Development of an anthraquinone-based cyanide colorimetric sensor with activated C–H group: Large absorption red shift and application in food and water samples

Article abstract of DOI:10.1016/j.tet.2020.131479

Development of colorimetric sensors has emerged as an attractive strategy for cyanide detection owing to their unique advantages, including simple visual detection and economical nature. In this work, anthraquinone derivatives (3a-d) have been easily prep

Full text of DOI:10.1016/j.tet.2020.131479

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Development of an anthraquinone-based cyanide colorimetric sensor with activated
C–H group: Large absorption red shift and application in food and water samples
Tingting Zhu, Zheyao Li, Chao Fu, Lu Chen, Xi Chen, Chen Gao, Shuhan Zhang,
Chuanxiang Liu
PII:
S0040-4020(20)30659-1
https://doi.org/10.1016/j.tet.2020.131479
TET 131479
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 11 June 2020
Revised Date: 9 July 2020
Accepted Date: 4 August 2020
Please cite this article as: Zhu T, Li Z, Fu C, Chen L, Chen X, Gao C, Zhang S, Liu C, Development
of an anthraquinone-based cyanide colorimetric sensor with activated C–H group: Large absorption
red shift and application in food and water samples, Tetrahedron (2020), doi: https://doi.org/10.1016/
j.tet.2020.131479.
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Graphical Abstract
Development of an anthraquinone-based cyanide colorimetric sensor with activated C-H group: large
absorption red shift and application in food and water samples
Tingting Zhu, Zheyao Li, Chao Fu, Lu Chen, Xi Chen, Chen Gao, Shuhan Zhang and Chuanxiang Liu*
Design and working principle of sensor.

Tetrahedron
1
Tetrahedron
journal homepage: www.elsevier.com
Development of an anthraquinone-based cyanide colorimetric sensor with activated
C-H group: large absorption red shift and application in food and water samples
Tingting Zhu, Zheyao Li, Chao Fu, Lu Chen, Xi Chen, Chen Gao, Shuhan Zhang and Chuanxiang Liu*
School of Chemical and Environmental Engineering, Shanghai Institute of Technology, Shanghai 201418, P. R. China
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
Development of colorimetric sensors has emerged as an attractive strategy for cyanide detection
owing to their unique advantages, including simple visual detection and economical nature. In
this work, anthraquinone derivatives (3a-d) have been easily prepared via nucleophilic
substitution of 1-chloro anthraquinone with substituted phenylacetonitriles, with only nitro-
substituted anthraquinone 3d displaying colorimetric sensor capabilities. The sensor showed
good selectivity, reversibility and reusability toward cyanide detection, as well as efficient
naked-eye color change from colorless to blue-purple in a neutral aqueous medium. The
deprotonation mechanism of CH was investigated by NMR spectroscopy and supported by DFT
calculations. Furthermore, the sensor 3d was successfully loaded onto test strips as a convenient
and efficient solid-state sensor for cyanide detection. It was utilized for cyanide detection in
cassava flour and bitter almonds food samples, as well as displaying excellent performance in
real-world water samples.
Available online
Keywords:
Anthraquinone
C-H group
Colorimetric sensor
Cyanide
Real sample
2020 Elsevier Ltd. All rights reserved
.
1. Introduction
fluorescein, cyanine dyes, ruthenium complexes, ferrocene, azo
dye, 8-hydroxyquinoline, rhodamine and anthraquinones [21],
have been utilized as signaling units for the construction of
chemosensors. Among them, anthraquinone derivatives have
relatively stable structures, colorimetric properties, and wide
applications as dyes, pigments and industrial pharmaceuticals
[22-24]. Recent reports have shown numerous optical
anthraquinone–based sensors that exploit hydrogen-bonding
strategies such as OH or NH groups as binding motifs for
cyanides [25-28]. Additionally, activated C-H groups (CHCN),
can also attach to the chromophore or fluorophore to produce
optical sensors that trigger significant optical changes. However,
optical anthraquinone–based sensors with C-H group binding
sites have not yet been reported. Previous reports by our group
have shown the development of several sensors by implementing
the activated CH-based strategy with naphthalimide and
BODIPY [29,30], which significantly enhanced resistance to
proton transfer and affinity toward softer anions, as well as
stronger binding absorption red shift [31,32]. Furthermore, the
activated CH strategy was extended to a variety of other
chromophores and fluorophores, where a novel anthraquinone-
based cyanide colorimetric sensor with activated C-H group was
exploited for the first time (Scheme 1).
Cyanide (CN−) ion is extremely poisonous to all mammals and
aquatic life [1-3], due to it strongly binds the active site of
cytochrome c oxidase in mitochondrial, which suppresses
electronic transportation, causing cytotoxic hypoxia and eventual
cell death [4-6]. Despite its acute toxicity, cyanide is commonly
used in pharmaceuticals, plastics manufacturing, electroplating,
gold mining, and silver extraction [7,8]. Moreover, it is also
commonly found in foods and plants such as sprouted potatoes,
tapioca flour, cherry nuts, bamboo shoots and bitter almonds [9-
11]. Consequently, cyanide detection methodologies have gained
considerable attention. Compared to conventional analytical
methods such as mass spectrometry, Raman spectroscopy, ion
chromatography, electrochemical, titrimetric and voltammetric
technologies [12-16], optical chemosensors by colorimetric
analysis is the most promising approach owing to its simplicity,
high sensitivity, selectivity, rapid response, economical and
potential naked-eye visual detection [17-19]. However, some
reported sensors still lack reversibility and sensitivity [20].
Therefore, the design and development of novel colorimetric
chemosensors for the reversible and selective detection of
cyanide in various environmental and real-world samples is
highly desirable.
Recently, various chromophores or fluorophores, such as
naphthalene, anthracene, pyrene, BODIPY derivatives,
porphyrins, coumarin, nitro compounds, phthalocyanine,

2
Tetrahedron
extracted with dichloromethane and dried over anhydrous
NaSO4. Finally, the dried solution was concentrated and purified
by column chromatography (PE: DCM = 3:1) to obtain 3a (0.35
1
g, 52.2% yield) as a beige solid. H NMR (500 MHz, CDCl3) δ:
8.43 (d, J = 7.5 Hz, 1H), 8.30–8.24 (m, 2H), 7.93 (d, J = 8.0 Hz,
1H), 7.85–7.78 (m, 3H), 7.42 (d, J = 7.5 Hz, 2H), 7.37 (t, J = 7.5
Hz, 2H), 7.32 (t, J = 7.5 Hz, 1H), 7.16 (s, 1H). 13C NMR (125
MHz, CDCl3) δ: 185.10, 182.79, 138.37, 136.49, 135.70, 135.65,
134.78, 134.56, 134.52, 132.77, 130.00, 129.43, 128.82, 128.55,
128.35, 127.94, 127.16, 120.24, 38.72. HRMS (ESI): m/z calcd
for C22H14NO2 [M + H]+ , 324.1019; found, 324.1019.
Scheme 1. Design and working principle of sensor.
In this study, four anthraquinone derivatives 3a-d, were
prepared via the conjugation of C-H group (ArCHCN) at 1-
position of anthraquinone framework. Unfortunately, only nitro-
substituted anthraquinone 3d showed obvious color change and
spectral changes (Fig. 1), which can be used for quantitative
cyanide detection. These visible color and absorption spectra
changes were ascribed to enhanced acidity of C-H proton due to
the presence of the strong electron-withdrawing group (-NO2) as
well as cooperative intramolecular hydrogen bonds (IHBs)
between C=O group of anthraquinone and activated C-H group
promoting auxiliary binding with cyanides. Furthermore, sensor
3d displays high sensitivity, excellent selectivity, reversibility,
reusability, insensitive to pH, large absorption red shift and
usability in water-miscible organic solvents. Surprisingly, it can
not only be used as a solid sensor for cyanide detection, but also
for detection in real water and food samples. To the best of our
knowledge, sensor 3d has not been reported in the relevant
2.2.2. Synthesis of 3b
Under a N2 atmosphere, a well-stirred solution of KOH (0.19 g,
3.31 mmol) in DMF (25 ml) was injected with 2b (0.89 g, 6.61
mmol) at room temperature for 30 min. Then, 1 (0.40 g, 1.65
mmol) was quickly added into the mixture and stirred for another
2 hours. After the reaction was completed, the reaction mixture
was filtered to remove insoluble components. The filtrate was
extracted with ethyl acetate and washed with an appropriate
amount of saturated brine and dried over anhydrous NaSO4.
Finally, the dried solution was concentrated and purified by
column chromatography (PE: EA = 50:1) to obtain 3b (0.21 g,
1
37.5% yield) as a beige solid. H NMR (500 MHz, CDCl3) δ:
8.42 (d, J = 7.5 Hz, 1H), 8.26-8.22 (m, 2H), 7.95 (d, J = 8.0 Hz,
1H), 7.84 (t, J = 8.0 Hz, 1H), 7.80-7.75 (m, 2H), 7.42-7.38 (m,
2H), 7.10 (s, 1H), 7.08-7.02 (m, 2H). 13C NMR (125 MHz,
CDCl3) δ: 185.08, 182.73, 163.73, 161.76, 138.05, 136.26,
135.74, 134.85, 134.67, 134.64, 134.46, 132.74, 130.17, 130.10,
129.87, 128.98, 127.94, 127.22, 120.15, 116.49, 116.32, 38.16.
HRMS (ESI): m/z calcd for C22H13FNO2 [M + Na]+ , 364.0744;
found, 364.0741.
literature
.
1.2
1.2
0.9
0.6
0.3
0.0
(b)
(a)
0.9
0.6
0.3
0.0
-
-
-
-
3a
3d+CN
3c+CN
3b
3c
3d
3b+CN
3a+CN
3d
-
3d+CN
2.2.3. Synthesis of 3c
Under a N2 atmosphere, a well-stirred solution of KOH (0.093
g, 1.65 mmol) in DMF (15 ml) was injected with 2c (0.64 g, 3.31
mmol) at room temperature for 30 min. Then, 1（0.20 g, 0.83
mmol ）was quickly added into the mixture and stirred for
another 2 hours. After the reaction was completed, the reaction
mixture was filtered to remove insoluble components. The filtrate
was extracted with ethyl acetate and washed with an appropriate
amount of saturated brine and dried over anhydrous NaSO4.
Finally, the dried solution was concentrated and purified by
column chromatography (PE: EA = 50:1) to obtain 3c (0.20 g,
400
600
800
1000
400
600
800
1000
Wavelength/nm
Wavelength/nm
Fig. 1. (a) UV-visible absorption spectra of 3a-d (20 μM)in the absence of
CN- in THF/H2O (9:1, v/v) aqueous environments. Inset: visual color of 3a-d
without CN-. (b) UV-visible absorption spectra of 3a-d (20 μM) in the
presence of CN- in THF/H2O (9:1, v/v) aqueous environments. Inset: visual
color of 3a-d with CN-.
2. Materials and methods
2.1. General information
1
60.6% yield) as a yellow solid. H NMR (500 MHz, CDCl3) δ:
8.45 (d, J = 8.0 Hz, 1H), 8.32-8.25 (m, 2H), 7.83-7.79 (m, 2H),
7.77 (t, J = 8.0 Hz, 1H), 7.65 (d, J = 8.0 Hz, 1H), 7.59 (d, J = 8.0
Hz, 1H), 7.50 (d, J = 7.5 Hz, 1H), 7.39 (t, J = 7.5 Hz, 1H), 7.29-
7.25 (m, 1H), 7.12 (s, 1H). 13C NMR (125 MHz, CDCl3) δ:
184.73, 182.82, 136.76, 135.74, 135.60, 134.95, 134.78, 134.53,
134.41, 134.36, 134.07, 132.71, 130.53, 130.46, 130.03, 128.89,
128.37, 128.04, 127.14, 124.74, 118.88, 40.58. HRMS (ESI): m/z
calcd for C22H13BrNO2 [M + H]+ , 404.0105; found, 404.0101.
Unless specifically noted, all solvents and reagents were
analytical grade and used without further purification. All flash
column chromatograpy was carried out on silica gel (200−300
mesh). UV−visible absorption spectra were obtained on a
SHIMADZU UV-1800 spectrophotometer. 1H and 13C NMR
spectra were recorded on a Bruker AVANCE III spectrometer
1
(500 MHz for H NMR, 125MHz for 13C NMR), and chemical
shifts were reported in parts per million (ppm, δ) downfield from
the internal standard, tetramethylsilane (TMS). Multiplicities of
signals are described as follows: s-singlet; d-doublet; t-triplet; m-
multiplet. HRMS were recorded on a solanX 70 FT-MS
spectrometer.
2.2.4. Synthesis of 3d
Under a N2 atmosphere, 2d (0.50 g, 2.07 mmol) was added into
a well-stirred solution of NaH (60%, 0.40 g, 16.53 mmol）in
DMF (30 ml) at room temperature for 30 min. Then, 1 (0.50 g,
2.07 mmol) was quickly added into the mixture and stirred at 120
℃ for another 3 hours. After the reaction was completed, it was
cooled to room temperature and quenched with saturated citric
acid. The solution was extracted with ethyl acetate. The organic
layer was washed with an appropriate amount of water and
saturated brine and dried over anhydrous NaSO4. Finally, the
dried solution was concentrated and purified by column
chromatography (PE: EA = 15:1) to obtain 3d (0.32 g, 42.1%
2.2. Synthesis of sensor 3a-d
2.2.1. Synthesis of 3a
Under a N2 atmosphere, a well-stirred solution of KOH (0.23 g,
4.13 mmol) in DMF (30 ml) was injected with 2a (0.97 g, 8.26
mmol) at room temperature for 30 min. Then, 1 (0.50 g, 2.07
mmol) was quickly added into the mixture and stirred for another
2 hours. After the reaction was completed, the reaction mixture
was filtered to remove insoluble components. The filtrate was
1
yield) as a beige solid. H NMR (500 MHz, CDCl3) δ: 8.50 (d, J

Tetrahedron
3
= 7.5 Hz, 1H), 8.31-8.19 (m, 4H), 8.01 (d, J = 8.0 Hz, 1H), 7.91
(t, J = 8.0 Hz, 1H), 7.85-7.80 (m, 2H), 7.62 (d, J = 9.0 Hz, 2H),
7.22 (s, 1H). 13C NMR (125 MHz, CDCl3) δ: 185.09, 182.50,
148.01, 142.71, 136.43, 136.38, 135.92, 134.98, 134.95, 134.93,
134.27, 132.75, 129.93, 129.52, 129.35, 127.99, 127.36, 124.59,
119.17, 38.84. HRMS (ESI): m/z calcd for C22H13N2O4 [M + Na]
+ , 391.0689; found, 391.0686.
to the nonlinear fitting of the Boltzmann function (Fig. S19). This
confirms sensor 3d good stability toward pH. Moreover, the Job
curves indicate that the binding ratio of sensor 3d to CN− is 1:1
(Fig. S20).
1.2
0.9
0.6
0.3
0.0
1.2
0.9
0.6
0.3
0.0
■
588nm
0.6
0.3
0.0
(a)
(b)
-
CN
3. Results and discussion
-
CN
0
200
400
-
µ
[CN ]/ M
3.1. Synthesis of target sensors
others
As shown in Scheme 2, the target compound 3a-d is obtained
by the nucleophilic substitution reaction between the 1-
chloroanthraquinone (1) and substituted arylacetonitrile (2a-d)
under a N2 atmosphere and alkaline conditions [33]. The final
products (3a-d) were characterized with 1H NMR, 13C NMR, and
HRMS (Figs. S1−S12).
400
600
800
1000
400
600
800
1000
Wavelength/nm
Wavelength/nm
Fig. 2. (a) UV-visible absorption spectra of sensor 3d (20 μM) in the
presence of different anions (ca. 22.0 equiv.) in THF/H2O (9:1, v/v) aqueous
environments. Inset: Color change of the solution after the sensor 3d interacts
−
with different anions (from left to right: sensor 3d only, CN−, F−, H2PO4 ,
−
−
−
AcO−, Cl−, Br−, I−, HSO4 , NO3 , BF4−, ClO4 , SCN−). (b) UV-visible spectra
in 20 μM solutions of sensor 3d upon titration with different CN−
concentrations (0 to 22.0 equiv.) in THF/H2O (9:1, v/v) aqueous
environments. The inset shows the absorbance at 588 nm as a function of
[CN−] and visual color change of sensor 3d with CN-
.
0.6
0.4
0.2
0.0
0.7 (a)
0.6
Scheme 2. Synthesis of 3a-d.
(b)
y = 0.01909+0.00262X
= 0.98293
3.2. UV–vis absorbance of sensor 3d to cyanide (CN−)
2
R
0.5
µ
LOD = 29.48 M
0.4
The selectivity of sensor 3d toward CN- was investigated using
0.3
various of anions including F−, H2PO4 , AcO−, Cl−, Br−, I−,
−
0.2
HSO4 , NO3 , BF4−, ClO4 , and SCN− ions in THF/H2O (v/v, 9:1)
aqueous environments (Fig. 2a). When CN- was added, new
absorption peaks appearing at 588 and 775 nm increased greatly,
demonstrating that sensor 3d possesses excellent selectivity
towards CN- in aqueous solution. In addition, an instantaneous
colorimetric change of the solution in the bottle can be observed
from colorless to blue-purple (Fig. 2a, inset), indicating the
sensor’s capability naked-eye selective cyanide detection.
Moreover, UV-visible absorption titration spectra of sensor 3d
(20 μM) upon titration with CN- were recorded in THF/H2O (v/v,
9:1) aqueous environments (Fig. 2b). Absorption peaks at 588
and 775 nm were progressively augmented with increasing
amount of CN-. The nitro group in 3d can enhance the acidity of
the C-H group promoting to easily binding with the cyanides via
strong hydrogen-bonding interaction, which further facilitates the
process of charge transfer by deprotonation of C-H group to
induce a vivid color change and red-shift signals [34-36]. In Fig.
3a, interference experiments were conducted with the addition of
CN- to the solution of sensor 3d containing equivalent amount of
−
−
−
0.1
0.0
1
2
3
4
5
6
7
8
9
10 11 12
0
100
200
-
µ
[CN ]/ M
Fig. 3. (a) The competitive of sensor 3d (20 μM) for CN− in the presence of
other anions in THF/H2O (9:1, v/v) aqueous environments. The black bars
represent the absorbance at 588 nm of sensor 3d in the presence of 22.0
equiv. of the anion of interest (from left to right: CN−, F−, H2PO4 , AcO−, Cl−,
−
Br−, I−, HSO4 , NO3 , BF4−, ClO4 , SCN−). The red bars indicate the change
that occurs upon subsequent addition of 22.0 equiv. of CN− to the solution
containing the sensor and the anion of interest. (b) The linear relationship
between the absorption at 588nm and the concentration of CN- in the THF/
H2O (9:1, v/v) aqueous environments.
−
−
−
3.3. Reversible and reusable study of sensor 3d
The reversibility and reusability of sensor 3d was further
investigated, using UV−visible absorption titration spectra with
[3d+CN-] complex upon titration with trifluoroacetic acid (TFA)
performed in THF solution (Fig. 4a) [37]. With increasing
amount of TFA, the UV−visible absorption peak at 591 nm
progressively weakens until it was restored to be consistent with
the original UV-visible spectrum of sensor 3d. Therefore, the CH
deprotonation process is reversible. Fig. 4b shows the
potentially interfering anions. Except for H2PO4 , AcO− and
−
−
HSO4 , the observed interference is almost negligible. Fig. 3b
reproducibility experiments of CN- recognition by sensor 3d
.
shows that the absorbance at 588 nm is almost linear with the
concentration of CN-. The detection limit of sensor 3d was
determined to be 29.48 μM (according to formula LOD = 3δ/S)
in THF/H2O (v/v, 9:1) aqueous environments. S and δ in the
formula represent the slope (the absorbance at 588 nm versus
[CN-]) and the standard deviation, respectively. Comparing to
other reported cyanide sensors, 3d has a relatively low detection
limit (LOD) (Table S1). The experiments were also conducted in
pure THF and THF/H2O (v/v, 7:3) aqueous environments,
producing similar results (Figs. S13−S17).
Five consecutive cycles of titrations were performed with CN-,
followed by addition of TFA. Furthermore, the color of the
solution, visible to the naked-eye, in the bottle repeatedly
changes from colorless to blue, and then back to colorless (Fig.
4c). Hence, sensor 3d has excellent reversibility and reusability
features. It is further deduced that the sensor 3d can achieve
reversible recognition by C-H deprotonation with strongly basic
anions and protonation in acidic environments.
Meanwhile, the pH dependence of sensor 3d (20 μM) in the
absence and presence of CN- (ca. 22.0 equiv.) in THF/H2O (v/v,
9:1) solution was evaluated for potential applicability (Fig. S18).
The results showed that sensor 3d can detect CN- in a moderate
range of 3–11, where the pKa of CH proton was 11.6 according

4
Tetrahedron
1.0
0.8
0.6
0.4
0.2
0.0
(b)
0.6
0.3
0.0
(a)
■
591nm
CN-
0.6
0.4
0.2
0.0
TFA
0
20
40
µ
TFA/ M
TFA
400
600
800
1000
0
2
4
6
8
10
Wavelength/nm
Cycles
-
-
-
-
-
CN
CN
CN
CN
CN
(c)
TFA TFA TFA TFA
TFA
Fig. 4. (a) UV-visible spectral changes of [3d+CN-] (20 μM) upon titration
with TFA (0-1.4 equiv.) in THF. The inset shows the absorbance at 591 nm
as a function of [TFA]. (b) UV-visible absorbance intensity obtained during
the titration of sensor 3d with CN- and H+ (TFA) in THF. (c) Visual color
changes after cyclic titration of saturated equivalents CN- and H+ (TFA) in
THF.
3.4. Theoretical calculations
Density functional theory (DFT) calculations were carried out in
Gaussian 09 software [38] to further clarify the electronic
structure and observed spectroscopic properties of sensor 3d
before and after binding with CN- [39,40]. The optimized
molecular geometries of sensor 3d and 3d+CN- are shown in Fig.
5. Upon sensor 3d interacting with CN-, the dihedral angle of
anthraquinone and substituted arylacetonitrile change from
98.23° to 130.67°, which indicating that the coplane of the whole
molecular increases and leads to a significant red shift in UV-
visible absorption. According to the calculations, an
intramolecular (CH…O=C) distance of 2.1506 Å of sensor 3d
can be estimated, which is a similar interaction required to form
potential intramolecular hydrogen bonds (IHBs) between C=O
group of anthraquinone and activated C-H group for auxiliary
binding with cyanides. Moreover, the energy gap (ΔE) between
the highest occupied molecular orbital (HOMO) and lowest
unoccupied molecular orbital (LUMO) of sensor 3d is 6.65 eV,
whereas for [3d+CN-] is 3.38 eV. The significant reduction of
HOMO-LUMO energy gap upon interaction with CN- is
associated with the bathochromic shift (～262nm) in the UV-
visible band of sensor 3d. Therefore, DFT results support the
observed absorption wavelengths.
Fig. 5. Optimized molecular geometries and HOMO-LUMO energy level
diagrams of sensor 3d and 3d+CN-.
f
d
e
b
a
g
h
3.5. 1H NMR titration experiments
a
h
b
e
g
In order to further investigate the deprotonation of CH in sensor
1
3d with cyanide, a series of H NMR titrations were performed
on 3d in DMSO-d6 (Fig. 6). On increasing amount of cyanide,
the signal peak of CH proton at 7.05 ppm (Hc) gradually
8.0
7.7
7.1
6.5
6.2
Fig. 68..31H NMR titration spec7tr.4a of sensor 3d6(.830 mM) in DMSO-d6
upon addition of various equivalents CN− (as salts in DMSO-d6). From
bottom to top: sensor 3d, 0.2, 0.4, 0.6, 0.8, 1.0 equiv.
disappeared and
a new signal appeared at 6.38 ppm
concomitantly. When 1.0 eq of CN- was added, the CH signal at
6.38 ppm (Hc) disappeared completely and other aromatic
hydrogen peaks moved to the high field to varying degrees.
Among them, the proton signal peak (Ha) on the nitrophenyl ring
moved to the high field with a great extent. The addition of
higher concentrations of CN- did not cause any other changes in
the 1H NMR titration. Thus, the CH deprotonation mechanism of
the sensor 3d with cyanide is final confirmed.
3.6. Practical applications [41]
Due to senor 3d favorable features in solution, probe-loaded test
strips were fabricated for solid-state cyanide detection to
demonstrate the sensor’s potential practical applicability. The test
strips were prepared through immersion of filter paper strips in
THF solution (1 mM) of sensor 3d for 3 h. After removal of the
test strips, they were air-dried. Subsequently, the prepared test
strips were placed in CN- solutions of varying concentration, and
then removed and left to dry at room temperature. The color of
the test strips change from colorless to light blue and finally dark
blue with increasing CN− concentration, as observed by the
naked-eye (Fig. 7a). Interestingly, the feasibility of reversible
cyanide detection on test strips was verified using TFA (Fig. 7b).
This indicates the suitability of sensor 3d for solid state sensing.

Tetrahedron
5
Furthermore, these test strips still had a clear identification effect
2.0
1.5
1.0
0.5
0.0
on CN- even they were stored for more than 5 days (Fig. S21).
Under solid-state conditions, the sensor 3d still had relatively
good selectivity to CN- (Fig. S22). Therefore, sensor 3d is
suitable as a portable colorimetric cyanide detector for selectively
detect cyanide in practical applications.
NO2
NC
O
O
3d
Cassave Flour
Bitter Almond
3d
3d + Cassave Flour
3d + Bitter Almond
400
600
800
1000
Wavelength/nm
Fig. 8. Visible color changes observed for sensor 3d upon addition of
these food extracts and absorbance spectra response of 3d in these
diluted food samples.
Table 1. Determination of CN− in spiked water samples (n = 6)
Recovery
(%)
Samples
Spilked/μM
Found/μM
SD (%)
Drinking
water 1
Drinking
water 2
Drinking
water 3
50
50.13
100.27
99.75
99.70
0.56
0.51
1.27
Fig. 7. (a) Photograph of test strips of sensor 3d after exposure to
various concentrations of CN- solution under natural light. (b)
Photograph of test strips after sequential addition of CN- and H+ (TFA).
120
200
119.79
199.39
Furthermore, it is necessary to explore the potential application
of sensor 3d for the determination of endogenous biological
cyanides in various food samples. Cassava flour and bitter
almonds food samples were infused in aqueous sodium
hydroxide, followed by ultrasonic treatment, filtration,
centrifugation, and pH adjustment to obtain the final cyanide
solutions. As shown in Fig. 8, the titration of sensor 3d (20 μM)
with the extracts of these food samples induce an obviously color
change, which is similar to the UV-visible response to CN- in
aqueous solution. After the addition of the cassava flour extracts
to sensor 3d solution, new absorption peaks appear at 587 and
729 nm, as well as a color change from colorless to blue-purple.
Similarly, the addition of bitter almond extracts to sensor 3d
solution shows new absorption peaks at 587 and 751 nm, with a
similar visible color change. Therefore, sensor 3d can be applied
to cyanide detection in cassava flour and bitter almonds with
naked-eye determination, revealing its great potential for
practical application in our daily life and health sciences.
4. Conclusions
In summary, a novel anthraquinone-based colorimetric sensor
3d with activated C-H group for detection CN− in 10% aqueous
solution was developed, which displayed excellent performance,
such as naked-eye color changes from colorless to blue-purple,
high sensitivity, excellent selectivity, reversibility and reusability,
and insensitive to pH. In addition, colorimetric sensor 3d was
employed as a solid-state sensor, which could be potentially used
in reversible cyanide detection in “in-the-field” measurements.
Importantly, sensor 3d has been successfully applied to the
qualitative determination of cyanide in food and real-world water
samples. The mechanism of CH-deprotonation was fully
investigated by 1H NMR titrations and DFT calculations. Overall,
this work provides a new strategy for the development of
anthraquinone-based sensors for cyanide detection based on
activated C-H groups.
Moreover, 3d was utilized to sense cyanide in drinking water,
tap water and river water. It was carried out in water samples
mixed with 90% THF with different spiked concentrations of CN-
. The results were summarized in Table 1, Table S2 and Fig. S23.
By comparing the experimental data in the three water samples, it
was found that the analysis accuracy of CN- in drinking water
was satisfactory. These results prove that sensor 3d is capable of
qualitative sensing cyanide in real water samples.
Declaration of competing interest
There are no conflicts of interest to declare.
Acknowledgments
We thank the Natural Science Foundation of Shanghai (No.
17ZR1429900) and the Opening Fund of Shanghai Key
Laboratory of Chemical Biology for financial support.
Appendix A. Supplementary data
Supplementary data to this article can be found online at
https://doi.org/

6
Tetrahedron
[40] Z. Wang, Y. Zhang, J. Song, Y. Wang, M. Li, Y. Yang, X. Xu, H.
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Highlights
1.
2.
3.
Novel colorimetric sensor based on anthraquinone linking an activated C-H group was developed.
The sensor can detect cyanides with high selectivity and sensitivity in aqueous solution.
The sensor exhibited satisfactory analytical performance in terms of reversibility.
4. The sensor was successfully applied to detect CN− in test paper strips, food and water samples.
5. The sensor has a large absorption red shift.

Declaration of interests
☒ The authors declare that they have no known competing financial interests or personal relationships
that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which may be considered
as potential competing interests: