A Highly Sensitive Bimodal Detection of Amine Vapours Based on Aggregation Induced Emission of 1,2-Dihydroquinoxaline Derivatives

Article abstract of DOI:10.1002/chem.201703253

The detection of food spoilage is a major concern in food safety as large amounts of food are transported globally. Direct analysis of food samples is often time-consuming and requires expensive analytical instrumentation. A much simpler and more cost-eff

Full text of DOI:10.1002/chem.201703253

A Journal of
Accepted Article
Title: A Highly Sensitive Bimodal Detection of Amine Vapours Based
on Aggregation Induced Emission of 1,2-Dihydroquinoxaline
Derivatives
Authors: Parvej Alam, Nelson Lik Ching Leung, Huifang Su, Zijie Qiu,
Ryan T. K. Kwok, Jacky W. Y. Lam, and Ben Zhong Tang
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Chem. Eur. J. 10.1002/chem.201703253
Link to VoR: http://dx.doi.org/10.1002/chem.201703253
Supported by

10.1002/chem.201703253
Chemistry - A European Journal
FULL PAPER
A Highly Sensitive Bimodal Detection of Amine Vapours Based
on Aggregation Induced Emission of 1,2-Dihydroquinoxaline
Derivatives
Parvej Alam+,[a, b] Nelson L. C. Leung+,[a, b] Huifang Su,[a, b] Zijie Qiu,[a, b] Ryan T. K. Kwok,[a, b] Jacky W.
Y. Lam,[a, b] and Ben Zhong Tang*[a, b, c]
Abstract: The detection of food spoilage is a major concern in food Introduction
safety as large amounts of food are transported globally. Direct
analysis of food samples is often time-consuming and requires
expensive analytical instrumentation. A much simpler and more cost-
effective method for monitoring food fermentation is to detect biogenic
amines generated as a by-product during food decomposition. In this
work, a series of 1,2-dihydroquinoxaline derivatives (DQs) with
aggregation-induced emission (AIE) characteristics were synthesized
and their protonated forms, i.e. H+DQs, can be utilized for the sensitive
detection of biogenic amines. For example, upon exposure to amine
vapours, deprotonation occurs which converts the red-coloured, non-
emissive H+DQ2 back to its yellow-coloured, fluorescent parent form.
The bimodal absorption and emission changes endow the system with
Over USD $220 billion worth of meat and seafood was shipped all
over the world in 2016.[1] Because of this, food safety and human
health are fundamentally important issues. Much research has
been done to ensure that the transported food remains fresh and
unspoiled,[2] and many methods have been designed to monitor
the safety of food products.[3] For example, time-temperature
indicators (TTI)[4] have been developed to show whether raw food
materials have been exposed to elevated temperatures for an
extended duration of time. Indeed, even the FDA has adopted
guidelines for the use of TTIs in US seafood products to ensure
food safety.[5] However, maintaining a chilled temperature only
slows down the enzymatic processes of food spoilage. In fact,
biogenic amine species, such as putrescine and cadaverine,
produced by microbes have been found in rainbow trout stored at
0 °C by the second day.[6] Biogenic amines have gained
recognition as good indicators of food freshness because they are
products of microbial fermentation.[7] In the process of food
spoilage, microbes break down amino acids via deaminization to
generate ammonia and decarboxylation to generate biogenic
amines such as cadaverine, putrescine, spermidine, spermine,
and others (Scheme 1). Biogenic amines not only signal the
freshness of the food, but also have adverse impact on human
health and physiological functions.[8] In fact, putrescine,
cadaverine, spermidine, and spermine can react with nitrites to
generate nitrosamines, a known carcinogen, in processes such
as meat curing.[9]
Thus, monitoring biogenic amines in food is important because
the chemical species and their by-products can have toxic effects
and they also signify food spoilage by microbes. Compared to
TTIs, a system that can detect the presence of biogenic amines
is a more direct method to monitor food safety and hygiene. One
obstacle for the detection of biogenic amines is that they have no
inherent characteristic absorption or emission. There are many
conventional techniques for amine detection[10] such as GC-
MS,[11] electrochemical systems,[12] array systems,[13] and
HPLC,[14] but many of these are more complex in nature.
The detection of biogenic amines can be simplified by exploiting
the chemical nature of the amines to induce photophysical
changes. For example, colourimetric change can be induced by
protonation/deprotonation[15] or through chemical reaction with
the probe.[16] Such a change allows easy visualization of the
presence of biogenic amines. A further improvement would be if
the system shows luminescence change upon exposure to amine
vapours as well.[17]
high sensitivity, capable of detecting ammonia vapour at
a
concentration of as low as 690 ppb. Taking advantage of this, H+DQ2
was successfully applied for the detection of food spoilage and was
established as a robust and cost effective technique to monitor food
safety.
[a]
[b]
Dr. P. Alam,+ N. L. C. Leung,+ Dr. Huifang Su, Z. Qiu, Dr. R. T. K.
Kwok, Dr. J. W. Y. Lam, Prof B. Z. Tang
HKUST Shenzhen Research Institute
No. 9 Yuexing 1st Rd, South Area, Hi-tech Park,
Nanshan, Shenzhen 518057, China
E-mail: tangbenz@ust.hk
Dr. P. Alam,+ N. L. C. Leung,+ Dr. Huifang Su, Z. Qiu, Dr. R. T. K.
Kwok, Dr. J. W. Y. Lam, Prof B. Z. Tang
Department of Chemistry
Division of Biomedical Engineering
Hong Kong Branch of Chinese National Engineering Research
Center for Tissue Restoration and Reconstruction
Institute for Advanced Study
Institute of Molecular Functional Materials and State Key Laboratory
of Molecular Neuroscience
The Hong Kong University of Science and Technology
Clear Water Bay, Kowloon, Hong Kong, China
Prof B. Z. Tang
Guangdong Innovative Research Team
SCUT-HKUST Joint Research Laboratory
State Key Laboratory of Luminescent Materials and Devices
South China University of Technology
[c]
[+]
Guangzhou 510640, China
P.A. and N.L.C.L. contributed equally to this work.
Supporting information, including NMR spectra, mass spectra,
absorption and emission spectra, AIE PL curves, absorption and
emission spectra changes after protonation of DQ2, Job plot of
DQ2, PL reversibility of H+DQ2, calculated average intensity plot
after exposure to ammonia vapour, photograph of H+DQ2 filter
paper strip sealed with salmon sample at room temperature and
2 °C, and photographs H+DQ2 filter paper strip sealed with white-leg
shrimp for this article can be found under <DOI>
This article is protected by copyright. All rights reserved.

10.1002/chem.201703253
Chemistry - A European Journal
FULL PAPER
Scheme 1. Schematic illustration of microbial proteolysis leading to the generation of ammonia and selected biogenic amines. Ammonia and biogenic amines
deprotonate red-coloured, non-emissive H+DQ2 to form yellow-coloured, fluorescent DQ2, allowing the detection of food spoilage. Structures of H+DQ2 and DQ2
and their photos taken under (left) daylight and (right) 365 nm UV irradiation.
Luminescent systems exhibit high sensitivity in response to
external stimuli. For example, amine detection showing
absorption and luminescence changes in solution with nanomolar
sensitivity has recently been reported.[18] Solution-based systems
are hard to use due to inherent logistic issues. Ideally, loading the
chemical sensor onto a solid support would drastically simplify the
methodology.[19] This allows the sensor to be sealed within the
packaging for a more direct monitoring of food freshness.
Unfortunately, conventional luminescent systems often
experience reduced emission intensity in the aggregate state due
to aggregation-caused quenching (ACQ).[20] In contrast, dye
molecules with aggregation-induced emission (AIE)[21]
characteristics are not affected by the ACQ effect and show
strong light emission in the solid state, making them ideal
candidates as sensors for detecting biogenic amines.[22] The bulky
nature of AIEgens may even enhance the sensitivity due to the
increase in intermolecular void spaces facilitating analyte species
to reach the chemical sensors.
amines released induces both colourimetric change and emission
turn-on of DQ2, allowing easy visualization for food safety
monitoring.
Results and Discussion
Characterization and Photophysical Properties
The DQs were synthesized by condensations of 1,2-diamino-4,5-
disubstituted benzenes (1) and benzil derivatives (2) followed by
reaction of the resulting intermediates (3) with n-butyl lithium (n-
BuLi) (Scheme 2). All the compounds were obtained in good to
moderate yields. Their chemical structures were confirmed by
standard spectroscopic techniques including NMR and HRMS
(Figure S1-S4 in the Electronic Supporting Information) with
satisfactory results. The reaction of 3 with n-BuLi converts an
imine (sp2 nitrogen, electron accepter) to an amine (sp3 nitrogen,
electron donor). This creates a donor (D)-acceptor (A) structure
in the DQs.
The optical properties of the DQ derivatives were studied in
organic solvents with different polarities at room temperature
(Figure S5-8). The DQs show an absorbance band in the range
of 380-420 nm. Their emission spectra changed with the solvent
because of the ICT effect stemming from their D-A structures. The
ICT features of the compounds were further investigated by DFT-
based calculations using Jaguar 9.4 in Schrödinger Materials
Science Suite 2016-4.[23] Results showed that the HOMO cloud
was localized mainly at the dihydropyrazine amine and the fused
phenyl ring while the LUMO cloud was spread over the
dihydropyrazine imine and other phenyl rings (Figure S9). As such,
ICT is likely to arise from this D-A structure. The calculated energy
gaps were in the range of 3.50-3.70 eV.
Herein, we report the synthesis of a series dihydroquinoxaline
derivatives (DQ1-4) with both AIE and intramolecular charge
transfer (ICT) features displaying strong solid-state emission.
Among the DQ derivatives, DQ2 was selected as a model for the
investigation due to its abundance (Scheme 1). DQ2 is yellow in
colour and after protonation to form H+DQ2, its colour visibly
changes to red. In addition, H+DQ2 is non-emissive but emission
is recovered after deprotonation. This provides both
a
colourimetric change and emission turn-on feature for sensitive
amine sensing with a detection limit of 690 ppb for ammonia (NH3).
In particular, H+DQ2 was responsive even to biogenic amines
such as putrescine, cadaverine and spermidine. Because of its
AIE nature, the probe can be loaded onto a solid substrate and
sealed in a container with food. As the food ferments, biogenic
This article is protected by copyright. All rights reserved.

10.1002/chem.201703253
Chemistry - A European Journal
FULL PAPER
Figure 1. (A) PL spectra of DQ2 in MeOH/H2O mixtures with different water
fractions (fw). Concentration: 10 μM; λex = 400 nm. (B) Plot of PL intensity and
emission maximum versus the composition of the MeOH/H2O mixtures of DQ2.
(C) Fluorescent image of DQ2 in MeOH/H2O mixtures with water fractions from
0 to 90% (left to right) taken under 365 nm UV irradiation.
To verify these hypotheses, DQ2 was first reacted with
trifluoroacetic acid (TFA) to generate H+DQ2, the protonated form
of DQ2 (Scheme 1). The optical properties of both DQ2 and
H+DQ2 were then investigated. The absorption spectrum of DQ2
in DCM showed two peaks at 270 nm and 392 nm, which moved
to 338 nm and 478 nm, upon the addition of TFA (Figure S17). PL
analysis showed a similar result where the emission maximum
moved from 530 nm to 560 nm upon molecular protonation
(Figure S18). The ICT effect of the molecular was strengthened
upon protonation, which might account for the red-shift in the
absorption and emission. It should be noted that alongside the
wavelength shift, the emission intensity is also significantly
quenched. In addition, the absorption spectrum of H+DQ2
significantly overlap with its PL spectrum. Thus, the non-emissive
nature of H+DQ2 may be explained as a combination of self-
absorption and the photoinduced electron transfer effect (Figure
S18). The addition of base such as triethylamine (TEA) restores
of the emission peak at 530 nm.
The stoichiometric ratio between DQ2 and TFA was determined
to be 1:1 by UV-VIS titration followed by a Job plot (Figure S19).
The protonation process was also monitored using NMR
spectroscopy: after the addition of TFA the resonance peak at δ
6.18 ppm shifted to 6.50 ppm, which moved to the original position
after deprotonation with TEA (Figure S17). These experiments
showed the protonation and deprotonation processes are
reversible in nature.
Scheme 2. Top: Synthetic route for the dihydroquinoxaline (DQ) derivatives.
Bottom: Fluorescent photo of the DQs taken under 365 nm UV excitation.
The AIE properties of the DQs were further studied in
methanol/water (Figure 1, S10, S13 and S15) and THF/water
mixtures (Figure S11, S12, S14 and S16). With an increase in
water fraction from 0 to 60% in methanol/water mixture, the
emission decreased alongside a bathochromic shift in peak
maximum from 573 nm to 585 nm (Figure 1). This phenomenon
is attributed to the enhancement of the ICT effect by the increase
in solvent polarity. However, at fw = 70%, an immediate 28-fold
emission enhancement was observed with a hypsochromic shift
in the PL spectrum. Further addition of water strengthens the
blue-shifted emission. The PL enhancement at fw ≥ 70% was
recognized as a signal for the activation of the AIE phenomenon
due to the formation of aggregates.[21] Similar observations were
found upon the addition of water to the THF solution of DQ2
(Figure S12). These results clearly demonstrate that DQ2 exhibits
both typical AIE and ICT features. The emission enhancement
after aggregate formation was due to the predominance of the AIE
effect over the ICT effect. Analogous AIE behaviour was observed
for other DQs (Figure S10-16).
We prepared H+DQ2-loaded filter paper to investigate the
system’s ability to detect amine vapours in the solid state.
Whatman glass microfibre filters were chosen as a substrate for
their porosity and we were careful to only deposit 100 µL of a 100
µM DCM solution to ensure accuracy and reproducibility. Its
reversibility was tested by exposing alternatively to NH3 and TFA
for multiple cycles (Figure S20). No emission was initially
observed from the filter paper but a turn-on signal appears after
Protonation-Induced Photophysical Changes
Due to the D-A structure of the DQs, we anticipated that their
optical properties would change when their imine unit is
protonated. On the other hand, deprotonation of the
aforementioned nitrogen by amine vapours may restore the
original properties of the molecules.
This article is protected by copyright. All rights reserved.

10.1002/chem.201703253
Chemistry - A European Journal
FULL PAPER
Figure 2. (A) Top: PL spectra of H+DQ2-doped filter paper strips after exposure
to 0 ppm, 15 ppm, 40 ppm, 58 ppm, 85 ppm, and 120 ppm of ammonia vapour
for 5 min. λex = 365 nm. Below: Photographs of the H+DQ2-doped filter paper
strips after exposure to ammonia vapour taken under 365 nm UV excitation. (B)
PL turn-on response of H+DQ2-loaded filter paper strip in the presence of
various amine vapours. H+DQ2 was exposed to aqueous or methanolic amine
solutions (0.08 M) for 40 s. Biogenic amines and ammonia coloured in red, other
amine species coloured grey. Ammonia was prepared as an aqueous solution,
while other amine species were prepared as methanolic solutions. Abbreviation:
DEA = diethylamine; TMA = trimethylamine; TEA = triethylamine; MeBzA =
methylbenzylamine; 1,2 DiPhA = 1,2-diphenylamine.
fuming with ammonia gas. The emission faded again after
exposure to TFA vapour. Such emission turn-on and turn-off can
be repeated for many cycles with minimal fatigue, demonstrating
the high reversibility and reliability of the present system.
To investigate the turn-on sensitivity, the H+DQ2-loaded strips
were exposed to various concentrations of NH3 vapour. 5 mL of
aqueous NH3 solutions with various concentrations were placed
in 100 mL bottles and sealed overnight to reach equilibrium. The
NH3 vapour concentrations were measured using Gastec detector
tubes and the vapours were exposed to the H+DQ2-loaded strips.
The turn-on emissions were measured using PL spectroscopy
(Figure 2A). The strips can show varying PL intensities due to
inherent microscopic differences of the substrate. As such,
instead of using a spectrophotometer to measure a single location,
the average greyscale values of the strips were also calculated
using MATLAB to represent the overall brightness of the
fluorescent images.[24] These values were then used to determine
the limit of detection (LOD). First, a regression line was obtained
by plotting the greyscale value versus the amine concentration.
The LOD was calculated to be 690 ppb by the equation 3σ/m,
where σ is the standard deviation of the blank measurement and
m is the slope of the regression line. (Figure S21).
Figure 3. (A) H+DQ2 sensor sealed with salmon sashimi in room temperature.
After 24 hours, emission turn-on can be observed. (B) H+DQ2 sensor in sealed
packages of yellowfin seabream, after 18 hours, emission turn-on can be
observed. Inset: magnified photo of the sealed sensor.
H+DQ2-loaded filter papers were then placed on top of the open
glass vials of the amine solutions for 40 s. After exposure, the
fluorescence of the filter papers was measured. The filter paper
was then exposed to TFA vapour to re-protonate DQ2. This
finishes one detection cycle. A total of three detection cycles were
performed for each amine solution and the PL responses were
graphed in Figure 2B. The filter paper strips showed a turn-on
response within 40 seconds after exposure to ammonia,
cadaverine, putrescine, spermidine along with hydrazine, TEA,
DEA, TMA and piperidine. Less volatile amine species such as
spermine, piperazine, MeBzA, aniline, and 1,2 DiPhA, induced
smaller emission changes.
Fluorescence Detection of Inorganic and Biogenic Amines
The fluorescence turn-on capability of the H+DQ2-loaded filter
paper strip was further investigated using different amine vapours.
10 mL of 0.08 M methanolic solutions of hydrazine, diethylamine
(DEA), trimethylamine (TMA), triethylamine (TEA), piperidine,
These experiments revealed the potentiality of H+DQ2-loaded
filter paper as a turn-on fluorescence sensor for volatile amines
including important biogenic amines.
Detection of Amines from Food Spoilage
Based on the capability of H+DQ2-loaded filter paper for detecting
biogenic amines, we aimed to test the system’s response to
vapour biogenic amines generated in-situ due to fermentation.
Fresh samples of salmon sashimi, yellowfin seabream, and white-
leg shrimp were purchased from a local supermarket. To first
examine if the test strip would show any response, three sealed
piperazine,
methylbenzylamine
(MeBzA),
aniline,
1,2-
diphenylamine (1,2 DiPhA), cadaverine, putrescine, spermidine,
and spermine were prepared in 25 mL glass vials. A 10 mL of
0.08M aqueous solution of ammonia was also prepared. The
This article is protected by copyright. All rights reserved.

10.1002/chem.201703253
Chemistry - A European Journal
FULL PAPER
4,5-Dimethylbenzene-1,2-diamine,
tolylethane-1,2-dione,
benzene-1,2-diamine,
1,2-bis(4-bromophenyl)ethane-1,2-dione
1,2-di-p-
and
Petri dishes with test strips containing (i) no sample and samples
of salmon sashimi kept at (ii) room temperature and (iii) 2 °C were
prepared (Figure S22). After 48 h, only the test strip sealed with
the sashimi kept at room temperature showed colour and
emission change. Its original red colour changed to yellow and
bright emission was observed under UV irradiation. Further
testing of the strips was performed by sealing the strips with
varying numbers of fresh salmon sashimi at room temperature
(Figure 3A). After 24 h, the test strip sealed with three pieces of
salmon sashimi was somewhat emissive, although no apparent
colour change was observed. After 48 h, all test strips showed
both visible colour change and emission turn-on. This highlights
the higher sensitivity of fluorescence technique over colourimetric
change for detecting biogenic amines. Fluorescence turn-on can
be observed before visible colourimetric change. The threshold
for fluorescence turn-on can be reached faster in the sample with
a larger sample size, leading to visible emission after 24 h.
Apparent colour change indicates that active fermentation has
taken place.
ethanol were purchased from the J&K Company Ltd. All spectroscopic
grade solvents: such as dichloromethane (DCM), methanol (MeOH),
toluene, 1,4-dioxane, ethyl acetate, chloroform (CHCl3), tetrahydrofuran
(THF), acetonitrile (ACN), dimethylformamide were procured from the
Merck Company. Whatman glass microfibre filter paper was used for the
H+DQ2-loaded filter paper strips.
General Syntheses of 2,3-diphenylquinoxaline derivatives (3)
Intermediate 3 was synthesized based on reported works[25] with the
synthetic route shown in Scheme 2. To a stirred solution of 1,2-diamino-
4,5-disubstituted benzenes (1, 18.5 mmol) in ethanol (50 mL), benzil
derivatives (2, 18.5 mmol) and a catalytic amount of acetic acid were
added. The mixture was refluxed for 5 h. After cooling to room temperature
and solvent evaporation, the crude product was purified by recrystallization
from a mixture of DCM and ethanol (1:5), generating 3 in 70-80% yield.
General Syntheses of 1,2-dihydroquinoxaline (DQ) derivatives
To further explore the capability and ease of use of the test strips,
we attached them to plastic wrap used to reseal the package of
yellowfin seabream (Figure 3B) and white-leg shrimp (Figure S23).
After keeping the samples at room temperature for 18 h,
absorption and fluorescence changes were observed in both
samples, which were indicative of microbial fermentation. The
strips are easy to produce providing simple and sensitive
monitoring of food fermentation.
An oven dried round bottom flask sealed with rubber stopper was charged
3 (1.6 mmol) followed by addition of dry THF (30 mL). The reaction mixture
was cooled at 0 °C, and n-butyl lithium (1.2ꢀmmol, 2.5ꢀM in hexane) was
added dropwise to the mixture using a syringe. After complete addition,
the reaction mixture was stirred at room temperature for 3 h. Then, the
mixture was hydrolysed by addition of an excess amount of water. The
reaction mixture was extracted using CH2Cl2 and dried over sodium
sulphate. The solvent was evaporated under reduced pressure to afford
the crude product which was further purified by column chromatography
using ethyl acetate/hexane mixture as eluent to give a solid product in 55-
70% yield.
Conclusions
Characterization
In this work, we developed a series of DQs with both AIE and ICT
features. DQs show absorption and emission changes upon
protonation. Utilizing this bimodal variation, DQs were used as
sensors for sensitive detection of biogenic amine vapours such as
cadaverine, putrescine and spermidine. The detection limit was
found to be 690 ppb for NH3, which was low enough to detect
amines generated from food spoilage. An easily prepared
portable sensor was developed by using filter paper as a solid
support to detect food spoilage. The sensor displays changes in
its optical properties in response to amines produced due to food
spoilage: luminescent turn-on can give the earliest signal for the
presence of fermentation, and colourimetric changes allow easy
visualization with just the naked eye. It is noteworthy that DQ2
can easily enter HeLa cells and stain lipid droplets with high
brightness and specificity (Figure S24). MTT assay showed that
even at concentration of up to 10 μM, DQ2 showed minimal
cytotoxicity to cells (Figure S25). Its low cytotoxicity is particularly
important as a food safety monitoring agent. Thus, new materials
synthesized in this study are expected to find an array of
advanced applications.
1H and 13C spectra were recorded on
spectrometer using CDCl3 and MeOD solvents. UV-VIS absorption spectra
were recorded on PerkinElmer UV/VIS Lambda 365. The
photoluminescence (PL) spectra were recorded on Fluorolog®-3
spectrofluorometer. High-resolution mass spectroscopy (HRMS) were
carried out on a GCT premier CAB048 mass spectrophotometer operating
in MALDI-TOF mode. All the reactions were performed under nitrogen
atmosphere and the progress of the reaction was monitored using thin-
layer chromatography (TLC) plates pre-coated with 0.20 mm silica gel.
a Bruker ARX 400 NMR
a
a
DQ1: 1H NMR (400 MHz, CDCl3) δ (ppm) 7.56-7.50 (m, 2H), 7.39-7.26 (m,
6H), 7.21 (ddd, J = 8.2, 6.3, 2.2 Hz, 3H), 6.24 (s, 1H), 3.75 (s, 1H), 2.40-
2.26 (m, 1H), 2.18 (d, J = 10.1 Hz, 6H), 2.03-1.81 (m, 1H), 1.71 (m, 1H),
1.36-1.09 (m, 3H), 0.77 (t, J = 7.1 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ
(ppm) 161.60, 145.40, 138.78, 137.73, 133.61, 129.39, 129.23, 128.92,
128.82, 128.17, 127.75, 127.73, 126.15, 125.73, 113.74, 61.59, 37.75,
26.65, 22.98, 19.84, 18.83, 13.85. MS (MALDI-TOF): calcd. for M+ = m/z
368.2252; found: m/z 368.2255.
DQ2: 1H NMR (400 MHz, CDCl3) δ (ppm) 7.39 (d, J = 8.2 Hz, 2H), 7.23 (d,
J = 8.2 Hz, 2H), 7.14 (d, J = 8.8 Hz, 3H), 7.00 (d, J = 8.0 Hz, 2H), 6.19 (s,
1H), 3.66 (s, 1H), 2.31 (d, J = 14.1 Hz, 6H), 2.15 (d, J = 11.4 Hz, 6H), 2.01-
1.81 (m, 1H), 1.76-1.53 (m, 1H), 1.34-1.04 (m, 3H), 0.75 (t, J = 7.0 Hz,
3H); 13C NMR (101 MHz, CDCl3) δ (ppm) 160.98, 142.19, 138.10, 136.79,
136.72, 135.41, 133.00, 128.93, 128.79, 128.47, 127.76, 127.50, 125.35,
124.89, 112.98, 60.63, 37.47, 26.06, 22.40, 20.64, 20.43, 19.16, 18.16,
13.25. MS (MALDI-TOF): calcd. for (M+H)+ = m/z 397.2644; found: m/z
397.2614.
Experimental Section
Materials
This article is protected by copyright. All rights reserved.

10.1002/chem.201703253
Chemistry - A European Journal
FULL PAPER
1
DQ3: H NMR (400 MHz, MeOD) δ (ppm) 7.35 (d, J = 8.3 Hz, 2H), 7.18
52, 13987-13990; c) P. S. Taoukis, T. P. Labuza, J. Food Sci. 1989, 54,
783-788.
(dd, J = 11.2, 4.8 Hz, 3H), 7.11 (d, J = 8.1 Hz, 2H), 7.04 (d, J = 8.1 Hz, 2H),
6.91 (td, J = 7.8, 1.4 Hz, 1H), 6.54 (td, J = 7.6, 1.2 Hz, 1H), 6.47 (dd, J =
7.9, 1.1 Hz, 1H), 3.30 (s, 1H), 2.28 (d, J = 3.5 Hz, 6H), 2.20 (m, 1H), 2.04
[5]
FDA, Fish and Fishery Products Hazards and Controls Guidance,
https://www.fda.gov/downloads/Food/GuidanceRegulation/UCM251970
.pdf, accessed: May 2017.
(m,1H), 1.77-1.58 (m, 1H), 1.31-1.02 (m, 2H), 0.72 (t, J = 7.1 Hz, 1H); 13
C
NMR (101 MHz, CDCl3) δ (ppm) 162.01, 142.01, 138.37, 136.90, 135.35,
135.19, 130.59, 128.97, 128.22, 127.82, 127.62, 127.57, 125.42, 117.07,
111.72, 60.68, 37.50, 26.06, 22.39, 20.66, 20.43, 13.26. MS (MALDI-
TOF): calcd. for (M+H)+ = m/z 369.2331; found: m/z 369.2321.
[6]
[7]
A. A. Dawood, J. Karkalas, R. N. Roy, C. S. Williams, Food Chem. 1988,
27, 33-45.
a) C. Ruiz-Capillas, F. Jiménez-Colmenero, Crit. Rev. Food Sci. Nutr.
2005, 44, 489-599; b) I. A. Bulushi, S. Poole, H. C. Deeth, G. A. Dykes,
Crit. Rev. Food Sci. Nutr. 2009, 49, 369-377; c) M. T. Veciana-Nogués,
A. Mariné-Font, M. C. Vidal-Carou, J. Agric. Food Chem. 1997, 45, 2036-
2041; d) F. a. A. O. o. t. U. Nations, W. H. Organization, Joint FAO/WHO
expert meeting on the public health risks of histamine and other biogenic
amines from fish and fishery products: meeting report, World Health
Organization, Geneva, 2013.
DQ4: 1H NMR (400 MHz, CDCl3) δ (ppm) 7.64-7.53 (m, 8H), 7.46 (d, J =
4.4 Hz, 4H), 7.45-7.38 (m, 5H), 7.34 (q, J = 7.2 Hz, 2H), 7.02 (td, J = 7.7,
1.4 Hz, 1H), 6.73 (td, J = 7.6, 1.2 Hz, 1H), 6.43 (dd, J = 7.9, 1.1 Hz, 1H),
3.91 (s, 1H), 2.54-2.38 (m, 1H), 2.11-1.95 (m, 1H), 1.85-1.69 (m, 1H), 1.27
(m, 3H), 0.78 (t, J = 7.1 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ (ppm)
161.96, 144.29, 141.68, 140.58, 140.42, 140.25, 137.40, 135.87, 131.22,
130.36, 129.16, 128.84, 128.78, 128.73, 128.47, 127.62, 127.53, 127.02,
127.01, 126.61, 126.49, 117.95, 112.50, 61.44, 38.11, 26.75, 23.02, 13.89.
MS (MALDI-TOF): calcd. for (M+H)+ = m/z 493.2644; found: m/z 493.2632.
[8]
[9]
A. R. Shalaby, Food Res. Int. 1996, 29, 675-690.
a) J. J. Warthesen, R. A. Scanlan, D. D. Bills, L. M. Libbey, J. Agric. Food
Chem. 1975, 23, 898-902; b) G. Drabik-Markiewicz, B. Dejaegher, E. De
Mey, T. Kowalska, H. Paelinck, Y. Vander Heyden, Food Chem. 2011,
126, 1539-1545.
[10] A. Önal, Food Chem. 2007, 103, 1475-1486.
Computational Methods
[11] a) J. O. Fernandes, I. C. Judas, M. B. Oliveira, I. M. P. L. V. O. Ferreira,
M. A. Ferreira, Chromatographia 2001, 53, S327-S331; b) S. C. Cunha,
M. A. Faria, J. O. Fernandes, J. Agric. Food Chem. 2011, 59, 8742-8753.
[12] L. K. Fiddes, J. Chang, N. Yan, Sensor Actuat. B-Chem. 2014, 202,
1298-1304.
The DFT calculations were performed using Jaguar 9.4 in Schrödinger
Materials Science Suite 2016-4.[23] B3LYP functional was used to optimize
the structures of DQ1-4 using the 6-31G** basis set.
[13] a) G. A. Sotzing, J. N. Phend, R. H. Grubbs, N. S. Lewis, Chem. Mater.
2000, 12, 593-595; b) J. Lange, C. Wittmann, Anal. Bioanal. Chem. 2002,
372, 276-283.
Acknowledgements
[14] a) N. Innocente, M. Biasutti, M. Padovese, S. Moret, Food Chem. 2007,
101, 1285-1289; b) S. Gómez-Alonso, I. Hermosín-Gutiérrez, E. García-
Romero, J. Agric. Food Chem. 2007, 55, 608-613.
This work was partially supported by the National Basic Research
Program of China (973 Program, 2013CB834701 and
2013CB834702), the University Grants Committee of Hong Kong
(AoE/P-03/08), the Research Grants Council of Hong Kong
(16305015, 16308016, and N_HKUST604/14), the Innovation
and Technology Commission (ITC-CNERC14SC01 and
ITCPD/17-9). We thank the support of the Guangdong Innovative
Research Team Program (201101C0105067115) and the
[15] N. A. Rakow, A. Sen, M. C. Janzen, J. B. Ponder, K. S. Suslick, Angew.
Chem. Int. Ed. 2005, 44, 4528-4532.
[16] V. Valderrey, A. Bonasera, S. Fredrich, S. Hecht, Angew. Chem. Int. Ed.
2017, 56, 1914-1918.
[17] A. Mallick, B. Garai, M. A. Addicoat, P. S. Petkov, T. Heine, R. Banerjee,
Chem. Sci. 2015, 6, 1420-1425.
[18] S. Mallick, F. Chandra, A. L. Koner, Analyst 2016, 141, 827-831.
[19] A. Sandeep, V. K. Praveen, K. K. Kartha, V. Karunakaran, A. Ajayaghosh,
Chem. Sci. 2016, 7, 4460-4467.
Science
and
Technology
Plan
of
Shenzhen
(JCYJ201602292056014di82).
[20] X. Ma, R. Sun, J. Cheng, J. Liu, F. Gou, H. Xiang, X. Zhou, J. Chem.
Educ. 2016, 93, 345-350.
[21] J. Mei, N. L. C. Leung, R. T. K. Kwok, J. W. Y. Lam, B. Z. Tang, Chem.
Rev. 2015, 115, 11718-11940.
Keywords: aggregation-induced emission • amines •
colourimetric • fluorescence • food safety
[22] M. Gao, S. Li, Y. Lin, Y. Geng, X. Ling, L. Wang, A. Qin, B. Z. Tang, ACS
Sensors 2016, 1, 179-184.
[1]
a) I. T. Centre, Trade Map - List of importers for the selected product in
2016 (Fish and crustaceans, molluscs and other aquatic invertebrates),
http://www.trademap.org/tradestat/Country_SelProduct.aspx?nvpm=1|||
||03|||2|1|1|1|1||2|1|, accessed: May 2017; b) I. T. Centre, Trade Map -
List of importers for the selected product in 2016 (Meat and edible meat
offal),
[23] a) A. D. Bochevarov, E. Harder, T. F. Hughes, J. R. Greenwood, D. A.
Braden, D. M. Philipp, D. Rinaldo, M. D. Halls, J. Zhang, R. A. Friesner,
Int. J. Quantum Chem. 2013, 113, 2110-2142; b) in Jaguar, Schrödinger,
LLC, New York, NY, 2016.
[24] a) C. A. Poynton, Vol. 3299, 1998, pp. 232-249; b) J. van Rheenen, M.
Langeslag, K. Jalink, Biophys. J. 2004, 86, 2517-2529; c) S. M. Sadeghi,
A. Hatef, A. Nejat, Q. Campbell, M. Meunier, J. Appl. Phys. 2014, 115,
134315; d) C. Gui, E. Zhao, R. T. K. Kwok, A. C. S. Leung, J. W. Y. Lam,
M. Jiang, H. Deng, Y. Cai, W. Zhang, H. Su, B. Z. Tang, Chem. Sci. 2017,
8, 1822-1830.
http://www.trademap.org/tradestat/Country_SelProduct.aspx?nvpm=1|||
||02|||2|1|1|1|1||2|1|, accessed: May 2017.
[2]
a) M. Friedman, J. Agric. Food Chem. 1996, 44, 631-653; b) L. Gram, L.
Ravn, M. Rasch, J. B. Bruhn, A. B. Christensen, M. Givskov, Int. J. Food
Microbiol. 2002, 78, 79-97.
[25] a) C. Xie, Z. Zhang, B. Yang, G. Song, H. Gao, L. Wen, C. Ma,
Tetrahedron 2015, 71, 1831-1837; b) T. Hirayama, S. Yamasaki, H.
Ameku, T. Ishi-i, T. Thiemann, S. Mataka, Dyes Pigm. 2005, 67, 105-110.
[3]
[4]
a) Y. Wang, T. V. Duncan, Curr. Opin. Biotechnol. 2017, 44, 74-86; b) M.
Akhoundian, A. Rüter, S. Shinde, Sensors 2017, 17, 645.
a) M. Ozdemir, J. D. Floros, Crit. Rev. Food Sci. Nutr. 2004, 44, 185-193;
b) A. Mills, D. Hawthorne, A. Graham, K. Lawrie, Chem. Commun. 2016,
This article is protected by copyright. All rights reserved.

10.1002/chem.201703253
Chemistry - A European Journal
FULL PAPER
Layout 1:
FULL PAPER
Detecting biogenic amines: A new
family of AIEgens provide a platform
for simple, sensitive, bimodal
Parvej Alam, Nelson L. C. Leung,
Huifang Su, Zijie Qiu, Ryan T. K. Kwok,
Jacky W. Y. Lam, and Ben Zhong Tang*
detection of biogenic amine vapours
produced by food fermentation. The
colourimetric change allows for easy
naked eye visualization, while
fluorescence turn-on provides
enhanced sensitivity for earlier
indication, with a detection limit of 690
ppb for ammonia.
Page No. – Page No.
A Highly Sensitive Bimodal Detection
of Amine Vapours Based on
Aggregation Induced Emission of 1,2-
Dihydroquinoxaline Derivatives
This article is protected by copyright. All rights reserved.