Shape-Controlled Synthesis of Hollow Silica Colloids - Langmuir (ACS

Subscriber access provided by TEXAS STATE UNIV SAN MARCOS

Article

Shape-Controlled Synthesis of Hollow Silica Colloids Yong Wang, Xiaowen Su, Panshuang Ding, Shan Lu, and Huaping Yu Langmuir, Just Accepted Manuscript • DOI: 10.1021/la402769u • Publication Date (Web): 19 Aug 2013 Downloaded from http://pubs.acs.org on September 1, 2013

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Langmuir is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 28

1 2 3 4 5 6 7 8 9 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

Langmuir

Shape-Controlled Synthesis of Hollow Silica Colloids Yong Wang,* Xiaowen Su, Panshuang Ding, Shan Lu, and Huaping Yu

Department of Chemistry, Capital Normal University, Beijing, 100048, China.

ABSTRACT. In this work, hollow silica colloids with different shapes, such as pseudocubes, ellipsoids, capsules and peanuts, have been synthesized through the following process: silica coating on the surface of hematite colloidal particles with different shapes (pseudocubes, ellipsoids, capsules and peanuts) and the sequential acid-dissolution of the hematite cores. The as-obtained hollow silica colloids with different shapes have uniform sizes, shapes and shells.

ACS Paragon Plus Environment

1

Langmuir

1 2 3 4 5 6 7 8 9 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

Page 2 of 28

1. INTRODUCTION Hollow micro- and nanostructures have high specific surface areas, capsulation capacity, and better permeation, and hence they have widespread potential applications in catalysis,1 photocatalysis,2 gas sensors,3 lithium batteries,4 and other areas. To satisfy the different requirements of such applications, remarkable progress has been made for the fabrication of hollow materials with varying sizes and shapes.5-12 As we know, the strategies for synthesizing hollow structures can be broadly divided into two categories: template and template-free methods. The template-free formation of hollow structures is generally based on some selfassembly or novel mechanisms such as Ostwald ripening.13 The template method has been demonstrated to be a powerful method because of its general versatility in fabricating narrowsize-distribution hollow colloids of a wide range of materials with well-defined shapes; the widely employed colloidal templates include monodispersed silica spheres,14 polymer latex spheres,15,16 carbon nanoparticles,17 and reducing metal nanoparticles.18 Usually, the size of the obtained hollow structures can be finely controlled through precise manipulation of the template dimensions. However, the hollow structures obtained by template method are mostly spherical in shape, and the shapes of the hollow structures are limited due to difficulty in obtaining uniform nonspherical sacrificial templates with different shapes. Moreover, available methods for the controlled synthesis of nonspherical monodispering hollow particles with uniform sizes, shapes and shells are rather limited due to difficulty in forming uniform coating around high-curvature surfaces. Thus, it is still a big challenge to develop a facile method to fabricate uniform nonspherical oxides hollow structures with different shapes. Silica materials have been studied in diverse application fields owing to their structural flexibility and unique properties, including biomedical applications,19 drug release,20 lithium-ion batteries.21 Recently, various hollow micro- and nanostructures of silica, such as hollow


2

Page 3 of 28

1 2 3 4 5 6 7 8 9 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

Langmuir

spheres,22-25 multi-shelled hollow nanospheres,26 hollow ellipsoids,27,28 nonspherical hollow colloids,29 and other hollow structures, have been synthesized by different methods. Despite these successes, it is still a big challenge to explore simpler and more efficient strategies for the shape-controlled synthesis of hollow silica colloids with uniform sizes, shapes and shells. Scheme 1. Schematic illustration of the shape-controlled synthesis of hollow silica colloids: (i) hematite colloidal particles with different morphologies, (ii) silica shell structures with hematite cores, and (iii) as-prepared hollow silica colloids.

Herein, we report a shape-controlled synthesis of various hollow silica colloids using hematite colloidal particles with different shapes as templates. The synthesis procedure of hollow silica colloids with different shapes is depicted in Scheme 1. In the first step, hematite colloidal particles with different shapes, such as pseudocubes, ellipsoids, capsules and peanuts, are prepared by adjusting the amount of Na2SO4 in the reaction system;30,31 in the next step, colloidal hematite templates with different shapes can be coated with silica to form a hematite core- silica shell structure; in the final step, after the hematite cores are removed by dissolving in HCl


3

Langmuir

1 2 3 4 5 6 7 8 9 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

Page 4 of 28

solution, the hollow silica colloids with different shapes are produced. It is noted that the shapes of these hollow silica colloids are similar to those of their hematite templates. 2. EXPERIMENTAL SECTION Preparation of hematite colloidal particles with different shapes. All the reagents were of analytical grade, and used without further purification. The synthesis of hematite colloidal particles with different shapes was achieved by a process based on a method developed by Sugimoto et al.30,31 In a typical synthesis of peanut-shaped hematite colloidal particles, a NaOH solution (90 mL, 6.0 M) was added to 100 mL of well-stirred 2.0 M FeCl3 in a 250 mL Pyrex bottle during 5 min, followed by the addition of Na2SO4 solution (10 mL, 0.60 M), and the agitation was continued for an additional 10 min. The tightly stoppered bottle containing the Fe(OH)3 gel, which nominally consisted of 0.9 M Fe(OH)3, 0.1 M Fe3+ and 30 mM SO42-, was placed in a laboratory oven preheated to 100 oC and the gel was aged for 8 days. After the treatment, red products were collected by filtration, washed three times with deionized water and ethanol before drying at 50 oC overnight. For the synthesis of capsule-shaped, ellipsoid-shaped and pseudocube-shaped hematite colloidal particles, the procedure was similar to the preparation of peanut-shaped hematite colloidal particles except that the concentration of the added Na2SO4 solution (10 mL) was decreased from 0.60 M to 0.20 M, 0.06 M and 0 M respectively, that is, the final Na2SO4 concentration was decreased from 30 mM to 10 mM, 3 mM and 0 mM respectively. Preparation of hollow silica colloids with different shapes. The synthesis of hollow silica colloids with different shapes, including hollow pseudocubes, hollow ellipsoids, hollow capsules and hollow peanuts, was achieved by a solution process using the pre-fabricated hematite colloidal particles with different shapes as sacrificial templates. Silica-coated hematite particles were prepared with the modified Stöber method for synthesis of monodisperse silica solid spheres.32 For a typical silica coating, hematite colloidal particles (0.6 g) with different shapes


4

Page 5 of 28

1 2 3 4 5 6 7 8 9 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

Langmuir

were first dispersed by ultrasonication in a mixture consisting of 100 mL of ethanol and 5 mL of deionized water, followed by addition of 15mL of NH3·H2O (25%). The mixture was poured into 250 mL Pyrex bottle, which was then placed in an ultrasonic water bath under 50 oC. Then, 0.5 mL of Tetraethyl orthosilicate (TEOS) was added. After aged for 5 h, the products were collected by filtration, washed three times with deionized water and ethanol before vacuum-drying at 80 oC for 10 h. As-prepared hematite/silica core/shell particles were almost etched with HCl solution (4 M) at 100 oC for 48 h to obtain hollow silica colloids without hematite cores. Characterization. X-ray diffraction (XRD) patterns of the samples were recorded with X-ray powder diffraction (XRD, Bruker, D8 ADVANCE). The morphology and structure of the samples were further investigated by field emission scanning electron microscopy (FESEM, Hitachi, S-4800) with energy-dispersive X-ray (EDX) spectroscopy, and transmission electron microscopy (TEM, FEI, Tecnai G2 F30, 300KV) with energy-dispersive X-ray (EDX) spectroscopy. 3. RESULTS AND DISCUSSION The initial colloidal hematite templates with different shapes, such as pseudocubes, ellipsoids, capsules and peanuts, were prepared by adjusting the amount of Na2SO4 in the reaction system.30,31 Figure 1 shows FESEM images of the products, indicating that the hematite colloidal particles with different shapes are well monodisperse and nearly uniform with sizes in the range of 1.5 to 2.5 µm. As shown in Figure S1 (Supporting Information), XRD analyses indicate that all the as-obtained samples are identified as the single phase hematite (α-Fe2O3) with wellcrystallized rhombohedral structure (a=0.5038 nm, c=1.3772 nm, JCPDS file No. 24-0072). No peaks from other phases are found, suggesting high purity of the final products.


5

Langmuir

1 2 3 4 5 6 7 8 9 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

Page 6 of 28

Figure 1. Typical FESEM images of hematite (α-Fe2O3) colloidal particles with different shapes: (a) pseudocubes; (b) ellipsoids; (c) capsules; and (d) peanuts. After the silica is deposited onto hematite templates with different shapes, hematite core coated silica shell is obtained (Figure 2 and Figure S2-3). Figure 2 shows the TEM image of differently shaped hematite/silica core/shell particles possessing a core with an average diameter of 1.5-2.5 µm and a uniform shell with the thickness of 90-110 nm. The reaction mechanism was reported in the literature.33 It is known that high density of hydroxyl (-OH) groups on the outer surface of naked hematite particles (Figure S4, Supporting Information), represents the main source of reactive groups for subsequent chemical surface engineering.30,31 These -OH groups on the surface of hematite particles are, however, coupled with silicic acid molecules formed directly from TEOS, which polymerizes with the increase of pH value caused by the presence of ammonia. Consequently, the resulted silanol groups (Si-OH) are further condensed to covalent siloxanes bonds (Si-O-Si) that leads to the formation of silica coating layer that surrounds the particle core.33,34


6

Page 7 of 28

1 2 3 4 5 6 7 8 9 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

Langmuir

In order to further confirm the formation of hematite core- silica shell structures with different shapes, we investigated the selective removal of hematite cores in HCl solution. After the asprepared hematite core- silica shell structures with different shapes were almost etched with HCl solution (4 M) at 100 oC for 48 h, various hollow silica colloids with different shapes, such as pseudocubes, ellipsoids, capsules and peanuts, were synthesized from hematite core- silica shell with similar shapes. The shapes and sizes of the hollow silica colloids were almost identical to the hematite templates. In order to obtain more information on hollow silica colloids with different shapes, the morphology and structure of hollow silica colloids with different shapes were investigated by FESEM, TEM and XRD.

Figure 2. TEM images of differently shaped hematite/silica core/shell particles: (a) pseudocubes; (b) ellipsoids; (c) capsules; and (d) peanuts. As shown in Figure 3a, when pseudocube-shaped hematite colloidal particles are used as templates, the as-prepared sample is mainly composed of pseudocubic cages with edge-length of about 1.5 µm. The interior space of the hollow pseudocubic silica is clearly revealed on the SEM image for some broken silica pseudocubes (Figure 3a-b). Figure 3c-d gives the typical TEM


7

Langmuir

1 2 3 4 5 6 7 8 9 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

Page 8 of 28

images of the pseudocubic hollow silica colloids. Each pseudocubic structure has a uniform shell with the thickness of 90-110 nm (Figure 3d). Such a novel template process can be extended to the synthesis of ellipsoid-shaped hollow silica colloids. As shown in Figure 3e-f, the as-synthesized product exhibits a hollow ellipsoidshaped morphology with length of about 1.5 µm and width of about 1.2 µm. The TEM images of such prepared ellipsoids (Figure 3g) show that the final product with hollow structure is in high yield. Through the magnified TEM image (Figure 3h), it can be seen that the shell of the ellipsoid-shaped cage is 90-110 nm in thickness. By carefully using the hematite templates with other shapes, various hollow silica colloids with other well-defined shapes were explored. The capsule-shaped hollow colloidal particle discussed below is a good example further demonstrating the interesting concept. The representative SEM patterns of the capsules shown in Figure 3i clearly indicate that there exist a large number of microcapsules with length of about 2 µm and width of about 1 µm. As shown in Figure 3j, the incomplete capsule reveals that the architecture of the capsule is empty in the interior. Figure 3k-l shows the corresponding TEM images of the sample, which indicate that the boundary of the shell of the hollow capsules is quite defined, and the thickness of the shell is 90-110 nm. Hollow silica colloids are synthesized from hematite templates with similar morphologies, which inspires us to extend the template to peanut-shaped hematite. Interestingly, the as-prepared sample is mainly composed of peanuts with lengths of about 2.2 µm (Figure 3m), and has a hollow interior (Figure 3n). The structure of the sample is further characterized by TEM. As shown in Figure 3o, the edges and centers of the peanuts show strong brightness contrast, further confirming their hollow nature. Through the magnified TEM image (Figure 3p), it can be seen that the shell of the peanut is 90-110 nm in thickness.


8

Page 9 of 28

1 2 3 4 5 6 7 8 9 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

Langmuir

Figure 3. FESEM and TEM images of hollow silica colloids with different shapes: (a-d) pseudocubes; (e-h) ellipsoids; (i-l) capsules; and (m-p) peanuts. The element composition is further confirmed with energy dispersive X-ray (EDX) spectroscopy analysis under STEM. EDX point spectra, taken from the center point of hollow colloidal particles with different shapes, show strong Si and O signals, and no Fe signal is found (Figure 4). As depicted in EDX line scans (Figure S5, Supporting Information), both Si and O are


9

Langmuir

1 2 3 4 5 6 7 8 9 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

Page 10 of 28

mainly distributed in the region between the two shells, while the weaker signal in the center suggests that the inner cavity remains hollow.

Figure 4. EDX point spectra taken from the center point of hollow colloidal particles with different shapes: (a) pseudocube; (b) ellipsoid; (c) capsule; and (d) peanut. The weak Cu and C peaks are attributed to the carbon-coated Cu grid used in TEM. The scale bar of inset in (g) is 500 nm. Figure S6 (Supporting Information) displays the X-ray diffraction (XRD) patterns of the asobtained hollow colloids with different shapes. In Figure S6 (Supporting Information), the silica hollow colloids are amorphous as evident from the presence of a single broad peak centered at


10

Page 11 of 28

1 2 3 4 5 6 7 8 9 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

Langmuir

about 23o,21 and no peaks from hematite (α-Fe2O3) are observed. The above investigations indicate that the hematite cores are almost etched by HCl solution and the silica hollow colloids with different shapes are produced, which conforms to the above TEM, SEM observations and EDX spectra. As shown in Figure 5, specific surface areas of silica solid spheres (Figure S7, Supporting Information), hollow pseudocubes, hollow ellipsoids, hollow capsules, and hollow peanuts are 10.4 m2·g-1, 26.7 m2·g－1, 26.9 m2·g－1, 26.5 m2·g－1, and 28.5 m2·g－1, respectively. In addition, pore volumes of silica solid spheres, hollow pseudocubes, hollow ellipsoids, hollow capsules, and hollow peanuts are 0.015 cm3 g-1, 0.033 cm3 g-1, 0.033 cm3 g-1, 0.037 cm3 g-1, and 0.036 cm3 g-1, respectively. Based on specific surface areas and pore volumes, we can deduce that there are a few pores on the surface of hollow silica with different shapes. Through a few pores on the surface of hollow silica with different shapes, the hematite cores can be almost etched with HCl solution, but high concentration of HCl solution (4 M) and long etching time (at least 24 h) must be used.


11

Langmuir

1 2 3 4 5 6 7 8 9 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

Page 12 of 28

Figure 5. The nitrogen adsorption/desorption isotherm of hollow silica colloids with different shapes and solid particles: (a) solid particles and pseudocubes; (b) ellipsoids; (c) capsules; (d) peanuts. In order to investigate the effect of the amount of TEOS on the structures of hollow silica colloids, different amount of TEOS was added to prepare peanut-shaped hollow silica colloids. As shown in Figure 6 and Table 1, the shell thickness of peanut-shaped hollow silica colloids can be easily tailored by varying the amount of TEOS. In addition, with the increase of TEOS amount from 0.15 ml to 1.2 ml, the shell thickness increases and breakage of the hollow structures decreases. When the amount of TEOS is 0.9 ml, hollow particles with wall holes can hardly be observed (Figure 6j). However, when the amount of TEOS is 1.2 ml, a lot of submicrometer spheres can be observed (Figure S8, Supporting Information).


12

Page 13 of 28

1 2 3 4 5 6 7 8 9 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

Langmuir

Figure 6. FESEM and TEM images of the peanut-shaped hollow silica colloids prepared with different amount of TEOS: (a-c) 0.15 mL; (d-f) 0.3 mL; (g-i) 0.7 mL; (j-l) 0.9 mL; (m-o) 1.2 mL.

Table 1 Shell thickness of the peanut-shaped hollow silica colloids prepared with different amount of TEOS. TEOS/mL

Shell thickness/nm

0.15

29±5

0.3

71±5

0.5

104±5

0.7

156±8

0.9

211±8

1.2

230±10


13

Langmuir

1 2 3 4 5 6 7 8 9 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

Page 14 of 28

4. CONCLUSIONS In summary, shape-controlled synthesis of hollow silica colloids has been successfully achieved by using monodisperse hematite colloidal particles with different shapes as effective sacrificial templates. Firstly, hematite colloidal particles with different shapes, such as pseudocubes, ellipsoids, capsules and peanuts, are controlled-synthesized by adjusting the amount of Na2SO4 in the reaction system; secondly, the silica is deposited onto hematite templates with different shapes to form a hematite core- silica shell structure; finally, the hematite cores are almost etched by HCl solution, which results in the formation of the silica hollow colloids with different shapes. Compared with the reported procedures for hollow particles with different shapes,6-12 the present approach has four main characteristics: (1) the shapes of hollow colloids can be easily tailored by simply adjusting the amount of Na2SO4 in the formation process of hematite templates; (2) no protective surfactant is used, and no prior surface functionalization or modification before the surface coating step of hematite colloidal particles is required, so as-prepared hollow silica colloids should have relatively clean surfaces, which are important in some application areas needing strict surface chemistry requirements, such as catalysis, electrochemistry, sensing, etc; (3) the as-obtained hollow colloids with different shapes have uniform sizes, shapes and shells. (4) Hollow silica colloids were generally prepared in alkaline media and HF solution. The disadvantage of this etching agent is that it is extremely corrosive and toxic and thus the handling is not convenient.24 In this work, the core templates can be almost etched to form hollow colloids with different shapes by HCl solution.

ASSOCIATED CONTENT


14

Page 15 of 28

1 2 3 4 5 6 7 8 9 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

Langmuir

Supporting Information. Figures S1–S8. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author E-mail: [email protected].

Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This work was supported by the General Program of Science and Technology Development Project of Beijing Municipal Education Commission (No. KM201210028019) and Beijing Natural Science Foundation (No. 2102009). REFERENCES (1)

Ching, S.; Kriz, D. A.; Luthy, K. M.; Njagi, E. C.; Suib S. L. Self-assembly of

Manganese Oxide Nanoparticles and Hollow Spheres. Catalytic Activity in Carbon Monoxide Oxidation. Chem. Commun. 2011, 47, 8286-8288. (2)

Xu, X. J.; Fang, X. S.; Zhai, T. Y.; Zeng, H. B.; Liu, B. D.; Hu, X. Y.; Bando, Y.;

Golberg, D. Tube-in-Tube TiO2 Nanotubes with Porous Walls: Fabrication, Formation Mechanism, and Photocatalytic Properties. Small 2011, 7, 445-449. (3)

Zhang, H. G.; Zhu, Q. S.; Zhang, Y.; Wang, Y.; Zhao, L.; Yu, B. One-Pot Synthesis and

Hierarchical Assembly of Hollow Cu2O Microspheres with Nanocrystals-Composed Porous Multishell and Their Gas-Sensing Properties. Adv. Funct. Mater. 2007, 17, 2766-2771.


15

Langmuir

1 2 3 4 5 6 7 8 9 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

(4)

Page 16 of 28

Wang, X.; Wu, X. L.; Guo, Y. G.; Zhong, Y. T.; Cao, X. Q.; Ma, Y.; Yao, J. N. Synthesis

and Lithium Storage Properties of Co3O4 Nanosheet-Assembled Multishelled Hollow Spheres. Adv. Funct. Mater. 2010, 20, 1680-1686. (5)

Hwang, L.; Zhao, G. P.; Zhang, P. J.; Rosi, N. L. Size-Controlled Peptide-Directed

Synthesis of Hollow Spherical Gold Nanoparticle Superstructures. Small 2011, 7, 1939-1942. (6)

Langille, M. R.; Personick, M. L.; Zhang, J.; Mirkin, C. A. Bottom-Up Synthesis of Gold

Octahedra with Tailorable Hollow Features. J. Am. Chem. Soc. 2011, 133, 10414-10417. (7)

Chen, D.; Ye, J. H. Hierarchical WO3 Hollow Shells: Dendrite, Sphere, Dumbbell, and

Their Photocatalytic Properties. Adv. Funct. Mater. 2008, 18, 1922-1928. (8)

Fei, J. B.; Cui, Y.; Yan, X. H.; Qi, W.; Yang, Y.; Wang, K. W.; He, Q.; Li, J. B.

Controlled Preparation of MnO2 Hierarchical Hollow Nanostructures and Their Application in Water Treatment. Adv. Mater. 2008, 20, 452-456. (9)

Fei, J. B.; Cui, Y.; Yan, X. H.; Yang, Y.; Wang, K. W.; Li, J. B. Controlled Fabrication of

Polyaniline Spherical and Cubic Shells with Hierarchical Nanostructures. ACS Nano 2009, 3, 3714-3718. (10) Yang, X. F.; Fu, J. X.; Jin, C. J.; Chen, J.; Liang, C. L.; Wu, M. M.; Zhou,W. Z. Formation Mechanism of CaTiO3 Hollow Crystals with Different Microstructures. J. Am. Chem. Soc. 2010, 132, 14279-14287. (11) Kozlovskaya,V.; Higgins, W.; Chen, J.; Kharlampieva, E. Shape Switching of Hollow Layer-by-layer Hydrogel Microcontainers. Chem. Commun. 2011, 47, 8352-8354.


16

Page 17 of 28

1 2 3 4 5 6 7 8 9 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

Langmuir

(12) Cao, J.; Zhu, Y. C.; Bao, K. Y.; Shi, L.; Liu, S. Z.; Qian, Y. T. Microscale Mn2O3 Hollow Structures: Sphere, Cube, Ellipsoid, Dumbbell, and Their Phenol Adsorption Properties. J. Phys. Chem. C 2009, 113, 17755-17760. (13) Wang,W. S.; Zhen, L.; Xu, C. Y.; Shao, W. Z. Aqueous Solution Synthesis of Cd(OH)2 Hollow Microspheres via Ostwald Ripening and Their Conversion to CdO Hollow Microspheres. J. Phys. Chem. C 2008, 112, 14360-14366. (14) Strandwitz, N. C.; Shaner, S.; Stucky, G. D. Compositional Tunability and High Temperature Stability of Ceria–zirconia Hollow Spheres. J. Mater. Chem. 2011, 21, 1067210675. (15) Zeng, H. B.; Xu, X. J.; Bando, Y.; Gautam, U. K.; Zhai, T. Y.; Fang, X. S.; Liu, B. D.; Golberg, D. Template Deformation-Tailored ZnO Nanorod/Nanowire Arrays: Full Growth Control and Optimization of Field-Emission. Adv. Funct. Mater. 2009, 19, 3165-3172. (16) Zhao, B.; Collinson, M. M. Hollow Silica Capsules with Well-Defined Asymmetric Windows in the Shell. Langmuir 2012, 28, 7492-7497. (17) Dong, Z. H.; Lai, X. Y.; Halpert, J. E.; Yang, N. L.; Yi, L. X.; Zhai, J.; Wang, D.; Tang, Z. Y.; Jiang, L. Accurate Control of Multishelled ZnO Hollow Microspheres for Dye-Sensitized Solar Cells with High Efficiency. Adv. Mater. 2012, 24, 1046-1049. (18) Yin,Y. D.; Rioux, R. M.; Erdonmez, C. K.; Hughes, S.; Somorjai, G. A.; Alivisatos, A. P. Formation of Hollow Nanocrystals Through the Nanoscale Kirkendall Effect. Science 2004, 304, 711-714.


17

Langmuir

1 2 3 4 5 6 7 8 9 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

Page 18 of 28

(19) Chen,Y.; Chu, C.; Zhou, Y. C.; Ru, Y. F.; Chen, H. R.; Chen, F.; He, Q. J.; Zhang, Y. L.; Zhang, L. L.; Shi, J. L. Reversible Pore-Structure Evolution in Hollow Silica Nanocapsules: Large Pores for siRNA Delivery and Nanoparticle Collecting. Small 2011, 7, 2935-2944. (20) Zhu, Y. F.; Shi, J. L.; Shen, W. H.; Dong, X. P.; Feng, J. W.; Ruan, M. L.; Li, Y. S. Stimuli-Responsive

Controlled

Drug

Release

from

a

Hollow

Mesoporous

Silica

Sphere/Polyelectrolyte Multilayer Core–Shell Structure. Angew. Chem. Int. Ed. 2005, 44, 50835087. (21) Sasidharan, M.; Liu, D.; Gunawardhana, N.; Yoshio, M.; Nakashima, K. Synthesis, Characterization and Application for Lithium-ion Rechargeable Batteries of Hollow Silica Nanospheres. J. Mater. Chem. 2011, 21, 13881-13888. (22) Baù, L.; Bártová, B.; Arduini, M.; Mancin, F. Surfactant-free Synthesis of Mesoporous and Hollow Silica Nanoparticles with an Inorganic Template. Chem. Commun. 2009, 7584-7586. (23) Du, L.; Liao, S. J.; Khatib, H. A.; Stoddart, J. F.; Zink, J. I. Controlled-Access Hollow Mechanized Silica Nanocontainers. J. Am. Chem. Soc. 2009, 131, 15136-15142. (24) Yu, Q. Y.; Wang, P. P.; Hu, S.; Hui, J. F.; Zhuang, J.; Wang, X. Hydrothermal Synthesis of Hollow Silica Spheres under Acidic Conditions. Langmuir 2011, 27, 7185-7191. (25) Zhang, L. J.; Acunzi, M. D.; Kappl, M.; Auernhammer, G. K.; Vollmer, D.; van Kats, C. M.; van Blaaderen, A. Hollow Silica Spheres: Synthesis and Mechanical Properties. Langmuir 2009, 25, 2711-2717.


18

Page 19 of 28

1 2 3 4 5 6 7 8 9 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

Langmuir

(26) Liu, J.; Hartono, S. B.; Jin, Y. G.; Li, Z.; Lu, G. Q.; Qiao, S. Z. A Facile Vesicle Template Route to Multi-shelled Mesoporous Silica Hollow Nanospheres. J. Mater. Chem. 2010, 20, 4595-4601. (27) Sacanna, S.; Rossi, L.; Kuipers, B. W. M.; Philipse, A. P. Fluorescent Monodisperse Silica Ellipsoids for Optical Rotational Diffusion Studies. Langmuir 2006, 22, 1822-1827. (28) Hao, L. Y.; Zhu, C. L.; Jiang, W. Q.; Chen, C. N.; Hu, Y.; Chen, Z. Y. Sandwich Fe2O3@SiO2@PPy Ellipsoidal Spheres and Four Types of Hollow Capsules by Hematite Olivary Particles. J. Mater. Chem. 2004, 14, 2929-2934. (29) Lee, S. H.; Gerbode, S. J.; John, B. S.; Wolfgang, A. K.; Escobedo, F. A.; Cohen, I.; Liddell, C. M. Synthesis and Assembly of Nonspherical Hollow Silica Colloids under Confinement. J. Mater. Chem. 2008, 18, 4912-4916 (30) Sugimoto, T.; Khan, M. M.; Muramatsu, A.; Itoh, H. Formation Mechanism of Monodisperse Peanut-type α-Fe2O3 Particles from Condensed Ferric Hydroxide Gel. Collids Surfaces A 1993, 79, 233-247. (31) Sugimoto, T.; Khan, M. M.; Muramatsu, A. Preparation of Monodisperse Peanut-type αFe2O3 Particles from Condensed Ferric Hydroxide Gel. Collids Surfaces A 1993, 70, 167-169. (32) Stöber, W.; Fink, A.; Bohn, E. Controlled Growth of Monodisperse Silica Spheres in the Micron Size Range. J. Colloid Interface Sci. 1968, 26, 62-69. (33) Zhang, L. D.; Liu, W. L.; Xu, W. H.; Yao, J. S.; Zhao, L.; Wang, X. Q.; Wu, Y. Z. Synthesis and Characterization of Superhydrophobic and Superparamagnetic Film Based on Maghemite-polystyrene Composite Nanoparticles. Appl. Surf. Sci. 2012, 259, 719-725.


19

Langmuir

1 2 3 4 5 6 7 8 9 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

Page 20 of 28

(34) White, L. D.; Tripp, C. P. Reaction of (3-Aminopropyl)dimethylethoxysilane with Amine Catalysts on Silica Surfaces. J. Colloid Interface Sci. 2000, 232, 400-407.

SYNOPSIS (Word Style “SN_Synopsis_TOC”).


20

Page 21 of 28

1 2 3 4 5 6 7 8 9 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

Langmuir

Scheme 1. Schematic illustration of the shape-controlled synthesis of hollow silica colloids: (i) hematite colloidal particles with different morphologies, (ii) silica shell structures with hematite cores, and (iii) asprepared hollow silica colloids. 78x77mm (300 x 300 DPI)


Langmuir

1 2 3 4 5 6 7 8 9 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

Figure 1. Typical FESEM images of hematite (α-Fe2O3) colloidal particles with different shapes: (a) pseudocubes; (b) ellipsoids; (c) capsules; and (d) peanuts. 80x80mm (300 x 300 DPI)


Page 22 of 28

Page 23 of 28

1 2 3 4 5 6 7 8 9 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

Langmuir

Figure 2. TEM images of differently shaped hematite/silica core/shell particles: (a) pseudocubes; (b) ellipsoids; (c) capsules; and (d) peanuts. 80x80mm (300 x 300 DPI)


Langmuir

1 2 3 4 5 6 7 8 9 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

Figure 3. FESEM and TEM images of hollow silica colloids with different shapes: (a-d) pseudocubes; (e-h) ellipsoids; (i-l) capsules; and (m-p) peanuts. 162x162mm (300 x 300 DPI)


Page 24 of 28

Page 25 of 28

1 2 3 4 5 6 7 8 9 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

Langmuir

Figure 4. EDX point spectra taken from the center point of hollow colloidal particles with different shapes: (a) pseudocube; (b) ellipsoid; (c) capsule; and (d) peanut. The weak Cu and C peaks are attributed to the carbon-coated Cu grid used in TEM. The scale bar of inset in (g) is 500 nm. 135x228mm (300 x 300 DPI)


Langmuir

1 2 3 4 5 6 7 8 9 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

Figure 5. The nitrogen adsorption/desorption isotherm of hollow silica colloids with different shapes and solid particles: (a) solid particles and pseudocubes; (b) ellipsoids; (c) capsules; (d) peanuts. 112x88mm (300 x 300 DPI)


Page 26 of 28

Page 27 of 28

1 2 3 4 5 6 7 8 9 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

Langmuir

Figure 6. FESEM and TEM images of the peanut-shaped hollow silica colloids prepared with different amount of TEOS: (a-c) 0.15 mL; (d-f) 0.3 mL; (g-i) 0.7 mL; (j-l) 0.9 mL; (m-o) 1.2 mL. 97x58mm (300 x 300 DPI)


Langmuir

1 2 3 4 5 6 7 8 9 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

39x39mm (300 x 300 DPI)


Page 28 of 28

Shape-Controlled Synthesis of Hollow Silica Colloids - Langmuir (ACS

Recommend Documents