Double Solvent Sensing Method for Improving Sensitivity and Accuracy of Hg(II) Detection Based on Different Signal Transduction of a Tetrazine-Functionalized Pillared Metal-Organic Framework

Article abstract of DOI:10.1021/acs.inorgchem.7b01155

To design a robust, π-conjugated, low-cost, and easy to synthesize metal-organic framework (MOF) for cation sensing by the photoluminescence (PL) method, 4,4′-oxybis(benzoic acid) (H₂OBA) has been used in combination with 3,6-di(pyridin-4-yl)-1

Full text of DOI:10.1021/acs.inorgchem.7b01155

Article
pubs.acs.org/IC
Double Solvent Sensing Method for Improving Sensitivity and
Accuracy of Hg(II) Detection Based on Different Signal Transduction
of a Tetrazine-Functionalized Pillared Metal−Organic Framework
Sayed Ali Akbar Razavi,† Mohammad Yaser Masoomi,† and Ali Morsali*
Department of Chemistry, Faculty of Sciences, Tarbiat Modares University, P.O. Box 14117-13116, Tehran, Islamic Republic of Iran
S
* Supporting Information
ABSTRACT: To design a robust, π-conjugated, low-cost, and easy to
synthesize metal−organic framework (MOF) for cation sensing by the
photoluminescence (PL) method, 4,4′-oxybis(benzoic acid) (H2OBA) has
been used in combination with 3,6-di(pyridin-4-yl)-1,2,4,5-tetrazine
(DPT) as a tetrazine-functionalized spacer to construct [Zn(OBA)-
(DPT)0.5]·DMF (TMU-34(-2H)). The tetrazine motif is a π-conjugated,
water-soluble/stable fluorophore with relatively weak σ-donating Lewis
basic sites. These characteristics of tetrazine make TMU-34(-2H) a good
candidate for cation sensing. Because of hydrogen bonding between
tetrazine moieties and water molecules, TMU-34(-2H) shows different PL
emissions in water and acetonitrile. Cation sensing in these two solvents
revealed that TMU-34(-2H) can selectively detect Hg2+ in water (by 243%
enhancement) and in acetonitrile (by 90% quenching). The contribution
of electron-donating/accepting characteristics along with solvation effects
on secondary interactions of the tetrazine motifs inside the TMU-34(-2H) framework results in different signal transductions.
Improved sensitivity and accuracy of detection were obtained using the double solvent sensing method (DSSM), in which
different signal transductions of TMU-34(-2H) in water and acetonitrile were combined simultaneously to construct a double
solvent sensing curve and formulate a sensitivity factor. Calculation of sensitivity factors for all of the tested cations demonstrated
that it is possible to detect Hg2+ by DSSM with ultrahigh sensitivity. Such a tremendous distinction in the Hg2+ sensitivity factor
is visualizable in the double solvent sensing curve. Thus, by application of DSSM instead of one-dimensional sensing, the
interfering effects of other cations are completely eliminated and the sensitivity toward Hg(II) is highly improved. Strong
interactions between Hg2+ and the nitrogen atoms of the tetrazine groups along with easy accessibility of Hg2+ to the tetrazine
groups lead to a shorter response time (15 s) in comparison with other MOF-based Hg2+ sensors.
applications because of their unique characteristics, especially
for porosity and tunable chemical functionalization. The PL
behaviors of MOFs originate from the conjugated organic
linkers and/or metal ions or clusters as well as some other
factors like host−guest/solvent interactions, hydrogen bonding,
and π−π interactions in their crystalline structures. In linker-
based luminescence behavior, π-extended conjugated MOFs
have excellent signal transduction. Moreover, immobilization of
functional groups as fluorophores has a significant effect on the
secondary interactions and PL behavior of MOFs.17,18
INTRODUCTION
■
Sensing of Hg2+ is of special importance because this ion is the
most stable inorganic form of mercury with good solubility in
water that, even at low concentrations, can cause many serious
problems like digestive, kidney, and specially neurological
complications for humans.1,2Release of Hg2+ in nature through
industrial waste has dramatically increased. Considering the
toxicity and widespread release of Hg2+, a fast, facile, cheap, and
effective method to detect Hg2+ is needed.3,4
Traditional detection methods for Hg2+, like gas chromatog-
raphy, ultrasensitive stripping voltammetry, atomic emission/
absorption spectrometry, inductively coupled plasma mass
spectrometry, cold-vapor atomic fluorescence spectrometry,
and anodic stripping voltammetry are quite sensitive and
effective, but they are very expensive and slow.5−15
Recently, photoluminescence (PL) methods have drawn a lot
of interest to themselves for sensing applications because these
methods are very selective, sensitive, low-cost, and visualizable
while offering rapid response times and real-time monitoring.16
Metal−organic frameworks (MOFs) are a class of crystalline
porous materials that have received a lot of attention in sensing
Many studies of Hg2+ detection have encountered challenges
like long response times, the poor dispersion of MOFs in water,
framework collapsr, and noticeable effects of other cations on
the PL spectra.11,19−28 These problems lead to lower sensitivity,
precision, and accuracy of detection.
The 1,2,4,5-tetrazine motif shows unique characteristics like
reversible redox activity, significant color change, and low-lying
π* orbitals that make it usable for applications in the fields of
Received: May 6, 2017
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.7b01155
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Scheme 1. Structure of TMU-34(-2H) and Tetrazine-Functionalized Pores
mg of TMU-34(-2H) powder into 4.00 mL of water or 4.00 mL of
acetonitrile. (III) Cation-incorporated TMU-34(-2H) emulsions were
prepared by adding 1−5 mL of target analyte solution (1.0 × 10−3 M)
into the emulsions of step (II) in an incremental fashion to achieve
target analyte concentrations of (2−10) × 10−4 M. (IV) The mixed
solutions prepared in step (III) were shaken for a few seconds. After
these steps, the fluorescence properties of all cations incorporated in
TMU-34(-2H) emulsion solutions were measured.
sensors, electrochemistry, and conducive materials, but its
applications in supramolecular chemistry are rare.29 Here, by
applying the electron-donating/accepting characteristics of
1,2,4,5-tetrazine, we suggest a strategy for ultrahigh-sensitivity
sensing of Hg(II). Also, secondary interactions of the tetrazine
group are completely discussed.
The sensitivity factor (S) is formulated as follows:
EXPERIMENTAL SECTION
■
Rf − Ri
Materials and Characterization. All of the required chemicals
were obtained from commercial suppliers and used without further
purification unless otherwise stated.
S =
Ri
Ultrasonic generation was carried out in a SONICA-2200 EP
ultrasonic bath (frequency of 40 kHz). Powder X-ray diffraction
(PXRD) measurements were performed using a Philips X’pert
diffractometer with monochromatized Cu Kα radiation. Elemental
analyses were carried out on a CHNS Thermo Scientific Flash 2000
elemental analyzer. Sorption studies were performed with a TriStar II
3020 surface area analyzer from Micromeretics Instrument Corpo-
ration using N2 at 77 K. The samples were characterized using energy-
dispersive X-ray spectroscopy (EDAX) on a CamScan MV2300
instrument with gold coating. Thermal behavior was measured with a
PL-STA 1500 apparatus at a heating rate of 10 °C min−1 in a static
atmosphere of argon.
where Ri and Rf are the initial sensor response and the response of the
sensor in the presence of the desired cation, respectively. This
response is defined as the ratio of the intensities of the TMU-34(-2H)
PL emission peaks in water and acetonitrile.
The quenching or enhancement effect was calculated using the
Stern−Volmer equation:
I0
I
= 1 + KSV[M]
where I0 and I are the luminescence intensities of the suspension of
TMU-34(-2H) without and with the addition of cation, respectively,
[M] is the molar concentration of the cation, and KSV is the Stern−
Volmer quenching constant.26
Synthesis. 3,6-Di(pyridin-4-yl)-1,2,4,5-tetrazine (DPT). The DPT
spacer was synthesized according to reported procedures (Scheme
S1).30−32
RESULTS AND DISCUSSION
[Zn(OBA)(DPT)0.5]·DMF (TMU-34(-2H)). A powdered sample of
TMU-34(-2H) was synthesized by mixing Zn(CH3COO)2·2H2O
(0.22 g, 1 mmol), H2OBA (0.26 g, 1 mmol), and DPT (0.24 g, 1
mmol) in 30 mL of DMF/acetonitrile (1:1) and sonicating the mixture
for 60 min at ambient temperature and atmospheric pressure. The
mixture was then centrifuged, and the resulting powder was washed
with DMF and dried at 80 °C for 48 h. Yield: 0.37 g (85% based on
OBA). IR data for selected bands (KBr pellet, ν/cm−1): 656(w),
780(w), 874(w), 1091(w), 1160(m), 1231(m), 1399(vs), 1500(s),
1629(s), 1672(s), 3429(m). Elemental analysis (%) found for
[Zn(C14O5H8)(C12N6H8)0.5]·(C3ONH7): C, 54.0; N, 10.9; H, 3.9.
Fluorescence Measurements. Luminescence spectra were
recorded with a PerkinElmer LS-55 fluorescence spectrometer at
room temperature. Both the excitation and emission slit widths were
10 nm. Fluorescence measurements were carried out in a 1 cm quartz
cuvette.
■
Characterization. TMU-34(-2H) was synthesized in a fast
and facile manner via a sonochemical reaction using zinc
acetate, H2OBA as the oxygen donor ligand, and DPT as the
nitrogen donor spacer (Scheme 1). The PXRD pattern of the
sonochemically synthesized TMU-34(-2H) is identical to
simulated pattern reported earlier (Figure S1).32,33
TMU-34(-2H) is constructed from paddle-wheel
Zn2(COO)4 clusters pillared by DPT spacer ligands.32 It
contains three-dimensional interconnected pores (aperture size:
4.4 Å × 8.1 Å, including van der Waals radii) that are
functionalized with tetrazine groups (Figures S2 and S3).32 To
study the porosity of TMU-34(-2H), N2 adsorption/desorption
was carried out at 77 K and 1 bar on the sonochemically
synthesized sample. The results showed that TMU-34(-2H)
can adsorb 201 cm3·g−1 N2 with a Brunauer−Emmett−Teller
(BET) specific surface area of 667 m2·g−1 (Figure S4).
Thermogravimetric analysis showed that there is a weight loss
between 110 and 220 °C that is attributed to the loss of two
For fluorescence measurements, the following steps were taken: (I)
Stock solutions in water of nitrate salts of metal ions (Na+, Mg2+, Sr2+,
Al3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Pb2+, Hg2+, Li+, K+, Fe2+, Fe3+, Ca2+,
and Cr3+) at a concentration of 10−3 M were prepared. (II) Highly
dispersed emulsions of TMU-34(-2H) were prepared by introducing 2
B
DOI: 10.1021/acs.inorgchem.7b01155
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
guest DMF molecules (calculated 14.42% and found 16.43%).
A second weight loss was observed in the range of 290−400 °C
corresponding to decomposition of the framework (Figure S5).
EDAX analysis was used to determine the Hg(II) adsorption
after sensing tests. The results for Hg(II)@TMU-34(-2H) in
water and acetonitrile showed that each tetrazine moiety
interacts with one Hg(II) ion (Figures S6−S9). Also, the
element mapping data indicated the distribution of Hg(II) and
Zn(II) inside the framework (Figures S10−S13).
Photoluminescence Properties of TMU-34(-2H). Here,
different solvents (water, methanol, ethanol, acetonitrile, DMF,
toluene, and n-hexane) were tested to find the best one for use
in cation sensing applications. For all of the solvents except
water, the excitation and emission wavelengths are centered at
458 and 618 nm, respectively. The emission peak of TMU-34(-
2H) is enhanced with increasing of solvent polarity (Figures 1
emission peak in water (Figure 1). Moreover, contrary to the
general trend for the other solvents, the red shift in the PL
emission peak and decrease in the emission peak intensity
reveals that there is a specific interaction between water
molecules and the TMU-34(-2H) framework.
To explore this behavior of the PL spectrum of TMU-34(-
2H), mixtures of water and acetonitrile were examined.
Acetonitrile was selected because TMU-34(-2H) is dispersed
very well and has relatively intense emission in acetonitrile. As
represented in Figure 2, as the water content in the mixture
increases, the intensity of the emission peak decreases upon
excitation at either 458 and 504 nm. This is in very good
agreement with intensities of TMU-34(-2H) in pure acetoni-
trile and water. Thus, this PL behavior of TMU-34(-2H) in
water/acetonitrile mixtures shows that water molecules interact
with the TMU-34(-2H) framework.
TMU-34(-2H) is functionalized with tetrazine moieties
which are nitrogen-rich. Because the four N(sp2) lone pairs
can act as Lewis basic sites and electron-donating motifs, it is
able to interact through hydrogen bonding with two acidic
hydrogens in water molecules. Thus, because of this hydrogen
bonding, electron density is transferred from the tetrazine
moieties to the two hydrogens in water molecules, and
consequently, the quantum efficiencies of the π → π* and/or
n → π* transitions are reduced, and the fluorescence emission
intensity decreases.34−36
1,2,4,5-Tetrazine contains four π-accepting and σ-donating
N(sp2) atoms, and therefore, it has simultaneous electron-
donor/acceptor characteristics.37 The contribution of the
electron-donating/accepting characteristics along with solvation
effects (hydrogen bonding in water) on secondary interactions
of the tetrazine motifs inside the TMU-34(-2H) framework
cause the unique behavior and different signal transduction in
cation sensing. Hence, because of the different behaviors of
TMU-34(-2H) in water and acetonitrile, sensing of cations was
investigated in both solvents.
Figure 1. Effect of the solvent on the TMU-34(-2H) fluorescence
emission peak.
Sensing of Hg2+ in Acetonitrile and Water. The PL
spectra of TMU-34(-2H) in acetonitrile were recorded under
ambient conditions in the presence of various cations as
mentioned in the experimental section. None of the cations
except Hg2+ have a significant effect on the PL spectrum of
TMU-34(-2H), whereas the PL spectrum shows 90%
quenching and 243% enhancement in the presence of Hg2+in
acetonitrile and water, respectively (Figures 3, S15, and S16).
and S14 and Table S1). TMU-34(-2H) demonstrates different
PL behavior in water, and its excitation and emission
wavelengths are centered at 504 and 648 nm, respectively.
Water is the most polar solvent among these selected solvents,
and on the basis of the trend for the other solvents, TMU-34(-
2H) was expected to have the highest emission intensity in
water. However, it actually has the lowest intensity for the
Figure 2. PL emission of TMU-34(-2H) in water (W.)/acetonitrile (A.) mixtures upon excitation at (a) 504 nm (the excitation wavelength of pure
water) and (b) 458 nm (the excitation wavelength of pure acetonitrile).
C
DOI: 10.1021/acs.inorgchem.7b01155
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 3. (a) Effects of cations on the PL peak at 618 nm upon excitation at 458 nm in acetonitrile. (b) Effects of cations on the PL peak at 648 nm
upon excitation at 504 nm in water.
Table 1. Evaluated Sensing Parameters for TMU-34(-2H) in Water and Acetonitrile
em
solvent
water
acetonitrile
λex (nm)
emission band (nm)
λ
(nm)
response time (s)
signal change
KSV (M−1
)
detection limit (M)
max
504
458
610−710
580−680
648
618
15
15
243% enhancement
90% quenching
3737
1.8 × 10−6
6.9 × 10−6
63618
Scheme 2. Representation of Electron Transfer between Hg2+ and TMU-34(-2H) in Water and Acetonitrile
The emission intensity clearly decreases gradually with
increasing Hg2+ concentration in acetonitrile, but different
behavior occurs in water (Figure S17). As TMU-34(-2H)
shows exceptional selectivity for Hg2+, we aimed to test it in the
presence of other ions. The results show that there is no
significant change in the quenching behavior of TMU-34(-2H)
in the presence of Hg2+ upon addition of other ions (Figure
S18). The evaluated sensing parameters for TMU-34(-2H) in
water and acetonitrile are summarized in Tables 1 and S2. The
value of KSV in acetonitrile is among the highest values reported
for Hg2+ detection (Table 1 and Figure S19).38,39 The detection
limit of TMU-34(-2H) for Hg2+ was calculated on the basis of
the 3δ IUPAC criterion (Table 1 and section 7 in the
Supporting Information).
density from the tetrazine moieties toward Hg2+ ions chelating
to the N(sp2) atoms of the DPT ligands.
As mentioned above, this different behavior in water
compared with acetonitrile may be attributed to the hydrogen
bonding between water molecules and tetrazine moieties in the
TMU-34(-2H) framework in the presence of water as a solvent,
causing the transfer of electron density from the tetrazine ring
toward the hydrogens in water molecules. As a result, contrary
to the electron transfer in acetonitrile, the electrons are
transferred from Hg2+ toward the tetrazine ring, which is most
likely the reason for the enhancement of the PL emission peak
of TMU-34(-2H) in water (Scheme 2).34−36,44
Double Solvent Sensing Method (DSSM). Most
luminescent MOFs for Hg2+ detection are based on quenching
or enhancement of the emission intensity with one-dimensional
(1D) signal transduction. However, one of the most important
factors for an ideal sensor is sensitivity, which cannot be
achieved by this type of signal transduction.45 The double
solvent sensing method (DSSM) is based on simultaneous
combination of two independent and different signal trans-
ductions of TMU-34(-2H) in water and acetonitrile for
construction of a double solvent sensing curve and formulation
of a sensitivity factor that improves the sensitivity and accuracy
of Hg2+ detection.
Lots of research has explored the detection of Hg2+ using
nitrogen- and sulfur-functionalized MOFs because mercury
ions have high affinity toward N and S atoms. Hg2+ ions are
detected by Hg2+−S or Hg2+−N interactions leading to the
quenching effect. It seems that after binding of Hg2+ to S or N
atoms, electrons are transferred from the conjugated π system
of the framework to unoccupied Hg2+ orbitals, causing the
significant fluorescence quenching.19−21,25,27,28,40−43 The tetra-
zine moiety is a relatively weak σ donor and can act as a Lewis
base. Therefore, the quenching of TMU-34(-2H) in acetonitrile
upon addition of Hg2+ may be attributed to transfer of electron
Sensitivity is defined as the change in response in the
presence of the analyte divided by the initial response.45 The
D
DOI: 10.1021/acs.inorgchem.7b01155
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
calculated sensitivity factor in the 2D sensing curve is between
0 and 2 for all of the cations other than Hg2+, whereas for Hg2+
it is equal to 41 (section 8 in the Supporting Information).
These calculations show that by changing from 1D signal
transduction to the 2D sensing method, the sensitivity and
accuracy of Hg2+ detection is highly improved while interfering
effects are eliminated effectively (Table S3 and Figure 4).
other cations have been effectively eliminated and consequently
sensitivity and accuracy of detection have been highly improved
The response time was recorded for acetonitrile- and water-
dispersed TMU-34(-2H) as a fluorescence probe in the
presence of 2 × 10−4 M Hg2+. The results show a fast response
of 15 s for acetonitrile and water at the mentioned
concentration of Hg2+. This very fast response along with the
high value of KSV in comparison with other MOFs may be
attributed to the highly dispersible nature of TMU-34(-2H),
causing greater and easier accessibility of tetrazine groups to
Hg2+ and strong interactions between Hg2+ and these groups
(Table S4).23,24,45,46
Sensor stability and durability through sensing are important
for practical applications.47 PXRD patterns show that TMU-
34(-2H) is stable in both solvents and after sensing experiments
(Figure S1). Furthermore, the sensor response remains
unaltered after five cycles, indicating the high photostability
of TMU-34(-2H) in the presence of Hg2+ cation (Figures S20
and S21). Moreover, comparison of the PXRD patterns of
TMU-34(-2H) before and after five repeated tests clearly shows
this compound to maintain its original structure (Figure S22).
CONCLUSION
■
Figure 4. Sensitivity factors for all of the cations tested.
In this work, we used a sonochemical method to synthesize
tetrazine-functionalized TMU-34(-2H) as a good candidate for
cation sensing because the tetrazine moiety is a π-conjugated
and water-soluble/stable fluorophore with relatively weak σ-
donating Lewis basic sites. TMU-34(-2H) can detect Hg2+
selectively in acetonitrile and water with different 1D signal
transductions. By simultaneous combination of the different
signal transductions of this MOF in acetonitrile (quenching)
and water (enhancement), the double solvent sensing method
with 2D signal transduction is used, which can eliminate the
effects of other cations and amplify sensitivity toward Hg2+.
Calculation of the sensitivity factors shows that by applying the
double solvent sensing method instead of 1D sensing, the
Calculations of sensitivity factors for all of the cations
demonstrate that it is possible to detect Hg2+ by DSSM with
ultrahigh sensitivity. Such a tremendous distinction in the Hg2+
sensitivity factor is visualizable in the double solvent sensing
curve (Figure 5). As shown in Figure 5, two 1D detection
curves of Hg2+ in water and acetonitrile can be combined
together for constructing a 2D double solvent sensing curve.
Hence, this method can reduce/eliminate response-influenc-
ing environmental factors and specially interfering effects of
other cations and hence amplify sensitivity. Figure 4 reveals that
by changing 1D curve to 2D curve the interfering effects of
Figure 5. 2D sensing curve for Hg2+ detection in water and acetonitrile. As can be clearly seen, the accuracy and sensitivity are increased because
interfering effects are eliminated.
E
DOI: 10.1021/acs.inorgchem.7b01155
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(9) Bagheri, H.; Naderi, M. Immersed single-drop microextraction−
electrothermal vaporization atomic absorption spectroscopy for the
trace determination of mercury in water samples. J. Hazard. Mater.
2009, 165, 353−358.
(10) Campanella, B.; Onor, M.; Mascherpa, M. C.; D’Ulivo, A.;
Ferrari, C.; Bramanti, E. Determination of thiomersal by flow injection
coupled with microwave-assisted photochemical online oxidative
decomposition of organic mercury and cold vapor atomic fluorescence
spectroscopy. Anal. Chim. Acta 2013, 804, 66−69.
(11) Shan, F.-S.; Lai, J.-P.; Sun, H.; Zhang, P.; Luo, C.; He, Y.-H.;
Feng, H.-R. A facile, fast responsive and highly selective mercury(II)
probe characterized by the fluorescence quenching of 2,9-dimethyl-
1,10-phenanthroline and two new metal−organic frameworks. RSC
Adv. 2016, 6, 66215−66223.
(12) Ma, S.; He, M.; Chen, B.; Deng, W.; Zheng, Q.; Hu, B. Magnetic
solid phase extraction coupled with inductively coupled plasma mass
spectrometry for the speciation of mercury in environmental water and
human hair samples. Talanta 2016, 146, 93−99.
interfering effects of other cations are completely eliminated
and the sensitivity toward Hg(II) is highly improved. Using this
two-dimensional sensing curve greatly helps in eliminating
interfering effects and thus creates high sensitivity toward
Hg(II) with a fast response.
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.7b01155.
PXRD patterns, crystal structure images, N2 isotherms at
77 K, TGA profile, EDAX analysis, FE-SEM mapping
images, fluorescence spectra, selectivity evaluation, and
detection limit calculation (PDF)
(13) Cheng, H.; Wu, C.; Shen, L.; Liu, J.; Xu, Z. Online anion
exchange column preconcentration and high performance liquid
chromatographic separation with inductively coupled plasma mass
spectrometry detection for mercury speciation analysis. Anal. Chim.
Acta 2014, 828, 9−16.
AUTHOR INFORMATION
Corresponding Author
*E-mail: morsali_a@modares.ac.ir. Tel: (+98) 21-82884416.
ORCID
Mohammad Yaser Masoomi: 0000-0003-1329-5947
Ali Morsali: 0000-0002-1828-7287
■
(14) Laffont, L.; Hezard, T.; Gros, P.; Heimburger, L.-E.; Sonke, J. E.;
̈
Behra, P.; Evrard, D. Mercury(II) trace detection by a gold
nanoparticle-modified glassy carbon electrode using square-wave
anodic stripping voltammetry including a chloride desorption step.
Talanta 2015, 141, 26−32.
(15) Almeida, E. S.; Richter, E. M.; Munoz, R. A. On-site fuel
electroanalysis: Determination of lead, copper and mercury in fuel
bioethanol by anodic stripping voltammetry using screen-printed gold
electrodes. Anal. Chim. Acta 2014, 837, 38−43.
Author Contributions
†S.A.A.R. and M.Y.M. contributed equally to this work.
Notes
The authors declare no competing financial interest.
(16) Pramanik, S.; Zheng, C.; Zhang, X.; Emge, T. J.; Li, J. New
microporous metal−organic framework demonstrating unique selec-
tivity for detection of high explosives and aromatic compounds. J. Am.
Chem. Soc. 2011, 133, 4153−4155.
ACKNOWLEDGMENTS
■
Support of this investigation by Tarbiat Modares University is
gratefully acknowledged.
(17) Cui, Y.; Yue, Y.; Qian, G.; Chen, B. Luminescent functional
metal−organic frameworks. Chem. Rev. 2012, 112, 1126−1162.
(18) Hu, Z.; Deibert, B. J.; Li, J. Luminescent metal−organic
frameworks for chemical sensing and explosive detection. Chem. Soc.
Rev. 2014, 43, 5815−5840.
(19) Wu, L. L.; Wang, Z.; Zhao, S. N.; Meng, X.; Song, X. Z.; Feng,
J.; Song, S. Y.; Zhang, H. J. A Metal−Organic Framework/DNA
Hybrid System as a Novel Fluorescent Biosensor for Mercury(II) Ion
Detection. Chem. - Eur. J. 2016, 22, 477−480.
(20) Zhu, Y.-M.; Zeng, C.-H.; Chu, T.-S.; Wang, H.-M.; Yang, Y.-Y.;
Tong, Y.-X.; Su, C.-Y.; Wong, W.-T. A novel highly luminescent
LnMOF film: a convenient sensor for Hg2+ detecting. J. Mater. Chem.
A 2013, 1, 11312−11319.
(21) Yee, K.-K.; Reimer, N.; Liu, J.; Cheng, S.-Y.; Yiu, S.-M.; Weber,
J.; Stock, N.; Xu, Z. Effective mercury sorption by thiol-laced metal−
organic frameworks: in strong acid and the vapor phase. J. Am. Chem.
Soc. 2013, 135, 7795−7798.
(22) Wang, H.-M.; Yang, Y.-Y.; Zeng, C.-H.; Chu, T.-S.; Zhu, Y.-M.;
Ng, S. W. A highly luminescent terbium−organic framework for
reversible detection of mercury ions in aqueous solution. Photochemical
& Photobiological Sciences 2013, 12, 1700−1706.
(23) Wen, L.; Zheng, X.; Lv, K.; Wang, C.; Xu, X. Two Amino-
Decorated Metal−Organic Frameworks for Highly Selective and
Quantitatively Sensing of HgII and CrVI in Aqueous Solution. Inorg.
Chem. 2015, 54, 7133−7135.
(24) Xu, H.; Gao, J.; Qian, X.; Wang, J.; He, H.; Cui, Y.; Yang, Y.;
Wang, Z.; Qian, G. Metal−organic framework nanosheets for fast-
response and highly sensitive luminescent sensing of Fe3+. J. Mater.
Chem. A 2016, 4, 10900−10905.
(25) Ding, S.-Y.; Dong, M.; Wang, Y.-W.; Chen, Y.-T.; Wang, H.-Z.;
Su, C.-Y.; Wang, W. Thioether-Based Fluorescent Covalent Organic
Framework for Selective Detection and Facile Removal of Mercury-
(II). J. Am. Chem. Soc. 2016, 138, 3031−3037.
REFERENCES
■
(1) Onyido, I.; Norris, A. R.; Buncel, E. Biomolecule−mercury
interactions: modalities of DNA base-mercury binding mechanisms.
Remediation strategies. Chem. Rev. 2004, 104, 5911−5930.
(2) Levina, A.; Lay, P. A. Mechanistic studies of relevance to the
biological activities of chromium. Coord. Chem. Rev. 2005, 249, 281−
298.
(3) Jayabal, S.; Sathiyamurthi, R.; Ramaraj, R. Selective sensing of
Hg2+ ions by optical and colorimetric methods using gold nanorods
embedded in a functionalized silicate sol−gel matrix. J. Mater. Chem. A
2014, 2, 8918−8925.
(4) Senthamizhan, A.; Celebioglu, A.; Uyar, T. Flexible and highly
stable electrospun nanofibrous membrane incorporating gold nano-
clusters as an efficient probe for visual colorimetric detection of
Hg(II). J. Mater. Chem. A 2014, 2, 12717−12723.
(5) Lin, Z. H.; Zhu, G.; Zhou, Y. S.; Yang, Y.; Bai, P.; Chen, J.; Wang,
Z. L. A self-powered triboelectric nanosensor for mercury ion
detection. Angew. Chem., Int. Ed. 2013, 52, 5065−5069.
(6) Yuan, Y.; Jiang, S.; Miao, Q.; Zhang, J.; Wang, M.; An, L.; Cao,
Q.; Guan, Y.; Zhang, Q.; Liang, G. Fluorescent switch for fast and
selective detection of mercury(II) ions in vitro and in living cells and a
simple device for its removal. Talanta 2014, 125, 204−209.
(7) Bazzicalupi, C.; Caltagirone, C.; Cao, Z.; Chen, Q.; Di Natale, C.;
Garau, A.; Lippolis, V.; Lvova, L.; Liu, H.; Lundstrom, I.; et al.
̈
Multimodal Use of New Coumarin-Based Fluorescent Chemosensors:
Towards Highly Selective Optical Sensors for Hg2+ Probing. Chem. -
Eur. J. 2013, 19, 14639−14653.
(8) Domínguez, M. A.; Grunhut, M.; Pistonesi, M. F.; Di Nezio, M.
̈
́
S.; Centurion, M. E. Automatic flow-batch system for cold vapor
atomic absorption spectroscopy determination of mercury in honey
from Argentina using online sample treatment. J. Agric. Food Chem.
2012, 60, 4812−4817.
F
DOI: 10.1021/acs.inorgchem.7b01155
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(26) Chen, Y.; Rosenzweig, Z. Luminescent CdS quantum dots as
selective ion probes. Anal. Chem. 2002, 74, 5132−5138.
(27) Wu, P.; Liu, Y.; Liu, Y.; Wang, J.; Li, Y.; Liu, W.; Wang, J.
Cadmium-Based Metal−Organic Framework as a Highly Selective and
Sensitive Ratiometric Luminescent Sensor for Mercury(II). Inorg.
Chem. 2015, 54, 11046−11048.
High Selectivity and Sensitivity to Picric Acid. ACS Appl. Mater.
Interfaces 2016, 8, 21472−21479.
(46) Tan, H.; Liu, B.; Chen, Y. Lanthanide coordination polymer
nanoparticles for sensing of mercury(II) by photoinduced electron
transfer. ACS Nano 2012, 6, 10505−10511.
(47) Bagheri, M.; Khodadadi, A. A.; Mahjoub, A. R.; Mortazavi, Y.
Highly sensitive gallia-SnO2 nanocomposite sensors to CO and
ethanol in presence of methane. Sens. Actuators, B 2013, 188, 45−52.
(28) Shahat, A.; Hassan, H. M.; Azzazy, H. M. Optical metal−organic
framework sensor for selective discrimination of some toxic metal ions
in water. Anal. Chim. Acta 2013, 793, 90−98.
(29) Clavier, G.; Audebert, P. s-Tetrazines as building blocks for new
functional molecules and molecular materials. Chem. Rev. 2010, 110,
3299−3314.
(30) Hsu, C.-J.; Tang, S.-W.; Wang, J.-S.; Wang, W.-J. Self-assembly
Molecular Complex by 3,6-Di(pyridin-4-yl)-1,2,4,5-tetrazine with
Trimesic Acid through H-Bonding. Mol. Cryst. Liq. Cryst. 2006, 456,
201−208.
(31) Razavi, S. A. A.; Masoomi, M. Y.; Morsali, A. Ultrasonic assisted
synthesis of a tetrazine functionalized MOF and its application in
colorimetric detection of phenylhydrazine. Ultrason. Sonochem. 2017,
37, 502−508.
(32) Razavi, S. A. A.; Masoomi, M. Y.; Islamoglu, T.; Morsali, A.; Xu,
Y.; Hupp, J. T.; Farha, O. K.; Wang, J.; Junk, P. C. Improvement of
Methane−Framework Interaction by Controlling Pore Size and
Functionality of Pillared MOFs. Inorg. Chem. 2017, 56, 2581−2588.
(33) Li, J.; Peng, Y.; Liang, H.; Yu, Y.; Xin, B.; Li, G.; Shi, Z.; Feng, S.
Solvothermal Synthesis and Structural Characterisation of Metal-
Organic Frameworks with Paddle-Wheel Zinc Carboxylate Clusters
and Mixed Ligands. Eur. J. Inorg. Chem. 2011, 2011, 2712−2719.
(34) Odelius, M.; Kirchner, B.; Hutter, J. s-Tetrazine in aqueous
solution: A density functional study of hydrogen bonding and
electronic excitations. J. Phys. Chem. A 2004, 108, 2044−2052.
(35) Xie, D.; Zeng, J. Hydrogen bonding and solvatochromatic shift
of the lowest 1 (n, π*) excitation of s-tetrazine in its hydrated clusters
and dilute solutions. J. Comput. Chem. 2004, 25, 1487−1495.
(36) Yuasa, J.; Mitsui, A.; Kawai, T. π−π* Emission from a tetrazine
derivative complexed with zinc ion in aqueous solution: a unique
water-soluble fluorophore. Chem. Commun. 2011, 47, 5807−5809.
(37) Kaim, W. The coordination chemistry of 1,2,4,5-tetrazines.
Coord. Chem. Rev. 2002, 230, 127−139.
(38) Yang, J.; Wang, Z.; Li, Y.; Zhuang, Q.; Zhao, W.; Gu, J.
Porphyrinic MOFs for reversible fluorescent and colorimetric sensing
of mercury(II) ions in aqueous phase. RSC Adv. 2016, 6, 69807−
69814.
(39) Rudd, N. D.; Wang, H.; Fuentes-Fernandez, E. M. A.; Teat, S. J.;
Chen, F.; Hall, G.; Chabal, Y. J.; Li, J. Highly Efficient Luminescent
Metal−Organic Framework for the Simultaneous Detection and
Removal of Heavy Metals from Water. ACS Appl. Mater. Interfaces
2016, 8, 30294−30303.
(40) Xu, X.-Y.; Yan, B. Fabrication and application of a ratiometric
and colorimetric fluorescent probe for Hg2+ based on dual-emissive
metal−organic framework hybrids with carbon dots and Eu3+. J. Mater.
Chem. C 2016, 4, 1543−1549.
(41) He, J.; Yee, K.-K.; Xu, Z.; Zeller, M.; Hunter, A. D.; Chui, S. S.-
Y.; Che, C.-M. Thioether side chains improve the stability,
fluorescence, and metal uptake of a metal−organic framework.
Chem. Mater. 2011, 23, 2940−2947.
(42) Xu, F.; Kou, L.; Jia, J.; Hou, X.; Long, Z.; Wang, S. Metal−
organic frameworks of zeolitic imidazolate framework-7 and zeolitic
imidazolate framework-60 for fast mercury and methylmercury
speciation analysis. Anal. Chim. Acta 2013, 804, 240−245.
(43) Jia, J.; Xu, F.; Long, Z.; Hou, X.; Sepaniak, M. J. Metal−organic
framework MIL-53 (Fe) for highly selective and ultrasensitive direct
sensing of MeHg+. Chem. Commun. 2013, 49, 4670−4672.
(44) El-Qisairi, A. K. Synthesis, characterization and semiempirical
calculations of mercury(II) complexes of 3,6-bis(2′-pyridyl)-1,2,4,5-
tetrazine. J. Coord. Chem. 2007, 60, 1069−1076.
(45) Bagheri, M.; Masoomi, M. Y.; Morsali, A.; Schoedel, A. Two
Dimensional Host−Guest Metal−Organic Framework Sensor with
G
DOI: 10.1021/acs.inorgchem.7b01155
Inorg. Chem. XXXX, XXX, XXX−XXX