Hematite template route to hollow-type silica spheres

Han, Yang‐Su; Jeong, Gee-Young; Lee, Sun-Young; Kim, Ho-Kun

doi:10.1016/j.jssc.2007.08.016

Cited by 14 publications

(7 citation statements)

References 48 publications

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“…Even if the hematite cores are changed into Fe 3 O 4 ferromagnetic nanoparticles, the uniform silica coating still effectively prevents them from aggregating due to magnetic attraction and allows them to be easily dispersed in water or ethanol (Supporting Information, Figure S1). Compared with the previous silica coating routes, ,,− the coating method reported here offers many advantages. (1) In our WPN system, the hydrolysis reaction of TEOS is kept slow and confined around the core surface due to the “bound” water, and the formation of new nuclei is suppressed.…”

Section: Resultsmentioning

confidence: 99%

“…A variety of routes such as microemulsion, molecular templating, and modified stöber methods ,,− have been developed to coat iron oxide with silica for high stability, drug delivery, multiphase separation, and possible photonic crystal with magnetically controlled bandgap. However, these methods are limited by aggregations, deformed spherical shape, polydispersity, and additional surface modification processes used to suppress the formation of new nuclei.…”

Section: Introductionmentioning

confidence: 99%

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Highly Shape-Selective Synthesis, Silica Coating, Self-Assembly, and Magnetic Hydrogen Sensing of Hematite Nanoparticles

et al. 2009

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The open forced hydrolysis method and controllable silica growth based on bound water to polyvinylpyrrolidone molecules have been developed for the highly shape (including rhombohedra, semispheres, and rods) selective synthesis, self-assembly, and uniform silica coating (in the unprecedented range of 5-200 nm) of hematite nanoparticles. The open system realizes the direct short-range self-assembly of hematite semispheres in their growth process. The bound water method has been extended to coat gold nanoparticles with tunable silica shell and directly assemble the cores into one-dimensional, dimer, and trimer nanostructures during the coating process. The silica coating increases the particle stability and monodispersity even as hematite is modified into ferromagnetic Fe(3)O(4). The hematite@silica core-shell spheres are assembled into long-range ordered structures with considerable photonic bandgap for the first time due to their high monodispersity. By exploiting the hematite antiferromagnetism caused by the superexchange interaction via intervening oxygen ions that are sensitive to hydrogen, a novel hydrogen sensing based on magnetization variations is achieved in the hematite assemblies. Weakening the antiferromagnetism by reducing the hematite size and/or covering the hematite surface by silica coating suppresses the sensitivity to hydrogen, showing that the antiferromagnetic spin variations on the hematite surface are responsible for the gas sensing.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Highly Shape-Selective Synthesis, Silica Coating, Self-Assembly, and Magnetic Hydrogen Sensing of Hematite Nanoparticles

et al. 2009

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“…Our as-synthesized Fe 2 O 3 @SiO 2 nanoparticles could serve as a template to derive hollow spheres with mesoporous shells (HSMS) by removal of the core particle via an acid leaching process. These hollow materials may find applications in drug delivery, cosmetics, detergents, nanocatalysis, and specific recognition systems. , Compared to conventional methods, − our synthesis produced more uniform hollow SiO 2 spheres with tunable shell thickness. Size tunability in the <100 nm range would be of importance in biomedical applications, such as in drug delivery systems to control drug release rates and durations.…”

Section: Resultsmentioning

confidence: 94%

Controlled Fabrication of Iron Oxide/Mesoporous Silica Core–Shell Nanostructures

et al. 2013

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In this study, a simple and reproducible method for the preparation of well-defined iron oxides/mesoporous silica core-shell nanostructure was provided. Iron oxide nanocubes with a narrow size distribution were synthesized through a novel ethanol/acetic acid system using Fe(NO 3 )•9H 2 O as an iron source and polyvinylpyrrolidone (PVP) as a capping agent under mild solvothermal conditions (200 o C).These monodisperse nanoparticles were directly used as core for the deposition of a mesoporous silica shell via a sol-gel process, resulting in uniform core-shell Fe 2 O 3 @SiO 2 composites with tailored silica shell thickness and controllable core morphology. In addition, composition as well as magnetization of the reduced core-shell composites could be easily controlled by reduction process. Furthermore, the iron oxide core in Fe 2 O 3 @SiO 2 could be completely etched to produce hollow SiO 2 nanospheres. The mechanism of formation of core-shell structure was also proposed by the aid of IR spectrum analysis.

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“…Recently, silica hollow spheres have been fabricated by microemulsion templating method . Likewise, hard templates (e. g. CaCO 3, hematite, Fe 3 O 4 , polystyrene) have been utilized in the fabrication of hollow silica micro‐ /nanoparticles . Despite the previous contributions, the sacrificial templates are still costly and the production procedures are complex.…”

Section: Introductionmentioning

confidence: 99%

Approachable Way to Synthesize 3D Silica Hollow Nanospheres with Mesoporous Shells via Simple Template‐Assisted Technique

Abdelaal

Harbrecht

2016

ChemistrySelect

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3D porous silica hollow nanospheres (PSHNSs) with mesoporous walls have been successfully fabricated by simple template-assisted method using tetraethoxysilan (TEOS) as a silica precursor and glucose-derived functionalized carbon spheres (FCSs) as hard templates. Template-precursor hybrid composite spheres were formed by direct adsorption of the silica precursor onto the surface layers of the FCSs. After etching of the template via oxidation in air, free standing 3D PSHNSs were obtained. The resulting PSHNSs were~85 nm in size as indicated by both SEM and TEM images. BET analysis has shown that nanospheres to have a large specific surface area up to 400 m 2 /g. The fascinating structure of 3D PSHNSs may provide more accessibility and good contacts with reactants that is very important in the fields of catalysts, gas adsorbent, heavy metals removal, electronics, and so on.[a] Dr.

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Hematite template route to hollow-type silica spheres

Cited by 14 publications

References 48 publications

Highly Shape-Selective Synthesis, Silica Coating, Self-Assembly, and Magnetic Hydrogen Sensing of Hematite Nanoparticles

Highly Shape-Selective Synthesis, Silica Coating, Self-Assembly, and Magnetic Hydrogen Sensing of Hematite Nanoparticles

Controlled Fabrication of Iron Oxide/Mesoporous Silica Core–Shell Nanostructures

Approachable Way to Synthesize 3D Silica Hollow Nanospheres with Mesoporous Shells via Simple Template‐Assisted Technique

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