A highly selective fluorescent chemosensor for Hg2+ based on rhodamine B and its application as a molecular logic gate

Article abstract of DOI:10.1016/j.dyepig.2013.01.002

A novel and simple fluorescent chemosensor based on rhodamine (R-2) is designed and synthesized to detect Hg²⁺. Probe R-2 exhibits high selectivity and sensitivity for sensing Hg²⁺ with a detection limit at 10^-8 M level, and displays a significant color change from colorless to pink color in the presence of Hg²⁺. About a 400-fold increase in fluorescence emission intensity is observed upon binding excess Hg²⁺ in 50% H₂O/CH₃CN HEPES buffer at pH 7.00. The titration results show a 1:1 complex formation between R-2 and Hg ²⁺. The reversibility of chemosensor R-2 is verified through its spectral response toward Hg²⁺ and I^- titration experiments. Using Hg²⁺ and I^- as chemical inputs and the fluorescence intensity signal as outputs, R-2 can be utilized as an INHIBIT logic gate at molecular level.

Full text of DOI:10.1016/j.dyepig.2013.01.002

Dyes and Pigments 97 (2013) 324e329
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Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
A highly selective fluorescent chemosensor for Hg2þ based on
rhodamine B and its application as a molecular logic gate
*
*
Zhengping Dong , Xin Tian, Yuanzhe Chen, Jingran Hou, Yueping Guo, Jian Sun, Jiantai Ma
State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, South Tianshui Road, Lanzhou 730000, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel and simple fluorescent chemosensor based on rhodamine (R-2) is designed and synthesized to
detect Hg2þ. Probe R-2 exhibits high selectivity and sensitivity for sensing Hg2þ with a detection limit at
Received 14 September 2012
Received in revised form
27 November 2012
Accepted 2 January 2013
Available online 16 January 2013
10ꢀ8 M level, and displays a significant color change from colorless to pink color in the presence of Hg2þ
.
About a 400-fold increase in fluorescence emission intensity is observed upon binding excess Hg2þ in
50% H2O/CH3CN HEPES buffer at pH 7.00. The titration results show a 1:1 complex formation between R-
2 and Hg2þ. The reversibility of chemosensor R-2 is verified through its spectral response toward Hg2þ
and Iꢀ titration experiments. Using Hg2þ and Iꢀ as chemical inputs and the fluorescence intensity signal
as outputs, R-2 can be utilized as an INHIBIT logic gate at molecular level.
Keywords:
Chemosensor
Mercury
Ó 2013 Elsevier Ltd. All rights reserved.
Rhodamine B
Logic gate
Selective detection
Reversibility
1. Introduction
recent years, many Hg2þ sensors based on rhodamine derivatives
have been developed [14,19,26e30]. Most of the developments
Mercury, one of the most prevalent toxic heavy metals in the
environment, can easily pass through biological membranes and
through respiratory and gastrointestinal tissues [1e3]. When
absorbed in the human body, it will produce damage to the brain,
kidneys and endocrine system [4]. As a result, there has been
considerable interest in the development of effective tools for
detecting Hg2þ ions in the environment. As fluorescence meas-
urement provides a powerful way for detecting metal ions because
of its low detection limit and simple instrumentation, considerable
efforts have been devoted to design fluorescent chemical sensors
for detecting Hg2þ [5e10]. Many Hg2þ sensors based on pyrene
[11e13], naphthalimide [14e16], bispyrenyl [17], terphenyl [18,19],
naphthylthiourea [20], dansyl [21e23] have been reported. How-
ever, most of these sensors are irreversible, and cannot be used to
monitor both the increase and the decrease of Hg2þ concentration
in the environment or some biological metabolite. Therefore, the
development of reversibly fluorescent chemosensors for Hg2þ
determination with light “off-on” and high selectivity is still highly
desirable [24].
have shown that rhodamine derivatives are promising structural
scaffold for the design of reversible and selective chemosensors.
The cation-sensing mechanism of most of the rhodamine probes is
based on a change from the spirolactam to an open-ring amide,
resulting in a color change, highly fluorescent compound. When
some ligands which exhibit stronger coordination ability with Hg2þ
are added to the Hg2þ-rhodamine sensing system, the open-ring
amide will change to spirolactam, and the reversibility is realizable.
On the other hand, since the pioneering work by de Silva [31],
using fluorescent signal as outputs and chemically encoded infor-
mation (such as pH, temperature, light, anions and metal ions) as
inputs to design molecular logic gates is an area of intense research
activity [32e37]. And molecular systems showing functions such as
AND, NAND, OR, XOR, and INHIBIT have been widely explored [37e
40]. In all the molecular logic gates systems, the molecule dem-
onstrates “on” or “off” switching of the fluorescence signal meaning
“1” or “0” output, in response to the addition “1” or no addition “0”
of the input chemicals. Thus, they have the potential for compu-
tation on a molecular level that silicon based devices cannot
address.
Rhodamine is a dye used extensively as a fluorescent signal
transducer due to its excellent photophysical properties [25]. In
Bearing the above statement in mind, we herein report the
design, synthesis and spectral characteristics of a mercuric probe
R-2 based on rhodamine B. It shows highly fluorescent selective for
Hg2þ over other metal ions. Adding Iꢀ to the mixture of Hg2þ and
* Corresponding authors. Tel.: þ86 0931 8912577; fax: þ86 0931 8912582.
E-mail addresses: dongzhp@lzu.edu.cn (Z. Dong), majiantai@lzu.edu.cn (J. Ma).
0143-7208/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.dyepig.2013.01.002

Z. Dong et al. / Dyes and Pigments 97 (2013) 324e329
325
R-2 solution, the fluorescence is turned off and the pink color of the
Hg2þ/R-2 system also turned colorless, indicating that Iꢀ sequesters
Hg2þ of the mixture, liberates the free R-2 [19,24,41]. And the
reversibility of R-2 is realizable. Using Hg2þ and Iꢀ as chemical
inputs and the fluorescence intensity signal as outputs, R-2 can be
utilized as an INHIBIT logic gate at molecular level. We hope such
rhodamine-based fluorescent sensors and molecular logic devices
will find application in the development of cations sensing probes
and digital devices.
give R-2 (0.77 g, yield: 74%).1H NMR (d6-DMSO, 400 MHz):
d
0.97 (m,
24H), 1.93 (s, 3H), 3.19 (m, 16H), 6.25 (m, 4H), 6.40 (m, 8H), 7.02 (m,
4H), 7.53 (s, 4H), 7.90 (s, 2H), 8.88 (s, 2H), 11.14 (s, 1H) ppm; 13C NMR
(d6-DMSO, 100 MHz):
d 12.20, 18.46, 19.53, 43.55, 55.98, 65.31, 97.38,
104.83, 108.02, 119.93, 122.94, 123.60, 127.40, 127. 87, 128.31, 128.66,
130.18, 133.8, 146.78, 148.42, 151.15, 152.58, 154.18, 163.45 ppm; ESI:
(m/z) 1041.9 [M þ H]þ.
2.4. General methodology adopted for spectroscopic studies
2. Experimental
1H NMR and 13C NMR spectra were recorded using 400 MHz and
100 MHz. Chemical shifts were expressed in ppm and coupling
constants (J) in Hz. Absorption spectra were determined on a Varian
UV-Cary100 spectrophotometer. Fluorescence spectra measure-
ments were performed on a Hitachi F-4500 spectrofluorimeter.
HEPES buffer solutions (20 mM, pH ¼ 7.0) were prepared in
deionized water.
2.1. Regents
Rhodamine B and hydrazine hydrate were purchased from
Aladdin Chemistry Co. Ltd. Cationic compounds such as NaClO4,
KClO4, Mg(ClO4)2, Ca(ClO4)2, Fe(ClO4)3, Co(ClO4)2, Ni(ClO4)2,
Cu(ClO4)2, Zn(ClO4)2, Cd(ClO4)2, Al(ClO4)3, Pb(ClO4)2, AgClO4 and
Hg(ClO4)2 were purchased from Aldrich and used as received. All
other chemicals were of the reagent-grade purchased from Tianjing
Guangfu Chemical Companies and used as supplied. All solvents
used for synthesis and measurements were redistilled before use.
UVevis titrations were performed on 1 ꢁ 10ꢀ5 M solution of
ligand R-2 in HEPES buffer (20 mM, pH ¼ 7.0) containing 50% (v/v)
H2O/CH3CN. Typical aliquots of freshly prepared Hg(ClO4)2 solu-
tions (1 ꢁ 10ꢀ2 M to 1 ꢁ 10ꢀ5 M solutions in CH3CN) were added
and the UVevis spectra of samples were recorded.
Fluorescence titrations were performed on 1 ꢁ 10ꢀ5 M solution
of ligand R-2 in HEPES buffer (20 mM, pH ¼ 7.0) containing 50% (v/
v) H2O/CH3CN. Typical aliquots of freshly prepared metal perchlo-
2.2. Synthesis of compound R-1
rates (Hg2þ, Naþ, Kþ, Mg2þ, Ca2þ, Al3þ, Cd2þ, Zn2þ, Ni2þ, Co2þ, Pb2þ
,
Rrhodamine hydrazide was synthesized following the reported
procedure [42]. To rhodamine B hydrochloride (0.96 g, 2 mmol)
dissolved in 30 mL methanol, excess amount of hydrazine hydrate
(1 mL, 6.98 mmol) was added and the reaction mixture was
refluxed till the pink color disappeared. After that, the reaction
mixture was cooled to room temperature, poured into distilled
water and extracted with ethyl acetate (6 ꢁ 25 mL). The combined
extract was washed with brine, dried with anhydrous sodium
sulfate, filtered, and then concentrated under reduced pressure to
yield 0.64 g (70%) of compound R-1. 1H NMR (CDCl3, 400 MHz):
Fe3þ and Agþ) standard solutions (1 ꢁ 10ꢀ2 M to 1 ꢁ 10ꢀ5 M solu-
tions in CH3CN) were added and the fluorescence spectra of sam-
ples were recorded.
3. Results and discussion
In this paper, compound R-1 was synthesized by the reaction of
rhodamine B and hydrazine hydrate, the new probe R-2 was syn-
thesized by the condensation reaction between R-1 and 4-Methyl-
2, 6-Diformyl Phenol (Scheme 1). Its structure was confirmed by ESI
data, 1H NMR and 13C NMR spectrum, and it was designed to che-
late with metal ions via its carbonyl O and amine N atoms. Similar
to other rhodamine spirolactam derivatives [25,44], compound R-2
forms a fluorescence inactive solution in either aqueous buffer
solution or pure organic solvent, indicating that the spirolactam
form exists predominantly.
d
1.168 (t, J ¼ 7.2 Hz, 12H), 3.36 (q, J ¼ 7.0 Hz, 8H), 3.63 (s, 2H), 6.30
(d, J ¼ 2.4 Hz, 2H), 6.42 (d, J ¼ 2.4 Hz, 2H), 6.48 (s, 1H), 6.52 (s, 1H),
7.11 (m, 1H), 7.46 (m, 2H), 7.94 (m, 1H) ppm; 13C NMR (CDCl3,
100 MHz):
d 11.9, 43.7, 65.3, 96.4, 103.6, 107.5, 122.7, 123.2, 127.6,
128.4, 131.8, 147.4, 150.9, 153.6, 165.3 ppm; ESI: (m/z) 457.4
[M þ H]þ.
2.3. Synthesis of compound R-2
3.1. Fluorescence and UVevis spectral responses of R-2
4-Methyl-2, 6-Diformyl Phenol was synthesized as reported
[43]. 1H NMR (CDCl3, 400 MHz):
d
2.39 (s, 3H), 7.77 (s, 2H), 10.22 (s,
The fluorescence intensity changes of R-2 were monitored upon
adding metal ions to determine the cations binding abilities. Fig. 1a
showed fluorescence spectra of R-2 in the presence and absence of
2H), 11.46 (s, 1H) ppm; 13C NMR (CDCl3, 100 MHz):
d 20.06, 120.1,
129.1, 132.6, 136.9, 196.7 ppm; EI: (m/z) 164.
A stirred solution of R-1 (1.0 g, 2.2 mmol), 4-Methyl-2, 6-Diformyl
Phenol (0.164 g, 1.0 mmol) in ethanol (50 mL) was heated under
reflux for 5 h under N2 in the dark. After the ethanol had been
evaporated under reduced pressure, the residue was purified by
silica gel column chromatography (CH2Cl2/MeOH/Et3N ¼ 200:1:1) to
500 mM of cations. R-2 showed only a very weak fluorescence in the
absence of metal ions. A high-intensity fluorescence band at
595 nm was observed upon addition of Hg2þ into the solution of R-
2. Fluorescence almost did not change in Naþ, Kþ, Mg2þ, Ca2þ, Al3þ
,
Cd2þ, Zn2þ, Ni2þ, Co2þ, Pb2þ, Fe3þ and Agþ solutions. Like some
Scheme 1. Synthetic procedure of chemosensor R-2.

326
Z. Dong et al. / Dyes and Pigments 97 (2013) 324e329
Fig. 2. Fluorescence spectra of R-2 (10
HEPES, 50:50, v/v, pH 7.0) upon addition of different amounts of Hg2þ ion. Inset: flu-
orescence intensity at 595 nm of R-2 (10
M) as a function of Hg2þ concentration (0e
500
M). lex ¼ 500 nm.
mM) in CH3CN-HEPES buffer solution (20 mM
m
m
Fig. 1. (a) Fluorescence spectra of R-2 (10 m
M) upon addition of 50 eq. of Hg2þ and 50
eq. other metal ions in CH3CN-HEPES buffer solution (20 mM HEPES, 50:50, v/v, pH
7.0). (b) Fluorescence response of R-2 (10
M) to 50 eq. Hg2þ in CH3CN-HEPES buffer
solution (20 mM HEPES, 50:50, v/v, pH 7.0) containing 50 eq. various metal ions. The
black bars represent the addition 50 eq. of the competing metal ion to a 10 M solution
m
m
of R-2. The gray bars represent the change of the emission that occurs upon the
subsequent addition of 50 eq. Hg2þ to the above solution. lex ¼ 500 nm, lem ¼ 595 nm.
other reported rhodamine-based mercury sensors [25,27,45], the
fluorescence intensity of R-2 was affected to some extent in Cu2þ
solutions. High concentration of Cu2þ contamination is likely to
mislead the fluorescent selectivity of Hg2þ. So, when R-2 is used as
the probe for Hg2þ, high concentration of Cu2þ interference must
be eliminated by using quinoline derivative based adsorbent [46].
On the other hand, an important feature of the chemosensor is its
high selectivity toward the analyte over the other competitive
species. Herein, a competition experiment was also carried out by
adding Hg2þ to the solution of R-2 in the presence of other metal
ions. Fig. 1b showed the comparison between the fluorescence
response of R-2 with each metal ion and the emission that occurred
after the addition of Hg2þ. The results indicated that the sensing of
Hg2þ by R-2 was hardly affected by the commonly co-existent ions.
In other words, the selectivity of R-2 for the Hg2þ over other
competitive cations was remarkably high.
Fig. 3. (a) Absorption spectra of R-2 (10
2 eq.) of Hg2þ in CH3CN-HEPES buffer solution (20 mM HEPES, 50:50, v/v, pH 7.0). Inset:
The color changes of R-2 (10
M) to Hg2þ in CH3CN-HEPES buffer solution (20 mM HEPES,
50:50, v/v, pH 7.0). (b) Absorbance at 600 nm of R-2 (10
M) as a function of Hg2þ
concentration (0e20 M). Inset: The nonlinear fitting (absorbance at 600 nm) of R-2.
mM) with addition increasing concentration (0e
In order to gain an insight into the signaling properties of R-2
toward Hg2þ, fluorescence titration experiments were carried out
in CH3CN-HEPES buffer solution (20 mM, pH ¼ 7.0 50% (v/v) H2O/
CH3CN). A new emission band at 595 nm gradually appeared
m
m
m

Z. Dong et al. / Dyes and Pigments 97 (2013) 324e329
327
upon the addition of Hg2þ (Fig. 2). In the presence of 50 eq. of
Hg2þ, the mixture showed an intense orange fluorescence and
>400-fold enhancement in the fluorescence intensity at
a
595 nm. Furthermore, for the UVevis titration spectra of R-2, in
the addition of Hg2þ (0e2 eq.), there was also a new absorption
peak at 600 nm, which was consistent with the result of fluo-
rescence spectra (Fig. 3a). After the addition of various concen-
tration of Hg2þ (from 0 to 2 eq.) to R-2 solution (1*10ꢀ5 M), it was
found that, when the concentration of Hg2þ reached 10ꢀ8 M, the
absorption intensity at 600 nm of R-2 enhanced in the visible
range at room temperature. And the absorption intensity grad-
ually enhanced when increasing Hg2þ. For practical application,
the detection limit of this new chemosensor was also evaluated
by fluorescence and UVevis titration, and the titration results
demonstrated that the detection limit of Hg2þ was at 10ꢀ8
level.
M
The unique and highly selective of rhodamine based fluorescent
sensors for Hg2þ can also be easily observed by even naked eye
detection [4,47,48]. The color change of R-2 in CH3CN-HEPES buffer
solution with Hg2þ was shown in Fig. 3a inset. From Fig. 3a inset, it
can be seen that, Hg2þ caused visible detectable color change of R-2
solution, from colorless to pink.
Fig. 4. Job’s plot of Hg2þ versus R-2 ([Hg2þ] þ [R-2] ¼ 20
mM) at 600 nm.
h
i
A ꢀ Amin
Amax ꢀ A
lg
¼ lgK þ nlg Mnþ
In the equation, K is the association constant, Amax is the
absorbance of R-2 in the presence of excess amount of Hg2þ, A is the
absorbance of R-2 obtained with various concentration of Hg2þ
3.2. Determination of binding constant
,
In this work, the spirolactam moiety of the rhodamine
group acts as a signal switcher, which is envisioned to turn on
when the cation is binded (Scheme 2). When sensor R-2 meets
Hg2þ, the spirolactam form (fluorescence-off) of R-2 converts to
the Hg2þ-promoted ring-opened amide form (fluorescence-on),
the R-2 þ Hg2þ system forms a large conjugated system, which
serves as the foundation for a novel chemosensor for Hg2þ [49].
Moreover, the sensor is most likely to chelate metal ions via
the imide N and phenol O atoms like other reported sensors
[7,30,50e52].
Amin is the absorbance of R-2 without any cation. The nonlinear
fitting of the titration curve showed a 1:1 stoichiometry between R-
2 and Hg2þ (Fig. 3b). This result was further confirmed by the Job’s
plot (Fig. 4). From Fig. 4, it can be observed that the absorbance
went through a maximum at a molar fraction of about 1/2, indi-
cating that a 1:1 stoichiometry was most possible for the binding
mode of Hg2þ and R-2. Thus, in accordance with the 1:1 stoichi-
ometry, the possible binding mode between R-2 toward Hg2þ was
proposed in Scheme 2.
As a highly selective fluorescent chemosensor, the binding
constant of R-2 for Hg2þ was also investigated. By assuming a 1:n
stoichiometry for interaction between R-2 and metal ions, the as-
3.3. Logic gate
sociation constant of R-2 for Hg2þ determined from the following
Due to the reversibility is an important aspect for a chemical
sensor to be widely employed in the detection of specific analyses,
2D
equation [53,54] to be K ¼ 9.21 ꢁ 105 Mꢀ1
.
Hg
Scheme 2. Proposed binding mode of R-2 with Hg2þ
.

328
Z. Dong et al. / Dyes and Pigments 97 (2013) 324e329
Fig. 5. Fluorescence spectrum (lex ¼ 500 nm) of R-2 (10
m
M) in the presence of Hg2þ (500
m
M) and Iꢀ (1 mM) in CH3CN-HEPES buffer solution (20 mM HEPES, 50:50, v/v, pH 7.0),
truth table, and logic scheme (Inset, A: R-2þ Hg2þ. B: R-2þ Hg2þþIꢀ).
[2] Chen C, Wang R, Guo L, Fu N, Dong H, Yuan Y. A squaraine-based colorimetric
and “turn on” fluorescent sensor for selective detection of Hg2þ in an aqueous
medium. Org Lett 2011;13:1162e5.
[3] Liu W, Chen J, Xu L, Wu J, Xu H, Zhang H, et al. Reversible "off-on" fluorescent
chemosensor for Hg2þ based on rhodamine derivative. Spectrochim Acta A
2012;85:38e42.
[4] Wang F, Nam SW, Guo Z, Park S, Yoon J. A new rhodamine derivative bearing
benzothiazole and thiocarbonyl moieties as a highly selective fluorescent and
colorimetric chemodosimeter for Hg2þ. Sens Actuators B 2012;161:948e53.
[5] Cheng X, Li Q, Qin J, Li Z. A new approach to design ratiometric fluorescent
probe for mercury(II) based on the Hg2þ-promoted deprotection of thio-
acetals. ACS Appl Mater Interf 2010;2:1066e72.
[6] Yoon S, Miller EW, He Q, Do PH, Chang CJ. A bright and specific fluorescent
sensor for mercury in water, cells, and tissue. Angew Chem Int Edit 2007;46:
6658e61.
[7] Zhao Y, Zheng BZ, Du J, Xiao D, Yang L. A fluorescent "turn-on" probe for the
dual-channel detection of Hg(II) and Mg(II) and its application of imaging in
living cells. Talanta 2011;85:2194e201.
[8] Xie ZJ, Wang K, Zhang CL, Yang ZH, Chen YC, Guo ZJ, et al. A fluorometric/
colorimetric dual-channel Hg2þ sensor derived from a 4-amino-7-nitro-ben-
zoxadiazole (ANBD) fluorophore. New J Chem 2011;35:607e13.
[9] Wu YZ, Dong Y, Li JF, Huang XB, Cheng YX, Zhu CJ. A highly selective and
sensitive polymer-based fluorescence sensor for Hg2þ-ion detection via click
reaction. Chem Asian J 2011;6:2725e9.
the reversibility experiment has been carried out. In light of the
strong binding ability of the Iꢀ toward Hg2þ, the reversibility of the
system was investigated by introduction of iodide anion [26]
(Fig. 5). When Iꢀ was added to the system, the fluorescence emis-
sion did not change. The addition of Hg2þ to the solution of R-2
caused fluorescence enhancement. Upon addition of excess amount
of Iꢀ to the mixture of R-2 and Hg2þ, the color of the mixture
changed from pink to colorless (Fig. 5, inset), and fluorescent
emission intensity of the system was quenched, indicating that Iꢀ
replaced the receptor R-2 to coordinate Hg2þ
.
These behaviors can be analyzed with the combinational logic
circuit. The two input signals are Input 1 (Hg2þ) and input 2 (Iꢀ).
Input 1 leads to fluorescence enhancement in its occupied state,
equivalent to a YES operation. The interaction of input 2 with its
corresponding receptor leads to fluorescence quenching, thereby
implementing the necessary NOT gate. The receptor acts in parallel
on the fluorescence output signals, which implements the required
AND function. In the presence of both inputs, the quenching (by
input 2) overrides the fluorescence enhancement by input 1, in
accordance with the truth table shown in Fig. 5. Therefore, mon-
itoring the fluorescence at 595 nm, upon addition of Hg2þ, Iꢀ and
their reacting dose mixture lead to an INHIBIT logic gate.
[10] Jiang X-J, Wong C-L, Lo P-C, Ng DKP. A highly selective and sensitive BODIPY-
based colourimetric and turn-on fluorescent sensor for Hg2þ ions. Dalton
Trans 2012;41:1801e7.
[11] Weng JN, Mei QB, Ling QD, Fan QL, Huang W. A new colorimetric and fluo-
rescent ratiometric sensor for Hg2þ based on 4-pyren-1-yl-pyrimidine. Tet-
rahedron 2012;68:3129e34.
[12] Zhou Y, Zhu C-Y, Gao X-S, You X-Y, Yao C. Hg2þ-selective ratiometric and "off-
on" chemosensor based on the azadiene-pyrene derivative. Org Lett 2010;12:
2566e9.
4. Conclusion
[13] Lin W-C, Wu C-Y, Liu Z-H, Lin C-Y, Yen Y-P. A new selective colorimetric and
fluorescent sensor for Hg2þ and Cu2þ based on a thiourea featuring a pyrene
unit. Talanta 2010;81:1209e15.
[14] Liu YL, Lv X, Zhao Y, Chen ML, Liu J, Wang P, et al. A naphthalimide-rhodamine
ratiometric fluorescent probe for Hg2þ based on fluorescence resonance en-
ergy transfer. Dyes Pigm 2012;92:909e15.
[15] Chen T, Zhu W, Xu Y, Zhang S, Zhang X, Qian X. A thioether-rich crown-based
highly selective fluorescent sensor for Hg2þ and Agþ in aqueous solution.
Dalton Trans 2010;39:1316e20.
[16] He C, Zhu W, Xu Y, Chen T, Qian X. Trace mercury (II) detection and separation
in serum and water samples using a reusable bifunctional fluorescent sensor.
Anal Chim Acta 2009;651:227e33.
In summary, a simple and easy-to-prepare rhodamine-based
optical chemosensor R-2 for the detection of Hg2þ ions has been
synthesized. The sensor R-2 displayed highly selective and sensitive
fluorescent enhancement and colorimetric change upon the addi-
tion of Hg2þ. The fluorescent selectivity of R-2 for Hg2þ may be
slightly affected when coexisted with Cu2þ. The reversibility of the
sensor was realizable by introduction of iodide anion. Moreover,
the fluorescent changes of R-2 upon the addition of Hg2þ and Iꢀ can
be utilized as an INHIBIT logic gate. Therefore, this simple sensor
could be potential candidate for the development of a new gener-
ation of digital devices.
[17] Kumar M, Dhir A, Bhalla V, Sharma R, Puri RK, Mahajan RK. Highly effective
chemosensor for mercury ions based on bispyrenyl derivative. Analyst 2010;
135:1600e5.
[18] Bhalia V, Tejpal R, Kumar M, Sethi A. Terphenyl derivatives as "turn on" flu-
orescent sensors for mercury. Inorg Chem 2009;48:11677e84.
[19] Bhalla V, Tejpal R, Kumar M. Rhodamine appended terphenyl: a reversible
"off-on" fluorescent chemosensor for mercury ions. Sens Actuators B 2010;
151:180e5.
Acknowledgments
[20] Chen Y, Sun Z-H, Song B-E, Liu Y. Naphthylthiourea-modified per-
methylcyclodextrin as a highly sensitive and selective "turn-on" fluorescent
chemosensor for Hg2þ in water and living cells. Org Biomol Chem 2011;9:
5530e4.
This work was supported by the Fundamental Research Funds
for the Central Universities (lzujbky-2012-68).
[21] Li H-W, Wang B, Dang Y-Q, Li L, Wu Y. A highly selective fluorescent sensor for
mercury ions in aqueous solution: detection based on target-induced aggre-
gation. Sens Actuators B 2010;148:49e53.
References
[22] Wang X, Wang P, Dong Z, Dong Z, Ma Z, Jiang J, et al. Highly sensitive fluo-
[1] Lu H, Xiong L, Liu H, Yu M, Shen Z, Li F, et al. A highly selective and sensitive
fluorescent turn-on sensor for Hg2þ and its application in live cell imaging.
Org Biomol Chem 2009;7:2554e8.
rescence probe based on functional SBA-15 for selective detection of Hg2þ
.
Nanoscale Res Lett 2010;5:1468e73.

Z. Dong et al. / Dyes and Pigments 97 (2013) 324e329
329
[23] Dhir A, Bhalla V, Kumar M. Ratiometric sensing of Hg2þ based on the calix[4]
arene of partial cone conformation possessing a dansyl moiety. Org Lett 2008;
10:4891e4.
[39] Kluciar M, Ferreira R, de Castro B, Pischel U. Modular functional integration of
a two-input INH logic gate with a fluorophore-spacer-receptor1-spacer-re-
ceptor2 conjugate. J Org Chem 2008;73:6079e85.
[24] Lin W, Cao X, Ding Y, Yuan L, Yu Q. A reversible fluorescent Hg2þ chemosensor
based on a receptor composed of a thiol atom and an alkene moiety for living
cell fluorescence imaging. Org Biomol Chem 2010;8:3618e20.
[40] Zhou J, Arugula MA, Halamek J, Pita M, Katz E. Enzyme-based NAND and NOR
logic gates with modular design. J Phys Chem B 2009;113:16065e70.
[41] Wu D, Huang W, Lin Z, Duan C, He C, Wu S, et al. Highly sensitive multi-
responsive chemosensor for selective detection of Hg2þ in natural water and
different monitoring environments. Inorg Chem 2008;47:7190e201.
[42] Chereddy NR, Thennarasu S. Synthesis of a highly selective bis-rhodamine
chemosensor for naked-eye detection of Cu2þ ions and its application in
bio-imaging. Dyes Pigm 2011;91:378e82.
[43] Wu JC, Tang N, Liu WS, Tan MY, Chan ASC. Intramolecular hydrogen bond self-
template synthesis of some new Robson-type macrocyclic ligands. Chin Chem
Lett 2001;12:757e60.
[44] Ma Q-J, Zhang X-B, Zhao X-H, Jin Z, Mao G-J, Shen G-L, et al. A highly selective
fluorescent probe for Hg2þ based on a rhodamine-coumarin conjugate. Anal
Chim Acta 2010;663:85e90.
[25] Kaewtong C, Wanno B, Uppa Y, Morakot N, Pulpoka B, Tuntulani T. Facile
synthesis of rhodamine-based highly sensitive and fast responsive colori-
metric and off-on fluorescent reversible chemosensors for Hg2þ: preparation
of a fluorescent thin film sensor. Dalton Trans 2011;40:12578e83.
[26] Zhao Y, Sun Y, Lv X, Liu Y, Chen M, Guo W. Rhodamine-based chemosensor for
Hg2þ in aqueous solution with a broad pH range and its application in live cell
imaging. Org Biomol Chem 2010;8:4143e7.
[27] Wang Y, Huang Y, Li B, Zhang L, Song H, Jiang H, et al. A cell compatible
fluorescent chemosensor for Hg2þ based on a novel rhodamine derivative that
works as a molecular keypad lock. RSC Adv 2011;1:1294e300.
[28] Hu Z-Q, Lin C-S, Wang X-M, Ding L, Cui C-L, Liu S-F, et al. Highly sensitive and
selective turn-on fluorescent chemosensor for Pb2þ and Hg2þ based on
a rhodamine-phenylurea conjugate. Chem Commun 2010;46:3765e7.
[29] Saha S, Mahato P, Reddy UG, Suresh E, Chakrabarty A, Baidya M, et al. Recognition
of Hg2þ and Cr3þ in physiological conditions by a rhodamine derivative and its
application as a reagent for cell-imaging studies. Inorg Chem 2012;51:336e45.
[30] Jiang L, Wang L, Zhang B, Yin G, Wang R-Y. Cell compatible fluorescent che-
mosensor for Hg2þ with high sensitivity and selectivity based on the rhod-
amine fluorophore. Eur J Inorg Chem 2010:4438e43.
[45] Zeng X, Dong L, Wu C, Mu L, Xue S-F, Tao Z. Highly sensitive chemosensor for
Cu(II) and Hg(II) based on the tripodal rhodamine receptor. Sens Actuators B
2009;141:506e10.
[46] Mu Shi, Chang JC, Lee S-T. Silicon nanowires-based fluorescence sensor for
Cu(II). Nano Lett 2008;8:104e9.
[47] Wang H, Li Y, Xu S, Li Y, Zhou C, Fei X, et al. Rhodamine-based highly sensitive
colorimetric off-on fluorescent chemosensor for Hg2þ in aqueous solution and
for live cell imaging. Org Biomol Chem 2011;9:2850e5.
[31] de Silva AP, McClenaghan ND. Molecular-scale logic gates. Chem Eur J 2004;
10:574e86.
[32] Amir RJ, Popkov M, Lerner RA, Barbas CF, Shabat D. Prodrug activation gated
by a molecular “OR” logic trigger. Angew Chem Int Edit 2005;44:4378e81.
[33] Andréasson J, Terazono Y, Albinsson B, Moore TA, Moore AL, Gust D. Molecular
[48] Huang J, Xu Y, Qian X. A rhodamine-based Hg2þ sensor with high selectivity
and sensitivity in aqueous solution: a NS2-containing receptor. J Org Chem
2009;74:2167e70.
[49] Zhang XL, Xiao Y, Qian XH. A ratiometric fluorescent probe based on FRET for
imaging Hg2þ ions in living cells. Angew Chem Int Edit 2008;47:8025e9.
[50] Mahato P, Saha S, Suresh E, Di Liddo R, Parnigotto PP, Conconi MT, et al.
Ratiometric detection of Cr3þ and Hg2þ by a naphthalimide-rhodamine based
fluorescent probe. Inorg Chem 2012;51:1769e77.
[51] Lee PF, Yang C-T, Fan D, Vittal JJ, Ranford JD. Synthesis, characterization and
physicochemical properties of copper(II) complexes containing salicylalde-
hyde semicarbazone. Polyhedron 2003;22:2781e6.
[52] Wang LN, Yan JX, Qin WW, Liu WS, Wang R. A new rhodamine-based single
molecule multianalyte (Cu2þ, Hg2þ) sensor and its application in the biological
system. Dyes Pigm 2012;92:1083e90.
[53] Dong M, Ma T, Zhang A, Dong Y, Wang Y, Peng Y. A series of highly sensitive
and selective fluorescent and colorimetric “off-on” chemosensors for Cu (II)
based on rhodamine derivatives. Dyes Pigm 2010;87:164e72.
[54] Jana A, Kim JS, Jung HS, Bharadwaj PK. A cryptand based chemodosimetric
probe for naked-eye detection of mercury(II) ion in aqueous medium and its
application in live cell imaging. Chem Commun 2009:4417e9.
AND logic gate based on electric dichroism of
a photochromic dihy-
droindolizine. Angew Chem Int Edit 2005;44:7591e4.
[34] Bhalla V, Vij V, Dhir A, Kumar M. Hetero-oligophenylene-based AIEE material
as a multiple probe for biomolecules and metal ions to construct logic circuits:
application in bioelectronics and chemionics. Chem Eur J 2012;18:3765e72.
[35] Szacilowski K. Molecular logic gates based on pentacyanoferrate complexes: from
simple gates to three-dimensional logic systems. Chem Eur J 2004;10:2520e8.
[36] Mishra RK, Upadhyay KK. Coumarin-based chromogenic receptor for Ni2þ in
aqueous medium exhibiting a reconfigurable logic gate pattern. Eur J Org
Chem 2011:4799e805.
[37] Maligaspe E, D’Souza F. NOR and AND logic gates based on supramolecular
porphyrin-fullerene conjugates. Org Lett 2009;12:624e7.
[38] Li A-F, Ruan Y-B, Jiang Q-Q, He W-B, Jiang Y-B. Molecular logic gates and
switches based on 1,3,4-oxadiazoles triggered by metal ions. Chem Eur J 2010;
16:5794e802.