Deep blue electro-fluorescence and highly efficient chemical warfare agent sensor: Functional versatility of weak coupling hybridized locally excited and charge-transfer excited state

Article abstract of DOI:10.1016/j.dyepig.2020.108317

A weakly-coupled hybridized locally-excited and charge-transfer hybridized locally-excited and charge-transfer (HLCT) dual-functional material TPA-2CNTAZ is designed and synthesized. The dispersed state of TPA-2CNTAZ exhibits deep blue electroluminescent

Full text of DOI:10.1016/j.dyepig.2020.108317

Journal Pre-proof
Deep blue electro-fluorescence and highly efficient chemical warfare agent sensor:
Functional versatility of weak coupling hybridized locally excited and charge-transfer
excited state
Man Wang, Zhiyong Cheng, Xiangyu Meng, Ying Gao, Xinqi Yang, Haichao Liu, Shi-
Tong Zhang, Hongwei Ma, Bing Yang
PII:
S0143-7208(20)30323-5
DOI:
https://doi.org/10.1016/j.dyepig.2020.108317
DYPI 108317
Reference:
To appear in: Dyes and Pigments
Received Date: 4 February 2020
Revised Date: 27 February 2020
Accepted Date: 27 February 2020
Please cite this article as: Wang M, Cheng Z, Meng X, Gao Y, Yang X, Liu H, Zhang S-T, Ma H, Yang B,
Deep blue electro-fluorescence and highly efficient chemical warfare agent sensor: Functional versatility
of weak coupling hybridized locally excited and charge-transfer excited state, Dyes and Pigments
(2020), doi: https://doi.org/10.1016/j.dyepig.2020.108317.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition
of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of
record. This version will undergo additional copyediting, typesetting and review before it is published
in its final form, but we are providing this version to give early visibility of the article. Please note that,
during the production process, errors may be discovered which could affect the content, and all legal
disclaimers that apply to the journal pertain.
© 2020 Published by Elsevier Ltd.

M. Wang, Z. Cheng, Dr. X. Meng, Y. Gao, X. Yang, Dr. H. Liu. Dr. S. Zhang*, Prof.
Dr. H. Ma*, Prof. Dr. B. Yang*
Deep Blue Electro-Fluorescence and Highly Efficient Chemical Warfare Agent
Sensor: Functional Versatility of Weak Coupling Hybridized Locally Excited and
Charge-Transfer Excited State
Highlights：
(1) The excited state design strategy of weak-coupling in TPA-2CNTAZ opens up a
new possibility for the design of dual-functional materials of deep-blue emission
and efficient sensors.
(2) Deep blue HLCT electrofluorescence with a CIE of (0.156, 0.065) and a EQE of
2.8% is achieved in the doped OLED.
(3) Highly efficient CWA analogue test strip is developed basing on TPA-2CNTAZ,
with an excellent LOD of 0.69 ppb, which is among the best reported results.

Deep Blue Electro-Fluorescence and Highly Efficient Chemical Warfare Agent Sensor:
Functional Versatility of Weak Coupling Hybridized Locally Excited and Charge-
Transfer Excited State
Man Wang 1, Zhiyong Cheng 2, Xiangyu Meng 1, Ying Gao 1, Xinqi Yang 1, Haichao Liu 1, Shi-
Tong Zhang 1, *, Hongwei Ma 2, * and Bing Yang 1, *
M. Wang, Dr. X. Meng, Y. Gao, X. Yang, Dr. H. Liu. Dr. S. Zhang, Prof. Dr. B. Yang
State Key Laboratory of Supramolecular Structure and Materials, Institute of Theoretical
Chemistry, College of Chemistry, Jilin University, Changchun, 130012, China
E-mail: stzhang@jlu.edu.cn, yangbing@jlu.edu.cn
Z. Cheng, Prof. Dr. H. Ma
Department of Chemistry and Chemical Engineering, College of Chemistry, Chemical
Engineering and Resource Utilization, Northeast Forestry University, Harbin 150040, China
E-mail: mahw@nefu.edu.cn
Keywords: OLED, blue-emission, HLCT, CWA, organic sensor
Abstract
A weakly-coupled hybridized locally-excited and charge-transfer hybridized locally-
excited and charge-transfer (HLCT) dual-functional material TPA-2CNTAZ is designed and
synthesized. The dispersed state of TPA-2CNTAZ exhibits deep blue electroluminescent (EL)
with an exceeding exciton utilization of 53%, and the aggregated state of TPA-2CNTAZ
displays efficient detection to the analogue of chemical warfare agents with an excellent limit
of detection of 0.69 ppb.
1. Introduction
The structure diversity of pure organic luminescent materials, as well as the diversity of
their excited state properties, entitles them boundless application possibilities in the field of
illumination, displayer and sensors. In recent years, the applications of donor-acceptor (D-A)
fluorescent materials in the next-generation organic light emitting diode (OLED) are
attracting increasing attention,[1] not only owing to their low cost and comparable high EL
1

efficiency to the phosphorescent noble-metal-complexes,[2] but also because that they point
out an access for the utilization of the spin-forbidden electrogenerated triplet excitons, which
account for 75% of the total electrogenerated excitons in OLED.[3] The representative two D-
A material systems that can fully utilize the electrogenerated excitons in OLED are the
thermally activated delayed fluorescent (TADF) materials and the HLCT materials.[4][5]
Although there is still no clear mechanism, the generally accepted view on the high EL
efficiency of the above two material systems is that HLCT excited state is usually associated
with different charge-transfer (CT) excited state properties,[6] which can decrease the binding
energy of electrogenerated-exciton and minimize the energy gap between the singlet and
triplet energy levels, thus an efficient reversed intersystem crossing (RISC) can be guaranteed
for the utilization efficiency of the electrogenerated triplet excitons. However, high EL
efficiency depends on both electrogenerated exciton utilizing efficiency (EUE) and the photo
luminescent (PL) efficiency. The separated hole and electron moieties of CT excitons always
cause a decreased photo luminescent quantum yield (PLQY), therefore, the molecular design
method for the D-A electro-fluorescent materials should also consider this issue. More
importantly, for the design of blue-emissive materials, CT excited state component will also
decrease the exciton energy and cause a red-shifted emission.[7] Therefore, for the
simultaneous realization of satisfied blue color and efficiency, the CT hybridization form
should be carefully considered.
Chemical warfare agents (CWAs), such as sarin, soman, tabun, VX and so on, are toxic and
fast acting to human body, which have been threatening the public security and international
security in the recent decades.[8] Standing out from the traditional detection method of CWAs
such as mass spectroscopy, ion spectroscopy and electrochemical methods, the recently
appeared fluorescence detection method is low-cost and rapid-response,[9] more importantly,
it is suitable for the on-site detection due to that the fluorescence spectrometer can be portable.
In the past five years, many works on the fluorescent detection of CWAs (or their reactivity
2

weakened CWA analogue diethyl chlorophosphite (DCP)) with high sensitivity were reported,
however, the detection mechanisms, including the reaction process and the photophysical
process that is related to the excited state properties, still remained unclear,[10] which limited
the development of the CWAs fluorescent detection for a while. In the last year, we reported
the application of efficient DCP detection with a D-A structure HLCT sensor TPA-9AC.[11]
The sp2 hybridized nitrogen atom is of chemical reactivity to the CWAs and their reactivity
weakened analogue DCP under water (Scheme S1), so that the excited state property,
specifically, the hybridization status of an HLCT sensor sharply changes when DCP reacts
with the sensor, along with rapid and significant fluorescent quenching, calling the de-
hybridization mechanism.[11-12] Different from the traditional mechanisms such as the
photoinduced electron transfer (PET) and the fluorescence resonance energy transfer
(FRET),[13] this de-hybridization mechanism can realize an extraordinary LOD of less than 1
ppb and very fast response of less than 3 seconds, demonstrating great application potential in
the efficient on-site detection of CWAs.
Notably, although TPA-9AC does not possess high PLQY, its weakly-coupled LE and CT
components greatly contributes to its efficient detection performance. Considering that the LE
exciton is always of higher energy and is more suitable for blue-emission, the rationally
designed weak coupling materials can hopefully be dual-functional materials: blue-emission
originated from the LE-like excited state property and the efficient detection to CWAs and
DCP owing to the weak interstate coupling. In this work, we reported the excited state design,
synthesis and structure-property relationship of an HLCT material 4,4'-(4-(4'-
(diphenylamino)-[1,1'-biphenyl]-4-yl)-4H-1,2,4-triazole-3,5-diyl)-dibenzonitrile(TPA-
2CNTAZ, Scheme 1), as well as its applications in blue-emissive OLED and CWA sensor.
TPA-2CNTAZ is designed to be an orthogonal HLCT material with weak interstate coupling
between S1 (LE) and S2 (CT) excited states.[5e,14-15] On the one hand, the emissive LE excited
state provides blue-shifted emission and the high-lying CT excited state guarantees exceeding
3

electro-exciton utilizing efficiency (EUE), contributing to the efficient deep-blue electro-
fluorescence. More importantly, different from the single-molecular HLCT state of TPA-9AC,
the interstate coupling of the LE and CT excited state components of TPA-2CNTAZ are even
weaker, resulting in an inter-molecular excimer emission, which is beneficial to the efficient
fluorescence detection of the CWAs and their analogues. The TPA-2CNTAZ neat film
demonstrates an exciplex emission, and the limit of detection (LOD) to the CWA DCP of the
prepared TPA-2CNTAZ test strip is as excellent as 0.69 ppb, which not only meets the
“harmless” level of human response to acute sarin exposure (7 ppb), but also stands out
among the reported results.
Scheme 1 The synthesis route of TPA-2CNTAZ.
2. Experimental Methods
2. 1 Synthesis
All the reagents were purchased from Acros and Changchun Sanbang without further
1
purification. The H NMR and 13C NMR were recorded on a Bruker AVANCZ 500
1
spectrometer at 500MHz, using DMSO as the solvent for H NMR and CDCl3 as the solvent
4

for 13C NMR at 298 K, using tetramethylsilane (TMS) as the internal standard. The synthesis
details in Scheme 1 are as follows:
4-cyano-N'-(4-cyanobenzoyl)benzohydrazide (CN-O-CN): 4-Cyanobenzoylchloride (9.9
g, 60 mmol) and triethylamine (8.3 mL, 60 mmol) were mixed in dichloromethane (90 mL)
and stirred for 10 min. Then hydrazine monohydrate (1.5 g, 30 mmol) was added into the
stirring solution using injection syringe drop by drop at 0 . After 30 min, the solution was
moved to room temperature and then stirred for another 4 h, and collected the white
precipitate. Then the crude product (white powder, 7.482g, yield=86%) was washed with
petroleum ether and deionized water and directly used as the reactant of the next step without
1
further purification. MS: MW 290.08, m/z=290.08(M+). H NMR (500 MHz, DMSO) δ 8.11
(d, J = 8.4 Hz, 4H), 8.02 (d, J = 8.3 Hz, 4H).
N-(chloro(4-cyanophenyl)methylene)-4-cyanobenzohydrazonoyl chloride (CN-Cl-CN):
CN-O-CN (6.96g, 24 mmol), phosphorus pentachloride (12.48 g, 60 mmol) and toluene (120
mL) were mixed in a 250 mL flask and refluxed at 110 for 3h under nitrogen atmosphere,
and the exhaust gas was absorbed with diluted NaOH solution or collected using a Y-pipe
connected balloon. The reaction can be quenched using deionized water (10 mL), and the
crude product can be collected by directly concentrated the solution and recrystallization
using ethanol. The crude product (citrine powder 5.48 g, yield=70%) was directly used as the
1
reactant of the next step without further purification. MS: MW 325.9, m/z=326.01(M+). H
NMR (500 MHz, DMSO) δ 10.08 (s, 2H), 8.11 (d, J = 1.7 Hz, 4H), 8.01 (d, J = 1.8 Hz, 4H).
4,4'-(4-(4-bromophenyl)-4H-1,2,4-triazole-3,5-diyl)dibenzonitrile (2CN-TAZ-Br): CN-
Cl-CN (2.1 g, 5 mmol) and 4-Bromoaniline (1.032 g, 6 mmol) were added to 30 ml degassed
N,N-dimethylformamide (DMF) in a 150 mL flask. The reaction mixture was initially
refluxed at 135 for 12 h under nitrogen atmosphere, cooled down to room temperature, then,
HCl (10 mL, 2 N) was dropwise added and stirred for another 1 h, the brown powder crude
product (1.08 g, yield=51%) can be collected by filtration. The crude product was then
5

washed with deionized water and dried in vacuum, and directly used as the reactant of the
1
next step without further purification. MS: MW 426.28，m/z=426.28(M+). H NMR (500
MHz, DMSO) δ 8.16 – 8.11 (m, 1H), 7.93 – 7.87 (m, 3H), 7.75 – 7.71 (m, 2H), 7.61 – 7.55
(m, 4H), 7.51 – 7.43 (m, 2H).
4,4'-(4-(4'-(diphenylamino)-[1,1'-biphenyl]-4-yl)-4H-1,2,4-triazole-3,5-
diyl)dibenzonitrile (TPA-2CNTAZ): 2CN-TAZ-Br (0.64 g, 1.5 mmol) and 4-
(Diphenylamino)phenylboronicacid (0.725 g, 2.5 mmol) were added to a mixed solvent of 2M
K2CO3 aqueous solution (10 mL), THF and toluene (2: 3: 3 volume ratio) and degassed, then
Pd(PPh3)4 (52 mg) was added under nitrogen atmosphere, and the reaction system was
degassed for another three times, and refluxed at 90℃ for 48 h. The reaction solution was
extracted with dichloromethane and the organic layer was dried with MgSO4. The crude
product was purified by column chromatography, and fluorescent yellow pure product was
1
obtained (0.61g, yield=69%). MS: MW 590.71. m/z=590.69(M+). H NMR (500 MHz,
CDCl3) δ 7.74 (d, J = 8.1 Hz, 2H), 7.64 (s, 8H), 7.54 (d, J = 8.7 Hz, 2H), 7.32 (t, J = 7.9 Hz,
4H), 7.24 (d, J = 8.1 Hz, 2H), 7.18 (dd, J = 11.5, 8.2 Hz, 6H), 7.11 (t, J = 7.4 Hz, 2H). 13C
NMR (500 MHz, CDCl3) 153.75, 148.65, 147.26, 143.03, 132.37, 132.33, 131.41, 130.70,
129.47, 129.10, 128.29, 127.74, 124.89, 123.63, 123.24, 117.99, 113.76. Calculate for
C40H26N6: C, 81.34; H, 4.44; N, 14.23; Found: C, 81.80; H, 4.58; N, 14.04.
2. 2 Fluorescence detection of DCP
Preparation of TPA-2CNTAZ test strips: The filter paper (without fluorescence) is cut
into strips with the size of 0.5 cm × 3 cm, and are dipped in a 0.2 ~ 0.5 mg/mL TPA-
2CNTAZ/CHCl3 solution. The dipped strips are then dried for detection.
Preparation and Detection of DCP solution: 3 mL DCM was put into the quartz cuvette,
after adding 3 µL DCP (0.01 M) into the cuvette and stirring for 10 s, the fluorescence
6

spectrum was recorded under the excitation at 365 nm. The same operation was recorded as
the DCP concentration increased.
Preparation and Detection of DCP vapor: At 25 0C, 2 mL DCP was injected into a 0.5 L
sampling bag and sealed the bag for 72 h. The concentration of saturation vapor pressure of
DCP is 132 ppm. Based on saturated vapor, we could obtain different concentrations of DCP
by injecting an amount of saturated DCP vapor into sampling bags in a range of size. Then,
the test strips were put into 40 mL cuvettes, injected different concentrations of DCP and put
the same test strips in the fluorimeter. The fluorescence intensity of test strips was recorded.
2. 3 Theoretical Calculations
The density functional theory (DFT) calculations and the natural transition orbit (NTO)
analysis are carried out using a Gaussian 09 D.01 Package. The excited state conformations
are optimized using td/m062x/6-31g(d, p) method, and the excited state properties are
calculated using the same method straight after.
3. Results and Discussions
3. 1 Photophysical Properties
To take a glance at the excited state property of TPA-2CNTAZ, we initially investigated its
natural transition orbit (NTO) using Gaussian 09 package.[16-17] In Figure 1a, the transition
character of S1 excited state of TPA-2CNTAZ is the LE transition of the 4-phenyl-substituted
triphenylamine (4-P-TPA), and the S2 excited state is the CT transition from the 4-P-TPA
donor to the “2CNTAZ” acceptor. Due to the totally different transition patterns, the energy
gap of the two excited states is quite large (0.46 eV, Figure S1), suggesting that the two
7

excited states are of very small coupling, and TPA-2CNTAZ is probably a LE emitter, whose
emission is assigned to the π→π* transition of 4-P-TPA moiety. However, judging from
Figure 1b, TPA-2CNTAZ also seems to be of typical strong CT property, since that its
solvatochromic PL spectra display a very large red-shift of near 160 nm, and more
importantly, the obvious indicator of pure CT excited state, that is, the dual-fluorescent
emission can be observed in the large-polarity solvent acetonitrile. Therefore, despite that
they seem to be totally different in transition pattern and efficiency (or the oscillator strength),
the two excited states (S1 and S2) should be both responsible to the emission of TPA-
2CNTAZ. The above conclusion can be verified by another three experimental facts:
(1) The first is that a vibrational fine-structure also appears in the small-polarity solvent
hexane in Figure 1b, which implies that the LE excited state character also dominates the
photophysical property of TPA-2CNTAZ.
(2) The second is that the photo-luminescent quantum yield (PLQY) and the radiative
transition rate constant (kr) of the four diluted solvents decreases in sequence till near zero in
acetonitrile (Table S1, Figure S2), assigning to the gradually changed emissive excited state
properties from LE to CT.
(3) The last is that a well correlated linear relationship can be found between the solvent
polarity factor (f) and the Stokes shift in the Lippert-Mataga solvatochromic model (Figure
1c, Figure S3), which assigns to one well-hybridized excited state in TPA-2CNTAZ. This
excited state is CT-like, because its excited state transitional dipole moment (µe) of TPA-
2CNTAZ can be estimated as large as 26 Debye.
8

Figure 1 (a) The NTO of the emission-relative excited states of TPA-2CNTAZ. The
molecular geometry of TPA-2CNTAZ is optimized using cam-b3lyp/6-31g (d, p) method, and
the excited state properties are calculated using td-cam-b3lyp/6-31g (d, p) method. (b) The
emission spectra of TPA-2CNTAZ in four solvents with sequentially increasing polarities.
The excitation wavelengths of different solutions can be found in Table S2. The concentration
of the solutions is < 10-5 mol/L to guarantee the monodispersity. (c) The Lippert-Mataga
solvatochromic model of TPA-2CNTAZ.
3. 2 Weakly Hybridization in TPA-2CNTAZ and Its OLED Performances
According to the above photophysical experimental facts, different from the well
hybridized excited states (Scheme 2a), the emission of TPA-2CNTAZ can be recognized as
an HLCT emission with weakly coupled LE and CT excited state components (Scheme 2b)
with a characteristic NTO image of typically LE-like transition. This kind of excited state is
suitable to construct more blue-shifted materials since the CT components effect is weaker
than the well-hybridized excited states. Nevertheless, the weak coupling CT component of
TPA-2CNTAZ can also grant TPA-2CNTAZ an exceeding EUE in OLED, more than that, the
weak coupling of LE and CT ensures the blue-shifted emission of TPA-2CNTAZ. As a result,
the doped OLED of TPA-2CNTAZ demonstrates a deep-blue emission, whose Commission
Internationale de l'Eclairage (CIE) coordinate is (0.156, 0.065). More importantly, an
exceeding EUE of 53% and an EQE of 2.8% is achieved in the doped OLED, which is a
9

satisfied result in the deep blue electro-emissive materials (Figure 2). Note again that the
lifetimes of TPA-2CNTAZ solutions are nanosecond-scaled and single-exponential decayed,
revealing that TPA-2CNTAZ is not a TADF material, coinciding to its large singlet-triplet
energy gap (Figure S4). Additionally, the thermal stability of TPA-2CNTAZ is decent, whose
glass-transition temperature is as high as 133℃ (Figure S5a), which implies that by further
structural modification, applicable deep-blue emissive materials are hopefully be realized
using the weak-coupling strategy.
Scheme 2 Schematic diagram of interaction between LE and CT excited states: (a) traditional
hybridized material and (b) weak-coupled material.
10

Figure 2 The EL performance of TPA-2CNTAZ doped OLED: the EQE-current density
relations and inset is the EL spectra.
Notably, although the full width at half maxima (FWHM) of the doped and the non-doped
films are quite similar, the lifetime of the non-doped film is two orders of magnitude longer
than that of the doped film, which can be as long as 146 ns. Recently we reported a series of
anthrancene based excimer emissive crystals with particular face-to-face (or π-π) stacking
pattern and similar large red-shift and long-lifetimes, but once the face-to-face stacking is
broken, such red-shift and long-lifetime will also disappear, since the excimer emission
strongly depends on the above face-to-face stacking and the effective molecular interaction.
[18]
The similar emission of TPA-2CNTAZ neat film can be defined as an excimer emission
afterall, since there is indeed no other ingredient in its neat film. However, instead of the
regularly stacked, face-to-face crystalline phase in the anthracene derivates, the wide, red-
shifted and long-lifetime emission can be easily realized in the amorphous film (Figure 3b).
Considering the strong CT property of TPA-2CNTAZ, the ultralong lifetime of TPA-
2CNTAZ can also be probably explained as the intermolecular exciplex CT emission from the
donor moiety of one molecule to the acceptor moiety of another molecule (Figure 5b). This
hypothesis can also be revealed by the fact that the EQE of TPA-2CNTAZ non-doped OLED
with a traditional device structure is not as satisfied as those based on the reported HLCT
materials, due to that TPA-2CNTAZ tends to form exciplex emission together with the
transporting or blocking layer materials. (Figure S11, Table S4)) Although the excimer and
exciplex emission are usually a negative factor in blue-emissive OLED, nevertheless, they can
be even more circumstance-sensitive than the monomer is, which is very suitable for the
application of stimulation-response.
11

Figure 3 The PL spectra and the PL decay spectra of (a) doped and (b) non-doped films of
TPA-2CNTAZ. The lifetimes of the doped and the non-doped films are 5.08ns and 146ns,
respectively. The host material of the doped film is polymethylmethacrylate (PMMA), and the
mass fraction of TPA-2CNTAZ is 20%.
3. 3 CWA Analogue Sensor Performance
As we have stressed, the sp2 hybridized nitrogen atoms in the acceptor unit of D-A
materials can meet the demand of efficient sensor to CWAs. Moreover, a more efficient
detection of CWAs can be expected in the situation of TPA-2CNTAZ, because the exciplex
emission can be more sensitive to the external stimulations. Regarding to the above
advantages, we prepared TPA-2CNTAZ fluorescence test strips for DCP detecting (Figure
4a). Upon DCP treating, the emission of the TPA-2CNTAZ test strip displays a fast
(responding time of < 2s), efficient quenching with an LOD of 0.69 ppb (Figure 4b and
Figure 4c), which is among the best results that have been reported (Table S5).[19] More
importantly, this TPA-2CNTAZ test strip shows decent retrievability (by simply exposing in
ammonia vapor to neutralize the TPA-2CNTAZ hydrochloride, Scheme 2) and selectivity
(Figure 4d and Figure 4e, respectively), which is hopeful for the practical application in real-
time detection of CWAs.
Except for the fast-reaction mechanism that we have mentioned above, specifically, the
mechanism of the efficient detection of TPA-2CNTAZ test strip can also be understood by the
12

change of the excited state properties of TPA-2CNTAZ aggregates from the bare and
protonated status. The single crystal structure of TPA-2CNTAZ is difficult to obtain, so that
we optimized the conformation of TPA-2CNTAZ bare dimer for further discussion. As shown
in Figure 5a, the optimized TPA-2CNTAZ dimer is a face-to-face structure, in which the
triphenylamine donor of one molecule is adjacent to the TAZ acceptor of the other molecule,
and the distance of the two molecules is about 8.4 Angstrom. The NTO of the bare dimer
shows a particular intermolecular HLCT character, whose S1 and S2 NTO both possess largely
overlapped hole and electron, which can afford an effective emission for the function of
fluorescent sensor. [20] This intermolecular HLCT can be destroyed after a hydrion is added on
one TPA-2CNTAZ molecule (Figure 5b), corresponding to the sufficient quenching in
Figure 4b. Notably, this quenching can be clearly confirmed by the shortened lifetime of the
protonated TPA-2CNTAZ (Figure S6), reflecting that the non-radiative rate rises after DCP
treating. The last but not the least, the performance of single-molecular dispersed diluted
TPA-2CNTAZ solution is poor, proving that the formation of the excimer emission is crucial
for the efficient detection of DCP.
13

Figure 4 The DCP detection performance of TPA-2CNTAZ test strip. (a) The image of the
TPA-2CNTAZ test strip before and after DCP treatment. (b) the PL spectra of TPA-2CNTAZ
test strip upon different concentration of DCP vapors. (c) The linear correlation of vapor-
concentration to quenching efficiency, whose slope is in inversely proportional relationship to
LOD. (d) The retrievability experiment of TPA-2CNTAZ test strip. (e) The selectivity
experiment of TPA-2CNTAZ test strip.
14

Figure 5 The NTO of (a) bared and (b) mono-protonated TPA-2CNTAZ dimer based on the
optimized geometry. We choose mono-protonated molecular model because that the
concentration of DCP is far less than that of TPA-2CNTAZ test strip.
4. Conclusions
In summary, we report the design and synthesize of a dual-functional HLCT material
(TPA-2CNTAZ) and investigate its applications in blue-emissive OLED and efficient
detections to CWAs in this work. On one hand, owing to the weakly-coupled LE- and CT-
excited state components, TPA-2CNTAZ demonstrates satisfied deep blue emission in the
doped OLED with exceeding EUE. On the other hand, thanks to the sensitive intermolecular
HLCT property of the TPA-2CNTAZ exciplex, the TPA-2CNTAZ based test strip exhibits
extremely potential outcomes in the fast, efficient detection of chemical weapons. This work
not only reflects a new understanding on the HLCT excited state theory, but also provides
effective molecular designing methods for the dual- or even multi- functional organic
fluorescent materials.
Acknowledgements
This work is supported by the National Natural Science Foundation of China (51803071,
51903031 and 91833304), the National Basic Research Program of China
(2016YFB0401001), the Natural Science Foundation of Heilongjiang Province
(YQ2019E003), the Postdoctoral Innovation Talent Support Project (BX20170097,
BX20180121), the China Postdoctoral Science Foundation (2017M620108 and
2018M641767), and JLUSTIRT (2019TD-33). M. Wang, Z. Cheng and X. Meng contributed
equally to this work.
15

References
[1]
[2]
C. W. Tang, S. A. VanSlyke, Appl. Phys. Lett. 1987, 51, 913.
a) M. A. Baldo, D. O'brien, Y. You, A. Shoustikov, S. Sibley, M. Thompson, S. R.
Forrest, Nature. 1998, 395, 151; b) Y. Ma, H. Zhang, J. Shen, C. Che, Synth. Met. 1998, 94,
245.
[3]
Thompson, S. Forrest, Phys. Rev. B. 1999, 60, 14422.
[4] a) H. Wang, L. Xie, Q. Peng, L. Meng, Y. Wang, Y. Yi, P. Wang, Adv. Mater. 2014,
a) B.Yang, Y.Ma, Scientia Sinica Chemica. 2013, 1457; b) M. Baldo, D. O’brien, M.
26, 5198; b) Q. Zhang, J. Li, K. Shizu, S. Huang, S. Hirata, H. Miyazaki, C. Adachi, J. Am.
Chem. Soc. 2012, 134, 14706; c) Z. Wu, J. Luo, N. Sun, L. Zhu, H. Sun, L. Yu, D. Yang, X.
Qiao, J. Chen, C. Yang, Adv. Funct. Mater. 2016, 26, 3306; d) W. Zeng, H. Y. Lai, W. K. Lee,
M. Jiao, Y. J. Shiu, C. Zhong, S. Gong, T. Zhou, G. Xie, M. Sarma, Adv. Mater. 2018, 30,
1704961; e) J. Guo, X. L. Li, H. Nie, W. Luo, S. Gan, S. Hu, R. Hu, A. Qin, Z. Zhao, S. J. Su,
Adv. Funct. Mater. 2017, 27, 1606458; f) G. Xie, X. Li, D. Chen, Z. Wang, X. Cai, D. Chen,
Y. Li, K. Liu, Y. Cao, S. J. Su, Adv. Mater. 2016, 28, 181.
[5]
a) W. Li, Y. Pan, R. Xiao, Q. Peng, S. Zhang, D. Ma, F. Li, F. Shen, Y. Wang, B.
Yang, Adv. Funct. Mater. 2014, 24, 1609; b) Y. Pan, W. Li, S. Zhang, L. Yao, C. Gu, H. Xu,
B. Yang, Y. Ma, Adv. Optical Mater. 2014, 2, 510; c) L. Yao, S. Zhang, R. Wang, W. Li, F.
Shen, B. Yang, Y. Ma, Angew. Chem., Int. Ed. 2014, 53, 2119; d) X. Qiu, S. Ying, C. Wang,
M. Hanif, Y. Xu, Y. Li, R. Zhao, D. Hu, D. Ma, Y. Ma, J. Mater. Chem. C 2019, 7, 592; e) S.
Zhang, L. Yao, Q. Peng, W. Li, Y. Pan, R. Xiao, Y. Gao, C. Gu, Z. Wang, P. Lu, Adv. Funct.
Mater. 2015, 25, 1755.
[6]
[7]
Z. R. Grabowski, K. Rotkiewicz, W. Rettig, Chem. Rev. 2003, 103, 3899.
S.-T. Zhang, X. Bai, X. Li, Q. Bai, M. Wang, H. Liu, P. Lu, S.-J. Su, B. Yang, Org.
Electron. 2019, 75, 105404.
16

[8]
a) B. Diaz de Grenu, D. Moreno, T. s. Torroba, A. Berg, J. Gunnars, T. Nilsson, R.
Nyman, M. Persson, J. Pettersson, I. Eklind, J. Am. Chem. Soc. 2014, 136, 4125; b) M.
Kloske, Z. Witkiewicz, Chemosphere. 2019; c) V. Pitschmann, Toxins. 2014, 6, 1761.
[9]
a) J. Y. Lee, Y. H. Lee, Y. G. Byun, Phosphorus, Sulfur Silicon Relat. Elem. 2012,
187, 641; b) Y. Kim, Y. J. Jang, S. V. Mulay, T. T. T. Nguyen, D. G. Churchill, Chem.– Eur.
J. 2017, 23, 7785; c) V. Kumar, H. Rana, Chem. Commun. 2015, 51, 16490; d) S. Royo, A. M.
Costero, M. Parra, S. Gil, R. Martínez‐Máñez, F. Sancenón, Chem.–Eur. J. 2011, 17, 6931;
e) J. Yao, Y. Fu, W. Xu, T. Fan, Y. Gao, Q. He, D. Zhu, H. Cao, J. Cheng, Anal. chem. 2016,
88, 2497; f) Y.-C. Cai, C. Li, Q.-H. Song, ACS sensors. 2017, 2, 834; g) H. Jiang, P. Wu, Y.
Zhang, Z. Jiao, W. Xu, X. Zhang, Y. Fu, Q. He, H. Cao, J. Cheng, Analytical Methods. 2017,
9, 1748; h) X. Zhou, Y. Zeng, C. Liyan, X. Wu, J. Yoon, Angew. Chem., Int. Ed. 2016, 55,
4729.
[10] L. Chen, D. Wu, J. Yoon, ACS sensors. 2017, 3, 27.
[11]
X. Li, Y. Lv, S. Chang, H. Liu, W. Mo, H. Ma, C. Zhou, S. Zhang, B. Yang, Anal.
chem. 2019, 91, 10927.
[12] Y. Gao, S. Zhang, Y. Pan, L. Yao, H. Liu, Y. Guo, Q. Gu, B. Yang, Y. Ma, Phys.
Chem. Chem. Phys. 2016, 18, 24176.
[13] W. Xuan, Y. Cao, J. Zhou, W. Wang, Chem. Commun. 2013, 49, 10474.
[14] a) S. Zhang, W. Li, L. Yao, Y. Pan, F. Shen, R. Xiao, B. Yang, Y. Ma, Chem.
Commun. 2013, 49, 11302; b) S. Zhang, Y. Dai, S. Luo, Y. Gao, N. Gao, K. Wang, B. Zou, B.
Yang, Y. Ma, Adv. Funct. Mater. 2017, 27, 1602276.
[15] Z. Mi, Z. Liu, C. Wang, Y. Liu, C. Zhou, D. Wang, X. Zhao, H. Zhou, Y. Zhang, C.
Chen, J. Polym. Sci., Part A: Poly Chem. 2018, 56, 2115.
[16]
R. L. Martin, J. Chem. Phys. 2003, 118, 4775.
[17] a) Y. Zhao, D. G. Truhlar, Theor. Chem. Acc. 2008, 120, 215; b) T. Lu, F. Chen, J.
Comput.
Chem.
2012,
17
33,
580.
b)

Gaussian 09, Revision D.01, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A
. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H. Nakatsuj
i, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Sonnenberg,
M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda,
O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery, Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J
. J. Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov, T. Keith, R. Kobayashi, J. Normand,
K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M.
Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts,
R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Marti
n, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg, S. Dapprich,
A. D. Daniels, O. Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski, and D. J. Fox, Gaussian,
Inc., Wallingford CT, 2013.
[18] a) Y. Shen, H. Liu, S. Zhang, Y. Gao, B. Li, Y. Yan, Y. Hu, L. Zhao, B. Yang, J.
Mater. Chem. C 2017, 5, 10061; b) H. Liu, L. Yao, B. Li, X. Chen, Y. Gao, S. Zhang, W. Li,
P. Lu, B. Yang, Y. Ma, Chem. Commun. 2016, 52, 7356; c) Y. Shen, Z. Zhang, H. Liu, Y.
Yan, S. Zhang, B. Yang, Y. Ma, J. Phys. Chem. C 2019.
[19] a) B. Huo, M. Du, A. Shen, M. Li, Y. Lai, X. Bai, A. Gong, Y. Yang, Anal. chem.
2019, 91, 10979; b) C. Sun, W. Xiong, W. Ye, Y. Zheng, R. Duan, Y. Che, J. Zhao, Anal.
chem. 2018, 90, 7131; c) S. Huang, Y. Wu, F. Zeng, L. Sun, S. Wu, J. Mater. Chem. C 2016,
4, 10105; d) Y.-C. Cai, C. Li, Q.-H. Song, J. Mater. Chem. C 2017, 5, 7337; e) V. V. Singh,
K. Kaufmann, J. Orozco, J. Li, M. Galarnyk, G. Arya, J. Wang, Chem. Commun. 2015, 51,
11190; f) M. S. J. Khan, Y.-W. Wang, M. O. Senge, Y. Peng, J. Hazard. Mater. 2018, 342, 10.
[20]
a) Y. Gao, H. Liu, S. Zhang, Q. Gu, Y. Shen, Y. Ge, B. Yang, Phys. Chem. Chem.
Phys. 2018, 20, 12129; b) H. Liu, Y. Dai, Y. Gao, H. Gao, L. Yao, S. Zhang, Z. Xie, K. Wang,
B. Zou, B. Yang, Adv. Optical Mater. 2018, 6, 1800085.
18

Author Statements
For
Deep Blue Electro-Fluorescence and Highly Efficient Chemical
Warfare Agent Sensor: Functional Versatility of Weak Coupling
Hybridized Locally Excited and Charge-Transfer Excited State
Dr. Shi-Tong Zhang and Prof. Hongwei Ma gave the conceptualization of this
work.
Man Wang, Dr. Xiangyu Meng, Ying Gao, Xinqi Yang, Dr. Haichao Liu and Dr.
Shi-Tong Zhang carried out the synthesis, the structure and property charaterization
and the OLED evaluation.
Zhiyong Cheng and Prof. Hongwei Ma carried out the DCP detection.
Dr. Haichao Liu, Dr. Shi-Tong Zhang, Prof. Hongwei Ma and Prof. Bing Yang
provided the funding.
Dr. Shi-Tong Zhang, Prof. Hongwei Ma and Prof. Bing Yang supervised the work.
All the authors wrote the paper.

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