Reaction-based probe for hydrogen sulfite: dual-channel and good ratiometric response

Article abstract of DOI:10.1002/bio.3117

We designed and synthesized a new series of intramolecular charge transfer (ICT) molecules (compounds T1, T2 and T3) by attaching various electron-donating thiophene groups to the triphenylamine backbone with aldehyde group as the electron acceptor. Based on the nucleophilic addition reaction between hydrogen sulfite and aldehyde, all compounds could act as ratiometric optical probe for hydrogen sulfite and displayed efficient chromogenic and fluorogenic signaling. Upon the addition of hydrogen sulfite anions, probe T3 displayed apparent fluorescent color changes from yellowish-green to blue, with a large emission wavelength shift (Δλ = 120?nm). T3 responded to hydrogen sulfite with high sensitivity and the detection limit was determined to be as low as 0.9?μM. At the same time, apparent changes in UV–vis spectra could also be observed. By virtue of the special nucleophilic addition reaction with aldehyde, T3 displayed high selectivity over other anions. Copyright

Full text of DOI:10.1002/bio.3117

Research article
Received: 28 September 2015,
Revised: 21 January 2016,
Accepted: 25 January 2016
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/bio.3117
Reaction-based probe for hydrogen sulfite:
dual-channel and good ratiometric response
Xiaohong Cheng,a* Ping He,b Zhicheng Zhonga and Guijie Lianga
ABSTRACT: We designed and synthesized a new series of intramolecular charge transfer (ICT) molecules (compounds T1, T2 and
T3) by attaching various electron-donating thiophene groups to the triphenylamine backbone with aldehyde group as the
electron acceptor. Based on the nucleophilic addition reaction between hydrogen sulfite and aldehyde, all compounds could
act as ratiometric optical probe for hydrogen sulfite and displayed efficient chromogenic and fluorogenic signaling. Upon the
addition of hydrogen sulfite anions, probe T3 displayed apparent fluorescent color changes from yellowish-green to blue, with
a large emission wavelength shift (Δλ = 120 nm). T3 responded to hydrogen sulfite with high sensitivity and the detection limit
was determined to be as low as 0.9 μM. At the same time, apparent changes in UV–vis spectra could also be observed. By virtue of
the special nucleophilic addition reaction with aldehyde, T3 displayed high selectivity over other anions. Copyright © 2016 John
Wiley & Sons, Ltd.
Additional supporting information may be found in the online version of this article at the publisher’s web site.
Keywords: reaction-based probe; fluorescence; colorimetric; hydrogen sulfite; intramolecular charge transfer
chemistry, aldehyde is known to react with hydrogen sulfite to
Introduction
form an aldehyde–hydrogen sulfite adduct (35). Considering that
In recent decades, efficient detection for anions has attracted
the conversion of the aldehyde into the hydrogen sulfite adduct
considerable attention because of their importance in a large
number of biological processes (1–6). Among these anions,
hydrogen sulfite has been widely used as a preservative for foods,
would bring about a change in the electron acceptor strength
and the concomitant intramolecular charge transfer (ICT) effi-
ciency, it is feasible to design chemosensors based on this
beverages and pharmaceutical products (fish, potatoes, wine, etc.).
process, for the detection of hydrogen sulfite anion (Scheme 1).
However, bisulfite has been associated with allergic reactions and
food intolerance symptoms such as difficulty in breathing, wheez-
ing, hives, and gastrointestinal distress (7–9). The acceptable daily
intake (ADI) of sulphite (expressed as SO2) is 0.7 mg/kg set by the
Meanwhile, thiophenes are ideal building blocks to provide the
basis for the synthesis of conjugated π-systems (36). With these
considerations in mind, here, we speculated whether dual-channel
and good ratiometric response probes for hydrogen sulfite could
European Parliament and Council Directives (10). Therefore, the
be designed by the modification of ICT efficiency of the
development of a sensitive and selective method for the determi-
thiophene-containing molecules in and without the presence of
nation of hydrogen sulfite is of great importance for food safety
hydrogen sulfite.
and quality control, clinical and environmental applications.
To this end, a new series of ICT molecules (compounds T1, T2
In the field of chemosensors, fluorescent sensors possess innate
and T3, Scheme 2) was synthesized by attaching various
advantages because of their high sensitivity, specificity, simplicity
electron-donating thiophene groups to a triphenylamine (TPA)
of implementation, and fast response times, offering application
methods not only for in vitro assays but also for in vivo imaging
backbone with the aldehyde group as the fixed electron acceptor.
The electron-rich TPA-thiophene moiety was selected to act as
studies (11,12). Meanwhile, colorimetric sensors are especially
both a fluorescent dye and electron donor in the ICT process,
promising because the color change can easily be observed by
which was the key to the success of this strategy (37). The alde-
the naked eye, thus requiring less labor and no equipment
hyde group was chosen to function as an electron acceptor in
(13–18). Therefore, it is reasonable that the dual-channel
chemosensors, which have both fluorescent and colorimetric
responses toward the analytes, can integrate the above two
* Correspondence to: Xiaohong Cheng, Hubei Key Laboratory of Low Dimen-
advantages. In addition, a ratiometric optical method can enable
the measurement of absorption/emission intensities at two differ-
ent wavelengths, providing a built-in correction for environmental
effects and also increasing the dynamic range of measurement
(19–24). However, the dual-channel probes for both fluorogenic
and chromogenic detection of hydrogen sulfite are still very scarce
so far, especially the ratiometric ones (25–29).
As an emerging approach, the reaction-based probes, which
involve the use of special chemical reactions induced by target
analytes, provide us with versatile means for investigating a wide
range of analytes with superior selectivity (30–34). In basic organic
sional Optoelectronic Materials and Devices, Hubei University of Arts and
Science, Xiangyang 441053, Hubei Province, People’s Republic of China.
E-mail: chengxiaohong0807@126.com
a
Hubei Key Laboratory of Low Dimensional Optoelectronic Materials and
Devices, Hubei University of Arts and Science, Xiangyang 441053 Hubei
Province, People’s Republic of China
b
College of Chemical Engineering and Food Science, Hubei University of Arts
and Science, Xiangyang 441053 Hubei ProvincePeople’s Republic of China
Abbreviations: ADI, acceptable daily intake; ICT, intramolecular charge
transfer
Luminescence 2016
Copyright © 2016 John Wiley & Sons, Ltd.

X. Cheng et al.
All other reagents were used as purchased. Compounds 1–4 were
synthesized according to the literature procedures (38).
The 1H and 13C NMR spectra were measured on Varian
Mercury300 and Bruker Avance III400 spectrometer. The ESI (???)
mass spectra were measured on a Finnigan LCQ advantage mass
spectrometer (RT: 4.97–5.38; AV: 26; NL: 8.42E6). The pH values
were determined using
a DELTA 320 PH dollar meter.
Photoluminescence spectra were performed on a Hitachi F-4500
fluorescence spectrophotometer. UV–vis spectra were obtained
using a Shimadzu UV-2550 spectrometer. Fourier transform infra-
red (FTIR) spectra were recorded on a PerkinElmer-2 spectrometer
in the region of 3000–400 cmꢀ1 on NaCl pellets.
Scheme 1. The process of nucleophilic addition reaction between aldehyde and
NaHSO3 and the resulting changed ICT efficiencies and optical properties.
the ICT process on the one hand, and to act as a putative hydrogen
sulfite-dependent reactive subunit on the other hand. Based on
the triphenylamine backbone, the thiophene and ethylene-
dioxythiophene moieties were introduced to enhance the
efficiency of the donor to benefit the delocalization of the whole
chromophore, respectively, in compounds T1 and T3. Then, we
linked bithiophene moieties to the backbone to extend the length
of the π conjugation to prepare compound T2. As demonstrated in
Scheme 2, the aldehyde T3 emitted yellowish-green fluorescence
with the quantum yield of ~0.30. After the reaction with hydrogen
sulfite anions, the resulting aldehyde–hydrogen sulfite adduct
displayed strong blue fluorescence with the increasing quantum
yield of about 0.51. Correspondingly, the color of its solution
changed from yellow to colorless. This indicated that after the
addition reaction of aldehyde, the electronic property of the
resultant hydrogen sulfite adduct changed, leading to the different
fluorescent behavior due to the different ICT efficiency. Herein, we
would like to describe the synthesis and the spectroscopic evalua-
tion of the dual-channel chemosensors in detail.
General procedure for synthesis of compounds T1, T2 and T3
Compound 5, or 6, or 7 (1 equiv.) was dissolved in ClCH2CH2Cl,
then POCl3 (2.7 equiv.) in DMF was added dropwise to the mixture
at 0°C. After the temperature rose to room temperature, the reac-
tion was heated to 45°C. After cooling, the mixture was poured in
an ice bath with stirring and later neutralized with sodium carbon-
ate. The mixture was then filtered, and the crude product was pu-
rified by column chromatography on silica gel to produce the
resulting powder.
Synthesis of compound T1. Compound 5 (0.51 g, 1.0 mmol), DMF
(0.5 mL, 6.5 mmol), POCl3 (0.25 mL, 2.7 mmol), ClCH2CH2Cl (25 mL).
Using petroleum ether/CHCl3 (1:1, v/v) as eluent to obtain T1 as an
orange powder (0.30 g, 56%). 1H NMR (400 MHz, CDCl3, ppm): 9.84
(s, 1H, ꢀCHO), 7.65 (s, 1H, Ar-H), 7.35–7.38 (m, 6H, Ar-H), 7.09–7.12
(m, 3H, Ar-H), 7.00–7.03 (d, 2H, ꢀCH = CH–), 6.95–6.98 (m, 4H, Ar-
H). 13C NMR (CDCl3) δ: 182.5, 152. 7, 146.0, 141.3, 137.2, 130.8,
123.6, 119.5, 116.2. MS (???) (ESI), m/z [M + H]+: 540.2, calcd, 539.9.
Synthesis of compound T2. Compound 6 (0.59 g, 1.0 mmol), DMF
(1 mL, 13.0 mmol), POCl3 (0.37 mL, 4.04 mmol), ClCH2CH2Cl
(50 mL). Using petroleum ether/CHCl3 (1:2, v/v) as eluent to obtain
Experimental
1
T2 as a yellow powder (0.36 g, 58%). H NMR (300 MHz, CDCl3,
Materials and instrumentations
ppm): 9.84 (s, 1H, ꢀCHO), 7.70–7.72 (d, 2H, J = 6.0 Hz, Ar-H),
7.61–7.64 (d, 2H, J = 9.0 Hz, Ar-H), 7.52–7.54 (m, 4H, Ar-H), 7.04–
7.07 (d, 2H, J = 9.0 Hz, ꢀCH = CH–), 6.88–6.90 (d, 4H, J = 6.0 Hz,
Ar-H), 6.79–6.82 (d, 4H, J = 9.0 Hz, Ar-H). 13C NMR (CDCl3) δ:
182.7, 146.3, 137.7, 132.7, 129.3, 127.8, 127.3, 126.1, 124.0, 120.2,
116.3. MS (ESI), m/z [M + H]+: 621.8, calcd, 621.9.
Double-distilled water was used in all experiments. Inorganic salts
including NaHSO3, NaOAc·3H2O, NaNO2, NaNO3, NaF, Na2CO3,
Na2SO4, Na3PO4, NaCl, NaIO3, KClO3, KBr, KSCN, KI, NaHSO4,
Na2S·9H2O and Na2S2O3·5H2O were purchased from Shanghai
Chemical Reagent Co. (Shanghai, China). All solvents and other
reagents were of analytical grade and purchased from the
Sigma-Aldrich Chemical Company. N,N-Dimethylformamide
(DMF) was dried over and distilled from CaH2 under an atmo-
sphere of dry nitrogen. Tetrahydrofuran (THF) was dried over and
distilled from a K–Na alloy under an atmosphere of dry nitrogen.
Synthesis of compound T3. Compound 7 (1.14 g, 2.0 mmol), DMF
(1 mL, 13.0 mmol), POCl3 (0.5 mL, 5.35 mmol), ClCH2CH2Cl (50 mL).
Using petroleum ether/CHCl3 (1:1, v/v) as eluent to obtain 1 as an
1
orange powder (1.00 g, 83.7%). H NMR (300 MHz, CDCl3, ppm):
Scheme 2. Structures of compounds T1, T2 and T3 and the sensing process of T3 toward HSOꢀ3 .
wileyonlinelibrary.com/journal/luminescence
Copyright © 2016 John Wiley & Sons, Ltd.
Luminescence 2016

Ratiometric optical probe for hydrogen sulfite
ꢀ
ꢁꢀ
ꢁ
9.87 (s, 1H, ꢀCHO), 7.56–7.58 (d, 2H, J = 6.0 Hz, Ar-H), 7.47–7.50 (m,
4H, Ar-H), 7.18 (s, 2H, ꢀCH = CH–), 7.03–7.06 (m, 6H, Ar-H),
4.45–4.50 (m, 4H, ꢀCH2–CH2–). 13C NMR (CDCl3) δ: 179.5, 148.9,
147.3, 146.2, 138.7, 132.7, 131.4, 131.0, 128.6, 128.2, 126.2, 123.7,
116.5, 116.3, 115.5, 65.6, 64.8. MS (ESI), m/z [M + H]+: 597.9, calcd,
598.0.
Astandard
Asample
Fsample
Fstandard
ΦFðsampleÞ
¼
ΦFðstandardÞ
ΦF was the fluorescence quantum yield, A was the absorbance,
F was the area under the corrected emission curve. Here, fluores-
cein was used as the standard; the quantum yield of fluorescein
in 0.1 M NaOH was 0.90 (39).
Preparation of solutions of anions
One millimole of each inorganic salt (NaHSO3, NaOAc·3H2O,
NaNO2, NaNO3, NaF, Na2CO3, Na2SO4, Na3PO4, NaCl, NaIO3, KClO3,
KBr, KSCN, KI, NaHSO4, Na2S·9H2O and Na2S2O3·5H2O) was
dissolved in distilled water (10 mL) to afford 1 × 10ꢀ1 mol/L
aqueous solution. The stock solutions were diluted to desired
concentrations with water when needed.
UV–vis absorption changes of T3 by HSO3ꢀ
A solution of T3 (20 μM) was prepared in THF–H2O solution (8:2, v/
v, 200 mM NaH2PO4 citric buffer, pH 5.0). Then 3.0 mL of the
solution of T3 was placed in a quartz cell (10.0 mm width) and
the absorption spectrum was recorded. The NaHSO3 aqueous
solution was introduced in portions (the effect on the total volume
of solution induced by the addition of hydrogen sulfite was
negligible) and the absorption spectra were recorded at room
temperature each time (slit width: 2.0 nm).
Fluorescence titration of T3 with HSO3ꢀ
A solution of T3 (10 μM) was prepared in THF–H2O solution (8:2, v/
v). A 200 mM NaH2PO4 citric buffer solution (pH 5.0) was
employed. Then 3.0 mL of the solution of T3 was placed in a quartz
cell (10.0 mm width) and the fluorescence spectrum was recorded.
The NaHSO3 solution was introduced in portions (the effect on the
total volume of solution induced by the addition of hydrogen sul-
fite was negligible) and fluorescence intensity changes were
recorded at room temperature each time (excitation wavelength:
400 nm; excitation slit: 5.0 nm; emission slit: 2.5 nm; fluorescence
emission spectra were uncorrected).
Results and discussion
Synthesis and structural characterization
The general synthetic procedure is presented in Scheme 3. The
Wittig reaction of the obtained diethyl ((4-(diphenylamino)benzyl)
triphenyl)-phosphonate (1) with 2-formyl-thiophene and deriva-
tives (2–4) gave the corresponding triphenylamine-vinyl thio-
phene (5–7). The followed Vilsmeier reaction of 5, 6 or 7 yielded
the corresponding aldehyde T1, T2 or T3. All compounds exhibited
good solubility in common organic solvents, such as CHCl3,
acetone, DMF, DMSO, CH3CN, and THF. Their structures were well
characterized by 1H, 13C NMR, and ESI-MS, and all gave satisfactory
spectral data (see Supplementary Material Figs S1–S9).
The UV–vis absorption and fluorescent emission spectra for the
ICT molecules are shown in Fig. S10 and summarized in Table 1.
Both the different absorption and emission behaviors between
the aldehydes and the precursors demonstrated the changes of
the electronic properties, leading to different ICT efficiency.
Fluorescence intensity changes of T3 with other anions
A solution of T3 (10 μM) was prepared in THF–H2O solution (8:2, v/
v, 200 mM NaH2PO4 citric buffer, pH 5.0). Then 3.0 mL of the
solution of T3 was placed in a quartz cell (10.0 mm width) and
the fluorescence spectrum was recorded. Different anion solutions
were introduced and the changes of the fluorescence intensity
were recorded at room temperature each time (excitation
wavelength: 400 nm; excitation slit: 5.0 nm; emission slit: 2.5 nm;
fluorescence emission spectra were uncorrected).
Quantum yield changes of T3 with HSO3ꢀ
Optimization of experimental conditions
Quantum yield was determined according to the equation as
follows:
As shown in Fig. 1, all compounds displayed two well separated
emission peaks before and after the addition of hydrogen sulfite,
Scheme 3. General procedures for the synthesis of T1, T2 and T3.
Luminescence 2016
Copyright © 2016 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/luminescence

X. Cheng et al.
Table 1. Optical data of sensor molecules
λ
abs (nm)
λ
em (nm)
λabs (nm)
λ
em (nm)
λ
abs (nm)
λem (nm)
5
T1
310
353
448
535
6
T2
310
354
497
570
7
T3
383
420
440
560
100
80
60
40
20
0
400
450
500
550
600
650
700450 500 550 600 650 700 750400 450 500 550 600 650 700 750
Wavelength (nm)
Figure 1. The fluorescent spectra of probe and probe + HSOꢀ3 .
thus potentially all of them could act as the ratiometric fluorescent
probe for HSOꢀ3 . However, with the addition of excess hydrogen
sulfite, compound T3 exhibited the largest emission wavelength
shift (from 560 to 440 nm, Δλ = 120 nm) and largest enhance-
ment in the ratiometric value (995-fold) compared with that of
the counterpart T1 (from 535 to 450 nm, Δλ = 85 nm, 500-fold)
and T2 (from 570 to 495 nm, Δλ = 75 nm, 415-fold). As men-
tioned above, the ultimate goal of this research was to develop
a reactive probe for hydrogen sulfite with a good ratiometric
optical response. Therefore, we chose compound T3 as the
representative of the ICT-type molecules in the following titration
experiment.
Sensing properties
The sensing behavior of T3 toward hydrogen sulfite was investi-
gated carefully under the optimized conditions. As shown in Fig. 2,
increasing the concentration of hydrogen sulfite, the maximum
emission wavelength shifted from 560 to 440 nm with a well
defined isoemissive point at 515 nm. Actually, even at the concen-
tration of hydrogen sulfite as low as 3 μM, apparent spectra
changes could be observed with respect to the blank solution. It
was noteworthy that the difference in the two emission wave-
lengths was very large (emission shift: Δλ = 120 nm), which not
only contributed to the accurate measurement of the intensities
of the two emission peaks, but also resulted in a huge ratiometric
value. Actually, in the presence of 90 μM of hydrogen sulfite, a c.
1000-fold enhancement in the ratiometric value of I440/I560 (from
0.04 to 39.83) was achieved with respect to the hydrogen sulfite-
free solution.
First, the effect of pH values on the reaction was investigated,
with the results summarized in Fig. S11. The pH value of 5.0
(200 mM Na2HPO4–citric acid buffer) was chosen, in order to
ensure the analyte anion as the chemically reactive hydrogen
sulfite but not sulfite or sulfur dioxide. In the titration experiment,
the mixture system with THF/H2O = 8:2 was chosen as the reaction
media. As shown in Fig. S12, after the addition of excess hydrogen
sulfite, the largest ratiometric value of I440/I560 could be achieved
with 80% of THF, which was beneficial to the design of a
ratiometric fluorescence probe. The possible reason was that there
were solubility differences between the probe and the addition
product and different existing forms of them would affect the fluo-
rescent measurement. Meanwhile, considering that the optical sig-
nal changes relied on the chemical reaction between compound
T3 and HSOꢀ3 , and then the reaction rate might affect the experi-
mental results, we investigated the influence of the reaction time
on the probing results, and the obtained results were demon-
To see the sensing process more visually, we compared the
intensities at the two different wavelengths with the results
strated in Fig. S13. At lower concentrations of HSOꢀ3 (1 × 10ꢀ5
,
2 × 10ꢀ5 and 3 × 10ꢀ5 M), there were gradual changes in the emis-
sion intensity from 0 to 8 minutes; however, after 8 min, the
changes became smaller than before. With the increasing of the
concentrations of HSOꢀ3 , such as 5 × 10ꢀ5, 7 × 10ꢀ5 and
9 × 10ꢀ5 M, a plateau of intensity could be achieved after 10 min
and the changes became slight from 10–14 min. Thus, in the titra-
tion experiment, we measured the optical intensity changes of the
T3 solutions 10 min later after all the species were added.
Figure 2. Fluorescent emission spectra of T3 (10 μM, in THF/H2O = 8/2, pH 5.0) in the
presence of different concentrations of HSOꢀ3 excited at 400 nm.
wileyonlinelibrary.com/journal/luminescence
Copyright © 2016 John Wiley & Sons, Ltd.
Luminescence 2016

Ratiometric optical probe for hydrogen sulfite
Figure 4. UV–vis absorption spectra of T3 (20 μM, in THF/H2O = 8/2, pH 5.0) in the
presence of different concentrations of HSOꢀ3 . Inset: photograph of the solution of
T3 (a); and T3 + HSOꢀ3 (b).
Figure 3. Ratiometric calibration curve I440/I560 of T3 (10 μM, in THF/H2O = 8/2,
pH 5.0) as a function of the concentration of HSOꢀ3 (λex = 400 nm). The error bars rep-
resent the standard deviation of three measurements. Inset: the intensity at 440 nm
changes of T3 as a function of the concentration of HSOꢀ3 .
the equilibrium of the reaction in Scheme 1 moved toward the left.
The above experiment results proved that the proposed recogni-
tion reaction was reversible.
summarized in Fig. 3. The error bars for three repeated measure-
ments showing the good reproducibility of this sensing method.
Furthermore, the detection limit (40) for the analysis of hydrogen
sulfite was estimated from the plot of fluorescence intensity
changes at 440 nm versus concentration of added HSOꢀ3 and
was found to be as low as 0.9 × 10ꢀ6 M as demonstrated in the in-
set of Fig. 3. Taking advantage of the same approach, Yang et al.
prepared a rhodamine-based fluorescent probe toward hydrogen
sulfite and the detection limit was reported as 0.89 × 10ꢀ6 M (26).
In addition, Guo et al. designed a series of coumarin-based fluores-
cent probes for selective detection of hydrogen sulfite anions with
the detection limit as 0.37 × 10ꢀ6 M (27). Recently, Guo et al. re-
ported a 1,8-naphthalimide fluorophore based probe for HSO3ꢀ
and the detection limit was determined to be 0.1 × 10ꢀ6 M (28).
Compared with these reported works, it was clear that the perfor-
mance of T3 was among the best results of the hydrogen sulfite
chemosensors with the same sensing approach.
To evaluate the specific nature of T3 toward hydrogen sulfite,
the influence of other anions were investigated. As shown in Fig. 5,
for all other anions including AcOꢀ, NOꢀ2 , NOꢀ3 , Fꢀ, CO23ꢀ, SO24ꢀ
,
PO34ꢀ, Clꢀ, IOꢀ3 , ClO3ꢀ, Brꢀ, SCNꢀ, Iꢀ, HSO4ꢀ, S2ꢀ and S2O23ꢀ, there
were nearly no changes in the fluorescence spectra observed
and the different sensing behavior could be easily seen by the na-
ked eye under a normal ultraviolet (UV) lamp (as displayed in the
inset fluorescence photograph in Fig. 5). Moreover, we measured
the response of T3 to hydrogen sulfite in the presence of other
competitive anions. As shown in Fig. 6, the presence of other
background anions did not show any obvious disturbance with
the signal response induced by hydrogen sulfite. As reported,
aldehyde could also serve as a reactive subunit toward other
biological nucleophiles such as cysteine, homocysteine and
glutathione (41–43). However, the nucleophilic addition reaction
promoted by biological nucleophiles needed much longer time
In addition to the changed fluorescent behavior caused by the
tuned ICT efficiency of T3 in the presence of hydrogen sulfite,
the color change was another apparent property. As shown in
Fig. 4, with the increasing concentrations of hydrogen sulfite, the
maximum absorption wavelength gradually shifted from 420 nm
to 385 nm, which was responsible for the color change (from yel-
low to colorless) and perceptible to the naked eye (inset in Fig. 4).
Thus, these results indicated that after the addition reaction of al-
dehyde, the electronic property of the resultant hydrogen sulfite
adduct changed, resulting in the different optical behavior due
to the different ICT efficiency.
As is well known, the addition reaction of aldehyde with hydro-
gen sulfite is chemically reversible. The typical approaches for
regenerating the aldehydes from the addition bisulfite adducts
found in the literature involved treating the bisulfite adducts with
either acid or base. Herein, we investigated the effect of pH on the
emission intensity at 440 nm as shown in Fig. S14. Upon adjusting
the pH to 9.0, 10.0 and further to 11.0, the solution of T3 displayed
apparent fluorescent color changes from blue to yellowish-green
and the color changes from colorless to yellow, indicating that
Figure 5. Ratiometric emission of T3 (10 μM, in THF/H2O = 8/2, pH 5.0, λex = 400 nm)
in the presence of different anions (HSO3ꢀ, 90 μM; others, 200 μM). Inset: fluorescent
photograph of T3 to various anions. (a) T3; (b–r) T3 + AcOꢀ, NO2ꢀ, NO3ꢀ, Fꢀ, CO23ꢀ
,
SO24ꢀ, PO34ꢀ, Clꢀ, IO3ꢀ, ClO3ꢀ, Brꢀ, SCNꢀ, Iꢀ, HSO4ꢀ, S2ꢀ, S2O23ꢀ, HSO3ꢀ.
Luminescence 2016
Copyright © 2016 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/luminescence

X. Cheng et al.
addition of excess hydrogen sulfite, a relatively weak peak at about
677.0 appeared coinciding exactly with that for the adduct species
[T3 + HSOꢀ3 -H]ꢀ (m/zcaled = 676.9). Meanwhile, the infra-red (IR)
spectra of T3 before and after the addition of hydrogen sulfite an-
ions could give some information on this transformation. As shown
in Fig. 8, a typical absorption peak at about 1655 cmꢀ1 appeared in
the IR spectrum of T3 in good accordance with aldehyde groups.
But after the addition of HSOꢀ3 ions, no absorption peak centered
at about 1655 cmꢀ1 was observed in the IR spectrum as the result
of the addition reaction between T3 and HSOꢀ3 anions. Further-
more, compound T1 was treated with 20 equiv. NaHSO3, and the
reaction product was characterized by 1H NMR spectrometry. The
partial 1H NMR spectra of T1 and the hydrogen sulfite adduct were
shown in Fig. S15. The resonance signal corresponding to the alde-
hyde proton (Ha) at 9.84 ppm shifted to 4.65 ppm (Hb), conforming
the formation of aldehyde–hydrogen sulfite adduct. The above
experimental data indicated that the sensing process most likely
followed the proposed mechanism as shown in Scheme 1.
Figure 6. Ratiometric emission of T3 (10 μM, in THF/H2O = 8/2, pH 5.0, λex = 400 nm)
to HSOꢀ3 (90 μM) in the presence of other competitive ions (200 μM).
to complete due to their steric hindrance effect. The above results
indicated that our probe had selective response toward hydrogen
sulfite over other anions. It was noteworthy that under the opti-
mized sensing conditions (pH = 5.0), these competitive ions might
not be in the forms listed above, for instance, a portion of the ac-
etate species would be in the neutral form (acetic acid) at pH 5.0.
Here, to simplify the presentation, the anions were described in
their added forms as in the other reported works.
To explore the sensing mechanism of T3 to hydrogen sulfite, the
reaction mixture of T3 with NaHSO3 was characterized by ESI-MS
firstly. As shown in Fig. 7, the ESI-MS spectrum of T3 revealed a
main peak at 597.9 nm before the addition of hydrogen sulfite, cor-
responding to the species [T3 + H]+ (m/zcaled = 598.0). After the
Figure 8. IR spectra of T3 and the product of the reaction between T3 and HSOꢀ3 .
Figure 7. ESI-MS spectra of T3 (left) and the product of the reaction between T3 and HSOꢀ3 (right).
wileyonlinelibrary.com/journal/luminescence
Copyright © 2016 John Wiley & Sons, Ltd.
Luminescence 2016

Ratiometric optical probe for hydrogen sulfite
19. Srikun D, Miller EW, Domaille DW, Chang CJ. Application of flow
injection analysis for determination sulphites in food and beverages:
a review. J Am Chem Soc 2008;130:4596–7.
Conclusion
In conclusion, dual-channel probes toward hydrogen sulfite were
constructed based on the special nucleophilicity of hydrogen
sulfite and the TPA-thiophene chromophore. Upon the addition
of hydrogen sulfite anions, probe T3 displayed apparent fluores-
cent color changes from yellowish-green to blue, with a large
emission wavelength shift (emission shift: Δλ = 120 nm). T3 gave
response to hydrogen sulfite with high sensitivity, and the
detection limit was determined to be as low as 0.9 μM. At the same
time, apparent changes on the UV–vis spectra could also be
observed. By virtue of the special nucleophilic addition reaction
with aldehyde, T3 displayed high selectivity over other anions.
Further study on the design of dual-channel probes for toxic
anions with better performance is still in progress in our laboratory.
20. Komatsu K, Urano Y, Kojima H, Nagano T. Development of an
iminocoumarin-based zinc sensor suitable for ratiometric fluorescence
imaging of neuronal zinc. J Am Chem Soc 2007;129:13447–54.
21. Tremblay MS, Halim M, Sames D. Cocktails of Tb3+ and Eu3+ complexes:
a general platform for the design of ratiometric optical probes. J Am
Chem Soc 2007;129:7570–7.
22. Deo S, Godwin HA. Ratiometric fluorescent sensor for Pb2+. J Am Chem
Soc 2000;122:174–5.
23. Mello JV, Finney NS. Dual-signaling fluorescent chemosensors based
on conformational restriction and induced charge transfer. Angew
Chem Int Ed 2001;40:1536–8.
24. Tsien RY, Harootunian AT. Practical design criteria for a dynamic ratio
imaging system. Cell Calcium 1990;11:93–109.
25. Mohr GJ. A chromoreactant for the selective detection of HSOꢀ3 based
on the reversible bisulfite addition reaction in polymer membranes.
Chem Commun 2002;38:2646–7.
26. Yang X, Zhao M, Wang G. A rhodamine-based fluorescent probe selec-
tive for bisulfite anion in aqueous ethanol media. Sensors Actuators B
Chem 2011;152:8–13.
27. Chen K, Guo Y, Lu Z, Yang B, Shi Z. Novel coumarin-based fluorescent
probe for selective detection of bisulfite anion in water. Chin J Chem
2010;28:55–60.
28. Sun Y, Wang P, Liu J, Zhang J, Guo W. A fluorescent turn-on probe for
bisulfite based on hydrogen bond-inhibited C = N isomerization mech-
anism. Analyst 2012;137:3430–3.
Acknowledgements
This work was financially supported by the National Natural
Science Foundation of China (No. 21502047 and No. 21302047)
and the Science and Technology Research Project of Department
of Education of Hubei Province (B2015147).
29. Wang G, Qi H, Yang X. A ratiometric fluorescent probe for bisulphate anion,
employing intramolecular charge transfer. Luminescence 2013;28:97–101.
30. Jun ME, Roy B, Ahn KH. “Turn-on” fluorescent sensing with “reactive”
probes. Chem Commun 2011;47:7583–601.
References
1. Rostami A, Taylor MS. Polymers for anion recognition and sensing.
Macromol Rapid Commun 2012;33:21–34.
31. Du J, Hu M, Fan J, Peng X. Fluorescent chemodosimeters using “mild”
chemical events for the detection of small anions and cations in biolog-
ical and environmental media. Chem Soc Rev 2012;41:4511–35.
32. Que EL, Domaille DW, Chang CJ. Metals in neurobiology: probing their
chemistry and biology with molecular imaging. Chem Rev
2008;108:1517–49.
2. Martínez-Máñez R, Sancenón F. Chemodosimeters and 3D inorganic
functionalised hosts for the fluoro-chromogenic sensing of anions.
Coord Chem Rev 2006;250:3081–93.
3. Kim SK, Kim HN, Zhu X, Lee HN, Soh JH, Swamy KMK, Yoon J. Recent
development of anion selective fluorescent chemosensors. Supramol
Chem 2007;19:221–7.
33. Kikuchi K Design, synthesis and biological application of chemical
probes for bio-imaging. Chem Soc Rev 2010;39:2048–53.
34. Qian X, Xiao Y, Xu Y, Guo X, Qian J, Zhu W. “Alive” dyes as fluorescent
sensors: fluorophore, mechanism, receptor and images in living cells.
Chem Commun 2010;46:6418–36.
35. Kjell DP, Slattery BJ, Semo MJ. A novel nonaqueous method for
regeneration of aldehydes from bisulfite adducts. J Org Chem
1999;64:5722–4.
36. Mishra A, Ma C-Q, Baüerle P. Functional oligothiophenes: molecular
design for multidimensional nanoarchitectures and their applications.
Chem Rev 2009;109:1141–276.
37. Tsai MS, Hsu YC, Lin JT, Chen HC, Hsu CP. Organic dyes containing
1H-phenanthro [9,10-d]imidazole conjugation for solar cells. J Phys
Chem C 2007;111:18785–93.
4. Kobayashi H, Ogawa M, Alford R, Choyke PL, Urano Y. New strategies
for fluorescent probe design in medical diagnostic imaging. Chem
Rev 2010;110:2620–40.
5. Gale PA, Garcia-Garrido SE, Garric J. Anion receptors based on organic
frameworks: highlights from 2005 and 2006. Chem Soc Rev
2008;37:151–90.
6. Suksai C, Tuntulani T. Chromogenic anion sensors. Chem Soc Rev
2003;32:192–202.
7. McFeeters RF. Use and removal of sulfite by conversion to sulfate in the
preservation of salt-free cucumbers. J Food Protect 1998;61:885–90.
8. Yang X, Guo X, Zhao Y. Novel spectrofluorimetric method for the deter-
mination of sulfite with rhodamine B hydrazide in a micellar medium.
Anal Chim Acta 2002;456:121–8.
9. Fazio T, Warner CR. A review of sulphites in foods: analytical methodol-
ogy and reported findings. Food Addit Contam 1990;7:433–54.
10. Claudia RC, Francisco JC. Application of flow injection analysis for
determination sulphites in food and beverages: a review. Food Chem
2009;112:487–93.
11. Dickerson TJ, Reed NN, LaClair JJ, Janda KD. A precipitator for the
detection of thiophilic metals in aqua. J Am Chem Soc 2004;126:16582–6.
12. Yoon S, Albers AE, Wong AP, Chang CJ. Screening mercury levels in fish
38. Huang F, Chen KS, Yip HL, Hau SK, Acton O, Zhang Y, Luo JD, Jen AK-Y.
Development of new cross-conjugated polymers with donor-π-bridge-
acceptor side chains for high performance solar cells. J Am Chem Soc
2009;131:13886–7.
39. Williams ATR, Winfield SA, Miller JN. Relative fluorescence quantum
yields using
a computer-controlled luminescence spectrometer.
Analyst 1983;108:1067–71.
40. Shortreed M, Kopelman R, Kuhn M, Hoyland B. fluorescent fiber-optic
calcium sensor for physiological measurements. Anal Chem 1996;68:1414–8.
41. Lin W, Long L, Yuan L, Cao Z, Chen B, Tan W. A ratiometric fluorescent
probe for cysteine and homocysteine displaying a large emission shift.
Org Lett 2008;10:5577–80.
42. Lin Y, Lin W, Yang Y. A ratiometric fluorescent probe for specific detec-
tion of cysteine over homocysteine and glutathione based on the dras-
tic distinction in the kinetic profiles. Chem Commun 2011;47:6275–7.
43. Kim TK, Lee DN, Kim HJ. Highly selective fluorescent sensor for homo-
cysteine and cysteine. Tetra Lett 2008;49:4879–81.
with
a selective fluorescent chemosensor. J Am Chem Soc
2005;127:16030–1.
13. Palomares E, Vilar R, Durrant JR. Heterogeneous colorimetric sensor for
mercuric salts. Chem Commun 2004;40:362–3.
14. Sancenón F, Martínez-Máñez R, Soto J. 1,3,5-Triarylpent-2-en-1,5-
diones for the colorimetric sensing of the mercuric cation. Chem
Commun 2001;37:2262–3.
15. Huang J, Wen W, Sun Y, Chou P, Fang J. Two-stage sensing property via
a conjugated donor-acceptor-donor constitution: application to the
visual detection of mercuric ion. J Org Chem 2005;70:5827–32.
16. Tatay S, Gavina P, Coronado E, Palomares E. Optical mercury sensing
using a benzothiazolium hemicyanine dye. Org Lett 2006;8:3857–60.
17. Wiskur SL, AitHaddou H, Lavigne JJV, Anslyn E. Teaching old indicators
new tricks. Acc Chem Res 2001;34:963–72.
Supporting information
Additional supporting information may be found in the online ver-
18. Brümmer O, Clair JJL, Janda KD. A colorimetric ligand for mercuric ion.
Org Lett 1999;1:415–8.
sion of this article at the publisher’s web site.
Luminescence 2016
Copyright © 2016 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/luminescence