Multi-component supramolecular gels induce protonation of a porphyrin exciplex to achieve improved collective optical properties for effective photocatalytic hydrogen generation

Article abstract of DOI:10.1039/c9cc08060k

Towards mimicking natural photosystems, supramolecular gels containing two types of porphyrins were developed for photocatalysis. Protonation and J-aggregation of porphyrins within gels expand the absorption to a wide range of visible wavelengths. Porphyrin exciplex formation renders a smaller bandgap for photo-induced electron generation. These features induce effective photocatalytic hydrogen generation.

Full text of DOI:10.1039/c9cc08060k

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Multi-component supramolecular gels induce
protonation of a porphyrin exciplex to achieve
improved collective optical properties for
effective photocatalytic hydrogen generation†
Cite this:DOI: 10.1039/c9cc08060k
Received 14th October 2019,
Accepted 3rd December 2019
Gengxiang Yang, Chenxiang Lin, Xuenan Feng, Tianyu Wang * and
DOI: 10.1039/c9cc08060k
Jianzhuang Jiang
*
rsc.li/chemcomm
Towards mimicking natural photosystems, supramolecular gels con- of free base porphyrins, namely 5,10,15,20-tetrakis(4-(hydroxyl)-
taining two types of porphyrins were developed for photocatalysis. phenyl)porphyrin (THPP) and 5,10,15,20-tetrakis(4-(carboxyl)-
Protonation and J-aggregation of porphyrins within gels expand the phenyl)porphyrin (TCPP), Scheme 1, for photocatalytic applications.
absorption to a wide range of visible wavelengths. Porphyrin exciplex Unexpectedly, the two types of porphyrins not only formed
formation renders a smaller bandgap for photo-induced electron exciplexes, but were also protonated under neutral conditions
generation. These features induce effective photocatalytic hydrogen upon gelation. The protonation and J-aggregation of porphyrins
generation.
expanded the absorption to a wide range of wavelengths. Depending
on the solvents for gelation, the nanostructures and properties of
Natural photosystems, such as plant photosystem I, are the assemblies can be thoroughly modulated, Scheme 1. These inter-
architectures of proteins and chromophores, which always have esting characteristics provided a smaller bandgap for photo-induced
delicate nanostructures.1 Multiple types of pigments are employed electron generation, good charge separation and efficient transpor-
by such natural photosystems for achieving efficient solar energy tation of photogenerated carriers.
conversion.2 It is worth noting that chromophores in natural light-
As a universal gelator, LBG can form supramolecular gels
harvesting complexes are not simply self-aggregated into huge with different guest organic molecules in diverse solvents.11 For
assemblies. Instead, co-assembly with protein scaffolds provides LBG/TCPP/THPP DMF gels, protonation and J-aggregation of
proper spatial organization of different chromophores.1–3
For the purpose of mimicking natural solar energy conversion,
development of photocatalytic systems based on supramolecular
assemblies has been attracting great interest.4–8 Although people
still cannot reproduce the complex nanostructures of natural
architectures like plant photosystem I, pioneering research
studies on supramolecular gels9 still open many new possibi-
lities for the fabrication of high-performance photocatalytic
systems via the self-assembly of small organic molecules.4 It is
noteworthy that multi-component supramolecular gels offer a
more flexible approach to tailor the properties of assemblies,10
and in principle have the advantages for mimicking natural
protein/porphyrin co-assemblies for light harvesting. However,
photocatalytic systems based on multi-component supramole-
cular gels are still rarely studied.
Herein, we report multi-component supramolecular gels
containing an L-glutamic acid derivative (LBG) and two types
Scheme 1 Molecular building blocks (LBG, THPP and TCPP) for forming
multi-component supramolecular gels. The nanostructures and capabilities of
photocatalytic hydrogen production of LBG/TCPP/THPP gels can be simply
modulated by gelation in different solvents. LBG/TCPP/THPP co-assemble
into fibrous nanostructures in DMF with TCPP/THPP forming a protonated
exciplex.
Beijing Key Laboratory for Science and Application of Functional Molecular and
Crystalline Materials, Department of Chemistry, University of Science and
Technology Beijing, Beijing 100083, China. E-mail: twang@ustb.edu.cn,
jianzhuang@ustb.edu.cn
† Electronic supplementary information (ESI) available: Experimental section
and additional figures and tables. See DOI: 10.1039/c9cc08060k
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was calculated to be about 50% (ESI†), which ensures the improved
collective optical properties of the systems. The protonation of
porphyrin cannot be changed when LBG/TCPP/THPP xerogels
were dispersed in water, presumably due to the strong hydropho-
bicity of the LBG gelators.
Both the TEM and SEM images of LBG/TCPP/THPP DMF gels
show fibrous nanostructures, Fig. 1c and d, which are similar to
that of pure LBG DMF gels, Fig. S7a (ESI†), suggesting that
porphyrin assemblies were included into these nanofibers. For
LBG/TCPP DMF gels, nanofibers can also be detected by TEM
and SEM measurements, Fig. S7b and c (ESI†). For LBG/THPP
DMF gels, small nanoparticles together with nanofibers were
detected, Fig. S7d and e (ESI†), indicating the possible phase
separation. Therefore, mixing TCPP and THPP with a molar ratio
of around 1/1 could induce better integration upon gelation with
LBG. Changing the molar ratio of TCPP/THPP cannot produce
more ordered nanostructures, Fig. S8 (ESI†).
Due to the poor solubility, the UV-vis spectra of TCPP in ethanol
solution show a relatively broad Soret band, Fig. S9a (ESI†). Gelation
in ethanol with LBG induced the aggregation and moderate
protonation of TCPP porphyrins, Fig. S9b (ESI†). No protonation
of porphyrins can be detected from the UV-vis spectra of THPP
ethanol solution, TCPP/THPP mixture in ethanol solution, and
LBG/THPP ethanol gels, Fig. 1e and Fig. S9 (ESI†). The protona-
tion of porphyrin can also be detected from the UV-vis spectra of
LBG/TCPP/THPP ethanol gels with a relatively weak absorption
at a longer wavelength, Fig. 1e.12d
Fig. 1 (a) UV-vis spectra of LBG/TCPP/THPP DMF gels (TCPP = 1.26 mM;
THPP = 1.47 mM) and TCPP/THPP mixture in DMF solution. (b) N 1s region
XPS of xerogels of LBG/TCPP/THPP DMF gels. N 1s region XPS for TCPP
powder. (c and d) Photographs (inset of c), TEM (c) and SEM (d) images of
LBG/TCPP/THPP DMF gels. (e) UV-vis spectra of LBG/TCPP/THPP ethanol
gels and TCPP/THPP mixture in ethanol solution. (f) Photographs (inset of f)
and TEM (f) image of LBG/TCPP/THPP ethanol gels.
Except for the TEM images of LBG/THPP ethanol gels, Fig. S10e
porphyrins occurred in a neutral environment, inset of Fig. 1a (ESI†), the TEM and SEM images of other different multi-component
and c.12 In this case, the concentration and the molar ratios of ethanol gels cannot show clear fibrous nanostructures, Fig. 1f and
TCPP/THPP play a very important role, Fig. S2 and S3 (ESI†). Fig. S10 (ESI†), suggesting the less ordered molecular packing within
Gels containing 10 mg LBG and 2 mg porphyrin (molar ratios of ethanol gels.
THPP/TCPP = 1.15/1) in 1 mL DMF produce the broadest
Parts of the carboxylic acid groups changed into carboxylate in
UV-visible absorption, Fig. 1a. In contrast, no protonation can TCPP of LBG/TCPP/THPP DMF gels, which was confirmed from
be detected from the UV-vis spectra of other DMF systems, such the FT-IR spectra, Fig. S11 (ESI†), further demonstrating that the
as TCPP/THPP mixture in DMF solution, LBG/TCPP DMF gels, proton source is TCPP. The XRD pattern of pure LBG gels shows a
LBG/THPP DMF gels, TCPP DMF solution and THPP DMF diffraction peak of 2y = 2.541 with a d spacing of 3.86 nm,
solution, Fig. 1a and Fig. S4 (ESI†). These results suggest that suggesting the tail-to-tail stacking mode13 of LBG molecules,
the protonation of porphyrins cannot happen in the solution Fig. S12 (ESI†). For the XRD patterns of LBG/TCPP/THPP assem-
state. TCPP or THPP alone also cannot protonate itself upon blies formed in DMF and ethanol, a d spacing of 3.86 and 3.71 nm
gelation in DMF.
was determined, respectively, Fig. S12 (ESI†). These results suggest
The porphyrin protonation in LBG/TCPP/THPP DMF gels was that the bilayer nanostructures of LBG assemblies were not
further confirmed by the UV-vis spectra of LBG/TCPP DMF gels and destroyed by porphyrin assemblies within the multi-component
LBG/TCPP DMF gels treated with TFA (trifluoroacetic acid), Fig. S5 supramolecular gels. This situation was demonstrated by the
(ESI†). The X-ray photoelectron spectra (XPS) of LBG/TCPP/THPP feeble cotton effects from different CD spectra, Fig. S13 (ESI†),
DMF gels suggest a molar ratio of about 5/3 between the unproto- which suggests the relatively weak interactions between por-
nated nitrogen (–CQN–) of porphyrin and the protonated nitrogen phyrin assemblies and LBG bilayers.11 Moreover, the XRD peak
(–N+),12e showing the partially protonating nature of porphyrin, at 2y = 6.31 for LBG/TCPP/THPP assemblies formed in DMF
Fig. 1b. The oxygen of phenolic hydroxy groups (Ph-OH) was clearly suggests a d value of 1.4 nm, which can be assigned to the layer
identified from the XPS signals, Fig. S6 (ESI†), which suggests that distance of porphyrin assemblies.
the phenol hydroxyl was not ionized. Therefore, the protonation of
The fluorescence of the TCPP/THPP mixture in DMF solution
porphyrins should be dependent on the carboxylic acids of TCPP. shows a broad peak with a distinct red shift compared with that of
The very close molecular packing of TCPP and THPP within gels TCPP or THPP alone in DMF solution, indicating the formation of
induces the protonation. Nevertheless, the protonation and the TCPP/THPP exciplex in DMF solution, Fig. 2a.14 This exciplex
J-aggregation of porphyrins leads to a broader UV-visible was proved by the further broadening and red shifts of fluores-
absorption. The corresponding theoretical spectral efficiency cence peaks upon increasing the concentration of the TCPP/THPP
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formed in DMF is almost six-times larger than that of the systems
obtained in ethanol, due possibly to the ordered nanostructure of
LBG/TCPP/THPP DMF gels with very broad visible light absorp-
tion, as well as the porphyrin exciplex formed in the DMF system.
These results confirm the efficient charge separation within the
LBG/TCPP/THPP DMF gels.
For the time-resolved fluorescence decay, the average transient
fluorescence lifetime of the LBG/TCPP/THPP DMF gels was calcu-
lated to be 10.44 ns, which was enhanced in comparison with that
of TCPP/THPP in DMF solution (8.23 ns), suggesting the improve-
ment of photogenerated charge separation within the gels, Fig. 2d
and Table S1 (ESI†). Due to the aggregation, TCPP molecules in
ethanol solution show very fast fluorescence decay, Fig. S16 (ESI†).
Notably, although the lifetime of LBG/TCPP/THPP ethanol gels
(10.72 ns) is similar to that of LBG/TCPP/THPP DMF gels, a
distinct change was detected when Pt nanoparticles were included
by reduction of H2PtCl6 solution upon light illumination.8c For
LBG/TCPP/THPP/Pt obtained from DMF (Fig. S17, ESI†), the
average fluorescence lifetime was found to be 1.82 ns, Fig. 3b
and Table S1 (ESI†), whereas the lifetime of LBG/TCPP/THPP/Pt
obtained in ethanol is 10.003 ns, Fig. 3b and Table S1 (ESI†).
When Pt nanoparticles as cocatalysts were included, the entire
photocatalytic hydrogen generation could be achieved. The
much shorter fluorescence lifetime suggests the more efficient
transportation of photogenerated carriers.
As for the hydrogen production photocatalyzed by LBG/
TCPP/THPP/Pt obtained from DMF gels with ascorbic acid as
the sacrificial reagent, the total amount of H2 generated under
5 h visible light irradiation was calculated to be 6.5 mmol gÀ1
porphyrin, Fig. 3c, which is about seven-times larger than that
of the LBG/TCPP/THPP/Pt system prepared in ethanol, Fig. 3d;
and 15 times larger than that of the LBG/TCPP/Pt catalyst, Fig.
S18 (ESI†). Moreover, the recycling experiments suggest good
photocatalytic properties during the 5 catalytic runs over 25
hours, demonstrating the stability of photocatalysis based on
the multi-component supramolecular gels, Fig. S19 (ESI†). The
photocatalytic H2 generation performances of LBG/TCPP/THPP
based assemblies can be comparable with those of the recently
reported supramolecular porphyrin systems, such as porphyrin
MOFs, TiO2/porphyrin assemblies, and graphene derivatives/
porphyrin assemblies, Table S2 (ESI†).
Fig. 2 (a) Fluorescence spectra of TCPP, THPP and TCPP/THPP mixture in
DMF solution. (b) Fluorescence spectra of TCPP/THPP mixture in DMF solution
at different concentrations. (c) Fluorescence spectra of LBG/TCPP/THPP DMF
gels and LBG/TCPP/THPP ethanol gels. (d) Transient fluorescence lifetime
of LBG/TCPP/THPP DMF gels and TCPP/THPP mixture in DMF solution.
(The excitation wavelength for fluorescence measurements is 420 nm, for
transient fluorescence lifetime it is 405 nm.)
mixture, Fig. 2b. The TCPP/THPP exciplex in DMF further demon-
strates the pairing of two types of porphyrins. This exciplex was
also recognized in LBG/TCPP/THPP DMF gels with the red shifts
of fluorescence peak, Fig. 2c. The porphyrin exciplex possesses a
smaller bandgap, which could benefit the photo-induced electron
generation and the charge separation. However, in the case of the
TCPP/THPP mixture in ethanol solution, no exciplex can be
detected, Fig. S14 (ESI†).
The xerogels of LBG/TCPP/THPP were put on the ITO electrode
for electrochemical studies, Fig. S15 (ESI†). Upon photoirradiation,
a prompt and reproducible transient photocurrent was detected,
Fig. 3a. Interestingly, the photocurrent intensity of the assemblies
In summary, multi-component supramolecular gels containing
two types of free base porphyrins and a L-glutamic acid derivative
were fabricated for photocatalytic applications. The nanostruc-
tures and photocatalytic properties of the systems were simply
modulated by changing the solvent for gelation. Importantly,
gelation induces porphyrin protonation and J-aggregation in a
neutral environment and subsequently expands the absorption
to a wide range of visible wavelengths with a theoretical spectral
efficiency up to 50%, suggesting very good light harvesting
properties. Upon changing the solvents, a porphyrin exciplex
with a smaller bandgap for photo-induced electron generation
was obtained. As a result, the UV-visible absorption, charge
separation, and transportation of photogenerated carriers of
the systems can be easily modulated by changing the assemblies
with different nanostructures. The present multi-component
Fig. 3 (a) Photocurrents of the xerogels of LBG/TCPP/THPP DMF gels and
LBG/TCPP/THPP ethanol gels under visible light irradiation (l 4 400 nm).
(b) Transient fluorescence lifetime of LBG/TCPP/THPP/Pt assemblies
formed in different solutions. (c) Recycling photocatalyzed H2 production
by LBG/TCPP/THPP/Pt assemblies obtained from DMF gels. (d) Recycling
photocatalyzed H2 production by LBG/TCPP/THPP/Pt assemblies based on
ethanol gels.
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2, 58–63; (e) J. Fei and J. Li, Adv. Mater., 2015, 27, 314–319; ( f ) K. Liu,
R. Xing, Y. Li, Q. Zou, H. Moehwald and X. Yan, Angew. Chem., Int.
Ed., 2016, 55, 12503–12507; (g) Z. Zhang, Y. Zhu, X. Chen, H. Zhang
and J. Wang, Adv. Mater., 2019, 31, 1806626.
7 (a) J. Tian, Z.-Y. Xu, D.-W. Zhang, H. Wang, S.-H. Xie, D.-W. Xu,
Y.-H. Ren, H. Wang, Y. Liu and Z.-T. Li, Nat. Commun., 2016,
7, 11580; (b) D. Liu, J. Wang, X. Bai, R. Zong and Y. Zhu, Adv. Mater.,
2016, 28, 7284–7290; (c) A. Krieger, J. P. Fuenzalida Werner,
G. Mariani and F. Groehn, Macromolecules, 2017, 50, 3464–3475;
(d) S. Fruehbeisser and F. Groehn, J. Am. Chem. Soc., 2012, 134,
14267–14270; (e) M. de Torres, R. van Hameren, R. J. M. Nolte,
A. E. Rowan and J. A. A. W. Elemans, Chem. Commun., 2013, 49,
10787–10789.
8 (a) N. Zhang, L. Wang, H. Wang, R. Cao, J. Wang, F. Bai and H. Fan,
Nano Lett., 2018, 18, 560–566; (b) Y. Liu, L. Wang, H. Feng, X. Ren,
J. Ji, F. Bai and H. Fan, Nano Lett., 2019, 19, 2614–2619; (c) J. Wang,
Y. Zhong, L. Wang, N. Zhang, R. Cao, K. Bian, L. Alarid,
R. E. Haddad, F. Bai and H. Fan, Nano Lett., 2016, 16, 6523–6528;
(d) D. Zhang, Y. Liu, Y. Fan, C. Yu, Y. Zheng, H. Jin, L. Fu, Y. Zhou
and D. Yan, Adv. Funct. Mater., 2016, 26, 7652–7661; (e) L. Yang,
M. Wang, P. M. Slattum, B. R. Bunes, Y. Wang, C. Wang and L. Zang,
ACS Appl. Mater. Interfaces, 2018, 10, 19764–19772; ( f ) H. Zhao,
D. Zhang, P. Du, H. Li, C. Liu, Y. Li, H. Cao, J. C. Crittenden and
Q. Huang, J. Hazard. Mater., 2015, 297, 269–277; (g) P. Du, H. Zhao,
C. Liu, Q. Huang and H. Cao, Water Res., 2016, 106, 488–495.
9 (a) C. D. Jones, H. T. D. Simmons, K. E. Horner, K. Liu,
R. L. Thompson and J. W. Steed, Nat. Chem., 2019, 11, 375–381;
(b) Y. Wang, S. Oldenhof, F. Versluis, M. Shah, K. Zhang, V. van
Steijn, X. Guo, R. Eelkema and J. H. van Esch, Small, 2019,
15, 1804154; (c) G. Yu, X. Yan, C. Han and F. Huang, Chem. Soc.
Rev., 2013, 42, 6697–6722; (d) Z. Shen, Y. Jiang, T. Wang and M. Liu,
J. Am. Chem. Soc., 2015, 137, 16109–16115; (e) Z. Shen, Y. Sang,
T. Wang, J. Jiang, Y. Meng, Y. Jiang, K. Okuro, T. Aida and M. Liu,
Nat. Commun., 2019, 10, 1–8.
10 (a) L. E. Buerkle and S. J. Rowan, Chem. Soc. Rev., 2012, 41,
6089–6102; (b) W. Edwards and D. K. Smith, J. Am. Chem. Soc.,
2014, 136, 1116–1124; (c) J. Ruiz-Olles and D. K. Smith, Chem. Sci.,
2018, 9, 5541–5550.
11 (a) Y. Li, T. Wang and M. Liu, Soft Matter, 2007, 3, 1312–1317;
(b) P. Duan, H. Cao, L. Zhang and M. Liu, Soft Matter, 2014, 10,
5428–5448; (c) P. Duan, Y. Li, J. Jiang, T. Wang and M. Liu, Sci.
China: Chem., 2011, 54, 1051–1063.
12 (a) X. Li, Z. Zheng, M. Han, Z. Chen and G. Zou, J. Phys. Chem. B,
2007, 111, 4342–4348; (b) G. Dyrda, R. Slota, M. A. Broda and
G. Mele, Res. Chem. Intermed., 2016, 42, 3789–3804; (c) G. De Luca,
A. Romeo and L. M. Scolaro, J. Phys. Chem. B, 2006, 110, 14135–14141;
(d) M. Zannotti, R. Giovannetti, B. Minofar, D. Reha, L. Plackova,
C. A. D’Amato, E. Rommozzi, H. V. Dudko, N. Kari and M. Minicucci,
Spectrochim. Acta, Part A, 2018, 193, 235–248; (e) J. R. Eskelsen,
Y. Wang, Y. Qui, M. Ray, M. Handlin, K. W. Hipps and U. Mazur,
J. Porphyrins Phthalocyanines, 2012, 16, 1233–1243; ( f ) Y. Zhao, X. Cai,
Y. Zhang, C. Chen, J. Wang and R. Pei, Nanoscale, 2019, 11,
12250–12258.
supramolecular gels represent a new approach for the fabrica-
tion of photocatalytic systems.
The authors gratefully acknowledge support for this work
from the Natural Science Foundation of China (no. 21631003,
21471015, 21671017, 21474118 and 21773006), Major Science
and Technology Program for Water Pollution Control and
Treatment (2017ZX07402001), Beijing Municipal Commission
of Education, and University of Science and Technology Beijing.
Conflicts of interest
There are no conflicts to declare.
Notes and references
1 (a) S. Caffarri, T. Tibiletti, R. C. Jennings and S. Santabarbara, Curr.
Protein Pept. Sci., 2014, 15, 296–331; (b) Y. Mazor, A. Borovikova,
I. Caspy and N. Nelson, Nat. Plants, 2017, 3, 17014; (c) H. Toporik,
I. Carmeli, I. Volotsenko, M. Molotskii, Y. Rosenwaks, C. Carmeli
and N. Nelson, Adv. Mater., 2012, 24, 2988–2991, S2988/2981-S2988/
2915.
2 (a) R. Croce and H. van Amerongen, Nat. Chem. Biol., 2014, 10,
492–501; (b) H. Hashimoto, Y. Sugai, C. Uragami, A. T. Gardiner and
R. J. Cogdell, J. Photochem. Photobiol., C, 2015, 25, 46–70; (c) S. K.
Ravi, V. S. Udayagiri, L. Suresh and S. C. Tan, Adv. Funct. Mater.,
2018, 28, 1705305.
3 (a) T. Brixner, R. Hildner, J. Koehler, C. Lambert and F. Wuerthner,
Adv. Energy Mater., 2017, 7, 1700236; (b) J. Neugebauer, J. Phys.
Chem. B, 2008, 112, 2207–2217; (c) X.-L. Zeng, K. Tang, N. Zhou,
M. Zhou, H. J. M. Hou, H. Scheer, K.-H. Zhao and D. Noy, J. Am.
Chem. Soc., 2013, 135, 13479–13487.
4 (a) R. V. Kazantsev, A. J. Dannenhoffer, A. S. Weingarten, B. T.
Phelan, B. Harutyunyan, T. Aytun, A. Narayanan, D. J. Fairfield,
J. Boekhoven, H. Sai, A. Senesi, P. I. O’Dogherty, L. C. Palmer,
M. J. Bedzyk, M. R. Wasielewski and S. I. Stupp, J. Am. Chem. Soc.,
2017, 139, 6120–6127; (b) A. S. Weingarten, R. V. Kazantsev,
L. C. Palmer, M. McClendon, A. R. Koltonow, A. P. S. Samuel,
D. J. Kiebala, M. R. Wasielewski and S. I. Stupp, Nat. Chem., 2014,
6, 964–970; (c) A. S. Weingarten, R. V. Kazantsev, L. C. Palmer,
D. J. Fairfield, A. R. Koltonow and S. I. Stupp, J. Am. Chem. Soc., 2015,
137, 15241–15246; (d) C. Felip-Leon, F. Guzzetta, B. Julian-Lopez,
F. Galindo and J. F. Miravet, J. Phys. Chem. C, 2017, 121,
21154–21159; (e) B. Maiti, A. Abramov, R. Perez-Ruiz and D. Diaz
Diaz, Acc. Chem. Res., 2019, 52, 1865–1876; ( f ) K. Kong, S. Zhang,
Y. Chu, Y. Hu, F. Yu, H. Ye, H. Ding and J. Hua, Chem. Commun.,
2019, 55, 8090–8093.
5 (a) B. Yuan, H. Yang, Z. Wang and X. Zhang, Langmuir, 2014, 30,
15462–15467; (b) C. Zhang, P. Chen, H. Dong, Y. Zhen, M. Liu and
W. Hu, Adv. Mater., 2015, 27, 5379–5387; (c) P. Guo, P. Chen and
M. Liu, ACS Appl. Mater. Interfaces, 2013, 5, 5336–5345; (d) G. Geng,
Z. Wang, P. Chen, B. Guan, C. Yang and M. Liu, Phys. Chem. Chem.
Phys., 2018, 20, 8488–8497; (e) J. Kwak, M.-C. Kim and S.-Y. Lee,
Nanoscale, 2016, 8, 15064–15070; ( f ) C. Zhou, X. Feng, R. Wang,
G. Yang, T. Wang and J. Jiang, ACS Omega, 2018, 3, 10638–10646.
6 (a) B. Sun, K. Tao, Y. Jia, X. Yan, Q. Zou, E. Gazit and J. Li, Chem. Soc.
Rev., 2019, 48, 4387–4400; (b) J. Han, K. Liu, R. Chang, L. Zhao and
X. Yan, Angew. Chem., Int. Ed., 2019, 58, 2000–2004; (c) Q. Zou,
K. Liu, M. Abbas and X. Yan, Adv. Mater., 2016, 28, 1031–1043;
(d) K. Liu, M. Abass, Q. Zou and X. Yan, Green Energy Environ., 2017,
13 (a) Y. Li, P. Duan and M. Liu, Chem. – Eur. J., 2017, 23, 8225–8231;
(b) X. Wang, F. Xie, P. Duan and M. Liu, Langmuir, 2016, 32,
12534–12541.
14 (a) F. Abou-Chahine, D. Fujii, H. Imahori, H. Nakano, N. V. Tkachenko,
Y. Matano and H. Lemmetyinen, J. Phys. Chem. B, 2015, 119,
7328–7337; (b) A. H. Al-Subi, M. Niemi, N. V. Tkachenko and
H. Lemmetyinen, J. Phys. Chem. A, 2012, 116, 9653–9661;
(c) T. Umeyama, J. Mihara, H. Hayashi, N. Kadota, V. Chukharev,
N. V. Tkachenko, H. Lemmtyinen, K. Yoshida, S. Isoda and
H. Imahori, Chem. Commun., 2011, 47, 11781–11783.
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