Highly fluorescent triazolopyridine-thiophene D-A-D oligomers for efficient pH sensing both in solution and in the solid state

Article abstract of DOI:10.1039/c9cp00672a

Conjugated fluorophores have been extensively used for fluorescence sensing of various substances in the field of life processes and environmental science, due to their noninvasiveness, sensitivity, simplicity and rapidity. Most existing conjugated fluorophores exhibit excellent light-emitting performance in dilute solutions, but their properties substantially decrease or even completely vanish due to severe aggregation quenching in the solid state. Herein, we synthesize a series of triazolopyridine-thiophene donor-acceptor-donor (D-A-D) type conjugated molecules with high absolute fluorescence quantum yields (Φ_F) ranging from 80% to 89% in solution. These molecules also show unusual light-emitting properties in the solid state with Φ_F of up to 26%. We find that owing to the protonation-deprotonation process of the pyridine ring, these compounds display obvious changes in both fluorescence wavelength and intensity upon addition of acids, and these changes can be readily recovered by the successive introduction of bases. By harnessing this phenomenon, we further show that these fluorophores can be employed for efficient and reversible fluorescence sensing of hydrogen ions in a broad pH range (0.0-7.0). With the fabrication of pH testing papers and ink-printed complex patterns including butterflies and letters on substrates, we demonstrate the application of such sensors to fluorescence indication or solid state pH detection for real samples such as volatile acidic/basic gas and water-quality analysis.

Full text of DOI:10.1039/c9cp00672a

View Article Online
View Journal
PCCP
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: N. Jian, K. Qu, H.
Gu, L. Zou, X. Liu, F. Hu, J. Xu, Y. Yu and B. Lu, Phys. Chem. Chem. Phys., 2019, DOI:
1
0.1039/C9CP00672A.
Volume 18 Number
1
7
January 2016 Pages 1–636
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
PCCP
Physical Chemistry Chemical Physics
www.rsc.org/pccp
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1463-9076
PERSPECTIVE
Darya Radziuk and Helmuth Möhwald
Ultrasonically treated liquid interfaces for progress in cleaning and
separation processes
rsc.li/pccp

Please do not adjust margins
Page 1 of 10
Physical Chemistry Chemical Physics
View Article Online
DOI: 10.1039/C9CP00672A
Journal Name
ARTICLE
Highly fluorescent triazolopyridine-thiophene D-A-D oligomers for
efficient pH sensing in both solution and solid state
Received 00th January 20xx,
Accepted 00th January 20xx
a
a
b
b
b
b
*a,b
*c
Nannan Jian , Kai Qu , Hua Gu , Lie Zou , Ximei Liu , Faqi Hu , Jingkun Xu , Yan Yu , Baoyang
*a,b
Lu
DOI: 10.1039/x0xx00000x
Conjugated fluorophores have been extensively used for fluorescent sensing of various substances in the field of life
processes as well as environmental science, due to their noninvasiveness, sensitivity, simplicity and rapidity. Most existing
conjugated fluorophores exhibit excellent light-emitting performances in dilute solutions, but their properties substantially
decrease or even completely vanish due to severe aggregation quenching in solid state. Herein, we synthesize a series of
triazolopyridine-thiophene donor-acceptor-donor (D-A-D) type conjugated molecules with high absolute fluorescence
www.rsc.org/
F
quantum yields (Φ ) ranging from 80% to 89% in solution. These molecules also show unusual light-emitting nature in solid
state with Φ up to 26%. We find that owing to the protonation-deprotonation process of the pyridine ring, these
F
compounds display obvious fluorescence changes in both wavelength and intensity upon addition of acids, and these
changes can be readily recovered by successive introduction of bases. By harnessing this phenomenon, we further show
that these fluorophores can be employed for efficient and reversible fluorescence sensing of hydrogen ions in a broad pH
range (0.0 ~ 7.0). With the fabrication of pH testing papers and ink-printed complex patterns including butterflies and
letters on substrate, we demonstrate the applications of such sensors towards fluorescence indicating or solid state pH
detection for real samples such as volatile acidic/basic gas and water-quality analysis.
sensing,15 nonlinear optics,16 as light emitters for OLEDs, and
17
1
8
Introduction
as light harvesting materials for solar cells.
Although much progress has been made on conjugated
fluorophores in terms of both materials development and
Push-pull conjugated fluorophores and related polymeric
systems, also known as donor-acceptor-donor (D-A-D) type
conjugated systems, are an important class of fluorescence
and light emitting materials that have been extensively studied
1
9,20
pratical
applications,
most
existing
conjugated
and excellent
fluorophores exhibit relatively high absolute Φ
whereas their light-
emitting properties substantially decrease or even completely
F
2
1-23
photostability in dilute solutions,
1
-12
and utilized in various technologies.
Their molecular
structures generally contain electron rich (donor) and electron
deficient (acceptor) moieties linked via a π-conjugated bridge.
Photoexcitation leads to the intramolecular charge-transfer
from the electron rich units in the molecule to the electron
deficient fragments.13 Such a redistribution of electron density
usually leads to extended absorption/emission bands all the
way from the ultraviolet to the near-infrared regions,
depending on the electronic offset between the donor and
vanish in the solid state due to the strong intermolecular π–π
2
4,25
stacking interactions.
Up to date, rational design of novel
conjugated D-A-D fluorophores with high performances in
both solution and solid state is still significant to this field in
terms of various practical application requirements.
The most common yet effective strategy to design new D-A-D
molecules with tunable optical and electronic properties is to
modify the electron donating and/or accepting nature of the D
or A fragments, respectively. Most recently, we and other
new type of acceptor moieties,
and their
analogues/derivatives, which have been successfully employed
towards rational design of narrow band gap D-A-D polymers
1
4
acceptor components and the overall delocalization length.
This type of materials usually exhibit excellent photophysical
properties, sensitivity, simplicity, rapidity and noninvasiveness,
and have been utilized in many organic electronic and optical
applications including use as fluorescent indicating and
groups developed
a
chalcogenodiazolo[3,4-c]pyridine
2
6-31
with high performance in organic electronics.
found that those D-A-D type polymers also display excellent
fluorescence in organic solution and can be utilized for
It was also
a. School of Chemistry & Chemical Engineering, Jiangxi Science & Technology
Normal University, Nanchang 330013, Jiangxi, PR China;
b.
School of Pharmacy, Jiangxi Science & Technology Normal University, Nanchang
fluorescent sensing towards proton and even Lewis
3
30013, Jiangxi, PR China;
c.
26,27,29
School of Optical and Electronic Information, Huazhong University of Science and
Technology, Wuhan 430074, Hubei, PR China.
acids.
However, like most reported D-A-D type molecular
systems, chalcogenodiazolo[3,4-c]pyridine-based conjugated
fluorophores display significantly decreased or even
*Corresponding author. Email: lby1258@163.com; xujingkun1971@yeah.net; and
yuyan19840218@hust.edu.cn
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2017, 00, 1–3 | 1
Please do not adjust margins

Please do not adjust margins
Physical Chemistry Chemical Physics
Page 2 of 10
ARTICLE
Journal Name
completely disappeared light-emitting in solid state compared
to their corresponding diluted solution due to aggregation-
caused fluorescence quenching during the solid state packing.
Experimental
View Article Online
DOI: 10.1039/C9CP00672A
2
.1 Materials
From the materials development perspective, conjugated Building blocks like thiophene (Th, 99.5%, Sigma-Aldrich), 3-
fluorophores based on triazolo[4,5-c]pyridine (PTz), an methylthiophene (3MT, 98%, Sigma-Aldrich), 3-hexylthiophene
important nitrogen analogue of chalcogenodiazolo[3,4- (3HT, 99%, Sigma-Aldrich), 3-octylthiophene (3OT, 97%, Sigma-
c]pyridine which can be facilely modified on the N position Aldrich), and 3,4-ethylenedioxythiophene (EDOT, 97%, J&K)
with different functional groups might reveal excellent were all used as received. Other reagents were purchased
fluorescence and sensing properties in both solution and solid from guaranteed chemical plants and directly used for the
-1
state, due to the feasibility of reducing the strong synthetic procedure, such as n-butyllithium (n-BuLi, 1.6 mol L
intermolecular π–π stacking interactions. Furthermore, the in hexanes, J&K), chlorotributyltin (SnBu Cl, J&K), acetic acid
protonation-deprotonation of pyridine ring allow these (AcOH, 99%, J&K), sodium nitrite (NaNO , ≥ 99.999% trace
3
2
compounds to serve as fluorescence sensing materials for metals basis; 98-102% (RT), Sigma-Aldrich), triethylamine
effective detection of acids like pH. Unfortunately, to the best (99.5%, Energy), 1-bromohexane (99%, Shanghai Vita), 1-
of our knowledge, rational design and structure-property iodododecane (98%, stablized with copper, Shanghai Vita),
relationship of triazolo[4,5-c]pyridine-based D-A-D molecular dichloromethane (DCM, 99.9%, superdry, with molecular
systems have not been well known and explored for sieves, J&K), acetonitrile (ACN, 99.9%, ACS/HPLC certified, J&K).
fluorescent chemosensors.
Tetrahydrofuran (THF), as solvent for stannylization, was
Here, based on the 2H-[1,2,3]triazolo[4,5-c]pyridine (PTz) purified by distillation with sodium under nitrogen atmosphere
moiety, we design and synthesize a series of novel before use. Trans-dichlorobis(triphenyl-phosphine)palladium
triazolopyridine-thiophene
fluorophores (1~10, Scheme 1) with alkyl substitution to as the catalyst for Stille coupling. Tetrabutylammonium
enhance the solubility and solid-state fluorescence. Systematic hexafluorophosphate (TBAPF , 99%, Shanghai Vita), electrolyte
D-A-D
type
conjugated (II) (Pd(PPh
3 2 2
) Cl , 98%, 15% Pd, Sigma-Aldrich) was employed
6
investigation of their structure-property relationship as well as for the electrochemical polymerization, was dried under
photophysical properties demonstrates excellent fluorescence vacuum at 60 °C for 24 h before use.
properties of these D-A-D molecular systems both in the 2.2 Instruments and characterization
diluted solutions and solid state. Moreover, efficient and
reversible pH sensing behavior in both solution and solids are 13
1
A Bruker AV 400 NMR spectrometer was employed for H and
C NMR spectral measurements, with trimethylsilane (TMS) as
observed for these molecules. Enabled by their good solubility,
we further demonstrate the facile fabrication of complex
patterns by ink-jet printing such as butterflies and letters, and
explore their potential applications for the detection of volatile
acidic/basic vapor.
3 6
the internal standard and CDCl or DMSO-d as the solvent. A
X-4 digital display micro melting point instrument was used to
determine the melting points of triazolopyridine-thiophene D-
A-D type conjugated fluorophores. Infrared spectra were
performed with a Bruke Vertex 70 Fourier-transform infrared
(FT-IR) spectrometer. The electronic spectra were recorded on
a
Lambda 750 UV-Vis spectrophotometer. Theoretical
calculations of all triazolopyridine-thiophene D-A-D type
fluorophores were performed by DFT methods with the
Gaussian 09 program package. Becke’s three-parameter
gradient corrected functional (B3LYP) with the 6-31G (d,p)
basis in vacuum was used for all the compounds to optimize
the structure geometry and to compute the electronic
structures at the minimum found. Electrochemical
polymerization was investigated by
a
Versa Stat
3
electrochemical workstation (EG&G Princeton Applied
Research). Pt wires (diameter: 1 mm) were employed as the
working and counter electrodes, and an Ag/AgCl electrode as
the reference electrode, respectively. Moreover, in order to
minimize the oxygen effect, the electrolytic system was
bubbled by nitrogen stream before experiments. In order to
obtain sufficient polymers for further characterization, Pt
2
sheet (2×1.5 cm ) was used as working electrode and another
2
Pt sheet (2×2 cm ) was employed as the counter electrode.
2
.3 Synthesis
Scheme
triazolopyridine-thiophene
Scheme 1 (A) Chemical structures of typical chalcogenodiazolo[3,4-c]pyridine
derivatives-based conjugated D-A-D type molecules reported in literature and
triazolopyridine-thiophene systems synthesized in this work. (B) Detailed
synthetic routes of triazolopyridine-thiophene D-A-D type molecules 1 ~ 10 via
Stille coupling.
1
illustrates the synthetic route of various
D-A-D
and
type
dodecyl
conjugated
substituted
fluorophores.
Hexyl
2
| J. Name., 2017, 00, 1–3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Page 3 of 10
Physical Chemistry Chemical Physics
Journal Name ARTICLE
View Article Online
3
1,2,3]triazolo[4,5-c]pyridine (HPTz and DPTz) were chosen as 3MT-HPTz (2). 94% yield. H NMR (400 MHz, CDCl , ppm): 8.63
1
[
the acceptors, while thiophenes like Th, 3MT, 3HT, 3OT and (s, 1H), 8.30 (s, 1H), 7.84 (s, 1H), 7.12 (s,D1OHI:),106..190839(/sC,91CHP0),0467.826A
EDOT were employed as the donors, and all these molecular (t, J = 7.20 Hz, 2H), 2.37 (d, J = 9.10 Hz, 6H), 2.21 (dd, J = 14.1,
systems were synthesized by Stille coupling. Stannylization of 7.10 Hz, 2H), 1.35 (d, J = 7.60 Hz, 6H), 0.97 (d, J = 6.60 Hz, 3H).
1
3
thiophenes occurred at 2-position with tri-n-butyltin choride,
3
C NMR (400 MHz, CDCl , ppm): 153.16, 144.04, 140.89,
and they were employed for the next step immediately 138.53, 138.11, 137.64, 137.53, 136.09, 131.58, 129.01, 124.22,
3
2-35
without further purification.
Acceptor intermediates such 123.97, 120.89, 117.42, 56.59, 30.48, 29.39, 25.55, 21.80,
-1
as 4,7-dibromo-[1,2,3] triazolo[4,5-c]pyridine, 4,7-dibromo- 16.67, 15.20. FT-IR (ATR, cm ): 3087, 2927, 2553, 1579, 1552,
hexyl[1,2,3]triazolo[4,5-c]pyridine
dodecyl[1,2,3]triazolo[4,5-c]pyridine
according to previously reported procedures.
synthetic procedures are described as following.
and
were
4,7-dibromo- 1489, 1365, 1195, 1151, 1072, 713.
1
synthesized 3HTh-HPTz (3). 84% yield. H NMR (400 MHz, CDCl
3
, ppm):
3
6-40
The primary 8.64 (s, 1H), 8.30 (s, 1H), 7.85 (s, 1H), 7.13 (s, 1H), 7.00 (s, 1H),
4.87 (t, J = 7.00 Hz, 2H), 2.70 (dd, J = 15.8, 8.00 Hz, 4H),
4
,7-Dibromo-[1,2,3]triazolo[4,5-c]pyridine. To a solution of 2.23~2.10 (m, 2H), 1.76~1.67 (m, 4H), 1.38~1.33 (m, 13H),
1
3
2
,5-dibromopyridine-3,4-diamine (0.80 g, 3.00 mmol) in acetic 0.94~0.90 (m, 14H). C NMR (400 MHz, CDCl
(0.30 g, 3.30 mmol) 144.69, 141.54, 139.18, 138.76, 138.29, 129.66, 127.44, 124.87,
in deionized water (6.00 mL) was gradually added at room 121.54, 118.07, 57.24, 32.25, 31.13, 30.04, 28.22, 26.77, 26.20,
3
, ppm): 154.24,
acid (12.00 mL, AcOH), a solution of NaNO
2
-1
temperature. The mixture was stirred for 20 min at the same 24.42, 23.34, 22.45, 13.97. FT-IR (ATR, cm ): 3080, 2934, 2854,
temperature. Then, the precipitate was obtained by filtration 1581, 1549, 1493, 1368, 1221, 1154, 1058, 698.
1
and washed with deionized water. The crude products were 3OT-HPTz (4). 69% yield. H NMR (400 MHz, DMSO-d
6
, ppm):
directly used for the next step without further purification.
,7-Dibromo-hexyl[1,2,3]triazolo[4,5-c]pyridine and 4,7- 4.96 (t, J = 6.90 Hz, 2H), 2.66 (dd, J = 15.7, 8.00 Hz, 4H),
dibromo-dodecyl[1,2,3]triazolo[4,5-c]pyridine. A solution of 2.16~2.08 (m, 2H), 1.64 (s, 4H), 1.37~1.23 (m, 24H), 0.86 (dd, J
8.68 (s, 1H), 8.27 (s, 1H), 7.94 (s, 1H), 7.46 (s, 1H), 7.35 (s, 1H),
4
1
3
4
,7-dibromo-[1,2,3]triazolo[4,5-c]pyridine (0.61 g, 2.20 mmol) = 15.4, 8.10 Hz, 10H). C NMR (400 MHz, CDCl
in N,N-dimethylformamide (DMF, 30.00 mL), triethylamine 144.54, 141.39, 139.03, 138.61, 138.14, 129.51, 127.29, 124.72,
2.50 mmol) was slowly added under nitrogen atmosphere. 121.39, 117.92, 57.09, 33.73, 30.98, 29.89, 28.07, 26.62, 26.05,
3
, ppm): 154.09,
(
-1
After stirring for 1 h, 1-bromohexane (0.41 g, 2.50 mmol)/1- 24.27, 23.19, 22.30, 13.82. FT-IR (ATR, cm ): 3091, 2930, 2849,
iodododecane (0.74 g, 2.50 mmol) were added drop-wise. The 1582, 1547, 1492, 1360, 1204, 1150, 1056, 697.
1
reaction was stirred for 24 h at room temperature. DMF was EDOT-HPTz (5). 91% yield. H NMR (400 MHz, CDCl
3
, ppm):
removed, while organic layer was extracted with DCM and 9.38 (s, 1H), 6.72 (s, 1H), 6.56 (s, 1H), 4.86 (t, J = 7.20 Hz, 2H),
then purified by silica column chromatography.
4
4.57 (s, 2H), 4.45~4.26 (m, 6H), 2.19 (dd, J = 14.4, 7.20 Hz, 2H),
,7-Dibromo-hexyl[1,2,3]triazolo[4,5-c]pyridine. 70% yield. 1H 1.43~1.32 (m, 6H), 0.90 (dd, J = 7.20, 3.80 Hz, 3H). C NMR
13
3 3
NMR (400 MHz, CDCl , ppm): 8.34 (s, 1H), 4.82 (t, J = 7.40 Hz, (400 MHz, CDCl , ppm): 155.34, 152.57, 151.77, 145.42, 144.71,
2
5
H), 2.25~2.10 (m, 2H), 1.45~1.31 (m, 6H), 0.88 (dd, J = 8.60, 114.78, 113.85, 95.42, 94.88, 66.09, 65.07, 64.45, 63.88, 57.27,
-1
.20 Hz, 3H).
31.15, 30.06, 26.79, 26.22, 15.98. FT-IR (ATR, cm ): 3088, 2926,
4
,7-Dibromo-dodecyl[1,2,3]triazolo[4,5-c]pyridine. 73% yield. 2852, 1580, 1548, 1495, 1364, 1197, 1155, 1070, 701.
1
1
H NMR (400 MHz, CDCl
3
, ppm): 8.34 (s, 1H), 4.82 (t, J = 7.40 Th-DPTz (6). 72% yield. H NMR (400 MHz, DMSO-d
6
, ppm):
Hz, 2H), 2.16 (d, J = 7.30 Hz, 2H), 1.39~1.24 (m, 17H), 0.89 (dd, 8.75 (s, 1H), 8.43 (d, J = 3.60 Hz, 1H), 8.09 (d, J = 3.50 Hz, 1H),
J = 15.0, 8.30 Hz, 4H). 7.85 (d, J = 5.00 Hz, 1H), 7.75 (d, J = 5.00 Hz, 1H), 7.36~7.24 (m,
Representative procedures for the synthesis of 1~10. To a 2H), 4.94 (t, J = 6.80 Hz, 2H), 2.19~2.05 (m, 2H), 1.19 (d, J =
1
3
solution of stannylized donors (10.00 mmol) and 4,7-dibromo- 24.0 Hz, 17H), 0.87 (d, J = 7.30 Hz, 4H). C NMR (400 MHz,
hexyl[1,2,3]triazolo[4,5-c]pyridine (0.72 g, 2.00 mmol) or 4,7- CDCl , ppm): 150.91, 149.44, 143.34, 142.36, 130.44, 130.27,
3
dibromo-dodecyl[1,2,3]triazolo[4,5-c]pyridine (0.89 g, 2.00 130.02, 129.68, 129.38, 129.09, 128.94, 128.65, 61.27, 32.20,
mmol) in DMF (30.00 mL), trans-dichlorobis(triphenyl- 31.00, 30.00, 29.36, 28.29, 27.75, 27.08, 26.54, 26.05, 22.77,
-1
3 2 2
phosphine)palladium (II) (Pd(PPh ) Cl , 0.14 g, 0.20 mmol) was 22.58, 17.49. FT-IR (ATR, cm ): 3092, 2820, 2846, 1581, 1550,
added, and then the mixture was stirred for 24 h at 110 °C. 1491, 1369, 1195, 1147, 1067, 705.
1
After the reaction, the mixture was poured into deionized 3MT-DPTz (7). 74% yield. H NMR (400 MHz, CDCl
3
, ppm): 8.63
water and extracted with DCM. The organic layer was purified (s, 1H), 8.33 (s, 1H), 7.84 (s, 1H), 7.14 (s, 1H), 6.99 (s, 1H), 4.87
by silica column chromatography.
Th-HPTz (1). 76% yield. H NMR (400 MHz, DMSO-d
(t, J = 7.20 Hz, 2H), 2.38 (d, J = 9.60 Hz, 6H), 2.25~2.17 (m, 2H),
, ppm): 1.47~1.32 (m, 17H), 0.98~0.94 (m, 4H). C NMR (400 MHz,
1
13
6
8
7
1
.76 (s, 1H), 8.44 (s, 1H), 8.09 (s, 1H), 7.86 (s, 1H), 7.76 (s, 1H), CDCl
.43~7.22 (m, 2H), 4.96 (t, J = 7.00 Hz, 2H), 2.23~2.05 (m, 2H), 138.27, 136.82, 132.32, 129.75, 124.95, 124.70, 121.63, 118.16,
3
, ppm): 154.05, 144.77, 141.63, 139.27, 138.85, 138.38,
1
3
.32 (dd, J = 15.7, 8.60 Hz, 6H), 0.87 (d, J = 6.40 Hz, 3H).
, ppm): 155.82, 144.46, 143.34, 142.46, 15.94, 14.06, 13.67. FT-IR (ATR, cm ): 3088, 2934, 2825, 1580,
41.41, 132.05, 131.64, 130.27, 130.02, 128.32, 127.88, 127.46, 1557, 1493, 1368, 1195, 1153, 1062, 695.
C
57.33, 45.83, 40.50, 40.32, 31.22, 30.13, 26.86, 22.54, 17.41,
-1
NMR (400 MHz, CDCl
1
1
3
1
3
26.98, 59.73, 39.90, 39.79, 22.77, 22.58, 16.91. FT-IR (ATR, 3Hh-DPTz (8). 64% yield. H NMR (400 MHz, CDCl , ppm): 8.64
-1
cm ): 3085, 2831, 2847, 1587, 1550, 1491, 1362, 1201, 1150, (s, 1H), 8.32 (s, 1H), 7.86 (s, 1H), 7.15 (s, 1H), 7.01 (s, 1H), 4.87
1
071, 711.
(t, J = 7.00 Hz, 2H), 2.70 (dd, J = 15.8, 8.00 Hz, 4H), 2.28~2.15
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2017, 00, 1–3 | 3
Please do not adjust margins

Please do not adjust margins
Physical Chemistry Chemical Physics
Page 4 of 10
ARTICLE
Journal Name
(
m, 2H), 1.70 (m, 4H), 1.39~1.22 (m, 29H), 0.92~0.85 (m, 10H). 24 h in dark at room temperature. Fluorescent detection of
View Article Online
1
3
, ppm): 153.82, 144.27, 141.12, volatile acid/base vapor was conductedDuOsI:in10g.10a39c/uClt9uCrPe00d6i7s2hA.
C NMR (400 MHz, CDCl
3
1
5
38.76, 138.34, 137.87, 129.24, 127.02, 124.45, 121.12, 117.65, Patterning of the fluorescent butterfly and letters were
6.82, 32.25, 30.71, 30.03, 29.62, 28.65, 27.80, 27.08, 26.35, fabricated by inkjet-printing of these fluorophores dissolving
5.78, 24.88, 24.00, 22.03, 21.28, 20.13, 15.54. FT-IR (ATR, cm- into DCM on substrates using a Canon MG3620 printer.
2
1
)
: 3087, 2921, 2845, 1584, 1557, 1492, 1367, 1195, 1158,
1
3
8
4
7
059, 691.
1
Results and Discussion
OT-DPTz (9). 56% yield. H NMR (400 MHz, DMSO-d
.68 (s, 1H), 8.27 (s, 1H), 7.95 (s, 1H), 7.46 (s, 1H), 7.35 (s, 1H),
.96 (s, 2H), 2.66 (d, J = 8.20 Hz, 4H), 2.13 (s, 2H), 1.59 (d, J =
.70 Hz, 6H), 1.41~1.13 (m, 35H), 0.90~0.84 (m, 10H). C NMR
, ppm): 154.25, 144.70, 141.55, 139.20, 138.78,
38.31, 129.68, 127.46, 124.89, 121.56, 118.08, 57.26, 33.90,
2.68, 31.15, 30.05, 29.08, 28.23, 26.79, 26.21, 24.43, 22.46,
6
, ppm):
3
.1 Molecular design and synthesis
From the molecular design perspective, the combination of
donors and acceptors can effectively tune the photophysical
properties of molecules. Alkyl substituted donors/acceptors
have been introduced into the π-conjugated systems to
increase solution processability and weaken intermolecular π–
π stacking interactions. A series of novel triazolopyridine-
thiophene D-A-D type conjugated fluorophores (1 ~ 10) are
synthesized via Stille coupling (Scheme 1). All intermediates
and target fluorophores are obtained in relatively high yields
1
3
(400 MHz, CDCl
3
1
3
1
2
-1
7.33, 15.97, 14.98, 13.98, 13.60. FT-IR (ATR, cm ): 3089, 2922,
848, 1585, 1552, 1492, 1362, 1197, 1159, 1057, 701.
1
EDOT-DPTz (10). 85% yield. H NMR (400 MHz, CDCl
3
, ppm):
9
4
1
1
9
2
.55 (s, 1H), 6.87 (s, 1H), 6.61 (s, 1H), 4.89 (t, J = 6.90 Hz, 2H),
.70 (s, 2H), 4.48~4.22 (m, 6H), 2.21 (d, J = 7.70 Hz, 2H), 1.24 (s,
7H), 0.87 (t, J = 6.80 Hz, 4H). C NMR (400 MHz, CDCl , ppm):
3
(typically over 70%). Their molecular structures are all
1
3
determined by NMR spectra (Fig. S1 ~ Fig. S22) and FT-IR
spectra (Fig. S23 and Table S1).
Density functional theory (DFT) calculations were used to
study the conformational and electronic properties of
55.19, 152.42, 151.62, 145.27, 144.56, 114.63, 113.70, 95.27,
4.73, 65.94, 64.92, 64.30, 63.73, 57.12, 31.80, 31.01, 29.91,
8.09, 26.65, 26.07, 25.17, 24.29, 23.22, 22.32, 15.83. FT-IR
-1
(
1
2
ATR, cm ): 3087, 2929, 2850, 1579, 1549, 1490, 1360, 1198,
152, 1069, 703.
.4 Detection of fluorescence sensing
A series of aqueous solutions with different pH from 0.00 to
.00 were prepared with HCl and deionized water, and the pH
triazolopyridine-thiophene
D-A-D
type
conjugated
fluorophores (1 ~ 10). DFT calculations are beneficial for
confirming molecular geometry, predicting optimized
molecular structures and electronic energy levels, and
demonstrating complete delocalization across the molecular
7
vaues were confirmed by using a pH meter. Typically, the stock
standard solutions (40 μL, 15 μM) of fluorophores dissolving in
DMSO were added to different pH solutions (2 mL). After 10
min of equilibration time, the fluorescence spectra were
recorded with an F-4500 fluorescence spectrophotometer with
excitation and emission slit set at 5 nm.
41-44
backbones.
From the theoretical calculations (Table 1 and
Table S2), the optimized geometries of all the triazolopyridine-
based D-A-D type fluorophores shows quasi-planar conjugated
systems with small dihedral twist angles between each block.
The molecular orbital distribution results suggest that the
LUMO is mostly localized on the triazolopyridine acceptor unit,
whrereas the HOMO is well-distributed over the entire
2
.5 The preparation of pH test papers and patterning
The fluorescence pH testing papers were prepared by dipping molecular structure, and the energy levels vary with the
filter paper into a DCM solution of fluorophores (0.1 mg in 1 electron-donating ability of the end-capping moieties. This is in
mL DCM) for 10 s. Then, these test papers were dried in air for good agreement with most reported calculations of D-A-D type
Table 1 Optical parameters and DFT theoretical calculation data of triazolopyridine-thiophene D-A-D type conjugated fluorophores (1~10).
HOMODFT
eV)
LUMODFT
(eV)
Dihedral
angels(°)
Eg,opt
(eV)
λmax,1
(nm)
λmax,2
(nm)
λmax,3
(nm)
λem
(nm)
Φ
F
[%]
Fluorophores
(
solution
solid
25.2
1
2
3
4
5
6
7
8
9
-5.27
-5.19
-5.17
-5.15
-4.83
-5.27
-5.19
-5.15
-5.17
-4.82
-2.09
14.0, 0.10
13.9, 0.37
16.5, 0.56
6.96, 0.53
4.07, 3.76
15.2, 0.49
14.8, 0.08
8.88, -0.42
14.6, -0.43
5.05, 3.94
2.79
2.70
2.74
2.72
2.58
2.83
2.70
2.74
2.72
2.63
242
240
238
239
248
243
238
238
240
246
276
278
281
282
292
277
281
281
281
294
397
407
408
408
417
400
408
409
410
418
498
508
509
509
520
498
510
510
510
521
86.7
87.8
87.8
89.2
82.5
86.9
86.5
88.1
88.6
79.8
-2.03
-2.02
-2.03
-1.78
-2.08
-2.03
-2.02
-2.01
-1.77
15.1
24.7
26.0
14.6
23.2
18.6
22.9
20.2
13.2
1
0
4
| J. Name., 2017, 00, 1–3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Page 5 of 10
Physical Chemistry Chemical Physics
Journal Name ARTICLE
molecule systems.45-47 Note here that triazolopyridine-based dilute solution (Table S3), whereas their VfileuwoArrteicsleceOnnlcinee
D-A-D type fluorophores exhibited slightly higher LUMO than performances severely decrease or evenDOcoI:m10p.1l0e3t9e/lCy9vCaPn0i0s6h72inA
their chalcogenodiazolo[3,4-c]pyridine analogs (Table S3). This the solid state due to aggregation-caused fluorescence
phenomenon is mainly caused by the introduction of long alkyl quenching during the solid state packing. So far, only a few
F
chain spacers on triazolopyridine acceptor, which interrupts materials reveal light-emitting properties with Φ greater than
2
6
the intermolecular arrangement of these systems.
.2 Photophysical properties
20% in both solution and solid state. Interestingly, we find
that these triazolopyridine-based D-A-D type fluorophores in
this work demonstrate very strong light emitting nature with
3
Owing to the introduction of long alkyl chains, these D-A-D
type fluorophores indeed reveal excellent solubility in
common organic solvents, for instance, dimethyl sulfoxide
F
outstanding Φ both in dilute solution (up to 89%) and in the
solid state (up to 26%) (Fig. 1A, Fig. S24, and Table 1). The
emission peaks of these compounds are generally in the range
of 498~521 nm (Fig. 1B, Fig. S24, and Table 1), typically in the
blue (450 ~ 500 nm) to green (500 ~ 570 nm) region. In good
agreement with UV-vis spectral results, the emission spectra
also display slight red shifts owing to the increase of electron-
donating capacity from Th to alkyl thiophenes and further to
EDOT. Overall, triazolopyridine-based D-A type fluorophores
reported herein display better fluorescence properties than
their chalcogenodiazolo[3,4-c]pyridine analogs (Table S3),
(DMSO), acetonitrile (ACN), tetrahydrofunan (THF), DCM, and
chloroform (CDCl ). The superior solubility of these
3
fluorophores can facilitate their practical applications in
various fields. As typical D-A-D type systems, all these
triazolopyridine-thiophene molecules reveal characteristic
dual-band absorptions in the UV-vis spectra (Fig. 1A and Fig.
S24). To be specific, the π-π* transition (both E1 and K
absorption bands) of individual aromatic units like thiophene
ring in these conjugated systems results in two maximum
peaks at short wavelengths (230~300 nm), whereas charge
transfer between different donor units and acceptors as well
as the n-π* transition of the triazolopyridine units (R bands
from C=N and N=N bonds) typically yield red-shifted maximum
6
2
6,27,29,51-55
and even higher than most of the fluorescent
materials.56-58 This is mainly due to the fact that the stronger
electron-deficient nature of triazolopyridine unit decreases the
singlet oxygen generation efficiency and increases the
emission intensity.
absorption peaks extended to longer wavelengths in the range
of 395~420 nm.2
6,27,29,48
3.3. Fluorescence quenching/recovery of pH sensing
Moreover, the extension of side chains
in thiophene-based donor units is found to cause slight red Guaranteed by their superior solubility, these fluorophores can
shifts in the absorption peaks due to the fact that side groups be dissolved into many organic solvents and even water-based
with varying electron-donating ability exert different changes binary solvents such as water-DMSO, water-ACN, etc. These
on the electronic structures of these D-A-D type molecules are expected to possess good sensitivity towards
fluorophores.4 For example, due to the extended alkyl chain hydrogen ions and even electron-deficient atoms in Lewis
9,50
5
9
reducing the LUMO level, the absorption bands of dodecyl acids (like BF3) due to the fact the lone pair electrons at the
modified triazolopyridine-based fluorophores show N position in pyridine ring. Moreover, the pH sensing
bathochromic shift to lower energy region compared to their performances are probably improved owing to the molecular
hexyl analogs. Compared to our previous results of wire magnification effect from extended π-conjugated
chalcogenodiazolo[3,4-c]pyridine-based
analogs,
the molecular backbone. To examine the fluorescence sensing
absorption bands of triazolopyridine-thiophene D-A-D type properties, we choose the binary solvent of water and DMSO
precursors slightly blue-shift to higher energy regions due to as testing system since both water and DMSO are nontoxic and
the stronger electron-deficient nature of triazolopyridine unit. environmentally friendly. As expected, all these fluorophores
Table S3).2
6,27,29,51-55
reveal strong blue to green light-emission in such media, and a
(
Although a series of chalcogenodiazolo[3,4-c]pyridine-based D- gradual fluorescence quenching is observed with stepwise
A-D type conjugated fluorophores have been obtained in the addition of acids like HCl (Fig. 2A and Fig. S25). Meanwhile, the
emitting color of the fluorophores correspondingly changes
from blue or green to kelly, yellow, and further to claybank
due to the protonation of pyridine ring with hydrions.
Interestingly, this fluorescence quenching can be easily
recovered with the addition of bases like sodium hydroxide
solution (NaOH) owing to the deprotonation of nitrogen on the
pyridine ring (Fig. 2A and Fig. S25), indicating a reversible
coordination process between fluorophores and acids. The
light-emitting color changes also imply the reversible pH
detection and this process even can be easily observed by
naked eyes.
Fluorescent spectroscopy is more sensitive to small changes in
Fig. 1 (A) Photoluminescence of triazolopyridine-thiophene D-A-D type
conjugated fluorophores (1~10) in both solution (DCM) and solid state. (B) UV-Vis
absorption and emission spectra of representative triazolopyridine-thiophene D-
A-D type conjugated fluorophores (1, 3, 5 and 10) in DCM.
emission and quantitatively disclose the detailed information
6
0,61
during the quenching and recovery process.
In order to
last several years,26,27,29,51-55 these molecules mostly exhibit
bright light-emitting properties with high Φ (0.072-0.849) in
F
further evaluate the sensing performances of these molecules,
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2017, 00, 1–3 | 5
Please do not adjust margins

Please do not adjust margins
Physical Chemistry Chemical Physics
Page 6 of 10
ARTICLE
Journal Name
absorbance spectra when varying the pH from neutral to acidic
View Article Online
DOI: 10.1039/C9CP00672A
state. The red shift in the absorption spectra of these D-A-D type
fluorophores in the presence of hydrogen ions leads to obviously
narrowed band gap. Clearly, with the decrease of pH, the strong
absorption in the short wavelengths region depletes and new
absorption bands arise due to the influence of hydrogen ions (Fig. 3
and Fig. S27). Take fluorophore 5 as an example, with the increase
of the acidity, the strong absorption in the visible region (about 432
nm) decrease in the absorbance or even disappear and a new
absorption band (centered at around 525 nm) presents.
Furthermore, other fluorophores also display similar evolution
trends and mechanism in the corresponding absorbance spectra
(Fig. S27). We propose the quenching mechanism as follows: with
Fig. 2 (A) Images of fluorescence quenching/recovery of triazolopyridine-
thiophene D-A-D type conjugated fluorophores (exemplified by fluorophore 2)
the addition of acids (low pH), protons in the aqueous solution can
easily complex with the nitrogen atom of pyridine ring to form the
protonated complex, which destroys the π-conjugated double-bond
system of these fluorophores and hence results in significant
upon addition of HCl and reversed by NaOH in water-DMSO. (B) Fluorescence
Fig. 3 (A) The absorption spectral evolution of fluorophore 5 (15 μM) in the pH
quenching in emission spectra of fluorophore 2 (15 μM) against pH decrease
range of 7.00~4.31. (B) Proposed mechanism of fluorescence quenching for
from 7.00 to 0.00 (adjusted by addition of HCl). Excitation: 380 nm. (C)
triazolopyridine-thiophene D-A-D type conjugated fluorophores.
6
2
Fluorescence recovery in emission spectra of fluorophore 2-hydrions complex by
fluorescence quenching. On the other hand, the push–pull effect
adding bases (adjusted pH from 0.00 to 7.00 by NaOH). Excitation: 380 nm.
of D-A type molecules is reduced in acidic conditions.
63
3
.5 pH-induced fluorescence sensing of electrosynthesized
we recorded the emission spectra of these fluorophores at
different pH values (Fig. 2B, Fig. S26). Clearly, the fluorescence
intensity at maximum emission peak decreased gradually with
decreasing the pH owing to the protonation of nitrogen atom
on the pyridine ring. Such quenching of these fluorophores
provides an effective method to detect hydrogen ions. The
relationship between fluorescence intensity and the pH values
is shown in Fig. S26. Obviously, fluorescence intensity displays
a monotonical decrease against pH, revealing that this method
is suitable for detecting the unknown content of pH in a broad
pH range (0.0 ~ 7.0).
Reversibility will enable fluorophores to be utilized in a wider
range of applications. We find that the fluorescence quenching
of fluorophores against hydrogen proton can be recovered by
adding bases like NaOH into the system (Fig. 2C). With the
addition of bases, hydroxyl in the aqueous solution can easily
complex with the protons of protonated complex to form
renewedly the pyridine ring, which recovers the π-conjugated
double-bond system of these fluorophores and hence results
in significant fluorescence recovery. According to the
deprotonation of nitrogen on the pyridine ring, the
fluorescence intensity recovery of all these fluorophores is
calculated to be over 75%, implying the excellent reversibility
of the fluorescence quenching process. For instance, the
emission intensity of fluorophore 2 is calculated to be
approximately 76% with the addition of NaOH. These results
indicate the reusability of these materials for pH sensing. Such
results demonstrated that these fluorophores reveal excellent
and reversible pH-sensing photophysical properties, and can
be potentially employed as desirable bichromophoric sensor
materials for pH sensing.
polymers
According to the molecular-wire effect, D-A-D type conjugated
polymers generally exhibit excellent fluorescence and sensing
behaviors over their corresponding small molecules.
6
4-66
All
these molecules are supposed to be electropolymerizable due
to the terminal thiophene units. Quantum chemistry
calculation results also indicate the electropolymerization
should occur at the α-positions of the thiophenes based on to
the molecular orbital theory because of higher HOMO portions
at these sites (Table 1 and Table S2). To explore the
photophysical properties and sensing performances of the
conjugated polymers, we successfully electropolymerize these
fluorophores in the commonly used electrolytic system DCM-
6
TBAPF (Fig. 4A) The polymerization of these D-A-D type
fluorophores happens at α-positions of end-capping thiophene
units (Fig. S23 and Table S1). All these polymers are partially
dissolve in common organic solvents, and show significant red-
3
.4 Fluorescence quenching mechanism
To get an insight into the fluorescence quenching/recovery
mechanism, we investigate the absorbance spectral evolution of all
these fluorophores under different pH (Fig. 3 and Fig. S27). We find
that these fluorophores undergo obvious changes in the
Fig. 3 (A) The absorption spectral evolution of fluorophore 5 (15 μM) in the pH
range of 7.00~4.31. (B) Proposed mechanism of fluorescence quenching for
triazolopyridine-thiophene D-A-D type conjugated fluorophores.
6
| J. Name., 2017, 00, 1–3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Page 7 of 10
Physical Chemistry Chemical Physics
Journal Name ARTICLE
View Article Online
DOI: 10.1039/C9CP00672A
Fig. 5 Fluorescence test papers and inkjet-printed complex patterns towards
effective detection of acids (HCl vapor) and their recovery by bases (NH
vapor).
3 2
∙H O
-
1
Fig. 4 (A) Cyclic votammograms for the electropolymerization of 0.01 mol L
can be employed as excellent fluorescenc sensing materials
towards practical applications. We further demonstrate that
these fluoropheres reveal an excellent and reversible pH-
induced fluorescence quenching/recovery phenomenon.
Enabled by their good processability in common organic
solvents, we successfully fabricate sensing devices such as
fluorescence papers and complex inkjey-printed patterns for
the detection of volatile acids both in solution and vapor
atmosphere. Further device fabrication and related
applications by combining pH fluorescenc sensing behavior
and patterning of these molecules are underway in our lab.
-1
6
Fluorophore 2 in DCM-TBAPF . Potential scan rate: 100 mV s . (B) Fluorescence
quenching of P2 (15 μM in repeat units) at the neutral state and pH 2.0.
Fluorescence emission (C) and UV-vis absorption (D) spectra of P2 (15 μM in
repeat units) at the neutral state and pH 2.0. Excitation: 380 nm.
shifts in the emission peaks due to the elongation in π-
conjugated systems. Unfortunately, compared to their
monomeric precursors, they generally display weakened light-
emitting nature under 365 nm (Fig. 4 and Fig. S28) probably
due to broad molecular weight and compact packing during
the electropolymerization. Interestingly, these polymers also
display complete fluorescence quenching by adding acids to
pH=2.0 (Fig. 4B~D and Fig. S28), demonstrating similar sensing
phenomenon and mechanism with their monomeric
precursors.
Conflicts of interest
There are no conflicts to declare.
3
.6 Inkjet-printed complex patterns for practical flurescent sensing
applications
Acknowledgements
Patterning of conjugated fluorophores into complex
geometries is a crucial step for device fabricating and
customized requirements. The good solvent processability of
these triazolopyridine-thiophene conjugated fluorophores
enables us to fabricate stable fluorescent complex solid
patterns with advanced manufacturing techniques such as
inkjet printing. The fabricated pH test papers and patterns all
display effective fluorescence sensing with color changes
towards the sensing of acids and even volatile HCl vapor, and
can be almost completely recovered by using bases like
This work was supported by the National Natural Science
Foundation of China (51863009, 51763010), Innovation Driven
“
5511” Project of Jiangxi Province (20165BCB18016), Science
Foundation for Excellent Youth Talents in Jiangxi Province
20162BCB23053), the Key Research and Development
Program of Jiangxi Province (20171BBH80007,
0181ACB20010), and Science and Technology Foundation of
(
2
Jiangxi Educational Committee (GJJ160790). K. Q. thanks
Jiangxi Educational Committee for a Postgraduate Innovation
Program grant (YC2017-S409). N. J. thanks Jiangxi Science &
Technology Normal University for a Postgraduate Innovation
Program grant (YC2017-X26).
3 2
NH ∙H O (Fig. 5, Fig. S29, Movie S1, Movie S2). Multiple cyclic
fluorescence quenching/recovery tests also indicate very good
reversibility of such patterns, which can be advantageous for
6
7-72
practical flurescent sensing applications.
References
Conclusions
This work was supported by the National Natural Science
Foundation of China (51863009, 51763010), Innovation Driven
In summary, we successfully synthesized a series of novel
triazolopyridine-thiophene D-A-D type conjugated
fluorophores by Stille coupling with high yields. These
molecules exhibit very high fluorescence quantum yields both
in solution (80~89%) and in solid state (13%~26%), and thus
“
5511” Project of Jiangxi Province (20165BCB18016), Science
Foundation for Excellent Youth Talents in Jiangxi Province
20162BCB23053), the Key Research and Development
Program of Jiangxi Province (20171BBH80007,
0181ACB20010), and Science and Technology Foundation of
(
2
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2017, 00, 1–3 | 7
Please do not adjust margins

Please do not adjust margins
Physical Chemistry Chemical Physics
Page 8 of 10
ARTICLE
Journal Name
2
2
2
5
6
7
A.P. De Silva, T.P. Vance, M.E.S. West MViEewS Aartnicdle OGn.liDne.
Jiangxi Educational Committee (GJJ160790). K. Q. thanks
Jiangxi Educational Committee for a Postgraduate Innovation
Program grant (YC2017-S409). N. J. thanks Jiangxi Science &
Technology Normal University for a Postgraduate Innovation
Program grant (YC2017-X26).
Wright, Org. Biomol. Chem., 2008, 6, 2468.
DOI: 10.1039/C9CP00672A
S.L. Ming, S.J. Zhen, K.W. Lin, L. Zhao, J.K. Xu and B.Y. Lu.
ACS Appl. Mater. Interfaces, 2015, 7, 11089.
N.N. Jian, H. Gu, S.M. Zhang, H.T. Liu, K. Qu, S. Chen,
X.M. Liu, Y.F. He, G.F. Niu, S.Y. Tai, J. Wang, B.Y. Lu, J.K.
Xu and Y. Yu, Electrochim. Acta, 2018, 266, 263.
2
8
B.Y. Lu, S.L. Ming, K.W. Lin, S.J. Zhen, H.T. Liu, H. Gu, S.
Chen, Y.Z. Li, Z.Y. Zhu and J.K. Xu, New J. Chem., 2016,
References
4
0, 8316.
1
F. Hu, K. Schmidt-Rohr and M. Hong, J Am. Chem. Soc.,
012, 134, 3703.
29 S.L. Ming, S.J. Zhen, X.M. Liu, K.W. Lin, H.T. Liu, Y. Zhao,
B. Y. Lu and J.K. Xu, Polym. Chem., 2015, 6, 8248.
30 D. Baran, A. Balan, S. Celebi, B.M. Esteban, H.
Neugebauer, N.S. Sariciftci and L. Toppare, Chem.
Mater., 2010, 22, 2978.
31 S. Chaurasia, W.I. Hung, H.H. Chou and J.T. Lin, Org.
Lett., 2014, 16, 3052.
32 A. Patra, M. Bendikov and S. Chand, Acc. Chem. Res.,
2014, 47, 1465.
33 G.L. Gibson, T.M. McCormick and D.S. Seferos, J Am.
Chem. Soc., 2012, 134, 539.
34 H. Gu, S.L. Ming, K.W. Lin, S. Chen, X.M. Liu, B.Y. Lu and
J.K. Xu, Electrochim. Acta, 2018, 260, 772.
35 K.W. Lin, S. Chen, B.Y. Lu, and J.K. Xu, Sci. China Chem.,
2017, 60, 38.
36 S.C. Price, A.C. Stuart, L.Q. Yang, H.X. Zhou and W. You, J
Am. Chem. Soc., 2011, 133, 4625.
37 W.J. Ying, J.B. Yang, M. Wielopolski, T. Moehl, J.E.
Moser, P. Comte, J.L. Hua, S.M. Zakeeruddin, H. Tian
and M. Gratzel M, Chem. Sci., 2014, 5, 206.
38 Y. Hua, J. He, C.S. Zhang, C.J. Qin, L.Y. Han, J.S. Zhao, T.
Chen, W.Y. Wong, W.K. Wong and X.J. Zhu, J Mater.
Chem. A, 2015, 3, 3103.
39 H.L. Cheng, Z.S. Huang, L.Y. Wang, H. Meler and D.R.
Cao, Dyes Pigm., 2017, 13, 143.
40 Y. Sun, S.C. Chien, H.L. Yip, Y. Zhang, K.S. Chen, D.F.
Zeigler, D.F. Chen, F.C. Chen, B.P. Lin and A.K.Y. Jen, J
Mater. Chem., 2011, 21, 13247.
41 C. Risko, M.D. McGehee and J.L. Bredas, Chem. Sci.,
2011, 2, 1200.
42 Z.B. Henson, G.C. Welch, V.D.P. Thomas and C.B.
Guillermo, J. Am. Chem. Soc., 2012, 134, 3766.
43 Z.W. Wang, Q. Zhang, K. Zhang and G.K. Hu, Adv. Mater.,
2016, 28, 9857.
2
2
N. Kang, J.H. Park, K.C. Ko, J. Chun, E. Kim, H.W. Shin,
S.M. Lee, H.J. Kim, T.K. Ahn, J.Y. Lee and S.U. Son,
Angew. Chem. Int. Ed., 2013, 52, 6228.
3
4
5
6
X.H. Li, X.H. Gao, W. Shi and H.M. Ma, Chem. Rev., 2014,
1
14, 590.
J. Yin, Y. Hu and J. Yoon, Chem. Soc. Rev., 2015, 44,
619.
4
J.J. Deng, K. Wang, M. Wang, P. Yu and L.Q. Mao, J Am.
Chem. Soc., 2017, 139, 5877.
I.H. Park, A. Chanthapally, Z.J. Zhang, S.S. Lee, M.J.
Zaworotko and J.J. Vittal, Angew. Chem. Int. Ed., 2014,
5
3, 414.
7
S.Y. Yang, X.L. Deng, R.F. Jin, P. Naumov, M.K. Panda,
R.B. Huang, L.S. Zheng and B.K. Teo, J Am. Chem. Soc.,
2
014, 136, 558.
8
9
1
1
Y. Tang, J.J. Li, Q.F. Guo and G.M. Nie, Sens. Actuator B
Chem., 2019, 282, 824.
G.M. Nie, Y. Tang, B. Zhang, Y. Wang and Q.F. Guo,
Biosens. Bioelectron., 2018, 116, 60.
G.M. Nie, Y. Wang, Y. Tang, D. Zhao and Q.F. Guo,
Biosens. Bioelectron., 2018, 101, 123.
J. Deng, J.F. Li, P.N. Chen, X. Fang, X.M. Sun, Y.S. Jiang,
W. Weng, B.J. Wang and H.S. Peng, J Am. Chem. Soc.,
0
1
2
015, 138, 225.
1
2
J. Deng, Y. Zhang, Y. Zhao, P.N. Chen, X.L. Cheng and H.S.
Peng, Angew. Chem. Int. Ed., 2015, 54, 15419.
H. Meier, Angew. Chem. Int. Ed., 2005, 44, 2482.
P.M. Beaujuge, S. Ellinger and J.R. Reynolds, Nat.
Mater., 2008, 7, 795.
1
1
3
4
1
5
R. Mukherji, A. Samanta, R. Illathvalappil, S. Chowdhury,
A. Prabhune and R.N. Devi, ACS Appl. Mater. Interfaces,
2
013, 5, 13076.
1
6
M. Albota, D. Beljonne, J.E. Bredas, J.E. Ehrlich, J.F. Fu,
A.A. Heikal, S.E. Hess, T. Kogej, M.D. Levin, S.R. Marder,
D. Mccord-Maughon, J.W. Perry, H. Röckel, M. Rumi,
G. Subramaniam, W.W. Webb, X.L. Wu and C. Xu,
Science, 1998, 281, 1653.
44 K. Zhang, H.L. Duan, B.L. Karihaloo and J. Wang, Proc.
Natl. Acad. Sci. U. S. A., 2010, 107, 9502.
45 T. Lei, J.H. Dou, Z.J. Ma, C.H. Yao, C.J. Liu, J.Y. Wang and
J. Pei, J. Am. Chem. Soc., 2012, 134, 20025.
46 X. Zhang, T.T. Steckler, R.R. Dasari, S. Ohira S, W.J.
Potscavage Jr, S.P. Tiwari, S. Coppee, S. Ellinger, S.
Barlow, J.L. Bredas, B. Kippelen, J.R. Reynolds and S.R.
Marder, J. Mater. Chem., 2010, 20, 123.
47 T.T. Steckler, P. Henriksson, S. Mollinger, A. Lundin, A.
Salleo and M.R. Andersson, J. Am. Chem. Soc., 2014,
136, 1190.
48 D. Aldakov, M.A. Palacios and P. Anzenbacher, Chem.
Mater., 2005, 17, 5238.
49 M. Icli-Ozkut, H. Ipek, B. Karabay, A. Cihancer and A.M.
Onal, Polym. Chem., 2013, 4, 2457.
50 E.G. Wang, C. Li, W.L. Zhuang, J.B. Peng and Y. Cao, J
Mater. Chem., 2008, 18, 797.
51 M.L. Saha, X. Yan and P.J. Stang, Acc. Chem. Res., 2016,
49, 2527.
52 X. Sun, Y. Wang and Y. Lei, Chem. Soc. Rev., 2015, 44,
8019.
53 G. Feng and B. Liu, Small, 2016, 12, 6528.
54 Y.F. Wang, T. Zhang and X.J. Liang, Small, 2016, 12,
6451.
1
1
7
8
A. Haldi, A. Kimyonok, B. Domercq and L.E. Scholz, Adv.
Funct. Mater., 2008, 18, 3056.
M.C. Scharber, M. Koppe, J. Gao, F. Cordella, M.A. Loi, P.
Denk, M. Morana, H.J. Egelhaaf, K. Forberich, G.
Dennler, R. Gaudiana, G. Waller, Z.G. Zhu, X.B. Shi and
C.J. Brabec, Adv. Mater., 2010, 22, 367.
1
2
9
0
Y. Yu, L. Ye, Y.M. Song, Y.D. Guan, J.F. Zang, Extreme
Mech. Lett., 2017, 11, 128.
Y. Yu, S.L. Jiang, G.Z. Zhang, W.L. Zhou, X.S. Miao, Y.K.
Zeng, J. Wang, J.G. He and L. Zhang, Appl. Phys. Lett.,
2
012, 101, 073113.
2
2
2
2
1
2
3
4
Q.A. Best, R.S. Xu, M.E. McCarroll, L.C. Wang and D.J.
Dyer, Org. Lett., 2010, 12, 3219.
S. Kang, S. Kim, Y.K. Yang, S. Bae and J. Tae, Tetrahedron
Lett., 2009, 50, 2010.
H. Langhals, O. Krotz, K. Polborn and P. Mayer, Angew.
Chem. Int. Ed., 2005, 44, 2427.
I.D.W. Samuel and G.A. Turnbull, Chem. Rev., 2007, 107,
1
272.
8
| J. Name., 2017, 00, 1–3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Page 9 of 10
Physical Chemistry Chemical Physics
Journal Name ARTICLE
5
5
6
J. Mei, N.L.C. Leung, R.T.K. Kwok, J.W.Y. Lam and B.Z.
View Article Online
DOI: 10.1039/C9CP00672A
Tang, Chem. Rev., 2015, 115, 11718.
5
W.H. Huang, X.P. Zhang, B. Chen, H. Miao, C.O. Trindle,
Y.C. Wang, Y. Luo and G.Q. Zhang, Chem. Comm., 2019,
5
5, 67.
5
5
5
6
6
7
8
9
0
1
J. Peng, W.Q. Yin, J. Shi, X.Y. Jin and G. Ni, Microchim.
Acta, 2019, 186, 24.
G.
DOI:10.1021/acs.bioconjchem.8b00861.
G.C. Welch and G.C. Bazan, J Am. Chem. Soc., 2011, 133,
632.
Y.K. Yang, K.J. Yook and J. Tae, J Am. Chem. Soc., 2005,
27, 16760.
Meltem,
Biomol.
Chem.,
2019,
4
1
L. Prodi, C. Bargossi, M. Montalti, N. Zaccheroni, N. Su,
J.S. Bradshaw, R.M. Izatt and P.B. Savage P.B, J Am.
Chem. Soc., 2000, 122, 6769.
6
6
6
6
6
2
3
4
5
6
C.G. Niu, X.Q. Gui, G.M. Zeng, A.L. Guan, P.F. Gao and
P.Z. Qin, Anal. Biochem., 2005, 383, 349.
V.B. Bojinov, N.I. Georgiev and N.V. Marinova, Sens.
Actuator B Chem., 2010, 148, 6.
A.H. Malik, S. Hussain, A. Kalita and P.K. Iyer, ACS Appl.
Mater. Interfaces, 2015, 7, 26968.
T. Bhuvana, B. Kim, X. Yang, H. Shin and E. Kim, Angew.
Chem. Int. Ed., 2013, 52, 1180.
S. Seo, C. Allain, J. Na, S. Kim, X. Yang, C. Park, J.
Malinge, P. Audebert and K. Kim, Nanoscale, 2013, 5,
7
321.
6
6
6
7
7
7
7
8
9
0
1
2
J. Liu, C. Tan and O. A. Scherman, Angew. Chem. Int.
Eng., 2018, 57, 8854.
J. Liu and O. A. Scherman, Adv. Funct. Mater., 2018, 28,
1
800848.
G.Y. Gu, J. Zou, R.K. Zhao, X.H. Zhao and X.Y. Zhu, Sci.
Robot., 2018, 3, 2874.
G.Y. Gu, U. Gupta, J. Zhu, L.M. Zhu and X.Y. Zhu, IEEE
Trans. Robot., 2017, 33, 1263.
H. Yuk, B.Y. Lu and X.H. Zhao, Chem. Soc. Rev., 2018,
DOI:10.1039/c8cs00595h
B.Y. Lu, H. Yuk, S.T. Lin, N.N. Jian, K. Qu, J.K. Xu and X.H.
Zhao, Nat. Commun., 2019, DOI: 10.1038/s41467-019-
0
9003-5.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2017, 00, 1–3 | 9
Please do not adjust margins

Physical Chemistry Chemical Physics
Page 10 of 10
View Article Online
DOI: 10.1039/C9CP00672A
A series of novel triazolopyridine-thiophene D-A-D type conjugated
fluorophores are successfully synthesized by Stille coupling with high yields. These
fluoropheres exhibit very high fluorescence quantum yields both in solution (80~89%)
and in solid state (13%~26%), and thus can be employed as excellent fluorescenc
sensing materials towards practical applications. These fluoropheres reveal an
excellent and reversible pH-induced fluorescence quenching/recovery phenomenon.
Enabled by their good processability in common organic solvents, sensing devices
such as fluorescence papers and complex inkjey-printed patterns are successfully
fabricated for the detection of volatile acids both in solution and vapor atmosphere.