A Supramolecular Artificial Light-Harvesting System with Two-Step Sequential Energy Transfer for Photochemical Catalysis

Article abstract of DOI:10.1002/anie.201912654

An artificial light-harvesting system with sequential energy-transfer process was fabricated based on a supramolecular strategy. Self-assembled from the host–guest complex formed by water-soluble pillar[5]arene (WP5), a bola-type tetraphenylethylene-funct

Full text of DOI:10.1002/anie.201912654

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Accepted Article
Title: A Supramolecular Artificial Light-harvesting System with Two-
step Sequential Energy Transfer for Photochemical Catalysis
Authors: Min Hao, Guangping Sun, Minzan Zuo, Zuqiang Xu, Yuan
Chen, Xiao-Yu Hu, and Leyong Wang
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201912654
Angew. Chem. 10.1002/ange.201912654
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10.1002/anie.201912654
Angewandte Chemie International Edition
RESEARCH ARTICLE
A Supramolecular Artificial Light-harvesting System with Two-
step Sequential Energy Transfer for Photochemical Catalysis
Min Hao,# Guangping Sun,# Minzan Zuo,# Zuqiang Xu, Yuan Chen, Xiao-Yu Hu,* and Leyong Wang*
Abstract: An artificial light-harvesting system with sequential
energy-transfer process is successfully fabricated in aqueous
environment based on the supramolecular strategy. Self-assembled
from the hostguest complex formed by water-soluble pillar[5]arene
(WP5) and a bola-type tetraphenylethylene-functionalized dialkyl
ammonium derivative (TPEDA), as well as two fluorescent dyes,
Eosin Y (ESY) and Nile Red (NiR), the obtained supramolecular
vesicles can achieve efficient energy transfer from the AIE guest
light-harvesting systems are constructed by non-covalent
interactions between chlorophyll and protein. Therefore,
compared with traditional artificial light-harvesting systems via
covalent bonds, supramolecular light-harvesting systems
constructed by noncovalent interaction are usually easy to be
fabricated without multiple synthesis.[4]
So far, most research has focused on the construction of light-
harvesting systems in organic solvents[5] rather than in the
aqueous environment as the natural photosynthesis system.
Since the energy donors are usually hydrophobic, the organic
system can avoid the ACQ effect induced by water, and thus
high energy transfer efficiency can be achieved compared with
that in aqueous solution. Therefore, fabricating efficient light-
harvesting systems in water to mimic the natural processes
remains a challenging task, which has aroused great interest
among researchers.[6] For instance, Liu et al. demonstrated that
an oligo(phenylenevinylene) derivative could effectively inhibit
the ACQ effect and exhibited outstanding energy transfer
efficiency in water.[7] Our group has previously reported an
artificial light-harvesting system based on a salicylaldehyde
azine derivative which showed aggregation-induced emission
(AIE) effect instead of the ACQ phenomenon.[8] However, most
of these systems contain only one-step direct FRET process
from donors to acceptors, while the natural light-harvesting
system with excellent efficiency is characterized by multi-
channel information communication.[9] Besides, the use of
harvested solar energy for further photochemical catalysis has
been rarely addressed. Thus, to better understand and mimic
the natural light-harvesting antenna systems, establishing the
multi-step sequential FRET systems with the capability to
convert solar energy into chemical energy in aqueous
environment is of great significance.[10]
TPEDA to ESY at
a
high energy-transfer efficiency and
donor/acceptor ratio. Moreover, ESY can function as a relay to
further transfer the energy to the second acceptor NiR and realize
the two-step sequential energy-transfer process with good efficiency.
By properly tuning the ratio between the donor and acceptors, bright
white light emission can be successfully achieved with a CIE
coordinate of (0.33, 0.33). More importantly, to better mimic the
natural photosynthesis and make full use of the harvested energy,
the WP5TPEDA-ESY-NiR system can be utilized as a nanoreactor,
where photocatalysed dehalogenation of α-bromoacetophenone can
be realized with 96% yield in aqueous medium.
Introduction
Light-harvesting systems play an important role in natural
photosynthesis for converting light energy into chemical
energy,[1] which paves a prospective way for the exploitation of
renewable energy resources. In recent years, more and more
attention has been paid to mimic natural light-harvesting
systems because of their considerable potential applications in
the field of biological imaging and optoelectronic devices.[2]
Inspired by nature, there are two crucial prerequisites to realize
efficacious energy transfer from a donor to an acceptor through
the Förster resonance energy transfer (FRET) process.[3] Firstly,
the donor should be not only densely packed but also needs to,
in the meantime, avoid intramolecular self-quenching of
fluorescence caused by the aggregation-caused quenching
(ACQ) effect. Secondly, the ratio of the donor and acceptor
should be relatively high to make sure that multiple donors
correspond to one acceptor. It is noteworthy that efficient natural
Herein, we report the fabrication of a novel artificial light-
harvesting system based on the noncovalent supramolecular
assembly between a water-soluble pillar[5]arene (WP5) and a
bola-type tetraphenylethylene-functionalized dialkyl ammonium
derivative (TPEDA),[11] which could realize two-step sequential
energy-transfer process in aqueous environment (Scheme 1).
Due to the unique property of AIE effect, TPE analogues in the
aggregated form can exhibit high emission,[12] which makes
TPEDA a remarkable donor in water. Meanwhile, WP5 could
function as an ideal host towards TPEDA to lower its critical
aggregation concentration as well as strengthen the AIE effect.
When WP5 was added into the aqueous solution of TPEDA,
stable hostguest inclusion complex could be formed and further
self-assembled into supramolecular nanoparticles. Driven by the
noncovalent interaction, an energy acceptor, the hydrophobic
fluorescent dye Eosin Y (ESY), could be successfully entrapped
into the hydrophobic core of the formed WP5TPEDA
vesicles.[13] Because of the well overlap between the emission
band of the WP5TPEDA complex and the absorption band of
ESY, efficient one-step energy-transfer process could take place
from WP5TPEDA vesicles to ESY. Furthermore, a two-step
sequential energy-transfer process could also be realized by the
simultaneous encapsulation of another carefully selected
[*]
M. Hao,# G. Sun,# M. Zuo,# Z. Xu, Y. Chen, Prof. Dr. X.-Y. Hu, Prof.
Dr. L. Wang
Key Laboratory of Mesoscopic Chemistry of MOE, Jiangsu Key
Laboratory of Advanced Organic Materials, School of Chemistry and
Chemical Engineering, Nanjing University
Nanjing, 210023, China
E-mail: lywang@nju.edu.cn
Prof. Dr. X.-Y. Hu
College of Material Science and Technology, Nanjing University of
Aeronautics and Astronautics
Nanjing, 211100, China
E-mail: huxy@nuaa.edu.cn
Prof. Dr. L. Wang
School of Petrochemical Engineering, Changzhou University
Changzhou, 213164, China
[#]
M. Hao, G. Sun, and M. Zuo contributed equally to this work.
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

10.1002/anie.201912654
Angewandte Chemie International Edition
RESEARCH ARTICLE
hydrophobic dye Nile Red (NiR) as the second energy acceptor.
Thus, this two-step energy-transfer process could initially take
place from WP5TPEDA vesicles to ESY and then to NiR at a
high energy-transfer efficiency and donor/acceptor ratio
([TPEDA]/[ESY]/[NiR] = 200:1:1). In addition, strong white light
emitting[1315] can also be achieved with the fabricated
WP5TPEDA-ESY-NiR supramolecular system. Significantly,
due to the AIE enhanced FRET process, undesired fluorescence
quenching could be avoided and the harvested solar energy
could be utilized to promote the photocatalysed dehalogenation
of α-bromoacetophenone with 96% yield in aqueous medium.
Before exploring the energy-transfer process, we first studied
the self-assembly behavior of the WP5TPEDA complex.
Neither Tyndall effect nor strong fluorescence could be observed
from the freshly prepared TPEDA solution (Figure S11,
Supporting Information). However, in the presence of WP5,
notable opalescence with obvious Tyndall effect could be
observed, suggesting the formation of large amounts of
WP5TPEDA supramolecular nanoparticles. Moreover, the free
TPEDA solution exhibited very dim fluorescence. On the
contrary, the WP5TPEDA solution showed significantly
enhanced fluorescence (Figure S11 and Figure S16, Supporting
Information), indicating that WP5 could induce the self-assembly
behavior of TPEDA, and the close-packed structure could
restrict the intramolecular rotation of TPEDA, which in return
resulted in the obvious AIE effect. Then the best molar ratio of
TPEDA and WP5 for aggregation was tested to be 5:1
([TPEDA]/[WP5]) by UV-visible spectroscopy (Figure S13,
Supporting Information). What’s more, the critical aggregation
concentration (CAC) of WP5TPEDA assembly was confirmed
to be 0.014 mM at the best molar ratio (Figure S14, Supporting
Information). The size and morphology of assemblies were
investigated by dynamic light scattering (DLS) and transmission
electron microscope (TEM) measurements, respectively.
WP5TPEDA nano-aggregates showed
a
narrow size
distribution with an average diameter of 180 nm (Figure 1a).
TEM images revealed a dark spherical structure (Figure 1b)
with a similar diameter as the DLS results, suggesting the
formation of multilayer vesicular structure. Zeta potential
measurements gave a relatively high positive ζ-potential (19.84
Scheme 1. Schematic illustration of the self-assembly of pillar[5]arene-based
aqueous light-harvesting system with two-step sequential energy transfer.
Results and Discussion
The synthesis of WP5[16] and pentyltrimethylammonium bromide
(GM)[17] were according to the reported methods, and guest
molecule
TPEDA
was
prepared
by
taking
4-
hydroxybenzophenone as the starting material (Scheme S1 and
Figure S1-S8, Supporting Information). Initially, 1H NMR
spectroscopic studies was conducted to investigate the host
guest binding ability between WP5 and TPEDA (Figure S9,
Supporting Information). Considering the complicated structure
of TPEDA may hamper the investigation of hostguest
association, GM with the same binding site as TPEDA was
utilized as the model compound. Figure S9 revealed that the
protons of the alkyl chain moiety (H2, H3, H4, H5, and H6) of GM
underwent manifest upfield shift due to the shielding effect of the
WP5 hydrophobic cavity, while the signals of the phenyl protons
(Ha) and methylene protons (Hb) of WP5 shifted downfield
slightly. These results convincingly demonstrated that GM
threaded into the electron-rich cavity of WP5. Moreover, the
association constant (Ka) between WP5 and TPEDA was
determined to be (1.69  0.27)  105 M-1 by Isothermal Titration
Calorimetry (ITC) (Figure S10, Supporting Information). Such
high binding affinity may attribute to the cooperative CH···,
electrostatic as well as hydrophobic interactions, leading to the
formation of stable amphiphilic hostguest complex.
Figure 1. DLS data of (a) WP5TPEDA assembly, (c) WP5TPEDA-ESY
assembly, and (e) WP5TPEDA-ESY-NiR assembly in water at 25 °C. TEM
images of (b) WP5TPEDA assembly, (d) WP5TPEDA-ESY assembly, and
(f) WP5TPEDA-ESY-NiR assembly. [WP5] = 1.0 × 10-5 M, [TPEDA] = 5.0 ×
10-5 M, [ESY] = 2.5 × 10-7 M and [NiR] = 2.5 × 10-7 M. Scale bar: 200 nm.
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10.1002/anie.201912654
Angewandte Chemie International Edition
RESEARCH ARTICLE
mV, Figure S15, Supporting Information), suggesting that the
electrostatic repulsive force around the surfaces of the
nanoparticles can prevent their agglomeration and further
improve the stability of the nanoparticles in aqueous solution.
transfer efficiency was calculated to be 74.39% at the molar ratio
of donor/acceptor = 200:1 (Figure S19b, Supporting Information).
Moreover, the antenna effect was calculated to be 11.5 at such
a high donor/acceptor ratio (Figure S21, Supporting Information)
and the fluorescence quantum yield was tested to be 7.27%
(Figure S18b and Table S2, Supporting Information). The above
results indicated that the WP5TPEDA assembly could function
as a promising light harvesting antenna in aqueous environment.
Since WP5 could obviously induce the AIE effect of TPEDA,
the fluorescence intensity of the system was significantly
enhanced with a fluorescence quantum yield of 15.63% (Figure
S18a and Table S2, Supporting Information), indicating that
WP5TPEDA assembly can be served as an ideal donor for the
construction of an artificial light-harvesting system in aqueous
solution. ESY, a hydrophobic fluorescent dye, was expected to
be a promising acceptor due to the following benefits: on one
hand, the absorption band of ESY overlaps very well with the
fluorescence emission of the WP5TPEDA assembly (Figure
S19a, Supporting Information). On the other hand, since the
WP5TPEDA inclusion complex tends to form tightly stacked
π–π stacking assembly, ESY can be easily entrapped into the
hydrophobic layer of the obtained WP5TPEDA vesicles via
noncovalent interaction, thus the distance between the donor
and acceptor will be significantly shortened, which ensures the
efficient FRET effect. Accordingly, the obtained ESY-loaded
WP5TPEDA assembly had an obviously increased average
diameter (Figure 1c and 1d) compared with the blank
nanoparticles. Subsequently, the fluorescent behavior of the
ESY-loaded vesicles was investigated. As shown in Figure 2a,
with the increasing concentration of ESY, the fluorescence
intensity of TPEDA (donor) at 480 nm decreased gradually,
while the fluorescence emission of ESY (acceptor) at 550 nm
increased when excited at 365 nm. In addition, the fluorescent
color changed from light blue of WP5TPEDA vesicles to bright
yellow-green of WP5TPEDA-ESY system (Figure 2a and
Figure S12c, Supporting Information). These phenomena are
consistent with the efficient energy transfer from the donor to the
acceptor. To further confirm the light-harvesting properties,
fluorescence decay experiments were conducted. The decay
curve of WP5TPEDA assembly was fitted as a double
exponential decay (Figure 2b), which showed the fluorescence
lifetimes of 1 = 1.79 ns and 2 = 5.40 ns (Figure S17a and Table
S1, Supporting Information). In addition, the fluorescence
lifetimes of WP5TPEDA-ESY system decreased to 1 = 1.15 ns
and 2 = 3.64 ns (Figure S17b and Table S1, Supporting
Information), indicating that the WP5TPEDA-ESY system
functions as an artificial light-harvesting system in which the
energy can be transferred from WP5TPEDA assembly to the
acceptor ESY. To quantitatively evaluate the efficiency of a light-
harvesting system, it is very necessary and important to know its
energy transfer efficiency and antenna effect. According to the
fluorescence quenching rate of WP5TPEDA assembly, energy
Considering that the photosynthetic light-harvesting system in
nature consists of multichromophoric assemblies for multi-step
sequential energy transfer rather than the simple one-step
energy transfer,[18] we further investigated the possibility of
sequential energy transfer process of the fabricated
supramolecular system. After systematic screening, NiR was
selected as a suitable acceptor for WP5TPEDA-ESY system
(Figure 1e and 1f), because the absorption band of ESY
overlaps well with the fluorescent emission of the WP5TPEDA-
ESY assembly. When the second acceptor NiR was added to
the WP5TPEDA-ESY system, the emission intensity at 550 nm
ascribed to ESY decreased and a new emission band of NiR at
610 nm appeared at the same time (Figure 3a, for full spectra,
see Figure S26 in Supporting Information). Moreover, the
fluorescent color changed from bright yellow-green of
WP5TPEDA-ESY assembly to off-white of WP5TPEDA-ESY-
NiR assembly (Figure 3a and Figure S12d, Supporting
Information). These observations indicated that a sequential
energy transfer process took place from WP5TPEDA-ESY
system to NiR, and ESY may function as a crucial bridge to
realize this sequential energy transfer in a relay mode. The
fluorescence quantum yield of WP5TPEDA-ESY-NiR system
was tested to be 5.01% (Figure S18c and Table S2, Supporting
Information), and the energy-transfer efficiency was calculated
to be 56.28% with the molar ratio of donor/acceptor I/acceptor II
= 200:1:1 (Figure S20b, Supporting Information). The antenna
effect was then calculated to be 3.5 at such
a high
donor/acceptor ratio (Figure S22, Supporting Information). To
further confirm the crucial role of ESY as a bridge for sequential
energy transfer, WP5TPEDA-NiR assembly was used as a
control treatment, as seen in Figure S24, the emission band of
the NiR could hardly be observed, indicating the very low
harvesting antenna effect between WP5TPEDA and NiR. The
above results also confirmed that the WP5TPEDA-ESY-NiR
assembly could function as sequential harvesting antenna in
aqueous environment.
Furthermore, fluorescence lifetime decay tests were also
performed to investigate the energy transfer process for the
Figure 3. (a) Fluorescence spectra of WP5TPEDA-ESY assembly in water
with different concentrations of NiR. Inset: photographs of WP5TPEDA-ESY
assembly and WP5TPEDA-ESY-NiR assembly. (b) Fluorescence decay
profiles of WP5TPEDA-ESY assembly (red line), and WP5TPEDA-ESY-
NiR assembly (blue line). [WP5] = 2 × 10-5 M, [TPEDA] = 1 × 10-4 M, [ESY] = 5
× 10-7 M, [NiR] = 5 × 10-7 M.
Figure 2. (a) Fluorescence spectra of WP5TPEDA assembly in water with
different concentrations of ESY. Inset: photographs of WP5TPEDA assembly
and WP5TPEDA-ESY assembly. (b) Fluorescence decay profiles of
WP5TPEDA assembly (black line), and WP5TPEDA-ESY assembly (red
line). [WP5] = 2 × 10-5 M, [TPEDA] = 1 × 10-4 M, [ESY] = 5 × 10-7 M.
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10.1002/anie.201912654
Angewandte Chemie International Edition
RESEARCH ARTICLE
WP5TPEDA-ESY-NiR systems. The decay curve of the
WP5TPEDA-ESY-NiR assembly showed the lifetimes of 1 =
storing for 24 hours, which might be suitable for further
application in light-emitting materials (Figure S25, Supporting
Information).
1.05 ns and 2
= 2.68 ns (Figure 3b). Therefore, the
fluorescence lifetime showed an initial decline from
WP5TPEDA assembly to WP5TPEDA-ESY assembly and a
further decrease from WP5TPEDA-ESY assembly to
WP5TPEDA-ESY-NiR assembly. These results can also jointly
validate the encapsulation of fluorescent dyes ESY and NiR into
the WP5TPEDA vesicles as well as the sequential energy
transfer in the relay mode.
To better mimic the natural photosynthesis process and make
full use of the harvested energy, the WP5TPEDA-ESY-NiR
system was utilized as
a nanoreactor to catalyze the
dehalogenation of α-bromoacetophenone in aqueous medium. It
is known that organic dyes can be used successfully in the
photoredox catalysis with specific light region due to their limited
absorption in other regions.[19] However, in the WP5TPEDA-
ESY-NiR system, the fluorescent chromophores exhibit
sequential harvesting antenna effect from the UV region to the
visible light region, thus full solar light spectrum can be used to
catalyze the chemical reaction. Accordingly, a Xenon lamp was
used as a solar light simulator for the photocatalysis reaction.[20]
Upon irradiation, the light energy can be transferred from the
donor to NiR through sequential FRET process. Meanwhile, the
Subsequently, the emission behavior of the WP5TPEDA-
ESY-NiR assembly was investigated. Since the WP5TPEDA
assembly acts as an AIE fluorophore, it may show
concentration-dependent fluorescence in a certain color range.
As expected, the color of the WP5TPEDA-ESY-NiR
nanoparticle solution turned from bluish violet to light blue
(Figure 4a) as the WP5TPEDA assembly changed from high
concentration (1 × 10-4 M) to low concentration (5 × 10-5 M). This
is probably because the WP5TPEDA inclusion complex at high
concentration presents a closely compact form to induce the
remarkable AIE effect. However, at low concentration,
WP5TPEDA inclusion complex prefer to keep a more loose
form and the AIE effect is decreased. Consequently, the
fluorescent color changed accordingly. Moreover, the
WP5TPEDA-ESY-NiR assembly also showed ratio-dependent
fluorescent changes. As the ratio of ESY increased (from
100:1:1 to 100:10:1), the color of the system changed from light
blue to bright yellow, indicating more efficient energy transfer
process from WP5TPEDA assembly to ESY. Thus, the sample
could display a strong white-light emission at a concentration of
5 × 10-5 M (TPEDA) with the ratio of [TPEDA]/[ESY]/[NiR] =
100:5:2 (Figure 4b). The color coordinate of the resulting
WP5TPEDA-ESY-NiR system was calculated as (0.33, 0.33)
in the CIE (Commission Internationale de l’Eclairage) xy
chromaticity diagram, which is exactly the pure white point and
could be perceived as white light-emitting materials. Under this
condition, the energy-transfer efficiency from WP5TPEDA
assembly to ESY was calculated up to 92.45% (Figure S23a,
Supporting Information) and the sequential energy-transfer
efficiency from WP5TPEDA-ESY assembly to NiR was 74.78%
(Figure S23b, Supporting Information), indicating the successful
construction of a white light-emitting material based on a
sequential energy transfer process in supramolecular systems.
Moreover, this white-light emission system was very stable after
WP5TPEDA-ESY-NiR vesicles could function as
a
nanoreactor to provide favorable space for the photocatalysis
reaction and makes it possible to perform organic reactions in
aqueous environment (Figure 5). As shown in Table 1, the
photocatalytic activities of fluorescent chromophores alone and
the light-harvesting system were both investigated. After
optimizing the reaction conditions (Table S3 and Figure S31-S33,
Supporting Information), for the WP5TPEDA-ESY-NiR group,
the yield of product acetophenone reached 96% after eight-hour
irradiation, which was dramatically increased compared with the
ESY + NiR group (Table 1 and Figure S27-28, Supporting
Information). And very low yield was obtained for the TPEDA
group as well as for the blank control without catalyst (Table 1
and Figure S29-S30, Supporting Information). Moreover, nearly
Figure 4. (a) CIE chromaticity coordinates of equal ratio WP5TPEDA-ESY-
NiR assembly at different concentrations (red arrow, from 5 × 10-5 M to 1 × 10-
4
M), equal concentration WP5TPEDA-ESY-NiR assembly at different ratios
(blue arrow, from 100:1:1 to 100:10:1), and the white-light-emitting coordinate.
(b) Fluorescence spectra of the white-light-emitting coordinate. Inset:
corresponding fluorescent image. [WP5] = 1 × 10-5 M, [TPEDA] = 5 × 10-5 M,
[ESY] = 2.5 × 10-6 M and [NiR] = 1 × 10-6 M.
Figure 5. A plausible mechanism for the dehalogenation reaction using
WP5TPEDA-ESY-NiR assembly as a nanoreactor in aqueous medium.
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10.1002/anie.201912654
Angewandte Chemie International Edition
RESEARCH ARTICLE
Table 1. Photocatalytic dehalogenation reaction of α-bromoacetophenone
in mimicking natural photosynthesis featuring facile integration
and multi-step energy transfer process.
using Hantzsch ester as a reduction equivalent.
Entry
Conditions
Light irradiation
Yield [%][b]
Experimental Section
1
2
3
4
5
None[a]
Yes
Yes
Yes
Yes
No
10
13
31
96
n.d.
TPEDA
Preparation of the Supramolecular Assembly Solutions. The
blank WP5TPEDA assembly solution was prepared as follows:
TPEDA (0.38 mg) was dissolved in DMSO (50 μL).
Subsequently, the above solution was added to the WP5
aqueous solution (0.02 mM, 5 mL) during ultrasonication within
ESY + NiR
WP5TPEDA-ESY-NiR
WP5TPEDA-ESY-NiR
30
s to generate the assembly solutions in water. The
WP5TPEDA-ESY and WP5TPEDA-NiR assembly solutions
were prepared as follows: TPEDA (0.38 mg) was dissolved in
ESY (50 μM)-containing or NiR (50 μM)-containing DMSO
solution (50 μL), respectively. The above mixed solutions were
added separately to WP5 aqueous solution (0.02 mM, 5 mL)
during ultrasonication within 30 s to generate the assembly
solutions in water. The WP5TPEDA-ESY-NiR assembly
solution was prepared as follows: TPEDA (0.38 mg) was
dissolved in DMSO solution (50 μL) containing ESY (50 μM) and
NiR (50 μM). The above mixed solution was added to the WP5
aqueous solution (0.02 mM, 5 mL) during ultrasonication within
30 s to generate the assembly solution in water.
[a] Dehalogenation reaction of α-bromoacetophenone without catalyst. [b]
Yield determined by GC using appropriate calibrated internal standards.
no catalytic activity was observed in dark for the WP5TPEDA-
ESY-NiR group. The high catalytic efficiency for the
WP5TPEDA-ESY-NiR system in aqueous medium may be due
to the fact that the loading of dyes into the hydrophobic layer of
the supramolecular vesicles could minimize the photobleaching
effect upon long-time irradiation. What’s more, the AIE effect of
the donor and the appropriate arrangement of the dyes within
restricted space can avoid the undesired fluorescence
quenching, which is highly beneficial to improve the light-use-
efficiency. Moreover, the wide region of the solar light can be
used to synergisticly trigger the photocatalysis. These results
suggest that the WP5TPEDA-ESY-NiR nanoreactor with good
photocatalytic ability can function as an efficient light-harvesting
system to make full use of the harvested solar energy and
convert it into chemical energy in aqueous phase. Thus, we
believe that such an efficient light-harvesting system with two-
step energy transfer process would provide a new insight into
the fabrication of artificial photosynthetic systems.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (No. 21572101, 21871136), and the Natural
Science Foundation of Jiangsu Province (No. BK20180055). L.
Wang is grateful to UM Macao Distinguished Visiting Scholar
Scheme.
Keywords: Hostguest interaction
• Supramolecular self-
Conclusion
assembly • Artificial light-harvesting • Sequential energy transfer
• White light emission
In summary,
a
sequential light-harvesting system with
outstanding efficiency based on facile supramolecular strategy
has been designed in aqueous solution. Owing to WP5-induced
self-assembly process, the obtained WP5TPEDA hostguest
amphiphile further assembled into supramolecular nanoparticles,
which exhibited significant AIE effect with dramatically enhanced
fluorescence compared to the free TPEDA solution. After non-
covalently encapsulation of the hydrophobic fluorescent dye
ESY, an artificial light-harvesting system was successfully
fabricated with efficient FRET process that occurred from the
donor (WP5TPEDA assembly) to the acceptor (ESY). What’s
more, when a second hydrophobic fluorescent dye NiR was
further entrapped into the WP5TPEDA assembly, a light-
harvesting system with two-step sequential energy transfer
could be achieved from WP5TPEDA to ESY and then to NiR.
More importantly, by tuning the ratio of these two different dyes,
the WP5TPEDA-ESY-NiR system could realize white light
[1]
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emission at
a
proportion of 100:5:2 (TPEDA/ESY/NiR).
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10.1002/anie.201912654
Angewandte Chemie International Edition
RESEARCH ARTICLE
RESEARCH ARTICLE
An artificial light-harvesting system
with two-step sequential energy
transfer process in a relay mode is
successfully fabricated in aqueous
environment based on the
Min Hao,# Guangping Sun,# Minzan
Zuo,# Zuqiang Xu, Yuan Chen, Xiao-Yu
Hu,* and Leyong Wang*
Page No. – Page No.
supramolecular strategy, which can be
used as a nanoreactor for efficient
photochemical catalysis. Moreover,
bright white light emission can be
successfully achieved with a CIE
coordinate of (0.33, 0.33).
A Supramolecular Artificial Light-
harvesting System with Two-step
Sequential Energy Transfer for
Photochemical Catalysis
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