Synthesis Of Hollow Silica Particles Research Articles

Synthesis of Hollow Silica Particles Using Acid Dissolvable Resorcinol‐Formaldehyde Resin Particles as Template

AbstractHollow silica particles (HSPs) were produced using acid dissolvable resorcinol‐formaldehyde resin (RF) particles as template. Since the RF particles synthesized in alkaline condition were thought to be highly cross‐linked, they were commonly removed by calcination. Apparently, the acid washing method was more facile and time saving. By conducting control experiments, it was proposed that the destruction of the RF template in acid solution was attributed to the large amount of hydrolyzable bonds in their structure. Moreover, Au nanoparticles loaded HSPs were successfully prepared with prefabricated Au nanoparticles as core materials. And thanks to the remained RF in the HSPs, Ag nanoparticles loaded HSPs had also be prepared via an in‐situ reduction route. These results demonstrated the flexibility and effectiveness of our method in synthesizing the hollow and rattle‐type materials.

Design of polymer particles maintaining dispersion stability for the synthesis of hollow silica particles through sol-gel reaction on polymer surfaces

To synthesize polystyrene-silica core-shell particles and silica hollow particles, soap-free emulsion polymerization was carried out using styrene and N-vinylacetamide (NVA), and the Stöber method using tetraethyl orthosilicate (TEOS) was performed on the polymer particle surfaces. Here, NVA acts as a stabilizer for the polymer colloids, maintaining dispersion stability by synthesizing hydration layers even when the electrostatic adsorption of TEOS had occurred, and as a catalyst for the sol-gel reaction. NVA was polymerized by the cationic initiator located on the surface of the polystyrene particles to maintain dispersion stability by a steric effect. Therefore, the sol-gel reactions proceeded more efficiently on the surface of polymer particles, facilitated by the much larger surface area. Finally, the polymer core was removed by heating to prepare highly monodisperse silica hollow particles.

Facile synthesis of hollow silica nanospheres employing anionic PMANa templates

This article presents a facile and green route to the synthesis of hollow silica particles by means of anionic particles of poly(sodium methacrylate) (PMANa) as templates. This method was composed of the following three steps: formation of PMANa particles in ethanol by nanoprecipitation, the deposition of silica shell on the polymer cores through sol–gel process of tetraethylorthosilicate under catalysis of ammonia, and removal of the polymer templates by washing with water. The templates’ size can be controlled in the range of about 70–140 nm by altering the ratio of ethanol to water, the polymer solution concentration, the ethanol amount in polymer solution, and the silica shell thickness can be adjusted between 15 and 30 nm by varying the ratio of silica precursor to the polymer cores. A tentative interpretation about the silica-coating process on the anionic PMANa particles was also proposed according to the experimental results.

Synthesis of hollow silica particles with tunable size, shell thickness, and morphology

We herein present a simple and effective method to control the particle size, shell thickness, and morphology of hollow silica particles (HSPs). To synthesize the HSPs, polystyrene (PS) particles were employed as a sacrificial template. Size tuning of the HSPs could therefore be achieved by using PS particles of varying sizes. The size of the PS particles was easily controlled by modulation of the monomer content used in the particle synthesis. Varying amounts of TEOS and ammonium hydroxide were systematically added to the system in order to modify the shell thickness and morphology of the desired HSPs. The results indicated that the effects of TEOS and ammonium hydroxide concentrations on the HSP shell thicknesses were similar whereas the effects on morphologies differed significantly.

A facile and environmentally friendly method for the synthesis of hollow silica particles in a self-stable dispersion

The fabrication of hollow silica particles is of interest from both academic and application viewpoints. In this paper, we propose a distinctly novel method by which hollow silica particles are successfully fabricated in a self-stable system without any surfactants during a self-consumptive templated process. In detail, it was carried out by adopting a two-step feeding of tetraethoxysilane including initial dropping and subsequent addition of residual TEOS in one batch. The synthesized hollow particles have been extensively characterized using a scanning electron microscope, transmission electron microscope and N2 sorption analysis. The results indicated that the morphology of the resultant hollow silica particles was governed by simply changing the volume ratio of the precursor added in two steps, the reaction temperature and the concentration of ammonia. Additionally, the mechanism governing the formation of the hollow silica particles is discussed.

Synthesis and characterization of hollow silica microspheres functionalized with magnetic particles using W/O emulsion method

Hollow silica particles functionalized with magnetic particles (HSFMs) were prepared without templates using the W/O emulsion system containing magnetic nanoparticles synthesized by the redox reaction of Fe salts. Since the removal process like etching step is not required, our system is a simple and easy method to obtain the functionalized shell and composite hollow materials. Here, the magnetite nanoparticles not only give the hollow silica particles, the magnetic properties but also influence the formation process of the hollow silica microspheres. It is verified by X-ray diffraction (XRD), energy-dispersive X-ray (EDS), and vibrating sample magnetometer (VSM) measurements that the structure and magnetic property of the magnetic particles were not changed in quality before and after the synthesis of hollow silica particles. From the Brunauer, Emmett, Teller (BET - Nitrogen adsorption–desorption measurements) analysis, hollow silica microspheres functionalized by magnetic nanoparticles (HSFMs) reveal the typical Type I isotherm in the IUPAC classification, which shows a long saturation plateau and involves micropore filling. This method can be extended to the synthesis of hollow silica particles functionalized by other metal oxide materials as well as iron oxide.

Fluorinated‐Surfactant‐Templated Synthesis of Hollow Silica Particles with a Single Layer of Mesopores in Their Shells

Fluorinated‐Surfactant‐Templated Synthesis of Hollow Silica Particles with a Single Layer of Mesopores in Their Shells