A rhodamine-based dual chemosensor for the naked-eye detection of Hg2+and enhancement of the fluorescence emission for Fe3+

Article abstract of DOI:10.1039/d0pp00302f

A novel fluorescent chemosensor based on trimesoyl chloride-rhodamine (TR) was successfully synthesized. Rising chromogenic and fluorogenic spectral enhancements could be observed in trimesoyl chloride-rhodamine (TR) probes when Hg2+ and Fe3+ were added, respectively. TR has shown selectivity for Hg2+ and Fe3+ with high sensitivity due to metal ion complexation induced photophysical "turn-on"signaling responses. The detection limit towards Hg2+ was 2.46 × 10-8 M as determined by the 3σ method. At the same time, fluorogenic spectral enhancements were observed in TR, which exhibits a superior sensitive and selective recognition towards Fe3+ with 4.11 × 10-8 M of the detection limit. The test strips were used for colorimetric and simple detection towards Hg2+, which might finally enable the advancement of the Hg2+ sensor in the field of on-site detection. This journal is

Full text of DOI:10.1039/d0pp00302f

Photochemical &
Photobiological Sciences
View Article Online
View Journal
PAPER
A rhodamine-based dual chemosensor for the
naked-eye detection of Hg2+ and enhancement
of the fluorescence emission for Fe3+†
Cite this: DOI: 10.1039/d0pp00302f
a,b
Jian-Peng Hu,a Hao-Hang Yang,a Qi Lin, a Hong Yao,a You-Ming Zhang,
Tai-Bao Wei *a and Wen-Juan Qu*a
A novel fluorescent chemosensor based on trimesoyl chloride–rhodamine (TR) was successfully syn-
thesized. Rising chromogenic and fluorogenic spectral enhancements could be observed in trimesoyl
chloride–rhodamine (TR) probes when Hg2+ and Fe3+ were added, respectively. TR has shown selectivity
for Hg2+ and Fe3+ with high sensitivity due to metal ion complexation induced photophysical “turn-on”
signaling responses. The detection limit towards Hg2+ was 2.46 × 10−8 M as determined by the 3σ
method. At the same time, fluorogenic spectral enhancements were observed in TR, which exhibits a
superior sensitive and selective recognition towards Fe3+ with 4.11 × 10−8 M of the detection limit. The
test strips were used for colorimetric and simple detection towards Hg2+, which might finally enable the
advancement of the Hg2+ sensor in the field of on-site detection.
Received 11th September 2020,
Accepted 10th November 2020
DOI: 10.1039/d0pp00302f
rsc.li/pps
also one of the important integrants in biological systems
because it plays an indispensable role in various physiological
1. Introduction
The problem of heavy metal pollution in the environment is processes. However, a normal level of Fe3+ deficiency and
becoming more and more serious, especially in aquatic and excess of Fe3+ can cause an increase in the incidence of certain
biological systems.1–3 Concerning the harmful effects of heavy cancers and dysfunction of certain organs.16–20 Most reported
metal ions on the human body, the design of rapid, selective fluorescent chemosensors for Fe3+ are based on a fluorescence
and sensitive chemosensors is increasingly in demand to meet quenching mechanism. Therefore, the construction of Fe3+
qualitative and quantitative detection.4,5 Mercury ions, one of chemosensors with fluorescence enhancement is urgently
the most important metal ions in toxic heavy metal ions, have needed.21–23
caused increasing damage to the environment and biological
Traditional heavy metal detection methods generally
systems and they could be generated by various natural pro- include inductively coupled plasma-mass spectroscopy,24,25
cesses, industrial emissions and human activities, such as vol- plasma atomic emission spectrometry, atomic absorption
canic eruptions, gold mining, the coal industry and so on.6–10 spectrometry,26–28 and electrochemical methods.29 However,
Mercury could be assimilated by microorganisms and con- these methods requiring expensive instruments are usually not
verted to methylmercury. Then mercury ions can bind to sulf- suitable for the in situ detection of heavy metal ions in biologi-
hydryl proteins in various human organs such as the kidneys, cal systems and environments.30,31 Fluorescent probes have
brain, immune system and central nervous system by entering become a new analytical method for detecting important
the food chain. All of these are responsible for various serious cations, anions, small neutral molecules and biomacro-
diseases.11–15 Compared with other heavy metal ions, Fe3+ is molecules (such as proteins and DNA) of biological and
environmental relevance,32–40 due to the advantages of fluo-
rescence detection processes, including operational simplicity,
low cost, real-time monitoring, and high sensitivity. In particu-
lar, chromogenic reactions are usually used to detect and
analyze species because of their extremely simple and practical
features.41,42
Rhodamine B derivatives are promising compounds that
fulfill many requirements in many fields with the development
of chromogenic, fluorescent chemosensors and photochro-
mism. Chromogenic and fluorescence detection methods
aKey Laboratory of Polymer Materials of Gansu Province, Research Center of Gansu
Military and Civilian Integration Advanced Structural Materials, College of
Chemistry and Chemical Engineering, Northwest Normal University, Anning East
Road 967, Lanzhou, Gansu, 730070, P. R. China. E-mail: weitaibao@126.com,
quwenjuanlz@163.com
bDeputy Director-General of Gansu Natural Energy Research Institute, Renmin Road 23,
Lanzhou, Gansu, 730000, P. R. China
†Electronic supplementary information (ESI) available. See DOI: 10.1039/
d0pp00302f
This journal is © The Royal Society of Chemistry and Owner Societies 2020
Photochem. Photobiol. Sci.

View Article Online
Paper
Photochemical & Photobiological Sciences
based on rhodamine B derivatives have become indispensable
methods in detecting Hg2+ and other metal ions.43–46
Rhodamine B acts more effectively in Hg2+ detection due to its
long excitation wavelength, good light stability, high fluo-
rescence quantum yield, good water solubility, and less toxicity
compared to other rhodamines.47–50 In recent years, the con-
struction of Hg2+ indicators has aroused great attention from
scientists. The “turn-on” effect of rhodamine on lactam made
it possible to identify specific metal ions.51 Due to the bond
and ring-opening in the structure, a recognition group can be
introduced to modify the rhodamine molecule into various
derivatives.52,53
In the present work, we synthesized a trimesoyl chloride–
rhodamine derivative TR. TR exhibited metal ion complexa-
tion induced photophysical “turn-on” signaling responses.
The chromogenic and fluorogenic spectral enhancements
were observed in trimesoyl chloride–rhodamine (TR) probes
when Hg2+ and Fe3+ were added. TR showed selective detec-
tion of Hg(II) ions and Fe3+ with high sensitivity. The test
strips for the detection of Hg2+ were successfully prepared,
making TR a promising Hg2+ sensor in the field of on-site
detection.
Scheme 1 Cartoon illustration of the fluorescent sensor TR and its
response mechanism for Hg2+ and Fe3+
.
and the solvent was removed under reduced pressure. Add
1 mol L−1 HCl (about 50 mL) to the flask to produce a clear red
solution. On this basis, 1 mol L−1 NaOH (about 70 mL) was
added and stirred until the solution pH reached 9–10. Then
thoroughly dried under vacuum and the reaction afforded the
host compound TR of 0.83 g (75%) as pink solid. 1H NMR
(400 MHz, CDCl3) δ (ppm): 7.94 (s, 1H), 7.44 (d, J = 6.9 Hz,
2H), 7.11 (s, 1H), 6.46 (s, 2H), 6.41 (s, 2H), 3.61 (s, 2H), 3.33 (s,
8H), 1.16 (t, J = 7.0 Hz, 12H). 13C NMR (400 MHz, CDCl3) δ
166.1, 153.8, 151.5, 148.9, 132.5, 128.1, 123.8, 122.9, 108.0,
104.6, 99.98, 65.9. ESI-MS m/z:(M + H)+ calculated C28H33N4O2
457.2595; found 457.2597.
The synthesis of TR was performed with 3 mmol rhoda-
mine B in a 100 mL round bottom flask containing 50 mL
methanol. Then trimesoyl chloride (0.6 mmol, 0.268 g) was
added and the reaction mixture was allowed to stir for 24 h.
After the reaction was completed, the crude product was puri-
fied by silica-gel flash chromatography (ethyl petroleum : ether
acetate: 5 : 1). The product TR was obtained as a red solid, as
shown in Scheme S1;† yield = 54%. 1H NMR (400 MHz, CDCl3)
δ (ppm): 10.40 (s, 3H), 7.91 (s, 3H), 7.79 (s, 3H), 7.51 (s, 6H),
6.99 (s, 3H), 6.51 (s, 6H), 6.27 (s, 12H), 3.24 (s, 12H), 1.02 (s,
18H).
2. Experimental: materials and
methods
2.1. Materials
Rhodamine B, 1,3,5-benzenetricarboxylic acid chloride, hydra-
zine hydrate, concentrated hydrochloric acid and sodium
hydroxide were purchased from Alfa. Analytical solvents such
as ethanol and dichloromethane used in this study were pur-
chased from Samchun Chemicals and used without further
purification. All cations were used as perchlorate salts, which
were purchased from Alfa Aesar.
2.2. Methods
Melting point measurements on X-4 digital melting point
apparatus are not corrected. Fluorescence spectral data were
recorded on a Shimadzu RF-5310 spectrometer. Nuclear mag-
netic resonance (NMR) spectra were recorded on Varian
Mercury 400 and Varian Inova 600 instruments. High-resolu-
tion MS was performed on a Bruker Esquire 3000 Plus spectro-
meter (Bruker-Franzen Analytik GmbH, Bremen, Germany)
equipped with an ESI interface and an ion trap analyzer.
Infrared spectra were recorded on a Digilab FTS-3000 Fourier
transform-infrared spectrophotometer.
2.4. Preparation of the test solution
The stock solution of the TR fluorescent probe (2.0 × 10−4 mol
L−1) was prepared in ethanol. The stock solutions of metal
ions (4.0 × 10−3 mol L−1) were prepared in distilled water with
perchlorate. For the fluorescence spectra, the excitation wave-
length was set to 510 nm (Scheme 1).
2.3. Synthesis of TR
Synthesis of RBA. Rhodamine B (1.20 g, 2.5 mmol) was
placed in a 100 mL flask and subsequently dissolved in 30 mL
ethanol. The solution was stirred at room temperature for
30 min and 3.0 mL of hydrazine hydrate (85%) was added
3. Results and discussion
3.1. The effect of the water content ratio on the TR probe
response to Hg2+ and Fe3+
dropwise into it. The stirred mixture was heated at 85 °C and The effect of the water content ratio on the response of the TR
refluxed for 8 h. The solution changed from dark purple to probe to Fe3+ and Hg2+ was investigated by fluorescence emis-
light orange and then became clear. The mixture was cooled sion spectroscopy and UV-vis. As shown in Fig. S6 and S7,†
Photochem. Photobiol. Sci.
This journal is © The Royal Society of Chemistry and Owner Societies 2020

View Article Online
Photochemical & Photobiological Sciences
Paper
when the water content was 10%, the response of the TR probe
to Fe3+ and Hg2+ ions is most obvious according to the fluo-
rescence emission and UV absorption peaks of the system.
Therefore, we conducted all subsequent experiments with a
water ratio of 10%.
3.2. Effect of pH on the fluorescence of TR
The fluorescence emission of the probes will be changed by
the pH of the system. Therefore, it is essential to optimize the
effect of pH on the fluorescence intensity of the TR probe. The
fluorescence intensity of TR was tested in the presence of
different pH solutions from 1 to 12. As shown in Fig. S10,†
when the pH value was 2, the rhodamine group showed ring
opening reaction. Therefore, TR has a wide range of pH appli-
cations to detect metal ions.
Fig. 2 Fluorescence spectra of target compound TR (2.0 × 10−5 M) in
EtOH/H2O (9 : 1, v/v) solution in the presence of Fe3+ and other metal
ions.
3.3. Metallic ion sensing studies
In order to validate the specificity of TR, we proceeded with
competition experiments with other metal ions (including
The fluorescence emission and UV-vis properties of the TR
probe in the presence of different metal ions (Ag+, Ca2+, Cd2+
,
+
Ca2+, Mg2+, Ba2+, Al3+, Cr3+, Mn2+, Fe3+, Co2 , Ni2+, Cu2+, Zn2+,
Co2+, Cu2+, Hg2+, Fe2+, Fe3+, Ni2+, Zn2+, Mn2+ and Cr3+) were
investigated in EtOH/H2O (9 : 1, v/v). As shown in Fig. 1 and
2, only Hg2+ and Fe3+ showed significant changes in both the
fluorescence emission and UV-vis spectra. Except for Fe3+ and
Hg2+, all the added other cations showed no significant
changes in the fluorescence and UV-vis spectra. When Fe3+
and Hg2+ were added into the solution, strong fluorescence
emission of Fe3+ and the absorption bands of Hg2+ were
observed. The fluorescence color of the probe solution
changed completely from colorless to yellow when 20 times
equivalent Fe3+ was added to the TR solution. Similarly, in
the UV-vis spectra, we could observe that only the addition of
Hg2+ could obviously enhance the UV absorption peak with
the color of the solution changing from colorless to purple
when Hg2+ was added to the TR solution. However, the
addition of Fe3+ could make the UV-vis peak show a slight
enhancement and the solution color changed from colorless
to light pink, while other metal ions could not change the UV
absorption peak. All these results confirmed that Fe3+ and
Hg2+ promote the ring-opening reaction of rhodamine
spironolactone.
Ag+, Cd2+, Pb2+ and Hg2+) being added. As depicted in Fig. 3
and 4, only Fe3+ could induce a significant increase in fluo-
rescence intensity and Hg2+ induced a remarkable increase in
absorption. Other ions showed negligible fluorescence and
absorption responses. These results showed that the presence
of other competitive ions had an inconsiderable effect on the
specific detection of mercury ions and iron.
Fig. 3 UV-vis spectra of target compound TR (2.0 × 10−5 M) in EtOH/
H2O (9 : 1, v/v) solution in the presence of Hg2+ and other metal ions.
Fig. 4 Fluorescence spectra of target compound TR (2.0 × 10−5 M) in
EtOH/H2O (9 : 1, v/v) solution in the presence of Fe3+ and other metal
ions.
Fig. 1 UV-vis spectra of target compound TR (2.0 × 10−5 M) in EtOH/
H2O (9 : 1, v/v) solution in the presence of Hg2+ and other metal ions.
This journal is © The Royal Society of Chemistry and Owner Societies 2020
Photochem. Photobiol. Sci.

View Article Online
Paper
Photochemical & Photobiological Sciences
3.4 Sensitivity studies for Fe3+ and Hg2+
The detection limits of TR for Fe3+ and Hg2+ were 4.11 × 10−8
M and 2.46 × 10−8 M (Fig. S8 and S9†), respectively, and were cal-
culated by the 3σ method.54 It indicated that TR has favorable
selectivity and sensitivity for the detection of Fe3+ and Hg2+.
To demonstrate the efficiency of the TR probe in Fe3+ and Hg2+
quantitative measurements, the TR probe was treated with
various concentrations of Fe3+ and Hg2+ in EtOH : H2O (9 : 1,
v/v) mixed solution. The fluorescence spectra in TR solutions
containing different concentrations of Fe3+ and the UV-vis
spectra in TR solutions with different concentrations of Hg2+
were recorded (Fig. 5 and 6). For the free TR solution, no
obvious characteristic emission and UV-vis peaks of TR were
observed. The red emission band corresponding to rhodamine
with a maximum of 576 nm appeared with the increase of the
Fe3+ concentration from 0 to 15.2 equivalents; simultaneously,
the fluorescence intensity of the TR probe gradually increased.
At the same time, the UV-vis peak gradually increased with the
increase of the Hg2+ concentration from 0 to 10.96 equivalents.
These results proved that the complexes formed between the
TR probe with Fe3+ and Hg2+ led to the reconstruction of spiro-
nolactone rings in the TR probe.
3.5 Sensing mechanism
To further investigate the sensing mechanism, 1H NMR and
FT-IR experiments were carried out with the TR probe and
different concentrations of Fe3+ and Hg2+. In the 1H NMR
experiment, as shown in Fig. 7, with the increase of the Hg2+
concentration, the H1–H13 resonance peaks on rhodamine
groups shifted upfield. These upfield shifts of the proton
signal were attributed to the change in the electron density of
the rhodamine group in DMSO, which indicated that the rho-
damine group could coordinate with Hg2+. These results also
supported the spirolactam ring-opening mechanism.
The IR spectral data of TR, TR-Hg2+ and TR-Fe3+ were also
collected. As depicted in Fig. S13,† the stretching vibration
peaks of CvO and –NH on TR appeared at 1730 cm−1 and
3446 cm−1, respectively. However, when adding Hg2+ into TR,
the stretching vibration peaks of CvO and –NH of TR-Hg2+
appeared at 1724 cm−1 and 3444 cm−1, respectively. When Fe3+
was added to TR, the stretching vibration peaks of TR-Fe3+
–CvO and –NH appeared at 1721 and 3415 cm−1, respectively.
These results could be attributed to the coordination inter-
action between the mercury ions and CvO/–NH. The results
also support the ring-opening mechanism of spironolactone.
Finally, in order to study the ratio of the TR sensor to iron
ions and mercury ions, we carried out a high-resolution mass
spectrometry experiment. As shown in Fig. S11 and S12,† in
the ESI-MS of the TR sensor, a peak at m/z = 1698.4341 for (TR
+ 3Fe3+) proved the 1 : 3 complexation stoichiometry between
TR and Fe3+. Similarly, a peak at m/z = 1698.4341 for (TR +
3Hg2+) proved the 1 : 3 complexation stoichiometry between TR
and Hg2+. These outcomes might be a result of the TR probe
forming a stable complex with iron and mercury ions.
Fig. 5 The response absorption intensity of TR (2.0 × 10−5 M) was
present with different concentrations of Hg2+ in EtOH/H2O (9 : 1, v/v)
solution.
3.6 Preparation of test strips
Furthermore, the TR-based test strips were prepared by immer-
sing filter paper into the TR (EtOH/H2O, 1 × 10−3 M) solution
Fig. 6 The response fluorescence intensity of TR (2.0 × 10−5 M) was
present with different concentrations of Fe3+ in EtOH/H2O (9 : 1, v/v)
solution (Ex = 510 nm).
Fig. 7 Partial 1H NMR titration spectra (400 MHz, 298 K) of TR (10 mg
ml−1) with different fractions of Hg2+: (a) TR, (b) 0.2 eq., (c) 0.5 eq., (d)
1.0 eq., (e) 2.0 eq., and (f) 3.0 eq. in a DMSO-d6 solution.
Photochem. Photobiol. Sci.
This journal is © The Royal Society of Chemistry and Owner Societies 2020

View Article Online
Photochemical & Photobiological Sciences
Paper
3 A. Renzoni, F. Zino and E. Franchi, Mercury levels along
the food chain and risk for exposed populations, Environ.
Res., 1998, 77, 68–72.
4 V. Dujols, F. Ford and A. W. Czarnik, A long-wavelength
fluorescent chemodosimeter selective for Cu(II) ion in
water, J. Am. Chem. Soc., 1997, 119, 7386–7387.
Fig. 8 Color changes of TR-based test strips after the addition of
different concentrations of Hg2+ (from 1 × 10−1 M to 1 × 10−7 M).
5 K. C. Behera and B. Bag, Switch in ‘turn-on’ signaling pre-
ferences from Fe(III) to Hg(II) as a function of solvent and
structural variation in rhodamine-based probes, Dyes Pigm.,
2016, 135, 143–153.
6 S. Squadrone, A. Benedetto, P. Brizio, M. Prearo and
M. Abete, Mercury and selenium in European catfish
(Silurus glanis) from Northern Italian Rivers: can molar
ratio be a predictive factor for mercury toxicity in a top
predator, Chemosphere, 2015, 119, 24–30.
7 M. Hong, X. Lu, Y. Chen and D. Xu, A novel rhodamine-
based colorimetric and fluorescent sensor for Hg2+ in water
matrix and living cell, Sens. Actuators, B, 2016, 232, 28–36.
8 X. Wu, Q. Niu, T. Li, Y. Cui and S. Zhang, A highly sensitive,
selective and turn-off fluorescent sensor based on phenyla-
mine-oligothiophene derivative for rapid detection of Hg2+,
J. Lumin., 2016, 175, 182–186.
9 S. Sharma, N. Kaur, J. Singh, A. Singh, P. Raj and S. Sankar,
Salen decorated nanostructured ZnO chemosensor for the
detection of mercuric ions (Hg2+), S, Sens. Actuators, B,
2016, 232, 712–721.
and then drying in air. Interestingly, the test strips could serve
as an effective test kit for the convenient detection of Hg2+ in
water. As shown in Fig. 8, these test strips exhibited a strong
color change upon dipping into different concentrations (from
1 × 10−1 M to 1 × 10−7 M) of the Hg2+ solution, respectively.
These test strips showed distinct color changes. The lowest
response concentration of these test strips for Hg2+ was 1 ×
10−7 M.
4. Conclusion
In summary, we synthesized a novel probe molecule TR with
rhodamine hydrazine and triphenyl trimacyl chloride. TR
showed unique specificity for the detection of Hg2+ and Fe3+.
TR with a spironolactone structure is colorless and non-fluo-
rescent, whereas TR with a ring-opening amide causes chro-
mogenic and fluorescent reactions to facilitate turn-on-type
fluorescence detection. Moreover, we also made the test strip
for mercury ion detection which can be used in practical
applications.
10 J. Wang and X. Qian, A series of polyamide receptor-based
PET fluorescent sensor molecules: positively cooperative
Hg2+ ion binding with high sensitivity, Org. Lett., 2006, 17,
3721–3724.
11 L. Prodi, C. Bargossi, M. Montalti, N. Zaccheroni, N. Su,
J. S. Bradshaw, R. M. Izatt and P. B. Savage, An effective
fluorescent chemosensor for mercury ions, J. Am. Chem.
Soc., 2000, 122, 6769–6770.
Conflicts of interest
There are no conflicts to declare.
12 H. N. Kim, W. X. Ren, J. S. Kim and J. Yoon, Fluorescent
and colorimetric sensors for detection of lead, cadmium,
and mercury ions, Chem. Soc. Rev., 2012, 41, 3210–3244.
13 D. J. Shi, J. F. Zeng, J. Ye, M. Ni, Y. M. Chen and
M. Q. Chen, An effective fluorescent chemosensor for
mercury ions, J. Chin. Chem. Soc., 2017, 64, 986–992.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (NSFC) (Nos. 21662031, 21661028 and 14 P. Mahato, S. Saha, E. Suresh, R. D. Liddo, P. P. Parnigotto,
21574104), the National Natural Science Foundation of
Northwest Normal University (NWNU-LKQN-18-24) and the
Program for Chang Jiang Scholars and Innovative Research
Team in the University of Ministry of Education of China
(IRT1177).
M. T. Conconi, M. K. Kesharwani, B. Ganguly and A. Das,
Ratiometric detection of Cr3+ and Hg2+ by a naphthalimide
rhodamine based fluorescent probe, Inorg. Chem., 2012, 51,
1769–1777.
15 H. R. Yang, C. M. Han, X. J. Zhu, Y. Liu, K. Y. Zhang,
S. J. Liu, Q. Zhao, F. Y. Li and W. Huang, Upconversion
luminescent chemodosimeter based on NIR organic dye
for monitoring methylmercury In Vivo, Adv. Funct. Mater.,
2016, 26, 1945–1953.
Notes and references
1 W. F. Fitzgerald, C. H. Lamborg and C. R. Hammerschmidt, 16 K. Kaur, S. Chaudhary, S. Singh and S. Mehta, Azaindole
Marine biogeochemical cycling of mercury, Chem. Rev.,
2007, 107, 641–662.
2 T. W. Clarkson and L. Magos, The toxicology of mercury
modified imine moiety as fluorescent probe for highly sen-
sitive detection of Fe3+ ions, Sens. Actuators, B, 2016, 232,
396–401.
and its chemical compounds, Crit. Rev. Toxicol., 2006, 36, 17 Y. Wang, M. Yang, M. Zheng, X. Zhao, Y. Xie and J. Jin, 2-
609–662.
Pyridylthiazole derivative as ICT-based ratiometric fluo-
This journal is © The Royal Society of Chemistry and Owner Societies 2020
Photochem. Photobiol. Sci.

View Article Online
Paper
Photochemical & Photobiological Sciences
rescent sensor for Fe(III), Tetrahedron Lett., 2016, 57, 2399– 31 J. Li, D. Yim, W. D. Jang and J. Yoon, Recent progress in
2402.
the design and applications of fluorescence probes con-
taining crown ethers, Chem. Soc. Rev., 2017, 46, 2437–
2458.
18 J. F. Liu and Y. Qian, A novel naphthalimide-rhodamine
dye: Intramolecular fluorescence resonance energy transfer
and ratiometric chemodosimeter for Hg2+ and Fe3+, Dyes 32 J. Qin, J. Yan, B. Wang and Z. Yang, Rhodamine-enaphtha-
Pigm., 2017, 136, 782–790.
lene conjugate as a novel ratiometric fluorescent probe for
19 M. Y. Zhang, C. C. Shen, T. Jia, J. W. Qiu, H. Zhu and
recognition of Al3+, Tetrahedron Lett., 2016, 57, 1935–1939.
Y. Gao, One-step synthesis of rhodamine-based Fe3+ fluo- 33 F. Hu, B. Zheng, D. Wang, M. Liu, J. Du and D. Xiao, A
rescent probes via mannich reaction and its application in
living cell imaging, Spectrochim. Acta, Part A, 2020, 231,
118105–118112.
novel dual-switch fluorescent probe for Cr(III) ion based on
PET-FRET processes, Analyst, 2014, 139, 3607–3613.
34 M. Annadhasan and N. Rajendiran, Highly selective and
sensitive colorimetric detection of Hg(II) ions using green
synthesized silver nanoparticles, RSC Adv., 2015, 5, 94513–
94518.
35 M. Li, H. Zhou, L. Shi, D. Li and Y. Long, Ion-selective gold-
ethiol film on integrated screen printed electrodes for ana-
lysis of Cu(II) ions, Analyst, 2014, 139, 643–648.
36 L. Chang, Q. Gao, S. Liu, D. Luo, B. Han, K. Xia and
C. Zhou, A single polymer chemosensor for differential
determination of Hg2+ and Cu2+ in pure aqueous media
without mutual interference, Mater. Today Commun., 2019,
19, 148–156.
20 E. L. Mackenzie, K. Iwasaki and Y. Tsuji, Intracellular iron
transport and storage: from molecular mechanisms to
health implications, Antioxid. Redox Signal., 2008, 10, 997–
1030.
21 X. Cao, F. Zhang, Y. Bai, X. Ding and W. Sun, A highly selec-
tive “Turn-on” fluorescent probe for detection of Fe3+ in
cells, J. Fluoresc., 2019, 29, 425–434.
22 Z. Yang, M. She, B. Yin, J. Cuo, Y. Zhang and W. Sun, Three
rhodamine-based “Off-On” chemosensors with high
selectivity and sensitivity for Fe3+ imaging in living cells,
J. Org. Chem., 2012, 77, 1143–1147.
23 Y. Liu, C. X. Zhao, X. Y. Zhao, H. L. Liu, Y. B. Wang, 37 L. Bai, F. Tao, L. Li, A. Deng, C. Yan, G. Li and L. Wang, A
Y. G. Du and D. B. Wei, A selective N, N-dithenoyl-
rhodamine based fluorescent probe for Fe3+ detection
in aqueous and living cells, J. Environ. Sci., 2020, 90, 180–
188.
simple turn-on fluorescent chemosensor based on Schiff
base-terminated water-soluble polymer for selective detec-
tion of Al3+ in 100% aqueous solution, Spectrochim. Acta,
Part A, 2019, 214, 436–444.
24 H. Wang, B. B. Chen and S. Q. Zhu, Chip-based magnetic 38 L. Bai, G. Li, L. Li, M. Gao, H. Li, F. Tao, A. Deng, S. Wang
solid-phase microextraction online coupled with micro
HPLC-ICPMS for the determination of mercury species in
cells, Anal. Chem., 2016, 88, 796–802.
and L. Wang, Schiff base functionalized PEG as a high
efficient fluorescent chemosensor for Al3+ detection in
100% aqueous solution, React. Funct. Polym., 2019, 139, 1–
8.
25 G. Reddi and C. Rao, Analytical techniques for the determi-
nation of precious metals in geological and related 39 T. Geng, C. Guo, Y. Dong, M. Chen and Y. Wang, Turn-on
materials, Analyst, 1999, 124, 1531–1540.
fluorogenic and chromogenic detection of cations in com-
plete water media with poly (N-vinyl pyrrolidone) bearing
rhodamine B derivatives as polymeric chemosensor, Polym.
Adv. Technol., 2016, 27, 90–97.
26 N. Amiri, M. K. Rofouei and J. B. Ghasemi, Multivariate
optimization, preconcentration and determination of
mercury ions with (1-(p-acetyl phenyl)-3-(o-methyl-
benzoate)) triazene in aqueous samples using ICP-AES, 40 G. Li, L. Bai, F. Tao, A. Deng and L. Wang, A dual chemo-
Anal. Methods, 2016, 8, 1111–1119.
27 S. Caroli, G. Forte, A. Iamiceli and B. Galoppi,
Determination of essential and potentially toxic trace
sensor for Cu2+ and Hg2+based on a rhodamine-terminated
water-soluble polymer in 100% aqueous solution, Analyst,
2018, 143, 5395–5403.
elements in honey by inductively coupled plasma-based 41 Q. M. Wang, W. Gao, X. H. Tang, Y. Liu and Y. Li, A fluo-
techniques, Talanta, 1999, 50, 327–336.
rescence turn-on sensor for aluminum ion by a naphthal-
28 W. S. Zhong, T. Ren and L. J. Zhao, Determination of Pb
dehyde derivative, J. Mol. Struct., 2016, 1109, 127–130.
(Lead), Cd (Cadmium), Cr (Chromium), Cu (Copper), and 42 W. Y. He, R. Q. Liu, Y. H. Liao, G. H. Ding, J. L. Li, W. Liu,
Ni (Nickel) in Chinese tea with high-resolution continuum
source graphite furnace atomic absorption spectrometry,
Food Drug Anal., 2016, 24, 46–55.
L. Y. Wu, H. J. Feng, Z. F. Shi and M. X. He, A new 1,2,3-tri-
azole and its rhodamine B derivatives as a fluorescence
probe for mercury ions, Anal. Biochem., 2020, 598, 113690–
113702.
29 N. Promphet, P. Rattanarat, R. Rangkupan, O. Chailapakul
and N. Rodthongkum, An electrochemical sensor based on 43 Z. L. Yang, S. Chen, Y. X. Zhao, P. T. Zhou and Z. H. Cheng,
graphene/polyaniline/polystyrene nanoporous fibers modi-
fied electrode for simultaneous determination of lead and
cadmium, Sens. Actuators, B, 2015, 207, 526–534.
Hg2+ chromogenic and fluorescence indicators based on
rhodamine derivatives bearing thiophene group, Sens.
Actuators, B, 2018, 266, 422–428.
30 B. Kaur, N. Kaur and S. Kumar, Colorimetric metal ion 44 O. Mecit, A fast-response, highly selective, chromogenic
sensors-a comprehensive review of the years 2011-2016,
and fluorescent chemosensor for the detection of Hg2+
Coord. Chem. Rev., 2018, 358, 13–69.
ions, Sens. Actuators, B, 2017, 249, 217–228.
Photochem. Photobiol. Sci.
This journal is © The Royal Society of Chemistry and Owner Societies 2020

View Article Online
Photochemical & Photobiological Sciences
Paper
45 S. Saha, P. Mahato, U. Reddy G, E. Suresh, A. Chakrabarty, 50 K. Li, Y. Xiang, X. Y. Wang, J. Li, R. R. Hu, A. J. Tong and
M. Baidya, S. K. Ghosh and A. Das, Recognition of Hg2+
and Cr3+ in Physiological Conditions by a Rhodamine
Derivative and Its Application as a Reagent for Cell
Imaging Studies, Inorg. Chem., 2012, 51, 336–345.
B. Z. Tang, Reversible photochromic system based on rho-
damine B salicylaldehyde hydrazone metal complex, J. Am.
Chem. Soc., 2014, 136, 1643–1649.
51 K. H. Chu, Y. Zhou, Y. Fang, L. H. Wang, J. Y. Li and
C. Yao, Rhodamine-pyrene conjugated chemosensors for
ratiometric detection of Hg2+ ions: different sensing behav-
ior between a spirolactone and a spirothiolactone, Dyes
Pigm., 2013, 98, 339–346.
46 F. Abebe, T. Sutton, P. Perkins and R. Shaw, Two colori-
metric fluorescent turn–on chemosensors for detection of
Al3+and N3−: Synthesis, photophysical and computational
studies, Luminescence, 2018, 33, 1194–1201.
47 W. Y. Lin, L. Yuan, X. W. Cao, W. Tan and Y. M. Feng, A 52 D. Q. Sun, T. Lu, F. P. Xiao, X. Y. Zhu and G. Q. Sun,
Coumarin-Based Chromogenic Sensor for Transition-Metal
Ions Showing Ion-Dependent Bathochromic Shift,
Eur. J. Org. Chem., 2008, 4981–4987.
Formulation and aging resistance of modified bio-asphalt
containing high percentage of waste cooking oil residues,
J. Cleaner Prod., 2017, 161, 1203–1214.
48 C. Chen, R. Wang, L. Guo, N. Fu, H. Dong and Y. Yuan, A 53 Z. L. Yang, S. Chen, Y. X. Zhao, P. T. Zhou and Z. H. Cheng,
squaraine-based colorimetric and “Turn on” fluorescent
sensor for selective detection of Hg2+ in an Aqueous
Medium, Org. Lett., 2011, 13, 1162–1165.
Hg2+ chromogenic and fluorescence indicators based on
rhodamine derivatives bearing thiophene group, Sens.
Actuators, B, 2018, 266, 422–428.
49 Z. Guo, S. Park, J. Yoon and I. Shin, Recent progress in the 54 Analytical Methods Committee, Recommendations for the
development of near-infrared fluorescent probes for bio-
Definition, Estimation and Use of the Detection Limit,
imaging applications, Chem. Soc. Rev., 2014, 43, 16–29.
Analyst, 1987, 112, 199–204.
This journal is © The Royal Society of Chemistry and Owner Societies 2020
Photochem. Photobiol. Sci.