Article pubs.acs.org/crystal
Cuboctahedral Sb2O3 Mesocrystals Organized from Octahedral Building Blocks: More than Self-Similarity Sha-Sha Wang,†,⊥ Zhou-Hao Xing,† Guang-Yi Chen,§ Helmut Cölfen,*,∥ and An-Wu Xu*,† †
Division of Nanomaterials and Chemistry, Hefei National Laboratory for Physical Sciences at Microscale, Department of Chemistry, University of Science and Technology of China, Hefei 230026, China ⊥ Key Laboratory for Organic Electronics & Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing University of Posts and Telecommunications, 9 Wenyuan Road, Nanjing 210046, China § School of Automotive Engineering, Dalian University of Technology, Dalian 116024, China ∥ Physical Chemistry, University of Konstanz, Universitätsstraße 10, Box 714, D-78457 Konstanz, Germany S Supporting Information *
ABSTRACT: Assembly of nanoparticle building blocks over multiple length scales into hierarchically ordered structures plays an essential role in the nonclassical crystallization pathway. Although random particle aggregates are constantly observed in crystallization experiments, mesocrystals with wellshaped morphology and ordered hierarchical structure have been seldomly reported. Here, we describe the successful production of remarkable cuboctahedral Sb2O3 mesocrystals with hierarchical three-dimensional superstructures through a simple solution route. This is the first example of well-defined polyhedral mesocrystals with a cuboctahedral external morphology differing from the octahedral morphology of the building subunits. Electrostatic interactions between cetyltrimethylammonium cations (CTA+) and tartrate anions and hydrophobic interactions between the cetyltrimethylammonium bromide tails were supposed to be the driving force for the aggregation-based growth process. This novel mesocrystal formation breaks through the classical crystallization pattern and opens up a new pathway to construct mesoscale-transformed mesocrystals with hierarchical superstructures.
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INTRODUCTION Biominerals with multiscale hierarchical structures existing in nature have been intensively investigated to unravel the mechanisms for novel materials design.1−5 On the basis of some pioneering studies, a burgeoning field collectively known as the biomimetic mineralization has emerged.6,7 Recently, the classical and nonclassical crystallization of inorganic minerals has been described according to the latest developments in the biomimetic mineralization field. Unlike the ion-by-ion crystal growth model in classical crystallization, particles,8,9 clusters,10 and high density liquid droplets11 generally act as the building blocks in a nonclassical crystallization process, which is demonstrated to be an effective strategy to generate complex hierarchical structures. Although particle aggregates have been observed in some experimental studies, the ordered organization with welldefined morphologies and hierarchical superstructures for metal oxides has been much less reported.12−14 Recent studies have shown that the oriented-attachment of nanocrystals with regular morphology may lead to very complex geometrical arrangements expressing an appearance similar to the primary nanocrystal, which has been known as the self-similar assembly process. For example, through a mesoscale aggregation of © XXXX American Chemical Society
triangle nanoparticles, superstructured calcite mesocrystals with a similar triangular-shaped morphology were prepared.15 A previous study by Tian et al. reported remarkable silica mesophase crystals with multiscale hierarchical structures through self-similar assembly of primary octahedral subunits.16,17 In addition, octahedral Cu2O mesocrystals with distinct triangular external faces and regular calcite crystals consisting of three-pointed stars have been fabricated via the self-similar growth route.18,19 These facts suggest that large mesocrystals with ordered three-dimensional (3D) structures that preserve the shape and orientation of the basic building units could be spontaneously formed via mesoscale selforganized pathways. It is noted that the morphology of the primary building blocks is highly related to the final appearance of the generated mesocrystals. In some cases, the resulting mesocrystals appear to present the same shape as the building blocks.12−14 As a member of sesquioxides, Sb2O3 has been widely used in nonlinear optical devices and flame retardants.20,21 Sb2O3 Received: December 22, 2015 Revised: June 1, 2016
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DOI: 10.1021/acs.cgd.5b01810 Cryst. Growth Des. XXXX, XXX, XXX−XXX
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expressed three different polymorphs,22 and among them cubic α-Sb2O3 is most stable at an ambient pressure and temperature lower than 570 °C, which usually exhibits an octahedral appearance. In this work, we report well-shaped cuboctahedral Sb2O3 mesocrystals different from the primary octahedral building particles in terms of morphology. The formation and configuration of a mesocrystal are largely dependent on the crystal symmetry and anisotropy. Because of the crystal symmetry, the structures of mesocrystals are found to correlate well with those of primary building blocks, establishing the foundation of self-similar growth. With regard to the anisotropy, a critical factor for crystallization is involved with additives, which determine the crystallographic orientation and preferred attachment. Additives are usually introduced to tune the surface energy different crystal facets, and control crystal growth habits and aggregation behaviors. Therefore, the mesoscale self-organized process is sensitive to additives by modifying the interactions between developing nanocrystals and added molecules. Here, remarkable cuboctahedral Sb2O3 mesocrystals with hierarchical 3D superstructures have been reported using cetyltrimethylammonium bromide (CTAB) as a template and antimony potassium tartrate (KSbC4H4O7·0.5H2O) as a reagent. Unique well-shaped polyhedral metal oxide mesocrystals were synthesized with a cuboctahedral external morphology, which is different from the octahedral shape of the building subunits. On the basis of the mesoscale assembly of anisotropic nanoparticle subunits, the aggregation behavior is closely associated with self-similar growth and also differs from it. The electrostatic interaction between the positively charged CTA+ and negatively charged tartrate anions adsorbed on Sb3+exposed faces of octahedral Sb2O3 subunits is supposed to facilitate the oriented aggregation of the building blocks. A possible aggregation mechanism is proposed based on the concentration of CTAB. Our findings will thus contribute to explore more possibilities of the self-similar growth pattern as an effective approach to generate hierarchical mesocrystals.
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ethanol with sonicating for 20 min, and then the suspension was dropped on the copper grid. After ethanol evaporating, the TEM grids were prepared for measurements.
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RESULTS AND DISCUSSION Figure 1 presents the scanning electron microscopy (SEM) images of the Sb2O3 products (see Experimental Section) along
Figure 1. SEM images (a−c) and XRD result (d) of the hydrothermally synthesized cuboctahedral Sb2O3 sample at 100 °C for 9 h. The inset in (b) exhibits a schematic description of a single Sb2O3 cuboctahedron.
with the X-ray diffraction (XRD) result. At first glance, a lot of polyhedral crystals with a well-defined shape and rough surfaces are observed, and their sizes range from ca. 5 to 12 μm (Figure 1a). Closer SEM observations of the sample show its cuboctahedral shape being a truncated octahedron with 14 faces, which is enclosed by a combination of six {001} and eight {111} faces respectively, as highlighted in Figure 1b. In principle, the triangular faces are indexed as the {111} family; those are the usually exposed faces of cubic phase Sb2O3, while the square faces of this cuboctahedral crystal are assigned to the crystal facets of the {001} family.23 The high-magnification SEM image of a single cuboctahedron shows that the micrometer-scaled crystal appears to possess a porous superstructure (Figure 1c, an enlarged picture is shown in Figure S1), formed by a regular aggregation of primary octahedral subunits in three dimensions. Although octahedral building units have been reported in some cases,24,25 it is the first time that well-defined polyhedral crystals have been obtained with a cuboctahedral external morphology aggregated by octahedrons. The size of these octahedral particles determined from SEM images is about 300−800 nm. On the basis of the aggregation pattern of octahedral nanoparticles, the triangular faces of cuboctahedron crystal are constructed by the oriented {111} faces of octahedral building blocks, while the square faces of cuboctahedron are paved by pyramid vertices of octahedral subunits oriented along the (001) direction. The whole cuboctahedral structures are well-defined and highly ordered, and many pores and defects can be observed, which are the important characters for mesocrystals. A similar jagged surface of Cu2O ordered crystals was reported by Zhang et al. through a selective oxidative etching method at the expense of the {111} facets of Cu2O octahedron.26 However, a distinct mechanism of
EXPERIMENTAL SECTION
Preparation. The reagents, antimony potassium tartrate (KSbC4H4O7·0.5H2O), cetyltrimethylammonium bromide (CTAB), and sodium hydroxide (NaOH) were purchased from Sinopharm Chemical Reagent Co., Ltd. and used without any further purification. In a typical procedure, KSbC4H4O7·0.5H2O (2 mmol) and CTAB (0.1 g) were added into H2O (14 mL) and allowed to dissolve within 5 min under stirring. With dropwise addition of NaOH (1 M), the solution pH value was adjusted from pH 5 to pH 7, and a white precursor was precipitated. An 18 mL Teflon-lined autoclave containing the above mixture solution was kept at 100 °C for 9 h and then cooled in the ambient atmosphere. The prepared products were collected by centrifugation and rinsed thoroughly with distilled water and ethanol. The samples were dried at 60 °C for further analysis. Control experiments were carried out to pursue the growth stages of the crystals with varying reaction time and content of CTAB, while other conditions were kept the same. Characterization. The crystal structure information on the samples was obtained with a Rigaku X-ray diffractometer using CuKα radiation (λ: 1.54178 Å). The thermostability of the samples was examined with a TGA-50 thermal analyzer (Shimadzu Corporation) in a nitrogen atmosphere and the temperature rising rate was 10 °C min−1. The morphology of the samples was revealed with a JEOL JSM-6700F scanning electron microscopy (SEM) at 15 kV. The detailed crystallographic structure was characterized with a JEOL-2010 transmission electron microscopy (TEM) at 200 kV. A pretreatment of samples was performed by dispersing the powder in B
DOI: 10.1021/acs.cgd.5b01810 Cryst. Growth Des. XXXX, XXX, XXX−XXX
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size of 200−350 nm (Figure 2c). HRTEM image taken from several Sb2O3 subunits as marked in (c) provides insight into their crystallographic registration. The clear observations of crystalline domains from different particles reveal clear lattice fringes of cubic Sb2O3 (111) planes (d = 0.644 nm) in Figure 2d, indicating nanoparticle building units within Sb2 O3 cuboctahedrons have the same crystallographic orientation, thus indicating the formation of Sb2O3 mesocrystals. This is also demonstrated by SAED result (inset in Figure 2d) measured from large area of Figure 2c. Electron diffraction covering some nanoparticles from a larger area confirms that these particle aggregates exhibit single crystal diffraction instead of a polycrystalline case. To further confirm the octahedronbased assembly, the cuboctahedrons were ground and fractured into octahedral subunits, as arrows indicated in Figure S2, demonstrating the cuboctahedrons are built by octahedral particles. The composition and microstructure of the precursor greatly influence the nucleation and growth of the as-obtained Sb2O3 mesocrystals. Figure 3a presents the SEM image of the
the formation of our jagged faces is based on the oriented attachment of octahedral subunits. The crystal structure information on the samples was investigated using XRD analysis, as displayed in the upper portion of Figure 1d. The location of each diffraction peak is exactly the same as the standard XRD pattern (in the lower part of Figure 1d, JCPDS card No. 43-1071), implying a wellcrystallized cubic phase Sb2O3 (space group: Fd3̅m). The strongest (222) reflection indicates that Sb2O3 mesocrystals are built up by octahedral units with exposed {111} facets. The organization and crystallographic structure of the octahedron-built Sb2O3 cuboctahedrons were further explored by transmission electron microscopy (TEM) measurements. Figure 2a is a representative TEM photograph of a Sb2O3
Figure 2. (a) TEM image of a single Sb2O3 cuboctahedron. Inset in (a) is the SEM image of a single Sb2O3 cuboctahedron viewed from the same direction. (b) HRTEM photograph recorded from the edge of the Sb2O3 cuboctahedron indicated by the white box in (a). The corresponding SAED pattern is displayed in the inset (b). The arrows point to boundaries between nanoslabs. (c) TEM image of an ultrathin section of Sb2O3 cuboctahedrons. (d) HRTEM image taken from several different Sb2O3 nanoparticles of the ultramicrotomed sample, as marked in (c). The inset in (d) presents the corresponding SAED result taken along the [011̅] direction.
Figure 3. Morphology evolution of the products grown for (a) 0, (b) 1, (c) 9, and (d) 24 h. The arrows point to primary octahedral subunits.
cuboctahedron taken from the [001] direction. The highresolution TEM (HRTEM) image measured from the edge of the cuboctahedron pointed in (a) reveals distinct lattice fringes of (400) planes with the lattice spacing of 0.278 nm, as shown in Figure 2b. The [001] zone-axis selected-area electron diffraction (SAED) pattern can be readily assigned to a cubic phase Sb2O3 (the inset of Figure 2b). The oriented lattice fringes and regular SAED spots confirm that the whole assembly of blocks appears as a single crystal, which is a typical feature of a mesocrystal.27,28 As the arrows in Figure 2b show, the HRTEM image contains a couple of assembled nanoslabs with consistent lattice fringes, indicating the whole crystalline aggregates have the same 3D aligned crystallography.29 The internal structure and mutual particle orientation of Sb2O3 cuboctahedrons were further investigated using an ultramicrotome to cut through Sb2O3 cuboctahedrons. The ultrathin microtomed section of the sample displays a granular substructure organized by octahedral-like nanocrystals with a
precursor that was collected before hydrothermal treatment. The precursors display an amorphous feature with irregular morphologies, which was confirmed by XRD analysis (Figure S3). Thermogravimetric analysis (TGA) reveals that the precursors are mixtures of CTAB, tartrate anions, and Sb(OH)3 (Figure S4). The evolution track of the Sb2O3 cuboctahedrons was investigated by capturing the grown intermediates with varying reaction times. At the initial growth of 1 h, some cuboctahedron like particles comprised of oriented octahedral subunits emerged from the amorphous precursors (Figure 3b), suggesting that the aggregation process was initiated in the early stage of the reaction. It should be noted that under close examination, clear evidence is found for aggregation intermediates in the sample after 1 h reaction, a single octahedron, several octahedral aggregates and more subunit intermediates (indicated by arrows in Figure S5 enlarged from Figure 3b) coexist in the sample growth for 1 h. Therefore, it is available to C
DOI: 10.1021/acs.cgd.5b01810 Cryst. Growth Des. XXXX, XXX, XXX−XXX
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were stabilized by sorption of tartrate anions via electrostatic interactions.30 Obviously, the formation of the octahedron follows classical ion-by-ion growth. However, oriented attachment of octahedral building blocks could take place with the addition of CTAB through a nonclassical crystallization process; furthermore, the aggregated structures could be modulated by the concentrations of CTAB. Generally, increasing concentration of CTAB led to a closer packed aggregation, as indicated in Figure 4b−d. With increasing the content of CTAB, the Sb2O3 samples go through an evolution from octahedral single crystal to cuboctahedral mesocrystal to octahedral mesocrystal, demonstrating their distinct organized structures from octahedral building blocks. It is noted that no Sb2O3 cuboctahedral mesocrystals were observed when SbCl3 was used as the reagent instead of antimony potassium tartrate, indicating that the synergistic effects of tartrate anions and CTA+ cations induce the generation of mesocrystals. CTAB is proposed as the medium for self-assembly in many reports involving a lot of nanomaterials such as Au, SiO2, and CuO.31−33 With regard to the formation of aggregates, it has been reported that the driving forces inducing the self-assembly of nanoparticles include a number of distinct interactions (van der Waals, dipolar, electrostatic, hydrophobic interactions, hydrogen and coordination bonds).34,35 Here an aggregation mechanism is proposed attributing the driving forces to electrostatic interactions, the steric effects as well as hydrophobic interactions provided by CTA+ and tartrate anions. When the amorphous Sb(OH)3 precursors were formed in the initial stage, on the one hand, the adsorption of CTA+ prevented the precursor nanoparticles from excess growth that is adverse to mesoscale assembly; on the other hand, because of the electrostatic interactions between CTA+ cations and tartrate anions, CTA+ cations can firmly bind to octahedral subunits, and then CTA+ bilayers generated from hydrophobic interactions between the CTA+ nonpolar tails serve as the template and promote oriented attachment of octahedron subunits. A comparison between precursors in the presence and in the absence of CTAB is shown in Figure S6. After being rinsed by ethanol, the former displays an agglomeration of nanoparticles with a much smaller size than the latter. Previous studies imply that primary building blocks with relatively small size and weight more easily follow oriented attachment.36 The aggregated nanoparticles could spontaneously adjust the orientation and optimal location by rotation or migration to form vectorially aligned aggregation. Hydrophobic effects of the CTAB tails forming bilayers can lead the aligned aggregation of the building blocks to significantly reduce the exposed surface energy of the corresponding crystal faces. Here a possible aggregation mechanism is proposed in Figure 4e, illustrating that CTA+ cations with different concentrations could lead to distinct aggregation modes of octahedron subunits. At low concentration, the bilayers of CTAB preferentially bind to the {110} edges of high electron density, in which the polar heads of CTAB bilayers attach the edges of two individual building blocks and the nonpolar tails overlap to sequester themselves from water.37 By edge-to-edge contacts, geometric packing of the mutually oriented building units results in the relatively loose, porous aggregates,38 which further transforms into cuboctahedral mesocrystals. With an abundant CTAB content, CTAB bilayers cover over the {111} faces and induce a face-toface attachment of octahedron building blocks. The surface energy can be minimized by face-to-face attachment, and the
capture the whole aggregation process in the same sample. These results clearly show that the oriented aggregation of primary octahedral building units is attributed to the formation of novel Sb2O3 mesocrystal cuboctahedrons. After a 9 h reaction, the transformation of amorphous precursor to cuboctahedral Sb2O3 mesocrystals was completed. Sb2O3 mesocrystals were perfectly generated by vectorially aligned octahedron subunits via mesoscopic transformation, as clearly displayed in Figure 3c. Upon prolonged crystallization time to 24 h, primary octahedral subunits fused and coarsened to form larger octahedral crystals (Figure 3d). The {111} faces of mesocrystals clearly became smooth by Ostwald ripening, while the {001} faces finally vanished. At last, cuboctahedral Sb2O3 mesocrystals completely transformed to octahedral single crystals. The above growth process clearly reveals that oriented attachment of the preformed building blocks to cuboctahedron mesocrystals with ordered superstructures follows a distinct nonclassical crystallization pathway. For cubic phase Sb2O3, octahedral morphology is a common crystal shape in the presence of tartrate anions.24,25 Figure 4a shows a SEM image of octahedral Sb2O3 single crystals with smooth surfaces using antimony potassium tartrate as reagent in the absence of CTAB. The large {111} polar facets with positively charged Sb3+-terminated faces (inset in Figure 4a)
Figure 4. SEM images of the samples synthesized with varying CTAB amounts: (a) 0, (b) 0.2, (c) 0.3, and (d) 0.4 g. Inset in (a) shows an atomic reconstruction of a Sb2O3 octahedron exhibiting the Sb3+terminated {111} faces. (e) Schematic representation of the proposed aggregation pathways of octahedron subunits under different concentrations of CTAB. D
DOI: 10.1021/acs.cgd.5b01810 Cryst. Growth Des. XXXX, XXX, XXX−XXX
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(6) Xu, A. W.; Ma, Y. R.; Cölfen, H. J. Mater. Chem. 2007, 17, 415− 449. (7) Mann, S.; Webb, J.; Williams, R. J. P. Biomineralization; VCH: Weinheim, Germany, 1989. (8) Niederberger, M.; Cölfen, H. Phys. Chem. Chem. Phys. 2006, 8, 3271−3287. (9) Auyeung, E.; Li, T. I. N. G.; Senesi, A. J.; Schmucker, A. L.; Pals, B. C.; De La Cruz, M. O.; Mirkin, C. A. Nature 2013, 505, 73−77. (10) Wang, F. K.; He, C. B.; Han, M. Y.; Wu, J. H.; Xu, G. Q. Chem. Commun. 2012, 48, 6136−6138. (11) Vekilov, P. G. Cryst. Growth Des. 2004, 4, 671−685. (12) Wang, S. S.; Xu, A. W. CrystEngComm 2013, 15, 376−381. (13) Zhou, L.; Smyth-Boyle, D.; O’Brien, P. J. Am. Chem. Soc. 2008, 130, 1309−1320. (14) Cölfen, H.; Antonietti, M. Angew. Chem., Int. Ed. 2005, 44, 5576−5591. (15) Xu, A. W.; Antonietti, M.; Yu, S. H.; Cölfen, H. Adv. Mater. 2008, 20, 1333−1338. (16) Bellomo, E. G.; Deming, T. J. J. Am. Chem. Soc. 2006, 128, 2276−2279. (17) Yao, Y.; Dong, W. Y.; Zhu, S. M.; Yu, X. H.; Yan, D. Y. Langmuir 2009, 25, 13238−13243. (18) Deng, S. Z.; Tjoa, V.; Fan, H. M.; Tan, H. R.; Sayle, D. C.; Olivo, M.; Mhaisalkar, S.; Wei, J.; Sow, C. H. J. Am. Chem. Soc. 2012, 134, 4905−4917. (19) Imai, H.; Terada, T.; Yamabi, S. Chem. Commun. 2003, 484− 485. (20) Dimitrov, V.; Sakka, S. J. Appl. Phys. 1996, 79, 1736−1740. (21) Owen, S. R.; Harper, J. F. Polym. Degrad. Stab. 1999, 64, 449− 455. (22) Zhao, Z.; Zeng, Q.; Zhang, H.; Wang, S.; Hirai, S.; Zeng, Z.; Mao, W. L. Phys. Rev. B: Condens. Matter Mater. Phys. 2015, 91, 184112. (23) Lim, B.; Jiang, M. J.; Camargo, P. H. C.; Cho, E. C.; Tao, J.; Lu, X. M.; Zhu, Y. M.; Xia, Y. N. Science 2009, 324, 1302−1305. (24) Zhang, L.; Pan, C. L.; Liu, Y. Mater. Lett. 2012, 75, 29−32. (25) Ma, X. C.; Zhang, Z. D.; Li, X. B.; Du, Y.; Xu, F.; Qian, Y. T. J. Solid State Chem. 2004, 177, 3824−3829. (26) Shang, Y.; Sun, D.; Shao, Y. M.; Zhang, D. F.; Guo, L.; Yang, S. H. Chem. - Eur. J. 2012, 18, 14261−14266. (27) Cölfen, H.; Mann, S. Angew. Chem., Int. Ed. 2003, 42, 2350− 2365. (28) Zhou, L.; Smyth Boyle, D.; O’Brien, P. Chem. Commun. 2007, 144−146. (29) Zhang, Z. P.; Sun, H. P.; Shao, X. Q.; Li, D. F.; Yu, H. D.; Han, M. Y. Adv. Mater. 2005, 17, 42−47. (30) Wang, D. B.; Zhou, Y. H.; Song, C. X.; Shao, M. Q. J. Cryst. Growth 2009, 311, 3948−3953. (31) Yamaguchi, A.; Uejo, F.; Yoda, T.; Uchida, T.; Tanamura, Y.; Yamashita, T.; Teramae, N. Nat. Mater. 2004, 3, 337−341. (32) Sau, T. K.; Murphy, C. J. Langmuir 2005, 21, 2923−2929. (33) Li, J. Y.; Xiong, S. L.; Xi, B. J.; Li, X. G.; Qian, Y. T. Cryst. Growth Des. 2009, 9, 4108−4115. (34) Talapin, D. V. ACS Nano 2008, 2, 1097−1100. (35) Whitesides, G. M.; Grzybowski, B. Science 2002, 295, 2418− 2421. (36) Chen, J. S.; Zhu, T.; Li, C. M.; Lou, X. W. Angew. Chem., Int. Ed. 2011, 50, 650−653. (37) Yang, Y.; Matsubara, S.; Nogami, M.; Shi, J. L.; Huang, W. M. Nanotechnology 2006, 17, 2821−2827. (38) Cölfen, H.; Antonietti, M. Mesocrystals and Nonclassical Crystallization; John Wiley & Sons: Chichester, U. K., 2008.
resulting more packed assembly could fuse to form octahedronshaped mesocrystals. Currently, the detailed growth mechanism is still under investigation; nevertheless, it is obvious that these structures are found to correlate closely with oriented aggregation from primary geometrical building blocks. Notably, it not only replicates the shape of primary building blocks but also provides more possibilities to fabricate complex hierarchical superstructures constructed by oriented attachment of polyhedral subunits; therefore, this is a novel growth mode generated from but beyond self-similar growth. How to regulate the anisotropy of different edges and faces of crystals will be the key point we will investigate in the future.
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CONCLUSIONS In summary, we have demonstrated novel Sb2O3 mesocrystal cuboctahedrons aggregated from primary octahedral building units using CTAB as the additive. Electrostatic interactions between CTA+ cations and tartrate anions, and the hydrophobic effect between the CTAB tails were proposed to induce the assembly of mesocrystals. According to the CTAB linking to the {110} edges or {111} faces of octahedral building units, oriented aggregation modes could be divided into two kinds: edge-to-edge and face-to-face attachment, leading to distinct superstructures of mesocrystals. The well-defined polyhedral mesocrystals present a cuboctahedral external morphology differing from the octahedral morphology of the building blocks. This fact breaks through the classical crystallization pathway and opens up a new strategy to construct mesoscaleorganized mesocrystals with hierarchical superstructures.
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ASSOCIATED CONTENT
* Supporting Information S
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.cgd.5b01810. XRD pattern, TGA result, and SEM images for Sb2O3 cuboctahedral mesocrystals (PDF)
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AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected] (H.C.). *E-mail:
[email protected] (A.W.X.). Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The authors acknowledge financial support from cooperation between NSFC and Netherlans Organisation for Scientific Research (51561135011), the National Natural Science Foundation of China (51572253, 21271165), and Nanjing University of Posts and Telecommunications Scientific Foundation (NY215055).
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REFERENCES
(1) Antonietti, M.; Ozin, G. A. Chem. - Eur. J. 2004, 10, 28−41. (2) Bäuerlein, E. Biomineralization; Wiley-VCH: Weinheim, Germany, 2000. (3) Lowenstam, H. A.; Weiner, S. On Biomineralization; Oxford University Press: New York, 1989. (4) Mann, S. Biomineralization, Principles and Concepts in Bioinorganic Materials Chemistry; Oxford University Press: Oxford, U. K., 2001. (5) Meldrum, F. C.; Cölfen, H. Chem. Rev. 2008, 108, 4332−4432. E
DOI: 10.1021/acs.cgd.5b01810 Cryst. Growth Des. XXXX, XXX, XXX−XXX
