Ratiometric luminescence detection of hydrazine with a carbon dots-hemicyanine nanohybrid system

Article abstract of DOI:10.1039/c6ra27844b

It is significant to develop probes for rapid, selective, and sensitive detection of highly toxic hydrazine in both environmental and biological science. In this work, under mild conditions, through the electrostatic attraction between negatively charged CDs and positively charged hemicyanine molecules, a novel ratiometric fluorescent probe containing CDs and a hemicyanine derivative was fabricated for reliable, selective, and sensitive sensing of hydrazine. This nanohybrid system possesses dual emission peaks at 550 and 610 nm under a single excitation wavelength of 530 nm. The addition of hydrazine to CDs-hemicyanine nanohybrid solution results in complete fluorescence quenching of the hemicyanine derivative, while the orange fluorescence of CDs remains constant. Furthermore, the CDs-hemicyanine nanohybrid system shows high selectivity toward hydrazine over other various species, including some nucleophilic species, metal ions and anions. The limit of quantification (LOQ) was 0-1 mM and the detection limit was as low as 8.0 μM.

Full text of DOI:10.1039/c6ra27844b

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Ratiometric luminescence detection of hydrazine
with a carbon dots–hemicyanine nanohybrid
system†
Cite this: RSC Adv., 2017, 7, 10875
Zhen An, Zhanxian Li,* Yangyang He, Bingjie Shi, Liuhe Wei and Mingming Yu*
It is significant to develop probes for rapid, selective, and sensitive detection of highly toxic hydrazine in
both environmental and biological science. In this work, under mild conditions, through the electrostatic
attraction between negatively charged CDs and positively charged hemicyanine molecules, a novel
ratiometric fluorescent probe containing CDs and a hemicyanine derivative was fabricated for reliable,
selective, and sensitive sensing of hydrazine. This nanohybrid system possesses dual emission peaks at
5
50 and 610 nm under a single excitation wavelength of 530 nm. The addition of hydrazine to CDs–
hemicyanine nanohybrid solution results in complete fluorescence quenching of the hemicyanine
derivative, while the orange fluorescence of CDs remains constant. Furthermore, the CDs–hemicyanine
nanohybrid system shows high selectivity toward hydrazine over other various species, including some
nucleophilic species, metal ions and anions. The limit of quantification (LOQ) was 0–1 mM and the
detection limit was as low as 8.0 mM.
Received 6th December 2016
Accepted 4th February 2017
DOI: 10.1039/c6ra27844b
rsc.li/rsc-advances
Therefore, it is difficult to detect trace hydrazine in situ, fast and
low cost in room temperature. On the other hand, uorescence-
Introduction
As a highly reactive base and reducing agent, hydrazine plays based method has been widely used to detect various analytes
crucial roles in the chemical, pharmaceutical and agricultural such as metal ions, anions and biomolecules due to its simplicity,
1–3
industries. Due to its detonable characteristics, hydrazine is high sensitivity, rapid response, capacity of real-time and in situ
9
–13
also a high-energy fuel for rocket-propulsion systems and monitoring of the dynamic biological processes in living cells.
4
missile systems. However, hydrazine is classed as a highly toxic However, available uorescent probes for hydrazine are still very
and pollutant compound, which can potentially lead to serious limited and most of them are turn-on types.
environmental contamination during its manufacture, use,
As we all know, the emission intensity may be inuenced by
14–24
transport and disposal. In addition, as a neurotoxin, hydrazine many factors, such as optical path length and the illumination
has several mutagenic effects, which can cause damage to the intensity, which are prone to disturbance in quantitative detec-
5
–7
liver, lungs, kidneys and central nervous system of humans.
tion. In addition, when turn-on mode uorescent probes are used
Besides, hydrazine is readily absorbed through oral, dermal or in complicated biosystems, the detection is inuenced by the
inhalation routes of exposure and it can cause harm to live cells. probe concentration, autouorescence, and instrumental factors.
Due to its widespread application, easy absorbance, and high A ratiometric approach can eliminate the effects of these factors
toxicity, hydrazine has been classied as a probable human and realize more effective quantitative detection through
carcinogen by the U.S. Environmental Protection Agency and measuring the ratio of uorescence intensities at two different
8
25
has a low threshold limit value of 10 ppb. Thus, an efficient and wavelengths. On the other hand, uorescent probes could be
simple method for determining hydrazine levels is urgently signicantly inuenced by excitation power and detector sensi-
needed in both environmental and biological science.
Approaches such as chromatography-mass spectrometry, direct observation with the naked eye because they are based on
tivity. By comparison, colorimetric probes are more suitable for
26–28
titration and electrochemical methods are available to measure absorption properties of the ground state.
Up to now, very few
hydrazine, but they oen require complicated equipment and ratiometric uorescent and colorimetric probes toward hydrazine
29–35
sample handling and professional operating personnel. have been reported.
Therefore, it is of great interest to design
ratiometric uorescent and colorimetric probes for hydrazine.
As an ideal ratiometric uorescent sensing mode, uores-
cence resonance energy transfer (FRET) has been widely adop-
ted in ratiometric detection because of its facile control and
College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou
4
6
†
50001, China. E-mail: lizx@zzu.edu.cn; yumm@zzu.edu.cn; Fax: +86 371
7781205; Tel: +86 371 67781205
36
basis on established theory. For a FRET system, the use of the
Electronic supplementary information (ESI) available: Synthesis procedure and
ratio of two interconnected uorescence signals as the detection
spectral data. See DOI: 10.1039/c6ra27844b
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Fig. 1 Dual-emission fluorescence sensing of hydrazine based on
a CDs–hemicyanine nanohybrid system.
index could effectively eliminate the background interference
37,38
and the uctuation of detection conditions.
On the other hand, due to their small size, tunable surface
functionalities and good photostability, carbon nanodots (CDs)
Fig. 2 (a) TEM image of the as-prepared CDs, (b) HRTEM image of the
have many excellent properties such as good water solubility, as-prepared CDs, (c) diameter distribution of the as-prepared CDs.
biocompatibility, excellent cell membrane permeability and low
3
9–43
cost.
Such features make CDs especially useful for uorescent
surface negative electricity of the CDs. FT-IR spectra (Fig. S1 in
ESI†) reveal that the CDs mainly contain carbon, nitrogen, oxygen,
and the surfaces of the CDs are functionalized with amino,
hydroxyl, and carboxylic/carbonyl moieties.
Hemicyanine derivative 1 was selected as the sensing unit
and energy accepter, which was synthesized in a high yield
starting from p-hydrazinobenzoic acid hydrochloride through
three steps. The reaction of p-hydrazinobenzoic acid hydro-
chloride and dimethylacetone gives product 3. Compound 2 was
obtained with a yield of 44.7% by the reaction of compound 3
44–48
biosensing or imaging.
However, exploration of CDs as uo-
rescent probes still remains at an early stage and no reports about
CDs uorescent probe toward hydrazine has been reported.
In this paper, we describe the rst example of a FRET-based
CDs–hemicyanine nanohybrid ratiometric probe toward hydra-
zine. In this probe, the CDs not only serve as the energy donor,
but also as the anchoring site for the probe, a hemicyanine
derivative. The schematic illustration for the selective detection
of hydrazine by the CDs–hemicyanine probe is shown in Fig. 1.
The probe based on this CDs–hemicyanine architecture demon-
strates several advantages: it is a FRET-based ratiometric probe
toward hydrazine which can ensure more accurate detection with
a detection limit of 8 mM, and it also has a large shi (80 nm)
between donor excitation and acceptor emission, which rules out
any inuence of excitation backscattering effects on uorescence
and CH
3
I. The reaction of 2 and 4-diethylaminobenzaldehyde
gives product 1 in a yield of 31.6%. Probe 1 was characterized by
1
13
H NMR, C NMR and HRMS.
Hydrazine sensing properties
detection. Moreover, due to the l -dependent PL emission of the
CDs, we can readily control the emission wavelength of the donor
ex
Fig. 3a and b and present the absorption and uorescence
spectra of probe 1 upon addition of hydrazine. It was clear that
the absorbance at about 577 nm and emission at 610 nm
decreased dramatically in the presence of hydrazine and
completely disappeared when the concentration of hydrazine was
up to 1 mM. The absorption and uorescence spectra change of
probe 1 by hydrazine is presumably due to the reaction of probe 1
and hydrazine. However, the emission spectrum of the CDs
hardly changes upon addition of hydrazine, and the slight
(CDs) and allow for precise energy matching between the donor
and the acceptor of the FRET system, which is benecial to
detection accuracy.
Results and discussions
Synthesis of probe 1 and preparation of CDs
For the fabrication of the sensing system, rst we synthesized change was presumably due to electron/hole annihilation
amino and carboxyl coated CDs by a simple hydrothermal method through effective electron or energy transfer process, which
using citric acid and ethylenediamine as the precursors. Fig. 2a resulted from the strong electrostatic interaction between CDs
indicates the TEM image of as-prepared CDs. Well-resolved lattice and hydrazine (Fig. 3c). Prior to probe preparation, the interac-
fringes are observed in high-resolution TEM (HRTEM, Fig. 2b) tion between CDs and probe 1 in the hybrid system was rst
image. The diameter distribution of the CDs is about 2.72 nm and investigated by monitoring their absorption and uorescence
the zeta potential is ꢀ30.4 mV (Fig. 2c), which is ascribed to the spectra changes. As shown in Fig. 3d, the maximum absorption
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Fig. 3 Absorption (a) and fluorescence (b) titration spectra of probe 1
ꢀ
5
(
1.0 ꢁ 10 M, VDMSO/Vwater ¼ 9/1) upon gradual addition of hydrazine
from 0 to 1 mM. (c) Fluorescence spectra change of CDs (water, 0.01 mg
ꢀ1
ꢀ5
mL ) with excitation at 530 nm. (d) Absorption of probe 1 (1.0 ꢁ 10 M,
DMSO/Vwater ¼ 9/1) (black line) and fluorescence spectrum of CDs
V
(
ꢀ1
water, 0.01 mg mL ) with excitation at 530 nm (red line).
peak of probe 1 is at about 577 nm and the emission peak of CDs
is at about 550 nm upon excitation at 530 nm. That is to say, there
is a good overlap between the absorption spectrum of probe 1
and the PL spectrum of CDs, indicating that the energy transfer
efficiency from CDs to probe 1 may be high. Therefore, it is
possible to select a 530 nm wavelength laser to excite CDs in the
hybrid probe. Upon 530 nm excitation, the emission of CDs was
absorbed by probe 1 and the nanohybrid system exhibits one very
strong emission peak at 610 nm and a very weak emission peak at
Fig. 4 (a) Absorption and (b) emission spectra of the CDs–hemi-
cyanine nanohybrid system [Vwater/VDMSO ¼ 1/9] upon titration of
hydrazine water solution (0–100 equiv. to 1) with excitation at 530 nm.
5
50 nm. To obtain a ratiometric uorescence probe with an The reaction time is 60 min hydrazine concentration from left to right:
ꢀ
4
ꢀ4
ꢀ4
ꢀ4
0
M, 1.0 ꢁ 10 M, 2.0 ꢁ 10 M, 3.0 ꢁ 10 M, 4.0 ꢁ 10 M, 5.0 ꢁ
ꢀ4 ꢀ4 ꢀ4 ꢀ4 ꢀ4
appropriate color variation during sensing, we prepared
a mixture solution containing CDs (0.01 mg mL ) and probe 1
ꢀ1
10 M, 6.0 ꢁ 10 M, 7.0 ꢁ 10 M, 8.0 ꢁ 10 M, 9.0 ꢁ 10 M, 1.0 ꢁ
ꢀ3
1
0
M. Photographs of the CDs–hemicyanine nanohybrid system
(10 mM) as the probe solution for hydrazine detection.
[
V
water/VDMSO ¼ 1/9] upon addition of hydrazine at various concen-
ꢀ4
ꢀ4
ꢀ4
ꢀ4
To study the sensing properties of the CDs–hemicyanine
trations (0 M, 1.0 ꢁ 10 M, 2.0 ꢁ 10 M, 3.0 ꢁ 10 M, 4.0 ꢁ 10 M,
ꢀ4
ꢀ4
ꢀ4
ꢀ4
ꢀ4
nanohybrid system toward hydrazine, UV-Vis and uorescence 5.0 ꢁ 10 M, 6.0 ꢁ 10 M, 7.0 ꢁ 10 M, 8.0 ꢁ 10 M, 9.0 ꢁ 10 M,
ꢀ
3
1
.0 ꢁ 10 M, from left to right) in water in daylight (c). The reaction
titration experiments (Fig. 4) were conducted with 0–1 mM
hydrazine water solution in aqueous solution of CDs–hemi-
cyanine nanohybrid system (Vwater/VDMSO ¼ 1/9). Upon addition
of hydrazine, the absorbance at 561 nm in the UV-Vis spectra
time is 20 min. (d) CIE 1931 (x, y) chromaticity diagram of the solutions
for the detection of hydrazine at different concentrations.
decreased gradually with the original peak at 317 nm changing of hydrazine (Fig. 4c). The Commission Internationale de
a little, and then, the peak at 561 nm reached the minimum at L'Eclairage (CIE) 1931 (x, y) chromaticity diagram of the solutions
1
5
5
00 equiv. of hydrazine (Fig. 4a). Accordingly, upon excitation at aer addition of different concentrations of hydrazine for 30
30 nm, the emission intensity at 610 nm decreased and that at minutes are shown in Fig. 4d. When the hydrazine concentration
50 nm increased with increasing hydrazine concentration was increased, the uorescence color of the solution changed
(Fig. 4b). The decrease of the absorption peak at 561 nm and that from red to orange. All of the above spectra, solution and uo-
at 610 nm in emission spectrum is ascribed to the reaction of rescence color change implied that probe 1 can serve as not only
hydrazine and probe 1. The increase of the emission peak at a highly sensitive ‘naked-eye’ probe but also a ratiometric uo-
550 nm can be explained as below: upon excitation at 530 nm and rescence probe for hydrazine.
with no hydrazine, the emission at 550 nm of the CDs was mostly
Fig. 5a suggested a good linear relationship between the ratio
absorbed by probe 1 and gave a strong emission at 610 nm; with of I550/I610 with hydrazine concentration in the range of 0 and
the addition of hydrazine, a new compound was obtained, which 1 mM, implying that hydrazine can be quantitatively detected in
cannot absorb energy at 550 nm and no emission at 610 nm was a wide concentration range in ratiometric uorescence mode.
given, thus, the emission at 550 nm increased and that at 610 nm From the linear calibration graph with the uorescence titration
decreased. Moreover, the solution color of 1 changed by degrees experiment (Fig. 5a), the detection limit of probe CDs–hemi-
from pink to colorless in the presence of different concentrations cyanine for hydrazine was gured out to be about 8.0 mM based
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Fig. 5 The linearity of emission intensity of the CDs–hemicyanine
nanohybrid system (Vwater/VDMSO ¼ 1/9) with respect to hydrazine
concentrations. The excitation wavelength was 530 nm and the
reaction time is 60 min (a). Kinetics of fluorescence change rate by the
reaction of the CDs–hemicyanine nanohybrid system [Vwater/VDMSO
¼
ꢀ3
1
/9] and hydrazine (the concentration of hydrazine is 1.0 ꢁ 10 M) (b).
I
550 and I610 represent the emission intensity at 550 nm and 610 nm.
Fig. 6 Fluorescence response (red bars) of the CDs–hemicyanine
nanohybrid system (Vwater/VDMSO ¼ 1/9) upon addition of different
species (100 equiv. of species relative to 1), and fluorescence changes
4
9,50
on signal-to-noise ratio (S/N) ¼ 3.
These results led us to
(green bars) of the mixture of the CDs–hemicyanine nanohybrid
conclude that CDs–hemicyanine nanohybrid system could be an system (Vwater/VDMSO ¼ 1/9) and hydrazine hydrate (1 mM in water)
after addition of an excess of the indicated species (100 equiv. relative
effective ratiometric uorescent probe for hydrazine.
Time-dependent uorescence experiments on the CDs–hemi-
cyanine nanohybrid system toward hydrazine the CDs–hemi-
to 1) (green bars). The excitation wavelength was 530 nm and the
reaction time was 60 min. I550 and I610 represent the emission intensity
at 550 nm and 610 nm. The species used were His, lle, Val, Asn, Thr,
cyanine nanohybrid system hydrazine is completely accomplished
within 190 min and hydrazine can be detected within 60 min when
the concentration of hydrazine is higher or equal to 1.0 ꢁ 10 M.
Ser, Trp, Glc, Pro, Tyr, Leu, Lys, GSH, Glu, Gly, Met, Ala, Phe, Cys.
ꢀ
3
species (His, lle, Val, Asn, Thr, Ser, Trp, Glc, Pro, Tyr, Leu, Lys,
GSH, Glu, Gly, Met, Ala, Phe, Cys), various metal ions (Na ,
+
The sensing mechanism
2
+
3+
+
2+
3+
2+
3+
2+
2+
2+
2+
Mg , Al , K , Ca , Cr , Mn , Fe , Co , Ni , Cu , Zn ,
The sensing mechanism was studied by mass spectra. For pure
probe 1, a characteristic peak at m/z ¼ 3777.2227 was obtained
which corresponds to the species [M ꢀ I], whilst on reaction of
hydrazine, the peak at 3777.2224 disappeared and one new peak
appeared at m/z ¼ 192.1499 corresponding to the species [4 + H].
Such mass spectra data conrm that compound 4 was formed
through the reaction of hydrazine with probe 1 (Scheme 1).
2
+
2+
2+
ꢀ
2ꢀ
2ꢀ
ꢀ
2ꢀ
Cd , Hg , Pb ) and anions (CH
3
ꢀ
COO , SO
4
, SO
3
, HS ,
2
ꢀ
ꢀ
4ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
S
2
O
3
, S
2
, P
2
O
7
, NO
3
, N
3
, I , HSO
4
, HSO
3
, HPO
4
,
3ꢀ
2
4ꢀ
ꢀ
4ꢀ
3
ꢀ
ꢀ
2
4
2ꢀ
ꢀ
HCO , H
PO , F , ClO , ClO
, Cl , C
O
, and Br ) were
tested. As shown in the red bars of Fig. 6, S3 and S4 in the ESI,†
only the introduction of hydrazine to the CDs–hemicyanine
nanohybrid system solution induced a signicant uorescence
change. In the same condition, other tested species mentioned
above did not induce any obvious uorescence change to the
CDs–hemicyanine nanohybrid system solution.
The selectivity study of the CDs–hemicyanine nanohybrid
system for hydrazine
To evaluate the selectivity of the CDs–hemicyanine nanohybrid The anti-disturbance effect study of the CDs–hemicyanine
system for hydrazine, various species including some biological nanohybrid system for hydrazine detection
To further assess its utility as a hydrazine-selective ratiometric

uorescent probe, its uorescence spectral response to hydra-
zine in the presence of other species mentioned above (green
bars of Fig. 6, S3 and S4†) was also tested. The results demon-
strated that all of the selected species have no interference in
2
+
the detection of hydrazine except some metal ions such as Mg ,
3
+
2+
3+
3+
2+
2+
2+
2+
2+
2+
Al , Ca , Cr , Fe , Co , Cu , Zn , Cd , Hg and Pb . This
result strongly indicates that the CDs–hemicyanine nanohybrid
system could be an excellent ratiometric uorescent probe
towards hydrazine with strong anti-interference ability.
Experimental section
Materials and methods
p-Hydrazinobenzoic acid hydrochloride, dimethylacetone,
3
CH I, AcOH, AcONa, 4-diethylaminobenzaldehyde, His, lle, Val,
Asn, Thr, Ser, Trp, Glc, Pro, Tyr, Leu, Lys, GSH, Glu, Gly, Met,
Scheme 1 Synthesis of the probe 1 and the proposed mechanism of
the response of 1 to hydrazine.
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Ala, Phe, Cys, NaCl, MgCl
2
, AlCl
3
, KNO
3
, CaCl
2
, CrCl
3
, MnCl
2
,
Absorption and uorescence assay of hydrazine
FeCl , CoCl , NiCl , CuCl , ZnCl , CdCl , HgCl , Pb(NO ) ,
3
2
2
2
2
2
2
3 2
The detection of hydrazine was performed in the mixture of
CH COONa, Na SO , NaHS, Na S O , NaS , Na P O , NaN , KI,
3
2
3
2
2
3
2
4
2
7
3
DMSO and water solution (VDMSO/Vwater ¼ 9/1) at room
NaHSO , NaHSO , Na HPO , NaHCO , NaH PO , NaF, NaClO ,
4
3
2
4
3
2
4
4
temperature. In a typical run, 30 mL of CDs dispersion solution
NaClO
3
, Na
2
C
2
O
4
, and KBr. All commercial grade chemicals and
ꢀ1
(
1 mg mL ) was added into 3 mL mixed solution mentioned
solvents were purchased and were used without further puri-
above in the presence of 10 mM probe 1, followed by the addition
of calculated amount of hydrazine. The sensitivity and selec-
tivity measurements were conducted in triplicate.
cation. Mass spectra were obtained on high resolution mass
1
13
spectrometer (IonSpec4.7 Tesla FTMS-MALDI/DHB). H and
C
NMR spectra were recorded on a Bruker 400 NMR spectrometer.
Chemical shis are reported in parts per million using tetra-
methylsilane (TMS) as the internal standard. All spectral char- Conclusions
ꢂ
acterizations were carried out in HPLC-grade solvents at 20 C
A novel ratiometric uorescent probe containing CDs and
within a 10 mm quartz cell. UV-Vis absorption spectra were
measured with a TU-1901 double-beam UV-Vis spectropho-
tometer. Fluorescence spectroscopy was determined on a Hita-
chi F-4600 spectrometer. Fourier transform infrared
spectroscopy (FTIR) was performed on a NEXUS-470 spectrom-
a hemicyanine derivative was fabricated for reliable, selective,
and sensitive sensing of hydrazine. The probe was built through
the electrostatic attraction between negatively charged CDs and
positively charged hemicyanine molecule. This nanohybrid
system possesses dual emission peaks at 550 and 610 nm under
a single excitation wavelength of 530 nm. The addition of
hydrazine to CDs–hemicyanine nanohybrid solution results in
complete uorescence quenching of the hemicyanine derivative
ꢀ
1
eter at frequencies ranging from 400 to 4000 cm . Samples for
transmission electron microscopy (TEM) analysis were prepared
by drying a colloidal solution of nanoparticles on amorphous
carbon-coated copper grids. Low-resolution TEM were operated
on a JEOL-JEM 2100 transmission electron microscopy operated
at 200 kV. High resolution TEM (HRTEM) were carried out on
a JEOL-JEM 2100F eld emission transmission electron micro-
scope operated at 200 kV. The particle size and zeta potential of
1, while the orange uorescence of CDs keeps constant.
Furthermore, the CDs–hemicyanine nanohybrid system shows
high selectivity toward hydrazine over other various species
including some biological species, metal ions and anions.
ꢀ
1
the CDs (0.5 mg mL ) were recorded on a zetasizer (Nanoplus-
3
, Micromeritics, the United States).
Probe 1 was synthesized according to Scheme 1. Compounds
Acknowledgements
51
We are grateful for the nancial supports from National Natural
Science Foundation of China (21601158 and U1504203), Key
Laboratory of Photochemical Conversion and Optoelectronic
Materials and Zhengzhou University.
3
and 2 were obtained following the recently reported method.
Synthesis of compound 2. Compound 3 (1.0 g, 4.93 mmol)
and CH I (700 mg, 4.93 mmol) were dissolved in 10 mL
3
acetonitrile. The mixture was reuxed for 12 hours and then
allowed to cool to room temperature. By ltration of the above
mixture, the solid was obtained as product 2 (0.76 g, 44.7%):
Notes and references
1
H NMR (400 MHz, DMSO-d , TMS): dH 8.38 (s, 1H), 8.19
6
(
d, 1H), 8.03 (d, 21H), 4.00 (s, 3H), 2.82 (s, 3H), 1.57 (sd, 6H).
1 J. Sanabria-Chinchilla, K. Asazawa, T. Sakamoto, K. Yamada,
H. Tanaka and P. Strasser, J. Am. Chem. Soc., 2011, 133, 5425–
5431.
2 T. Sakamoto, K. Asazawa, J. Sanabria-Chinchilla,
U. Martinez, B. Halevi, P. Atanassov, P. Strasser and
H. Tanaka, J. Power Sources, 2014, 247, 605–611.
3 A. Serov, M. Padilla, A. J. Roy, P. Atanassov, T. Sakamoto,
K. Asazawa and H. Tanaka, Angew. Chem., Int. Ed., 2014,
53, 10336–10339.
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5 R. Ahmad, N. Tripathy, D. U. J. Jung and Y. B. Hahn, Chem.
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1
3
C NMR (100 MHz, DMSO-d
41.72, 132.04, 130.83, 124.68, 115.85, 54.72, 35.52, 21.96,
and 15.12.
Synthesis of probe 1 (ref. 52). Compound 2 (690 mg, 2.0
6 C
): d 199.48, 166.95, 142.42,
1
mmol), and 4-diethylaminobenzaldehyde (354 mg, 2.0 mmol)
were dissolved in 10 mL ethanol. The mixture was reuxed for 3 h
at 80
product (probe 1, 318.6 mg, 31.6%) was obtained by ltration and
being washed with ethanol for three times. Characterization of 1:
HRMS (EI) m/z: calcd for C24
3
8
6
ꢂ
C and cooled to room temperature. The nal
H
30IN
2
O
2
[M ꢀ I], 3777.2224; found,
77.2227. H NMR (400 MHz, DMSO-d , TMS): d 13.09 (s, 1H),
.37 (d, 1H), 8.29 (s, 1H), 8.10 (d, 3H), 7.74 (d, 1H), 7.22 (d, 1H),
1
6
H
1
3
.91 (d, 2H), 3.94 (s, 3H), 3.59 (q, 4H), 1.78 (s, 6H), 1.20 (t, 6H).
C
NMR (100 MHz, DMSO-d ): dC 180.75, 167.25, 155.57, 153.64,
6 S. D. Zelnick, D. R. Mattie and P. C. Stepaniak, Aviat., Space
Environ. Med., 2003, 74, 1285–1291.
7 Y. Qian, J. Lin, L. J. Han, L. Lin and H. L. Zhu, Biosens.
Bioelectron., 2014, 58, 282–286.
6
1
1
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