A novel ratiometric fluorescent probe for sensitive and selective detection of Cu2+ based on Boranil derivatives

Article abstract of DOI:10.1016/j.ica.2021.120438

A novel ratiometric fluorescent probe 1, consisting of Boranil derivative as the fluorophore and picolinate as the recognition site for Cu²⁺, was designed and synthesized. 1 was found to display ratiometric response while interacting with Cu²⁺ by undergoing a Cu²⁺-promoted hydrolysis of the picolinate moiety for the release of its precursor, 2. We observed that 1 not only showed quick response time (within 10 min), high sensitivity (detection limit of 0.52 μM), and high selectivity for Cu²⁺ over other metal ions, but also allowed us to detect Cu²⁺ in a convenient way of observing fluorescence color change under a 365 nm UV lamp using naked eyes. Our study introduced the first ratiometric fluorescent probe for Cu²⁺ based on Boranil derivative.

Full text of DOI:10.1016/j.ica.2021.120438

Inorganica Chimica Acta 524 (2021) 120438
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journal homepage: www.elsevier.com/locate/ica
Research paper
A novel ratiometric fluorescent probe for sensitive and selective detection
of Cu2+ based on Boranil derivatives
,
Dongjian Zhua *, Shilei Jiangb, Wei Zhaoc, Xiaowei Yana, Wei Xiea, Yuhao Xionga,
,
*
Sujuan Wanga, Wen Caia, Youjun Gaod, Aishan Rena
a Research Institute of Food Science and Engineering Technology, College of Food and Bioengineering, Hezhou University, Hezhou 542899, PR China
b Yiwu Inspection and Quarantine Academy of Science and Technology, Yiwu 322000, PR China
c Key Laboratory of Cluster Science of Ministry of Education, Key Laboratory of Medical Molecule Science and Pharmaceutics Engineering, Ministry of Industry and
Information Technology, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 102488, PR China
d College of Materials and Chemical Engineering, Hezhou University, Hezhou 542899, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords:
A novel ratiometric fluorescent probe 1, consisting of Boranil derivative as the fluorophore and picolinate as the
recognition site for Cu2+, was designed and synthesized. 1 was found to display ratiometric response while
interacting with Cu2+ by undergoing a Cu2+-promoted hydrolysis of the picolinate moiety for the release of its
precursor, 2. We observed that 1 not only showed quick response time (within 10 min), high sensitivity
Ratiometric
Fluorescent probe
Cu2+
Boranil derivatives
(detection limit of 0.52
μ
M), and high selectivity for Cu2+ over other metal ions, but also allowed us to detect
Cu2+ in a convenient way of observing fluorescence color change under a 365 nm UV lamp using naked eyes. Our
study introduced the first ratiometric fluorescent probe for Cu2+ based on Boranil derivative.
1. Introduction
Agency (EPA) and Administration of the People’s Republic of China are
30
μM [12], 20 μM [13] and 15.7 μM [4], respectively. Due to its
Development of techniques for monitoring heavy and transition
metal cations have attracted increasing attention in recent years [1].
Among various heavy and transition metal cations, copper ion (Cu2+),
being the third most abundant cations in human body, is playing crucial
roles in physiological processes [2]. It is essential to keep an appropriate
amount of Cu2+ in order to keep regular Cu2+-mediated processes in
lives. Daily doses of Cu2+ suggested by the National Research Council
are 0.4 mg to 0.6 mg, 1.5 mg to 2.5 mg and 1.5 mg to 3.0 mg for infants,
children and adults, respectively [3]. The average Cu2+ concentration is
physiological roles as well as environmental concerns, it is important to
develop efficient methods of detecting Cu2+ in biological and environ-
mental systems.
Up to now, many conventional analytical technologies have been
developed to detect Cu2+ in quantitative manner, e.g., inductively
coupled plasma mass spectrometry (ICP-MS) [14], atomic absorption
spectrometry (AAS) [15], atomic emission spectrometry (AES) [16] and
electrochemical [17]. However, these methods normally require
expensive instruments, tedious sample preparation procedures, skilled
operators, long time consumption. By contrast, use of fluorescent probes
offers an efficient way to detect Cu2+ with excellent advantages, e.g.,
specificity, high sensitivity, simple instrumentation, easy operation,
limited from 15.7
μ
M to 23.6
μ
M in blood [4]. However, aberrant Cu2+
levels, both deficiency and excess, can cause serious diseases. Specif-
ically, Cu2+ deficiency can result in anemia [5], myelopathy [6] and
coronary heart disease [7], neurodegenerative diseases such as Alz-
heimer’s [8], Parkinson’s [9], Wilson’s [10] and Menke’s [11] are
associated with excessive Cu2+. Owing to extensive use of Cu-mediated
materials in industry and agriculture, continuous discharge of Cu2+ may
cause significant environmental contaminations. For these reasons, the
maximum allowable levels (MAL) of Cu2+ in drinking water defined by
World Health Organization (WHO), U.S. Environmental Protection
real-time monitoring with rapid response [18]. Hence, numerous Cu2+
-
selective fluorescent probes have been developed [19–36,39–41].
Typically, two strategies are employed for the design of the reported
Cu2+ fluorescent probes, coordination-based and reaction-based ap-
proaches. Due to the inherent fluorescence quenching property of
paramagnetic Cu2+, coordination-based fluorescent probes [19–24]
usually exhibit turn-off fluorescence signaling upon chelating with Cu2+
,
* Corresponding authors.
E-mail addresses: zhudongjian@iccas.ac.cn (D. Zhu), rash_yudi@163.com (A. Ren).
https://doi.org/10.1016/j.ica.2021.120438
Received 10 February 2021; Received in revised form 26 April 2021; Accepted 3 May 2021
Available online 6 May 2021
0020-1693/© 2021 Elsevier B.V. All rights reserved.

D. Zhu et al.
Inorganica Chimica Acta 524 (2021) 120438
Scheme 1. Synthetic strategy for 1 and proposed sensing mechanism for Cu2+
.
yet may cause false-positive results. On the contrary, reaction-based
strategy is an effective way to construct turn-on fluorescent probes
through Cu2+-promoted irreversible chemical reactions, including hy-
drolysis [25–31], oxidation [32–34], Heck [35], and Click [36] reaction.
The reaction-based strategy allows for desirable fluorescence enhance-
ment signal with high sensitivity. Actually, it is an attractive strategy to
design ratiometric fluorescent probes for Cu2+. Since intensity-based
either turn-off or turn-on fluorescent probes are easily influenced by
many factors, including probe concentration, instrumental efficiency,
excitation intensity and environmental variations. In contrast, ratio-
metric fluorescent probes can eliminate most or all interferences by self-
calibration of two different emission bands [37–41]. However, to the
best of knowledge, only few ratiometric fluorescent probes for Cu2+
have been reported [39–41].
a novel fluorescent probe 1 with Boranil derivative as the fluorophore
and picolinate as the recognition site for Cu2+, as shown in Scheme 1.
Boranil derivative 2 (Scheme 1) consists of electrondonating dieth-
lyamino group and hydroxyl group, which introduces two intermolec-
ular charge transfer (ICT) processes from diethlyamino group and
hydroxyl group to the Boranil core. We reasoned that the ICT process
from hydroxyl group to the Boranil core may be inhibited. We expect to
see that 1 would exhibit relatively weaker fluorescence intensity and
shorter emission wavelength compared to 2 (Scheme 1). When 1 mixed
with Cu2+, the ICT process from hydroxyl group to the Boranil core
could be restored with an increase in fluorescence intensity and
bathochromic-shift of the maximum emission wavelength. Satisfyingly,
we see that first fluorescent probe based on Boranil derivatives 1 is a
ratiometric fluorescent probe for sensitive and selective detection of
It is well known that fluorescent probes generally contain two
components: the fluorophore and the specific recognition site. Although
different fluorophores, such as coumarin [19,28], fluorescein [22],
rhodamine [21,31,34], naphthalimide [24], quinoline [23,25] and
boron dipyrromethene (BODIPY) [20] have been successfully employed
for the preparation of Cu2+ fluorescent probes, fluorescent probes based
on other new fluorophores are rarely reported. Thus the design and
synthesis of novel fluorophores are attractive research topics in the
fields of fluorescent probes recently. Boranil derivatives possess rigidify
skeletons and chelate core of N∧O-boron moiety, which exhibit
outstanding optical properties [42,43] and can be facilely synthesized,
modified and purified [44,45]. To the best of our knowledge, only two
Boranil-based fluorescent probes were developed for cysteine [44] and
biothiols [45] by our group, and Cu2+-specific fluorescent probe based
on Boranil derivatives has not been reported. In addition, hydrolysis
reaction of the picolinate moiety has been considered as an efficient
strategy for Cu2+ fluorescent probes and receives considerable attention
[25–31]. The 2-picolinic acid can be directly modified to hydroxyl-
phenyl group of the fluorophore to yield the picolinate moiety, where
the picolinate moiety can be hydrolyzed in the presence of Cu2+ and
subsequently releases the fluorophore.
Cu2+
.
2. Experimental
2.1. Reagents and apparatus
All the chemicals and solvents were purchased from Energy Chemi-
cal Corporation, and used as received with the following exceptions.
Dichloromethane (DCM) was dried over calcium hydride. Pure water
(18.25 Ω) was used to prepare all aqueous solutions. Column chroma-
tography was conducted on silica gel (200–300 mesh). Electrospray
ionization mass spectra (ESI-MS) were performed on an Agilent LC-MS
6120 equipped with Single Quadrupole LC/MS system. 1H and 13C nu-
clear magnetic resonance (NMR) spectra were recorded on Bruker
Avance-400 (400 MHz) spectrometer and referenced to the residue
solvent peaks (ref). UV–visible spectra were recorded in the wavelength
range of 300–550 nm on a Thermo Fisher Evolution 300 UV–vis spec-
trometer. Fluorescence spectra were recorded in the emission wave-
length range of 430–700 nm with the excitation wavelength at 405 nm
using a HITACHI F-4600 spectrometer. The excitation and emission slits
were set at 5 nm and 10 nm, respectively. All pH measurements were
examined with a FE20 pH-Meter, and the pH values were adjusted with
With the aforementioned facts in mind, we designed and synthesized
2

D. Zhu et al.
Inorganica Chimica Acta 524 (2021) 120438
Fig. 1. (a) Absorption and (b) fluorescence spectra of 1 (10 µM) before (black line) and after (red line) reaction with Cu2+ (40 µM) in HEPES buffer solution (1 mM,
H2O/CH3CN, v/v = 3:2, pH 7.0, 25 ◦C). The fluorescence color changes of 1 before and after the reaction in HEPES buffer solution under a 365 nm UV lamp are
shown in the inset.
1 M HCl and 1 N NaOH aqueous solution. The stock solution of 1 and 2
were prepared in DMSO (2 mM). The solutions of metal ions (10 mM)
were prepared from commercial CuSO4⋅5H2O, Al(NO3)3⋅9H2O,
BaCl2⋅2H2O, CaCl2, CdCl2⋅2.5H2O, CoCl2⋅6H2O, FeCl3⋅6H2O, HgCl2,
KCl, MgCl2⋅6H2O, MnSO4⋅H2O, NaCl and ZnCl2. The 4-(2-hydrox-
yethyl)-1-piperazineethanesulfonic acid (HEPES) buffer solutions were
prepared using deionized water. Fluorescence quantum yield was esti-
mated using quinine sulfate (Φf = 0.54 in 0.1 N H2SO4) as the reference
[46].
2.2. Synthesis of 1
3 and 2 were synthesized according to our previously reported
method [44,45]. 2 (332.2 mg, 1.0 mmol), 2-picolinic acid (183.2 mg,
1.5 mmol), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydro-
chloride (EDCI) (287.6 mg, 1.5 mmol), and 4-dimethylaminopyridine
(DMAP) (12.2 mg, 0.1 mmol) were dissolved in anhydrous DCM (30
mL) under argon atmosphere. The resulted solution was stirred over-
night at room temperature. Upon completion, 0.1 M HCl aqueous so-
lution (40 mL) was added into the reaction mixture. The mixed solution
was extracted with dichloromethane (3 × 30 mL). The organic layer was
combined and washed with brine, then dried over sodium sulfate. The
organic solvent was evaporated to generate crude solid, which was
further purified by flash chromatography (on silica gel) using DCM/
methanol (100:0–100:2, v/v) as the eluent to give the desired products,
153.1 mg (35%).1H NMR (400 MHz, d6-DMSO, ppm) δ = 8.84–8.82 (m,
1H), 8.70 (s, 1H), 8.27 (d, J = 8.0 Hz, 1H), 8.11–8.07 (m, 1H), 7.76–7.73
(m, 1H), 7.66 (d, J = 8.8 Hz, 1H), 7.51 (d, J = 9.2 Hz, 1H), 7.46 (d, J =
9.2 Hz, 2H), 6.57–6.54 (m, 1H), 6.18 (d, J = 2.0 Hz, 1H), 3.52 (q, J = 7.2
Hz, 4H), 1.18 (t, J = 6.8 Hz, 6H). 13C NMR (100 MHz, d6-DMSO, ppm) δ
= 163.4, 160.93, 159.92, 156.0, 145.0, 149.5, 146.6, 140.6, 137.7,
134.9, 127.9, 125.7, 124.1, 122.6, 106.8, 96.7, 44.4, 12.4. MS(ESI) for
Fig. 2. Effect of pH on fluorescence intensity ratio of F474 nm/F461 nm for 1 (10
μ
M) in the absence (black square) and presence (red cycle) of Cu2+ (40
μM) in
HEPES buffer solution (1 mM, H2O/CH3CN, v/v = 3:2, 25 ◦C, λex = 405 nm).
25 ◦C) were firstly evaluated. As illustrated in Fig. 1, the solution of 1
exhibited a maximum absorption peak at 402 nm with a molar extinc-
tion coefficient of 6.53 × 104 L molꢀ 1 cmꢀ 1. Upon adding Cu2+, the
maximum absorption peak was found to slightly bule-shift to 400 nm
with a molar extinction coefficient of 5.15 × 104 L molꢀ 1 cmꢀ 1. When
excited at 405 nm, fluorescence spectra of 1 before and after reaction
with Cu2+ displayed different fluorescence intensities and showed
maximum emission peaks at 461 nm (Φf = 0.006) and 474 nm (Φf =
0.085), respectively. This result is consistent with our hypothesis that
ratiometric fluorescence change for the ratio of the two emission peaks
at 474 nm and 461 nm (F474 nm/F461 nm) is observed. Simultaneously, an
obvious color change from dark blue to blue was observed by naked-eyes
under a 365 nm UV lamp (Fig. 1b inset). Interestingly, the absorption
spectra, fluorescence spectra and fluorescence color of the reaction
system are similar to those of 2 in HEPES buffer solution (Fig. S1†),
indicating that the Cu2+-promoted hydrolysis of the picolinate moiety
causes the release of 2. To further verify the proposed sensing mecha-
nism, the mixed solution of 1 with Cu2+ was analyzed by the ESI-MS
spectrum. A major peak at m/z = 333.1 [M + H]+ was detected
(Fig. S2†), which was consistent with the molecular weight of 2. All
these results clearly suggested that 1 underwent Cu2+-mediated hy-
drolysis and released the precursor 2 (Scheme 1).
C
23H23BF2N3O+3 ([M + H]+): calcd: 438.2, found: 438.2.
3. Results and discussions
The synthetic route for 1 was illustrated in Scheme 1, in where 1 was
made from 2 and 2-picolinic acid in the presence of EDCI and DMAP.
The chemical structure of 1 was fully characterized by nuclear magnetic
resonance (1H NMR and 13C NMR) spectrometry and electrospray
ionization (ESI-MS) mass spectrometry, which were explained in the
supporting information.
The UV–vis absorption and fluorescence spectra of 1 with/without
Cu2+ in HEPES buffer solution (1 mM, H2O/CH3CN, v/v = 3:2, pH 7.0,
3

D. Zhu et al.
Inorganica Chimica Acta 524 (2021) 120438
Fig. 3. (a) Fluorescence spectra of 1 (10
μ
M) recorded for 15 min in 1 min intervals after the addition of Cu2+ (40
μ
M) in HEPES buffer solution (1 mM, H2O/CH3CN,
v/v = 3:2, pH 7.0, 25 ◦C, λex = 405 nm). The fluorescence color changes of 1 without and with Cu2+ in HEPES buffer solution under a 365 nm UV lamp are shown in
the inset. (b) The fluorescence intensity ratio (F474 nm/F461 nm) changes as a function of time.
Next, we observed pH-dependent and time dependent fluorescence
response upon interacting with Cu2+. The ratios of fluorescence in-
tensities at 474 nm and 461 nm (F474 nm/F461 nm) of 1 without or with
Cu2+ were explored in HEPES buffer solution (1 mM, H2O/CH3CN, v/v
= 3:2, 25 ◦C, λex = 405 nm) by adjusting pH from 4.0 to 10.0 using HCl
or NaOH (Fig. 2). The fluorescence intensity ratio (F474 nm/F461 nm) of 1
without Cu2+ remained almost unchanged when pH changes from 4.0 to
10.0. On contrast, the fluorescence intensity ratio (F474 nm/F461 nm) of 1
with Cu2+ rapidly increased in the pH range from 5.0 to 7.0 and slightly
decreased in the pH range from 7.0 to 8.0. Very little change was
observed in the pH range from 8.0 to 10.0. Therefore, pH 7.0 was chosen
as the optimal pH in the following investigation.
Subsequently, the response time of 1 with Cu2+ was measured by
fluorescence spectroscopy in HEPES buffer solution (1 mM, H2O/
CH3CN, v/v = 3:2, 25 ◦C, λex = 405 nm). As depicted in Fig. 3, the so-
lution of 1 displayed a maximum emission peak at 461 nm (Fig. 3a).
Upon addition of Cu2+, the fluorescence intensity at 461 nm slightly
decreased, and a bathochromic-shift emission peak emerged at 474 nm
(Fig. 3a). Interestingly, we observed a significant color change for the
Fig. 4. Kinetic plot of the fluorescence intensity ratio (F474 nm/F461 nm) of the
solution from dark blue to blue under a 365 nm UV lamp (Fig. 3a inset),
indicating that 1 can be effectively employed as an efficient ratiometric
and colorimetric fluorescent probe for the detection of Cu2+. The fluo-
rescence intensity ratio (F474 nm/F461 nm) of 1 changed from 0.85 in the
pseudo-first order reaction of 1 (10
μ
M) to Cu2+ (40
μM), using excitation
wavelength at 405 nm. The slope of the plot corresponds to the observed re-
action rate of 5.76 £ 10¡3 s¡1
.
Fig. 5. Plot of the fluorescence intensity ratio (F474 nm/F461 nm) versus the response time in the presence of various concentrations of Cu2+ (from bottom to top):
0 (control), 1 µM, 2 µM, 3 µM, 4 µM, 5 µM, 10 µM, 20 µM, 30 µM, 40 µM and 50 µM. (b) The fluorescence intensity ratio (F474 nm/F461 nm) as a function of Cu2+
concentration in the range of 1–5
μ
M. Data were acquired in HEPES buffer solution (1 mM, H2O/CH3CN, v/v = 3:2, pH 7.0, 25 ◦C, λex = 405 nm).
4

D. Zhu et al.
Inorganica Chimica Acta 524 (2021) 120438
to Cu2+ was calculated to be 0.52
μM based on 3δ/k, where δ is the
standard deviation of blank measurement (number of measurements =
30) and k is the slope the fluorescence intensity ratio (F474 nm/F461 nm
)
versus Cu2+ concentration. The detection limit is much lower than the
MAL of Cu2+ in drinking water set by the WHO, U.S. EPA and Admin-
istration of the People’s Republic of China. These results indicate that 1
shows high sensitivity of detecting Cu2+ and allows for quantitative
detection based on ratiometric fluorescence changes.
Besides high sensitivity, selectivity is another criteria to evaluate a
fluorescent probe. The fluorescence responses of 1 toward various metal
ions, including Cu2+, Ag+, Al3+, Ba2+, Ca2+, Cd2+, Co2+, Fe3+, Hg2+, K+,
Mg2+, Mn2+, Na+ and Zn2+, were studied in HEPES buffer solution (1
mM, H2O/CH3CN, v/v = 3:2, pH 7.0, 25 ◦C, λex = 405 nm). As presented
in Fig. 6 and Fig. S3†, the fluorescence intensity ratio (F474 nm/F461 nm) as
well as fluorescence spectra of 1 induced significant changes with the
addition of Cu2+, while Ag+, Al3+, Ba2+, Ca2+, Cd2+, Co2+, Fe3+, Hg2+
,
K+, Mg2+, Mn2+, Na+ and Zn2+ exhibited negligible changes in the
fluorescence intensity ratio (F474 nm/F461 nm) and fluorescence spectra of
1. Furthermore, the competition experiments were further explored in
the presence of other metal ions mixed with Cu2+. It can be seen that the
coexistence of potentially competing other metal ions had no evident
effect on the fluorescence intensity ratio (F474 nm/F461 nm) and fluores-
cence spectra of 1 to Cu2+. The above results suggested that 1 possessed
high selectivity and strong anti-interference ability for the detection of
Fig. 6. Fluorescence responses of 1 (10 μM) to various metal ions (40 μM): 1,
Cu2+; 2, none (1); 3, Ag+; 4, Al3+; 5, Ba2+; 6, Ca2+; 7, Cd2+; 8, Co2+; 9, Fe3+; 10,
Hg2+; 11, K+; 12, Mg2+; 13, Mn2+; 14, Na+; 15, Zn2+. Gray bars represent the
fluorescence intensity ratio (F474 nm/F461 nm) of 1 and 1 treated with the marked
metal ions. Black bars represent the fluorescence intensity ratio (F474 nm/F461
nm) of 1 treated with the marked metal ions followed by Cu2+ (40
μM). Data
were acquired in HEPES buffer solution (1 mM, H2O/CH3CN, v/v = 3:2, pH 7.0,
25 ◦C, λex = 405 nm).
Cu2+
.
To our satisfaction, 1 can detect Cu2+ by monitoring fluorescence
color change under a 365 nm UV lamp. As demonstrated in Fig. 7, the
solution of 1 mixed with Cu2+ in the absence and presence of other metal
absence of Cu2+ to 1.22 in the presence of Cu2+ (Fig. 3b). In addition, the
ratio of F474 nm/F461 nm immediately increased in the first 5 min and
reached fatigue within 10 min (Fig. 3b), suggested that the reaction of 1
and Cu2+ can complete within 10 min. Hence the optimal response time
was determined as 10 min. Moreover, kinetic measurement of the re-
ions (Ag+, Al3+, Ba2+, Ca2+, Cd2+, Co2+, Fe3+, Hg2+, K+, Mg2+, Mn2+
,
Na+ and Zn2+), exhibited blue fluorescence, but the other aforemen-
tioned metal ions displayed dark blue fluorescence, indicating that 1
showed excellent selectivity to Cu2+ over other metal ions.
action between 1 (10
μ
M) and Cu2+ (40
μM) under the pseudo-first-
order condition gave an observed rate constant of kobs = 5.76 £ 10¡3
s¡1 (Fig. 4), indicating that 1 can be used for the real-time detection of
Cu2+ in high sensitivity.
By comparing to other fluorescent probes with picolinate as the
recognition unit (Table S1), we see similar results in terms of detection
limit and response time for the detection of Cu2+. Specifically, the
To test sensitivity of 1 for Cu2+, we titrated 1 with different con-
centrations of Cu2+ by monitoring the fluorescence intensity ratio (F474
nm/F461 nm). It can be seen in Fig. 5, the fluorescence intensity ratio (F474
nm/F461 nm) was continuously increased while the concentration of Cu2+
detection limit (0.52 μM) is similar to these of the probes based on
dicyanoisophorone [29], quinolone [25], and fluorescein [47]. For the
response time (10 min), it is consistent with these of fluorescent probes
for Cu2+ sensing based on BODIPY [48] and tricyanofuran [49].
changes from 0 μM to 40 μM, and a linear relationship between the
fluorescence intensity ratio (F474 nm/F461 nm) and Cu2+ concentration
4. Conclusion
was observed in the low concentration range of 0–5 μM (Fig. 5 inset). A
linear regression curve was y = 0.83641 + 0.02617 x, with a correlation
In summary, we have developed a novel ratiometric fluorescent
coefficient (R2) of 0.995 (Fig. 5b inset). The limit of detection (LOD) of 1
Fig. 7. The fluorescence color changes observed before (a) and after (b) the addition of Cu2+ (40
μM) to the solution of 1 (10 μM) in HEPES buffer solution (1 mM,
H2O/CH3CN, v/v = 3:2, pH 7.0, 25 ◦C) under a 365 nm UV lamp in the presence of different metal ions (40
μ
M): Cu2+, none (1), Ag+, Al3+, Ba2+, Ca2+, Cd2+, Co2+
,
Fe3+, Hg2+, K+, Mg2+, Mn2+, Na+, Zn2+
.
5

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Inorganica Chimica Acta 524 (2021) 120438
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2018GXNSFAA281166,
2020GXNSFBA159050), Students’ Platform for Innovation and Entre-
preneurship Training Program (201811838035), High Level Innovation
Teams of Guangxi Colleges & Universities and Outstanding Scholars
Program (Guijiaoren[2018]35) and Special Project on Innovation-
driven Development of Hezhou (HKCPT1907006), W.Z. acknowledge-
ments the support of the Beijing Institute of Technology Research Fund
Program for Young Scholars.
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