A facile approach to fabrication of PbS hollow spheres with improved polystyrene templates

This paper provides a simple route to produce monodisperse PbS hollow spheres by using cationic polystyrene (PS) micro-particles as templates. The templates used in our experiment, were prepared via emulsifier-free polymerization by using the cationic monomer 2-(methacryloyloxy) ethyltrimethylammonium chloride as co-monomer. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTRI) were used to characterize the structure of the obtained PbS/PS composites and hollow PbS spheres. It was found that the as-produced samples are well-defined core-shell structures with an average diameter of about 0.98 μm. TEM showed that after the removal of the templates, the hollow structures were perfectly retained.     

Sol-gel synthesis of titania hollow spheres

TiO₂ hollow spheres are prepared by a convenient sol-gel method at room temperature. The products were characterized by XRD, FESEM, TEM and FT-IR. It was found that these spheres are hollow inside with outer diameters of 200-500 nm. The average mesoporous diameter is about 9.8 nm. And the BET surface area and specific pore volume are about 161.9 m²/g and 0.441 cm³/g, respectively.     

Hydrothermal synthesis and characterization of PbS cage-like structures

A hydrothermal route has been proposed for the synthesis of PbS cage-like structures from Pb(NO₃)₂, Na₂SO₄ and Na₂S·9H₂O. This route involved a two-step procedure (that is, first, PbSO₄ was prepared through the precipitation reaction of Pb(NO₃)₂ and Na₂SO₄ in distilled water under the ambient condition; second, cubic phase PbS with cage-like structure was prepared via the hydrothermal reaction of PbSO₄ and Na₂S·9H₂O at 180 °C for 12 h). The resultant products were characterized by X-ray diffraction, field emission scanning electron microscope, transmission electron microscopy, high resolution transmission electron microscopy, and room temperature Raman spectra. It was observed that PbS cage-like structures had unique optical property and may be useful in further applications such as Raman detectors.     

Templating synthesis of waxberried hematite hollow spheres

Novel hematite (α-Fe₂O₃) hollow spheres were prepared through a surfactant-assisted solvothermal process. The XRD, SEM and TEM characterization data confirm that the formation of α-Fe₂O₃ hollow spheres exhibits waxberry-like architectures with spindle nanoparticles, the length in the range of 150-400 nm, as building block. Their tips of these nanoparticles were concentrated on a center. The sizes of α-Fe₂O₃ waxberry are less than 3 µm. They possess good photocatalytic properties when used for the degradation of salicylic acid in water. The formation mechanism of α-Fe₂O₃ waxberry is also discussed.     

Hydrothermal synthesis of spindle-like ZnS hollow nanostructures

Spindle-like hollow nanostructures of zinc sulfide (ZnS) have been successfully synthesized by hydrothermal process using a simple surfactant emulsion template. The morphologies of ZnS nanostructures were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and field-emission scanning electron microscopy (FE-SEM). It is found that most of the products including twin ellipsoids with connected hollow cores are reminiscent of spindle-like structures. The lengths, widths and the thickness of the shell are in the range of 1-2 μm, 300-450 nm and 20-40 nm, respectively. Selected area electron diffraction (SAED) and X-ray powder diffraction (XRD) patterns show that the shell is composed of sphalerite ZnS polycrystals.     

Hydrothermal synthesis of SnO2 hollow microspheres

SnO₂ hollow microspheres have been synthesized by a hydrothermal method. X-ray powder diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM) were used to characterize such hollow microspheres. SEM image shows that SnO₂ microspheres with diameters of 0.5–1 μm are composed of SnO₂ nanoparticles with about 15 nm in diameter. Some broken microspheres indicate the hollow spherical structure. XRD shows that SnO₂ hollow microspheres have tetragonal structure.     

CuS纳米空心管结构的水热合成

以氯化铜和硫代乙酰胺为原料,在碱性条件下,利用低温简单水热法合成了硫化铜纳米空心管结构。通过XRD、TEM、FT-IR等检测方法对产品进行了结构和形貌分析。结果表明,所得硫化铜产品为六方相铜蓝矿结构,纳米空心管结构,纳米管的直径为150～200nm,长度为1.5～2.5μm;在1110cm-1处出现Cu-S键的红外特征吸收峰;同时对可能的生长机理做了阐述。     

A room-temperature synthesis of titanium nitride hollow spheres

Titanium nitride hollow spheres were synthesized by the reaction of TiCl4 and NaNH2 at room temperature. X-ray powder diffraction (XRD) pattern could be indexed as cubic TiN with the lattice constants of a = 4.236 A. Transmission electron microscopy (TEM) images showed hollow spheres with diameter about 200 nm. A possible formation mechanism of TiN hollow spheres was discussed.     

Simple synthesis of hollow carbon spheres from glucose

Hollow carbon spheres were prepared by the reaction between glucose and Zn particles at 550 °C. Scanning and transmission electron microscopies reveal that most of the spheres are about 1-2 µm in diameter, similar to the sizes of the Zn particle. The shells of the spheres are comprised of numerous hollow nanospheres with the diameter of 10-100 nm. The specific surface area of the spheres is 207 m²/g. The Zn particles act as both the reactant and the template for the micron-scale spheres, and the H₂ bubbles generated during the reaction as the template for the hollow nanospheres.     

From CdS aggregate spheres to PbS hollow spheres: a case study of the growth mechanism in chemical conversion

Monodisperse PbS hollow spheres were successfully prepared via using CdS aggregate spheres as template. The present strategy is based on the different solubilities of CdS and PbS. This process was intensively studied by time-dependent trails which were monitored by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and photoluminescence spectroscopy (PL). Reaction temperature was found to play an important role in controlling the diffusion rate of Pb²⁺ ions and the quality of as-prepared PbS crystals, which finally leads to different shape evolution processes from the starting aggregate spheres to the final hollow spheres. Two growth mechanisms defined as kinetics-controlled process (KCP) and thermodynamics-controlled process (TDCP) were, respectively, proposed for the two conversion patterns observed at 30 and 90 °C. Moreover, specific structural evolution including primary crystal size, diameter growth, and shell thickness were also discussed in detail. This work is of great significance in elucidating the underlying mechanism of chemical conversion and could be potentially applied to synthesize other hollow architectures.     

Coprecipitation synthesis of hollow Zn2SnO4 spheres

Pure and Dy³⁺-doped Zn₂SnO₄ (ZTO) hollow spheres, integrated with nanoparticles, have been synthesized using the coprecipitation method. The ZTO spheres have been characterized with X-ray diffraction and scanning electron microscope. The photoluminescence and photocatalytic properties are investigated. The influences of Dy³⁺ ions on the morphology and the photoluminescence of ZTO have been explained in detail.     

Surface synthesis of PbS nanoparticles on silica spheres by a sonochemical approach

A simple sonochemical approach for the preparation of PbS nanoparticles homogeneously coated on sub-micrometer silica spheres has been described. The transmission electron microscopy and scanning electron microscopy images show that the PbS nanoparticles with size of 30 nm were coated on the silica spheres, without any free nanoparticles. X-ray diffraction reveals that the PbS nanoparticles are of cubic rock-salt structure. Moreover, by dissolving the silica cores with a diluted hydrofluoric acid solution, stable PbS hollow structures were obtained. It is considered that the sonochemical process in which triethanolamine acted as complex agent played an important role for the homogenouse coating of PbS nanoparticles on silica spheres.     

Facile synthesis of hierarchically structured NiO flower-like hollow spheres

The hierarchical flower-like NiO hollow spheres were synthesised by a facile method without using any templates or surfactants. The as-prepared sample and precursor were characterised by X-ray diffraction and field emission scanning electron microscopy. The results indicated that the as-prepared NiO is self-assembled hierarchically. During the assembly of NiO, the reaction time plays an important role. The flower-like NiO hollow sphere showed much higher catalytic activity than large-size NiO or hollow NiO for the oxidative dehydrogenation of ethane to ethylene due to its special structure.     

Shape-controlled synthesis and properties of dandelion-like manganese sulfide hollow spheres

Dandelion-like gamma-manganese (II) sulfide (MnS) hollow spheres assembled with nanorods have been prepared via a hydrothermal process in the presence of l-cysteine and polyvinylpyrrolidone (PVP). l-cysteine was employed as not only sulfur source, but also coordinating reagent for the synthesis of dandelion-like MnS hollow spheres. The morphology, structure and properties of as-prepared products have been investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), selected area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM) and photoluminescence spectra (PL). The probable formation mechanism of as-prepared MnS hollow spheres was discussed on the basis of the experimental results. This strategy may provide an effective method for the fabrication of other metal sulfides hollow spheres.     

Fabrication of hollow silver spheres by MPTMS-functionalized hollow silica spheres as templates

In this study, we provide a strategy to prepare the hollow silver spheres by accumulating the silver nanoparticles on the surface of 3-mercaptopropyltrimethoxysilane (MPTMS)-functionalized silica as templates, which was accomplished by the chemisorption between silver nanoparticles and thiol groups. Then, the resulting hollow silver spheres were obtained through the chemical wet etching process with 10 M HF solution. In conventional method, the fabrication of hollow silver spheres from core-shell spheres was not easy due to the difficulties in retaining the shell structures during core removal. The method in this paper could overcome this limitation. The major focus of study is on understanding the mechanism of formation of the hollow silver spheres through the self-assembly behavior by chemisorption between silver nanoparticles and thiol groups. The silver-coated silica and hollow silver spheres were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution TEM (HR-TEM), and X-ray photoelectron spectroscopy (XPS).     

Sol-gel synthesis, microstructure and adsorption properties of hollow silica spheres

Spherical colloidal particles with a hollow interior and a mesoporous shell are particularly useful for drug delivery and release because such spheres combine the unique properties of hollow interior (for storing the drug) with mesoporous shell (for controlled release). Hollow silica spheres (HSS) with a mesoporous shell were prepared via a sol-gel process in the presence of dual templates polystyrene spheres and cetyltrimethylammonium bromide for creating the hollow core and mesopore shell. The effect of the ratio of silica precursor over polystyrene spheres on particle morphology and pore structure of the HSS was investigated. The adsorption kinetics of methyl blue on the HSS was evaluated and correlated with the mesoporous shell structure.     

One-step synthesis of hierarchically porous hybrid TiO2 hollow spheres with high photocatalytic activity

Hierarchically porous hybrid TiO₂ hollow spheres were solvothermally synthesized successfully by using tetrabutyl titanate as titanium precursor and hydrated metal sulfates as soft templates. The as-prepared TiO₂ spheres with hierarchically pore structures and high specific surface area and pore volume consisted of highly crystallized anatase TiO₂ nanocrystals hybridized with a small amount of metal oxide from the hydrated sulfate. The proposed hydrated-sulfate assisted solvothermal (HAS) synthesis strategy was demonstrated to be widely applicable to various systems. Evaluation of the hybrid TiO₂ hollow spheres for the photo-decomposition of methyl orange (MO) under visible-light irradiation revealed that they exhibited excellent photocatalytic activity and durability.     

Synthesis and optical properties of ZnS hollow spheres from single source precursor

A facile one-pot synthesis of ZnS hollow spheres has been carried out via a chemical transformation induced inside-out Ostwald ripening process from a single source precursor. The size and shell thickness of the ZnS hollow spheres can be controlled by adjusting the reaction temperature and reaction time, respectively. Photoluminescence spectra show a dominant emission peak at 470 nm accompanied by several weaker peaks. UV-vis measurement reveals that the obtained ZnS hollow spheres exhibit “hollow effect”. The formation process of ZnS hollow spheres has been discussed.     

Controllable synthesis of silica hollow spheres by vesicle templating of silicone surfactants

Silica hollow spheres (SHSs) have been designed and prepared through three distinct synthetic routes based on the self-assembling of comb-like copolymer silicone surfactants. This process was based on the rule of similarities for hydrophobicity and hydrophilicity between the surfactant and a silica source. The directed silica wall formations were performed at different confined spaces of the vesicles, including the outer and inner surfaces, and the hydrophobic parts of the bi-layers. The resultant SHSs possess tailorable shell thicknesses (20–400 nm), particle sizes (200 nm–1.2 μm), and a high dispersibility in aqueous solutions.