Morphology Of Hollow Spheres Research Articles

Efficient hydrogen production by water-splitting over Pt-deposited C–HS–TiO2 hollow spheres under visible light

A Pt-deposited C–HS–TiO2 hollow sphere prepared through a simple template approach as well as their implementation as a photocatalyst for water splitting. The obtained Pt-deposited C–HS–TiO2 hollow spheres are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), UV–vis absorption spectrum (UV–vis), and transmission electron microscope (TEM). The results show that hollow spherical morphology was successfully synthesized. Compared with commercial P-25 TiO2 and C–TiO2 hollow sphere, Pt-deposited C–HS–TiO2 hollow spheres exhibit significant improvement in photoactivity under the visible light irradiation. It can be attributed to the enhanced visible light absorption by the deposited Pt. Furthermore, 1.0 wt% Pt/C–HS–TiO2 presents an ultra-high photocatalytic water splitting activity. The maximum production rate of hydrogen at a reaction temperature of 25 °C is measured as 2857 µmol/h. In addition, 1.0 wt% Pt/C–HS–TiO2 exhibits excellent long-term stability and durability of photocatalytic activity. The rate of visible light water splitting has no significant change. After 22 days of operation, an 8% loss of the initial activity occurs. Finally, the probable mechanism of hydrogen production by water splitting under visible light irradiation is proposed in this study.

Porous hollow carbon spheres: facile fabrication and excellent supercapacitive properties

A facile method has been developed for the fabrication of hierarchically porous hollow carbon spheres (HCS) by using K2CO3 impregnated starch as the raw material. The shell of HCS is highly graphitized and abundant in oxygen-containing surface groups. The presence of K2CO3 activates the carbon matrix with numerous hierarchical pores during heat treatment. A slow heating rate is the key to fabricate hollow carbon spheres. The by-product of water possibly serves as the template and promotes the formation of HCS. The carbonization duration plays an important role. Extending the heating time enhances both the porosity and the graphitization degree of the shell. The HCS–10 exhibits a large specific surface area of 517.5m2 g−1 and pore volume of 0.265cm3g–1. The unique hollow spherical morphology and suitable porous structure bestow HCS–10 excellent supercapacitive performances. Derived from the CV curves, a symmetrical supercapacitor of HCS–10 exhibits a maximum specific capacitance of 317Fg–1 at a slow scan rate of 5mVs–1 and a high rate capacitance of 222.2Fg–1 at a fast scan rate of 300mVs–1 with the potential window of 1.0V by using 6M KOH solution as the electrolyte. Galvanostatic charge-discharge displays a high capacitance of 265.4Fg–1 at 1Ag–1 and a high rate capacitance of 137.9Fg–1 even at a high current density of 100Ag–1. The high capacitance retention of 99.6 % over 25000 charge/discharge cycles further confirms the cycling stability and rate performance with varied current densities of 1, 2, 5, 10 and 1Ag–1. Also, the presence of oxygen-containing groups broadens the working voltage up to 1.5V. Notably, the highest power density of 100kWkg–1 is achieved at current density of 100Ag−1 and working voltage of 1.0V. Cycling tests deliver a compatible data at 1.4V and 10Ag–1, a high capacitance of 286Fg–1 with a high energy density of 77.88Whkg–1 and a large power density of 14kWkg–1. The excellent supercapacitive performances of HCS–10 will possibly fit the growing demands for the energy storage devices.

Preparation of aniline from photocatalytic reduction of nitrobenzene using Pt/Nd2O3 nanocomposite

In this manuscript, a template method was used to synthesis Pt-doped Nd2O3 nanostructures with controlled Pt doping contents. The characterizations illustrated that the obtained samples have ultra high surface area (190 m2/g), high crystallinity, small grain size (20 nm) and hollow spherical like morphology. Also, the band gap of the Pt-doped Nd2O3 nanostructures can be controlled by controlling the Pt contents. The photocatalytic activity of the Pt-doped Nd2O3 nanostructures samples was studied by studying the reduction of nitrobenzene into aniline using visible light irradiation. The photocatalytic performance of Nd2O3 was enhanced by Pt doping. This can be attributed to the fact that the trapping effect of the Pt-doped Nd2O3 nanostructures and the red shift of absorption edge. The study result provides an effective method to create different photocatalysts with enhanced visible-light-driven photocatalytic performance.

3D computational reconstruction of tissues with hollow spherical morphologies using single-cell gene expression data.

Single-cell gene expression analysis has contributed to a better understanding of the transcriptional heterogeneity in a variety of model systems, including those used in research in developmental, cancer and stem cell biology. Nowadays, technological advances facilitate the generation of large gene expression data sets in high-throughput format. Strategies are needed to pertinently visualize this information in a tissue structure-related context, so as to improve data analysis and aid the drawing of meaningful conclusions. Here we describe an approach that uses spatial properties of the tissue source to enable the reconstruction of hollow sphere-shaped tissues and organs from single-cell gene expression data in 3D space. To demonstrate our method, we used cells of the mouse otocyst and the renal vesicle as examples. This protocol presents a straightforward computational expression analysis workflow, and it is implemented on the MATLAB and R statistical computing and graphics software platforms. Hands-on time for typical experiments can be <1 h using a standard desktop PC or Mac.

Controllable preparation of CeF 3 :Tb 3+ nanostructures with different morphologies from an ionic liquid-based extraction system

Abstract The extraction system is a promising environment to prepare nanomaterials with diverse advantages, but its controllability of the size and shape of the products is still relatively weak. Here, CeF 3 :Tb 3+ nanostructures with the morphologies of hollow spheres and nanoplates were controllably prepared using a third phase from an ionic liquid (IL)-based extraction system at an aqueous–organic interface. The shape of the CeF 3 :Tb 3+ nanostructure is controlled from hollow sphere to nanoplate by decreasing the size and amount of the big reverse micelles in the third phase through the addition of iso-propanol. Moreover, the luminescent properties of the as-prepared nanostructures were investigated.

Unconventional Dexter–Silverton Type Manganese Heteropolytungstate [Mn7(MnW12O42(OH)4·8H2O)] Hollow Microsphere: Synthesis, Crystal Structure, Growth Mechanism, and Optical Property Study

An uncommon yet highly symmetric crystal form of a Mn-based heteropolytungstate (Mn-HPT), Mn7(MnW12O42(OH)4)·8H2O, has been synthesized by a unique solvothermal method at 180 °C for 6 h. The nature of the solvent (water/ethanol = 50/50 by volume) and the presence of citric acid were the key reasons for the formation of the Mn-HPT phase and its hollow spherical morphology under the said experimental conditions. Combined powder X-ray diffraction analysis and field emission scanning electron miroscopy (FESEM) analysis reveals that the structure (cubic, space group Im3) consisted of [MnW12O42]10– polyanion with Mn in a central 12-coordinated cavity, which cross-linked three dimensionally with other MnO6 octahedra, to form the characteristic rhombododecahedron shaped particles of size ∼150 nm. Each polyanion was made of six pair of face shared WO6 dimers (W2O9) with mean W···W separation of 2.98 A. The WO6 octahedrons were tilted to an O–W–O angle of 99.1° with four different types of W–O bonds. The structure ...

Synthesis of B-doped hollow carbon spheres as efficient non-metal catalyst for oxygen reduction reaction

Synthesis scheme and morphology of B-doped hollow carbon spheres applied as an efficient non-metal catalyst for oxygen reduction reaction.

Synthesis of Fe-doped WO3 nanostructures with high visible-light-driven photocatalytic activities

In this paper, the Fe-doped WO3 nanostructures with precisely controlled Fe doping contents are obtained by using a template method. The characterizations obviously show that the as-prepared samples have hollow spherical like morphology, small grain size (10nm), high crystalline quality, and ultrahigh surface area (225m2/g). Furthermore, the band gap of the Fe-doped WO3 nanostructures is facilely tunable by controlling the Fe contents. And the density-functional theory (DFT) calculation reveals that the formation of impurity band in the band gap narrows the band gap of the Fe-doped WO3 nanostructures. The photocatalytic activity of WO3 nanostructures could be remarkably enhanced by doping the Fe impurity. This can be attributed to the fact that the red shift of absorption edge and the trapping effect of the Fe-doped WO3 nanostructures. The research result provides a general and effective method to synthesize different photocatalysts with enhanced visible-light-driven photocatalytic performance.

Solvothermal synthesis and characterization of ceria with solid and hollow spherical and multilayered morphologies

Ceria powders with different morphologies were synthesized using a facile template-free solvothermal process combined with calcination. The influence of solvothermal temperature and time on the powder was studied. Solid spheres, hollow spheres, and multilayered structures were controlled by adjusting the solvothermal conditions. The possible mechanisms for the formation of the precursors under the solvothermal conditions employed and the evolution of the powder from solid spherical to multilayered structures were discussed. Ethylene glycol played a key role in the morphology evolution of the powder. Cerium catalyzed the Guerbet-like reaction and reacted with ethylene glycol to produce ceria (CeO2), Ce(HCOO)3, and Ce(OH)CO3. The redox-assisted dissolution–recrystallization process significantly contributed to the morphology transformation from solid spheres to multilayered structures. Moreover, the samples synthesized at different temperatures for 24h possessed excellent adsorption capacities towards the removal of acid orange 7 when compared with commercial ceria.

Morphology Design of IRMOF-3 Crystal by Coordination Modulation

A one-pot synthesis design on shape-controlled growth of Zn-based isoreticular metal–organic framework (i.e., IRMOF-3) was carried out in this work with the controllable crystal morphological evolution from simple cubes to several complex shapes. A new synthetic protocol was devised where poly(vinylpyrrolidone) (PVP), noble metal source (AgNO3), mixed solvents (N,N-dimethylformamide (DMF)–ethanol mixture) and tetramethylammonium bromide (TMAB) were mutually introduced to the reaction medium as surfactant, adjuvant, accelerator, and structure-directing agent (SDA), respectively. Meanwhile, the crystallization process was investigated by a series of time-dependent experiments. Indeed, the added modulators and crystallization time were able to regulate the growth and thus the morphology of the final products. The resulting homogeneous IRMOF-3-Ag-n materials with unique and novel crystal morphologies were characterized via scanning electron microscopy (SEM), X-ray powder diffraction (XRD), thermogravimetric and differential thermal analyses (TG-DTA), transmission electron microscopy (TEM), infrared spectrum (IR), and optical microscope characterizations. Various shapes of IRMOF-3-Ag-n crystals as sorbents for capturing dibenzothiophene (DBT) were evaluated. Among all the morphology-controlled samples, IRMOF-3-Ag-5 with hollow sphere morphology was demonstrated to show the highest DBT capture capacity due to its unique morphology.

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 synthesis, magnetic and optical properties of double-shelled Co3O4 hollow microspheres

Double-shelled Co3O4 hollow spheres are successfully synthesized by chemically induced self-assembly in the hydrothermal environment. The morphology, chemical composition, and crystalline structure of the double-shelled Co3O4 hollow spheres are characterized by different techniques, such as powder X-ray diffraction (PXRD), Raman spectrum, X-ray photoelectron spectrum (XPS), field emission scanning electron microscope (FESEM), and high resolution transmission electron microscope (HRTEM) with selected area electron diffraction (SAED). Magnetic measurements and optical spectra suggest the double-shelled Co3O4 hollow spheres exhibit close to a weak ferromagnetic behaviour and enhanced photogenerated carrier separation. Since this synthetic route is simple, convenient, and “green”, it is possible to extend this synthetic method to preparation of a wide range of the multishelled hollow spheres of metal oxides for semiconductor device applications.

Hierarchical ZnO hollow microspheres with strong violet emission and enhanced photoelectrochemical response

Hierarchical ZnO hollow microspheres were prepared via a carbon microspheres-templated approach, and their microstructures were analyzed by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The as-prepared ZnO products show well-defined hollow spherical morphology with a size of 2–4µm. The thickness of ZnO shells is around 100nm, and they are assembled by numerous nanoparticles of 30–50nm. The optical properties of the ZnO hollow microspheres were studied, and they exhibit a narrowed band gap (2.96eV) and a sharp violet emission at 434nm. Moreover, the ZnO hollow microspheres show a stable and greatly enhanced photocurrent response to visible light, which can be attributed to the hierarchical structures and the narrowed band gap resulted from the carbothermic process.

Visible light catalysis-assisted assembly of Ni(h)-QD hollow nanospheres in situ via hydrogen bubbles.

Hollow spheres are one of the most promising micro-/nanostructures because of their unique performance in diverse applications. Templates, surfactants, and structure-directing agents are often used to control the sizes and morphologies of hollow spheres. In this Article, we describe a simple method based on visible light catalysis for preparing hollow nanospheres from CdE (E = Te, Se, and S) quantum dots (QDs) and nickel (Ni(2+)) salts in aqueous media. In contrast to the well-developed traditional approaches, the hollow nanospheres of QDs are formed in situ by the photogeneration of hydrogen (H2) gas bubbles at room temperature. Each component, that is, the QDs, metal ions, ascorbic acid (H2A), and visible light, is essential for the formation of hollow nanospheres. The quality of the hollow nanospheres depends on the pH, metal ions, and wavelength and intensity of visible light used. Of the various metal ions investigated, including Cu(+), Cu(2+), Fe(2+), Fe(3+), Ni(2+), Mn(2+), RuCl5(2-), Ag(+), and PtCl4(2-), Ni(2+) ions showed the best ability to generate H2 and hollow-structured nanospheres under visible light irradiation. The average diameter and shell thickness of the nanospheres ranged from 10 to 20 nm and from 3 to 6 nm, respectively, which are values rarely reported in the literature. Studies using high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), inductively coupled plasma-mass spectroscopy (ICP-AES), and steady-state and time-resolved spectroscopy revealed the chemical nature of the hollow nanospheres. Additionally, the hollow-structured nanospheres exhibit excellent photocatalytic activity and stability for the generation of H2 with a rate constant of 21 μmol h(-1) mg(-1) and a turnover number (TON) of 137,500 or 30,250 for CdTe QDs or nickel, respectively, under visible light irradiation for 42 h.

Preparation of ZnO hollow spheres with different surface roughness and their enhanced gas sensing property

ZnO hollow spherical samples with different surface roughness have been synthesized using a one-step, template-free hydrothermal method. Materials characterization has included XRD, SEM, TEM, XPS and XRF. It was found that the surface roughness of the ZnO hollow spheres can be tuned from rough to smooth via regulating trisodium citrate concentration during the synthesis. When 2mM of trisodium citrate was used, ZnO hollow spheres showed the roughest surface morphology. With increasing the citrate concentration from 2 to 6mM, the resultant ZnO hollow sphere morphology became increasingly denser and smoother. When the citrate concentration was further increased to 8mM, however, the morphology became rough again. Sensors fabricated using the ZnO hollow spheres were characterized by the response to alcohol vapor. The roughest sample gave the best sensor response toward 10–500ppm alcohol vapor, about 11–16 times higher than the reference one prepared without citrate. This corresponds to a remarkable sensor response as high as 402 and an extrapolated detection limit 0.5ppm. The reasons behind the improvements in sensor performance are discussed.

Hollow Spheres of Iron Carbide Nanoparticles Encased in Graphitic Layers as Oxygen Reduction Catalysts

Nonprecious metal catalysts for the oxygen reduction reaction are the ultimate materials and the foremost subject for low-temperature fuel cells. A novel type of catalysts prepared by high-pressure pyrolysis is reported. The catalyst is featured by hollow spherical morphologies consisting of uniform iron carbide (Fe3 C) nanoparticles encased by graphitic layers, with little surface nitrogen or metallic functionalities. In acidic media the outer graphitic layers stabilize the carbide nanoparticles without depriving them of their catalytic activity towards the oxygen reduction reaction (ORR). As a result the catalyst is highly active and stable in both acid and alkaline electrolytes. The synthetic approach, the carbide-based catalyst, the structure of the catalysts, and the proposed mechanism open new avenues for the development of ORR catalysts.

Hollow Spheres of Iron Carbide Nanoparticles Encased in Graphitic Layers as Oxygen Reduction Catalysts

AbstractNonprecious metal catalysts for the oxygen reduction reaction are the ultimate materials and the foremost subject for low‐temperature fuel cells. A novel type of catalysts prepared by high‐pressure pyrolysis is reported. The catalyst is featured by hollow spherical morphologies consisting of uniform iron carbide (Fe3C) nanoparticles encased by graphitic layers, with little surface nitrogen or metallic functionalities. In acidic media the outer graphitic layers stabilize the carbide nanoparticles without depriving them of their catalytic activity towards the oxygen reduction reaction (ORR). As a result the catalyst is highly active and stable in both acid and alkaline electrolytes. The synthetic approach, the carbide‐based catalyst, the structure of the catalysts, and the proposed mechanism open new avenues for the development of ORR catalysts.

Morphologic control of Sb-rich Sb2Se3 to adjust its catalytic hydrogenation properties for p-nitrophenol

Sb-rich Sb2Se3 with hollow sphere morphology is an efficient catalyst for the hydrogenation of p-nitrophenol.

Effect of Solvents on Morphology of Hollow Nickel-Silica Composite Spheres and Their Catalytic Performance for Hydrolytic Dehydrogenation of Ammonia Borane

We study the effect of solvents on morphological and/or structural properties and catalytic activity of hollow nickel-silica composite spheres for hydrolytic dehydrogenation of ammonia borane. Nickel-silica composite shells were coated on polystyrene (PS) templates via sol-gel reaction with L(+)-arginine as the promoter of the sol-gel reaction followed or in parallel with the dissolution of the PS templates in the same medium to form hollow spheres. From the transmission electron microscopy (TEM) images, nickel-silica composite shells were formed for 1.5 h, and the surface roughness of the shells increases with the increase of aging time in methyl alcohol, while the shells were formed via the formation of aggregates of irregular shape in ethyl alcohol and 2-propyl alcohol. From the angle attenuated total reflectance infrared (ATR-IR) spectra, the order of dissolution rate of PS templates is 2-propyl alcohol > ethyl alcohol > methyl alcohol. These results indicate that the shells are formed before the dissolution of PS templates in methyl alcohol, while in ethyl alcohol and 2-propyl alcohol, nickel-silica composite shells was formed in parallel with dissolution of PS templates via the formation of aggregates of irregular shape. From the results of N

Influence of Preparation Conditions on the Morphology and Catalytic Activity of Hollow Spheres of Copper-Cerium Composite Oxide for Oxidation of Carbon Monoxide

The present study investigated the influence of preparation conditions of hollow spheres of copper-cerium composite oxide on the morphology and catalytic activity for oxidation of carbon monoxide. The hollow spheres were obtained by a hydrothermal method using silica templates, and the homogeneity of the hollow spheres depended on the amount of urea used during preparation. X-ray diffraction studies indicated that the dispersion of CeO2 in the copper-cerium composite oxide increased with the addition of urea during preparation. In addition, X-ray photoelectron spectroscopy studies indicated that the amount of surface copper also increased with the addition of urea. The hollow spheres prepared with urea showed a higher catalytic activity for oxidation of carbon monoxide than the sample prepared without urea due to the morphological homogeneity, dispersion of CeO2, and surface composition of Cu species.