Article pubs.acs.org/Langmuir
Efficient Immobilization of Colloidal Particles from Aqueous Suspension by Electrostatic Interactions Makoto Ogawa*,†,‡ and Shotaro Kaneko‡ †
Department of Earth Sciences and ‡Graduate School of Creative Science and Engineering, Waseda University, 1-6-1 Nishiwaseda, Shinjuku-ku, Tokyo 169-8050, Japan ABSTRACT: Anionically charged colloidal particles (β-iron oxyhydroxide and smectite clay) were successfully removed from the suspension by the interactions with micrometer-sized hydrotalcite. The efficiency of the removal was evaluated by an examination of concentration-dependent experiments.
(OH)12·mH2O], in this study, hydrotalcite [Mg6Al2(CO3)(OH)16·4H2O]). The electrostatic interactions between oppositely charged particles are expected to play a role in the concentration of nanoparticles from aqueous media. To achieve an efficient collection, large platy particles (a few micrometers) of hydrotalcite (abbreviated as HT; a scanning electron micrograph and a transmission electron micrograph are shown in Figure 1), which were synthesized according to our previous reports,18,19 were used. β-FeOOH gives a stable aqueous suspension, and it precipitates after the addition of HT as shown in the photograph (Figure 2). The amount of β-FeOOH remaining in the aqueous phase is used as the equilibrium concentration, and the amount of β-FeOOH removed from the suspension of HT (similar to the adsorption isotherm) is plotted against the equilibrium concentration as shown in Figure 3. The shape of the relationship is similar to the shape of the Langmuir-type adsorption isotherm, suggesting strong interactions between βFeOOH and HT. Thus, the effective removal of β-FeOOH nanoparticles from aqueous suspension by interaction with HT was achieved. The adsorption is irreversible as shown by the fact that no β-FeOOH was detected in the aqueous phase when the sample (β-FeOOH immobilized on HT) was allowed to react with water. These observations indicate the strong interactions between HT and β-FeOOH. The removal of colloidal β-FeOOH as well as smectite is possible by the addition of Al3+, and the precipitate (composed of β-FeOOH and aluminum hydroxide) is plasterlike or a jelly. The advantage of the present method is the ease of operation: a short precipitation time (a few hours) and easy solid−liquid separation. Thanks to the large particle size of the present HT,
N
anoparticles have attracted increasing interest because of the wide range of applications in catalysts, imaging, optics, electronics, and so forth.1−5 In addition to the size- and shape-controlled synthesis, the immobilization of nanoparticles on or within solid supports has been a topic of interest for such applications as supported catalysts.6−8 As for nanoparticlesupported solids, the size, shape, and distribution of the nanoparticles on or within solid supports are important parameters in determining product performance. There are two available approaches to the preparation of hybrid materials containing nanoparticles: one is based on the in situ formation of nanoparticles on supports, and the other is the immobilization of presynthesized nanoparticles on supports by such means as impregnation. The immobilization of presynthesized nanoparticles has advantages in using the rapid progress of the precise syntheses of nanoparticles. The layer-by-layer assembly of nanoparticles on solid supports, which was used for the preparation of hybrid materials with alternating layered stacks, is a current topic, where a variety of nanoparticles (nanosheets and nanosphere) have been used.9−14 Besides the interest in advanced materials applications mentioned above, the immobilization of nanoparticles on solids is a concern involving general environmental issues.15−17 Nanoparticles in nature (especially those in air and water) are often regarded as contaminants and reservoir of toxic compounds, and their removal is required for environmental remediation. Depending on the nature of environmental nanoparticles (clays, pollen, etc.), various methods (filtration, precipitation, chemically induced aggregation, and so forth) have been used for their removal from the environment. In this article, we report the efficient removal of colloidal particles from their aqueous suspension by electrostatic interactions: the immobilization of negatively charged colloidal particles (β-FeOOH and smectite clay) on a positively charged solid support (a layered double hydroxide [Mg4Al2(CO3)© 2013 American Chemical Society
Received: August 6, 2013 Revised: October 23, 2013 Published: October 31, 2013 14469
dx.doi.org/10.1021/la402390t | Langmuir 2013, 29, 14469−14472
Langmuir
Article
Figure 3. Relationship between the amount of β-FeOOH removed and the concentration of β-FeOOH in the aqueous phase after the experiment.
4a,b, suggesting the possible control of the hybrid structures. At the maximum loading level of β-FeOOH (or at the minimum loading level of HT), the aggregation (interparticle aggregation) of β-FeOOH may be concerned. The hybrid materials composed of iron oxide nanoparticles and solid supports have been prepared and used in such applications as sensors and catalysts.20−24 The preparation of hybrids with controlled hybrid structure by the present method is worth further examination to tune the material performance of the products. To extend the idea to removing other colloidal particles from the aqueous suspension, the immobilization of smectite clay, which is a negatively charged layered silicate, on HT was examined. A synthetic saponite (Sumecton SA, hereafter abbreviated as SSA) was used as a negatively charged colloidal particle. A cationic dye, the ruthenium(II) tris(2,2′-bipyridine) complex, was intercalated in advance to visualize the state of the particles by the naked eye as well as for the simple determination of the amount of SSA by visible absorption spectroscopy. The dye-intercalated SSA was denoted as RuSSA. Figure 5 shows the photograph where orange colloidal particles of Ru-SSA were precipitated when HT was mixed into the aqueous suspension. The amount of immobilized Ru-SSA was ca. 0.01 g/g of HT. The concept was applied to collect a positively charged colloidal particle with a negatively charged solid support. A nanometer-sized HT particle, which was prepared according to the method reported previously, 25,26 was collected by interactions with a layered silicate, octosilicate, which is a
Figure 1. (a) Scanning electron micrograph and (b) transmission electron micrograph of HT.
the separation of solids from the aqueous phase was facile by simple sedimentation and/or centrifugation. The capacity of HT for the uptake of β-FeOOH was estimated from Figure 3 to be ca. 6 g/g of HT. This value is quite large, which is an important aspect of the present method of removing β-FeOOH particles from the environment. Transmission electron micrographs of the collected HT after the removal of β-FeOOH are shown in Figure 4, where the HT particle retained its original platy particle shape and needleshaped β-FeOOH particles were attached to the surface of HT. The population of β-FeOOH on HT depends on the amount of immobilized β-FeOOH as shown by the difference in Figure
Figure 2. β-FeOOH precipitation after the addition of HT. The photograph was taken after the sample stood for 7 h. 14470
dx.doi.org/10.1021/la402390t | Langmuir 2013, 29, 14469−14472
Langmuir
Article
composition depending on the relative amount of support and the number of colloidal particles.
■
EXPERIMENTAL SECTION
■
AUTHOR INFORMATION
Large platy particles of HT were synthesized according to our previous reports on the preparation of layered double hydroxides by means of urea hydrolysis under hydrothermal conditions.18,19 The formation of HT with well-defined structure and particle morphology (micrometersized hexagonal plates) was confirmed by XRD, IR, TG-DTA, and SEM. An aqueous β-FeOOH suspension was prepared by the method described previously.30,31 The suspension was diluted with deionized water to the desired concentration (90 mg/L), and the pH was adjusted to 11.5 by the addition of NaOH. After HT was mixed into the aqueous β-FeOOH suspension by shaking and ultrasonication for 30 min, the suspension was allowed to stand for 48 h. Then the amount of precipitated β-FeOOH was determined by subtracting the residual amount of β-FeOOH in the aqueous phase from the original amount of β-FeOOH. The amount of added HT was 1 to 1000 mg for 100 mL of an aqueous β-FeOOH suspension. X-ray powder diffraction (XRD) patterns of the products were recorded on a Rigaku RAD IB powder diffractometer equipped with monochromatic Cu Kα radiation operated at 20 mA and 40 kV. Scanning electron micrographs (SEM) of the Au-coated samples were obtained using a Hitachi S-2380N scanning electron microscope. Prior to the measurements, the samples were coated with a 20 nm gold layer. Transmission electron micrographs (TEM) were taken on a JEOL JEM1011 transmission electron microscope with an acceleration voltage of 100 kV. UV−vis absorption spectra were recorded on a Shimadzu UV-3100PC spectrometer using deionized water as a reference. Figure 4. Transmission electron micrographs of FeOOH on HT: (a) 4.5 mg of β-FeOOH on 5 mg of HT and (b) 4.5 mg of β-FeOOH on 1000 mg of HT.
Corresponding Author
*E-mail: [email protected]. Fax: (+81) 3-5286-1511. Tel: (+81) 3-5286-1511.
layered sodium silicate with micrometer-sized platy particles.27−29 In summary, the immobilization of charged colloidal particles with oppositely charged particles via electrostatic interactions is shown using negatively charged particles (β-FeOOH and smectite clay) and positively charged solid supports (hydrotalcite). Thanks to the large particle size of the present HT, the separation of solids from the aqueous phase was facile by simple sedimentation and/or centrifugation. These facts suggest the possible removal of colloidal particles from the environment. Furthermore, the method is applicable to the preparation of hybrid particles with the desired structure and
Notes
The authors declare no competing financial interest.
■ ■
ACKNOWLEDGMENTS Waseda University supported us financially as a special research project (2011A-604). REFERENCES
(1) Rosi, N. L.; Mirkin, C. Nanostructures in Biodiagnostics. Chem. Rev. 2005, 105, 1547−1562.
Figure 5. Photographs of Ru-SSA precipitation after the addition of HT. The photograph was taken after the aqueous mixture stood for 20 h. 14471
dx.doi.org/10.1021/la402390t | Langmuir 2013, 29, 14469−14472
Langmuir
Article
(2) Shipway, A. N.; Katz, E.; Willner, I. Nanoparticle Arrays on Surfaces for Electronic, Optical, and Sensor Applications. ChemPhysChem 2000, 1, 18−52. (3) Haynes, C. L.; Van. Duyne, R. P. Nanosphere Lithography: A Versatile Nanofabrication Tool for Studies of Size-Dependent Nanoparticle Optics. J. Phys. Chem. B 2001, 105, 5599−5611. (4) Loo, C.; Lowery, A.; Halas, N.; West, J.; Drezek, R. Immunotargeted Nanoshells for Integrated Cancer Imaging and Therapy. Nano Lett. 2005, 5, 709−711. (5) Toshima, N.; Yonezawa, T. Bimetallic NanoparticlesNovel Materials for Chemical and Physical Applications. New J. Chem. 1998, 1179−1201. (6) Aranda, P.; Kun, R.; Martín-luengo, M. A.; Letaïef, S.; Dékány, I.; Ruiz-Hitzky, E. Titania-Sepiolite Nanocomposites Prepared by a Surfactant Templating Colloidal Route. Chem. Mater. 2008, 20, 84− 91. (7) Li, L.; Feng, Y.; Li, Y.; Zhao, W.; Shi, J. Fe3O4 Core/Layered Double Hydroxide Shell Nanocomposite: Versatile Magnetic Matrix for Anionic Functional Materials. Angew. Chem., Int. Ed. 2009, 48, 5888−5892. (8) Xu, Y.; Zhang, H.; Duan, X.; Ding, Y. Preparation and Investigation on a Novel Nanostructured Magnetic Base Catalyst MgAl−OH-LDH/CoFe2O4. Mater. Chem. Phys. 2009, 114, 795−801. (9) Caruso, R.; Susha, A.; Caruso, F. Multilayered Titania, Silica, And Laponite Nanoparticle Coatings on Polystyrene Colloidal Templates and Resulting Inorganic Hollow Spheres. Chem. Mater. 2001, 13, 400− 409. (10) Ariga, K.; Ji, Q.; Hill, J. P.; Bando, Y.; Aono, M. Forming Nanomaterials As Layered Functional Structures toward Materials Nanoarchitectonics. NPG Asia Mater. 2012, 4, e17. (11) Sengupta, A.; Sarkar, C. K. Analytical Modeling of Si and Au Nanocrystal Embedded Multilayer Gate Dielectric Long Channel Gate All Around (GAA) MOSFET Non Volatile Memory Devices. Nanosci. Nanotechnol. Lett. 2012, 4, 667−675. (12) Liu, X.; Ma, R.; Bando, Y.; Sasaki, T. A General Strategy to Layered Transition-Metal Hydroxide Nanocones: Tuning the Composition for High Electrochemical Performance. Adv. Mater. 2012, 24, 2148−2153. (13) Wang, J.; Cheng, Q.; Tang, Z. Layered Nanocomposites Inspired by the Structure and Mechanical Properties of Nacre. Chem. Soc. Rev. 2012, 41, 1111−1129. (14) Wang, Q.; O’Hare, D. Recent Advances in the Synthesis and Application of Layered Double Hydroxide (LDH) Nanosheets. Chem. Rev. 2012, 112, 4124−4155. (15) Bradford, S.; Simunek, J.; Bettahar, M.; Van. Genuchten, M. T.; Yates, S. R. Modeling Colloid Attachment, Straining, and Exclusion in Saturated Porous Media. Environ. Sci. Technol. 2003, 37, 2242−2245. (16) Sauer, J. E.; Davis, E. J. Electrokinetically enhanced Sedimentation of Colloidal Contaminants. Environ. Sci. Technol. 1994, 28, 737−745. (17) Zevi, Y.; Dathe, A.; McCarthy, J. F.; Richards, B. K.; Steenhuis, T. S. Distribution of Colloid Particles onto Interfaces in Partially Saturated Sand. Environ. Sci. Technol. 2005, 39, 7055−7064. (18) Ogawa, M.; Kaiho, H. Homogeneous Precipitation of Uniform Hydrotalcite Particles. Langmuir 2002, 18, 4240−4242. (19) Kayano, M.; Ogawa, M. Preparation of Large Platy Particles of Co-Al Layered Double Hydroxides. Clays Clay Miner. 2006, 54, 382− 389. (20) Esteban-Cubillo, A.; Tulliani, J.-M.; Pecharromán, C.; Moya, J. S. Iron-Oxide Nanoparticles Supported on Sepiolite As a Novel Humidity Sensor. J. Eur. Ceram. Soc. 2007, 27, 1983−1989. (21) Choi, H. C.; Kundaria, S.; Wang, D.; Javey, A.; Wang, Q.; Rolandi, M.; Hongjie, D. Efficient Formation of Iron Nanoparticle Catalysts on Silicon Oxide by Hydroxylamine for Carbon Nanotube Synthesis and Electronics. Nano Lett. 2003, 3, 157−161. (22) Wu, X.-L.; Wang, L.; Chen, C.-L.; Xu, A.-W.; Wang, X.-K. Water-Dispersible Magnetite-Graphene-LDH Composites for Efficient Arsenate Removal. J. Mater. Chem. 2011, 21, 17353−17359.
(23) González-Alfaro, Y.; Aranda, P.; Fernandes, F. M.; Wicklein, B.; Darder, M.; Ruiz-Hitzky, E. Multifunctional Porous Materials through Ferrofluids. Adv. Mater. 2011, 23, 5224−5228. (24) Chen, C.; Gunawan, P.; Xu, R. Self-Assembled Fe3O4-Layered Double Hydroxide Colloidal Nanohybrids with Excellent Performance for Treatment of Organic Dyes in Water. J. Mater. Chem. 2011, 21, 1218−1225. (25) Nitoh, K.; Ayral, A.; Ogawa, M. Preparation of Well-Defined Nanometer-Sized Layered Double Hydroxides by Novel pH Adjustment Method Using Ion-Exchange Resin. Chem. Lett. 2010, 39, 1018− 1019. (26) Naito, S.; Nitoh, K.; Ayral, A.; Ogawa, M. Preparation of Finite Particles of Nitrate Forms of Layered Double Hydroxides by pH Adjustment with Anion Exchange Resin. Ind. Eng. Chem. Res. 2012, 51, 14414−14418. (27) Iler, R. K. Ion Exchange Properties of a Crystalline Hydrated Silica. J. Colloid Sci. 1964, 19, 648−657. (28) Endo, K.; Sugawara, Y.; Kuroda, K. Formation of Intercalation Compounds of a Layered Sodium Octosilicate with n-Alkyltrimethylammonium Ions and the Application to Organic Derivatization. Bull. Chem. Soc. Jpn. 1994, 67, 3352−3355. (29) Ogawa, M.; Iwata, D. Arrangements of Interlayer Quaternary Ammonium Ions in a Layered Silicate, Octosilicate. Cryst. Growth Des. 2010, 10, 2068−2072. (30) Sugimoto, T.; Khan, M. M.; Muramatsu, A. Preparation of Monodisperse Peanut-Type α-Fe2O3 Particles from Condensed Ferric Hydroxide Gel. Colloids Surf., A 1993, 70, 167−169. (31) Nakade, M.; Ikeda, T.; Ogawa, M. Synthesis and Properties of Ellipsoidal Hematite/Silicone Core-Shell Particles. J. Mater. Sci. 2007, 42, 4815−4823.
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dx.doi.org/10.1021/la402390t | Langmuir 2013, 29, 14469−14472
Efficient Immobilization of Colloidal Particles from Aqueous Suspension by Electrostatic Interactions Makoto Ogawa*,†,‡ and Shotaro Kaneko‡ †
Department of Earth Sciences and ‡Graduate School of Creative Science and Engineering, Waseda University, 1-6-1 Nishiwaseda, Shinjuku-ku, Tokyo 169-8050, Japan ABSTRACT: Anionically charged colloidal particles (β-iron oxyhydroxide and smectite clay) were successfully removed from the suspension by the interactions with micrometer-sized hydrotalcite. The efficiency of the removal was evaluated by an examination of concentration-dependent experiments.
(OH)12·mH2O], in this study, hydrotalcite [Mg6Al2(CO3)(OH)16·4H2O]). The electrostatic interactions between oppositely charged particles are expected to play a role in the concentration of nanoparticles from aqueous media. To achieve an efficient collection, large platy particles (a few micrometers) of hydrotalcite (abbreviated as HT; a scanning electron micrograph and a transmission electron micrograph are shown in Figure 1), which were synthesized according to our previous reports,18,19 were used. β-FeOOH gives a stable aqueous suspension, and it precipitates after the addition of HT as shown in the photograph (Figure 2). The amount of β-FeOOH remaining in the aqueous phase is used as the equilibrium concentration, and the amount of β-FeOOH removed from the suspension of HT (similar to the adsorption isotherm) is plotted against the equilibrium concentration as shown in Figure 3. The shape of the relationship is similar to the shape of the Langmuir-type adsorption isotherm, suggesting strong interactions between βFeOOH and HT. Thus, the effective removal of β-FeOOH nanoparticles from aqueous suspension by interaction with HT was achieved. The adsorption is irreversible as shown by the fact that no β-FeOOH was detected in the aqueous phase when the sample (β-FeOOH immobilized on HT) was allowed to react with water. These observations indicate the strong interactions between HT and β-FeOOH. The removal of colloidal β-FeOOH as well as smectite is possible by the addition of Al3+, and the precipitate (composed of β-FeOOH and aluminum hydroxide) is plasterlike or a jelly. The advantage of the present method is the ease of operation: a short precipitation time (a few hours) and easy solid−liquid separation. Thanks to the large particle size of the present HT,
N
anoparticles have attracted increasing interest because of the wide range of applications in catalysts, imaging, optics, electronics, and so forth.1−5 In addition to the size- and shape-controlled synthesis, the immobilization of nanoparticles on or within solid supports has been a topic of interest for such applications as supported catalysts.6−8 As for nanoparticlesupported solids, the size, shape, and distribution of the nanoparticles on or within solid supports are important parameters in determining product performance. There are two available approaches to the preparation of hybrid materials containing nanoparticles: one is based on the in situ formation of nanoparticles on supports, and the other is the immobilization of presynthesized nanoparticles on supports by such means as impregnation. The immobilization of presynthesized nanoparticles has advantages in using the rapid progress of the precise syntheses of nanoparticles. The layer-by-layer assembly of nanoparticles on solid supports, which was used for the preparation of hybrid materials with alternating layered stacks, is a current topic, where a variety of nanoparticles (nanosheets and nanosphere) have been used.9−14 Besides the interest in advanced materials applications mentioned above, the immobilization of nanoparticles on solids is a concern involving general environmental issues.15−17 Nanoparticles in nature (especially those in air and water) are often regarded as contaminants and reservoir of toxic compounds, and their removal is required for environmental remediation. Depending on the nature of environmental nanoparticles (clays, pollen, etc.), various methods (filtration, precipitation, chemically induced aggregation, and so forth) have been used for their removal from the environment. In this article, we report the efficient removal of colloidal particles from their aqueous suspension by electrostatic interactions: the immobilization of negatively charged colloidal particles (β-FeOOH and smectite clay) on a positively charged solid support (a layered double hydroxide [Mg4Al2(CO3)© 2013 American Chemical Society
Received: August 6, 2013 Revised: October 23, 2013 Published: October 31, 2013 14469
dx.doi.org/10.1021/la402390t | Langmuir 2013, 29, 14469−14472
Langmuir
Article
Figure 3. Relationship between the amount of β-FeOOH removed and the concentration of β-FeOOH in the aqueous phase after the experiment.
4a,b, suggesting the possible control of the hybrid structures. At the maximum loading level of β-FeOOH (or at the minimum loading level of HT), the aggregation (interparticle aggregation) of β-FeOOH may be concerned. The hybrid materials composed of iron oxide nanoparticles and solid supports have been prepared and used in such applications as sensors and catalysts.20−24 The preparation of hybrids with controlled hybrid structure by the present method is worth further examination to tune the material performance of the products. To extend the idea to removing other colloidal particles from the aqueous suspension, the immobilization of smectite clay, which is a negatively charged layered silicate, on HT was examined. A synthetic saponite (Sumecton SA, hereafter abbreviated as SSA) was used as a negatively charged colloidal particle. A cationic dye, the ruthenium(II) tris(2,2′-bipyridine) complex, was intercalated in advance to visualize the state of the particles by the naked eye as well as for the simple determination of the amount of SSA by visible absorption spectroscopy. The dye-intercalated SSA was denoted as RuSSA. Figure 5 shows the photograph where orange colloidal particles of Ru-SSA were precipitated when HT was mixed into the aqueous suspension. The amount of immobilized Ru-SSA was ca. 0.01 g/g of HT. The concept was applied to collect a positively charged colloidal particle with a negatively charged solid support. A nanometer-sized HT particle, which was prepared according to the method reported previously, 25,26 was collected by interactions with a layered silicate, octosilicate, which is a
Figure 1. (a) Scanning electron micrograph and (b) transmission electron micrograph of HT.
the separation of solids from the aqueous phase was facile by simple sedimentation and/or centrifugation. The capacity of HT for the uptake of β-FeOOH was estimated from Figure 3 to be ca. 6 g/g of HT. This value is quite large, which is an important aspect of the present method of removing β-FeOOH particles from the environment. Transmission electron micrographs of the collected HT after the removal of β-FeOOH are shown in Figure 4, where the HT particle retained its original platy particle shape and needleshaped β-FeOOH particles were attached to the surface of HT. The population of β-FeOOH on HT depends on the amount of immobilized β-FeOOH as shown by the difference in Figure
Figure 2. β-FeOOH precipitation after the addition of HT. The photograph was taken after the sample stood for 7 h. 14470
dx.doi.org/10.1021/la402390t | Langmuir 2013, 29, 14469−14472
Langmuir
Article
composition depending on the relative amount of support and the number of colloidal particles.
■
EXPERIMENTAL SECTION
■
AUTHOR INFORMATION
Large platy particles of HT were synthesized according to our previous reports on the preparation of layered double hydroxides by means of urea hydrolysis under hydrothermal conditions.18,19 The formation of HT with well-defined structure and particle morphology (micrometersized hexagonal plates) was confirmed by XRD, IR, TG-DTA, and SEM. An aqueous β-FeOOH suspension was prepared by the method described previously.30,31 The suspension was diluted with deionized water to the desired concentration (90 mg/L), and the pH was adjusted to 11.5 by the addition of NaOH. After HT was mixed into the aqueous β-FeOOH suspension by shaking and ultrasonication for 30 min, the suspension was allowed to stand for 48 h. Then the amount of precipitated β-FeOOH was determined by subtracting the residual amount of β-FeOOH in the aqueous phase from the original amount of β-FeOOH. The amount of added HT was 1 to 1000 mg for 100 mL of an aqueous β-FeOOH suspension. X-ray powder diffraction (XRD) patterns of the products were recorded on a Rigaku RAD IB powder diffractometer equipped with monochromatic Cu Kα radiation operated at 20 mA and 40 kV. Scanning electron micrographs (SEM) of the Au-coated samples were obtained using a Hitachi S-2380N scanning electron microscope. Prior to the measurements, the samples were coated with a 20 nm gold layer. Transmission electron micrographs (TEM) were taken on a JEOL JEM1011 transmission electron microscope with an acceleration voltage of 100 kV. UV−vis absorption spectra were recorded on a Shimadzu UV-3100PC spectrometer using deionized water as a reference. Figure 4. Transmission electron micrographs of FeOOH on HT: (a) 4.5 mg of β-FeOOH on 5 mg of HT and (b) 4.5 mg of β-FeOOH on 1000 mg of HT.
Corresponding Author
*E-mail: [email protected]. Fax: (+81) 3-5286-1511. Tel: (+81) 3-5286-1511.
layered sodium silicate with micrometer-sized platy particles.27−29 In summary, the immobilization of charged colloidal particles with oppositely charged particles via electrostatic interactions is shown using negatively charged particles (β-FeOOH and smectite clay) and positively charged solid supports (hydrotalcite). Thanks to the large particle size of the present HT, the separation of solids from the aqueous phase was facile by simple sedimentation and/or centrifugation. These facts suggest the possible removal of colloidal particles from the environment. Furthermore, the method is applicable to the preparation of hybrid particles with the desired structure and
Notes
The authors declare no competing financial interest.
■ ■
ACKNOWLEDGMENTS Waseda University supported us financially as a special research project (2011A-604). REFERENCES
(1) Rosi, N. L.; Mirkin, C. Nanostructures in Biodiagnostics. Chem. Rev. 2005, 105, 1547−1562.
Figure 5. Photographs of Ru-SSA precipitation after the addition of HT. The photograph was taken after the aqueous mixture stood for 20 h. 14471
dx.doi.org/10.1021/la402390t | Langmuir 2013, 29, 14469−14472
Langmuir
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(2) Shipway, A. N.; Katz, E.; Willner, I. Nanoparticle Arrays on Surfaces for Electronic, Optical, and Sensor Applications. ChemPhysChem 2000, 1, 18−52. (3) Haynes, C. L.; Van. Duyne, R. P. Nanosphere Lithography: A Versatile Nanofabrication Tool for Studies of Size-Dependent Nanoparticle Optics. J. Phys. Chem. B 2001, 105, 5599−5611. (4) Loo, C.; Lowery, A.; Halas, N.; West, J.; Drezek, R. Immunotargeted Nanoshells for Integrated Cancer Imaging and Therapy. Nano Lett. 2005, 5, 709−711. (5) Toshima, N.; Yonezawa, T. Bimetallic NanoparticlesNovel Materials for Chemical and Physical Applications. New J. Chem. 1998, 1179−1201. (6) Aranda, P.; Kun, R.; Martín-luengo, M. A.; Letaïef, S.; Dékány, I.; Ruiz-Hitzky, E. Titania-Sepiolite Nanocomposites Prepared by a Surfactant Templating Colloidal Route. Chem. Mater. 2008, 20, 84− 91. (7) Li, L.; Feng, Y.; Li, Y.; Zhao, W.; Shi, J. Fe3O4 Core/Layered Double Hydroxide Shell Nanocomposite: Versatile Magnetic Matrix for Anionic Functional Materials. Angew. Chem., Int. Ed. 2009, 48, 5888−5892. (8) Xu, Y.; Zhang, H.; Duan, X.; Ding, Y. Preparation and Investigation on a Novel Nanostructured Magnetic Base Catalyst MgAl−OH-LDH/CoFe2O4. Mater. Chem. Phys. 2009, 114, 795−801. (9) Caruso, R.; Susha, A.; Caruso, F. Multilayered Titania, Silica, And Laponite Nanoparticle Coatings on Polystyrene Colloidal Templates and Resulting Inorganic Hollow Spheres. Chem. Mater. 2001, 13, 400− 409. (10) Ariga, K.; Ji, Q.; Hill, J. P.; Bando, Y.; Aono, M. Forming Nanomaterials As Layered Functional Structures toward Materials Nanoarchitectonics. NPG Asia Mater. 2012, 4, e17. (11) Sengupta, A.; Sarkar, C. K. Analytical Modeling of Si and Au Nanocrystal Embedded Multilayer Gate Dielectric Long Channel Gate All Around (GAA) MOSFET Non Volatile Memory Devices. Nanosci. Nanotechnol. Lett. 2012, 4, 667−675. (12) Liu, X.; Ma, R.; Bando, Y.; Sasaki, T. A General Strategy to Layered Transition-Metal Hydroxide Nanocones: Tuning the Composition for High Electrochemical Performance. Adv. Mater. 2012, 24, 2148−2153. (13) Wang, J.; Cheng, Q.; Tang, Z. Layered Nanocomposites Inspired by the Structure and Mechanical Properties of Nacre. Chem. Soc. Rev. 2012, 41, 1111−1129. (14) Wang, Q.; O’Hare, D. Recent Advances in the Synthesis and Application of Layered Double Hydroxide (LDH) Nanosheets. Chem. Rev. 2012, 112, 4124−4155. (15) Bradford, S.; Simunek, J.; Bettahar, M.; Van. Genuchten, M. T.; Yates, S. R. Modeling Colloid Attachment, Straining, and Exclusion in Saturated Porous Media. Environ. Sci. Technol. 2003, 37, 2242−2245. (16) Sauer, J. E.; Davis, E. J. Electrokinetically enhanced Sedimentation of Colloidal Contaminants. Environ. Sci. Technol. 1994, 28, 737−745. (17) Zevi, Y.; Dathe, A.; McCarthy, J. F.; Richards, B. K.; Steenhuis, T. S. Distribution of Colloid Particles onto Interfaces in Partially Saturated Sand. Environ. Sci. Technol. 2005, 39, 7055−7064. (18) Ogawa, M.; Kaiho, H. Homogeneous Precipitation of Uniform Hydrotalcite Particles. Langmuir 2002, 18, 4240−4242. (19) Kayano, M.; Ogawa, M. Preparation of Large Platy Particles of Co-Al Layered Double Hydroxides. Clays Clay Miner. 2006, 54, 382− 389. (20) Esteban-Cubillo, A.; Tulliani, J.-M.; Pecharromán, C.; Moya, J. S. Iron-Oxide Nanoparticles Supported on Sepiolite As a Novel Humidity Sensor. J. Eur. Ceram. Soc. 2007, 27, 1983−1989. (21) Choi, H. C.; Kundaria, S.; Wang, D.; Javey, A.; Wang, Q.; Rolandi, M.; Hongjie, D. Efficient Formation of Iron Nanoparticle Catalysts on Silicon Oxide by Hydroxylamine for Carbon Nanotube Synthesis and Electronics. Nano Lett. 2003, 3, 157−161. (22) Wu, X.-L.; Wang, L.; Chen, C.-L.; Xu, A.-W.; Wang, X.-K. Water-Dispersible Magnetite-Graphene-LDH Composites for Efficient Arsenate Removal. J. Mater. Chem. 2011, 21, 17353−17359.
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dx.doi.org/10.1021/la402390t | Langmuir 2013, 29, 14469−14472
