A new carbazole-based colorimetric and fluorescent sensor with aggregation induced emission for detection of cyanide anion

Article abstract of DOI:10.1016/j.dyepig.2019.01.023

A new carbazole-based naked-eye colorimetric and fluorescent sensor CPPB with aggregation induced emission (AIE) effect was successfully synthesized. The solid powder of CPPB emitted intense yellow fluorescence, and its emission wavelength and fluorescence intensity in DMSO/H₂O solution varied with the percentage of water (f_w). Nano-aggregates of CPPB molecules were prepared by increasing f_w of DMSO/H₂O solution, and the optimal aggregation state of CPPB was reached in 99% aqueous DMSO solution with the maximum fluorescence intensity. Moreover, CPPB displayed high selectivity and sensitivity toward cyanide anions (CN^?) in 99% aqueous DMSO solution even in the presence of other competitive anions (CN^?, F^?, Cl^?, AcO^?, NO₃ ^?, I^?, CO₃ ^2?, HCO₃ ^?, HSO₃ ^?, SO₄ ^2?, S^2?, HS^?, OH^?, H₂PO₄ ^? and HPO₄ ^2?) and the reactive oxygen species (H₂O₂, O₂ ^·?, ¹O₂, t-BuOOH and ·OH). The sensing mechanism for CN^? was confirmed by optical spectral studies, ¹H NMR titration, HRMS spectra, Job's plot analyses and DFT calculations. Sensor CPPB for CN^? detection revealed extremely low detection limit (67.4 nM), high anti–interference ability, wide pH response range (3.0–10.0) as well as the immediate response (15 s). Furthermore, the CPPB-based test strips were applied to detect CN^? qualitatively and quantitatively in 100% aqueous solution.

Full text of DOI:10.1016/j.dyepig.2019.01.023

Accepted Manuscript
A new carbazole-based colorimetric and fluorescent sensor with aggregation induced
emission for detection of cyanide anion
Qiqi Zou, Furong Tao, Hongtao Wu, William W. Yu, Tianduo Li, Yuezhi Cui
PII:
S0143-7208(18)32671-8
https://doi.org/10.1016/j.dyepig.2019.01.023
DYPI 7296
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 5 December 2018
Revised Date: 17 January 2019
Accepted Date: 17 January 2019
Please cite this article as: Zou Q, Tao F, Wu H, Yu WW, Li T, Cui Y, A new carbazole-based colorimetric
and fluorescent sensor with aggregation induced emission for detection of cyanide anion, Dyes and
Pigments (2019), doi: https://doi.org/10.1016/j.dyepig.2019.01.023.
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ACCEPTED MANUSCRIPT
Graphical Abstract
We have successfully developed sensor CPPB, which exhibited distinct
aggregation induced emission (AIE) effect, and detected CN− based on naked-eye
colorimetric and fluorescent sensing with high selectivity and great sensitivity.

ACCEPTED MANUSCRIPT
A new carbazole-based colorimetric and fluorescent sensor with
Aggregation induced emission for detection of cyanide anion
Qiqi Zou, Furong Tao, Hongtao Wu, William W. Yu, Tianduo Li, Yuezhi Cui*
School of Chemical and Pharmaceutical Engineering, Qilu University of Technology
(Shandong Academy of Sciences), Jinan 250353, P. R. China.
Tel: +86 531 89631208; Fax: +86 531 89631760;
E-mail address: yuezhicui@163.com
1

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Abstract
A new carbazole-based naked-eye colorimetric and fluorescent sensor CPPB with
aggregation induced emission (AIE) effect was successfully synthesized. The solid
powder of CPPB emitted intense yellow fluorescence, and its emission wavelength
and fluorescence intensity in DMSO/H2O solution varied with the percentage of water
(fw). Nano-aggregates of CPPB molecules were prepared by increasing fw of
DMSO/H2O solution, and the optimal aggregation state of CPPB was reached in 99%
aqueous DMSO solution with the maximum fluorescence intensity. Moreover, CPPB
displayed high selectivity and sensitivity toward cyanide anions (CN–) in 99%
aqueous DMSO solution even in the presence of other competitive anions (CN−, F−,
−
2−
−
−
2−
−
Cl−, AcO−, NO3 , I−, CO3 , HCO3 , HSO3 , SO4 , S2−, HS−, OH−, H2PO4 and
·
HPO4 ) and the reactive oxygen species (H2O2, O2 −, O2, t-BuOOH and ·OH). The
2−
1
1
sensing mechanism for CN– was confirmed by optical spectral studies, H NMR
titration, HRMS spectra, Job’s plot analyses and DFT calculations. Sensor CPPB for
CN– detection revealed extremely low detection limit (67.4 nM), high
anti–interference ability, wide pH response range (3.0 ~ 10.0) as well as the
immediate response (15 s). Furthermore, the CPPB-based test strips were applied to
detect CN− qualitatively and quantitatively in 100% aqueous solution.
Keywords: Aggregation induced emission, Colorimetric, Fluorescent, Cyanide anion,
test strips.
2

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1
．
Introduction
With the development of science, the safety of the living environment and food has
attracted wide concern. The cyanide anions have received a great deal of attention
since it is incredibly harmful and venomous to the human body [1–8]. Cyanide anions
are mainly associated with metal ions in cytochrome P450, which lead to losing its
ability to transmit electrons in the respiratory chain, followed by damaging on the
central nervous system. Even so, cyanide is widely used in many aspects of the
modern industry, such as wet smelting of gold and silver, electroplating technology,
synthetic fiber, herbicides and so on, which cause cyanide anions to enter the human
body through water and the food chain [9–13]. Nevertheless, the World Health
Organization (WHO) stipulates that the maximum safe concentration level allowed in
drinking water is 1.9 µM [14]. Therefore, the development of a low-cost, simple, great
sensitive and highly selective colorimetric and fluorescent chemical sensor for the
detection of cyanide ions in the environment is necessary [15–29]. A number of
colorimetric and fluorescent chemosensor for CN– has been developed, based on
several mechanisms, such as intra-molecular charge transfer (ICT) [30,31], excited state
intra-molecular proton transfer (ESIPT) [32], and photoinduced electron transfer (PET)
[33], et al. However, most sensing materials for CN– detection are readily soluble in
organic solvents but insoluble in water, while the most significant number of CN–
exists in water, such as industrial waste water, drinking water and experimental
discharge water, et al [34-37]. So it is critical to developing the sensors for CN– in
aqueous solution.
The sensing materials with aggregation induced emission (AIE) effect may be a
good candidate for detecting CN– in aqueous solution. AIE-active materials emit no
fluorescence in solution, while it is highly emissive in aqueous solution due to the
formation of aggregates [38]. However, only a limited number of sensing materials
with both AIE effect and good sensing performance for CN– have been reported.
Therefore, research on sensing materials for CN– detection with AIE effect is still of
great challenge.
Herein, we reported an AIE-active compound CPPB (Scheme 1), which was an
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ICT-based D-π-A type sensor with carbazole as an electron-donating group and
barbituric acid as an electron-withdrawing group. Sensor CPPB exhibited highly
sensitive and good selective for CN– detection based on naked-eye colorimetric and
fluorescent sensing in 99% aqueous DMSO solution. Sensor CPPB for CN– detection
displayed fast response speed, high anti-interference ability and low detection limit of
67.4 nM. Moreover, CPPB-based test paper strips revealed excellent and high
sensitivities for detection of CN– in 100% aqueous solution.
Scheme 1
2. Experimental
2.1. Materials and apparatus
All chemicals and solvents were obtained as the analytical grade by commerce and
−
2−
used without further purification. Anions (CN−, F−, Cl−, AcO−, NO3 , I−, CO3 ,
HCO3 , HSO3 , SO4 , S2−, HS−, OH−, H2PO4 and HPO4 ) from their
−
−
2−
−
2−
·
1
tetrabutylammonium salts and reactive oxygen species (H2O2, O2 −, O2, t-BuOOH
and ·OH)[39,40] were prepared, which was diluted to 1.0 mM by deionized water to
obtain the stock solution. NMR spectra were measured on Bruker AvanceⅡ 400 using
TMS as an internal standard spectrometer in DMSO-d6. Infrared spectra of CPPB and
CPPB-CN– were recorded on Bruker ALPHA FT-IR spectrometer using KBr pellets.
High-resolution mass spectra (HRMS) were obtained from Agilent 6510
Accurate-Mass Q-TOF LC/MS system. UV-vis and fluorescent spectra were carried
out on a Shimadzu UV-2600 and Hitachi F-4600 fluorescence spectrophotometer,
respectively.
2.2. Synthesis of the sensor CPPB
Compounds 2 and 3 were prepared by the previously reported procedures (Scheme
1) [41]. Compound 3 (0.5 g, 2.1 mmol) and barbituric acid (0.27 g, 2.1 mmol) were
mixed in distilled ethanol (10 mL) and stirred under reflux for 5 h, then the mixture
was cooled down and filtered off to obtain the compound CPPB, which was then
1
washed with ethanol and dried in vacuum as an orange solid (0.68 g, yield 93%). H
NMR: (400 MHz, DMSO-d6) δ = 11.22 (s, 1H), 11.10 (s, 1H), 9.21 (s, 1H), 8.56 (d, J
= 8.0 Hz, 1H), 8.44 (s, 1H), 8.11 (d, J = 8.0 Hz, 1H), 7.62-7.68 (m, 2H), 7.45 (t, J =
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8.0 Hz, 1H), 7.23 (t, J = 8.0 Hz, 1H), 4.35 (t, J = 8.0 Hz, 2H), 1.71-1.77 (m, 2H), 0.80
13
(t, J = 4.0 Hz, 3H); C NMR: (100 MHz, DMSO–d6) δ = 164.18, 162.37, 156.82,
150.23, 143.20, 140.80, 133.23, 129.48, 126.67, 123.42, 122.34, 120.46, 120.40,
114.06, 110.27, 109.30, 44.01, 21.85, 11.23; FT-IR: (KBr, cm–1) ν = 3423 (H2O), 3210
(N–H), 3057 (C–H), 1726 (C=O), 1665 (C=C), 1137 (C–N); HRMS (ESI): m/z:
[M+H]+ calcd for: C20H17N3O3: 348.1348, found: 348.1340.
2.3. Spectroscopic experiments
The sensor CPPB was dissolved in DMSO to obtain a stock solution of 1.0 mM.
The testing anions were dissolved in deionized water to obtain the stock solutions of
1.0 mM. The standard solution of CPPB (50 µL) was added to 5 mL of deionized
water containing various amount of CN–. A blank solution without any CN– was
prepared as the same procedure. The testing solutions contained 10 µM of CPPB. The
UV-vis absorption spectra were recorded in the wavelength range of 250 to 600 nm
using a quartz cell of 1 cm. The fluorescence emission spectra were recorded in the
wavelength range from 460 to 840 nm with excitation wavelength at 627 nm. Both the
excitation and emission slits were set at 5 nm.
2.4. The determination of DL
The detection limit (DL) was determined according to the formula (1) by emission
data of sensor CPPB upon gradual addition of CN–.
DL=3δ/S
(1)
where δ was the standard deviation of blank ample, S represented the absolute value
of the slope between fluorescence intensity and CN– concentration [42,43]
.
2.5. 1H NMR titration
A solution of sensor CPPB (5 mM) was prepared in DMSO-d6. To a 0.5 mL of
sensor solution, equivalents of tetrabutylammonium bromide (from a stock of 10 mM
in DMSO-d6) were added to an NMR tube through a micropipette, and the spectra
were recorded.
2.6 Computational Procedures for HOMO-LUMO energy gap
The HOMO-LUMO energy gap for CPPB and CPPB-CN–, as well as its
complexes, were calculated by density functional theory (DFT) using Gaussian 09W.
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The DFT based B3LYP/6-31G* model was performed for C, N, O, H atoms. After
obtaining the converged geometries, the TD-B3LYP/6-31G* was used to calculate the
vertical excitation energies.
3. Results and discussion
3.1 Synthesis and characterization
The
compound
CPPB
was
prepared
by
refluxing
between
9-Propyl-9H-carbazol-3-carbaldehyde and barbituric acid in EtOH (Scheme 1). The
synthetic route of CPPB was simple, and the yield is very high. The structure was
13
1
confirmed by 1H NMR, C NMR, HRMS and FT-IR spectra (Fig S1–S4). H NMR
spectrum of CPPB exhibits singlet signal at 11.22 ppm and 11.10 ppm ascribed to NH
and 9.21 ppm ascribed to vinyl C=CH proton, respectively. FT–IR spectrum of CPPB
displays stretching at 3210 cm−1 for N−H, 3057 cm−1 for saturated hydrocarbon C−H,
1726 cm−1 for amide C=O and 1665 cm−1 for vinyl C=C group. HRMS spectrum of
CPPB shows a parent peak at m/z 348.1340 corresponding to the [M+H]+ fragment.
3.2 AIE activity of sensor CPPB
AIE activity of CPPB was investigated by UV-vis spectra and fluorescence (FL)
spectra. As shown in Fig. 1, the absorption bands ranging between 270 and 350 nm
were assigned to π-π* electronic transition of the barbituric acid and carbazole unit.
Additionally, the CPPB molecule exhibited a sharp absorption peak at 434 nm, which
can be attributed to intra-molecular charge transfer (ICT) from the carbazole to the
barbituric acid.
Fig. 1
The FL spectra of sensor CPPB in pure DMSO solvent, as well as those in
DMSO/H2O mixture, were recorded (Fig. 2a). Since water is a poor solvent,
aggregation of CPPB can be promoted by adding water to DMSO, leading to
enhanced emission. Therefore, the mixture of DMSO and water was used for the
preparation of nano-aggregates of CPPB by increasing the percentage of water (fw).
Different FL spectra with different fw were exhibited (Fig.2(a), (b)) depicted the
variation trend of FL intensity and wavelength of CPPB under different fw.
As observed in Fig. 2a, sensor CPPB showed weak emission in pure DMSO
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solvent (CCPPB = 10 µM), while the powder of CPPB emitted strong fluorescence.
These observations indicated a strong AIE activity of CPPB. In addition, the FL
intensity of CPPB in pure DMSO (fw = 0%) was very weak. When fw was less than
80%，the FL intensity of CPPB decreased as water content increased. However, it
began to increase when fw was increased to 90%. Moreover, the FL intensity reached
a maximum at fw = 99%, which has increased by 5.7 times compared to the FL
intensity in pure DMSO solvent (fw = 0%). These data demonstrated CPPB is
AIE-active molecule [44-51]
.
From Fig. 2(b), it can be observed that the emission peak of CPPB was red-shifted
from 547 to 623 nm when fw increased from 0% to 99%. The large red-shifted may be
attributed to the π-π staking when CPPB molecules aggregated at high water content.
When fw was no more than 90%, the addition of water enhanced the polarity of the
mixed solvent which caused ICT, and thus the fluorescence became weakened as fw
increased. As fw reached 90%, CPPB molecules started to aggregate, resulting in
nanoparticles. Thus its fluorescence was significantly enhanced due to the AIE
activity.
Fig. 2
The fluorescence emission of CPPB in mixed DMSO/H2O (fw = 0% ~ 99%) under
UV lamp (365 nm) were observed in Fig. 3. The fluorescence enhanced when fw
increased from 0% to 80%, and then weakened obviously when fw increased from
90% to 99%. The fluorescence color was significantly changed from yellow-green to
orange. These observations were consistent with the data in Fig. 2.
Fig. 3
3.3 Sensing performance of CPPB
3.3.1. Selectivity and anti-interference of anions
–
–
2–
2–
–
A series of anions (F–, Cl–, Br–, I–, NO3 , AcO–, HCO3 , CO3 , SO4 , HSO4 , S2−,
·
−
−
HS−, OH− H2PO4 , HPO42− and CN–) and the reactive oxygen species (H2O2, O2 , 1O2,
t-BuOOH and ·OH) were respectively added to the solution containing CPPB (1 mM),
and the changes in the spectra as well as the FL spectra with each addition were
monitored. The solutions containing the common anions but CN– showed yellow in
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daylight and orange fluorescence at UV lamp (365 nm), while the solution containing
only CN– displayed no color in daylight and blue fluorescence at 365 nm (Fig. 4).
These observations indicated that the sensor is highly selective towards CN–. It was
found that the UV-vis spectra and FL spectra (λex = 440 nm, λem = 625 nm) of CPPB
did not show significant change, even upon adding 10 equiv. of each anions except for
CN– (Fig. 5). In the presence of CN–, the intensity of the absorption band of CPPB at
longer wavelength (436 nm) was attenuated, while a new band appeared at 260 nm,
and the intensity of the emission peak for CPPB at 625 nm was significantly
enhanced. Such spectral changes suggest changes in the chemical structure of CPPB.
This may be due to the fact that the reaction of cyanide with CPPB might have
switched-off the ICT transition, which in turn affects its spectral properties [52]
.
Fig. 4
Fig. 5
To further explore the utility of CPPB as an ion-selective fluorescent sensor for
CN–, the anti-interference experiment of sensor CPPB was carried out upon addition
of 2.0 equiv. of various anions in 99% aqueous DMSO solution (Fig. 6). The results
indicate that common anions has no effect on sensor CPPB for CN– detection and
CPPB could be used as a fluorescent sensor for CN– detection with excellent
selectivity and good anti-interference.
Fig. 6
3.3.2. Detection performance of sensor CPPB to CN–
The changes of absorption spectrum of CPPB upon adding different amounts of
CN– in 99% aqueous DMSO solution can be seen in Fig. 7. As the concentration of
CN– increased from 0.5 to 2.0 equiv., all the absorption peaks at 280nm, 333nm and
440nm decreased remarkably. Additionally, a new absorption band appeared at 263
nm and increased significantly with the concentration of CN– increasing. These results
indicate that the reaction between CPPB and CN– occurs and the conjugated system
of CPPB was broken by CN–. An iso-absorbance spot was observed at 275 nm
indicating that the reaction between CPPB and CN– produced a new complex. These
speculations have been experimentally proved in the next section.
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Fig. 7
The sensing performance of CPPB to different amounts of CN– in 99% aqueous
DMSO solution was further studied by fluorescence emission spectroscopy (Fig.8).
As shown in Fig. 8a, with the amount of CN– (0.5 ~ 2.0 equiv.) increasing, the
emission peak at 625 nm gradually decreases due to the interruption of
intra-molecular charge transfer (ICT) of CPPB. The inset in Fig. 8a is a plot of the
fluorescence intensity of CPPB at 625 nm as a function of the concentration of CN− (0
-
~ 2.0 equiv). It can be seen that the FL intensity decreases remarkably when CCN
-
increases from 0 to 10 µM. When CCN is larger than 10 µM, the FL intensity almost
remains unchanged, indicating that CN− is saturated in the solution. The detection
limit (DL) of sensor CPPB for CN– was determined to be 67.4 nM with a linear range
of concentration to be 0 ~ 10 µM (Fig. 8b), which far below the allowable content of
CN– in drinking water.
Fig. 8
The stability of CPPB and CPPB-CN– under different pH in 99% aqueous DMSO
solution was studied by FL spectra (Fig. 9). CPPB had a stable emission intensity as
pH changed from 1.0 to 10.0, while the emission intensity dropped sharply when the
pH was more than 10.0. Contrastingly, the emission intensity of CPPB-CN– in the pH
range of 1.0 ~ 10.0 was weaker than CPPB and showed a sharply decreasing
tendency when pH increased from 1.0 to 10. It can be seen that the different emission
intensity between CPPB-CN– and CPPB were relatively large at pH = 3.0 ~ 10.0,
indicating that CPPB may exhibits excellent fluorescence response to CN– at this pH
range.
Fig. 9
The reaction time of CPPB towards CN− was investigated by time-dependent
fluorescence spectrum (Fig. 10). The FL intensity of CPPB increased rapidly within
the first 15 s when CN− was added. Afterward, the FL intensity of CPPB-CN− almost
kept unchanged in the next 25 s. Conclusively, the reaction between CPPB and CN−
could accomplish within 15 s at room temperature. The rapid response of CPPB
towards CN− provides a favorable condition for practical applications.
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Fig. 10
3.4 Detection mechanism
1
The detection mechanism was investigated by H NMR titration, HRMS spectra
1
and Job’s titration. H NMR spectrum of sensor CPPB displayed two stretching
vibration bands at 11.20 ppm and 9.20 ppm, which were assigned to Ha of barbituric
1
acid and H1 of vinylidene (Fig. 11). Nevertheless, in the H NMR spectrum of
CPPB-CN–, the band at 9.20 ppm corresponding to H1 disappeared completely, while
a new peak at 5.60 ppm which was assigned to H2 was observed. Meanwhile, the peak
of Ha at 11.20 ppm moved to high frequency of 9.15 ppm that was assigned to Hb.
Furthermore, some other peaks corresponding to aromatic protons move slightly to
high frequencies upon CN– addition, owing to the breaking of the original structure.
The investigation confirmed that CN– with strong nucleophilicity attacked the C=C
bond and interrupted the ICT between the electron donor and the electron acceptor of
sensor CPPB [53]. To further confirm the detection mechanism, the HRMS spectra of
CPPB and CPPB-CN– were researched. As shown in Fig S5, a distinct upfield shift
was observed for the vinylic proton H1 of CPPB upon addition of CN–. The vinylic
proton H1 shifted upfield from 325.1457 ppm to 392.1485 ppm (denoted H2),
indicating that the nucleophilic addition reaction between CPPB and CN– was
completed. Fig. 12 displayed the results of Job’s titration derived from fluorescence
emission spectra, which indicated the 1:1 stoichiometric reaction between sensor
CPPB and CN–. Therefore, the detection mechanism of sensor CPPB for CN– has
been confirmed to be that CN– with strong nucleophilicity attacked the vinylidene of
CPPB (Scheme 2).
Fig. 11
Fig. 12
Scheme 2
3.5. Theoretical Calculations
To further investigate the detection mechanism of CPPB for CN–, the density
functional theory (DFT) and time-dependent density functional theory (TD-DFT)
calculations were performed at the B3LYP/6-31G* level of the Gaussian 09 program
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[44-47]
on the structure, electron distribution and optical properties of CPPB and
CPPB-CN–. The optimized structure of CPPB and CPPB-CN– was depicted in Fig.
13. Molecule CPPB showed a rigid planar conformation by sp2 hybridization,
however, CPPB-CN– displayed a V-shaped conformation by sp3 hybridization. The
result indicated that distinct structural differences between CPPB and CPPB-CN–
leaded to no ICT of CPPB-CN– and caused significant changes of the conjugated
system, which resulted in significant changes in their fluorescence properties.
Fig. 13
To grasp more about the colorimetric and fluorescent sensing mechanisms of
CPPB, the time dependent DFT calculations were figured out (Fig. 14). For CPPB
molecule, the electron distribution of LUMO was mainly concentrated in the entire
barbituric acid and a part of the carbazole group, while that of the HOMO was
distributed in the part of the barbituric acid and the entire carbazole group. However,
for the CPPB-CN− molecule, the electron distribution of LUMO and HOMO were
both distributed over the carbazole group, which implied the interruption of ICT stage,
resulted in obvious fluorescence weaken and brought about a new absorption band of
CPPB-CN−. Moreover, the break of the π-conjugated system caused the increased
HOMO-LUMO energy gap of CPPB-CN− (4.63 eV) relative to the sensor CPPB
(3.41 eV), which can be interpreted for the appearance of the new absorption band
(263 nm). Furthermore, the calculated excitation wavelengths of CPPB and
CPPB-CN− were 402 nm and 268 nm respectively, which were almost consistent with
the experimental results (Fig. 5). Therefore, these DFT and TD-DFT calculations
verified that the CN− was combined with the vinylidene of sensor CPPB which lead
to the fluorescence quenching of CPPB.
Fig. 14
3.6 Test strips for CN− detection in 100% aqueous
For convenient use of sensor CPPB for CN− detection, the test strips of CPPB
toward CN− in 100% aqueous was prepared. Sensor CPPB (20 µM, H2O/DMSO (9:1;
v/v)), has been coated on filter paper, and dried in a dry box, followed by adding
different concentrations of CN− in 100% aqueous. As observed in Fig. 14, significant
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color changes under UV light from orange to blue turn out with different
concentration of CN− (0 ~ 20 µM). It proved that the test strips can be applied to
detect CN− qualitatively and quantitatively.
Fig. 15
4. Conclusions
In summary, we have successfully developed sensor CPPB for CN– detection based
on naked-eye colorimetric and fluorescent sensing in 99% aqueous DMSO solution
with high selectivity and great sensitivity, which exhibits interesting AIE effect.
Moreover, sensor CPPB for the detection of CN− revealed extremely low detection
limit (67.4 nM), high anti-interference ability, wide pH response range as well as
immediate response (15 s), which indicated that CPPB may be promising candidates
for sensing CN− in water.
Acknowledgment
This work was financially supported by the Natural Science Foundation of
Shandong province [ZR2018MB025], Key R&D Program Projects of Shandong
province [2017GGX202001] and a Project of Shandong Province Higher Educational
Science and Technology Program (NO. J18KZ004).
Declarations of interest
None.
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Figure captions
Scheme 1. The synthetic route of the sensor CPPB
Fig. 1. The UV-vis absorption spectra of sensor CPPB (10 µM) in pure DMSO.
Fig. 2. (a) The FL spectra of sensor CPPB (10 µM) in DMSO/H2O (v/v) mixtures
with different water fraction (ƒw) at λex = 440 nm; (b) Plot of relative FL peak
wavelength (blue) and emission intensity (purple) of CPPB versus the ƒw. (The blue
line belongs to the wavelength, and the red line belongs to the FL intensity.)
Fig. 3. Photographs of sensor CPPB at fw = 0% to 99% under 365 nm UV light.
Fig. 4. Color changes induced upon addition of 2.0 equiv. of various anions and
reactive oxygen species to CPPB solution in 99% aqueous DMSO solution under
sunlight and 365 nm UV light. (The first row shows the color change under sunlight,
and the second row shows the color change under 365 nm UV light)
Fig. 5. (a) The UV-vis spectra of CPPB (10 µM) with various anions and reactive
oxygen species (2.0 equiv.) in 99% aqueous DMSO solution; (b) The FL spectra of
CPPB (10 µM) with various anions and reactive oxygen species (2.0 equiv.) in 99%
aqueous DMSO solution.
Fig. 6. Competitive experiments in the CPPB-CN− system with interfering anions
(λex = 440 nm). Blue bars represent other anions and reactive oxygen species solution
(1 mM) and red bars represent other anions and reactive oxygen species solution with
CN− (1 mM).
Fig. 7. The UV-vis spectra upon titration CN− (0 ~ 2.0 equiv.) at various concentration
in 99% aqueous DMSO solution.
Fig. 8. (a) The FL titration spectra of CPPB (10 µM) with the increasing
concentration of CN− (0 ~ 2.0 equiv.) in 99% aqueous DMSO solution, Inset: plot of
the FL intensity of CPPB at 625 nm as a function of CN− concentration (0 ~ 2.0
equiv.); (b) The detection limit of CPPB for CN–.
Fig. 9. The FL intensity of CPPB (10 µM) as a function of pH (1.0 ~ 14.0) in the
absence and presence of CN– (λex = 440 nm).
Fig. 10. The time-dependent FL spectrum of CPPB toward CN−.
1
Fig. 11. The H NMR spectra of CPPB (red) and CPPB-CN− (navy) in DMSO-d6
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upon the addition of 2.0 equiv. CN−.
Fig. 12. Job's plot for CPPB towards CN− in 99% aqueous DMSO solution (The total
concentration was 10 µM).
Scheme 2. The sensing mechanism of sensor CPPB for CN–.
Fig. 13. Optimized structures of CPPB and CPPB-CN−.
Fig. 14. HOMO and LUMO energy levels of CPPB and CPPB-CN−.
Fig. 15. The photographs of CPPB upon addition of CN− under 365 UV light on filter
paper.
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Scheme 1
Fig. 1
Fig. 2
Fig. 3
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Fig. 4
Fig. 5
Fig. 6
Fig. 7
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Fig. 8
Fig. 9
Fig.10
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Fig. 11
Fig. 12
Scheme 2
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Fig. 13
Fig. 14
Fig. 15
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Highlights
Carbazole-based colorimetric and fluorescent sensor CPPB was designed
and synthesized, which exhibited obvious aggregation induced emission
(AIE) effect.
The sensor CPPB detected CN– in 99% aqueous DMSO solution, and the
test strips of CPPB recognized CN– in 100% aqueous solution.
The detection limit of sensor CPPB for CN– were at nanomolar level in
99% aqueous DMSO solution.
Colorimetric responses of sensor CPPB toward CN– were visible with the
naked eyes under sunlight and UV lamp (365 nm).