hydrogen bond between the hydroxyl group and pyridinium nitro-
gen is more robust than that between the hydroxyl and benzene
rings [44,45]. Therefore, the assistance of different intramolecular
hydrogen bonds made the sensitivity of probes different.
À
The binding stoichiometry between N1, N2, N3 and F were
Scheme 1. The synthesis route of N1, N2, N3.
investigated through Job’s plot experiments (Fig. 5). The absor-
3

X. Yan, H. Lan, Y. Li et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 254 (2021) 119674
Fig. 1. (a, b, c) Absorption and colour change of N1 (a), N2 (b), N3 (c) in present fluoride; (d, e, f) the absorbance change of N1 (d), N2 (e), N3 (f) at 560 nm with the addition of
À5
different equipment fluoride(probes in DMSO, 10 M).
À
bance at 560 nm of N1, N2, N3 and F mixture at 560 nm were
To identify the sensing mechanism, the HNMR and Dept 135
experiments were carried out. The methylene proton signal peaks
of N1, N2, N3 located at around 6.0 ppm. In the presence of fluo-
ride, the signal peaks around 6.0 ppm disappeared (Fig. 6 a, b, c).
The keto form of N1, N2, N3 were transformed to the enol form
induced by fluoride and formed hydrogen bonding. The methylene
carbon Dept 135 signal of N1, N2, N3 located at around 40.0 ppm.
In the presence of fluoride, the signal peaks around 40.0 ppm dis-
appeared (Fig. 6 d, e, f). The transform from tertiary carbon to a
quaternary carbon proved the change of carbon structure.
À
recorded. The molar fraction of F with a constant total concentra-
tion of N1, N2, N3 and F (20 mmol) varied from 0 to 1. The absor-
bance at 560 nm reached the maximum value, when the molar
À
fraction was 0.5 for N1, N2, N3, indicating the formation of 1:1
À
complex between the N1, N2, N3 and F . On the basis of 1:1 stoi-
chiometry and UV–vis titration data, the association constant of
À
3
N1, N2, N3 with F ion in DMSO was found to be 3.629 Â 10
À1
3
À1
3
À1
M
, 1.879 Â 10 M , 5.946 Â 10
M
according to the linear
Benesi-Hildebrand expression (Figs. s12–14).
4

X. Yan, H. Lan, Y. Li et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 254 (2021) 119674
À5
Fig. 2. (a, b, c) the absorption changes at 560 nm of N1 (a), N2 (b), N3 (c) in present different anion; Inset: the absorption spectrum changes of N1, N2, N3 (10 M, DMSO) in
À5
present different anion (10 M, DMSO).
Fig. 3. The absorption changes at 470 nm of N1 (a), N2 (b), N3 (c) at different pH values.
À
À
À
To further explore the binding mechanism in detail, the infrared
spectra of compound N1, N2, and N3 and its combined complex
N1 + F , N2 + F and N3 + F were measured. The infrared spec-
À
À
À
trum of N1, N2, N3 and N1 + F , N2 + F , N3 + F were overlaid
and compared (Figure S11). Two C@O stretching vibration peaks
at 1723 cm and 1650 cm was obvious recorded in the free
N1, N2, N3 molecular. After the keto form of N1, N2, N3 was trans-
formed to the enol form, one of the two C@O group stretching
vibration peaks disappeared.
À1
À1
3.3. Chemosensing of water
Three probes combined with fluoride ions to form three com-
plex N1-enol-F, N2-enol-F, N3-enol-F (Fig. 4). The three com-
plexes would recover its initial states in present trace water.
Therefore, these probes based on hydrogen bonding were easily
disturbed by water and could only work in the organic solvent
[
46]. However, the resultant complex would be an excellent sec-
ondary probe for trace water. When quantitative water was added
to N1-enol-F, N2-enol-F, N3-enol-F solution, the significant
absorption peak centred at 560 nm gradually decreased in the vis-
ible region (400–700 nm), and finally recovered the initial states
N1, N2 and N3 (Fig. 7 a, b, c). As shown in Fig. 6d, e, f, the absorp-
tion intensity change at 560 nm of N1-enol-F, N2-enol-F, N3-enol-
F versus the concentration of water showed different linear rela-
tionships, and their calibration curve slope was 0.0326 (N1enol-
F), 0.0359 (N2-enol-F), 0.0367(N3-enol-F). The detection limits
of N1-enol-F, N2-enol-F, N3-enol-F were calculated to be
À7
0
.05737 (wt%), 0.05210 (wt%), 1.1 Â 10 M (0.04828) according
to the equation: 3r/b (r: the standard deviation of 20 blank sam-
ples (10 mol/L of N1-enol-F, N2-enol-F, N3-enol-F), b: calibration
curve slope of N1-enol-F, N2-enol-F, N3-enol-F) [47].
3.4. Fingerprint imaging
The most sensitive one (N3-enol-F) of the three probes were
Fig. 4. The proposed binding mechanism of N1, N2, N3 with fluoride.
incorporated with a test paper for fingerprint imaging. Firstly,
5

X. Yan, H. Lan, Y. Li et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 254 (2021) 119674
À
À
À
Fig. 5. Job’s plot (a, b, c) of the binding between probe (N1, N2, N3) and F . Absorbance at 560 nm was plotted as a function of the molar ratio [F ]/([probe] + [F ]) (the total
concentration of probe and F were 20 mmol/L).
À
À
À
À
6
Fig. 6. HNMR spectrum (a, b, c) and Dept 135 spectrum (d, e, f) of N1, N2, N3 and N1 + F , N2 + F , N3 + F in DMSO d .
Fig. 7. (a, b, c) Absorption change of N1-enol-F (a), N2-enol-F (b), N3-enol-F (c) in present water; (d, e, f) the absorbance change of N1-enol-F (d), N2-enol-F (e), N3-enol-F
À5
(
f) at 560 nm with the addition of different equipment fluoride(probes in DMSO, 10 M).
6

X. Yan, H. Lan, Y. Li et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 254 (2021) 119674
References
[
1] (a) Y. Wu, S. Liu, Z. Chen, J. Zhao, Synthesis and properties of cardo-type
polyimides containing hydroxyl groups for application in specific detection of
fluoride ion, Dyes Pigments 173 (2020) 107924;
(
b) A. Mondal, S. Nag, P. Banerjee, Coumarin functionalized molecular
scaffolds for the effectual detection of hazardous fluoride and cyanide,
Dalton T 2 (2021) 429–451;
(
c) M. Li, Z. Liu, H. Wang, A.C. Sedgwick, J.E. Gardiner, S.D. Bull, H. Xiao, T.D.
James, Dual-function cellulose composites for fluorescence detection and
removal of fluoride, Dyes Pigments (2018) 669–675;
Fig. 8. (a) Test paper incorporated with N3-enol-F (b) fingerprint images on the
test paper.
(d) C.M. Lopez-Alled, A. Sanchez-Fernandez, K.J. Edler, A.C. Sedgwick, S.D. Bull,
C.L. McMullin, G. Kociok-Kohn, T.D. James, J. Wenk, S.E. Lewis, Azulene-
boronate esters: colorimetric indicators for fluoride in drinking water, Chem.
Commun. 93 (2017) 12580–12583.
[
2] M. Kleerekoper, The role of fluoride in the prevention of osteoporosis,
Endocrinol. Metab. Clin. N. Am. 27 (1998) 441–452.
the water sensing process of the probe N3-enol-F in dry acetoni-
trile was explored. And then, test paper incorporated with N3-F
was prepared by using qualitative filter paper. The filter paper
[3] P. Singh, M. Barjatiya, S. Dhing, R. Bhatnagar, S. Kothari, V. Dhar, Evidence
suggesting that high intake of fluoride provokes nephrolithiasis in tribal
populations, Urol. Res. 29 (2001) 238e244.
À2
was immersed in the 10 ml solution of N3 (10 M) with an excess
[
4] X. Jin, J. Gao, T. Wang, W. Feng, R. Li, P. Xie, L. Si, H. Zhou, X. Zhang, Rhodol-
based fluorescent probes for the detection of fluoride ion and its application in
water, tea and live animal imaging, Spectrochim. Acta Part A: Mol. Biomol.
Spectrosc. (2020) 117467.
5] (a) R. Wang, Y. Ma, J. Zhao, A. Zhang, S. Yang, H. Shen, G. Li, Z. Shi, Novel
hydroxyl-substituted perylene-3,4,9,10-tetracarboxylic acid diimides for
selective recognition of fluoride, Sens. Actuators, B (2018) 719–726;
of Fluoride ion (0.1 M) in dry acetonitrile for 5 min. The wet paper
was then allowed to dry using a hot air gun. This deep purple col-
our paper incorporated with N3-F was used for fingerprint imag-
ing. Due to fingertips produced sweat [48], when a fingertip was
gently placed on the N3-enol-F incorporated test paper, the clear
impression of the fingertip appeared in the paper (Fig. 8). Com-
pared with inking methods or digital scanners, test paper incorpo-
rated N3-enol-F was candidate reliable and cheap technique for
fingerprint imaging [49].
[
(
b) A. Mondal, A. Hazra, J. Chakrabarty, N.C. Murmu, P. Banerjee, A harmonized
applied and theoretical exploration for nanomolar level recognition of perilous
FÀ and CNÀ by multichannel chemosensor: proposition of Hg2+-mediated
logic gate imitator, Chemistryselect 38 (2020) 11976–11985;
(
c) S. Xu, X. Sun, H. Ge, R.L. Arrowsmith, J.S. Fossey, S.I. Pascu, Y. Jiang, T.D.
James, Synthesis and evaluation of a boronate-tagged 1,8-naphthalimide probe
for fluoride recognition, Org. Biomol. Chem. 14 (2015) 4143–4148.
6] (a) Y. Wu, X. Peng, J. Fan, S. Gao, M. Tian, J. Zhao, S. Sun, Fluorescence sensing
of anions based on inhibition of excited-state intramolecular proton transfer, J.
Org. Chem. 1 (2007) 62–70;
[
4
. Conclusions
(
b) A. Mondal, A.R. Chowdhury, S. Bhuyan, S.K. Mukhopadhyay, P. Banerjee, A
In summary, three colourimetric fluoride and trace water
simple urea-based multianalyte and multichannel chemosensor for the
selective detection of F-, Hg2+ and Cu2+ in solution and cells and the
extraction of Hg2+ and Cu2+ from real water sources: a logic gate mimic
ensemble, Dalton T 13 (2019) 4375–4386.
7] V. Thiagarajan, P. Ramamurthy, D. Thirumalai, V.T. Ramakrishnan, A novel
colorimetric and fluorescent chemosensor for anions involving PET and ICT
pathways, Org. Lett. 4 (2005) 657–660.
probes based on tautomerization of naphthalimide were designed
and synthesized. They all showed the remarkable colour change
from colourless to purple in present fluoride, and the colour
returned to colourless in present trace water. The chemosensing
process was also applied to fingerprint imaging. The fantastic
structure change of the three probes in the sensing process was
proved by NMR and infrared spectra. The sensing model of the
three molecular provided a new strategy for design high-contrast
probe.
[
[8] (a) P. Rajamalli, E. Prasad, Low molecular weight fluorescent organogel for
fluoride ion detection, Org. Lett. 14 (2011) 3714–3717;
(
b) A.R. Chowdhury, A. Mondal, B.G. Roy, J.C.K. Bose, S. Mukhopadhyay, P.
Banerjee, Hydrazine functionalized probes for chromogenic and fluorescent
ratiometric sensing of pH and F-: experimental and DFT studies, Photoch.
Photobio. Sci. 11 (2017) 1654–1663.
[
9] (a) C. Saravanan, S. Easwaramoorthi, C.Y. Hsiow, K. Wang, M. Hayashi, L.
Wang, Benzoselenadiazole fluorescent probes–near-IR optical and ratiometric
fluorescence sensor for fluoride ion, Org. Lett. 2 (2014) 354–357;
CRediT authorship contribution statement
(
b) P. Ghosh, S. Paul, D. Dey, S. Jana, B.G. Roy, S.K. Mukhopadhyay, P. Banerjee,
Xia Yan: Conceptualization, Methodology, Validation, Investi-
gation. Haichuang Lan: Writing - review & editing. Yang Li: Visu-
alization. Xiaojing Yan: Software. Qilin Xing: Formal analysis.
Wen Wang: Investigation. Jiayu Zhang: Software. Shuzhang Xiao:
Resources.
Engineering bio-molecular device with biocompatible sensor via symmetric
encryption–decryption of spectroscopic signals towards FÀ detection and Zn2
+
1
recognition by the imine hydrolysis pathway, New J. Chem. 35 (2020)
5251–15259.
[
10] G. Sivaraman, D. Chellappa, Rhodamine based sensor for naked-eye detection
and live cell imaging of fluoride ions, J. Mater. Chem. B 42 (2013) 5768–5772.
11] X. Yong, M. Su, W. Wang, Y. Yan, J. Qu, R. Liu, A naked-eye chemosensor for
fluoride ions: a selective easy-to-prepare test paper, Org. Biomol. Chem. 14
(2013) 2254–2257.
[
Declaration of Competing Interest
[
12] Q. Wang, Y. Xie, Y. Ding, X. Li, W. Zhu, Colorimetric fluoride sensors based on
deprotonation of pyrrole-hemiquinone compounds, Chem. Commun. (Camb.)
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared
to influence the work reported in this paper.
2
1 (2010) 3669–3671.
[13] X. Zheng, W. Zhu, D. Liu, H. Ai, Y. Huang, Z. Lu, Highly selective colorimetric/
fluorometric dual-channel fluoride ion probe, and its capability of
differentiating cancer cells, ACS. Appl. Mater. Interfaces. 11 (2014) 7996–8000.
[
14] (a) M.S. Yuan, Q. Wang, W. Wang, D.E. Wang, J. Wang, J. Wang, Truxene-cored
pi-expanded triarylborane dyes as single- and two-photon fluorescent probes
for fluoride, Analyst. 6 (2014) 1541–1549;
Acknowledgements
(
b) X. Wu, X. Chen, B. Song, Y. Huang, W. Ouyang, Z. Li, T.D. James, Y. Jiang,
This work was financially supported by Hubei Provincial Natu-
ral Science Foundation of China (2017CFB219), China Three Gorges
University (1910103) and National Natural Science Foundation of
China (21472111).
Direct sensing of fluoride in aqueous solutions using a boronic acid based
sensor, Chem. Commun. 90 (2014) 13987–13989;
(
Ratiometric fluorescence sensing of fluoride ions by an asymmetric bidentate
receptor containing a boronic acid and imidazolium group, Eur. J. Org. Chem.
1
c) Z. Xu, S.K. Kim, S.J. Han, C. Lee, G. Kociok-Kohn, T.D. James, J. Yoon,
8 (2009) 3058–3065.
[
15] A. Roy, D. Kand, T. Saha, P. Talukdar, A cascade reaction based fluorescent
probe for rapid and selective fluoride ion detection, Chem. Commun. (Camb.)
Appendix A. Supplementary material
41 (2014) 5510–5513.
[
16] M. Jo, J. Lim, O.S. Miljanic, Selective and sensitive fluoride detection through
alkyne cruciform desilylation, Org. Lett. 14 (2013) 3518–3521.
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.saa.2021.119674.
7

X. Yan, H. Lan, Y. Li et al.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 254 (2021) 119674
[
17] H.S. Jung, P. Verwilst, W.Y. Kim, J.S. Kim, Fluorescent and colourimetric sensors
for the detection of humidity or water content, Chem. Soc. Rev. 5 (2016) 1242–
[33] S.Y. Xu, X. Sun, H. Ge, R.L. Arrowsmith, J.S. Fossey, S.I. Pascu, Y.B. Jiang, T.D.
James, Synthesis and evaluation of
a boronate-tagged 1,8-naphthalimide
1
256.
18] M. Cigá nˇ , M. Horváth, J. Filo, K. Jakusová, J. Donovalová, V. Garaj, A. Gáplovsk y´ ,
-Dialkylaminocoumarin oximates: small molecule fluorescent ‘‘turn-on”
probe for fluoride recognition, Org. Biomol. Chem. 14 (2015) 4143–4148.
[34] Z. Wu, X. Tang, Visualizing fluoride ion in mitochondria and lysosome of living
cells and in living mice with positively charged ratiometric probes, Anal.
Chem. 17 (2015) 8613–8617.
[
7
chemosensors for low-level water content in aprotic organic solvents,
Molecules 8 (2017) 1340.
[35] S.A. Yoon, J.H. Oh, S.K. Kim, M.H. Lee, Water-sensitive ratiometric fluorescent
probes and application to test strip for rapid and reversible detection of water,
Dyes Pigments (2019) 421–428.
[
19] M. Cigá nˇ , J. Gašpar, K. Gáplovská, J. Holekšiová, K. Jakusová, J. Donovalová, V.
Garaj, H. Stankovi cˇ ová, Coumarin phenylsemicarbazones: sensitive
colourimetric and fluorescent ‘‘turn-on” chemosensors for low-level water
content in aprotic organic solvents, New J. Chem. 10 (2016) 8946–8953.
20] P. Kumar, A. Ghosh, D.A. Jose, A simple colourimetric sensor for the detection
of moisture in organic solvents and building materials: applications in
rewritable paper and fingerprint imaging, Analyst. 2 (2019) 594–601.
21] G. Alberti, C. Zanoni, L.R. Magnaghi, R. Biesuz, Low-cost, disposable
colourimetric sensors for metal ions detection, J. Anal. Sci. Technol. 301
[36] P. Yadav, M. Kumari, Y. Jain, M. Agarwal, R. Gupta, Antipyrine based Schiff’s
base as a reversible fluorescence turn ‘‘off-on-off” chemosensor for sequential
+
À
[
[
[
recognition of Al3 and F ions: a theoretical and experimental perspective,
Spectrochim. Acta Part A: Mol. Biomol. Spectrosc. (2020) 117596.
[37] V. Vijayakumar, A. Karuppusamy, P. Kannan, P. Nagaraaj, Synthesis of novel 2-
((2-(benzothiazol-2-yl)hydrazono)methyl)naphthalen-1-ol (NBS) and its
selective sensing of fluoride ions, Chem. Phys. Lett. 136891 (2020).
[38] H. Lan, B. Liu, G. Lv, Z. Li, X. Yu, K. Liu, X. Cao, H. Yang, S. Yang, T. Yi, Dual-
channel fluorescence ‘‘turn on” probe for Cu2 , Sens. Actuators, B (2012) 811–
816.
(
2020) 1.
+
22] (a) V. Moradi, E.A. Caws, P.M. Wild, H.L. Buckley,
A
simple method for
detection of low concentrations of fluoride in drinking water, Sens. Actuators,
A 111684 (2020) 111684;
[39] Y. Mednykh, Y. Manaev, V. Volchkov, B. Uzhinov, Influence of the configuration
of the amine nitrogen atom on the efficiency of fluorescence of 4-
aminonaphthalimide derivatives, Russ. J. Gen. Chem. 11 (2004) 1728–1733.
[40] Z. Li, Q. Yang, R. Chang, G. Ma, M. Chen, W. Zhang, N-Heteroaryl-1,8-
naphthalimide fluorescent sensor for water: molecular design, synthesis and
properties, Dyes Pigments 3 (2011) 307–314.
(
b) T. Nishimura, S. Xu, Y. Jiang, J.S. Fossey, K. Sakurai, S.D. Bull, T.D. James, A
simple visual sensor with the potential for determining the concentration of
fluoride in water at environmentally significant levels, Chem. Commun. 5
(
2013) 478–480.
[
23] Y. Zhou, J. Yoon, Recent progress in fluorescent and colorimetric chemosensors
for detection of amino acids, Chem. Soc. Rev. 1 (2012) 52–67.
[41] X. Zheng, W. Zhu, D. Liu, H. Ai, Y. Huang, Z. Lu, Highly selective colorimetric/
fluorometric dual-channel fluoride ion probe, and its capability of
differentiating cancer cells, Acs. Appl. Mater. Inter. 11 (2014) 7996–8000.
[42] C. Yu, L. Chen, J. Zhang, J. Li, P. Liu, W. Wang, B. Yan, Off-on based fluorescent
chemosensor for Cu2 in aqueous media and living cells, Talanta 3 (2011)
1627–1633.
[
24] H. Ahmadpour-Yazdi, M.R. Hormozi-Nezhad, A.R. Abadi, M.H. Sanati, B.
Kazemi, Colourimetric-based method for the diagnosis of spinal muscular
atrophy using gold nanoprobes, IET Nanobiotechnol. 1 (2015) 5–10.
25] C.T.M.B. Tom, J.E. Crellin, H.F. Motiwala, M.B. Stone, D. Davda, W. Walker, Y.
Kuo, J.L. Hernandez, K.J. Labby, L. Gomez-Rodriguez, P.M. Jenkins, S.L. Veatch,
B.R. Martin, Chemoselective ratiometric imaging of protein S-sulfenylation,
Chem. Commun. 53 (2017) 7385–7388.
26] (a) L. Liu, F. Dan, W. Liu, X. Lu, Y. Han, S. Xiao and H. Lan, A high-contrast
colorimetric and fluorescent probe for Cu2+ based on benzimidazole-
quinoline, Sens. Actuators B: Chem. (2017) 445–450. (b) A journey towards
salivary fluoride level detection by suitable low cost chemosensor: from
molecule to product, Chem. Rec. 10 (2019) 2119–2129.
+
[
[43] M. Folkendt Michael, E. Weiss-Lopez Boris, J. Paul Chauvel, N.S. True, Gas-
phase 1H NMR studies of keto-enol tautomerism of acetylacetone, methyl
acetoacetate, and ethyl acetoacetate, J. Phys. Chem. 89 (1985) 3347.
[44] J. Sartorius, H. Schneider, A general scheme based on empirical increments for
the prediction of hydrogen-bond associations of nucleobases and of synthetic
host-guest complexes, Chem. - A Eur. J. 11 (1996) 1446–1452.
[45] M. Sun, Control of structure and photophysical properties by protonation and
subsequent intramolecular hydrogen bonding, J. Chem. Phys. 5 (2006) 54903.
[46] Y. Feng, X. Li, H. Ma, Z. Zhang, M. Zhang, S. Hao, A simple fluorescent film probe
for the detection of fluoride anion in organic solution, Dyes Pigments (2018)
200–205.
[
[
27] T.P. Martyanov, L.S. Klimenko, V.I. Kozlovskiy, E.N. Ushakov, Tautomeric
chromoionophores derived from 1-aryloxyanthraquinones and 4-
aminobenzo-15-crown-5 ether: sandwich complex formation enhanced by
interchromophoric interactions, Tetrahedron 6 (2017) 681–691.
[
[
[
28] G. Storch, M.J. Spallek, F. Rominger, O. Trapp, Tautomerization-mediated
molecular switching between six- and seven-membered rings stabilized by
hydrogen bonding, Chem. - A Eur. J. 24 (2015) 8939–8945.
29] A.R. Todorov, M. Nieger, J. Helaja, Tautomeric switching and metal-cation
sensing of ligand-equipped 4-hydroxy-/4-oxo-1,4-dihydroquinolines, Chem. -
A Eur. J. 23 (2012) 7269–7277.
30] V. Vetokhina, J. Nowacki, M. Pietrzak, M.F. Rode, A.L. Sobolewski, J. Waluk, J.
Herbich, 7-Hydroxyquinoline-8-carbaldehydes. 1. Ground- and excited-state
long-range prototropic tautomerization, J. Phys. Chem. A 38 (2013) 9127–
[47] J. Wang, Y. Pei, S. Ren, M. Yan, W. Luo, B. Zhang, Q. Li, Two 8-hydroxyquinoline-
based fluorescent chemosensors for ultra-fast and sensitive detection of water
content in strong polar organic solvents with large Stokes shifts, Spectrochim.
Acta Part A: Mol. Biomol. Spectrosc. (2020) 117956.
[48] S.A. Yoon, J.H. Oh, S.K. Kim, M.H. Lee, Water-sensitive ratiometric fluorescent
probes and application to test strip for rapid and reversible detection of water,
Dyes Pigments (2019) 421–428.
[49] (a) M. Cigá nˇ , M. Horváth, J. Filo, K. Jakusová, J. Donovalová, V. Garaj, A.
Gáplovsk y´ , 7-Dialkylaminocoumarin oximates: small molecule fluorescent
‘‘turn-on” chemosensors for low-level water content in aprotic organic
solvents, Molecules 8 (2017) 1340;
9
146.
[
31] H. Lan, Q. Li, Y. Li, S. Xiao, Y. Li, X. Yan, S. Yuan, P. Zhu, Solvent-controlled
tautomerism of malononitrile-naphthalimide via intramolecular proton
transfer, Dyes Pigments (2018) 121–125.
(b) J. Lian, F. Meng, W. Wang, Z. Zhang, Recent trends in fluorescent organic
materials for latent fingerprint imaging, Front. Chem. 8 (2020) 1–8.
[
32] X. Qian, Y. Xiao, Y. Xu, X. Guo, J. Qian, W. Zhu, ‘‘Alive” dyes as fluorescent
sensors: fluorophore, mechanism, receptor and images in living cells, Chem.
Commun. 35 (2010) 6418–6436.
8