Encapsulation of multiple large spherical silica nanoparticles in hollow spherical silica shells

Guo, Yu‐Guo; Davidson, Rob; Peck, Kristin A.; Guo, Ting

doi:10.1016/j.jcis.2014.12.055

Cited by 5 publications

(7 citation statements)

References 24 publications

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“…), which faces a great challenge in evaporation flux control. , The hard template-based techniques involve the etching of the template, which entails special physical/chemical post-treatments for template removal (strong acid etchant, thermal annealing, calcination, etc. ), separate synthesis of the template, and extra processing steps. ,, The microfluidics technique needs expensive special equipment, and a limited particle diameter is obtained (∼10 μm) . The freeze-drying technique necessitates a suspension temperature around −210 °C (using liquid N 2 ), and the frozen sample needs to be gradually warmed with a rate of 30 °C/h to tailor various microstructures.…”

Section: Introductionmentioning

confidence: 99%

“…The post-treatment conditions (i.e., hydrothermal temperature or low pressure) resulted in various microcapsule shapes (i.e., minitablet, hemisphere, bowl, monoporous spheres, etc.). Utilizing PS particles as a hard template, Guo et al 22 fabricated microsized, raspberry-like hollow silica capsules. To form hollow silica capsules, a hard template was removed through calcination and various etchant (hydrofluoric acid, tetrahydrofuran, sodium hydroxide solution, toluene, etc.)…”

Section: ■ Introductionmentioning

confidence: 99%

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Complex Polymeric Microstructures with Programmable Architecture via Pickering Emulsion-Templated In Situ Polymerization

Parvate

Chattopadhyay

2022

Langmuir

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Aside from smooth and spherical microcapsules, the concept of tailoring complex polymeric microstructures is being taken a step ahead due to their great demand in various applications and fundamental studies in the subjects of microfluidics and nanotechnology. Size, shape, and morphology are of paramount importance for their functional performance and various applications. However, simple, inexpensive, versatile, and high-throughput techniques for fabricating microcapsules with controlled morphology remain a bottleneck for discoveries in the subject of polymer colloids. In this paper, we directly fulfill this need by reporting a novel approach of Pickering emulsion-templated in situ polymerization for tailoring complex polymeric microstructures comprised of a composite shell of titanium dioxide nanoparticle (TiO2 NP)-embedded poly(melamine-urea-formaldehyde) (polyMUF) and a core of hexadecane (HD, soft template). At first, we hydrophobize TiO2 NPs by chemisorbing long-chain biobased myristic acid via a bidentate chelating complex and precisely tune their wettability by varying the grafting density of myristic acid to obtain highly stable oil-in-water (O/W) Pickering emulsion. Thereafter, we employ the optimized TiO2 NPs in the intended encapsulation strategy that enables various microstructures and morphologies with the particle diameter ranging from 5 to 20 μm. Careful manipulation of reaction parameters and copolymer components leads to novel complex microstructures: smooth, raspberry-like, partially budded, hollow, filled, single-holed, and closed-cell-like microstructures. Particle properties such as morphology, size, shell thickness, and core content are governed by the TiO2 NP content, core-to-shell ratio, copolymer component, conversion, and pH value. Based on the results of a series of control experiments, novel mechanisms for the formation of various such microstructures are proposed.

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Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Complex Polymeric Microstructures with Programmable Architecture via Pickering Emulsion-Templated In Situ Polymerization

Parvate

Chattopadhyay

2022

Langmuir

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“…Due to availability and the relatively low price of substrates, as well as simplicity and short time of synthesis, polymer templates are often selected as structure-directing agents to obtain core-shell composites by the bottom-up approach [14,15]. Oxide layers, e.g., SiO 2 , TiO 2 , ZrO 2 or CeO 2 , are deposited onto the polymer cores, and then the organic interior is easily removed by calcination or chemical etching with acidic, alkaline or organic agents [16][17][18][19][20]. In the synthesis of such core-shell systems, among other things, heterophase polymerization (leading to encapsulation of inorganic nanoparticles), sol-gel processes (leading to coating polymer colloids with an inorganic layer) and layer-by-layer deposition are used.…”

Section: Introductionmentioning

confidence: 99%

“…In the synthesis of such core-shell systems, among other things, heterophase polymerization (leading to encapsulation of inorganic nanoparticles), sol-gel processes (leading to coating polymer colloids with an inorganic layer) and layer-by-layer deposition are used. Regardless of the choice of the synthesis method, it is necessary to facilitate interaction between a polymer and an inorganic component [18,[20][21][22].…”

Section: Introductionmentioning

confidence: 99%

“…The process often takes place in an o/w (oil in water) emulsion in which monomer droplets are dispersed in water by surfactants. Other types of polymerization, such as so-called reverse w/o emulsion (water in oil) as well as w/o/w and o/w/o microemulsion, are rarely chosen [14,16,20]. The mechanism of surfactant-free emulsion polymerization has also been described [24].…”

Section: Introductionmentioning

confidence: 99%

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Design of Co3O4@SiO2 Nanorattles for Catalytic Toluene Combustion Based on Bottom-Up Strategy Involving Spherical Poly(styrene-co-acrylic Acid) Template

et al. 2021

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Bearing in mind the need to develop optimal transition metal oxide-based catalysts for the combustion of volatile organic compounds (VOCs), yolk-shell materials were proposed. The constructed composites contained catalytically active Co3O4 nanoparticles, protected against aggregation and highly dispersed in a shell made of porous SiO2, forming a specific type of nanoreactor. The bottom-up synthesis started with obtaining spherical poly(styrene-co-acrylic acid) copolymer (PS30) cores, which were then covered with the SiO2 layer. The Co3O4 active phase was deposited by impregnation using the PS30@SiO2 composite as well as hollow SiO2 spheres with the removed copolymer core. Structure (XRD), morphology (SEM), chemical composition (XRF), state of the active phase (UV-Vis-DR and XPS) and reducibility (H2-TPR) of the obtained catalysts were studied. It was proven that the introduction of Co3O4 nanoparticles into the empty SiO2 spheres resulted in their loose distribution, which facilitated the access of reagents to active sites and, on the other hand, promoted the involvement of lattice oxygen in the catalytic process. As a result, the catalysts obtained in this way showed a very high activity in the combustion of toluene, which significantly exceeded that achieved over a standard silica gel supported Co3O4 catalyst.

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Versatile hollow fluorescent metal-silica nanohybrids through a modified microemulsion synthesis route

Clemente

Moreno

Lobera

et al. 2018

Journal of Colloid and Interface Science

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Silica-metal nanohybrids are common materials for applications in biomedicine, catalysis or sensing. Also, hollow structures are of interest as they provide additional useful features. However, in these materials the control of the size and accessibility to the inner regions of the structure usually requires complex synthesis procedures. Here we report a simple colloidal procedure for synthesizing hollow silica-metal nanohybrids, driven by the diffusion of metal precursors through the porous silica shell and subsequent reduction in aqueous solutions. The formation of hollow nanoparticles is controlled by the colloidal conditions during synthesis, which affect the ripening of hollow nanoparticles in presence of organosilanes. The modification of the conditions during synthesis affected the growth of silica precursors in presence of fluorescein isothiocyanate (FITC). The limited access to water molecules during the hydrolysis of silica precursors is attributed to the hydrophobicity of organic fluorescent molecules linked to the condensing silica clusters at the initial stages of nanoparticle formation and to the limitation of water content in the microemulsion method used. Finally, the growth of metal nanoseeds at the core of hollow nanoparticles can be easily achieved though a simple method in aqueous environment. The pH and thermal conditions during the reduction process affect the formation of metal-silica nanohybrids and their structural features.

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Encapsulation of multiple large spherical silica nanoparticles in hollow spherical silica shells

Cited by 5 publications

References 24 publications

Complex Polymeric Microstructures with Programmable Architecture via Pickering Emulsion-Templated In Situ Polymerization

Complex Polymeric Microstructures with Programmable Architecture via Pickering Emulsion-Templated In Situ Polymerization

Design of Co3O4@SiO2 Nanorattles for Catalytic Toluene Combustion Based on Bottom-Up Strategy Involving Spherical Poly(styrene-co-acrylic Acid) Template

Versatile hollow fluorescent metal-silica nanohybrids through a modified microemulsion synthesis route

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