Template-free polyoxometalate-assisted synthesis for ZnO hollow spheres

ZnO hollow spheres with diameters ranging from 400 to 600 nm and the thickness of shell approximate 80 nm were synthesized by a simple polyoxometalate-assisted solvothermal route without using any templates. The effect of polyoxometalate concentration, reaction time and temperature on the formation of the hollow spheres was investigated. The results indicated that the hollow spheres were composed of porous shells with nanoparticles and polyoxometalate play a key role in controlling morphology of ZnO. A possible growth mechanism based on polyoxometalate-assisted assembly and slow Ostwald ripening dissolution in ethanol solution is tentatively proposed. In addition, the room temperature photoluminescence spectrum showed that the ZnO hollow spheres exhibit exciting emission features with wide band covering nearly all the visible region.     

Template synthesis of hydrogel composite hollow spheres against polymeric hollow latex

Hierarchically structured hydrogel hollow spheres with functional hydrogels located at desired sites are expected to have new properties. We have developed a facile swelling polymerization route using a polymer hollow sphere as template to synthesize hierarchically structured hydrogel hollow spheres. It is significant to pre-swell the template shell with good solvents, such as chloroform containing oil-soluble initiators to control interaction, thus, polymerization locus of different water-soluble functional monomers. Some representative hydrogel composite hollow spheres such as poly(N-isopropylarylamide) and poly(acrylic acid) with different morphologies have been synthesized. Hydrogels with functional groups can favorably complex with desired materials; hierarchically structured inorganic or polymer composite hollow spheres are synthesized by a sol–gel process of the inorganic precursor by using different hydrogel composite hollow spheres as templates.     

Surfactant-assistant and facile synthesis of hollow ZnS nanospheres

Small and monodisperse ZnS hollow nanospheres with outer diameter ranging from 60 to 70 nm and wall thickness of 15-20 nm were fabricated in a large scale by a simple surfactant polyethylene glycol (PEG) assisted method. The diameter and the wall thickness of the hollow nanospheres could be controlled by manipulating the amount of PEG and the aging time, respectively. Moreover, the wall of these hollow nanospheres is very compact. The product was characterized by X-ray power diffraction (XRD), transmission electron microscopy (TEM), UV-vis spectrum and fluorescence spectroscopy. The photocatalytic activity of as-prepared ZnS hollow nanospheres was also evaluated by using methyl orange (MO) as a model organic compound and the result revealed that their photocatalytic activity is a little lower than that of Degussa P25 TiO(2) but better than that of ZnS nanocrystals prepared by literature method. Furthermore, a rational mechanism to the formation and evolution of the products is proposed.     

The synthesis of ZnS hollow nanospheres with nanoporous shell

ZnS hollow nanospheres with nanoporous shell were successfully synthesized through the evolvement of ZnO nanospheres which were synthesized by hydrothermal method with poly (sodium-p-styrene sulfonate) (PSS) as surfactant at low temperature. The as-synthesized samples were characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), UV/vis spectrum and N₂ adsorption. The results showed that the shell of as-synthesized ZnS hollow structure was composed of many fine crystallites and had a nanoporous structure with pore diameter about 4 nm demonstrated by N₂ adsorption/desorption isotherm. The sample possessed efficiency of photocatalytic degradation on X-containing (X=Cl, Br, I) organic pollutants.     

One template synthesis of raspberry-like hierarchical siliceous hollow spheres

We report the synthesis of raspberry-like hierarchical siliceous hollow spheres (HSHS) via a one-pot, one template approach. The siliceous species and block copolymer molecules self-assemble simultaneously into composite spherical micelles and vesicles in solution. The colloidal interaction between spheres with different sizes gives rise to the final HSHS structure with a raspberry morphology.     

Hydrothermal synthesis of hollow silica spheres under acidic conditions

It is well-known that silica can be etched in alkaline media or in a unique hydrofluoric acid (HF) solution, which is widely used to prepare various kinds of hollow nanostructures (including silica hollow structures) via silica-templating methods. In our experiments, we found that sto?ber silica spheres could be etched in generic acidic media in a well-controlled way under hydrothermal conditions, forming well-defined hollow/rattle-type silica spheres. Furthermore, some salts such as NaCl and Na(2)SO(4) were found to be favorable for the formation of hollow/rattle-type silica spheres.     

LaAlO3 hollow spheres: synthesis and luminescence properties

Nearly monodisperse LaAlO(3) hollow spheres are synthesized by a novel precursor thermal decomposition method. Spherical colloids of capsulelike precursors with uniform diameters of 273 ± 35 nm have been synthesized by a solvothermal method. These spherical colloids could convert to LaAlO(3) hollow spheres with diameters of 166 ± 26 nm by a thermal decomposition process. The thermal transformation process from the precursors to LaAlO(3) was characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), and the Fourier transform infrared spectroscopy (FT-IR). By the doping of various lanthanide ions (Sm(3+), Eu(3+), and Tb(3+)), the emission luminescence of lanthanide-doped LaAlO(3) hollow microspheres can be tuned from red to green. In particular, these luminescent LaAlO(3) hollow spheres can be well dispersed in polar solvents such as the ethanol and water, which broadens the range of potential applications of these hollow spheres. The UV-vis absorption spectra show energy absorption at 211, 223, and 313 nm corresponding to the host lattice absorption and charge-transfer transitions. The results are in good agreement with the peaks observed in the excitation spectra.     

A facile method of synthesis of asymmetric hollow silica spheres

This paper presents a "one-step" method to synthesize asymmetric hollow silica spheres. In this method, when positively charged polystyrene particles were blended with mercaptopropyltriethoxysilane and stirred at 50 °C in alkaline ethanol/water medium for a period of time, Janus or lobed asymmetric hollow silica spheres could be directly obtained, just changing the ratio of ethanol to water in the reaction medium. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to characterize the morphology and topography of the asymmetric hollow silica spheres. The formation mechanism was described in detail.     

Facile synthesis of alumina hollow spheres for on-plate-selective enrichment of phosphopeptides

Alumina hollow spheres were synthesized, spotted and sintered on a stainless-steel plate. These spots were used to selectively capture phosphopeptides from peptide mixtures and the captured target peptides could be analyzed by MALDI-MS. This provides a fast and efficient on-plate selective enrichment method for phosphopeptides investigation.     

Chelating ligand-mediated synthesis of hollow ZnS microspheres and its optical properties

Monodispersed hollow ZnS microspheres have been successfully synthesized by a facile ethylenediamine tetraacetic acid (EDTA) mediated hydrothermal route. The sizes of the hollow spheres vary from 1.5 to 3.5 microm when the reaction temperature varied from 130 to 230 degrees C. The formation of these hollow spheres is attributed to the oriented aggregation of ZnS nanocrystals around the gas-liquid interface between H(2)S and water. EDTA plays important role as chelating ligand and capping reagent, which regulates the release of Zn(2+) ions for the formation of ZnS hollow spheres. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis spectroscopy, photoluminescence, and Raman spectroscopy. The obtained ZnS hollow spheres show a sharp and photostable UV emission approximately 370 nm, which is attributed to the recombination process associated with interstitial sulfur vacancy.     

Shape-controlled synthesis and characterization of cobalt oxides hollow spheres and octahedra

We demonstrated that single-crystalline cobalt monoxide (CoO) hollow spheres and octahedra could be selectively synthesized via thermal decomposition of cobalt(II) acetylacetonate in 1-octadecene solvent in the presence of oleic acid and oleylamine. The morphologies and sizes of as-prepared CoO nanocrystals could be controlled by adjusting the reaction parameters. Cobalt oxide (Co(3)O(4)) hollow spheres and octahedra could also be selectively obtained via calcination method using corresponding CoO hollow spheres and octahedra as precursors. The morphology, size and structure of the final products were investigated in detail by XRD, SEM, TEM, HRTEM, DSC, TG, and XPS. The results revealed that the electrochemical performance of cobalt oxide hollow spheres is much better than that of cobalt oxide octahedra, which may be related to the degree of crystallinity, size, and morphology of cobalt oxides.     

Solvothermal synthesis and photoluminescent properties of ZnS/cyclohexylamine: inorganic-organic hybrid semiconductor nanowires

An inorganic-organic hybrid semiconductor, ZnS/CHA (CHA = cyclohexylamine) nanocomposites was successfully synthesized via a solvothermal method using CHA as solvent, which yielded uniform and ultralong nanowires with widths of 100-1000 nm and lengths of 5-20 microm. Changing the reaction conditions could alter the morphology and optical properties of the nanocomposites. The periodic layer subnanometer structures were identified by high-resolution transmission electron microscopy (HR-TEM) images, with thickness of approximately 2 nm. The composites exhibited a very large blue-shift in their optical absorption edge as well as an exciton excitation band due to a strong quantum confinement effect caused by the internal subnanometer-scale structures. The pure hexagonal wurtzite ZnS nanowires were also obtained by extracting the ZnS/CHA nanocomposites with dimethyl formamide (DMF). In addition, the luminescent properties of exciton and defect-related transitions in different samples of ZnS/CHA were discussed in detail.     

Solvothermal synthesis of hollow Eu2O3 microspheres using carbon template-assisted method

This work presents a sol-gel carbon sphere template-assisted method of hollow Eu₂O₃ microspheres preparation. X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), as well as photoluminescence (PL) were used to characterise the products. The formation of hollow structure Eu₂O₃ microspheres can be assigned to a sol-gel carbon template. Furthermore, this work may confirm that the precursor sol-gel can be loaded onto the inner as well as the outer surface of carbon templates similarly as ions and nanocrystals. The presented method can afford a simple and efficient technique to obtain a series of hollow structure inorganic materials with high productivity.     

Aerosol assisted synthesis of silica/phenolic resin composite mesoporous hollow spheres

Hollow spheres of phenolic resin/silica composite are synthesized by macroscopic phase separation of a sorbitan monooleate surfactant Span 80 during aerosol-assisted spraying. The cavity can be evolved from multiple compartments to single hollow cavity with the increase of Span 80 content. The composite shell becomes mesoporous due to the release of small molecules after thermal treatment above 350 °C. After further thermal treatment at a higher temperature for example 900 °C in nitrogen or 1,450 °C in argon, the carbon/silica composite hollow spheres or crystalline silicon carbide hollow spheres are derived, respectively. Compared to the pure phenolic resin-based carbon spheres, thermal stability of the carbon-based composite spheres in air is essentially improved by the introduction of inorganic component silica. The carbon-based composite hollow spheres combine both performances of easy mass transportation through macropores and high specific surface area of mesopores, which will be promising to support catalysts for fuel cells. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Direct synthesis of uniform hollow carbon spheres by a self-assembly template approach

Hollow carbon spheres (50-100 nm) have been synthesized by a self-assembly approach using hexachlorobenzene and Na. NaCl which generated during the reaction has been successfully exploited as a template for the direct synthesis of porous carbon materials, which can be subsequently removed from carbon product by annealing above 1400 degrees C.     

Bioinspired synthesis of calcium carbonate hollow spheres with a nacre-type laminated microstructure

In this Article, we combine the characters of hyperbranched polymers and the concept of double-hydrophilic block copolymer (DHBC) to design a 3D crystal growth modifier, HPG-COOH. The novel modifier can efficiently control the crystallization of CaCO(3) from amorphous nanoparticles to vaterite hollow spheres by a nonclassical crystallization process. The obtained vaterite hollow spheres have a special puffy dandelion-like appearance; that is, the shell of the hollow spheres is constructed by platelet-like vaterite mesocrystals, perpendicular to the globe surface. The cross-section of the wall of a vaterite hollow sphere is similar to that of nacres in microstructure, in which platelet-like calcium carbonate mesocrystals pile up with one another. These results reveal the topology effect of the crystal growth modifier on biomineralization and the essential role of the nonclassical crystallization for constructing hierarchical microstructures.     

Facile synthesis of urchin-like glass/nickel core/shell composite hollow spheres

Novel urchin-like core/shell composite hollow spheres were fabricated by assembly of nickel nanocones on the surface of hollow glass spheres; the effects of some reaction parameters on the morphology of the shell layers and the room temperature magnetic properties of the products were investigated.