Y.-L. Qi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (xxxx) xxx
3
Then, the mixture was extracted with dichloromethane for 3 times.
The organic layer was collected, evaporated and dried. The target
product was obtained as a colorless solid without further purifi-
systems, with the addition of NH2NH2, the absorption peaks of
three probes decreased at near 300 nm. QYL-1 was chosen for the
following procedures due to the excitation wavelength (371 nm
versus 320 nm or 310 nm), emission wavelength (480 nm versus
400 nm or 410 nm) and Stoke Shift (180 nm versus 90 nm or
110 nm). When the NH2NH2 concentration was increased to 40
equiv of the probe concentration, the fluorescence intensity of
probe QYL-1 attained a 49-fold enhancement, while that of probe
QYL-2 increased by 1.1-fold and QYL-3 increased by 1.4-fold. The
fluorescence quantum yield was 0.19 for QYL-1, which was suitable
for a turn-on system. Then the sensing system consisting of QYL-1
cation (119 mg, 88%). 1H NMR (600 MHz, DMSO‑d6)
d 8.17 (d,
J ¼ 7.9 Hz, 1H), 8.11 (d, J ¼ 7.9 Hz, 1H), 7.90e7.87 (m, 1H), 7.58 (d,
J ¼ 7.3 Hz, 1H), 7.51 (t, J ¼ 7.5 Hz, 1H), 7.45 (t, J ¼ 8.1 Hz, 1H), 7.36 (d,
J ¼ 8.1 Hz, 1H), 3.87 (s, 3H), 2.47 (s, 3H). 13C NMR (151 MHz,
DMSO‑d6)
d 168.70, 162.14, 152.62, 152.26, 137.96, 135.24, 127.59,
127.19, 126.90, 126.22, 123.47, 122.63, 120.88, 115.46, 56.79, 39.98,
21.47. MS (ESI-TOF m/z): Calculated for [C16H13NO3SNa]þ
([MþNa]þ): 322.0, Found: 322.0. Anal. Calcd. for C16H13NO3S: C
64.20, H 4.38, N 4.68, found: C 64.28, H 4.38, N 4.67.
(10 mM) and hydrazine (400 mM) in PBS buffer (pH 7.4,10 mM,1 mM
For QYL-2, 2-(benzo[d]thiazol-2-yl)-5-methoxyphenyl acetate,
it was synthesized through the same approach of QYL-1. Yellow
CTAB 1% MeCN v/v) at 37 ꢀC was performed to check the responses
to different external conditions. Within the range of 7.0e11.0, the
fluorescence signals of both QYL-1 and the detecting system
remained relatively steady (Figs. S1 and SI), indicating a calibrating-
available wide window for application. Although the reaction
reached complete saturation in 2 h, the enhancing rate of fluores-
cent signal was quite slow after 1 h, thus the reaction time was
determined as 60 min (Figs. S2 and SI).
solid (120 mg, 88%). 1H NMR (600 MHz, DMSO‑d6)
d 8.26 (d,
J ¼ 8.8 Hz, 1H), 8.13 (d, J ¼ 7.7 Hz, 1H), 8.06 (d, J ¼ 8.0 Hz, 1H), 7.55
(ddd, J ¼ 8.3, 7.2, 1.3 Hz, 1H), 7.46 (ddd, J ¼ 8.2, 7.2, 1.2 Hz, 1H), 7.08
(dd, J ¼ 8.9, 2.6 Hz, 1H), 7.01 (d, J ¼ 2.6 Hz, 1H), 3.87 (s, 3H), 2.49 (s,
3H). 13C NMR (151 MHz, DMSO‑d6)
d 169.44, 162.44, 152.79, 149.91,
134.75, 131.06, 127.02, 125.74, 123.04, 122.47, 118.68, 113.46, 109.94,
56.36, 22.03. HRMS (ESI-TOF m/z): Calculated for [C16H14NO3S]þ:
300.0694, Found: 300.0681.
Shown in Fig. 4, the fluorescence spectrum of QYL-1 (10
with adding concentrations of hydrazine (0e500 M) suggested a
gradual turn-on change at 480 nm. The plateau was reached at 40.0
equivalent (400 M) and the linear range was 0e20.0 equivalent
(200 M). The limit of detection (LOD) was then determined to be
0.12 M (using formula 3 /k) and the limit of quantity (LOQ) was
tested to be 0.45 M by continuously diluting the concentration of
mM)
m
For QYL-3, 2-(benzo[d]thiazol-2-yl)-4-methoxyphenyl acetate,
it was synthesized through the same approach of QYL-1. White
m
solid (115 mg, 84%). 1H NMR (600 MHz, DMSO‑d6)
d
8.20e8.16 (m,
m
1H), 8.13 (d, J ¼ 8.1 Hz, 1H), 7.82 (d, J ¼ 3.1 Hz, 1H), 7.59 (ddd, J ¼ 8.3,
7.1, 1.3 Hz, 1H), 7.51 (ddd, J ¼ 8.2, 7.2, 1.2 Hz, 1H), 7.32 (d, J ¼ 8.9 Hz,
1H), 7.21 (dd, J ¼ 8.9, 3.1 Hz, 1H), 3.89 (s, 3H), 2.47 (s, 3H). 13C NMR
m
s
m
hydrazine hydrate. One attractive advantage was the ultra-wide
linear range, which was extremely essential for linking the moni-
toring in various scale and field through chemistry, environmental
science, plant physiology and preclinical diagnostics.
(151 MHz, DMSO‑d6) d 169.90, 162.06, 157.50, 152.50, 142.14, 135.33,
127.21, 126.46, 126.22, 125.86, 123.48, 122.64, 118.60, 113.14, 56.19,
21.94. HRMS (ESI-TOF m/z): Calculated for [C16H14NO3S]þ:
300.0694, Found: 300.0692.
3. Results and discussion
3.3. Selectivity of QYL-1
3.1. Synthesis of the sensors
The selectivity towards hydrazine was an important property,
therefore the performance of QYL-1 was evaluated with a variety of
analytes (Fig. 5a). Except for treating with hydrazine, no obvious
enhancement in fluorescence intensity could be observed in the
other groups. Furthermore, when the competitive experiment was
conducted, the response of QYL-1 towards hydrazine was not
interfered by the coexistence of other analytes (Fig. 5b). This probe
did not show any color changes with the addition of different
metals. Thus, in both independent and coexistence systems, the
selectivity of QYL-1 for hydrazine was guaranteed, which also help
built the feasibility of linking multi-field monitoring, especially in
the now-missing plant part.
All the sensors were synthesized as shown in Fig. 2 and
confirmed by satisfactory spectroscopic data (1H NMR, 13C NMR, MS
or HRMS, Figs. S5e22, SI).
3.2. Quick screening of general fluorescent properties for sensing
hydrazine
We recruited and designed a series of sensors QYL-1~3 for hy-
drazine. After evaluating the absorption (Fig. 3aec) and fluores-
cence spectra (Fig. 3def) of the sensors as well as the detecting
Fig. 2. General synthesis route of the QYL series sensors.
Please cite this article as: Y.-L. Qi et al., A turn-on fluorescent sensor for selective detection of hydrazine and its application in Arabidopsis