Double-Layered Plasmonic–Magnetic Vesicles by Self-Assembly of Janus Amphiphilic Gold–Iron(II,III) Oxide Nanoparticles

Article abstract of DOI:10.1002/anie.201702572

Janus nanoparticles (JNPs) offer unique features, including the precisely controlled distribution of compositions, surface charges, dipole moments, modular and combined functionalities, which enable excellent applications that are unavailable to their symmetrical counterparts. Assemblies of NPs exhibit coupled optical, electronic and magnetic properties that are different from single NPs. Herein, we report a new class of double-layered plasmonic–magnetic vesicle assembled from Janus amphiphilic Au-Fe₃O₄ NPs grafted with polymer brushes of different hydrophilicity on Au and Fe₃O₄ surfaces separately. Like liposomes, the vesicle shell is composed of two layers of Au-Fe₃O₄ NPs in opposite direction, and the orientation of Au or Fe₃O₄ in the shell can be well controlled by exploiting the amphiphilic property of the two types of polymers.

Full text of DOI:10.1002/anie.201702572

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
Chemie
International Edition
www.angewandte.org
Accepted Article
Title: Double-Layered Plasmonic-Magnetic Vesicles by Self-Assembly
of Janus Amphiphilic Au-Fe3O4 Nanoparticles
Authors: Jibin Song, Binghui Wu, Zijian Zhou, Guizhi Zhu, Yijing Liu,
Zhen Yang, Lisen Lin, Guocan Yu, Fuwu Zhang, Guofeng
Zhang, Hongwei Duan, Galen Stucky, and Xiaoyuan Chen
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201702572
Angew. Chem. 10.1002/ange.201702572
Link to VoR: http://dx.doi.org/10.1002/anie.201702572
http://dx.doi.org/10.1002/ange.201702572

10.1002/anie.201702572
Angewandte Chemie International Edition
COMMUNICATION
Self-Assembled Materials
Double-Layered Plasmonic-Magnetic Vesicles by Self-Assembly
of Janus Amphiphilic Au–Fe3O4 Nanoparticles
Jibin Song, Binghui Wu, Zijian Zhou, Guizhi Zhu, Yijing Liu, Zhen Yang, Lisen Lin, Guocan Yu, Fuwu Zhang,
Guofeng Zhang, Hongwei Duan,* Galen D. Stucky,* Xiaoyuan Chen*
Abstract: Janus nanoparticles (JNPs) offer unique features, including
precisely controlled distribution of compositions, surface charges, dipole
moments, modular and combined functionalities, which enable excellent
applications that are unavailable to their symmetrical counterparts.
Assemblies of NPs exhibit coupled optical, electronic and magnetic
properties that are different from single NPs. Herein, we report a new class
of double-layered plasmonic-magnetic vesicle assembled from Janus
amphiphilic Au-Fe3O4 NPs grafted with polymer brushes of different
hydrophilicity on Au and Fe3O4 surfaces separately. Like liposomes, the
vesicle shell is composed of two layers of Au-Fe3O4 NPs in opposite
direction, and the orientation of Au or Fe3O4 in the shell can be well
controlled by exploiting the amphiphilic property of the two types of
polymers. Owing to the interparticle plasmonic coupling between Au NPs
and magnetic dipole interaction of Fe3O4 NPs, the double-layered vesicles
exhibited significantly enhanced surface-enhanced Raman scattering
(SERS), photoacoustic and magnetic properties compared with those of
single JNPs. Furthermore, the results of in vivo imaging suggest that these
double-layered vesicles are suitable agents for dual photoacoustic and
magnetic resonance imaging with high resolution.
distribution of surface grafted molecules, hydrophilicity and
hydrophobicity, dipole moments, which offer diverse applications that
are not available to their symmetrical counterparts.[3a, b, 4]
Most recently, there has been a growing interest in the construction
of nanometer-sized assemblies of inorganic NPs because of their
unique and enhanced optical and electronic properties that originate
from the interaction or coupling of individual NPs.[4b, 5] As de Gennes
pointed out, the Janus feature often leads surfactant-like structures for
JNPs, exhibiting intriguing assembly behaviors and properties.[1-2]
According to computer simulation results, JNPs can form complex
structures unavailable to homo NPs.[6] Although a series of JNPs have
been prepared or functionalized, their assembly behavior and
mechanism have rarely been investigated.[7] Even the experimental
works on the self-assembly of small JNPs (< 20 nm in diameters) are
scarcely reported. So far, research on the self-assembly of JNPs are
mainly focused on mono-component NPs of biphasic geometry with
distinct surface functionalities, such as JNPs with bicompartment small
molecules or DNAs on two sides.[8] Limited reports are available on
the preparation of JNPs with both biphasic core compositions and
Janus distribution of surface coatings, and investigation of their self-
assembly properties.
Janus nanoparticles (JNPs) are a special class of anisotropic NPs
exhibiting biphasic geometry of core compositions or distinct surface
modifications, as presented by de Gennes in his Nobel lecture in
1991.[1] JNPs with diverse potential applications in surface property
control, self-assembly, optical and electronic device, have gained
increasing interests in the field of chemistry, physics, materials science,
and biology.[2] Recently, a variety of JNPs have been developed
including organic NPs (such as block copolymer micelles, dendrimers,
and nanofibers), inorganic NPs (such as dumbbell-, acorn-, or
raspberry-like clusters), and hybrid NPs with bicompartment grafted
small molecules, polymer brushes or surfactants.[3] More interestingly,
Janus metal or inorganic NPs exhibit unique features, such as
functional compositions, modular functionalities, precisely controlled
[*]
Dr. J. Song,+ Dr. Z. Zhou, Dr. G. Zhu, Dr. Y, Liu, Mr. Z.Yang, Dr. L. Lin,
Dr. G. Yu, Dr. F. Zhang, Dr. G. Zhang, Dr. X. Chen
Laboratory of Molecular Imaging and Nanomedicine, National Institute of
Biomedical Imaging and Bioengineering, National Institutes of Health,
Bethesda, MD 20892, USA
Figure 1. Schematic illustration of the Janus Au-Fe3O4 NPs grafted with
hydrophilic polyethylene glycol (PEG) on Au and hydrophobic polystyrene
(PS) on Fe3O4 (a), with PS on Au and PEG on Fe3O4 (b), and with binary
mixed PEG and PS (c), and the hierarchical self-assembly of the resulting
three kinds of Janus amphiphilic nanoparticles into double-layered
plasmonic-magnetic vesicle 1 (d) and 2 (e) and mono-layered vesicle 3 (f)
in aqueous media.
Email: shawn.chen@nih.gov
Dr. B. Wu,+ Dr. G. Stucky
Department of Chemistry & Biochemistry, University of California, Santa
Barbara, California 93106, USA
Collaborative Innovation Center of Chemistry for Energy Materials, Xiame
n University, Xiamen 361005, China
Email: stucky@chem.uscb.edu
Dr. H. Duan
School of Chemical and Biomedical Engineering, Nanyang Technological
University, 70 Nanyang Drive, Singapore 637457
Email: hduan@btu.edu.sg
Herein, we report a new model of “bundled amphiphilic block
copolymer brushes” for the self-assembly of Janus Au-Fe3O4 NPs,
coated with Janus amphiphilic distribution of hydrophilic and
hydrophobic polymer brushes on Au and Fe3O4 surface, respectively
(in Figures 1a, b). Janus Au-Fe3O4 NPs, containing amphiphilic
distribution of hydrophilic and hydrophobic polymer grafts, were
prepared by exploiting the different surface binding abilities of Au and
[+] Drs. J. Song and B. Wu contributed equally to this work.
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/anie.201xxxxxx
This article is protected by copyright. All rights reserved.

10.1002/anie.201702572
Angewandte Chemie International Edition
COMMUNICATION
Fe3O4 to thiolated and phosphonated groups, resulting in so-called
Janus amphiphilic particles. As an exemplary system, we used
amphiphilic Janus Au-Fe3O4 NPs, whose self-assembly allows exact
control on positioning and direction of JNPs. We considered the JNPs
as amphiphiles, resembling “A-B” diblock copolymer “bundled
brushes”, and used the assembling ability of block copolymers to
mixture of PEG-SH and PS-P to Au-Fe3O4 NPs (Figure 1a). The type
2 Janus NPs, with PS grafting on Au and PEG on Fe3O4 (Au@PS-
Fe3O4@PEG), were prepared by adding a mixture of PEG-P and PS-
1
SH to JNPs (Figure 1c). The H NMR results (Figure S3) and high
weight fraction of the polymer brushes coated on Janus NPs (over 35%)
(Figure S4) confirmed the successful preparation of the amphiphilic
NPS. This strategy demonstrates a particularly effective procedure for
chemically coating amphiphilic distinct polymers on Au and Fe3O4
surfaces, to give tunable structural parameters (graft density, molecular
weight, etc.) and well-controlled physicochemical properties
organize in
a
kinetically and thermodynamically controlled
nanostructures due to the Janus segregation of the constituent
amphiphilic blocks. Interestingly, two kinds of double layered
plasmonic-magnetic vesicles, with Au or Fe3O4 localized dominantly
on the outer or interior surface of the vesicular shell, were formed by
changing the amphiphilic property of the polymer bushes on the Au or
Fe3O4 surface (Figures 1d, e). In the double-layered vesicles (DL-Ve),
the Au and Fe3O4 not only imparted their intriguing physical properties
to the assembly but also led to enhanced physical properties (SERS,
optical, photoacoustic and magnetic activities) compared with those in
discrete units. We attribute this to the interaction and coupling of the
individual JNPs. More importantly, the vesicles with enhanced optical
and magnetic properties were served as dual functional probes for in
vivo dual photoacoustic and magnetic resonance (MR) imaging with
high resolution and accuracy.
Figure 2. (a) TEM images of the Janus Au-Fe3O4 NP. (b) UV-vis
spectra of Au NP and Janus Au-Fe3O4 NP in chloroform.
The Janus bifunctional composite 6.5-6.0 nm Au-Fe3O4 NPs,
containing Au and Fe3O4 NPs, respectively, were firstly synthesized by
a microwave heating approach (Figure 2 and S1, see supporting
information (SI) for the synthetic procedure).[9] The plasmon
absorption peak of Au NP at ~533 nm in the Janus Au-Fe3O4 NPs
showed a 16 nm red-shift compared with the Au NP prior to coating
Fe3O4 NP at 517 nm. The red-shift was caused by the charge variation
of the Au while conjugating with Fe3O4, confirming the successful
preparation of the JNPs.[10] The lattice fringes of Au have a spacing of
0.240 nm which corresponds to the (111) interplanar distance of face
centered cubic (fcc) Au; the distance between two adjacent planes in
Fe3O4 is 0.484 nm, resulting from a group of (111) planes in the
inverse spinel structured Fe3O4. The (111) interplanar distance in Fe3O4
is almost twice of that in Au with a very small lattice mismatch (<1%),
indicating that the Fe3O4 NPs are epitaxially overgrown on Au NPs due
to their lattice matching.[10-11] The presence of Au and Fe3O4 surfaces
facilitates the modification of different chemical functionalities.[12] Au
and Fe3O4 show good conjugating ability specifically with thiolated
and phosphonated molecules, respectively. Thus, thiolated
polyethylene glycol (PEG-SH) and polystyrene (PS-SH), and
phosphonated PEG (PEG-P) and PS (PS-P), were synthesized, where
PEG (MW=2 kDa) and PS (MW=26 kDa) (Figure S2) are hydrophilic
and hydrophobic polymers, respectively (Scheme S1, S2, and SI for
the synthesis procedures). Two types of amphiphilic Janus Au-Fe3O4
NPs, coated with bicompartment polymer brushes with opposite
amphiphilic property on Au and Fe3O4 surface were synthesized using
ligand exchange method, respectively, as depicted in Figure 1a, b.
Specifically, the type 1 Janus NPs, with PEG coating on Au and PS
coating on Fe3O4 (Au@PEG-Fe3O4@PS) were prepared by adding a
Figure 3. TEM, SEM images, and TEM-element mapping images of
the DL-Ve 1 (a, b), DL-Ve 2 (c, d), and ML-Ve 3(e, f).
Since the amphiphilic polymer brushes densely covered the JNPs’
surface, the obtained Au@PEG-Fe3O4@PS or Au@PS-Fe3O4@PEG
looked like
a “bundle” of conventional amphiphilic diblock
copolymers. We expected that the amphiphilic JNPs would show
excellent self-assembly property in aqueous solution, thus leading to
directed self-assembly of the NPs of diverse morphologies. The self-
assembly process was initiated by adding a mixture of tetrahydrofuran
and water to a solution of amphiphilic JNPs in a mixed organic solvent
of DMF and THF. The assembled nanostructures were purified by
centrifugation to remove the free JNPs. We first investigated the self-
assembly property of type 1 Au@PEG-Fe3O4@PS, where Au@PEG
and Fe3O4@PS serve as the hydrophilic and hydrophobic blocks,
respectively. Figure 3a and S5, S6 illustrates the Transmission
Electron Microscopy (TEM) images of the resultant vesicles, revealing
a hollow structure with different contrast between the shell and interior.
More interestingly, we found that the vesicular shell was composed of
two layers of Au-Fe3O4 NPs with Au extended dominantly to the
outside of the shell and Fe3O4 localized mostly face to face inside the
This article is protected by copyright. All rights reserved.

10.1002/anie.201702572
Angewandte Chemie International Edition
COMMUNICATION
shell, named double-layered vesicle 1 (DL-Ve 1) (Figure. 1d and 3a).
From element mapping images of DL-Ve-1, Au elements were
localized outside of DL-Ve 1 shell (Figure 3b).We measured the shell
thickness of the disrupted vesicle, caused by the high vacuum pressure
while obtaining SEM images, as ~28 nm (Figure. 3a), comparable
with the total size of two JNPs. Furthermore, the type 2 Au@PS-
Fe3O4@PEG NPs (Fig. 1b) also formed uniform double layered vesicle
using the same method (Figure 3c, S6), named double-layered vesicle
2 (DL-Ve 2). As displayed in Figure 3c, Fe elements were placed
outside of DL-Ve 2 shell, confirming the Fe3O4 NPs were localized
mostly outside the vesicular shell, which is opposite to the DL-Ve 1. In
TEM images, the DL-Ve 2 exhibited a lower contrast compared with
DL-Ve 1, due to the surface of DL-Ve 2 was coated with Fe3O4 NP
with low electron density. For DL-Ve-2, Fe3O4@PEG served as the
hydrophilic part, assisting the vesicle to disperse in water. The average
size of the DL-Ve1 and 2 is ~110 and ~115 nm, respectively (Figure
S7).
the other two vesicles (Figure 3b) to the more closely spaced two
layers of Au NPs in the vesicular shell.
Owing to their strong photoacoustic (PA) property, gold
nanocrystal assemblies that have a high optical absorption coefficient
have been used as optical agents in the biomedical imaging field.[16]
Figure 4c shows the PA images of the double-layered and mono-
layered vesicles at the same optical density (OD) value at 750 nm when
illuminated with 750 nm laser. The PA amplitude of DL-Ve 2 was 2.2
and 5 times higher than the PA amplitudes of DL-Ve 1 and ML-Ve 3,
respectively, at the same OD785 (Figure 4d), which is consistent with
the results of SPR red-shift and SERS enhancement.
The amphiphilic Janus distribution of the polymer brushes on the
Au-Fe3O4 NP surface determines the unique double layered
nanostructure of the vesicles as well as the position of the Au and
Fe3O4 in the vesicular shell. As an example, we find that the Au@PS-
Fe3O4@PEG NPs formed dimers to short chains (Figure S8) with Au
face to face with increasing initial concentration of the JNP during self-
assembly. The driving force for the orientation of the JNP is the
hydrophobic-hydrophobic interaction of the attached PS on Au surface
when add water into the organic solution of JNP. To further verify the
assumptions, we prepared Au-Fe3O4 NPs coated with mixed PEG and
PS on both Au and Fe3O4 surfaces (type 3: Au-Fe3O4@PEG/PS) as a
control sample (Fig. 1e). It was self-assembled into mono-layered
vesicles, monolayered vesicle 3 (ML-Ve 3), whereas Au and Fe3O4
were randomly paralleled inside the vesicular shell, as shown in Figure
1f, 3e and Figure S6, S9. From element mapping image, Au and Fe
elements were mixed together in the ML-Ve 3 shell (Figure 3f).
Furthermore, when the MW of PS was decreased to 15 kDa (Figure
S2), the obtained Au@PEG-Fe3O4@PS (Figure S10) or Au@PS-
Fe3O4@PEG formed micelles, not vesicles (Figure S11). The Au and
Fe3O4 were located at the outer interface of the micelles formed by the
first and second NPs, respectively, since both of them coated with PEG
as hydrophilic part. We ascribed this to the reduced volume of the
hydrophobic part due to using PS of lower MW; micelles are a more
stable morphology to minimize the overall free energy of the system.[13]
The surface plasmon resonance (SPR) of gold nanocrystals is
extremely sensitive to interparticle distances.[14] In comparison with the
SPR band of Au-Fe3O4 NP in the visible region, the SPR band for both
DL-Ve 1 and 2 was broadened and red-shifted to the near-infrared
(NIR) region, owing to interparticle plasmonic coupling between the
Au NPs in the vesicular shell. The DL-Ve 2 exhibited a greater red
shift than that of the DL-Ve 1, because the Au NPs were directed face-
to-face and had shorter interparticle distance in the DL-Ve 2. For the
single vesicle, scattering spectra obtained using the dark-field imaging
microscopy (Figure S12), revealed greater red shift for the DL-Ve 2
than that of DL-Ve 1, which is consistent with the absorption spectra of
the samples in aqueous solution.
Figure 4. (a) UV−vis spectra, (b) SERS spectra, (c) photoacoustic (PA)
images, (d) PA amplitude, (e) T2-weighted MR images and (f)
corresponding r2 values of the DL-Ve 1 and 2, and ML-Ve 3 and Janus
NPs.
Magnetic resonance imaging (MRI) is a powerful, non-invasive
widely applied in clinical diagnostics.[17] To improve resolution and
quality of MR image, special endeavor has been made to improve the
T2 contrast efficiency (r2).[17-18] Among them, introducing assemblies of
magnetic nanoparticles is probably the most effective yet intriguing
approach for enhancing the r2, which increases with decreasing
interparticle distance.[19] In our experiment, we found that the DL-Ve
exhibited greatly enhanced r2 activity compared with that of single
JNPs (Figure 4e, f). The r2 values of the DL-Ve 1 (405±12.4 mM-1s-1)
and DL-Ve 2 (295±7.2 mM-1s-1) are about 7 and 5 times greater than
that of single JNP (56±4.2 mM-1s-1), due to the strong magnetic dipole
interaction of the Fe3O4 NPs in the vesicular shell. We attribute the
better r2 activity of the DL-Ve 1 compared to that of DL-Ve 2 and ML-
Ve 3 (193±6.6 mM-1s-1) to two layers of Fe3O4 positioned face-to-face
with shorter interparticle distance in the vesicle shell of DL-Ve 1.
Surface enhanced Raman scattering (SERS) of the Raman dye
attached on gold nanocrystal surface can be enhanced by the
interparticle plasmonic coupling between gold nanocrystals upon
15]
clustering.[14b,
We introduced thiolated Rhodamine (RhB-SH,
Scheme S3) on the Au surface through Au-S bond to test the Raman
scattering enhancement of the double layered vesicle. The SERS
enhancement factor of the DL-Ve 2 is 2.5ⅹ107, which is higher than
that of the DL-Ve 1 (3.8ⅹ106) and ML-Ve 3 (5.8ⅹ105). We attributed
the better SERS activity of the A DL-Ve 2 compared to the activities of
This article is protected by copyright. All rights reserved.

10.1002/anie.201702572
Angewandte Chemie International Edition
COMMUNICATION
Keywords: Amphiphilic polymer • Self-assembly • Vesicle • Janus
nanoparticle • Imaging
[1] P. G. de Gennes, Rev. Mod. Phys. 1992, 64, 645-648.
[2] a) A. Walther, A. H. E. Müller, Chem. Rev. 2013, 113, 5194-5261; b) B. Wang,
B. Li, B. Zhao, C. Y. Li, J. Am. Chem. Soc. 2008, 130, 11594-11595; c) L. C.
Bradley, K. J. Stebe, D. Lee, J. Am. Chem. Soc. 2016, 138, 11437-11440.
[3] a) F. Liang, K. Shen, X. Qu, C. Zhang, Q. Wang, J. Li, J. Liu, Z. Yang, Ang.
Chem. Int. Ed. 2011, 50, 2379-2382; b) F. Wurm, A. F. M. Kilbinger, Ang.
Chem. Int. Ed. 2009, 48, 8412-8421; c) B. Wang, B. Li, B. Dong, B. Zhao, C. Y.
Li, Macromolecules 2010, 43, 9234-9238; d) J.-K. Kim, E. Lee, Z. Huang, M.
Lee, J. Am. Chem. Soc. 2006, 128, 14022-14023.
Figure 5. In vivo (a) photoacoustic images and (b) T2-weighted MR
images of tumor before and after injection of the double layered vesicle
2, the yellow circles indicate the tumor sites.
Since the vesicles showed strong optical absorption in the NIR
region and enhanced magnetic properties, and are stable under
physiological conditions (Figure S13) and safe for bioapplication
(Figure S14), we employed the DL-Ve 2 as dual PA and MRI agents
in order to determine the accumulation of vesicles in the tumor region
after injecting the vesicle (200 µL, 500 µg Au-Fe3O4/mL) in PBS
intravenously. The continuous enhancement of the PA signals (Figure
5a) and intensities (Figure S15) over time in the tumor region
confirmed the accumulation and distribution of the vesicle in the tumor.
Using high resolution 3D PA images (Figure S16) of the tumor, we
obtained extensive information about the tumor, such as position, size
and morphology. Consistent with the PA imaging findings, as shown in
the T2-weighted MR images (Figure 5b) and T2 contrast intensity
(Figure S17), we observed an obvious darkening effect at the tumor
site after the vesicles were administered, which is a beneficial
consequence of the high r2 value of the vesicle. The dual PA and MR
imaging with the double-layered vesicles are able to provide rich
information of tumor and also guide the cancer therapy, such as
photothermal and photodynamic treatment, showing advantages than
singe gold nanorod and iron oxide nanoparticle (Figure S18). Taken
together with the SERS activity and high tumor accumulation
efficiency (Figure S19) of the double-layered vesicles, the results
demonstrated the great potential of the vesicles, formed by the self-
assembly of JNPs, as multifunctional contrast agents and probes for
future biomedical applications.[20]
In summary, we prepared two kinds of amphiphilic Janus Au@PS-
Fe3O4@PEG and Au@PEG-Fe3O4@PS NPs via a highly efficient, easy
procedure. Due to the amphiphilic Janus distribution of the polymer
grafts on the Janus Au-Fe3O4 surface, double-layered plasmonic-
magnetic vesicles were formed mimicking the nature of classical
amphiphilic “bundled block polymers”. The positions of the Au and
Fe3O4 in the vesicular shell could easily be reversed by changing the
amphiphilic property of the polymer brushes coated on their surface.
Benefitting from the interparticle plasmonic coupling of the Au NPs
and magnetic diploe interaction of the Fe3O4 localized in the doubled
vesicular shell, the vesicles exhibited greatly enhanced optical and
magnetic properties. They demonstrated the potential to be used as a
dual optical and MR imaging agent in vivo. Given current advances in
the synthesis of functional copolymers and inorganic nanoparticles, the
proposed strategy may open up a new avenue for the controlled
preparation of novel Janus colloidal building blocks with adjustable
surface coating for the fabrication of new functional materials and
devices.
[4] a) S. X. Xing, Y. H. Feng, Y. Y. Tay, T. Chen, J. Xu, M. Pan, J. T. He, H. H.
Hng, Q. Y. Yan, H. Y. Chen, J. Am. Chem. Soc. 2010, 132, 9537-9539; b) J. van
Herrikhuyzen, G. Portale, J. C. Gielen, P. C. M. Christianen, N. A. J. M.
Sommerdijk, S. C. J. Meskers, A. P. H. J. Schenning, Chem. Commun. 2008,
697-699.
[5] a) S. Mallidi, T. Larson, J. Tam, P. P. Joshi, A. Karpiouk, K. Sokolov, S.
Emelianov, Nano Lett. 2009, 9, 2825-2831; b) N. J. Halas, S. Lal, W.-S. Chang,
S. Link, P. Nordlander, Chem. Rev. 2011, 111, 3913–3961; c) Z. H. Nie, D. Fava,
E. Kumacheva, S. Zou, G. C. Walker, M. Rubinstein, Nat. Mater. 2007, 6, 609-
614; d) J. Hu, T. Wu, G. Zhang, S. Liu, J. Am. Chem. Soc. 2012, 134, 7624-7627.
[6] a) F. Sciortino, A. Giacometti, G. Pastore, Phys. Rev. Lett. 2009, 103, 237801; b)
S. C. Glotzer, Science 2004, 306, 419-420; c) S. C. Glotzer, M. J. Solomon, Nat.
Mater. 2007, 6, 557-562.
[7] L. Hong, A. Cacciuto, E. Luijten, S. Granick, Langmuir 2008, 24, 621-625.
[8] L. H. Tan, H. Xing, H. Chen, Y. Lu, J. Am. Chem. Soc. 2013, 135, 17675-17678.
[9] B. Wu, S. Tang, M. Chen, N. Zheng, Chem. Commun. 2014, 50, 174-176.
[10] H. Yu, M. Chen, P. M. Rice, S. X. Wang, R. L. White, S. Sun, Nano Lett. 2005,
5, 379-382.
[11] B. Wu, H. Zhang, C. Chen, S. Lin, N. Zheng, Nano Res. 2009, 2, 975-983.
[12] C. Xu, J. Xie, D. Ho, C. Wang, N. Kohler, E. G. Walsh, J. R. Morgan, Y. E.
Chin, S. Sun, Ang. Chem. Int. Ed. 2008, 47, 173-176.
[13] a) C. Yi, S. Zhang, K. T. Webb, Z. Nie, Acc. Chem. Res. 2017, 50, 12-21; b) R.
Shenhar, T. B. Norsten, V. M. Rotello, Adv. Mater. 2005, 17, 657-669.
[14] a) A. Klinkova, R. M. Choueiri, E. Kumacheva, Chem. Soc. Rev. 2014, 43,
3976-3991; b) A. Kumar, S. Kim, J.-M. Nam, J. Am. Chem. Soc. 2016, 138,
14509-14525.
[15] a) M. J. Banholzer, J. E. Millstone, L. Qin, C. A. Mirkin, Chem. Soc. Rev. 2008,
37, 885-897; b) R. A. Alvarez-Puebla, L. M. Liz-Marzán, Small 2010, 6, 604-
610.
[16] L. Nie, X. Chen, Chem. Soc. Rev. 2014, 43, 7132-7170.
[17] D. Ling, N. Lee, T. Hyeon, Acc. Chem. Res. 2015, 48, 1276-1285.
[18] N. Lee, T. Hyeon, Chem. Soc. Rev. 2012, 41, 2575-2589.
[19] a) Y. Matsumoto, A. Jasanoff, Mag. Reson. Imaging 2008, 26, 994-998; b) D.
Wang, B. Lin, T. Shen, J. Wu, C. Xia, B. Song, H. Ai, Sci. Bull. 2016, 61, 1023-
1030.
[20] L. Vigderman, E. R. Zubarev, Adv. Drug Deliv. Rev. 2013, 65, 663-676.
Acknowledgements
This work was supported by the Intramural Research Program of the
National Institute of Biomedical Imaging and Bioengineering (NIBIB),
National Institutes of Health (NIH).
This article is protected by copyright. All rights reserved.

10.1002/anie.201702572
Angewandte Chemie International Edition
COMMUNICATION
Entry for the Table of Contents
COMMUNICATION
Double-layered plasmonic-
magnetic vesicles were
prepared by self-assembly of
Janus Au-Fe3O4 NPs grafted
with amphiphilic polymer
brushes of different
J. Song, B. Wu, Z. Zhou, G.
Zhu, Y. Liu, Z. Yang, L. Lin, G.
Yu, F. Zhang, G. Zhang, H.
Duan,* G. Stucky,* X. Chen*
Page No. – Page No.
hydrophilicity on Au and
Fe3O4 surfaces separately.
Double-Layered Plasmonic-
Magnetic Vesicles by Self-
Assembly of Janus
Amphiphilic Au–Fe3O4
Nanoparticles
This article is protected by copyright. All rights reserved.