One-step construction of a novel AIE probe based on diaminomaleonitrile and its application in double-detection of hypochlorites and formaldehyde gas

Article abstract of DOI:10.1039/d1nj00932j

As the environmental residues of formaldehyde and hypochlorites are very harmful to human health, a new simple and efficient aggregation-induced emission probe based on diaminomaleonitrile was designed and applied in the independent detection of hypochlorites and formaldehyde. The probe shows high selectivity and anti-interference ability against other potential competitive substances. ClO- promotes the oxidized splitting of CN in the probe, and induces evident color changes visible to the naked eye together with quenched fluorescence. The detection of ClO- by this probe was fast, sensitive, and visible to the naked eye. The detection limit of the probe to ClO- in the range of 0.70-20 μM is 18 nM. Through the condensation mechanism and with amine as the binding site of formaldehyde, the exposed amino group in the probe structure responds sensitively and efficiently to formaldehyde. The probe can effectively monitor 0.50-25 μM formaldehyde in aqueous solutions, with a detection limit as low as 42 nM. A portable solid sensor-a formaldehyde detection plate was built by directly covering the probe on a thin-layer chromatography plate. Thereby, formaldehyde gas can be effectively and sensitively detected, which offers a clue for developing solid-state formaldehyde-detection plates. The high experimental recovery rates prove that this new probe is highly promising in hypochlorite detection in the real water environment.

Full text of DOI:10.1039/d1nj00932j

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One-step construction of a novel AIE probe based
on diaminomaleonitrile and its application in
double-detection of hypochlorites and
formaldehyde gas†
Cite this: New J. Chem., 2021,
45, 8155
Xiaoye Wen,‡ Li Yan‡ and Zhefeng Fan
*
As the environmental residues of formaldehyde and hypochlorites are very harmful to human health, a
new simple and efficient aggregation-induced emission probe based on diaminomaleonitrile was
designed and applied in the independent detection of hypochlorites and formaldehyde. The probe
ꢀ
shows high selectivity and anti-interference ability against other potential competitive substances. ClO
promotes the oxidized splitting of CQN in the probe, and induces evident color changes visible to the
ꢀ
naked eye together with quenched fluorescence. The detection of ClO by this probe was fast,
ꢀ
sensitive, and visible to the naked eye. The detection limit of the probe to ClO in the range of
0.70–20 mM is 18 nM. Through the condensation mechanism and with amine as the binding site of
formaldehyde, the exposed amino group in the probe structure responds sensitively and efficiently to
formaldehyde. The probe can effectively monitor 0.50–25 mM formaldehyde in aqueous solutions, with
a detection limit as low as 42 nM. A portable solid sensor – a formaldehyde detection plate was built by
directly covering the probe on a thin-layer chromatography plate. Thereby, formaldehyde gas can be
effectively and sensitively detected, which offers a clue for developing solid-state formaldehyde-
detection plates. The high experimental recovery rates prove that this new probe is highly promising in
hypochlorite detection in the real water environment.
Received 24th February 2021,
Accepted 7th April 2021
DOI: 10.1039/d1nj00932j
rsc.li/njc
detect signals through the simultaneous or sequential action of
1
. Introduction
11,12
more than one analyte.
On the contrary, the analytes in OR
Fluorescent probes have gradually been used as powerful tools multi-site fluorescent probes can independently bind with the
to track small molecules in the environment and life systems, reaction sites and are mutually non-interfering, and thus possess
1
3–15
owing to their avoidance of sample pretreatment, low operational higher accuracy and sensitivity.
complexity, ease of visualization, fast response, high selectivity, multiple detection sites are prospective methods for simultaneous
In all, fluorescent probes with
1–4
and high sensitivity. However, the existing fluorescent probes detection of multiple chemical substances.
are monofunctional and only have single binding site targeting a
Hypochlorites are used in various fields, such as bleachers
specific analytical substance, and thus are severely restricted in (paper plants), disinfectants (tap water, swimming pools) and
1
6–18
practical applications. Research on multifunctional fluorescent cleaners.
The inhalation of trace hypochlorites can injure
probes with higher detection efficiency and lower costs is critical airway mucosas, leading to cough, asthma or even dyspnea, and
in developing and constructing fluorescence detection systems the intake of high-dose hypochlorites can result in severe acute
5–7
19,20
and is of very high significance and values. Double- or multi- symptoms, such as pneumonedema.
Hence, prevention of
analyte responsive fluorescent probes have been designed to build accidental leakage of hypochlorites and establishment of fast
probes with multiple reaction sites and to identify different and sensitive hypochlorite detection methods is extremely
substances through the analysis of different reaction mechanisms. important. So far, fluorescent probes have been prepared and
ꢀ
Double-analyte fluorescent probes can be mainly divided into AND used in ClO detection, but their mechanisms are mostly based
8–10
ꢀ
logics and OR logics.
The AND logic fluorescent probes can on the oxidizing reaction of ClO with different functional
2
1–28
groups (e.g. double bonds, ethers, sulfides, and oxime).
The practical applications of these probes are mostly limited by
the delayed and monotonous response to ClO , tedious synthesis
Department of Chemistry, Shanxi Normal University, Linfen 041004, China.
E-mail: zhefengfan@126.com
ꢀ
steps, low quantum efficiency, low water solubility, low biocom-
patibility, and subjection to interference by other active oxygen
†
‡
Electronic supplementary information (ESI) available. See DOI: 10.1039/d1nj00932j
Xiaoye Wen and Li Yan contributed equally to this work.
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Scheme 1 Mechanism of the probe in detecting formaldehyde gas and hypochlorites.
29
substances. Hence, new fluorescent probes are needed urgently as the solutions obviously changed in color so that the exis-
ꢀ
to relieve the above limitations. Formaldehyde (FA, HCHO) is a tence of ClO in the environment can be effectively detected in
colorless, combustible and suffocating chemical with high irrit- time. Moreover, the fluorescence spectral data can be used in
ꢀ
ability, and is a ubiquitous toxin and carcinogen in the environ- further quantitative analysis of environmental ClO . Since AIE
ment. Thus, residual FA in the environment and food can molecules show strong fluorescence under the solid-state, we
3
0,31
threaten human health.
The existing FA-responsive probes prepared an FA gas-testing plate and thereby successfully
32
are mainly based on two reaction mechanisms: (a) FA and detected gas-state FA. The one-step synthesis method used in
methyl-allyl-amine undergo an aza-Cope rearrangement reaction this study is simple, cheap, biocompatible, and can be used in a
to alter fluorescent signals;
–NH ) or hydrazine (–NHNH
to alter fluorescent signals.
3
3–36
(b) FA and the amino group 99% water medium. Hence, the new probe is prospective in
(
2
2
) undergo a condensation reaction practical applications and offers a new clue for constructing
3
7–39
Under physiological conditions, convenient double-site fluorescent probes (Scheme 1).
however, the probes based on the aza-Cope rearrangement reac-
tion mostly respond very slowly to FA and usually take 2–3 h to
reach the ideal fluorescent signals. In comparison, the fluores- 2. Experimental section
cent probes based on FA and hydrazine or amine reaction
respond much faster.
2.1. Materials and instruments
The reagents used in this experiment were purchased directly
Aladdin Co Ltd; China) and used without further purification.
Aggregation-induced emission (AIE) probes can solve the
defects of aggregation concentration quenching in common
luminescent materials, and are widely applied owing to the
convenience of structural modification and fluorescence wave-
(
Ultrapure water with a resistivity of 18.2 MO cm was used in the
experiment. The UV absorption spectrum was recorded on a
UV-visible spectrophotometer (TU-1901; Purkinje General
Instrument Co Ltd, China), the fluorescence spectrum was
measured using a fluorospectrophotometer (LS55; PerkinEl-
mer, USA). The NMR data were recorded on a magnetic
resonance spectrometer (AVANCE III HD; Bruker), MS spectra
were recorded on HRMS (Ultraflex MALDI-TOF/TOF, Bruker
Daltonics, Germany). The surface morphology and particle size
distribution were obtained using SEM (JSM-7500 F; Japan) and
4
0–42
length adjustment.
Our team has made many efforts to
build structurally simple fluorescence sensors with high sensi-
tivity, efficiency and practical values, and has constructed a
series of AIE fluorescent probes from Schiff base derivatives.
Moreover, through the modification of fluorescence molecular
structures by introducing different groups, we have managed to
adjust molecular energy gaps, forming fluorescent probes with
emission at different wavelengths, and applied in the detection
4
3–46 a particle size analyzer (Zetasizer Nano ZS90; Malvern Panaly-
tical, UK), respectively. The infrared data were measured using
of single analytes or continuous detection of two analytes.
Recently, OR logic fluorescent probes have displayed many
advantages and thus are increasingly needed and applied. In
this regard, here we experimentally designed a novel simple
double-site AIE fluorescent probe based on diaminomaleoni-
trile (DAMN). In brief, the convenient detection of hypochlor-
ites and FA was realized by introducing different binding sites
an FT-IR Spectrometer (Varian-660-IR; USA). The buffer
solution (Tris–HCl) was prepared using a pH meter (PHS-3E;
China).
2.2. Synthesis steps
(
2
CQN, –NH ) in the structure of the probe. The response of the The one-step synthetic route of the probe is illustrated in Fig. 1.
ꢀ
probe to ClO can be observed by the naked eye under sunlight In brief, diaminomaleonitrile (DAMN) (5.0 mmol, 0.54 g) was
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Fig. 1 Synthetic route of the probe.
dissolved in anhydrous ethanol (25 mL), and then salicylalde- zone was the detection area. Formaldehyde solutions at different
hyde (1.0 equiv.) was dripped dropwise. The reaction mixture concentrations were added in bottles, and the detection plate was
was stirred at room temperature for 7 days, forming earthy rapidly hung in each bottle. The bottles were kept at 60 1C for 1 h,
yellow precipitates, which were washed in anhydrous ethanol and after the FA gas was fully volatilized, the detection plates
and vacuum-dried. After that, the khaki target compound A were taken out. The changes in fluorescent colors in the detection
1
(
(
0.87 g) was obtained, with a yield rate of 82.04%. H NMR plates were observed under an ultraviolet lamp at 365 nm.
ꢀ
600 MHz, DMSO-d ) d (ppm) (Fig. S1a, ESI†): 10.42 (1H, s),
The probe was applied for ClO detection in real water
6
8
7
.61 (1H, s), 8.05 (1H, dd, J7.8), 7.85 (2H, s), 7.41–7.30 (1H, m), samples, including drinking water (from a direct drinking
1
3
.16–6.77 (2H, m). C NMR (150 MHz, DMSO-d
6
) d (ppm) system in a teaching building), lake water (from a lake in a campus),
(Fig. S1b, ESI†): 158.61, 153.31, 133.67, 129.37, 126.51, 121.73, and tap water (from a laboratory). Lake water samples were filtered
1
19.89, 116.89, 114.73, 103.91. HRMS (ESI) (Fig. S2, ESI†): m/z and diluted first. The actual water sample detection was performed
+
calculated for C11
H
8
N
4
O: 212.07; found [M + H] : 213.08.
by real-time sampling and real-time detection, which ensured the
ꢀ
valid ClO concentrations in the water samples.
2.3. Common methods of spectral measurement
The compound was dissolved in dimethyl sulfoxide (DMSO) to
form the reserve probe solution (1.0 mM). The concentration of
3
. Results and discussion
other inorganic substances was 10 mM. The excitation wavelength 3.1. Photophysical properties of the probe
for fluorescent spectrometry was 390 nm, and the excitation and
emission slit widths were 5 and 20 nm, respectively. The fluores-
cence spectra and UV absorption spectra of the probe in DMSO–
The probe can be dissolved in common organic solvents, there
was almost no emission in these solvents, but it showed a
strong emission in 1% DMSO aqueous solution (Fig. 2a). The
fluorescence emission spectra and UV absorption spectra of the
probe in DMSO/H O mixtures were recorded, and thereby the
2
AIE of the probe was determined. The emission spectra of the
2 w
H O mixtures with different water fraction volumes (f = 0–99%)
were recorded, and thereby the AIE properties of the probe were
ꢀ
determined. The response of the probe to FA/ClO was monitored
2
in DMSO/H O (1 : 99, v/v) at pH = 7.0 (Tris–HCl, 10 mM).
probe fell in the H O–DMSO system, and the fluorescence
2
emission spectra of the solvent in different water fraction
2
.4. Preparation of portable solid-state sensor and analysis
volumes ( f
weak fluorescence emission in pure DMSO, and the fluorescence
The detection plate was a thin-layer chromatography (TLC) emission maximized in DMSO/H O (1 : 99, v/v) (Fig. 3a). UV
plate. The TLC plate was dripped with a DMSO/H O (1: 99, v/v) absorption also proved the properties of AIE (Fig. 3b). In a good
probe solution (1 mM, pH = 7.0), and dried in a drying cabinet for solvent DMSO, C–C of probe molecules can freely rotate, and the
5 min. Then, the plate covered with the probe was observed in intramolecular rotation decreased the energy passing through
w
) were recorded. Clearly, the probe showed very
ꢀ
method of ClO in actual samples
2
2
1
an ultraviolet analyzer (365 nm), where the yellow fluorescent non-radiative channels, so the probe has no fluorescence. In the
Fig. 2 (a) The fluorescence spectra and (b) the UV absorption spectrum of the probe in different organic solvents.
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w
Fig. 3 (a) FL emission spectra of the probe; (b) UV absorption spectra of the probe in solvents with different water fraction volume (f ).
solid- or aggregation-state (poor solvents), after the molecules (x, st are the tested substance and the reference, respectively;
were excited, the hydroxyl group and nitrogen atoms formed an F, I, A, Z are quantum yield, fluorescence integral area, absor-
intramolecular hydrogen bond, which initiated the excited- bance, and solvent refractive index, respectively). The relative
state intramolecular proton transfer, so the excited-state non- quantum yields of the probe in the pure DMSO solution and
2
radiative energy decreased and the probability of radiative DMSO/H O (1 : 99, v/v) were calculated to be 3.47% and 40.67%,
4
7–51
transition increased, causing AIE.
Quinine sulfate was used respectively. These results imply that the aggregation-state
À
Á
2
2
as a reference, based on Fx ¼ FstðIx=IstÞ Z =Z ðAst=AxÞ probe has high fluorescence quantum yield and can effectively
x
st
ꢀ
Fig. 4 (a) Fluorescence intensity changes of the probe in response to ClO and FA within 30 min; (b) effects of pH on fluorescence intensity of the probe
ꢀ
response to ClO and FA; (c) fluorescence spectra of the probe after the addition of 5 equiv. of different competitive substances; (d) fluorescence of the
ꢀ
probe when the tested substances and 5 equiv. of other competitive substances coexisted (1. probe, 2. formaldehyde, 3. ClO , 4. acetaldehyde,
ꢀ ꢀ ꢀ ꢀ
5
. 1,4-phthalaldehyde, 6. 4-(diethylamino) salicylaldehyde, 7. phenol, 8. acetone, 9. glucose, 10. cysteine, 11. F , 12. NO , 13. OH , 14. HS , 15. H O , 16.
3
2
2
ꢁ
1
ꢀ
2+
2+
2 4
OH, 17. O , 18. ClO , 19. Ca , 20. Mg ).
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ꢀ
Scheme 2 Reaction mechanism between the probe and ClO .
improve precision and sensitivity. The dispersed particle sizes such reactions are usually very slow and take hours, so that
of the probe in different solvents were detected using dynamic these substances do not interfere with formaldehyde detection
light scattering (DLS, Fig. S3, ESI†). In DMSO/H O (1 : 99, v/v), within the tested 20 min. The effects of other coexisting
2
the dispersed particle size of the probe was significantly enlarged.
competitive substances were studied during the detection of
FA and ClO (Fig. 4d). Results showed that the specific detection of
ꢀ
the probe was unaffected by other potentially competitive small
molecules, active oxygen species, or ions. Though the response of
the probe to FA and ClO implied the quenching of fluorescent
3
.2. Mechanism of the probe in double-site detection of FA
ꢀ
and ClO
ꢀ
The reaction time is a critical factor that reflects the feasibility
and practicability of a probe. Firstly, changes in responsive
light intensity of the new probe with ClO and FA within
signals, the presence of FA did not largely affect the timely detection
ꢀ
of ClO , since the response time and temperature both largely
ꢀ
ꢀ
ꢀ
differed between FA and ClO . Thus, FA and ClO can be effectively
differentiated by the response time-duration of the probe.
30 min were detected. The fluorescence intensity of the probe
ꢀ
did not change with time (Fig. 4a). After the addition of ClO , the
fluorescence intensity of the probe was weakened immediately,
and fluorescence was quenched within the 30 s and minimized
within 1 min, indicating the probe rapidly responds to ClO and
is very important for real-time detection of ClO . The response
time of the probe over FA was studied, which showed the
quenching effect of the probe was optimized after 20 min. Thus,
the optimal FA detection time of the probe was set at 20 min.
Moreover, to validate the practicability of the probe over real
samples, we explored the effect of pH on the probe (Fig. 4b).
Though acidity is favorable for the rapid formation of Schiff
base compounds, the stability of Schiff bases is also affected. The
deprotonation under base conditions can improve the solubility
of the probe and weaken its aggregation and fluorescence.
After careful consideration, the detection condition of the probe
ꢀ
3.3. Fluorescence-sensing performance on ClO
ꢀ
In Scheme 2, the sensing mechanism of the probe over NaClO
ꢀ
is proposed, in which CQN is an effective recognition site of
ꢀ
ꢀ
ClO , and ClO can induce the conversion from CQN to –CHO.
When the probe molecules were under the aggregation state, the
existence of intramolecular hydrogen bond led to an excited-state
intramolecular proton transfer (ESIPT), but after the addition of
ꢀ
ClO , the intramolecular hydrogen bond was destroyed and
ESIPT was interrupted, leading to quenching of fluorescence.
The recognition mechanism of the probe was validated by high-
resolution mass spectrometry (Fig. S4, ESI†). When the probe
52
ꢀ
over formaldehyde and ClO was set at pH = 7.0 in subsequent
fluorescence detection. The optical response of the probe over
other analytes was also studied (Fig. 4c). Some potentially
competitive micromolecular substances or ions (aldehyde,
1
,4-phthalaldehyde, 4-(diethylamino)salicylaldehyde, phenol,
ꢀ
ꢀ
ꢀ
ꢀ
ꢁ
acetone, glucose, cysteine, F , NO , OH , HS , H O , OH,
3
2
2
1
ꢀ
2+
2+
O , ClO , Ca , and Mg ) were added to detect the variations
2
4
of fluorescence emission signals and the specificity of the
probe. The weak fluorescence changes of all substances can
be ignored, except acetaldehyde. Though other aldehydes can
Fig. 5 SEM images before and after the reaction between the probe and
ꢀ
also interact with the probe to form Schiff base compounds, ClO .
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molecules reacted with 1 equiv. of NaClO, the products were spectra and scanning electron microscopy (SEM) images were both
recrystallized. The mass spectrometry peaks at m/z 163.157 corre- compared before and after the binding between the probe and
+
ꢀ
ꢀ
sponded to the oxidation products [C H O + H O + Na] , indicating ClO , which further uncovered the binding between the probe and
7
6
2
ꢀ
2
that the probe effectively bound to ClO . Moreover, the infrared ClO . Several assignment peaks with obvious variations were found
ꢀ
ꢀ
Fig. 6 (a) Fluorescence spectra of the probe (20 mM) added with different concentrations of ClO (0–80 mM); inset: pictures of the probe/probe-ClO
ꢀ
under daylight lamp or 365 nm UV lamp; (b) working curves of the probe and ClO at different concentrations.
ꢀ
Table 1 Comparison of different ClO detection probes
Probe
CDs
One-step synthesis Medium (v/v)
Fluorescent color Fluorescent behavior Linear range (mM) LOD (mM) Ref.
NO
NO
PBS
Blue
On–off
Off–on
0.0–36.0
0–500
0.47
53
21
DMSO/PBS (2/8)
Orange
0.058
YES
NO
NO
PBS
Green
Blue
On–off
Off–on
Off–on
0–20
0–20
0–15
0.0082
0.012
54
20
29
PBS/DMSO (2/1)
PBS/DMSO (99/1) Blue
0.0091
NO
NO
PBS
Blue
Off–on
0–100
0–10
0.018
0.41
55
56
DMSO/H
2
O (1/99) Blue
Ratiometric
No
No
H
2
O
Green
On–off
Off–on
10–32
—
0.17
0.17
57
58
ACN/H
2
O (1/1)
Blue
No
PBS/CH
3
CN (7/3) Green
Off–on
On–off
0–8
0.12
59
YES
DMSO/H
2
O (1/99) Yellow
0.70–20
0.018
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Fig. 7 (a) Effects of temperature on the fluorescence intensity of the probe in response to FA; (b) fluorescence spectra of the probe (25 mM) added with
FA (0–50 mM); (c) Scatter plot of the probe and FA at different concentrations (0–50 mM); (d) working curve of the probe and FA at different
concentrations (0–25 mM).
ꢀ
ꢀ
in FT-IR spectra (Fig. S5, ESI†). When the probe bonded with ClO , gradually lowered, and the probe responded to ClO within
ꢀ
1
the peak of the exposed amino group (–NH
2
) at 3345–3459 cm
0.70–20 mM in a linear way, with the correlation coefficient of
was largely weakened, the assignment peak of cyano (CRN) at 0.99. The detection limit of the probe was determined by 3d/k to
ꢀ
ꢀ
1
2
1
239 cm disappeared, and a new assignment peak appeared at be 18 nM (d is standard deviation, k is the slope of the standard
1
ꢀ
798 cm (CQO), suggesting ClO reacted with the probe. SEM curve equation). All results indicated that the probe can rapidly
ꢀ
more visually reflected the changes in the probe after binding with and visually detect ClO , and has high selectivity and sensitivity
ꢀ
ClO (Fig. 5). Clearly, the probe is a clustered short rod and reacts as well as broad application prospects.
ꢀ
ꢀ
with ClO to form a decentralized massive structure, indicating that
To evaluate the feasibility and novelty of the ClO responsive
ꢀ
the structure changed-significantly after the reaction. Furthermore, probe, we compared it with other ClO fluorescent probes
the different morphology structure of the probe corresponds to the (Table 1). The new probe shows multiple excellent analytical
fluorescence change of the probe before and after the reaction with characteristics, such as simple synthesis steps, long emission
ꢀ
ClO . The morphology of the probe changes from the aggregate wavelength, and use of a highly aqueous medium.
state to the dispersed state accompanied by quenching of the strong
fluorescence based on AIE and ESIPT. All the studied results
ꢀ
confirmed the mechanism of detection on ClO .
ꢀ
After ClO was added to the probe solution, the colorless
and transparent solution immediately turned yellow under
sunlight, which corresponds to the fluorescence quenching of
the probe under the UV lamp at 365 nm. The color changes
ꢀ
after the reaction between the probe and ClO indicate that the
ꢀ
ꢀ
probe can recognize ClO under the naked eye. After ClO at
different concentrations was added to the probe DMSO/H
2
O
solution (1 : 99, v/v), the responsive sensitivity of the probe to
ꢀ
ClO was evaluated. Under the optimal experimental conditions
ꢀ
(
Fig. 6), as the ClO concentration increased, fluorescence was Fig. 8 SEM images before and after the reaction between the probe and FA.
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.4. Fluorescence sensing performance of the probe over FA
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3
aldehyde amine is condensed to form Schiff bases. The experi-
mental conditions of the probe for FA detection were set at
0 min, 60 1C, pH = 7.0. Then, the fluorescence spectra of the probe
in FA solutions at different concentrations were observed. The
fluorescence quenching effects of FA at different concentrations
on the probe were compared. Results show that the fluorescence
The effects of temperature on the probe and its response to FA
solutions were investigated (Fig. 7a). Results show that the
probe has high stability, and its fluorescence intensity is not
largely affected by temperature, but the temperature above
2
60 1C is favorable for its binding with FA, which may be because
Table 2 Comparison of different FA detection probes
Probe One-step synthesis Medium (v/v)
Emission wavelength (nm) Analytes LOD (mM) Gas test paper Ref.
No
No
MeOH
600
550
FA
FA
0.12
Yes
No
60
61
DMSO/PBS 1 : 99
0.0058
No
No
H
2
O/DMSO 3 : 7
393
519
FA
FA
1.6
Yes
No
62
63
DMSO/PBS 1 : 1
0.36
No
No
PBS
444
450
FA
FA
0.27
No
No
64
65
PBS/EtOH 5 : 95
1.6, 1.8
Yes
No
EtOH/HEPES 1 : 99 472
FA
FA
0.11
No
No
34
38
DMSO/PBS 1 : 9
530
0.040
No
H
2
2
O
436
575
FA
FA
8.4
No
66
Yes
H
O/DMSO 1 : 99
0.042
Yes
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ꢀ
ꢀ1
Table 3 Detection of ClO in real samples by the probe
2
between 3345–3459 cm was assigned to –NH . When the probe
bonded with FA, the disappearance of the bimodal absorption
Sensor (mM) Added (mM) Found (mM) Recovery (%)
corresponding to the disappearance of –NH , the appearance
2
Purified water No detected 5.0
5.74 ꢂ 0.55 114.8
9.68 ꢂ 0.24 96.8
10.36 ꢂ 0.67 109.4
15.04 ꢂ 0.34 101.5
5.16 ꢂ 0.06 103.2
11.05 ꢂ 0.03 110.5
ꢀ1
of spikes (1516 cm ) indicated the formation of new imine
1
0.0
5.0
0.0
groups. All the studied results confirmed the mechanism of the
detection on FA.
To evaluate the feasibility of the new FA-responsive probe,
we compared it with other FA fluorescent probes (Table 2). The
new probe shows multiple excellent analytical characteristics,
Tap water
Lake water
4.89 ꢂ 0.11
1
No detected 5.0
0.0
1
intensity of the probe is well linearly related to the FA concentration such as the one-step synthesis, emission at long wavelengths,
within 0.50–25 mM (Fig. 7b–d). Calculations indicate that the and applicability to gas detection.
detection limit of FA was 42 nM. The above results suggest that
3
.5. Practical application of the probe
the new probe can quantitatively detect aqueous FA and has high
ꢀ
sensitivity. The high fluorescence-sensing ability of the probe over The probe was used to detect ClO in real samples collected
FA may be attributed to the intramolecular charge transfer of the from water environments, including lake water, tap water, and
excited probe, forming an electron push/pull system. Since the drinking water. Each experiment was conducted in triplicate to
probe has a strong fluorescence, when the exposed amino group ensure experimental accuracy and validity (Table 3). From
ꢀ
binds with FA, the push–pull electron system is destroyed, so the standard curves of the probe in response to ClO , we
fluorescence is quenched. The probe and FA-binding mode were determined acceptable recovery rates, indicating that the probe
ꢀ
explored through fluorescence spectral analysis. This was validated is feasible in detecting ClO in real environments.
by mass spectra (Fig. S6, ESI†). The MS peak of the product
To further validate the detection ability of the probe over
O + H] from the reaction between the probe and FA gas, we developed an FA gas detection plate (Fig. 9).
equiv. of FA appeared at m/z 243.14, indicating that the probe can Under ultraviolet illumination at 365 nm, as the FA gas concen-
+
[
1
C
12
H
8
N
4
O + H
2
effectively bind with FA. SEM also shows that after binding with tration was increased, the fluorescence of the probe gradually
formaldehyde, the probe changed from the original clustered short weakened and finally disappeared. Hence, the experimental
rod shape to a decentralized fine and long fiber-like structure, which results indicate that the probe can be used as a portable
corresponds to the fluorescence change of the probe before and fluorescence sensor for detecting gas-phase FA. This method
after the reaction with FA (Fig. 8). The product was further purified is operationally easy and cheap and offers a feasible clue for the
and characterized by FT-IR (Fig. S7, ESI†), the bimodal absorption FA gas detection.
Fig. 9 Fluorescence pictures of gas-state FA on the detection plate (UV lamp at 365 nm).
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Paper
NJC
4
. Conclusion
5 S. Mu, H. Gao, C. Li, S. Li, Y. Wang, Y. Zhang, C. Ma,
H. Zhang and X. Liu, Talanta, 2021, 221, 121606.
An aggregation-induced emission (AIE) probe based on diamino-
maleonitrile was fabricated and used to sensitively and efficiently
detect FA and hypochlorites. This probe can be synthesized easily
from cheap raw materials and has typical AIE. In the mixed
solvent of DMSO/H
probe was fast, visible to the naked eye, and sensitive. The
detection limit was as low as 18 nM, and the recovery of real
water samples also validated the probe’s practicability for ClO
detection. Based on the condensation reaction, the probe with an
amino group as the binding site can well linearly detected in
6
7
8
9
G. Li, Y. Ma, M. Pei and W. Lin, Anal. Chem., 2019, 91,
4586–14590.
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Y.-D. Lu and H.-L. Zhu, Appl. Mater. Today, 2020, 21, 100877.
1
ꢀ
2
O (1: 99, v/v), the detection of ClO by the
ꢀ
1
0 P. Q. Nhien, W. L. Chou, T. T. K. Cuc, T. M. Khang, C. H.
Wu, N. Thirumalaivasan, B. T. B. Hue, J. I. Wu, S. P. Wu and
H. C. Lin, ACS Appl. Mater. Interfaces, 2020, 12, 10959–10972.
1 X. Wen, Q. Wang and Z. Fan, Anal. Chim. Acta, 2018, 1013,
0.50–25 mM FA solutions, with the detection limit of 42 nM.
According to AIE molecules’ application in solid films, a type of
portable solid-state detection plate was successfully developed
and used to detect FA gas.
In short, the simply synthesized probe is multifunctional. It
breaks through the defects of other probes such as complex
synthesis steps and organic solvent dependence. It is a novel
probe and can realize the detection of samples in the environ-
mental field. The probe has a good application prospect for the
1
1
1
1
1
79–86.
2 Z. Zhou, X. Li, Y. Zhang, C. C. Zhang, Y. Tang, J. Gao, L. Ma
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and Y. S. Al-Ammari, Spectrochim. Acta, Part A, 2018, 201,
ꢀ
rapid visual detection of ClO in environmental water sample
detection. The construction of solid-state detection plates has
favorable application prospects and provides a new idea for the
monitoring of formaldehyde gas in the environment. The
establishment and research on the new method offer a new
technique and clues for double-site fluorescence detection of
gas-state FA and hypochlorites.
54–60.
1
1
1
1
6 X. Li, X. Lin, S. Lin, X. Sun, D. Gao, B. Liu, H. Zhao, J. Zhang,
S. Cong and L. Wang, ACS Appl. Nano Mater., 2019, 2, 3161–3168.
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Author contributions
9 M. Li, F. Du, P. Xue, X. Tan, S. Liu, Y. Zhou, J. Chen and
Xiaoye Wen and Li Yan contributed equally to this work: con-
L. Bai, Spectrochim. Acta, Part A, 2020, 227, 117760.
ceptualization, data curation, formal analysis, methodology, 20 Y. Li, L. Liu, Y. Tang, Y. Wang, J. Han and L. Ni, Spectrochim.
investigation, writing-original draft. Zhefeng Fan: investigation,
resources, supervision, writing-review & editing.
Acta, Part A, 2020, 232, 118154.
21 B. Zhu, X. Wu, J. Rodrigues, X. Hu, R. Sheng and G. M. Bao,
Spectrochim. Acta, Part A, 2021, 246, 118953.
2
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Conflicts of interest
There are no conflicts of interest to declare.
Acknowledgements
This work was supported by the Doctor Fund of Shanxi Normal
University (0505/02070481), Science Foundation for Youths
Fund of Shanxi Province of China (0502/02010163).
7 Y. Huang, Y. Zhang, F. Huo, Y. Liu and C. Yin, Dyes Pigm.,
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