o-Phenylenediamine as a reaction-based probe for the fluorescent detection of Ce(IV) ions

Article abstract of DOI:10.1177/1747519820924638

o-Phenylenediamine as a new fluorescent probe is designed for detecting Ce(IV) ions. The mechanism of detection relies on the oxidative activity of Ce(IV) ions, which can promote the oxidative cyclization of o-Phenylenediamine leading to the formation of fluorescent 2,3-diaminophenazine and giving a more than 150-fold fluorescence enhancement. Furthermore, the o-Phenylenediamine fluorescent probe was effectively used for the detection of Ce(IV) ions in river water, tap water, rainwater, and lateritic soil from Ganzhou.

Full text of DOI:10.1177/1747519820924638

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research-arti
2cle2020 4638CHL0010.1177/1747519820924638Journal of Chemical ResearchLai et al.
Research Paper
Journal of Chemical Research
–6
1
o-Phenylenediamine as a reaction-based probe
for the fluorescent detection of Ce(IV) ions
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1
1
1
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Xiaojing Lai , Qiuxiang Ye , Ruixiang Wang , Peng Wang
1
and Jin-Biao Liu
Abstract
o-Phenylenediamine as a new fluorescent probe is designed for detecting Ce(IV) ions. The mechanism of detection relies
on the oxidative activity of Ce(IV) ions, which can promote the oxidative cyclization of o-Phenylenediamine leading
to the formation of fluorescent 2,3-diaminophenazine and giving a more than 150-fold fluorescence enhancement.
Furthermore, the o-Phenylenediamine fluorescent probe was effectively used for the detection of Ce(IV) ions in river
water, tap water, rainwater, and lateritic soil from Ganzhou.
Keywords
Ce(IV) ions, detection, fluorescence analysis, o-phenylenediamine, reaction-based probe
Date received: 15 March 2020; accepted: 17 April 2020
spectrophotometry,12 neutron activation analysis (NAA),13
Introduction
inductively coupled plasma mass spectrometry (ICP-MS),
Cerium (Ce), the most abundant rare-earth element, has
been widely used in industry as a polishing powder, as a
phosphor agent, as magnets, as a catalyst, and as a ceramic
14,15
and electrochemical methods.
However, these methods
possess several shortcomings, such as high cost, long pro-
cessing times, and complex sample preparation. Recently,
fluorescence sensors have become a powerful tool for the
detection of important analytes in the environment and in
1
–3
colorant. Although Ce(III) exists naturally in cerium flu-
orocarbonate minerals, during the process of mineral
extraction and metallurgy, Ce(III) is usually converted into
4
–6
Ce(IV) for easier extraction in the post-treatment stage.
This process further increases the exposure of Ce(IV) to the
community. High concentrations of Ce ions are known to
1School of Metallurgical and Chemical Engineering, Jiangxi University of
Science and Technology, Ganzhou, P.R. China
College of Biological, Chemical Science and Engineering, Jiaxing
7
,8
be harmful to the environment and human health. For
instance, long-term exposure to Ce(IV) ions would proba-
bly lead to dysfunction in circulatory systems, the immune
2
University, Jiaxing, P.R. China
9
Corresponding authors:
Peng Wang, College of Biological, Chemical Science and Engineering,
Jiaxing University, 118 Jiahang Road, Jiaxing 314000, P.R. China.
system, and the central nervous system in humans.
Therefore, accuracy, precision, and rapid determination of
Ce(IV) ions are very important for the environment and in Email: 815207636@qq.com
clinical applications.
Various instruments are commonly used for the detection
of Ce ions, such as X-ray fluorescence, inductively cou- 341000, P.R. China.
Jin-Biao Liu, School of Metallurgical and Chemical Engineering, Jiangxi
University of Science and Technology, 86 Hongqi Road, Ganzhou
10
11
pled plasma atomic emission spectrometry (ICP-AES),
Email: liujinbiao@jxust.edu.cn

2
Journal of Chemical Research 00(0)
in fluorescence only occurred when both Ce(IV) and OPD
were present in the system (Figure 1(b) and (c)).
Furthermore, only when OPD and Ce(IV) ions were pre-
sent, a strong absorption band between 350 and 550nm
could be found in the nature of UV-Vis absorption spectrum
(Figure S1). To confirm the product, the detection reaction
was performed at a millimolar level, and the OPDox prod-
uct was obtained with the structure being confirmed by
1
13
H/ C NMR spectroscopy (Figure S2 and S3). At the same
time, bright yellow fluorescence could be observed with
the naked eye via irradiation with an ultraviolet lamp at
3
65nm (Figure 1(b)) when OPD (1mM) and Ce(IV) ions
Scheme 1. Reaction principle for the detection of Ce(IV) ions.
(1mM) were mixed at room temperature. Hence, OPD as a
new and practical probe for the sensing Ce(IV) ions was
studied in further detail.
organisms because of their simplicity and high sensitiv-
16–20
ity.
Up to now, several fluorescence sensors have been
In order to ascertain the optimal sensing system, varying
21–25
exploited to detect the Ce ions.
However, some of these
MeCN/H O ratios were investigated for the luminescence
2
methods are restricted by toxic inorganic nanomaterials, low
sensitivity, or low selectivity. Recently, a rhodamine-based
response of the detection reaction. The highest lumines-
cence enhancement was obtained with a 4:1 MeCN/H O
2
26
27
probe and a Schiff base probe have been reported for the
recognition of Ce(IV) ions, respectively. The two probes
both show high selectivity and sensitivity, but with rela-
tively complex molecular structures. We also reported a
cascade-reaction-based fluorescence probe for the detection
ratio (Figure 2). However, the luminescence rate started to
decrease slowly thereafter. The incubation time was then
investigated. It can be found that the fluorescence intensity
of the system containing Ce(IV) ions increases with an
extended incubation time and reaches a steady state at 3h
28
of Ce(IV) ions. Ce(IV) ions can oxidize 2-naphthol, which
subsequently reacts with o-phenylenediamine (OPD) to pro-
duce fluorescent benzo[a]phenazine. Although this method
is efficient for the fluorescence detection of Ce(IV) ions,
multistep reactions are inconvenient for detecting ions.
Therefore, it is necessary to develop a rapid, sensitive, and
efficient Ce(IV)-ion-sensing platform.
(Figure 3). However, no obvious fluorescence enhance-
ment was measured without the Ce(IV) ions. We therefore
chose a 4:1 MeCN/H O as the best mixed solvent and 3h as
2
the optimal incubation time.
Sensitivity is of importance for an analytical method.
Hence, the fluorescence responses of the detection method
to various concentrations of Ce(IV) ions were examined in
detail. At room temperature, a system containing OPD
In recent years, the luminescent properties of 2,3-diami-
nophenazine (OPDox) have received extensive attention in
the fields of analytical chemistry, organic synthesis, and
(40μM) was uniformly mixed with different concentrations
of Ce(IV) ions (Figure 4). A highest 150-fold increase in
fluorescence was obtained on increasing the concentration
of Ce(IV) ions (0–88μM). Two linear relationships were
2
9–32
materials chemistry.
Notably, the Ce(IV) ions have
been generally studied as a single-electron oxidant in vari-
3
3,34
ous reactions.
As an efficient single-electron oxidizer,
2
established at ranges of 0.4–4μM (R =0.9979) and 5–36μM
Ce(IV) can efficiently promote the oxidative cyclization of
2
(
R =0.9988), respectively. At low Ce(IV) concentrations,
3
5–37
OPD to generate OPDox.
In this work, as a continua-
OPD was converted into fluorescent OPDox and could be
rapidly detected, resulting in a high sensitivity of the fluo-
rescence response. At higher Ce(IV) concentrations, more
fluorescent product was formed and the reaction proceeded
over a larger time window. This, together with the higher
fluorescence intensity, resulted in a lower slope. Therefore,
the probe exhibited different linear correlations at different
Ce(IV) concentration ranges. According to the limit of
detection (LOD)=3σ/s, 26nM of the LOD was calculated.
tion of our ongoing studies on reaction-based fluorescent
3
8–41
probes,
OPD is used as a reaction-based fluorescent
probe for the detection of Ce(IV) ions. In this detection pro-
cess, OPD can be rapidly oxidized by Ce(IV) ions to an
imine, which then undergoes as a further intermolecular
cycloaddition to form the product OPDox which possesses
yellow fluorescence, thus realizing the fluorescent detec-
tion of Ce(IV) ions (Scheme 1).
26
Compared to our previous work, this method shows a
wider detection range and a lower LOD.
Results and discussion
The method was also applied to solid-phase conditions.
The solvent for the reaction of Ce(IV) ions and OPD was The letters of “Ce” were written on a thin-layer chroma-
first investigated, including MeCN, dimethylformamide tography (TLC) aluminum sheet using the reaction solu-
(
DMF), dimethyl sulfoxide (DMSO), EtOH, CH Cl , and tion of OPD and Ce(IV) ions as an “ink” (Figure 5). When
2 2
H O. In the experiment, OPD (40μM) was mixed with the solvent was dried, we observed the TLC sheet under
2
Ce(IV) ions (0.4μM) for 1h at room temperature. It was daylight and UV 254 and 365nm irradiation. Compared
observed that the effect of the solvent was significant, and with the reaction solution that did not contain any Ce(IV)
the maximum fluorescence enhancement was observed in ions, the “Ce” containing both OPD and Ce(IV) ions emits
MeCN (Figure 1(a)). Control experiments were carried out bright yellow fluorescence under 365nm UV irradiation.
in order to investigate the effect of the various components Therefore, this method serves as a visual fluorescence
in the sensing system. It was thus shown that enhancement probe for Ce(IV) ions.

Lai et al.
3
Figure 1. Fluorescence emission spectra (λ =436nm) of the sensing system containing 40μM OPD, (a) with or without Ce(IV)
ex
ions (0.4μM) in the indicated solvents and (b) the emission spectra of the control experiments in MeCN. (c) Photographs of 1mM
of Ce(IV) (I), 1mM of OPD (II), and 1mM of Ce(IV) with 1mM of OPD(III) under 365nm UV illumination.
enhancement was obtained, even at a concentration of 20μM.
The specificity of the probe for Ce(IV) ions was also excel-
lently observed from a competition experiment conducted by
mixing Ce(IV) ions (0.4μM) in a system with another ion
(20μM). Comparable fluorescence enhancements indicated
that this organic reaction–based probe possesses high selec-
tivity toward Ce(IV) ions.
A Job’s plot experiment was carried out for the determi-
nation of the stoichiometric ratio of the interaction between
Ce(IV) ions and OPD (Figure 7). The 2:1 ratio obtained
from the Job’s plot experiment is consistent with the reac-
tion mechanism.
Finally, the detection of Ce(IV) ions was studied in real
samples using the fluorescent probe. Samples of Ganjiang
River water, tap water, rainwater, and lateritic soils were col-
Figure 2. Fluorescence enhancement of OPD (40μM) with
.4μM of Ce(IV) ions in various percentages of water in MeCN.
42,43
lected and pretreated according to previous methods.
0
When exogenous Ce(IV) ions (19.2μM) were added to the
samples, significant luminescence intensities were observed.
As shown in Table 1, recovery rates of 94.78% and 93.68%
could be obtained in Ganjiang River water and tap water sam-
ples, respectively. Higher recovery rates of 97.39% and
98.77% were obtained for rainwater and lateritic soils sam-
ples, respectively. These results show that our fluorescent
detection method can be applied for Ce(IV) ions sensing in
real samples with good sensitivity.
Conclusion
In this work, a reaction-based switch-on fluorescent probe for
Ce(IV) ions has been reported. The reaction is based on a tan-
dem oxidation–cyclization reaction between the OPD and
Ce(IV) ions, forming fluorescent OPDox. A maximum 150-
fold fluorescence enhancement is observed in response to
Ce(IV) ions, with good selectivity and sensitivity. Its applica-
bility can provide a platform for the development of the next-
generation Ce(IV)-ion probes for use in real-world scenarios.
Figure 3. The fluorescence intensity of the system in the
presence and absence of Ce(IV) ions with the indicated time.
The concentration of Ce(IV) ions is 0.4 and 40μM for OPD in
MeCN containing 20% H O. The fluorescence was monitored
2
at 15min intervals and collected at a wavelength of 526nm.
To show the excellent selectivity of this sensing method, Experimental
1
9 common cations, 11 common anions, and 15 rare-earth
General instrumentations and materials
cations were all investigated (Figure 6). It can be found that
only Ce(IV) ions (0.4μM) gave an obvious enhancement in The UV-Vis spectra were recorded on an ultraviolet spectro-
the fluorescence. As for other ions, only a slight fluorescence photometer (UV-2550). Emission spectra were performed

4
Journal of Chemical Research 00(0)
Figure 4. (a) Fluorescence responses of the system to various concentrations of Ce(IV) ions. The concentration of OPD is 40μM
and the concentration of Ce(IV) ions is in the range of 0–88μM. (b) Fluorescence responses at 526nm of the system at various
concentrations of Ce(IV) ions (1–120µM). The linear correlation between fluorescence intensity and the concentration of Ce(IV)
ions (c) 0.4–4µM and (d) 5–36µM. λ =436nm, λ =526nm.
ex
em
m (multiplet), dd (doublet of doublet), and bs (broad sin-
13
glet). C NMR spectra were recorded on Bruker spectrom-
eter with complete proton decoupling, and chemical shifts
were reported in ppm from TMS with the solvent as the
internal reference (DMSO-d , δ=39.5ppm).
6
Detection method
Figure 5. Photographs of TLC sheets with letters written
using OPD (top row) or OPD-Ce(IV) (bottom row) as “ink”
recorded under (a) daylight and UV light at (b) 254nm and (c)
The OPD was added into MeCN to a final concentration of
4
0μM. Different concentrations of Ce(IV) ions were then
3
65nm.
added to MeCN containing OPD (40μM) in a cuvette.
Then, emission spectra were recorded after 3-h incubation
in the range of 460–650nm at λex = 436nm, and the slit
width is 10nm/20nm.
on a fluorescence spectrometer (F-4600). Error limits were
estimated: λ (±1nm), τ (±10%), and ϕ (±10%). The sol-
vents were distilled from standard drying agents. Unless
otherwise stated, commercial reagents purchased from Alfa
Aesar, Acros, and Aldrich chemical companies were used
Preparation of real samples
without further purification. Purification of reaction prod- Ganjiang River water was collected from the Ganjiang
ucts was carried out by flash chromatography using Qing River. Tap water was collected from chemistry laboratory.
1
Dao Sea Chemical Reagent silica gel (200–300 mesh). H Rainwater was collected from Ganzhou. Ce(IV) ions were
NMR spectra were recorded on a Bruker Avance III 400 spiked into various water samples to obtain sample solu-
(
400MHz) spectrometer and referenced internally to the tions with 19.2μM of Ce(IV) ions. Lateritic soils were
residual proton resonance in DMSO-d with tetramethylsi- collected from Ganzhou. Ce(IV) ions (0.05mmol) were
6
lane (TMS; δ=0.00ppm) as the internal standard. Chemical spiked into 5g of soil and stirred well before use. Then,
shifts were reported as parts per million (ppm) in the δ scale the sample was extracted with water. After filtration, the
downfield from TMS. Multiplicity is indicated as follows: s sample was diluted to obtain a solution with 19.2μM of
(singlet), d (doublet), t (triplet), q (quartet), quint (quintet), Ce(IV) ions.

Lai et al.
5
Figure 6. Fluorescence intensity upon addition of 19 common cations (a) (Cu +, Mg2+, K , Zn , Ag , Co +, Al3+, Fe3+, Na+,
2
+
2+
+
2
2
+
2+
2+
3+
2+
2+
2+
2+
2+
2+
−
2−
−
−
2−
2−
−
Ca , Li , Mn , Cr , Fe , Ba , Sn , Ni , Hg , and Pt ), (b) 11 common anions (I , CO Br , Cl , SO SO HSO ,
3+
3
3
4
4
3
−
2−
2−
3−
3+
3+
3+
3+
3+
3+
3+
3+
3+
3+
3+
HCO , S , S O
NO ), and (c) 15 rare-earth cations (Ce , Nd , Gd , Dy , Tb , Bi , Y , La , Lu , Eu , Pr , Pm ,
2
3
3
+
3+
3+
Yb , Sc , and Er ). The red bars represent the addition of 20μM of different ions to the sensor system. The black bars represent
the subsequent addition of 0.4μM Ce(IV) ions to the system. λ =436nm, λ =526nm.
ex
em
measured in the range of 460–650nm with an excitation
wavelength at 436nm, and the slit width is 10nm/20nm.
Synthesis of 2,3-diaminophenazine
OPD (0.5mmol) and Ce(IV) ions (0.6mmol) were added
into a round bottom flask, and then, solvent MeCN/H O
2
(v/v=4:1) was added. The mixture was stirred at room tem-
perature for 3h. Then, the mixture was quenched with satu-
rated NaCl solution, extracted by EtOAc, and dried over
Na SO . The crude product was purified by flash column
2
4
chromatography to provide the corresponding yellowish-
brown product 2,3-diaminophenazine, and the yield was
1
8
3
(
9%. H NMR (400MHz, DMSO-d ) δ 7.87 (dd, J=6.5,
6
.4Hz, 2H), 7.53 (dd, J=6.5, 3.4Hz, 2H), 6.88 (s, 2H), 6.31
s, 4H); C NMR (101MHz, DMSO-d ) δ 144.81, 142.16,
Figure 7. Job’s plot for determining the stoichiometry of
Ce(IV) ions and OPD; the total concentration of Ce(IV) ions
and OPD was 100μM. Molar fraction is given by [Ce(IV)]/
1
3
6
1
40.08, 127.87, 127.06, 102.15.
([Ce(IV)]+[OPD]).
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with
respect to the research, authorship, and/or publication of this
article.
Table 1. Investigations on the detection of Ce(IV) ions in
water samples and lateritic soil samples.
a
Samples
pH Added Found Standard RSD (%, Recovery
amount amount deviation n = 3) (%, n = 3) Funding
μM) (μM) (μM)
(
The author(s) disclosed receipt of the following financial support
for the research, authorship, and/or publication of this article:
Financial support from the Natural Science Foundation of China
Ganjiang
River water
Rain water 6.21 19.20 17.99 1.22
Tap water 5.49 19.20 18.70 0.43
Lateritic
soils
8.07 19.20 18.20 0.65
1.91
94.78
(
21762018 and 21961014), the program of Qingjiang Excellent
Young Talents of Jiangxi University of Science and Technology
JXUSTQJBJ2018003), and the Science and the Technology
2.31
0.95
0.46
93.68
97.37
98.77
(
5.40 19.20 18.96 0.23
Innovation Outstanding Young Talents Program of Jiangxi
Province (20192BCBL23009) is gratefully acknowledged.
RSD: relative standard deviation.
a
Results for the determination of Ce(IV) ions in real samples.
Experimental conditions: MeCN/H O (v/v=4:1); OPD (40μM), Ce(IV)
19.2μM).
ORCID iD
2
Jin-Biao Liu
https://orcid.org/0000-0002-5038-6541
(
Supplemental material
Detection of OPD in real samples
Supplemental material for this article is available online.
Real samples (water samples and soil samples) were added
to a sensing system containing OPD (40μM) in MeCN
References
containing 20% H O. Then, the mixture solution was incu-
bated at room temperature for 3h. Emission spectra were
1. Abedi MR, Zamani HA, Ganjali MR, et al. Int J Environ
Anal Chem 2018; 88: 353.
2

6
Journal of Chemical Research 00(0)
2
3
. Hedrick JB and Sinha SP. J Alloys Compd 1994; 207: 377.
. Li M, Liu ZG, Liu LS, et al. J Chin Rare Earth Soc 2003; 21:
22. Rofouei MK, Tajarrod N, Masteri-Farahani M, et al. J
Fluoresc 2015; 25: 1855.
4
65.
23. Cui H, Zhang Q, Myint A, et al. J Photochem Photobiol A
Chem 2006; 181: 238.
. Luo XF, Huang XW, Zhu ZW, et al. J Rare Earth 2019; 24. Wang Y, Yan F, Kong D, et al. Desalin Water Treat 2018;
7: 119.
107: 147.
. Zhang D, Wang W, Deng Y, et al. Chem Eng J 2012; 179: 19. 25. Huang CZ, Li KA and Tong SY. Chin J Anal Chem 1997;
4
5
. Moore FL. Anal Chem 1969; 41: 1658.
2
6
7
. García A, Espinosa R, Delgado L, et al. Desalination 2011;
69: 136.
25: 768.
2
26. Huang L, Liu Y, Ma C, et al. Dyes Pigments 2013; 96: 770.
8
9
. Cassee FR, van Balen EC, Singh C, et al. Crit Rev Toxicol 27. Ghosh M, Ta S, Banerjee M, et al. J Photochem Photobiol A
011; 41: 213.
Chem 2018; 367: 32.
. Cheng W, Park SS, Weineng T, et al. J Rare Earth 2010; 28: 28. Lai X, Wang R, Li J, et al. RSC Adv 2019; 9: 22053.
2
7
85.
29. Sun J, Wang B, Zhao X, et al. Anal Chem 2016; 88: 1355.
30. Li F, Liu J, Hu Y, et al. Talanta 2018; 186: 330.
1. Achilli M, Ciceri G, Ferraroli R, et al. Analyst 1989; 114: 31. Wang J, Li H, Cai Y, et al. Anal Chem 2019; 91: 6155.
1
1
0. Masi AN and Olsina RA. Talanta 1993; 40: 931.
3
19.
2. Amin AS, Moustafa MM, Issa RM, et al. Talanta 1997;
4: 311.
32. Khattar R, Yadav A and Mathur P. Spectrochim Acta 2015;
142: 375.
33. Das AK. Coordin Chem Rev 2001; 213: 307.
1
1
1
4
3. Hamajima Y, Koba M, Endo K, et al. J Radioanal Nucl 34. Nair V and Deepthi A. Chem Rev 2007; 107: 1862.
Chem 1985; 89: 315.
4. Gupta VK, Singh AK and Gupta B. Anal Chim Acta 2006:
35. Wang YC, Liu JB, Zhou H, et al. J Org Chem 2020; 85:
1906.
5
75: 198.
36. Li X, Lin Q, Qu WJ, et al. Chin J Org Chem 2017; 37: 889.
37. Ni YY, Jiang YC, Hu MC, et al. Acta Chim Sin 2010; 68: 982.
6. Lee MH, Kim JS and Sessler JL. Chem Soc Rev 2015; 44: 38. Lai X, Qiu G, Ye Q, et al. J Photochem Photobiol A Chem
185.
2020; 386: 112101.
7. Tong SL, Xiang GH and Liu WP. Chin J Anal Chem 2005; 39. Liu JB, Wu C, Chen F, et al. Anal Chim Acta 2019; 1083: 166.
1
1
5. Khoo SB and Zhu J. Electroanalysis 1999; 11: 546.
4
1
5
3: 80.
40. Wu C, Wu KJ, Liu JB, et al. Chem Commun 2019; 55: 6353.
41. Wang RX, Lai XJ, Qiu GYS, et al. Chin J Org Chem 2019;
39: 952.
1
1
8. Ueno T and Nagano T. Nat Methods 2011; 8: 642.
9. Wang N, Wang R, Tu Y, et al. Spectrochim Act A 2018; 196:
3
03.
42. Jacobson AR, Dousset S, Andreux F, et al. Environ Sci
Technol 2007; 41: 6343.
1. Salehnia F, Faridbod F, Dezfuli AS, et al. J Fluoresc 2017; 43. Wang Y, Li J, Gao Y, et al. Hydrometallurgy 2020; 191:
7: 331.
105220.
2
2
0. Dong X, Wang R, Liu G, et al. Tetrahedron 2016; 72: 2935.
2