A bis-naphthalimide functionalized pillar[5]arene-based supramolecular π-gel acts as a multi-stimuli-responsive material

Article abstract of DOI:10.1039/c8nj03583k

In this work, a novel supramolecular π-gel has been constructed using a naphthalimide functionalized pillar[5]arene-based gelator (MP5). The gelator MP5 simultaneously contains a naphthalimide moiety as the π...π interaction site as well as a fluorophore. Interestingly, the MP5-based supramolecular π-gel (MP5-G) exhibits strong aggregation-induced emission (AIE). MP5-G exhibited good thermal-responsiveness, acid and base-responsiveness and cation and amino acid-responsiveness. Meanwhile, this supramolecular π-gel also shows selective fluorescence sensing for Fe³⁺via cation-π interactions with high selectivity and sensitivity, and the detection limit of MP5-G for Fe³⁺ is 6.06 × 10^?8 M. Even more meaningfully, MP5-G could remove Fe³⁺ from water solution with excellent recyclability and ingestion capacity, and the Fe³⁺ removal rate can reach up to 99.8%. Furthermore, the Fe³⁺ coordinated supramolecular gel, MP5-FeG, shows selective fluorescence “turn-on” sensing for l-Cys. The detection limit of MP5-FeG for l-Cys is 1.0 × 10^?8 M. Simultaneously, thin films based on these supramolecular gels were prepared, which were confirmed to be convenient test kits for detecting Fe³⁺ and l-Cys. In addition, these supramolecular π-gels could be used as sensitive ion sensors, sensitive logic gates and fluorescent display materials.

Full text of DOI:10.1039/c8nj03583k

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ISSN 1144-0546
PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
rsc.li/njc

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Bisꢀnaphthalimide functionalized pillar[5]areneꢀ based
supramolecular πꢀgel act as multiꢀstimuliꢀresponse
materials
Received 00th January 20xx,
Accepted 00th January 20xx
You-Ming Zhang*, Yong-Fu Li, Kai-Peng Zhong, Wen-Juan Qu, Hong Yao, Tai-Bao Wei and
Qi Lin*
DOI: 10.1039/x0xx00000x
www.rsc.org/
In this work, a novel supramolecular π-gel has been constructed by a naphthalimide functionalized pillar[5]arene-based
gelator (MP5). The gelator MP5 simultaneously contain naphthalimide moiety as π∙∙∙π interactions site as well as
fluorophore. Interestingly, the MP5-based supramolecular π-gel (MP5-G) has strong aggregation-induced emission (AIE).
The MP5-G exhibited good thermal-responsiveness, acid and base-responsiveness, cations and amino acids-
responsiveness. Meanwhile, this supramolecular π-gel also show selective fluorescent sensing for Fe3+ via cation-π
interactions with high selectivity and sensitivity, the detection limits of the MP5-G for Fe3+ is 6.06×10-8 M. Even more
meaningful, the MP5-G could remove Fe3+ from water solution with excellent recyclability and ingestion capacity, the Fe3+
removal rate can reach up to 99.8%. Furthermore, Fe3+ coordinated supramolecular gel MP5-FeG show selective
fluorescent “turn-on” sensing for L-Cys. The detection limits of the MP5-FeG for L-Cys is 1.0×10-8 M. Simultaneously, thin
films based on these supramolecular gels were prepared, which was confirmed to be a convenient test kits for detecting
Fe3+ and L-Cys. In addition, these supramolecular π-gels could be used for sensitive ions sensors, sensitive logic gates as
well as fluorescent display materials.
to their versatile applications in the field of molecular
15
Introduction
machine,
supramolecular polymers,16 self-assembly,17
sensors,18 transmembrane channels,19 drug delivery systems,20
gas adsorption and storage,21 metal-organic frameworks,22 and
so on.23 Because of their intrinsic unique rigid, electron-
donating cavities, symmetrical pillar architecture, and facile
modification properties.24,25 In addition, pillar[n]arenes have
various supramolecular assembly driving forces including C-
H∙∙∙π, π∙∙∙π, cation∙∙∙π, hydrophobic/hydrophilic, etc.26-28 These
properties not only afforded pillar[n]arenes excellent
capability to selectively bind different kinds of guests,29 but
also endowed with a novel and appealing platform for the
construction of numerous interesting supramolecular systems
As we all know, stimuli-responsive properties play an essential
role in the fields of material,1 environmental fields2 and
biological science.3 For instance, many biological processes and
smart materials depend on certain stimuli-responsiveness to
achieve their special functions.4-6 Recently, supramolecular π-
gels, which are formed by π-gelators tend to form 1D
aggregates directed by intermolecular interactions, especially
π–π interactions,7,8 followed by intertwining into a 3D network,
have attracted much attention due to they are sensitive to
external stimuli such as chemicals, heat, mechanical forces,
sound and light. 9-11 In addition, on account of the dynamic and
30-35
as well as supramolecular gels.36-39 Although many
reversible nature of self-assembly, supramolecular π-gel has
supramolecular materials based on pillar[n]arenes have been
reported, however, the construction of supramolecular π-gel
by bis-naphthalimide functionalized pillar[5]arene based
sensor has not been extensively studied.
Fe3+, one of the most indispensable physiologically relevant
metal ions, performs crucial and versatile roles in many
enzymatic electron transfer, oxygen transport, oxidation
reactions, DNA and RNA synthesis, physiological and
pathological processes.40-42 Both deficiency and excess
accumulation in the human body can induce various diseases
related to intelligence decline, anemia, heart failure, cancers,
and dysfunction of central nervous system.43,44 Also, Fe3+ was
important pollutant source of the environment. Cysteine (L-
become a wonderful candidate for a class of new stimuli-
responsive materials as well as chemosensors.12,13
Pillar[n]arenes,14 a new class of macrocyclic host molecules
have become one of the favorite topics since 2008 attributed
a.Key Laboratory of Eco-Environment-Related Polymer Materials, Ministry of
Education of China; Key Laboratory of Polymer Materials of Gansu Province;
College of Chemistry and Chemical Engineering, Northwest Normal University,
Lanzhou, Gansu, 730070. P. R. ChinaE-mail: zhangnwnu@126.com
linqi2004@126.com.
b.Fax: +86 9317973191; Tel: +86 9317973191
c. †Electronic Supplementary Informaꢀon (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
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Cys) is one of the sulfhydryl-containing small molecular amino
A
novel
naphthalimide
functionalized-pillar[5]arene
acids that play significant roles in many pathological and derivative
(
MP5) was firstly synthesized by rationally
physiological processes.45 Thus, the monitoring and detection connecting a pillar[5]arene moiety and a 1,8-naphthalimide
of Fe3+ and L-Cys was very significant in both biosystem and group via alkyl chain (Scheme 1). MP5 and its intermediate
environment. Although numerous molecular recognition have been characterized by 1H NMR, 13C NMR, and ESI mass
methods have been reported, it still has remained a challenge spectrometry (Fig. S1–S12, ESI†). At first, the self-assembly and
to develop a sensor that possesses the required rapid and gelation properties of MP5 were examined in various solvents
efficient detection, low cytotoxicity, easy operation and high by means of the “stable to inversion of a test tube” method
sensitivity and selectivity.
(Table S1, ESI†). As a result, the MP5 could self-assemble into a
-gel incyclohexanol solution. The
and stimuli-responsive supramolecular critical gelation concentration (CGC) is 5% (w/v 10 mgmL-1
In view of the above and with arousing interesting in stable supramolecular
π
46-48
chemosensors
=
functional materials.49-51 Herein we demonstrate a novel 1%). while the gel-sol transition temperature (Tgel) is 43~45 °C.
approach for design of multi-stimuli-response materials by Furthermore, the sol–gel state can change rapidly in
using bis-naphthalimide functionalized pillar[5]arene (MP5)- cyclohexanol solution. After cooling the cyclohexanol solution
based supramolecular π-gel. Our strategies for the design of of MP5, the stable gel MP5-G was gained within 1 min (Fig. 1).
the organic gelator are as follows. Firstly, we introduced This gel was found to be stable in closed test tube for at least
pillar[5]arene moiety into the gelator as multi-functional self- five weeks at room temperature. Interestingly, as shown in Fig.
assembly sites, which could afford driving forces including 2, the hot (T > Tgel) cyclohexanol solution of supramolecualr
CH∙∙∙π and π∙∙∙π interactions. Secondly, a naphthalimide group polymer MP5 has negligible fluorescence. However, with the
was introduced into the gelator, which could act as π∙∙∙π temperature of the hot solution dropping below the Tgel (T <
interactions site as well as fluorophore. Thirdly, we rationally Tgel), the emission intensity at 505 nm showed a sudden
introduced the competition of π∙∙∙π stacking and cation-π
interactions to achieve the sensitive response. Interestingly,
the MP5 could self-assemble into a stable supramolecular
gel (MP5-G) with strong aggregation-induced emission (AIE) in
cyclohexanol. Moreover, the supramolecular -gel MP5-G
π-
π
shows perferable thermal-responsiveness, acid and base-
responsiveness, cations and amino acids-responsiveness.
Meanwhile, this supramolecular
Fe3+ and L-Cys as well as efficiently remove Fe3+ in water. Much
more importantly, this new approach provides good
π-gel could successively sense
a
potential for practical application in highly sensitive detection
of ions, fluorescent display materials as well as sensitive logic
gates.
Results and discussion
Fig. 1 The gel–sol transitions of the supramolecular π-gel
triggered by different stimuli.
Fig. 2 Fluorescence spectra of supramolecular π-gel MP5-G
(in gelated state) and solution in cyclohexanol (5% w/v).
Scheme 1. Synthesis of the gelator molecule MP5
.
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high-molecular-weight supramolecular polymers.54 In the 2D
NOESY spectrum (Fig. S14, ESI†) of MP5 shows cross peaks A, B,
C and D representing the correlations, which imply that
naphthalene diimide was not threaded into the cavity of
pillar[5]arene MP5. These results further revealed that the
gelator MP5 could self-assemble to supramolecular π-gel MP5-
G
via π-π stacking interactions, which existing between
pillar[5]arene groups and naphthalimide groups of the gelators.
Additionally, in the 2D DOSY NMR spectrum (Fig. S15, ESI†) of
MP5 shows cross peaks A and B representing the correlations.
These results support the above possible assembly
mechanisms. As seen in Fig. 4, under the scanning electron
microscope (SEM) and transmission electron microscope (TEM),
the morphological features of MP5 powder shows an irregular
block structure. Whereas, the xerogel of MP5-G shows a
regular microsphere structure. These results suggest that a
macroscopical change took place in the MP5 assembled into
supramolecular π-gel. Moreover, the small-angle XRD patterns
also support the described assembly mechanisms. The XRD of
Fig. 3 1H NMR spectra 1H NMR spectra (600 MHz, 298 K) of
MP5 in DMSO-d6 at various concentrations: (a) 4.3×10-3 M;
(b) 7.2×10-3 M; (c) 1.4×10-2 M; (d) 2.9×10-2 M; (e) 4.3×10-2
M; (f) 7.2×10-2 M.
increase, finally it reached a steady state at λem = 535 nm (Fig.
S13, ESI†). Meanwhile, the MP5 solution changed into a stable
gel and showed strong yellow fluorescence under excitation at
365 nm with a hand-held UV lamp, indicating that the
fluorescence of MP5-G could be attributed to the aggregation-
induced emission (AIE).52,53
The self-assembly mechanism of the MP5-G was carefully
explored via 1H NMR, 2D NOESY NMR, 2D DOSY NMR, SEM,
TEM and X-ray. At first, we carried out the concentration-
dependent 1H NMR of MP5 (Fig. 3), as the concentration
increased, the signals of protons Ha, Hb and Hc on naphthalene
rings showed obvious upfield shifted, at the same time, the
signal of proton Hd also showed obvious upfield shifted,
indicating that the π-π stacking interactions between the
naphthalene rings and pillar[5]arene groups were involved in
the self-assembly process. Moreover, all the signals became
broad at high concentration, which confirmed the formation of
Fig. 5 (a) Structure of MP5; (b) proposed assemble and
stimuli-response mechanisms of MP5 with Fe3+ and L-Cys;
(c) MP5-G upon adding various cations in and MP5-FeG
upon adding various amino acids in, which was taken under
Fig. 4 SEM images of (a) MP5; (b) MP5-G; (c) TEM image of
MP5-G; (d) SEM images of MP5-FeG; (e) MP5-FeG+L-Cys
(f) TEM image of MP5-FeG+L-Cys
;
an UV-lamp (365 nm) at room temperature.
.
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xerogel MP5-G showed peak at 2θ = 22.7394° corresponding
to the d-spacing 3.89 Å (Fig. S16, ESI†), which further
confirmed that the π-π stacking existed in naphthalimide
groups as well as the pillar[5]arene groups. According to the
above phenomena, the proposed self-assembly process of the
organogelator MP5 is illustrated in Fig. 5. First, the MP5 self-
assembled into one-dimensional linear supramolecular
chains via π-π stacking interactions. Then the supramolecular
-gel chains formed two-dimensional supramolecular
π-gel
π
networks via the π-π interactions existing in naphthalimide
groups as well as pillar[5]arene groups. Finally, the two-
dimensional networks were extruded into microspheres by the
hydrophobic interaction (Fig. 4b).
The response to external stimuli was a significant property
for supramolecular π-gel. Therefore, stimuli-responsive
behaviors of the supramolecular π-gel MP5-G were
investigated. As shown in Fig. 1, after the addition of several
drops of the triethylamine and CH3COOH solution, the
Fig. 7 Fluorescent response of MP5-G (5% w/v) upon
addition of 1 M Fe3+ (λex = 375 nm) in cyclohexanol system.
supramolecular π-gel dissociated into
a turbid solution.
solution, while excited at λex = 375 nm. When adding and
diffusing water solution of Fe3+ to the supramolecular
Correspondingly, in the 1H NMR spectrum (Fig. S17 and Fig.
S18, ESI†), Ha, Hb, Hc, Hd and He signals of MP5 showed a
barely highfield shift. This result also suggested that
intermolecular π-π stacking interactions are destroyed. It's
worth noting that subsequent addition of CH3COOH and
ammonia water solution to the turbid solution, respectively.
π-gel
MP5-G, resulted in a decrease of about 80% fluorescence
quenched in the fluorescence spectrum. Meanwhile, the MP5-
G
changed into the Fe3+ coordinated metallogel (MP5-FeG).
Other cations could not induce any significant changes. Thus,
this supramolecular
-gel (MP5-G) could effectively sense Fe3+
π
with specific selectivity.
Led to the recovery of gel state
.
Furthermore, in order to determine the detection limits of
MP5-G for Fe3+, we carried out fluorescence emission titration
experiments. The emission spectral variation of MP5-G upon
gradual addition of Fe3+ is shown in Fig. 7. In the fluorescence
spectrum, upon addition of increasing amounts of Fe3+ (0–2.7
equiv.) to the solution of MP5-G in cyclohexanol, the emission
intensity at 535 nm is gradually decreased. The detection limit
of the fluorescent spectrum change was figured out on the
basis of 3δ/S55 method is 6.06×10-8 M (Fig. S19, ESI†),
indicating that the MP5-G can detect Fe3+ at very low
concentrations in the environment. Compared with other
reported fluorescent sensors for Fe3+ (Table S2, ESI†), this work
showed a lower detection limit. Moreover, the MP5-G could
also detect Fe3+ in solid samples. When iron (III) perchlorate
Then, we carefully investigated the metal ions response
properties of the supramolecular -gel (MP5-G), we carried
π
out a series of host−guest sꢀmuli-response experiments. The
recognition profiles of MP5-G toward various cations
(including Mg2+, Ca2+, Cr3+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Ag+, Cd2+,
Hg2+, Al3+, Ba2+, Pb2+, La2+, Eu3+ and Tb3+) were primarily
investigated using fluorescence spectroscopy. As shown in (Fig.
6 and Fig. 5 (c)). In the fluorescence spectrum, the maximum
emission of MP5-G appeared at 535 nm in cyclohexanol
hexahydrate (0.0089 g, 2.7 equiv.) was added into the MP5-G
,
the fluorescence of MP5-G also been quenched (Fig. S20, ESI†),
which showed a good detection result in real solid samples.
It is well known that amino acids are the most basic
substances that make up
a protein and have a close
relationship with biological life activities. The successively
response ability of MP5-FeG towards amino acids has been
further investigated by adding and diffusing various amino
acids, including L-Phe, L-Gln, L-Ile, L-Thr, L-Glu, L-Ala, L-Ser, L-
Met, L-Val, L-Tyr, L-Arg, L-Asp, L-Pro, L-His, L-Leu, L-Gly, L-Trp,
L-Lys, L-Asn and L-Cys (water solution, C = 0.1M) to the MP5-
FeG, respectively. As expected, the metallogel MP5-FeG
showed excellent fluorescence changes according to the
Fig. 6 Fluorescence spectra of MP5-G (0.036M) and MP5-G
(in gelated state) in the presence of various cations (2
equiv., Mg2+, Ca2+, Cr3+, Hg2+, Co2+, Ni2+, Cu2+, Zn2+, Ag+,
Cd2+, Fe3+, Al3+, Ba2+, Pb2+, La2+, Eu3+ and Tb3+).
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- +
corresponding to [MP5+Fe3++2ClO4 ] , which revealed a 1:1
stoichiometry for the complexation between MP5 and Fe3+. No
peaks related to the complexes with other stoichiometries
were found. Further evidence obtained by IR experiments (Fig.
S24, ESI†). For instance, in the FT-IR spectra of the MP5-G, the
stretching vibration absorption of -C
while with the addition of Fe3+ into the MP5-G, the -C
absorption peak shifted to 1701 cm-1. This result indicated that
Fe3+ coordinated with MP5-G through -C
O on naphthalimide
=
O appeared at 1705 cm-1,
=
O
=
group. What more, the stretching vibration absorption of
naphthyl =C-H appeared at 2933 cm-1. While, with the addition
of Fe3+ into the MP5-G, the =C-H absorption peak shifted to
2928 cm-1, which was attributed to the Fe3+ interact with
naphthyl group in MP5-G via the cation-π interactions. The
coordination interactions and cation-π interactions induce the
electron transfer from MP5 to Fe3+, which induced the
fluorescence of MP5 gel quenching. As we expected,
subsequent addition of L-Cys into the metallogel MP5-FeG, the
-C=O and =C-H stretching vibration recovered to their original
position. These results manifested that after addition L-Cys in
MP5-FeG, the L-Cys competitively binds with Fe3+ and the -C=O
and naphthyl (=C-H) groups of the MP5 released again.
Meanwhile, the fluorescence of MP5 gel recovered. In addition,
XRD also support this proposed mechanism. The X-ray
diffraction patters of xerogel MP5 showed peak at 2θ =
22.7394° corresponding to the d-spacing 3.89 Å, whereas, this
Fig. 8 Fluorescence spectra of metallogel MP5-FeG (5%,
MP5-G:Fe3+ = 1:2) and MP5-FeG (in gelated state) in the
presence of various amino acids (C = 0.1M water solution)
in cyclohexanol system (λex = 375 nm).
stimuli of the L-Cys. As shown in Fig. 8 and Fig. 5 (c), the MP5-
FeG could selectively sense L-Cys by fluorescence “turn on”.
While other amino acids such as L-Phe, L-Gln, L-Ile, L-Thr, L-Glu
L-Ala, L-Ser, L-Met, L-Val, L-Tyr, L-Arg, L-Asp, L-Pro, L-His, L-Leu,
L-Gly, L-Trp, L-Lys, and L-Asn could not induce any obvious
fluorescence changes. Therefore, the MP5-FeG could
selectively sense L-Cys in water solution. Moreover, as shown
in Fig. S21, the MP5-FeG also showed high sensitivities for L-
Cys. With the gradual addition of L-Cys, the emission intensity
at 480 nm increased along with increasing concentrations of L-
Cys. The detection limits of the changes in fluorescence
spectra calculated on the basis of cL = ksB/S (where sB is the
standard deviation of the blank measures, S is the sensitivity of
peak disappeared after adding Fe3+ into the xerogel of MP5
.
Notably, when adding L-Cys into the MP5-FeG, the strong peak
at 2θ = 22.6140° corresponding to the d-spacing of 3.93 Å
appeared again (Fig. S16, ESI†). In the corresponding SEM
image (Fig. 4), the image demonstrated that the powder of
MP5 showed irregular flake structure (Fig. 4a). While the
xerogel of MP5-G showed regulate spherical structure (Fig. 4b).
After the addition of Fe3+ to MP5-G, the regular spherical
structure was destroyed (Fig. 4c), which could be attributed to
Fe3+ form stable metallogel MP5-FeG via cation-π interactions
with MP5 and the π-π stacking within MP5 was destroyed.
However, after the addition of L-Cys into the MP5-FeG, the
SEM image showed the microsphere structure was recovery
(Fig. 4d). These results indicated L-Cys is competitively bound
with Fe3+ and MP5-FeG changes into MP5-G again. These
above phenomena are strongly and sufficiently indicated that
the MP5 response Fe3+ and L-Cys through the competition of
π-π stacking and cation-π interactions.
55
the method, and k = 3) was 1.0×10-8 M for L-Cys (by MP5-
FeG). Which indicated that the MP5-FeG has highly sensitive
response ability for L-Cys in the environment.
The above competitive binding mechanism is also supported
by the reversibility of the sensing process. The reversibility in
the response of MP5-G was further verified during three cycles
of titration by alternating the addition of Fe3+ and L-Cys to the
MP5-G
.
The
fluorescence
emission
of
MP5-G
exhibited reversible processes in a sequence as shown in Fig.
S22. Specifically, the Fe3+ results in quenching of the
fluorescence intensity and hence acts as an OFF switch
through complex formation. The addition of an excess amount
of L-Cys to the mixture of MP5-G and Fe3+ exhibits a
remarkable fluorescence change by showing ON behavior. This
“ON–OFF–ON” switching process could be repeated several
times with only a slight loss in fluorescent efficiency.
To facilitate the practical application of the fluorescent
supramolecular π-gel MP5-G
, Fe3+ responsive films based on
The stimuli-response mechanism of the supramolecular gels
was carefully investigated by ESI-MS, IR, X-ray and SEM.
Electrospray ionization mass spectrometry of MP5 and Fe3+
Fig. 9 Writing and erasing of a natural light invisible image
on MP5-G-based film. The photographs were taken at
room temperature under nature light (N) and exposure to
a 365 nm ultraviolet light (UV).
exhibited peaks at m/z
= 1652.4023 (Fig. S23, ESI†),
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this π
solution of MP5
-gel were prepared by pouring the heated cyclohexanol concentration of Fe3+ was quantified to be about 1.0 × 10-6 M.
onto the clean glass surface and then drying This result is consistent with the reported literature.56 Analyses
-G
in the air. As shown in Fig. 9, the MP5-G film showed a yellow of these spectra suggested that the sensor could efficiently
fluorescence emission under UV at 365 nm. When Fe3+ ions detect Fe3+ in water, confirming MP5-G to be a promising Fe3+
were added to the thin film, the obvious color change was probe for practical applications.
observed under irradiation at 365 nm using a UV lamp. In
Molecular logic is an interdisciplinary research field, which
has aroused worldwide interest.57,58 Due to the MP5-G has a
highly sensitive and reversible response for Fe3+ and L-Cys,
MP5-G could act as a Fe3+ and L-Cys responsible sensitive
IMPLICATION logic gate. In this system (Fig. 10), the two
chemical inputs of Fe3+ and L-Cys are designated as (In Fe3+)
addition, when water solution of L-Cys was added,
fluorescence can be effectively restored. Therefore, the MP5-G
film could act as not only a convenient reversible Fe3+
detection test kits, but also an erasable security fluorescent
display material.
In order to demonstrate the capture of Fe3+ from water, the and (In L-Cys) for the Set (S) and Reset (R) inputs, we defined
xerogel sample of MP5-G (0.70 mg) was suspended in a dilute their absence as “0” and their presence as “1”. The output was
aqueous solution of Fe(ClO4)3.6H2O (0.23 mg in 5.0 mL). After the fluorescence single change of the MP5-G
. The ON state
the mixture was stirred at room temperature for 10 h, the (Output fiuorescence signal = 1) is defined as the strong
precipitate was separated by centrifugation (20 min) and emission, whereas the OFF state (Output fiuorescence signal =
gained the supernatant liquor (5 mL). The inductively coupled 0) corresponds to the quenched emission. The operation of
plasma (ICP) analysis verified that the concentration of the this memory unit is as follows: with no input (0, 0), the output
residual Fe3+ in water was less than 0.2 ppm, indicating that was “1”. With Fe3+ (1, 0) input alone, the fluorescence
over 99.8% of Fe3+ could be effectively absorbed and removed intensity was extremely weak and the output was “0”.
even in extremely dilute solutions (Table S3, ESI†). Similarly with L-Cys (0, 1) input alone, the fluorescence
Furthermore, in order to investigate the recyclability of the intensity was extremely strong and the output was “1”. When
MP5-G, after absorbing Fe3+, the MP5-G could be extracted by the system was subjected to the two inputs together (1, 1), the
using dichloromethane. Reuse of the recycled MP5-G showed fluorescence single increased obviously, giving an output signal
almost no loss of activities in the capture of Fe3+ (Fig. S25, ESI†). of “1”. It is noteworthy that the present logic device has a
These properties are very crucial for the potential applications great advantage over previous reported related systems at
of the MP5-G for recyclable separation of Fe3+ in water least in terms of the reversible sensitive characteristics as well
solution.
as potential applications for successive detection of transition
metals and amino acids.
In addition, the MP5-G could acts as a convenient and sensi-
tive sensor for Fe3+ in real samples. To further testify the
potential of MP5-G probe for practical applications as well as Conclusions
to realize its applicability in actual samples. For example, we
successfully applied MP5-G to detect Fe3+ in tap water (Fig.
In summary, a novel supramolecular
constructed by bis-naphthalimide functionalized pillar[5]arene
MP5). This supramolecular -gel MP5-G exhibited favorable
π-gel (MP5-G) was
S26, ESI†). The detection results revealed that the
(
π
thermal-responsiveness, acid and base-responsiveness, cations
and amino acids-responsiveness. Meanwhile, the MP5-G could
successively sensitive response Fe3+ and L-Cys by the
competition of π-π stacking and cation-π interactions in gel
states. Interestingly, the MP5-G shows excellent recyclable
separation properties for Fe3+. In addition, the MP5-G has
good potential for fluorescent display materials as well as
sensitive logic gates. More importantly, the strategy
“competition of π-π stacking and cation-π interactions” in
supramolecular π-gel provides a novel and facile methodology
to synthesize smart stimuli-responsive supramolecular
materials for sensitive detection, fluorescent display,
molecular logic gates and so on.
Conflicts of interest
Fig. 10 (a) The sequential logic circuit of the
memorymachine and its truth table. (b) Feedback loop
showing the reversible logic operations for the memory
“There are no conflicts to declare”.
element
functions.
with
“Reading–Erasing–Reading–Writing”
Acknowledgements
6 | J. Name., 2012, 00, 1-3
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DOI: 10.1039/C8NJ03583K
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New Journal of Chemistry
Page 8 of 8
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DOI: 10.1039/C8NJ03583K
Graphical abstract
Bisꢀnaphthalimide
functionalized
pillar[5]areneꢀ
based
supramolecular πꢀgel act as multiꢀstimuliꢀresponse materials
YouꢀMing Zhang,* YongꢀFu Li, KaiꢀPeng Zhong, WenꢀJuan Qu, Hong Yao, TaiꢀBao
Wei and Qi Lin*
Key Laboratory of Eco-Environment-Related Polymer Materials, Ministry of
Education of China; Key Laboratory of Polymer Materials of Gansu Province;
College of Chemistry and Chemical Engineering, Northwest Normal University,
Lanzhou, Gansu, 730070. P. R. China
A novel and efficient approach for design of multiꢀstimuliꢀresponse supramolecular
functional materials was successfully developed by introducing the competition of πꢀπ stacking
and cationꢀπ interactions into
a novel bisꢀnaphthalimide functionalized pillar[5]arene
(MP5)ꢀbased supramolecular πꢀgel (MP5ꢀG). The MP5ꢀG show reversible AIE fluorescent
“ONꢀOFFꢀON” sense for Fe3+ and LꢀCys. Moreover, this MP5ꢀG has good potential practical
application in detection and adsorption of ions, multiꢀstimuliꢀresponse materials, fluorescent
display materials as well as sensitive IMPLICATION logic gates.