An expeditious method for the ultra-level chemosensing of uranyl ions †

Full text

An expeditious method for the ultra-level
chemosensing of uranyl ions†
Vishaka V. Halali and R. Geetha Balakrishna *
In this study, a new colorimetric chemosensor based on intramolecular charge transfer wasdesigned for the
qualitative and quantitative detection of uranyl ions at trace concentrations in environmental water samples.
The probe exhibited color change from colorless to red upon binding with uranyl ions at physiological pH.
This color change offered a simple, rapid and reliable method for the selective and sensitive visual detection
of trace levels of uranyl (UO
22+
) ions without any need for sophisticated instruments. The detection limit of
the synthesized chemosensor for uranyl ions was found to be 1.9 nM. This method was successfully applied
to detect trace amounts of uranyl ions in various groundwater samples. Moreover, immobilized paper strips
developed using this sensor have been demonstrated for the naked eye or on-field detection of UO
22+
ions.
1. Introduction
People's anxiety about radioactive and toxic trace metal
pollution caused due to the industrialization and develop-
ment of nuclear power plants is a serious concern and needs
to be addressed. Uranium is a major source of nuclear energy.
With the rapid development of nuclear power plants, the
demand for uranium has progressively increased, and the
spent uranium is inevitably released into the environment in
ionic (UO
22+
) form. Among the different ionic forms of
uranium, the uranyl (UO
22+
) ion is the most stable form
(aqueous) and can easily enter ground or surface water.
1–4
Moreover, exposure to uranyl ions leads to adverse impacts,
such as kidney damage, disruption of biomolecules, DNA
damage, and digestive, immune and reproductive disorders,
on human health.
5–8
The limit of contamination of uranyl
ions in drinking water is prescribed to be 30 ppb by WHO.
9
Considering the inuence of uranyl ions on various biolog-
ical systems, the real-time detection of these metal ions at
low levels is highly anticipated. Hence, methods that can
rapidly detect uranyl ions at trace levels and prevent their
utilization if the concentration is more than the desired limit
are in signicant demand. Various analytical techniques
necessitate expensive and complicated instruments for the
detection of uranyl ions in environmental and biological
samples, as reported for several decades.
10–26
Uranyl ion
sensing based on the optical phenomenon of uranyl ions is
avibranteld of research due to its easy execution, low cost,
on-eld detection, simplicity, selectivity and high
sensitivity.
21–23,27–41
A wide range of optical sensors based on coumarin,
42–45
quinolone
46–52
and nanoparticles
53–61
have been formerly used
for the sensing purpose. However, the efficacy of most of these
sensors is inadequate because of factors such as complex
synthetic procedures, strong interferences, and feeble sensi-
tivity. Our enduring interest and experience towards the
development of economic and easily available metal sensors
have inspired us to work in this direction.
62–73
In previous
studies, many optical probes have been designed to detect
uranium, and some of them have exhibited good sensitivity.
An organic probe based on rhodamine for UO
22+
ion detection
was reported for the rst time by Andersen and Hercules in
1964; however, it had a very low sensitivity level of 12 ppb.
74
In
2011, for the selective detection of Hg
2+
,Wanget al. reported
a similar ligand but with a different binding moiety.
75
These
probes are still considered highly promising due to their easy
operation and fast response. In this study, we designed a new
Schiffbase (P1) and synthesized it via a simple condensation
reaction. The obtained imine was characterized using NMR
and LCMS. The synthesized probe showed remarkably selec-
tive and sensitive probing properties for the UO
22+
ion in
MeCN at room temperature. A sensitivity level of up to
0.45 ppb could be achieved. Moreover, an immobile test strip
was developed using this probe for on-eld naked-eye detec-
tionandgroundwastewateranalysis,andshowednoveltyand
possible real-time applications.
2. Materials and methods
Details about materials, methods, synthesis of Schiffbase (P1)
(Scheme 1), LC-MS and NMR characterizations of P1 (Fig. S1
and S2†), measurement of the optical properties of P1, and
Centre for Nano and Material Sciences, Jain University, Jain Global Campus,
Kanakapura, Ramanagaram, Bangalore 562112, India. E-mail: br.geetha@
jainuniversity.ac.in
†Electronic supplementary information (ESI) available. See DOI:
10.1039/c9ay02715g
Cite this: DOI: 10.1039/c9ay02715g
Received 19th December 2019
Accepted 30th January 2020
DOI: 10.1039/c9ay02715g
rsc.li/methods
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detection of UO
22+
ions in groundwater have been explained in
the ESI 1–5.†
3. Results and discussion
3.1 Colorimetric sensing of P1
The absorption spectra of the probe P1 (50 mM) were obtained in
the presence of different metal ions in MeCN solvent. The Schiff
base P1 with UO
22+
ions exhibited an absorption maximum at
525 nm, which could be attributed to the p–p*charge-transfer
transitions (Fig. 1(a)). The concentration of the probe was
optimized at 100 mM and maintained throughout this study. P1
showed an identiable color change from colorless to red only
for the UO
22+
ions (50 mM) in MeCN. However, no signicant
changes were observed in the absorption spectra aer the
addition of various metal ions, such as Ca
2+
,Co
2+
,Pb
2+
,Ag
+
,
Mg
2+
,Cd
2+
,Al
3+
,UO
22+
,Hg
2+
,Cu
2+
,Zn
2+
,Ni
2+
,Cr
3+
and Fe
2+
ions, at a 100 mM concentration. The interference effect of the
coexistence of metal ions was also investigated, and the
selectivity of P1 towards the UO
22+
ion was very clearly evident.
The competing metal ions did not show any interference. These
results demonstrate that the probe retains its selectivity even in
the presence of competing ions (Fig. 1(b)). The easily observable
color change of P1 in the presence of UO
22+
ions indicates the
potential efficacy of P1 for the “naked eye”detection of UO
22+
(Fig. 1(c) and inset of Fig. 1(d)). The sensitivity of the probe was
investigated via absorbance titrations. A gradual increase in the
absorption intensity was observed because with an increase in
the concentration of the UO
22+
ions in P1 (Fig. 1(d)), the P1 +
UO
22+
ion complex was formed, and the limit of detection was
found to be 1.9 nM (Fig. 1(e)). The synthesized probe did not
display any uorescence response upon binding with UO
22+
ions. The probe turned pink upon binding with the target and
hence was used only as a colorimetric sensor.
Furthermore, the stoichiometry of the metal complex formed
between the Schiffbase P1 and the metal ion UO
22+
was esti-
mated by the Job's plot method. The study was carried out using
a UV-vis spectrophotometer possessing a different relative
Scheme 1 Synthesis scheme for P1.
Fig. 1 (a) UV-vis absorption spectra of P1 with individual metal ions (50 mM). (b) Interference study of P1 using a mixture of various metal ions. (c)
Digital photograph of the naked eye detection of P1. (d) Titration spectra of P1 with the increasing concentration of UO
22+
; inset: L–R digital
photographs of P1 and P1 +UO
22+
. (e) Limit of detection calibration graph.
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molar ratio of the probe and the metal ion. As shown in Fig. 2(a),
the maximum of the curve is reached at a 0.5 molar ratio, rep-
resenting a 1 : 1 stoichiometry of the complex. Moreover, this
stoichiometry was conrmed by LC-MS (Fig. S3†). The associa-
tion constant for the P1 +UO
22+
ion complex was determined by
the Benesi–Hildebrand plot via an absorbance experiment. The
association constant of the P1 +UO
22+
ion complex was found to
be 2.56 10
5
M
1
, exhibiting the high binding nature of the
probe (Fig. 2(b)).
To examine the stability of the sensor complex P1 +UO
22+
ions at different pH values, absorption spectra were recorded in
the MeCN solution by adjusting the pH value using HCl and
NaOH. It is evident from Fig. 3(a) that the receptor P1 is effective
in the pH range 6–7. At pH < 3, P1 itself shows a color change
due to the opening of the spirolactam ring under the inuence
of the protonation induced by highly acidic pH; moreover, P1
tends to lose its coordination affinity at pH > 7. Hence, pH 6–7is
the optimum range, indicating that the probe P1 can be easily
Fig. 2 (a) Job's plot and (b) Benesi–Hildebrand plot.
Fig. 3 (a) Maximum absorption intensity of P1 at 525 nm in the absence and presence of UO
22+
at different pH values, (b) effect of different
anions on the absorption of the P1 +UO
22+
complex, (c) UV-vis titration spectra of P1 +UO
22+
after the sequential addition of the 1 : 1 AcO

solution to the complex; inset: images of P1,P1 +UO
22+
and P1 +UO
22+
+ AcO

from L–R.
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used for the estimation of UO
22+
ions in environmental samples
at physiological pH. Since the reversible nature of the sensor is
vital for its practical applications, we have evaluated the effect of
various anions on the reversibility of the P1 +UO
22+
complex
ions to regenerate P1.
P1 could be successfully recovered by the addition of AcO

ions to the P1 +UO
22+
ion solution mixture, as shown in
Fig. 3(b). In addition, the binding reversibility of the UO
22+
ions
to P1 was proven in the presence of aqueous sodium acetate via
UV-vis spectral experiments. To gain more understanding of the
abovementioned concept, we carried out UV-vis titration for this
complex. As shown in Fig. 3(c), aer the incremental addition of
the AcO

ions, the absorption intensity at 525 nm gradually
decreased; this demonstrated the regeneration of the free probe
P1. This observed decrease in the absorption intensity dis-
continued upon the addition of 65 mM AcO

ions, suggesting
the complete dissociation of the UO
22+
ion from the receptor
site.
It is very clear from the UO
22+
ion binding studies that the
binding of the probe to the UO
22+
ion leads to a color change
due to the breaking of the spirolactam ring of the probe. As
demonstrated in Scheme 2, the addition of the UO
22+
ion
induced a colorimetric “On”response, producing a red color.
Moreover, the added AcO

could react with the UO
22+
ion and
prompt a colorimetric change from red to colorless. The
13
C
NMR spectra shown in Fig. S4 of the ESI†conrmed the
reversible ring closure of lactum. The absorption peak at
525 nm disappeared upon the addition of AcO

, forming uranyl
acetate (Fig. 3(c) inset). Then, the initial absorption intensity
was regained upon the addition of the UO
22+
ion to the mixture,
and this process was repeated at least ve times to suggest the
recyclability of the chemosensor (Fig. S5†).
To understand the sensing mechanism, we conducted the
ATR-IR and LC-MS analyses. ATR-IR was used to investigate the
impact of the C]O and C]N bonds on the binding of the
UO
22+
ions. The peaks at 1702 cm
1
and 1605 cm
1
correspond
to the characteristic frequencies of the C]O and C]N bonds of
the rhodamine moiety. Upon complexation of the probe with
UO
22+
, the peaks of the C]O and C]N bonds shied to
1711 cm
1
and 1614 cm
1
, respectively, suggesting the
successful binding of UO
22+
ions with the oxygen and nitrogen
atoms (Fig. S6†). In addition, to investigate the colorimetric
features, the LC-MS spectrum of the system was analyzed. The
peak at 370.04 conrms the presence of UO
22+
ions in the
complex aer the addition of UO
22+
ions to the probe solution
(mass of P1: 583.24) (Fig. S1 & S3†).
4. Application of the chemosensor P1
To evaluate the performance of the proposed chemosensor, real
sample analysis was performed because of the possible utili-
zation of this chemosensor in the detection of uranyl ions in
naturally occurring substances. The real-time application of the
probe was appraised through the determination of the
concentration of UO
22+
ions in groundwater samples. The
groundwater samples were examined for the UO
22+
ions, and
the results were validated by ICP-OES methods. Samples were
examined in triplicate. The results obtained using this chemo-
sensor are summarized in Table 1. It can be observed from
Table 1 that the results obtained for water samples are in good
agreement with those obtained using ICP-OES. Hence, the
designed colorimetric probe has good practical viability in the
quantitative detection of uranyl ions in different groundwater
samples.
5. Portable strips for the instant
detection of UO
22+
ions
Guaranteeing the purity of drinking water and consumable
food materials in remote areas (where test centers are not
accessible) is an inspiring task. Hence, herein, portable
strips were prepared for the fast track on-eld detection of
UO
22+
ions. Initially, a part of the paper strip was soaked in
the MeCN solution of P1 and then dried in air before its use
for the detection of UO
22+
ions in groundwater. A divergent
color change was observed instantly upon dipping the test
strips in the UO
22+
ion solution (Fig. 4). The UO
22+
ions
present in the solution selectively transformed the test-strips
from colorless to red. This newly developed chemosensor
system affords an alternative technique for the detection of
a range of harmful metal ions that contaminate natural
groundwater sources.
Scheme 2 Proposed mechanism for the changes in P1 upon the addition of UO
22+
and AcO

.
Table 1 Determination of UO
22+
in groundwater real samples
a,b
Samples
ICP-OES method Present method
UO
22+
found RSD (%) UO
22+
found RSD (%)
Sample 1 1.17 10
5
M 1.56 1.12 10
5
M 1.68
Sample 2 1.58 10
5
M 1.20 1.53 10
5
M 0.92
a
Sample 1: collected from Magadi Lake, Chickmagalur district.
b
Sample 2: collected from Chickballapur Lake, Kolar district.
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6. Conclusion
In summary, the synthesized chemosensor exhibited excep-
tional selectivity and sensitivity for the detection of UO
22+
ions
in groundwater samples. The sensitivity of the probe towards
uranyl ions was most adequate in the biological pH range. The
probe P1 exhibited a sensitivity of about 1.9 nM (0.45 ppb).
Moreover, the probe showed reversibility upon interaction with
an acetate moiety. In addition, we validated this detection of
UO
22+
ions using portable strips. The implication of this study
mainly relies on the application of this colorimetric chemo-
sensor in the fast track on-eld detection of UO
22+
ions in
groundwater samples.
Conflicts of interest
There are no conicts to declare.
Acknowledgements
The authors acknowledge BRNS, DAE, India, for nancial
assistance (Project Sanction No. 37(2)14/06/2014-BRNS), the
Institute of Excellence, Vijnana Bhavana, University of Mysore,
India, for providing the Nuclear Magnetic Resonance (NMR)
and liquid chromatography (LC-MS) facility, and TUV India
Private Limited, Bengaluru, India, for providing the ICP-OES
instrumentation facility.
References
1 J. Maynadi´
e, J.-C. Berthet, P. Thu´
ery and M. Ephritikhine,
Bent and Linear Uranium(IV) Metallocenes with Terminal
and Bridging Cyanide Ligands, Organometallics, 2007, 26,
4585–4591.
2 J. Wena, Z. Huanga, S. Hu, S. Li, W. Li and X. Wang,
Aggregation-induced emission active tetraphenylethene-
based sensor for uranyl ion detection, J. Hazard. Mater.,
2016, 318, 363–370.
3 A. Asica, et al., Chemical toxicity and radioactivity of depleted
uranium: the evidence from in vivo and in vitro studies,
Environ. Res., 2017, 156, 665–673.
4 W. Liu, X. Dai, Z. Bai, Y. Wang, Z. Yang, L. Zhang, L. Xu,
L. Chen, Y. Li, J. Diwu, J. Wang, R. Zhou, Z. Chai and
S. Wang, Highly Sensitive and Selective Uranium Detection
in Natural Water Systems Using a Luminescent
Mesoporous Metal–Organic Framework Equipped with
Abundant Lewis Basic Sites: A Combined Batch, X-ray
Absorption Spectroscopy, and First Principle Simulation
Investigation, Environ. Sci. Technol., 2017, 51(7), 3911–3921.
5 K. L. Cooper, et al., Inhibition of poly(ADP-ribose)
polymerase-1 and DNA repair by uranium, Toxicol. Appl.
Pharmacol., 2016, 291,13–20.
6 M. Sun, et al., A spectroscopic study of uranyl-cytochrome
b5/cytochrome c interactions, Spectrochimica Acta, Part A:
Molecular and Biomolecular Spectroscopy, 2014, 118, 130–137.
7 S. Fukuda, Chelating Agents Used for Plutonium and
Uranium Removal in Radiation Emergency Medicine, Curr.
Med. Chem., 2005, 12, 2765–2770.
8 P. A. Bryant, Chemical toxicity and radiological health
detriment associated with the inhalation of various
enrichments of uranium, J. Radiol. Prot., 2014, 34(1), N1–N6.
9 S. K. Guin, A. S. Ambolikar, J. P. Guin and S. Neogy, Exploring
the Excellent Photophysical and Electrochemical Properties
of Graphene Quantum Dots for Complementary Sensing of
Uranium, Sens. Actuators, B, 2018, 272, 559–573.
10 J. J. Gonzalez, D. Oropeza, X. Mao and R. E. Russo,
Assessment of the precision and accuracy of thorium
(232Th) and uranium (238U) measured by quadrupole
based inductively coupled plasma-mass spectrometry using
liquid nebulization, nanosecond and femtosecond laser
ablation, J. Anal. At. Spectrom., 2008, 23, 229–234.
11 K. Chandrasekaran, D. Karunasagar and J. Arunachalam,
Dispersive liquid–liquid micro extraction of uranium(VI)
from groundwater and seawater samples and
determination by inductively coupled plasma–optical
emission spectrometry and ow injection–inductively
coupled plasma mass spectrometry, Anal. Methods, 2011, 3,
2140–2147.
12 C. Moser, R. Kautenburger and H. P. Beck, Complexation of
europium and uranium by humic acids analyzed by capillary
electrophoresis-inductively coupled plasma mass
spectrometry, Electrophoresis, 2012, 3(9–10), 1482–1487.
13 S. Ali, Atomic absorption spectrometric and
spectrophotometric trace analysis of uranium in
environmental samples with furylacrylohydroxamic acid
and n-p-methoxy phenyl-2-4-(2-pyridylazo) resorcinol, Int. J.
Environ. Anal. Chem., 1989, 36(3), 163–172.
14 M. Branica and M. Mlakar, Stripping voltammetric
determination of trace levels of uranium by synergic
adsorption, Anal. Chim. Acta, 1989, 221, 279–287.
15 A. K. Brown, J. Liu, Y. He and Y. Lu, Biochemical
Characterization of a Uranyl Ion-Specic DNAzyme,
ChemBioChem, 2009, 10(3), 486–492.
16 A. Safavi and M. Bagheri, A novel optical sensor for uranium
determination, Anal. Chim. Acta, 2005, 530(1), 55–60.
17 Y. Luo, Y. Zhang, L. Xu, L. Wang, G. Wen, A. Liang and
Z. Jiang, Colorimetric sensing of trace UO22+ by using
nanogold-seeded nucleation amplication and label-free
DNAzyme cleavage reaction, Analyst, 2012, 137(8), 1866.
18 A. Becker, H. Tobias and D. Mandler, Electrochemical
Determination of Uranyl Ions Using a Self-Assembled
Monolayer, Anal. Chem., 2009, 81, 8627–8631.
Fig. 4 Photograph of a portable strip of the chemosensor P1 during
the detection of UO
22+
.
This journal is © The Royal Society of Chemistry 2020 Anal. Methods
Paper Analytical Methods
Published on 13 February 2020. Downloaded by MURDOCH UNIVERSITY LIBRARY on 2/14/2020 5:41:10 PM.
View Article Online

19 R. Zadeh kakhki and D. Ammann, Selective uranyl cation
detection by polymeric ion selective electrode based on
benzo-15-crown-5, Mater. Sci. Eng., C, 2011, 31, 1637–1642.
20 F. Alpat, K. ¨
Ozdemir and S. Kılınç Alpat, Voltammetric
Determination of Epinephrine in Pharmaceutical Sample
with a Tyrosinase Nanobiosensor, J. Sens., 2016, 2016,1–9.
21 B. J. Sanghavi, et al., Biomimetic sensor for certain
catecholamines employing copper(II) complex and silver
nanoparticle modied glassy carbon paste electrode,
Biosens. Bioelectron., 2013, 39, 124–132.
22 B. J. Sanghavi, S. Sitaula, M. H. Griep, S. P. Karna, M. F. Ali
and N. S. Swami, Real-Time Electrochemical Monitoring of
Adenosine Triphosphate in the Picomolar to Micromolar
Range Using Graphene-Modied Electrodes, Anal. Chem.,
2013, 85(17), 8158–8165.
23 M. Lee, H. J. Kim, S. Yoon, N. Park and J. S. Kim, Metal Ion
Induced FRET OFF–ON in Tren/Dansyl-Appended
Rhodamine, Org. Lett., 2007, 10(2), 213–216.
24 J. Ejnik, et al., Determination of the Isotopic Composition of
Uranium in Urine by Inductively Coupled Plasma Mass
Spectrometry, Health Phys., 2000, 78, 143–146.
25 P. Mahato, et al., An overview of the recent developments on
Hg2+ recognition, RSC Adv., 2014, 4(68), 36140–36174.
26 J. L. Atwood, Comprehensive supramolecular chemistry II,
Elsevier, 2017.
27 B. Bodenant, T. Weil, M. Businelli-Pourcel, F. Fages,
B. Barbe, I. Pianet and M. Laguerre, Synthesis and Solution
Structure Analysis of a Bispyrenyl Bishydroxamate Calix[4]
arene-Based Receptor, a Fluorescent Chemosensor for
Cu2+ and Ni2+ Metal Ions, J. Org. Chem., 1999, 1999(64),
7034–7039.
28 D. W. Cho, M. Fujitsuka, K. H. Choi, M. J. Park, U. C. Yoon
and T. Majima, Intramolecular Exciplex and
Intermolecular Excimer Formation of 1,8-Naphthalimide-
Linker-Phenothiazine Dyads, J. Phys. Chem. B, 2006, 110,
4576–4582.
29 T. Gunnlaugsson, B. Bichell and C. Nolan, Fluorescent PET
chemosensors for lithium, Tetrahedron, 2004, 60(27), 5799–5806.
30 H. He, K. Jenkins and Chao Lin, A uorescent chemosensor
for calcium with excellent storage stability in water, Anal.
Chim. Acta, 2008, 611(2), 197–204.
31 P. Nandhikonda, M. P. Begaye and M. D. Heagy, Highly
water-soluble, OFF–ON, dual uorescent probes for
sodium and potassium ions, Tetrahedron Lett., 2009, 50,
2459–2461.
32 L. Ma, H. Li and Y. Wua, A pyrene-containing uorescent
sensor with high selectivity for lead(II) ion in water with
dual illustration of ground-state dimer, Sens. Actuators, B,
2009, 143,25–29.
33 M. R. Ganjali, B. Veismohammadi, M. Hosseini and
P. Norouzi, A new Tb3+-selective uorescent sensor based
on 2-(5-(dimethylamino)naphthalen-1-ylsulfonyl)-N-
henylhydrazinecarbothioamide, Spectrochimica Acta, Part A:
Molecular and Biomolecular Spectroscopy, 2009, 74, 575–578.
34 C. R. Lohani and K.-H. Lee, The effect of absorbance of Fe3+
on the detection of Fe3+ by uorescent chemical sensors,
Sens. Actuators, B, 2010, 143, 649–654.
35 F. A. Abebe, C. S. Eribal, G. Ramakrishna and E. Sinn, A
‘turn-on’uorescent sensor for the selective detection of
cobalt and nickel ions in aqueous media, Tetrahedron Lett.,
2011, 52, 5554–5558.
36 Y. Zhaoa, B. Zheng, J. Dua, Dan Xiaoa and L. Yanga, A
uorescent “turn-on”probe for the dual-channel detection
of Hg(II) and Mg(II) and its application of imaging in
living cells, Talanta, 2011, 85, 2194–2201.
37 A. Banerjee, A. Sahana, S. Das, S. Lohar, S. Guha, B. Sarkar,
S. K. Mukhopadhyay, A. K. Mukherjee and D. Das, A
naphthalene exciplex based Al3+ selective on-type
uorescent probe for living cells at the physiological pH
range: experimental and computational studies, Analyst,
2012, 137(9), 2166.
38 M. Hosseini, M. R. Ganjali, F. Aboufazeli, F. Faridbod,
H. Goldooz, A. Badiei and P. Norouzi, A selective
uorescent bulk sensor for lutetium based on hexagonal
mesoporous structures, Sens. Actuators, B, 2013, 184,93–99.
39 S. Lohar, A. Banerjee, A. Sahana, A. Banik,
S. K. Mukhopadhyay and D. Das, A rhodamine–
naphthalene conjugate as a FRET based sensor for Cr3+
and Fe3+ with cell staining application, Anal. Methods,
2013, 5(2), 442–445.
40 A. Kamal, N. Sharma, V. Bhalla, R. Manoj Kumar and
M. Kumar, Electrochemical sensing of iron(III) by using
rhodamine dimer as an electroactive material, Talanta, 2014,
128, 422–427.
41 V. K. Gupta, A. Singh and L. K. Kumawat, A Turn-On
Fluorescent Chemosensor for Zn2+ Ions based on
Antipyrine schiffbase, Sens. Actuators, B, 2014, 204, 507–514.
42 L. Wang, D. Ye and D. Cao, A novel coumarin Schiff-base as
a Ni(II) ion colorimetric sensor, Spectrochimica Acta, Part A:
Molecular and Biomolecular Spectroscopy, 2012, 90,40–44.
43 X. Liu, Q. Lin, T.-B. Wei and Y.-M. Zhang, A highly selective
colorimetric chemosensor for detection of nickel ions in
aqueous solution, New J. Chem., 2014, 38(4), 1418–1423.
44 F. Ge, H. Ye, H. Zhang and B.-X. Zhao, A novel ratiometric
probe based on rhodamine B and coumarin for selective
recognition of Fe(III) in aqueous solution, Dyes Pigm.,
2013, 99, 661–665.
45 N. Roy, A. Dutta, P. M. Pradip, C. Paul and T. S. Singh, A new
coumarin based dual functional chemosensor for
colorimetric detection of Fe3+ and uorescence turn-on
response of Zn2+, Sens. Actuators, B, 2016, 236, 719–731.
46 H. M. Park, et al., Fluorescent chemosensor based-on
naphthol–quinoline for selective detectio of aluminum
ions, Tetrahedron Lett., 2011, 52, 5581–5584.
47 M. Li, H.-Y. Lu, R.-L. Liu, J.-D. Chen and C.-F. Chen, Turn-On
Fluorescent Sensor for Selective Detection of Zn2+, Cd2+,
and Hg2+ in Water, J. Org. Chem., 2012, 77(7), 3670–3673.
48 X. Zhou, P. Li, Z. Shi, X. Tang, C. Chen and W. Liu, A Highly
Selective Fluorescent Sensor for Distinguishing Cadmium
from Zinc Ions Based on a Quinoline Platform, Inorg.
Chem., 2012, 51(17), 9226–9231.
49 X. Wan, S. Yao, H. Liu and Y. Yao, Selective uorescence
sensing of Hg2+ and Zn2+ ions through dual independent
channels based on the site-specic functionalization of
Anal. Methods This journal is © The Royal Society of Chemistry 2020
Analytical Methods Paper
Published on 13 February 2020. Downloaded by MURDOCH UNIVERSITY LIBRARY on 2/14/2020 5:41:10 PM.
View Article Online

mesoporous silica nanoparticles, J. Mater. Chem. A, 2013,
1(35), 10505.
50 L. Tang, D. Wu, Z. Huang and Y. Bian, A uorescent sensor
based on binaphthol-quinoline Schiffbase for relay
recognition of Zn2+ and oxalate in aqueous media, J.
Chem. Sci., 2016, 128(8), 1337–1343.
51 Z. Wang, H. Wang, T. Meng, E. Hao and L. Jiao, Synthetically
simple, click-generated quinoline-based Fe3+ sensors,
Methods Appl. Fluoresc., 2017, 5(2), 024015.
52 H. Liu, Y. Tan, Q. Dai, H. Liang, J. Song, J. Qu and
W.-Y. Wong, A simple amide uorescent sensor based on
quinoline for selective and sensitive recognition of zinc(II)
and bioimaging in living cells, Dyes Pigm., 2018, 158, 312–
318.
53 S. Dutta, C. Ray, S. Sarkar, M. Pradhan, Y. Negishi and T. Pal,
Silver Nanoparticle Decorated Reduced Graphene Oxide
(rGO) Nanosheet: A Platform for SERS Based Low-Level
Detection of Uranyl Ion, ACS Appl. Mater. Interfaces, 2013,
5(17), 8724–8732.
54 P. Wu, K. Hwang, T. Lan and Y. Lu, A DNAzyme-Gold
Nanoparticle Probe for Uranyl Ion in Living Cells, J. Am.
Chem. Soc., 2013, 135(14), 5254–5257.
55 Y. Kim, R. C. Johnson and J. T. Hupp, Gold Nanoparticle-
Based Sensing of “Spectroscopically Silent”Heavy Metal
Ions, Nano Lett., 2001, 1(4), 165–167.
56 B. Zhou, L. F. Shi, Y.-S. Wang, H.-X. Yang, J.-H. Xue, L. Liu,
Y.-S. Wang, J.-C. Wang and J.-C. Yin, Resonance light
scattering determination of uranyl based on labeled
DNAzyme–gold nanoparticle system, Spectrochimica Acta,
Part A: Molecular and Biomolecular Spectroscopy, 2013, 110,
419–424.
57 M. Li, H. Gou, I. Al-Ogaidi and N. Wu, Nanostructured
Sensors for Detection of Heavy Metals: A Review, ACS
Sustainable Chem. Eng., 2013, 1(7), 713–723.
58 A. Bigdeli, et al., Nanoparticle-Based Optical Sensor Arrays,
Nanoscale, 2017, 9(43), 16546–16563.
59 I. A. A. Terra, L. A. Mercante, R. S. Andre and D. S. Correa,
Fluorescent and Colorimetric Electrospun Nanobers for
Heavy-Metal Sensing, Biosensors, 2017, 7(4), 61.
60 N. Ullah, M. Mansha, I. Khan and A. Qurashi, Nanomaterial-
based optical chemical sensors for the detection of heavy
metals in water: recent advances and challenges, TrAC,
Trends Anal. Chem., 2018, 100, 155–166.
61 Z. Jiang, D. Yao, G. Wen, T. Li, B. Chen and A. Liang, A Label-
Free Nanogold DNAzyme-Cleaved Surface-Enhanced
Resonance Raman Scattering Method for Trace UO22+
Using Rhodamine 6G as Probe, Plasmonics, 2013, 8(2), 803–
810.
62 H. R. Chandan, M. Venkataramana, M. D. Kurkuri and
R. Geetha Balakrishna, Simple Quantum Dot Bioprobe/
Label for Sensitive Detection of Staphylococcus aureus
TNase, Sens. Actuators, B, 2016, 222, 1201–1208.
63 H. R. Chandan, J. D. Schiffman and R. Geetha Balakrishnaa,
Quantum dots as uorescent probes: synthesis, surface
chemistry, energy transfer mechanisms, and applications,
Sens. Actuators, B, 2018, 258, 1191–1214.
64 C. H. Ravikumar, M. I. Gowda and R. Geetha Balakrishna, An
“OFF–ON”quantum dot–graphene oxide bioprobe for
sensitive detection of micrococcal nuclease of
Staphylococcus aureus, Analyst, 2019, 144, 3999.
65 H. V. Vishaka, et al., Paper based eld deployable sensor for
naked eye monitoring of copper(II) ions; elucidation of
binding mechanism by DFT studies, Spectrochimica Acta,
Part A: Molecular and Biomolecular Spectroscopy, 2019, 223,
117291.
66 C. Hunsur Ravikumar, Synergistic effect of binary ligands on
nucleation and growth/size effect of nanocrystals: studies on
reusability of the solvent, J. Mater. Res., 2014, 29, 1556–1564.
67 L. P. D'Souza, V. Amoli, H. R. Chandana, A. K. Sinha,
R. K. Pai and G. R. Balakrishna, Atomic force microscopic
study of nanoscale interaction between N719 dye and CdSe
quantum dot in hybrid solar cells and their enhanced
open circuit potential, Sol. Energy, 2015, 116,25–36.
68 V. H. Vishaka, M. Saxena, R. Geetha Balakrishna, S. Latiyan
and S. Jainc, Remarkably selective biocompatible turn-on
uorescent probe for detection of Fe3+ in human blood
samples and cells, RSC Adv., 2019, 9, 27439–27448.
69 S. Adhikari, S. Mandal, A. Ghosh, S. Guria, A. Pal, A. Adhikary
and D. Das, A FRET based colorimetric and uorescence
probe for selective detection of Bi3+ ion and live cell
imaging, J. Photochem. Photobiol., A, 2018, 360,26–33.
70 G. Bartwal, K. Aggarwal and J. M. Khurana, A highly selective
pH switchable colorimetric uorescent rhodamine
functionalized azo-phenol derivative for thorium
recognition up to nano molar level in semi-aqueous media:
implication towards multiple logic gates, J. Hazard. Mater.,
2018, 360,51–61.
71 X. Wu, Q. Huang, Y. Mao, X. Wang, Y. Wang, Q. Hu, H. Wang
and X. Wang, Sensors for determination of uranium:
a review, TrAC, Trends Anal. Chem., 2019, 118,89–111.
72 W. Hea and D. Huaa, Spectrographic sensors for uranyl
detection in the environment, Talanta, 2019, 201, 317–329.
73 X. Chen, L. Peng, M. Feng, Y. Xiang, A. Tong, L. He, B. Liu
and Y. Tang, An aggregation induced emission
enhancement-based ratiometric uorescent sensor for
detecting trace uranyl ion (UO22+) and the application in
living cells imaging, J. Lumin., 2017, 186, 301–306.
74 N. R. Andersen and D. M. Hercules, Fluorometric
Determination of Uranium with Rhodamine B, Anal.
Chem., 1964, 36, 11, 2138–2141.
75 Y. Wang, et al., A cell compatible uorescent chemosensor
for Hg2+ based on a novel rhodamine derivative that
works as a molecular keypad lock, RSC Adv., 2011, 1, 1294–
1300.
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