Synthesis Of Microspheres Research Articles

Aluminosilicate Microsphere Synthesis in Plasma Flow

The paper presents theoretical and experimental results on the synthesis of ash-based microspheres using the high-temperature plasma treatment. The dynamic motion of particles and their melting are considered depending on the initial porosity of the raw material modified by 3200K plasma treatment. Physicochemical studies relate to the original raw material and microspheres produced therefrom.

Nanoaramid Dressed Latex Particles: The Direct Synthesis via Pickering Emulsion Polymerization.

The direct synthesis of polymer microspheres modified by aramid nanofibers (ANFs) is an interesting challenge. This work describes a simple aqueous process to prepare polystyrene (PS)/ANF composite microspheres, where the specific ANF network was "dressed" on PS. ANF was derived from the copolymerization of terephthaloyl chloride, p-phenylene diamine, and methoxypolyethylene glycol and could be dispersed in water stably. We applied the as-synthesized ANF as a Pickering emulsifier in the o/w emulsion of styrene monomer. Radical polymerization was subsequently initiated in the Pickering emulsion system. The combination of ANF with polymer spheres was revealed by scanning electron microscopy (SEM) and thermal gravity analysis. The role of ANF in the monomer emulsion as well as in the polymerization was studied through SEM, optical microscopy, optical stability analyzer, and pulse nuclear magnetic resonance combined with the polymerization kinetic analysis. Moreover, we investigated the effects of other synthesis parameters, such as monomer type, monomer content, pH value, and salt concentration.

Facile synthesis of MnO2-embedded flower-like hierarchical porous carbon microspheres as an enhanced electrocatalyst for sensitive detection of caffeic acid

Tailored designs/fabrications of hierarchical porous advanced electrode materials are of great importance for developing high-performance electrochemical sensors. Herein, we demonstrate a simple and low-cost in situ chemical approach for the facile synthesis of MnO2-embedded hierarchical porous carbon microspheres (MnO2/CM). By the characterizations of scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction and energy dispersive spectroscopy, we evidenced that the synthesized product were flower-like carbon microspheres (CM) assembled by the bent flakes with thickness of about several nanometers and MnO2 nanorods were highly dispersed and successfully decorated on the CM layers, resulting in a rough surface and three-dimensional microstructure. The greatest benefit from the combined porous CM with MnO2 nanorods is that the MnO2/CM modified electrode has the synergetic catalysis effect on the electro-oxidation of caffeic acid, leading to the remarkable increase in the electron transfer rate and significant decrease in the over-potential for the caffeic acid oxidation in contrast to the bare electrode and CM modified electrode. This implies that the prepared MnO2/CM can be employed as an enhanced electrocatalyst for the sensitive detection of caffeic acid. Under the optimum conditions, the anodic peak current of caffeic acid is linear with its concentration in the range of 0.01–15.00 μmol L−1, and a detection limit of 2.7 nmol L−1 is achieved based on S/N = 3. The developed sensor shows good selectivity, sensitivity, reproducibility, and also excellent recovery in the detections of real samples, revealing the promising practicality of the sensor for the caffeic acid detection.

Synthesis and characterization of hollow glass microspheres reinforced magnesium alloy matrix syntactic foam

In the present scenario, a considerable importance is being given to find newer materials for marine applications. An endeavour has been made to synthesis hollow glass microspheres reinforced magnesium matrix (AZ91D/HGM) syntactic foams and analyze its mechanical properties for such applications in the present study. The 40 μm size reinforcement particles have been added with matrix under dissimilar mass fractions of 15%, 20% and 23% to investigate the interfacial reaction, compressive properties, hardness, density, porosity, corrosion resistance. From the experimental investigation, it has been inferred that the density of foams and corrosion rate have been considerably reduced owing to increase in reinforcement mass fraction. It has also been observed that the developed syntactic foam has produced higher compressive strength due to its cushion effect and higher plateau stress. From the porosity phase analysis, it has been found that the porosity has been increased with increasing mass fraction percentage. From the composition structural analysis, Mg17Al12 has been observed as main interfacial reaction between the microsphere and matrix alloy.

Size-controlled synthesis, growth mechanism and magnetic properties of cobalt microspheres

Monodispersed cobalt microspheres with remarkably uniform morphology and tunable size have been successfully synthesized via a facile and effective solvothermal route. It is found that sodium hydroxide has a great influence on the size and shape of the resulting cobalt powders. Through adjusting the molar ratio of NaOH to Co2+, the size of cobalt microspheres can be precisely manipulated. In addition, the magnetic properties of the as-synthesized samples demonstrate that cobalt microspheres exhibit ferromagnetic property related to their sizes. More importantly, this study not only provides a facile and effective strategy to prepare the cobalt microspheres with tunable sizes, but also gives a reference for the synthesis of other magnetic functional materials.

Correlation between types of defects/vacancies of Bi2S3 nanostructures and their transient photocurrent

Crystalline nanostructures possess defects/vacancies that affect their physical and chemical properties. In this regard, the electronic structure of materials can be effectively regulated through defect engineering; therefore, the correlation between defects/vacancies and the properties of a material has attracted extensive attention. Here, we report the synthesis of Bi2S3 microspheres by nanorod assemblies with exposed {211} facets, and the investigation of the types and concentrations of defects/vacancies by means of positron annihilation spectrometry. Our studies revealed that an increase in the calcined temperature, from 350 to 400 °C, led the predominant defect/vacancy densities to change from isolated bismuth vacancies (VBi) to septuple Bi3+–sulfur vacancy associates (VBiBiBiSSSS). Furthermore, the concentration of septuple Bi3+–sulfur vacancy associates increased as the calcined temperature was increased from 400 to 450 °C. The characterized transient photocurrent spectrum demonstrates that the photocurrent values closely correlate with the types and concentrations of the predominant defects/vacancies. Our theoretical computation, through first principles, showed that V BiBiBiSSSS strongly absorbs I2(sol), easily desorbs I−(sol), and enhances the electrocatalytic activity of the nanostructures.

Synthesis and catalytic oxidation property of titanium-zirconium mixed oxide microsphere as well as titanium oxide microcube

Titanium-zirconium mixed oxide microspheres and titanium oxide microcubes have been prepared by using sol-gel processes, which are further modified by chiral sulfonyl chloride in order to improve their activities for oxidation of alkenes. Characterizations reveal that the titanium-zirconium microspheres are solid, but substitution of zirconium with l-(+)-sodium tartrate produces microcubes featuring titanium oxide, which has a hollow structure. In catalysis, both microspheres and microcubes show satisfactory conversions of alkenes, as well as promising outputs of high-valued oxidized products. The linkage of chiral sulfonyl chloride looks efficient for improving catalysis. There is a kind of synergy between metal oxide and attached ligand, which plays a key role in catalytic outputs. Lastly, hydrogen peroxide appears to be a promising oxidant for transformation of aliphatic alkenes. This work puts forward micron-sized titanium materials with interesting structures, which also exhibit satisfactory activity for oxidation of alkenes.

Novel application of red mud: Facile hydrothermal-thermal conversion synthesis of hierarchical porous AlOOH and Al2O3 microspheres as adsorbents for dye removal

Originated from the by-product of alumina production, red mud has caused severe impact on environment. To cope with the increasingly urgent environmental issue, red mud has now been utilized for the first time to obtain the hierarchical porous γ-AlOOH/γ-Al2O3 microspheres as high efficient adsorbents for dye removal. The NaAlO2 leached from the red mud is hydrothermally treated at 150°C for 6.0h in the presence of urea, leading to hierarchical porous γ-AlOOH microspheres, with a specific surface area of 76.8m2g−1, 93% of which have a diameter within the range of 3.5–7.5µm. The subsequent mild thermal conversion at 600°C for 2.0h results in the hierarchical porous γ-Al2O3 microspheres with a specific surface area of 158.6 m2 g−1, and ca. 92% of which bear a size of 3.0–7.0µm. The porous γ-AlOOH and γ-Al2O3 microspheres exhibit excellent adsorption for MB with the maximum adsorption capabilities of 953.0mgg−1 and 1587.6mgg−1, respectively, and the latter is distinctly higher than most of the reported results. The possible formation is proposed, and the adsorption mechanism is discussed. The present work provides a new insight into the comprehensive utilization of the red mud as great potential adsorbents for removal of anionic dyes from mimetic waste water, and also is helpful for the future potential applications of the unique hierarchical porous structures in catalysis and other related fields.

Synthesis of flower-like copper sulfides microspheres as electrode materials for sodium secondary batteries

Flower-like copper sulfides (CuS) microspheres, with a diameter of about 10μm, are synthesized via a facile hydrothermal method and employed to sodium secondary batteries for the first time. The complex structure of CuS is composed by nanosheets with thickness around 50nm. Na/CuS cell delivers an initial discharge capacity of 348.6mAh/g. However, half of initial specific capacity maintains after 4 cycles, accompany with the structure degradation. Despite all that, CuS is a promising cathode material due to its high specific capacity for sodium batteries, which needs much more efforts to improve the cycle stability.

Hydrothermal Synthesis and Characterization of Flowerlike Molybdenum Disulfide Microspheres

Hydrothermal Synthesis and Characterization of Flowerlike Molybdenum Disulfide Microspheres

Synthesis and characterization of new hybrid microspheres with amide functionalization

In this article, synthesis and characterization of new crosslinked hybrid microspheres are presented. This material was obtained by the emulsion-suspension polymerization of 1,4-divinylbenzene and trimethoxyvinylsilane. In the case of introducing biologically active functional groups on the surface of microspheres, methacrylamide as a third monomer was added. Chemical structures of all new materials were confirmed by the spectroscopic method (attenuated total reflectance-Fourier transform infrared spectroscopy) and elemental analysis. The influence of comonomer structure on the physico-chemical properties of the hybrid microspheres was investigated. Porous structures in a dry state were studied by means of nitrogen adsorption–desorption measurements. Thermal stabilities and degradation behavior of the obtained copolymers were characterized by the use of thermogravimetric/derivative thermo-gravimetric analysis.

Plants to Polyelectrolytes: Theophylline Polymers and Their Microsphere Synthesis.

To extend fossil oil supplies, sustainable feed stocks for the production of useful reagents and polymers should be harnessed. In this regard, chemicals derived from plants are excellent candidates. While the vast majority of plant sources used for polymer science only contain C x H y O z , alkaloids such as caffeine, nicotine, and theophylline possess nitrogen functionality that can provide new functions for bioderived polymers and their synthesis. In this context, the chemistry of theophylline, a natural product found in chocolate and tea, is exploited to create a cationic "poly(theophylline)" in a straightforward fashion for the first time. This work demonstrates how this new polymer can be synthesized and used for the creation of narrowly disperse cationic microspheres.

Controlled synthesis of hydroxyapatite microspheres with hierarchical structure and high cell viability

Monodispersed vaterite CaCO3 microspheres with regular morphology were synthesized by a fast precipitation method in the presence of sodium carboxyl methylcellulose, and then used as a template to induce the formation of hydroxyapatite microspheres in a hydrothermal reaction. By regulating reaction temperature and amount of surfactant sodiumdodecyl benzene sulfonate, the secondary nano building blocks of hydroxyapatite microspheres can be accurately controlled between nanoplates and nanorods. Based on XRD, FTIR and HRTEM characterizations, a possible transformation mechanism is proposed. In vitro cell experiments show that hydroxyapatite microspheres with hierarchical structure produce significantly high cell viability. Moreover, the hydroxyapatite microspheres with nanoplates promoted cell reproduction better than those with nanorods.

Synthesis of Magnetic Microspheres with Sodium Alginate and Activated Carbon for Removal of Methylene Blue.

Based on the adsorption performance of composite microspheres with activated carbon (AC) and sodium alginate (SA), as well as the magnetic property of Fe3O4, we designed and explored an efficient strategy to prepare a unique, multifunctional Fe3O4/AC/SA composite absorbent (MSA-AC) that extracted dye from aqueous solution. The composite exhibited the following advantages: rapid and simple to prepare, environmentally friendly process, low-cost, recyclability, and multi-functionality. The physicochemical properties of the prepared magnetic microspheres were measured, and methylene blue (MB) was selected to investigate the performance of the magnetic absorbent. The results showed a maximum adsorption capacity of 222.3 mg/g for MB. Adsorption studies revealed that the data of adsorption isotherms and kinetics fit the pseudo-second-order kinetic model and Langmuir isotherm model.

Deposition of aminosilane coatings on porous Al2O3 microspheres by means of dielectric barrier discharges

Advances in the synthesis of porous microspheres and in their functionalization are increasing the interest in applications of alumina. This paper deals with coatings plasma deposited from 3‐aminopropyltriethoxysilane by means of dielectric barrier discharges on alumina porous microspheres, shaped by a vibrational droplet coagulation technique. Aims of the work are the functionalization of the particles with active amino groups, as well as the evaluation of their surface coverage and of the penetration of the coatings into their pores. A multi‐diagnostic approach was used for the chemical/morphological characterization of the particles. It was found that 5 min exposure to plasma discharges promotes the deposition of homogeneous coatings onto the microspheres and within their pores, down to 1 μm.

Histidine-functionalized carbon-based dot-Zinc(II) nanoparticles as a novel stabilizer for Pickering emulsion synthesis of polystyrene microspheres

Carbon-based dots (CDs) are nanoparticles with size-dependent optical and electronic properties that have been widely applied in energy-efficient displays and lighting, photovoltaic devices and biological markers. However, conventional CDs are difficult to be used as ideal stabilizer for Pickering emulsion due to its irrational amphiphilic structure. The study designed and synthesized a new histidine-functionalized carbon dot-Zinc(II) nanoparticles, which is termed as His-CD-Zn. The His-CD was made via one-step hydrothermal treatment of histidine and maleic acid. The His-CD reacted with Zn2+ to form His-CD-Zn. The as-prepared His-CD-Zn was used as a solid particle surfactant for stabilizing styrene-in-water emulsion. The Pickering emulsion exhibits high stability and sensitive pH-switching behaviour. The introduction of S2O82− triggers the emulsion polymerization of styrene. The resulted polystyrene microsphere was well coated with His-CDs on the surface. It was successfully used as an ideal adsorbent for removal of heavy metallic ions from water with high adsorption capacity. The study also provides a prominent approach for fabrication of amphiphilic carbon-based nanoparticles for stabilizing Pickering emulsion.

Small organic molecule-mediated hydrothermal synthesis of hierarchical porous hydroxyapatite microspheres by the incorporation of copper ions

Hierarchical porous hydroxyapatite microspheres with a pit in the center were prepared under the synergistic effect of inositol hexakisphosphate and copper ions.

The mechanism change by switching the reactants from water to hydroxyl ions for electrocatalytic water oxidation: a case study of copper oxide microspheres.

Developing noble metal-free water oxidation catalysts is essential for many energy conversion/storage processes (e.g., water splitting). Herein, we report a facile synthesis of CuO microspheres composed of ultrathin, single-crystal-like nanosheets via a simple solution method. The as-obtained CuO microspheres can serve as an active and stable water oxidation catalyst under electrochemical reaction conditions, owing to their unique structural features. In electrochemical water oxidation, this catalyst affords a current density of 10 mA cm-2 (a value related to practical relevance) at an overpotential of ∼0.48 V. Pure CuO was reported as a water oxidation catalyst (WOC) from near-neutral conditions to alkalescent conditions. Electrochemistry values agree with the Nernstian behavior, suggesting ne-/nH+ transfer prior to a chemical rate-determining step. Our results suggest that the delicate nanostructure can offer unique advantages for developing efficient water oxidation catalysts.

Synthesis of TiO2-polycrystalline microspheres and its microstructure at various high temperatures

Synthesis of TiO2-polycrystalline microspheres and its microstructure at various high temperatures

Synthesis and characterization of magnetic chitosan microspheres as low-density and low-biotoxicity adsorbents for lake restoration

We propose a novel magnetic adsorbent for optimal Phosphorus (P) removal from the upper sediment layers. For this aim, magnetic chitosan microparticles were prepared using a reverse-phase suspension cross-linking technique. The resulting particles and suspensions were characterized using scanning electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, magnetometry, thermogravimetric analysis, electrophoretic mobility and turbidity measurements. The hybrids are multicore particles consisting of well dispersed magnetite nanoparticles (approx. 10% w/w) homogeneously distributed within the biopolymer matrix. These microparticles can be easily separated from the water column and sediment using magnetic field gradients. Their P adsorption capacity is evaluated in batch conditions resulting in a maximum P adsorption capacity of ML = 4.84 mg g−1 at pH = 7. We demonstrate that these particles are excellent candidates to remove P from water column and also P mobile from the upper sediment layers due to two main reasons: they sediment slower and present lower potential toxicity (due to a their larger size) than conventional iron/iron oxide microparticles previously proposed for lake restoration.