General synthesis of hollow composite ellipsoids

A facile and general approach towards composite hollow ellipsoids has been proposed. The parent polystyrene (PS) hollow spheres are embedded in a matrix, for example, poly(vinyl alcohol), and stretched into the corresponding ellipsoids. The aspect ratio of the ellipsoids is tunable by stretching extent. Accordingly, sulfonated PS hollow ellipsoids are achieved by sulfonation of the PS hollow ellipsoids, which will facilitate an easy complexation with functional materials. Composite hollow ellipsoids, with varied composition ranging between polymer, metal and oxides, and inorganic materials, are synthesized against the polymer ellipsoids as templates. By controlling growth of the functional materials at specific sites, structure of the composite hollow ellipsoids is controlled such as surface-pillared, single-shelled and double-shelled. This approach avoids traditional removal of polymer templates, thus guarantees the shell integrity of the composite hollow ellipsoids.     

模板法制备复合中空微球

本文报道以一种商品化的聚苯乙烯中空球为模板, 采用溶胀聚合技术合成了具有IPN(Inter-Penetrating Network)结构的复合中空球; 对其中的一种高分子网络进行化学改性引入所需官能团, 制得带有羧基的聚合物凝胶中空球; 利用凝胶诱导生长特性, 成功制得聚合物复合中空球. 此方法无需去除模板就可批量制备各种复合功能中空球.     

Hierarchically Structured Porous Films of Silica Hollow Spheres via Layer‐by‐Layer Assembly and Their Superhydrophilic and Antifogging Properties

Raspberrylike organic/inorganic composite spheres are prepared by stepwise electrostatic assembly of polyelectrolytes and silica nanoparticles onto monodisperse polystyrene spheres. Hierarchically structured porous films of silica hollow spheres are fabricated from these composite spheres by layer‐by‐layer assembly with polyelectrolytes followed by calcination. The morphologies of the raspberrylike organic/inorganic composite spheres and the derived hierarchically structured porous films are observed by scanning and transmission electron microscopy. The surface properties of these films are investigated by measuring their water contact angles, water‐spreading speed, and antifogging properties. The results show that such hierarchically structured porous films of silica hollow spheres have unique superhydrophilic and antifogging properties. Finally, the formation mechanism of these nanostructures and property–structure relationships are discussed in detail on the basis of experimental observations.     

Polysaccharides as a source of advanced materials: Cellulose hollow microspheres for drug delivery in cancer therapy

Biocompatible hollow poly(methyl acrylic acid-co-N-isopropylacrylamide-co-ethyleneglycol dimethacrylate)@cellulose succinate (P(MAA-co-NIPAAM-co-EGDMA)@CS) microspheres have been synthesized by employing uniform silica-MPS microspheres as template. Silica spheres were synthesized via Stöber method involving tetraethyl orthosilicate. The surface of resulting silica Stöber microspheres was modified using 3-methacryloxypropyltrimethoxysilane (MPS), a polymerizable silane coupling agent. The above reagent introduces carbon–carbon double bonds on microspheres’ surface. This strategy uses the copolymerization of the following monomers, methacrylic acid (MAA), N-isopropyl acrylamide (NIPAAM) and the ethyleneglycol dimethacrylate (EGDMA), which was used as cross-linker, aiming at fabricating the first shell. Distillation precipitation polymerization method was carried out with 2,2-azobis(2-methylpropionitrile) as initiator in acetonitrile aiming at coating the inorganic microspheres with organic shell of the above-mentioned copolymer. In continuation, cellulose succinate and cellulose powder was absorbed through electrostatic interactions onto microspheres’ surface and the isolated product was cross-linked through esteric bonds formation. The cellulose succinate hollow microspheres were obtained after the silica core removal. The resulting spheres were characterized by Fourier transform infrared spectroscopy and observed by scanning and transmission electron microscopy. Dynamic light scattering was used to study the hydrodynamic diameter of the synthesized microspheres. The anticancer drug daunorubicin was loaded in the spheres, and its release behavior was evaluated at acidic and slightly basic pH conditions, aiming at evaluating its behavior at the healthy and pathogenic tissues.     

Preparation of single-hole hollow polymer nanospheres by raspberry-like template method

Single-hole hollow polymer nanospheres were fabricated by raspberry-like template method using "graft-from" strategy through atom transfer radical polymerization (ATRP). Nanometer-sized silica spheres were covalently attached onto the surfaces of micrometer-sized silica spheres. Crosslinked polymer shells on the nano-sized spheres outside the attached area were formed by "graft-from" strategy through ATRP. After removal of the silica cores, single-hole hollow crosslinked polymer nanospheres were obtained. In this strategy, most of ATRP monomers may be used and thus many functional groups can be easily incorporated into the single-hole hollow crosslinked polymer nanospheres.     

A general method for the synthesis of monodisperse hollow inorganic-organic hybrid microspheres with interior functionalized poly(methacrylic acid) shells

Hollow inorganic-organic hybrid microspheres, such as silica, titania, and zirconia, with interior poly(methacrylic acid) (PMAA) functionalized shell were synthesized by a general method containing a two-stage reaction. The hollow inorganic shell-layer with interior polymeric component was formed over the PMAA template during the second-stage controlled hydrolysis of inorganic precursors together with disintegration of PMAA cores and adhering to the interior wall of the silica during the drying process due to the capillary force as well as the competitive hydrogen bond interaction. In this process, PMAA microspheres were prepared by distillation precipitation polymerization of methacrylic acid (MAA) in acetonitrile as the first-stage reaction. The present work elaborately investigated the effects of the reaction conditions, including the amount of the tetraethyl orthosilicate (TEOS) precursors and the amount of ammonium hydroxide catalyst on the morphology and structure of the resultant hollow composite microspheres, which were characterized by transmission electron microscopy (TEM), Fourier-transform infrared spectra (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption.     

Fabrication of functional hollow carbon spheres with large hollow interior as active colloidal catalysts

In this study,we have established a facile method to synthesize functional hollow carbon spheres with large hollow interior,which can act as active colloidal catalysts.The method includes the following steps:first,hollow polymer spheres with large hollow interior were prepared using sodium oleate as the hollow core generator,and 2,4-dihydroxybenzoic acid and hexamethylene tetramine(HMT) as the polymer precursors under hydrothermal conditions;Fe 3+ or Ag + cations were then introduced into the as-prepared hollow polymer spheres through the carboxyl groups;finally,the hollow polymer spheres can be pseudomorphically converted to hollow carbon spheres during pyrolysis process,meanwhile iron or silver nanoparticles can also be formed in the carbon shell simultaneously.The structures of the obtained functional hollow carbon spheres were characterized by TEM,XRD,and TG.As an example,Ag-doped hollow carbon spheres were used as colloid catalysts which showed high catalytic activity in 4-nitrophenol reduction reaction.     

Low‐Temperature Facile Template Synthesis of Crystalline Inorganic Composite Hollow Spheres

This report presents a facile approach for the low‐temperature synthesis of crystalline inorganic‐oxide composite hollow spheres by employing the bulk controlled synthesis of inorganic‐oxide nanocrystals with polymer spheres as templates. The sulfonated polystyrene gel layer can adsorb the target precursor and induce inorganic nanocrystals to grow on the template in situ. The crystalline phase and morphology of the composite shell is tunable. By simply adjusting the acidity of the titania sol, crystalline titania composite hollow spheres with tunable crystalline phases of anatase, rutile, or a mixture of both were achieved. The approach is general and has been extended to synthesize the representative perovskite oxide (barium and strontium titanate) composite hollow spheres. The traditional thermal treatment for crystallite transformation is not required, thus intact shells can be guaranteed. The combination of oxide properties such as high refractive index, high dielectric constant, and catalytic ability with the cavity of the hollow spheres is promising for applications such as opacifiers, photonic crystals, high‐κ‐gate dielectrics, and photocatalysis.     

Synthesis and utilization of monodisperse hollow polymeric particles in photonic crystals

We developed a process to fabricate 150-700 nm monodisperse polymer particles with 100-500 nm hollow cores. These hollow particles were fabricated via dispersion polymerization to synthesize a polymer shell around monodisperse SiO(2) particles. The SiO(2) cores were then removed by HF etching to produce monodisperse hollow polymeric particle shells. The hollow core size and the polymer shell thickness, can be easily varied over significant size ranges. These hollow polymeric particles are sufficiently monodisperse that upon centrifugation from ethanol they form well-ordered close-packed colloidal crystals that diffract light. After the surfaces are functionalized with sulfonates, these particles self-assemble into crystalline colloidal arrays in deionized water. This synthetic method can also be used to create monodisperse particles with complex and unusual morphologies. For example, we synthesized hollow particles containing two concentric-independent, spherical polymer shells, and hollow silica particles which contain a central spherical silica core. In addition, these hollow spheres can be used as template microreactors. For example, we were able to fabricate monodisperse polymer spheres containing high concentrations of magnetic nanospheres formed by direct precipitation within the hollow cores.     

A one-pot synthetic approach to prepare palladium nanoparticles embedded hierarchically porous TiO2 hollow spheres for hydrogen peroxide sensing

A simple one-step method to fabricate hierarchically porous TiO₂/Pd composite hollow spheres without any template was developed by using solvothermal treatment. Pd nanoparticles (2-5 nm) were well dispersed in the mesopores of the TiO₂ hollow spheres via in-situ reduction. In our experiment, polyvinylpyrrolidone played an important role in the synthetic process as the reducing agent and the connective material between TiO₂ and Pd nanoparticles. HF species generated from solvothermal reaction leaded to the formation of TiO₂ hollow spheres and Ostwald ripening was another main factor that affected the size and structure of the hollow spheres. The as-prepared TiO₂/Pd composite hollow spheres exhibited high electrocatalytic activity towards the reduction of H₂O₂. The sensitivity was about 226.72 μA mM⁻¹ cm⁻² with a detection limit of 3.81 μM at a signal-to-noise ratio of 3. These results made the hierarchically porous TiO₂/Pd composite a promising platform for fabricating new nonenzymic biosensors.     

Synthesis of hollow polypyrrole-platinum complex spheres and their successful application as a catalyst for decomposition of hydrogen peroxide

Hollow pyrrole-platinumpoly (PPy-Pt) complex spheres effectively catalyze the decomposition of hydrogen peroxide to form oxygen. The method used to synthesize the catalysts employs chemical polymerization of pyrrole with potassium hexachloroplatinate(IV) as oxidant and ZSM-5 molecular sieve as a hard template removable by dissolution. ZSM-5 molecular sieve used as template has the following merits: it can be easily removed, it is inexpensive and owing to micrometer size it shows a minimal aggregation. In addition, the use of the zeolite avoids the need for non-volatile surfactants which may be adsorbed onto the synthesized PPy-Pt complex spheres and interfere with their possible applications in catalysis. The new micron-sized hollow PPy-Pt complex spheres are produced simply and cost-effectively, and they can be expected to play an important role in wastewater treatment technologies. The synthetic method may represent a novel route to prepare hollow conductive polymer spheres doped by various metals for specific applications.     

Fabrication of triple-shelled hollow spheres with optical properties via RAFT polymerization

<正>The triple-shelled hollow spheres with optical properties were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization.After removal the core templates of the poly(styrene),the hollow silica spheres were obtained.The coating process of poly(methyl methacrylate)(PMMA) on the hollow silica spheres surface via surface RAFT polymerization was performed subsequently.The polymers coated on the hollow spheres surfaces were end-functionalized by trithiocarbonate,and they were used as RAFT agent to proceed the chain extension polymerization using Tb complex as monomer.The samples were characterized by FT-IR,SEM and luminescence spectroscopy respectively.The results indicated that the triple-shelled hollow spheres had been prepared successfully and the average diameter of the hollow core was about 1μm.     

Architecture of micron-scale hollow spheres composed of silica nanoparticles and approach to luminescent spheres

Micron-scale hollow spheres were successfully constructed with silica nanoparticles by templating of polymer spheres. Subsequently, the use of 3-aminopropyltriethoxysilane (APTES) introduces carbon and oxygen defects in the silica nanoparticles resulting from calcination of the aminopropyl group. In this approach, the template of micron-scale polymer spheres was prepared from dispersion polymerization. Subsequent St?ber process results in the formation of a silica layer attached to the polymer sphere surfaces. After calcination, the obtained micron-scale hollow silica spheres were then studied on the relationship between the particle diameter and the surface morphology. The luminescence of hollow spheres was prepared through using APTES in St?ber process, and which of related the appearance of luminescence to the APTES concentration and calcination temperature. The results of this study can provide useful information for the structure of micron-scale hollow spheres and their application to luminescent materials.     

A simple method to synthesize sea urchin-like polyaniline hollow spheres

Oxidative polymerization of aniline diffusing out from polystyrene hollow spheres with ferric chloride results in the formation of sea urchin-like polyaniline composite hollow spheres, which provide a simple chemical way to assemble conducting polymer nanofibers into complex structure under mild condition.     

Novel one-step route for synthesizing CdS/polystyrene nanocomposite hollow spheres

CdS/polystyrene nanocomposite hollow spheres with diameters between 240 and 500 nm were synthesized under ambient conditions by a novel microemulsion method in which the polymerization of styrene and the formation of CdS nanoparticles were initiated by gamma-irradiation. The product was characterized by transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA), which show the walls of the hollow spheres are porous and composed of polystyrene containing homogeneously dispersed CdS nanoparticles. The quantum-confined effect of the CdS/polystyrene nanocomposite hollow spheres is confirmed by the ultraviolet-visible (UV-vis) and photoluminescent (PL) spectra. We propose that the walls of these nanocomposite hollow spheres originate from the simultaneous synthesis of polystyrene and CdS nanoparticles at the interface of microemulsion droplets. This novel method is expected to produce various inorganic/polymer nanocomposite hollow spheres with potential applications in the fields of materials science and biotechnology.     

Synthesis of poly(o-phenylenediamine) hollow spheres and nanofibers using different oxidizing agents

Poly(o-phenylenediamine) (PoPD) hollow spheres (ca. 800 nm in outer diameter) were synthesized by a simple solution route using ammonium persulfate (APS) as the oxidizing agent, whereas PoPD nanofibers (0.5-2 μm in width and more than 100 μm in length) and gold nanoparticles (200-500 nm) were obtained when changing the oxidizing agent of APS to chlorauric acid (HAuCl₄). The chemical structures of PoPD hollow spheres and nanofibers were characterized by FTIR and XRD spectra. When using HAuCl₄ as the oxidizing agent, the products of PoPD nanofibers and gold nanoparticles could be separated by chemical methods. The monomer droplets were proposed to act as template to the formation of polymer hollow spheres while the oriented growth of polymer nanofibers might be catalyzed by gold nanoparticles.     

Mesoporous hollow spheres from soap bubbling

The smaller and more stable bubbles can be generated from the large parent bubbles by rupture. In the presence of a bubble blowing agent, hollow spheres can be prepared by bubbling a silica sol. Herein, the trapped gas inside the bubble acts as a template. When the porogen, i.e., other surfactant, is introduced, a mesostructured shell forms by the co-assembly with the silica sol during sol-gel process. Morphological evolution emphasizes the prerequisite of an intermediate interior gas flow rate and high exterior gas flow rate for hollow spheres. The method is valid for many compositions from inorganic, polymer to their composites.     

Fabrication and biocompatible characterization of magnetic hollow capsules

Monodispersed Fe3O4/polypyrrole （PPy） hollow particles were synthesized via controllable in-situ deposition and polymerization techniques using poly（styrene-co-acrylic） （PSA） latex as template. Field-dependent magnetization plot illustrates that the capsules are superparamagnetic at 300 K. FTIR spectrum confirms that the myoglobin （Mb） molecule adsorbed on the surface of Fe3O4/PPy hollow particle essentially retains its native structure. Furthermore, direct electrochemistry of Mb can be realized on Fe3O4/PPy capsules modified pyrolytic graphite disk electrode, which indicates that the magnetic conductive polymer capsules can promote the electron transfer of protein.     

Fabrication of anisotropic silica hollow microspheres using polymeric protrusion particles as templates

Anisotropic polystyrene/poly(styrene-co-divinylbenzene) (PS/P(S-DVB)) protrusion particles with various morphologies such as eyeball-like, snowman-like, and raspberry-like were synthesized using a modified seeded polymerization method by dynamically controlling and stabilizing the phase separation. The effects of swelling agent, crosslinker, and monomer concentrations on the particle morphologies were studied. Using the PS/P(S-DVB) protrusion particles as templates, anisotropic silica (SiO₂) hollow microspheres were fabricated facilely. The obtained anisotropic silica hollow spheres had a potential application in rapid waste removal and detoxification extraction with a very simple procedure.     

Preparation and properties of nitrogen-containing hollow carbon nanospheres by pyrolysis of polyaniline-lignosulfonate composites

Polyaniline-lignosulfonate composite hollow spheres were synthesized by using one-step unstirred polymerization of aniline in the presence of lignosulfonate. Novel nitrogen-containing hollow carbon nanospheres were prepared by direct pyrolysis of the polyaniline-lignosulfonate composite spheres at different temperatures under a nitrogen atmosphere. Thermal behavior of the polyaniline-lignosulfonate composite spheres was studied by TG-DTG, FTIR and element analyze instruments. The resultant carbon spheres were characterized by SEM, XRD and nitrogen adsorption-desorption measurement. It was found that the pyrolysis products of the polyaniline-lignosulfonate composite spheres were made up of uniform hollow carbon nanospheres with an average diameter of 135 nm. Furthermore, the hollow carbon nanospheres exhibit high BET surface area range from 381.6 m² g⁻¹ to 700.2 m² g⁻¹. The hollow carbon nanospheres could be used as adsorbents of papain. The papain adsorption capacity for the carbon spheres prepared at 1200 °C was up to 1161 mg g⁻¹ at an initial papain concentration of 10 mg mL⁻¹ at 25 °C.