Binary and Ternary Superlattices Self-Assembled from Colloidal Nanodisks and Nanorods

Article abstract of DOI:10.1021/jacs.5b03234

Self-assembly of multicomponent anisotropic nanocrystals with controlled orientation and spatial distribution allows the design of novel metamaterials with unique shape- and orientation-dependent collective properties. Although many phases of binary structures are theoretically proposed, the examples of multicomponent assemblies, which are experimentally realized with colloidal anisotropic nanocrystals, are still limited. In this report, we demonstrate the formation of binary and ternary superlattices from colloidal two-dimensional LaF₃ nanodisks and one-dimensional CdSe/CdS nanorods via liquid interfacial assembly. The colloidal nanodisks and nanorods are coassembled into AB-, AB₂-, and AB₆-type binary arrays determined by their relative size ratio and concentration to maximize their packing density. The position and orientation of anisotropic nanocrystal building blocks are tightly controlled in the self-assembled binary and ternary lattices. The macroscopic orientation of the superlattices is further tuned by changing the liquid subphase used for self-assembly, resulting in the formation of lamellar-type binary liquid crystalline superlattices. In addition, we demonstrate a novel ternary superlattice self-assembled from two different sizes of nanodisks and a nanorod, which offers the unique opportunity to design multifunctional metamaterials. (Figure Presented).

Full text of DOI:10.1021/jacs.5b03234

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Article
Binary and Ternary Superlattices Self-Assembled
from Colloidal Nanodisks and Nanorods
Taejong Paik, Benjamin T. Diroll, Cherie R. Kagan, and Christopher B. Murray
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.5b03234 • Publication Date (Web): 30 Apr 2015
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Binary and Ternary Superlattices Self-Assembled
from Colloidal Nanodisks and Nanorods
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Taejong Paik,1 Benjamin T. Diroll,1 Cherie R. Kagan,1,2,3 and Christopher B. Murray 1,2,*
1Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104,
United States,
2Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia,
Pennsylvania 19104, United States
3Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia,
Pennsylvania 19104, United States
KEYWORDS Nanoplate, lanthanides, liquid crystals, self-assembly, anisotropic nanocrystals,
CdSe nanorods
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ABSTRACT Self-assembly of multi-component anisotropic nanocrystals with controlled
orientation and spatial distribution allows the design of novel metamaterials with unique shape-
and orientation-dependent collective properties. Although many phases of binary structures are
theoretically proposed, the examples of multi-component assemblies, which are experimentally
realized with colloidal anisotropic nanocrystals, are still limited. In this report, we demonstrate
the formation of binary and ternary superlattices from colloidal two-dimensional LaF3 nanodisks
and one-dimensional CdSe/CdS nanorods via liquid interfacial assembly. The colloidal
nanodisks and nanorods are co-assembled into AB-, AB2-, and AB6-type binary arrays
determined by their relative size ratio and concentration to maximize their packing density. The
position and orientation of anisotropic nanocrystal building blocks are tightly controlled in the
self-assembled binary and ternary lattices. The macroscopic orientation of the superlattices is
further tuned by changing the liquid sub-phase used for self-assembly, resulting in the formation
of lamellar-type binary liquid crystalline superlattices. In addition, we demonstrate a novel
ternary superlattice self-assembled from two different sizes of nanodisks and a nanorod, which
offers the unique opportunity to design multi-functional metamaterials.
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INTRODUCTION
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Colloidal self-assembly of nanocrystals has tremendous potential to fabricate complex
functional metamaterials structured at the nanoscale through a bottom-up approach.1-4 When
nanocrystals of various size, shape, and composition are self-assembled into ordered arrays,
novel collective properties arise from the controlled coupling between the nanocrystals in the
superlattices, which are governed by symmetry, coordination, inter-particle spacing, order, and
macroscopic orientation of the self-assembled structures.5-7 Among various types of nanocrystal
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building blocks, anisotropic nanocrystals are particularly interesting due to their shape- and
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orientation-dependent properties.8,
For example, semiconducting CdSe nanorods10 and
nanoplatelets11 exhibit shape-dependent polarized luminescence properties. In addition, Au
nanorods12 and Cu2-xS nanodisks13 show orientation-dependent transverse and longitudinal
plasmonic responses. For the design of optical and electrical devices, assembling anisotropic
building blocks with controlled orientation, symmetry, periodicity, and valency is crucial to
exploit their unique shape-dependent properties in devices.14-18
Many colloidal assembly approaches are employed to control the position and orientation
of anisotropic nanocrystals, for example, templated assembly,19-22 self-assembly in block
copolymers,23-25 Langmuir-Blodgett assembly,26 electric-field assisted assembly,27, 28 and drying-
mediated self-assembly.29, 30 Self-assembly of anisotropic colloidal nanocrystals into liquid
crystalline structures is a promising route to control the spatial configuration as well as the
orientation of nanocrystal building blocks over large areas.31-33 Colloidal anisotropic
nanocrystals, such as nanodisks and nanorods, are easily aligned to form self-assembled liquid
crystalline superlattices with controllable orientation.34-37 Liquid crystalline superlattices can also
be assembled from different types of nanocrystal building blocks to form multi-componenet
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systems, in which the position of one component can be directed by the anisotropic liquid
crystalline superstructure.2, 38-43 The position and orientation of multi-component anisotropic
nanocrystals can be further tailored by designing different types of binary phases possessing
unique symmetry, stoichiometry, and spatial coordination of the components in ordered arrays.
Rich phase diagrams are theoretically proposed and understood by hard particle models,44, 45 or
by the combination of particle-particle interactions driven by electrostatic force,46, 47 magnetic
interaction,48, 49 and dipole-dipole or van der Waals interaction between particles or ligands on
the particle surface.50-53 In addition, the introduction of multiple anisotropic building blocks
greatly expands the possible phase diagrams accessible for assembled structures.54-57 Therefore,
complex new materials with emergent or collective properties and tailored superlattice structures
can be designed de novo by the selection of appropriate building blocks.
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Here, we report novel binary and ternary superlattices self-assembled from two colloidal
anisotropic nanocrystals: two-dimensional nanodisks and one-dimensional nanorods. The
nanorods and nanodisks are deposited to form superlattice thin films on glycol-type polar sub-
phases via the liquid interfacial assembly technique.6 We employ lanthanum trifluoride (LaF3)
nanodisks and CdSe/CdS nanorods as building blocks. By changing the relative size ratio and
concentration of the nanodisks and nanorods and the sub-phases upon which the nanocrystals
self-assemble, AB-, AB2-, and AB6-type columnar binary lattices and lamellar-type liquid
crystalline superlattices are fabricated. Structural analysis shows these sytems to be very densely
packed. We speculate that the self-assembled structures maximize the packing density of the
building blocks, hence increasing the free-volume entropy and minimizing the Helmholtz free
energy. The position and orientation of colloidal nanodisks and nanorods are precisely controlled
in the binary lattices preserving long-range orientational and positional order. In addition, we
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observe a novel ABC-type ternary superlattice self-assembled from two nanodisks and one
nanorod, which is to our knowledge, the first example of an ordered assembly formed from three
anisotropic nanocrystals.
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RESULTS AND DISCUSSION
Colloidal LaF3 nanodisks are used as transparent dielectric nanocrystal building blocks for
self-assembly. LaF3 nanodisks are synthesized by a method previously reported in the literature
with slight modification.39 Transmission electron microscopy (TEM) (Figure 1a) shows nearly
monodisperse LaF3 nanodisks lying parallel to the substrate surface self-assemble into columnar
hexagonal arrays. Wide-angle X-ray diffractions (XRD) of these nanodisks shows sharp (100)
and (300) diffraction peaks with trigonal crystal structures (JCPDS No. 32-0483), indicating that
the nanodisks are truncated by the (001) plane and grow preferentially along the LaF3 (100)-
plane (Figure S1a, b). Wide-angle selected-area electron diffraction (SAED) of self-assembled
nanodisks shows relatively intense hexagonal electron diffraction spots representing the slight
hexagonal faceting of the nanodisks (Figure S2).
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Figure 1. TEM images of anisotropic nanocrystal building blocks. a) LaF3 nanodisks (22.3 nm
diameter with 1.6 nm thickness), b) CdSe/CdS dot-in-rods (15.1 nm in length and 3.8 nm in
diameter). c) AB2-type binary self-assembly of LaF3 nanodisks and CdSe/CdS nanorods. Inset
represents the schematic model of AB2-type superlattice and unit cell.
The size, shape, and size distribution of nanodisks are confirmed by wide-angle and small-
angle X-ray measurement and simulation. Experimentally measured X-ray diffraction patterns
match simulation results for LaF3 nanodisks that are 13.2 nm in diameter and 1.6 nm in thickness
(Figure S1a). The size of nanodisks is further tunable by the controlled over-coating of additional
layers on the core nanodisks by a seeded-growth reaction. After the over-coating, the size
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increases to about 22.3 nm in diameter with no noticeable change in thickness (Figure 1a, S1b),
as corroborated by SAXS patterns and simulations.
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Colloidal CdSe/CdS nanorods are used as a model one-dimensional building block
because of their unique optical properties and shape uniformity. CdSe/CdS dot-in-rods are
synthesized by a seeded growth method reported previously.58 Figure 1b show a representative
TEM image of the synthesized CdSe/CdS nanorods used in this study. The length and diameter
of the nanorods, which are characterized by X-ray measurement and simulation, is 15.1 nm and
3.8 nm, respectively (Figure S1c). Highly uniform nanorods self-assemble into smectic B liquid
crystalline structures using the liquid interfacial assembly method on a diethylene glycol sub-
phase. In some regions, the nanorods are vertically aligned in close-packed hexagonal arrays
(homeotropic alignment, Figure S3a) and in other regions, the nanorods are horizontally-aligned
with respect to the substrate forming smectic liquid crystalline structures (heterogeneous
alignment, Figure S3b and S3c).
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To assemble binary superlattices from these shape-engineered building blocks, the mixed
solution of LaF3 nanodisks and CdSe/CdS dot-in-rods are similarly self-assembled via the liquid
interfacial assembly technique using diethylene glygol as a sub-phase. The co-assembly of
nanodisks and nanorods into the binary lattices are observed with a small fraction of the single
component arrays of nanodisks or nanorods. Figure 1c displays a TEM image of AB2-type binary
superlattices of large LaF3 nanodisks (22.3 nm diameterⅹ 1.6 nm thickness) and CdSe/CdS
nanorods (15.1 nm length ⅹ 3.8 nm diameter). In the binary superlattices, nanodisks form
columnar liquid crystalline structures by stacking out of the plane and two vertically-aligned
nanorods fill each interstitial site between the stacked columns of nanodisks. Four sets of two
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vertically aligned nanorods (dimers) are included in binary lattices with four-fold symmetric
positions around the columns. To accommodate the inclusion of the nanorods in the interstitial
sites of the 2-dimensional triangular Bravais lattice of the columns (Figure S2), the symmetry of
self-assembled LaF3 nanodisks is deformed to a centered rectangular lattice (Figure 1c, S4).
Although the lattice structures formed by the binary mixture of nanodisks and nanorods are
analyzed as two-dimensional lattice structures, the actual structures exhibit three-dimensional
features with a stacking of nanodisks in each column. We observed that the number of nanodisks
in the columns can be varied, as seen by the difference in contrast between the columns in TEM
images (Figure S4a, b and S4c, d) The height of the columns can match the length of the
vertically aligned nanorods (Figure S5b), consistent with as many as approximately 5 to 6 disks
stacked in each single column in the binary assemblies.
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Two possible configurations of the nanorod inclusion are observed in binary superlattices.
One variant is that four sets of vertically aligned nanorod dimers around the columns are oriented
into the same direction with D2h point group symmetry, as depicted in Figure 2a. The second
variant occurs when two sets of nanorod dimers are aligned at a 90o angle in the interstitial sites
of nanodisk arrays with C2v point group symmetry, as shown in Figure 2b, which has a mirror
plane that intersects the center of the nanodisks. The simultaneous occurrence of both
configurations during the self-assembly induces twin boundaries in the superlattice structures, as
described in Figure 2c and 2d. This suggests that the energy barriers to formation for D2h and C2v
symmetry arrays are comparable or within kT such that thermal fluctuations provide enough
energy to produce both configurations.59
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Figure 2. TEM images of AB2-type binary superlattices. Colloidal LaF3 nanodisks and
CdSe/CdS nanorods are self-assembled with a) D2h point group symmetry and b) C2v point group
symmetry. c) Low magnification TEM image and d) the structural model visualizing the twin
boundary in the self-assembled AB2-type superlattices.
To understand the phase behavior of our binary superlattices, co-assembly of nanorods
with different sizes of LaF3 nanodisks is performed. When the diameter of nanodisks used for
self-assembly is decreased from 22.3 nm to 13.2 nm without changing the size of the nanorods,
AB-type binary superlattices with P4mm symmetry60 are observed predominantly where the
nanorods are vertically aligned and doped into the interstices of LaF3 nanodisk arrays, by
deforming the triangular lattices into square lattices (Figure 3a-c). For nanodisks with the larger
22.3 nm diameter, as described previously, AB2-type binary superlattices with C2mm
symmetry60 are predominantly formed where the two vertically aligned nanorods are placed at
the interstices of the centered rectangular lattices (Figure 3d-f). By increasing the concentration
of nanorods and using the same 22.3 nm diameter nanodisks and the nanorods, AB6-type binary
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lattices with P6mm symmetry is observed, where the stacked nanodisks are assembled into
hexagonal lattices while the vertically aligned nanorods are dodecagonally arrayed along the
edge of nanodisk columns, as displayed in Figure 3g-i. The grain sizes of these AB6-type binary
structures extend over larger than 10 ꢀm2, as displayed in Figure 4, while maintaining their long-
range orientational and positional orders.
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Figure 3. Self-assembled superlattices of nanodisks and nanorods depending on the relative size
ratio and concentrations. TEM images of a) a single compenent superlattice self-assembled from
13.2 nm LaF3 nanodisks and b) AB-type binary superlattice self-assembled from 13.2 nm LaF3
nanodisks and CdSe/CdS nanorods and c) the structural model of AB-type binary superlattice. d)
Single compenent superlattice self-assembled from 22.3 nm LaF3 nanodisks and e) AB2-type
superlattice self-assembled from 22.3 nm LaF3 nanodisks and CdSe/CdS nanorods and f) the
structural model of AB2-type binary superlattic. g) Low magnification and h) high magnification
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TEM images and i) the structural model of AB6-type superlattices self-assembled from 22.3 nm
LaF3 nanodisks and CdSe/CdS nanorods.
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Figure 4. a) Low- b) high- magnification TEM images and c) SEM image of AB6-type binary
superlattices self-assembled from large LaF3 nanodisks and CdSe/CdS nanorods. Inset in b)
represents the small-angle SAED pattern of AB6-type binary superlattice.
The phase diagram of binary mixtures of hard disks has been investigated theoretically,50,
61, 62
motivated by Fejes Tóth63 and Liko et. al.64 The binary structures are expected from a
theoretical model of space-filling, in which the two disk components are self-assembled into the
two-dimensional binary lattices that maximize the packing density of the system. In our binary
superlattices, all nanodisks and nanorods are aligned in the same crystallographic direction.
Therefore, a top-view of AB-, AB2-, and AB6-type superlattices represents the binary disk arrays
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by treating the vertically aligned nanorods as second disks with small diameter. This provides
guidance to explain the phase behaviors of our binary nanodisk-nanorod systems. Indeed, the
experimental results represent the theoretical models where the two components are self-
assembled into binary lattices maximizing space filling efficiency. AB-type binary arrangement
is predicted to be stable in the range of 0.155 < ρ < 0.414, where ρ = rsmall/rlarge, to maximize the
packing density.64 The diameter of small nanodisks and nanorods used for AB-type assembly,
which are calculated by X-ray measurement and simulation, are 13.2 nm and 3.8 nm,
respectively. Since our colloidal nanocrystals are coated with the long alkyl chain ligands, the
effective size can be estimated by adding the thickness of the soft ligand shell, which is
measured as the center-to-center distance of nanocrystals in the hexagonally-ordered, single-
component monolayer. The relative size ratio calculated by the effective sizes of nanocrystal
building blocks is about 0.40, which falls into the range where AB-type structures with square
lattices are favorably formed to maximize their space filling efficiency. Increasing size of the
nanodisks to 22.3 nm, results in a relative size ratio of about 0.25, which is in the range where
AB2-type binary disk mixtures are expected to be stable and form centered rectangular
lattices.(0.155 < ρ < 0.281, Table 1).64 This is confirmed by experimental observations showing
predominant AB2-type binary superlattices (Figure 4d-f). Increasing the concentration of
nanorods but maintaining the relative size ratio results in the formation of AB6-type binary
superlattices to accommodate the building blocks and maximize the packing density, which is
predicted be stable in the range of 0.101 < ρ < 0.349.64 Table 1 summarizes the ranges of
stability for different binary lattices. Although space-filling models of binary disk arrays can
explain the observed binary superlattices, the formation of these structures may involve
contributions from many additional interactions such as free volume entropy and the enthalpic
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interactions including dipole-dipole65, van der Waals66, an interaction between the ligands on the
surfaces52, and depletion attraction interactions.67 The understanding of these interactions may
enable a variety of novel binary structures with different types of anisotropic nanocrystals to be
precisely designed.
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Stoichiometry
Range of stability
0.155<ρ<0.414
0.155< ρ <0.281
0.101< ρ <0.349
Experimental size ratio(ρ)
Magic size ratio
0.414
0.397
0.251
0.251
AB
AB2
AB6
0.281
0.349
Table 1. Range of stability calculated as the two-dimensional binary lattices of hard
disks.(adapted from references 51, 61, 62, 64)
The ternary nanocrystal superlattices formed from three spherical nanocrystals have been
observed by Vanmaekelbergh et, al.68 and Murray et, al.69, however, the example of the ternary
superlattices composed of three different colloidal nanocrystals is still rare and from anistropic
building blocks is unprecedented. Here, we obtained new ternary superlattices by co-assembly of
three different anisotropic nanocrystal building blocks, small and large LaF3 nanodisks, and
CdSe/CdS nanorods. To investigate the self-assembly behavior of three components, nanocrystal
solutions used for AB-type superlattice (small nanodisks and nanorods) and AB2-type
superlattice (large nanodisks and nanorods) are mixed together in a 1:1 volume ratio and dropped
onto the surface of diethylene glycol. Locally, phase segregation to AB-type and AB2-type
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binary superlattices is observed as displayed in Figure 5a, which reflects the energetic preference
of both binary lattices over single component arrays. In addition to the AB- and AB2-type
superlattices described above, we observed the binary assembly of two different nanodisks, in
which nanodisks of each diameter are stacked to form columns and self-assembled into an AB-
type binary superlattice having an oblique 2-D Bravis lattice (Figure 5b, 5c). We also observe
ABC-type ternary superlattices with a centered rectangular lattice (Figure 5d-f), in which stacked
columns of small and large nanodisks are self-assembled into centered rectangular lattices and
vertically aligned CdSe nanorods are located in the interstices between stacked nanodisk
columns of small LaF3 nanodisks, as displayed in figure 5d-f.
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Figure 5. a) TEM images of self-assembled structures from small and large LaF3 nanodisks, and
CdSe/CdS nanorods. Phase-segregation to AB-type and AB2-type superlattices is observed. b)
TEM image and c) the structural model of an AB-type superlattice self-assembled from small
LaF3 and large LaF3 nanodisks. d) Low magnification, e) high magnification TEM images and f)
the structural model of ABC-type superlattices self-assembled from small and large LaF3
nanodisks and CdSe/CdS nanorods.
The orientation of binary liquid crystalline structures is further tuned by changing the sub-
phase upon self-assembly. When ethylene glycol is used as a sub-phase for self-assembly instead
of a diethylene glycol sub-phase, lamellar-type liquid crystalline structures are predominantly
formed with a small area of AB2-type binary lattice formation (Figure 6, S5, S6). In the lamellar-
type superlattices, nanodisks stand edge-on on the substrates and stack to form one-dimensional
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strings by face-to-face interactions. These strings are simultaneously self-assembled into
extended smectic liquid crystalline arrays. In the presence of colloidal nanorods, building blocks
are co-assembled into liquid crystalline binary lattices where nanorods lie parallel to the
substrates and are placed between two strings of LaF3 nanodisk arrays. The tip-to-tip distances
between the nanorods is close to the length of the inter-digitated ligands bound on the surface.
The nanorods are close-packed into one-dimensional arrays leaving a minimal space except for
the surface ligands. The trench formed between the arrays of nanodisk strings provides free
space to incorporate the nanorod building blocks, similar to the examples of
nanoplate/nanosphere39 and nanorod/nanosphere41 binary systems. This trench allows for the
alignment of nanorods along the orientation of lamellar liquid crystalline structures. At the edge
of superlattice, it is observed that the nanorods nearby a nanodisk arrays are already aligned
without the presence of the neighboring columns (Figure S6) indicating that the presence of the
nanodisk assemblies induces preferential alignment of the nanorods along the direction of the
nanodisk lamellar. Since dielectric LaF3 nanodisks are used as building blocks, liquid crystalline
binary structures may be utilized as a template directing one-dimensional building blocks into
long-range ordered, close-packed periodic arrays.
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Figure 6. a-c) TEM images and d) the structural model of lamella-type binary superlattices self-
assembled from large LaF3 and CdSe/CdS nanorods. Inset in b) is the wide-angle selected area
electron diffraction pattern The red colors in c) mark the position of the CdSe/CdS nanorods. e)
SEM image of lamella-type binary superlattices. Inset is high-magnification SEM image and the
structural model.
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CONCLUSION
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We demonstrate that mixtures of two and three different anistropically-shaped colloidal
nanocrystals co-assembly into binary and ternary superlattices respectively with long-range
orientational and positional order. By changing the relative size and concentration of LaF3
nanodisks and CdSe/CdS nanorods, we synthesized AB2-type, AB6-type, and two AB-type
binary superlattices as well as an ABC-type ternary superlattice, which are driven to maximize
the packing density. The orientation of superlattice structures is tunable by changing the sub-
phases upon which self-assembly occurs resulting in the formation of lamellar-type binary liquid
crystalline superlattices. In this structure, the pitch size of one-dimensionally aligned nanorods
would be further tuned in the binary lattices by changing the diameter of synthesized nanodisks.
The demonstration of binary and ternary superlattices constructed from anisotropic building
blocks shows shape-engineering of nanocrystals can be used to access new phases/structures,
which allows for the design of novel functional metamaterials by tailoring superlattice structures.
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EXPERIMENTAL SECTION
Materials. All chemicals are used as purchased without any further purification. Lanthanum(III)
oxide (99.9%), lithium fluoride (99.99%), cadmium oxide (99.99%), oleic acid (technical grade,
90%), and 1-octadecene (technical grade, 90%) are all purchased from Sigma Aldrich.
Diethylene glycol and ethylene glycol are purchased from Fisher scientific. Trifluoroacetic
acid(99.5+%) is purchased from Alfa Aesa. Lanthanum trifluoroacetate (LaTFA3) precursors are
synthesized by refluxing 10 g of lanthanum oxide in 100ml of trifluoroacetic acid and water
mixture.(50/50 vol%)
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Synthesis of LaF3 nanodisks. Colloidal LaF3 nanodisks are synthesized according to the
procedure previously reported with slight modification.39 Briefly, LiF (6 mmol) and LaTFA3 (2
mmol) are added oleic acid and 1-octadecene mixture (50/50 vol%) in a 125 mL three-neck flask.
The reaction mixture is degassed at 125°C for 2 h and then the solution is heated to 290°C under
N2 environment at a rate of 15°C/min and maintained at this temperature for 4 hours. Next, the
reaction solution is purified by precipitating nanocrystals in excess ethanol and centrifugation at
4000 rpm for 2 min. Purification process is conducted 2 times. After purification, hexane is
added into the precipitates to dissolve nanocrystals. Residual lithium fluoride, which is not
dissolved in nonpolar solvents, is simply removed by centrifugation at 3000 rpm for 2 min.
Seed-growth overcoating of LaF3 nanodisks. Mixture of nanocrystal solution, 3 mmol of LiF,
and 1 mmol of LaTFA3 are added into a 125 mL three-neck flask filled with oleic acid and 1-
octadecene mixture (50/50 vol%) and degassed at 125°C for 2 hr. and then the reaction mixture
is heated to 280°C at a rate of 15°C/min under N2 environment and maintained at this
temperature for 2 hours. The purification is conducted with the same method described earlier.
Synthesis of CdSe/CdS dot-in-rods. Synthesis of CdSe/CdS dot-in-rod samples followed
literature procedures.23, 54
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Binary assembly of LaF3 nanodisks and CdSe/CdS nanorods The liquid interfacial assembly
is performed by following the procedure reported in literature.6 Briefly, a Teflon well is filled
with diethylene glycol or ethylene glycol sub-phases. And then, 30 µL of the nanocrystal
mixtures in hexane is dropped onto the surface of sub-phases in the Teflon well and slowly dried
by covering a glass slide on the interface. Once nanocrystal solution on the interface is fully
dried to form the membrane, resulting films are transferred to carbon-coated TEM grids for
microscopic analysis. The TEM grids are further dried in the vacuum chamber to remove
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residual sub-phases. Concentration of nanocrystals used for self-assemblies is (1.6 mg + 8
mg)/ml hexane (small LaF3 and CdSe/CdS nanorods) for AB-type superlattices, (1.1 mg + 8
mg)/ml hexane (large LaF3 and CdSe/CdS nanorods) for AB2-type superlattices, (1.1 mg +
16mg)/ml (large LaF3 and CdSe/CdS nanorods) for AB6-type superlattices, and (1.6 mg + 1.1 mg
+ 8mg)/ml (small LaF3, large LaF3, and CdSe/CdS nanorods) for ABC-type superlattices.
Characterization. TEM images and electron diffraction patterns are collected using a JEM-2100
microscope equipped operating at 200 kV. Scanning electron microscopy (SEM) images are
collected on a JEOL 7500F HRSEM. Powder X-ray diffraction measurements are conducted
using a Rigaku Smartlab high-resolution diffractometer equipped with a 2.2 kW sealed tube
generator. X-ray diffraction patterns are collected using concentrated nanocrystal solutions filled
in a glass capillary enabling the diffraction patterns to be measured for randomly oriented
nanodisks. Small-angle X-ray scattering measurement are performed at the Multi-Angle X-ray
Scattering Facility at the University of Pennsylvania. The size and shape information are
extracted from X-ray simulation of wide-angle X-ray diffraction patterns and small-angle X-ray
scattering (SAXS) results.39, 70 The atomic coordinates and shape information of the nanodisks,
which are constructed from the monoclinic LaF3 unit cell (JCPDS no. 72-6288) and the statistical
size analysis from TEM images, are entered into the Debye formula to generate the simulated X-
ray patterns.
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ASSOCIATED CONTENT
Supporting Information. SAXS and WAXS patterns, additional TEM and SEM images. This
material is available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
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Corresponding Author Christopher B. Murray (cbmurray@sas.upenn.edu)
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ACKNOWLEDGMENT
We thank Dr. Paul Heiney for an analytical support on small-angle X-ray scattering
measurements. We thank the Office of Naval Research Multidisciplinary University Research
Initiative Award No. ONR-N00014-10-1-0942 for primary support for the synthesis of LaF3
nanodisks, performing the self-assembly studies, and the microscopic analysis. Synthesis of
CdSe/CdS dot-in-rods, small- and wide-angle X-ray characterizations, and X-ray simulation
were supported by the U.S. Department of Energy Office of Basic Energy Sciences, Division of
Materials Science and Engineering under award no. DE-SC0002158. C.R.K. thanks for the
support of Stephen J. Angello Professorship. C.B.M. is grateful for the support of the Richard
Perry University Professorship.
REFERENCES
(1).
(2).
Murray, C. B.; Kagan, C. R.; Bawendi, M. G., Annu. Rev. Mater. Sci. 2000, 30, 545-610.
Shevchenko, E. V.; Talapin, D. V.; Kotov, N. A.; O'Brien, S.; Murray, C. B., Nature
2005, 439, 55-59.
(3).
Grzelczak, M.; Vermant, J.; Furst, E. M.; Liz-Marzán, L. M., ACS Nano 2010, 4, 3591–
3605.
(4).
Macfarlane, R. J.; Lee, B.; Jones, M. R.; Harris, N.; Schatz, G. C.; Mirkin, C. A., Science
2011, 334, 204-208.
(5).
Urban, J. J.; Talapin, D. V.; Shevchenko, E. V.; Kagan, C. R.; Murray, C. B., Nat. Mater.
2007, 6, 115-121.
(6).
477.
(7).
(8).
(9).
Dong, A.; Chen, J.; Vora, P. M.; Kikkawa, J. M.; Murray, C. B., Nature 2010, 466, 474-
Ye, X.; Chen, J.; Diroll, B. T.; Murray, C. B., Nano Lett. 2013, 13, 1291-1297.
Kan, S.; Mokari, T.; Rothenberg, E.; Banin, U., Nat. Mater. 2003, 2, 155-158.
Jones, M. R.; Macfarlane, R. J.; Prigodich, A. E.; Patel, P. C.; Mirkin, C. A., J. Am.
Chem. Soc. 2011, 133, 18865-18869.
ACS Paragon Plus Environment
22

Page 23 of 25
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
(10). Hu, J.; Li, L.-s.; Yang, W.; Manna, L.; Wang, L.-w.; Alivisatos, A. P., Science 2001, 292,
2060-2063.
(11). Cassette, E.; Mahler, B.; Guigner, J.-M.; Patriarche, G.; Dubertret, B.; Pons, T., ACS
Nano 2012, 6, 6741-6750.
(12). Jana, N. R.; Gearheart, L.; Murphy, C. J., J. Phys. Chem. B 2001, 105, 4065-4067.
(13). Hsu, S.-W.; On, K.; Tao, A. R., J. Am. Chem. Soc. 2011, 133, 19072-19075.
(14). Rizzo, A.; Nobile, C.; Mazzeo, M.; Giorgi, M. D.; Fiore, A.; Carbone, L.; Cingolani, R.;
Manna, L.; Gigli, G., ACS Nano 2009, 3, 1506-1512.
(15). Rivest, J. B.; Swisher, S. L.; Fong, L.-K.; Zheng, H.; Alivisatos, A. P., ACS Nano 2011,
5, 3811-3816.
(16). Alvarez-Puebla, R. A.; Agarwal, A.; Manna, P.; Khanal, B. P.; Aldeanueva-Potel, P.;
Carbó-Argibay, E.; Pazos-Pérez, N.; Vigderman, L.; Zubarev, E. R.; Kotov, N. A.; Liz-Marzán,
L. M., Proc. Natl. Acad. Sci. U. S. A. 2011, 108, 8157 - 8161.
(17). Jones, M. R.; Macfarlane, R. J.; Lee, B.; Zhang, J.; Young, K. L.; Senesi, A. J.; Mirkin,
C. A., Nat. Mater. 2010, 9, 913-917.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(18). Walker, D.; Browne, K. P.; Kowalczyk, B.; Grzybowski, B. A., Angew. Chem. Int. Ed.
2010, 49, 6760-6763.
(19). Yin, Y.; Lu, Y.; Gates, B.; Xia, Y., J. Am. Chem. Soc. 2001, 123, 8718-8729.
(20). Xia, Y.; Yin, Y.; Lu, Y.; McLellan, J., Adv. Funct. Mater. 2003, 13, 907-918.
(21). Rupich, S. M.; Castro, F. C.; Irvine, W. T. M.; Talapin, D. V., Nat. Comm. 2013, 5, 5045.
(22). Greybush, N. J.; Saboktakin, M.; Ye, X.; Giovampaola, C. D.; Oh, S. J.; Berry, N. E.;
Engheta, N.; Murray, C. B.; Kagan, C. R., ACS Nano 2014, 8, 9482-9491.
(23). Thorkelsson, K.; Mastroianni, A. J.; Ercius, P.; Xu, T., Nano Lett. 2012, 12, 498-504.
(24). Zhang, Q.; Gupta, S.; Emrick, T.; Russell, T. P., J. Am. Chem. Soc. 2006, 128, 3898-
3899.
(25). Deshmukh, R. D.; Liu, Y.; Composto, R. J., Nano Lett. 2007, 7, 3662-3668.
(26). Kim, F.; Kwan, S.; Akana, J.; Yang, P., J. Am. Chem. Soc. 2001, 123, 4360–4361.
(27). Ryan, K. M.; Mastroianni, A.; Stancil, K. A.; Liu, H.; Alivisatos, A. P., Nano Lett. 2006,
6, 1479-1482.
(28). Carbone, L.; Nobile, C.; Giorgi, M. D.; Sala, F. D.; Morello, G.; Pompa, P.; Hytch, M.;
Snoeck, E.; Fiore, A.; Franchini, I. R.; Nadasan, M.; Silvestre, A. F.; Chiodo, L.; Kudera, S.;
Cingolani, R.; Krahne, R.; Manna, L., Nano Lett. 2007, 7, 2942-2950.
(29). Talapin, D. V.; Shevchenko, E. V.; Murray, C. B.; Kornowski, A.; Förster, S.; Weller, H.,
J. Am. Chem. Soc. 2004, 126, 12984-12988.
(30). Baker, J. L.; Widmer-Cooper, A.; Toney, M. F.; Geissler, P. L.; Alivisatos, A. P., Nano
Lett. 2010, 10, 195-201.
(31). Gabriel, J.-C. P.; Davidson, P., Top. Curr. Chem. 2003, 226, 119-172.
(32). Wu, K.-J.; Chu, K.-C.; Chao, C.-Y.; Chen, Y.-F.; Lai, C.-W.; Kang, C.-C.; Chen, C.-Y.;
Chou, P.-T., Nano Lett. 2007, 7, 1908-1913.
(33). Lynch, M. D.; Patrick, D. L., Nano Lett. 2002, 2, 1197-1201.
(34). Saunders, A. E.; Ghezelbash, A.; Smilgies, D.-M.; Sigman, M. B.; Korgel, B. A., Nano
Lett. 2006, 6, 2959-2963.
(35). Cao, Y. C., J. Am. Chem. Soc. 2004, 126, 7456-7457.
(36). Zhang, Y.-W.; Sun, X.; Si, R.; You, L.-P.; Yan, C.-H., J. Am. Chem. Soc. 2005, 127,
3260-3261.
ACS Paragon Plus Environment
23

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Page 24 of 25
1
2
3
4
5
6
7
8
9
(37). Ye, X.; Collins, J. E.; Kang, Y.; Chen, J.; Chen, D. T. N.; Yodh, A. G.; Murray, C. B.,
Proc. Natl. Acad. Sci. U. S. A. 2010, 107, 22430-22435.
(38). Sánchez-Iglesias, A.; Grzelczak, M.; Pérez-Juste, J.; Liz-Marzán, L. M., Angew. Chem.
Int. Ed. 2010, 49, 9985-9989.
(39). Paik, T.; Ko, D.-K.; Gordon, T. R.; Doan-Nguyen, V.; Murray, C. B., ACS Nano 2011, 5,
8322-8330.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(40). Ming, T.; Kou, X.; Chen, H.; Wang, T.; Tam, H.-L.; Cheah, K.-W.; Chen, J.-Y.; Wang,
J., Angew. Chem. Int. Ed. 2008, 47, 9685-9690.
(41). Ye, X.; Millan, J. A.; Engel, M.; Chen, J.; Diroll, B. T.; Glotzer, S. C.; Murray, C. B.,
Nano Lett. 2013, 13, 4980-4988.
(42). Paik, T.; Murray, C. B., Nano Lett. 2013, 13, 2952-2956.
(43). Nagaoka, Y.; Wang, T.; Lynch, J.; LaMontagne, D.; Cao, Y. C., Small 2012, 8, 843-846.
(44). Murray, M. J.; Sanders, J. V., Philos. Mag. A 1980, 42, 721-740.
(45). Filion, L.; Dijkstra, M., Phys. Rev. E 2009, 79, 046714.
(46). Kalsin, A. M.; Fialkowski, M.; Paszewski, M.; Smoukov, S. K.; Bishop, K. J. M.;
Grzybowski, B. A., Science 2006, 312, 420-424.
(47). Bartlett, P.; Campbell, A. I., Phys. Rev. Lett. 2005, 95, 128302.
(48). Singh, G.; Chan, H.; Baskin, A.; Gelman, E.; Repnin, N.; Král, P.; Klajn, R., Science
2014, 345, 1149-1153.
(49). Ahniyaz, A.; Sakamoto, Y.; Bergström, L., Proc. Natl. Acad. Sci. U. S. A. 2007, 104,
17570-17545.
(50). Law, A. D.; Buzza, D. M. A.; Horozov, T. S., Phys. Rev. Lett. 2011, 106, 128302.
(51). Fornleitner, J.; Verso, F. L.; Kahl, G.; Likos, C. N., Langmuir 2009, 25, 7836-7846.
(52). Ye, X.; Chen, J.; Engel, M.; Millan, J. A.; Li, W.; Qi, L.; Xing, G.; Collins, J. E.; Kagan,
C. R.; Li, J.; Glotzer, S. C.; Murray, C. B., Nat. Chem. 2013, 5, 446-473.
(53). Leunissen, M. E.; Christova, C. G.; Hynninen, A.-P.; Royall, P.; Campbell, A. I.; Imhof,
A.; Dijkstra, M.; Roij, R. v.; Blaaderen, A. v., Nature 2005, 437, 235-240.
(54). Millan, J. A.; Ortiz, D.; Anders, G. v.; Glotzer, S. C., ACS Nano 2014, 8, 2918-2928.
(55). Glotzer, S. C.; Solomon, M. J., Nat. Mater. 2007, 6, 557-562.
(56). Damasceno, P. F.; Engel, M.; Glotzer, S. C., Science 2012, 337, 453-457.
(57). Sacanna, S.; Pine, D. J., Curr. Opin. Colloid Interface Sci. 2011, 16, 96-105.
(58). Miszta, K.; Graaf, J. d.; Bertoni, G.; Dorfs, D.; Brescia, R.; Marras, S.; Ceseracciu, L.;
Cingolani, R.; Roij, R. v.; Dijkstra, M.; Manna, L., Nat. Mater. 2011, 10, 872-876.
(59). Elechiguerra, J. L.; Reyes-Gasga, J.; Yacaman, M. J., J. Mater. Chem. 2006, 16, 3906-
3919.
(60). Tschierske, C., Chem. Soc. Rev. 2007, 26, 1930-1970.
(61). Assoud, L.; Messina, R.; Löwen, H., Europhys. Lett. 2007, 80, 48001.
(62). Uche, O. U.; Stillinger, F. H.; Torquato, S., Physica A 2004, 342, 428-446.
(63). Tóth, L. F., Regular Figures. Macmillan: New York, 1964.
(64). Likos, C. N.; Henley, C. L., Philos. Mag. B 1993, 68, 85-113.
(65). Li, L.-S.; Alivisatos, A. P., Adv. Mater. 2003, 15, 408-411.
(66). Titov, A. V.; Kral, P., Nano Lett. 2008, 8, 3605-3612.
(67). Baranov, D.; Fiore, A.; Huis, M. v.; Giannini, C.; Falqui, A.; Lafont, U.; Zandbergen, H.;
Zanella, M.; Cingolani, R.; Manna, L., Nano Lett. 2010, 10, 743-749.
(68). Evers, W. H.; Friedrich, H.; Filion, L.; Dijkstra, M.; Vanmaekelbergh, D., Angew. Chem.
Int. Ed. 2009, 48, 9655-9657.
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Journal of the American Chemical Society
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(69). Dong, A.; Ye, X.; Chen, J.; Murray, C. B., Nano Lett. 2011, 11, 1804-1809.
(70). Murray, C. B.; Norris, D. J.; Bawendi, M. G., J. Am. Chem. Soc. 1993, 115, 8706-8715.
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