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).     

Fabrication of hollow silica spheres and their application in polyacrylate film forming agent

Polystyrene (PS)/silica core/shell spheres were fabricated using mono-dispersed PS as templates by hydrolysis and condensation of two different silica precursors. The PS cores of PS/silica core/shell spheres were dissolved subsequently in the tetrahydrofuran medium to form mono-dispersed hollow silica spheres. The structures and morphologies of hollow silica spheres were characterized by scanning electron microscopy and transmission electron microscopy. Then, polyacrylate/hollow silica composite film forming agents were prepared via physical blending of polyacrylate and two different hollow silica spheres, and the water vapor permeability of their films were compared. The results showed that the structure of hollow silica spheres were very typical and obvious. The silica shell was continuous and uniform using tetraethylorthosilicate as precursor, which was accumulated by many silica seeds with size of 10–20 nm, and the thickness of silica shell was about 16.7 nm. However, the hollow silica spheres using tetraethylorthosilicate and vinyl triethoxysilane as precursors had mesoporous structure in the shell. The introduction of hollow silica spheres could significantly improve the water vapor permeability of polyacrylate film. At last, a possible mechanism for the formation of hollow silica spheres was proposed and the process of water vapor through polyacrylate/hollow silica composite films was modeled.     

Facile preparation of titania hollow spheres by combination of the mixed solvent method and the sol-gel process and post-calcination

Polystyrene (core)-titania (shell) composite spheres consisting were readily prepared by a sol-gel process of titanium tetrabutoxide (TBOT) in a mixed solvent of ethanol/acetonitrile (3:1, v/v). Smooth and homogeneous titania coatings formed when the mixed solvent was dehydrated by anhydrous sodium sulfate. The thickness and surface roughness of titania coating increase with increase of the TBOT concentration. By adjusting the TBOT concentration in the range of 5.8-29.0 mM, the size of titania-coated PS spheres could be varied from 990 to 1125 nm. Calcination at elevated temperature gave dense, homogeneous, robust shells of anatase titania. The sizes of titania hollow spheres are 11.3-16.9% smaller than those of the titania-coated PS spheres as a result of calcination-induced shrinkage. The composite and hollow spheres were characterized by scanning electron microscopy, transmission electron microscopy and electron diffraction measurements. These core-shell organic-inorganic spheres and hollow ceramic spheres may have wide applications in catalysts, adsorbents, lightweight fillers, capsules, etc.     

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.     

Submicrometer-sized hollow nickel spheres synthesized by autocatalytic reduction

A facile method to fabricate submicrometer-sized hollow nickel spheres by autocatalyzing the redox reaction around a sacrificial colloidal particle surface is presented in this paper. The size distribution of these spheres can be controlled by regulating the concentration of the alkali solution. The hollow nickel particles were characterized by field emission scanning electron microscopy, transmission electron microscopy and X-ray powder diffraction. The hollow spheres produced by this process may have potential applications in many fields, including chemistry, biotechnology and materials science.     

Bi_2MoO_6空心球的水热沉淀法制备及其光催化性能

以葡萄糖为前躯体,采用水热法制备胶体碳球,以其为模板通过水热沉淀法制备C/Bi2MoO6核壳结构,然后在350℃空气中煅烧,获得了具有良好光催化性能的Bi2MoO6空心球.通过SEM、XRD、FT-IR和BET等测试方法对该催化剂进行了表征;并对其形成机理及反应过程进行了初步探讨,以亚甲基蓝作为被降解物质,研究了其光催化活性。结果表明,Bi2MoO6空心球是由纳米晶粒组成的,壁厚约为30～50nm,平均直径约为0.6～0.8μm,采用胶体碳球作模板时制得的Bi2MoO6空心球比表面积为11.315m2/g,而直接合成的粉体比表面积为3.378m2/g。在黑管灯照射下,2.5h亚甲基蓝的降解率达到了91.95%。     

Cetyltrimethyl ammonium bromide assisted hydrothermal growth of hematite hollow cubes

Hematite hollow cubes have been prepared by forced hydrolysis of ferric chloride solutions under hydrothermal conditions. The effects of reaction time, reaction temperature and cetyltrimethyl ammonium bromide on the transformation process from akageneite to hematite were investigated in detail. The products were characterized by X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. It is found that cetyltrimethyl ammonium bromide was a critical factor influencing the phase transformation process of akageneite and the final morphology of the as-prepared products. With cetyltrimethyl ammonium bromide, hematite hollow cubes and porous spheres were obtained. Otherwise only dense cubes were observed even prolonging reaction time or increasing reaction temperature. The mechanism was proposed.     

Fabrication of hollow silica spheres in an ionic liquid microemulsion

Hollow silica spheres have been successfully synthesized by using the ionic liquid microemulsion droplets as the template. The morphology and microstructures of the silica spheres were investigated by scanning electron microscopy (SEM), high-resolution transmission electron microscope (HRTEM), and Nitrogen adsorption-desorption measurements. The obtained images showed that the average size of the silica spheres was almost between 150 and 300 nm. The Nitrogen adsorption-desorption investigation on the silica spheres indicated the amorphous structure on the interface. Both of these two results provide us new insights into this novel template and hollow silica spheres were for the first time prepared free of additional acid and alkali conditions. The possible mechanism for the formation of silica spheres has been put forward and discussed in details.     

水热法合成α-氧化铝空心微球

以葡萄糖和硝酸铝为原料,采用水热法合成大小及壁厚可控的α-氧化铝空心微球。通过扫描电子显微镜(SEM)、傅立叶红外光谱分析仪(FT-IR)、X射线衍射(XRD)、热分析(TG-DSC)等手段对合成产品进行表征。结果表明:得到的氧化铝空心微球分散性较好,可通过调节加入的葡萄糖浓度及硝酸铝量,得到大小及壁厚不同的氧化铝空心球,烧结温度对微球粒径大小影响不大,当烧结温度上升900℃时,壳层结构由不定形态变为γ-Al2O3,当烧结温度上升到1 100℃时,可得到α-Al2O3氧化铝空心微球。     

Characterisation of hollow Russian doll microspheres

Poly(1-methylpyrrol-2-yl)squaraine (PMPS) particles have been characterised using SEM. The PMPS particles were used as templates to prepare bare silica and iron–silica hollow spheres, which were characterised using TEM and SEM. The PMPS particles and the hollow spheres are not uniformly sized and are agglomerated. The hollow spheres with larger diameters (>900 nm) contain an internal ‘Russian doll’ structure. The iron–silica hollow spheres are fused to one another, and the hollow spheres have a heterogeneous wall thickness. The silica and iron–silica hollow spheres both aggregate by size. There are two different size populations (for the diameter) of the bare silica and iron–silica hollow spheres. The smaller silica spheres have thinner walls compared to the larger silica hollow spheres. The larger silica hollow spheres and the iron–silica hollow spheres have similar wall thicknesses. The iron compound in the iron–silica hollow spheres has an oxidation state of 3+ and is crystalline.     

A novel route to synthesis Aluminum silicate hollow spheres having ZSM-5 structure in absence of template

A novel route to synthesize Aluminum silicate hollow spheres with thick walls having ZSM-5 structure without using any template at 150 °C was presented. X-ray diffraction (XRD), Scanning electron microscopy (SEM), TG/DTA, FT-IR and nitrogen adsorption were employed to characterize the morphology and microstructures of the as-prepared silica hollow spheres. Experimental results indicated that the hollow spheres had an average diameter of nearly 200 nm with a surface area of 342 m²/g.     

双金属催化剂Ni-Co/SiO2空心球的可控制备及催化性能

以二氧化硅为模板, 采用牺牲模板/界面反应法制备具有介孔结构的碱式硅酸镍钴空心球。采用透射电子显微镜(TEM)、X 射线衍射(XRD)、氮气吸脱附曲线(BET)和程序升温还原(TPR)等方法, 对样品的结构和形貌进行了表征, 探索了碱式硅酸镍钴空心球还原规律, 并研究了双金属催化剂Ni-Co/SiO₂的催化性能。研究发现, 140℃下反应6 h, 产物为核壳结构, 反应12 h时变为空心球结构; 在氢气气氛中800℃下反应5 h, 碱式硅酸镍钴被完全还原为Ni-Co/SiO₂, 还原前后形貌基本不变, 但比表面积有所减小, 孔径增大。Ni-Co/SiO₂空心球用于催化硝基苯加氢反应1 h后, 硝基苯的转化率为67%, 比商用Raney Ni 提高约28%。     

Hydrothermal synthesis of hollow MoS2 microspheres in ionic liquids/water binary emulsions

Hollow molybdenum disulfide (MoS₂) microspheres were synthesized in ionic liquids (1-butyl-3-methylimidazolium chloride, [BMIM]Cl)/water binary emulsions by the hydrothermal method at 180 °C for 24 h. The optimum value of volumetric proportions (ILs/water) equaled 1:9. The structure and morphology of products were characterized by means of X-ray powder diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The experimental results gave the evidences that the sample is consists of hollow spheres 1.8 - 2.1 μm in diameter, and there are much sheet-like structures on the surface of hollow MoS₂ microspheres. In addition, ILs could be collected and reused for subsequent reactions.     

Development of a simple method for the preparation of novel egg-shell type Pt catalysts using hollow silica nanostructures as supporting precursors

A simple method for the preparation of novel egg-shell type platinum catalysts was developed and achieved by utilizing unique hollow silica nanostructures, i.e., hollow silica nanospheres and nanotubes, as supports. The observation by transmission electron microscopy indicated that the well-dispersed hollow silica supported Pt catalysts with a Pt particle diameter of 8-14 nm can be successfully prepared by wet impregnation process and heat treatment. The Pt-loaded hollow silica nanostructures were also characterized by inductively coupled plasma, X-ray diffraction, specific surface area, Fourier transformation infrared spectroscopy, X-ray photoelectron spectroscopy and energy dispersive spectroscopy. It was thus demonstrated that a higher Pt loading amount (0.392%) could be obtained under the same conditions except the addition of ammonia, which was found to be more effective than that (0.061%) with the addition of HCl in the immobilization of Pt. In addition, the effect of soaking time, Pt precursor concentration and calcination temperature on the loading of Pt in hollow silica nanostructures were investigated as well.     

Template-free fabrication of TiO2 hollow spheres and their photocatalytic properties

Submicrometer-sized anatase TiO(2) hollow spheres were fabricated through a template-free solvothermal route using TiCl(4) as a raw material and a mixture of alcohols-acetone as solvent. Control of the hollow spheres' size was achieved by adjusting the ratio of alcohols to acetone. Products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution TEM, X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and thermogravimetric (TG) analysis. It was found that the formation process of the TiO(2) hollow spheres might include the hydrolysis of Ti(IV) with the water formed from the solvothermal etherification reaction, the aggregation of the anatase TiO(2) nanoparticles, and the Ostwald ripening. Furthermore, the as-prepared TiO(2) hollow nanostructures exhibited good photocatalytic activity for the degradation of phenol.     

Controllable fabrication of hollow TiO2 spheres as sustained release drug carrier

TiO₂ hollow spheres with controllable size were successfully synthesized through a hydrothermal silica etching method; SiO₂ cores were easily removed without the use of a toxic reagent. The parameters for the synthesis of SiO₂ cores and TiO₂ hollow spheres, including stirring time, ammonia concentration, tetrabutyl titanate content, hydrothermal time, and reflux time, were systematically investigated. SiO₂ cores and TiO₂ hollow structure were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectra (EDX), X-ray photoelectron spectroscopy (XPS), and N₂ adsorption-desorption isotherms. The results revealed that the mean diameter of SiO₂ was ∼280 nm when the concentration of ammonia was 4.8 M and the stirring time was 0.5 h. For hollow TiO₂, when the operation process was optimized (ammonia volume 0.35 mL, TBOT addition 1.5 mL, hydrothermal time 3 h, and reflux time 3 h), the average size and the shell thickness were 270 and 100 nm, respectively. The process exhibited a high drug loading capacity (33.12 ± 0.01%) and encapsulation rate (99.03 ± 0.24%) due to its high specific surface area of 121.62 m²·g⁻¹. In addition, TiO₂ hollow spheres displayed pH-responsive sustained-controlled drug release behavior in vitro which released 80% of doxorubicin at 5.0 pH within 120 h, its release kinetic showed that it fits well with Zero-order kinetic equation, demonstrating that DOX·HCl/hollow TiO₂ maintains constant release rate, and the investigation of blood compatibility showed that the hemolysis rate of hollow TiO₂ did not exceed 3% in the concentration range of 100 and 4000 μg/mL, further confirming that prepared hollow TiO₂ is a relatively safe medical inorganic material.     

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 PbS hollow spheres with single crystal-like electron diffraction patterns

PbS hollow spheres were successfully prepared by a sodium citrate-assisted hydrothermal process at 120 degrees C for 12 h, employing lead acetate trihydrate, thiourea and sodium citrate as precursors. The diameter of PbS hollow spheres is 200-400 nm, which is composed of about 50-80 nm nanoparticles. The synthesized product was characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), Fourier transform-infrared (FT-IR) spectroscopy, ultraviolet-visible spectrometer (UV-vis) and near-infrared absorption spectrometer (NIR). The effects of the reaction conditions on morphologies of PbS structures were investigated. Star-shaped and flat PbS crystals were obtained by changing some experiment conditions. The results show that temperature, sodium citrate concentration, sulfur sources and solvent play key roles on the final morphologies formation of PbS crystals. Especially, ED result indicates that PbS hollow spheres hold single crystal-like electron diffraction patterns. And the possible formation mechanism of hollow spheres was proposed.     

Spherical mesoporous silica templated with ionic liquid and cetyltrimethylammonium bromide and its conversion to hollow spheres

Spherical mesoporous silica was synthesized using a mixture of 1-methyl-3-octylimidazolium chloride and cetyltrimethylammonium bromide as the structure-directing agent. The obtained silica was characterized by X-ray powder diffraction, scanning electron microscope, transmission electron microscope, and ¹³C NMR spectroscopic techniques. The results show that the spherical silica possesses worm-like mesopores and larger mesopores, with the sizes about 6-50 nm. It is very interesting that the spherical mesoporous spheres were converted to hollow ones after reflux in boiling water. The treatment results in the generation of the hollow interior by dissolving the silica core. Meanwhile, the silica shell is well retained, which is confirmed by SEM and TEM images.     

氧化铟空心球的合成和光致发光性能研究

在180℃水热处理葡萄糖和铟盐的混合物,然后在空气中烧结制备了氧化铟空心球.利用场发射扫描电镜、透射电镜、X射线衍射等对其形貌和结构进行分析.结果表明,氧化铟空心球为多孔结构,其粒径为800～1000nm,由密堆积的纳米粒子组装而成.讨论了氧化铟空心球的形成机制和光致发光特性.