Synthesis Of Microspheres Research Articles

Solvo-Thermal Synthesis of H6V4O10 Microspheres as Stable Electrode Materials for Lithium and Zinc-ion Batteries

Solvo-Thermal Synthesis of H6V4O10 Microspheres as Stable Electrode Materials for Lithium and Zinc-ion Batteries

Mechanism of formation of microstructure of thin-layer coating based on Portland cement

Coatings based on mineral binders with inorganic hollow microfillers are effective thermal insulation materials. However, they have poor physical and mechanical characteristics, and this prevents from their extensive practical use. The purpose of the work is to develop the composition of a thin-layer thermal insulation coating based on Portland cement with addition of a complex additive intended to improve its physical and mechanical properties. The use of this additive facilitated the additional on-surface synthesis of microspheres of crystalline hydrates in the form of aggregate gels, ettringite needles and laminar structures, as well as the compacting of the structure of a thin-layer thermal insulation coating with crystalline hydrates formed during the clinker aluminate phase. These structural changes contributed to the improvement of physical and mechanical parameters of the thermal insulation coating.

Synthesis and characterization of cadmium-bismuth microspheres for the catalytic and photocatalytic degradation of organic pollutants, with antibacterial, antioxidant and cytotoxicity assay

Cadmium-Bismuth microspheres (CdS-Bi2S3) were prepared by facile solvothermal method with polyvinylpyrrolidone (PVP) employed to control the morphology of CdS-Bi2S3. The product was characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), diffuse reflectance UV–vis spectrophotometer and surface area of CdS-Bi2S3 was determined by BET analyzer. It was observed that CdS-Bi2S3 spheres exhibited good catalytic activity for the reduction of 4-nitrophenol. The photocatalytic application of CdS-Bi2S3 was evaluated for the photocatalytic degradation of environmental pollutants such as methyl orange, and methyl green under UV–visible light irradiation and it demonstrated good photocatalytic activity. Furthermore, we studied the antioxidant activity of CdS-Bi2S3 and it was observed that CdS-Bi2S3 showed antioxidant activity at all tested concentrations (5, 3 and 1 mg/mL). Antimicrobial activity of CdS-Bi2S3 microspheres was also studied for microbial control and the tested nanospheres proved to be exceptional antibacterial agent against tested Gram-positive and Gram-negative bacteria. CdS-Bi2S3 microspheres also exhibited significant cytotoxicity activity against HCT 116 (Human colon colorectal tumor) cell line. Our results indicate that CdS-Bi2S3 is good photocatalyst with several biological activities. The effective preparation method of CdS-Bi2S3 could be useful to design and fabricate the novel photocatalyst which may have several applications in the field of catalysis and in the medicine.

A green and easy way for carbon microspheres synthesis impregnated with palladium for hexavalent chromium reduction

Hexavalent chromium is a toxic heavy metal widely spread due to industrial activities around the world. Therefore, to treat wastewaters with this hazardous metal, carbon microspheres were synthesized from a 1.4 mol/L D-glucose solution heated in a closed vessel at 180 °C for 24 h. This carbon material was already functionalized with acid sites which may act as anchor groups for different ions removal. With this hydrothermal and eco-friendly method, it was possible to prepare carbon microspheres with 262 m2/g of surface area, 15 μm of average particle size and a total acidity of 3.13 mmol/g. Activated carbon of 1400 m2/g was oxidized as well with HNO3 in order to compare its activity with carbon microspheres in Cr(VI) reduction. Finally, Pd was impregnated on both carbon materials to reduce Cr(VI) with formic acid as reducing agent. The composite with Pd impregnated on carbon microspheres resulted to be the best catalyst since it reduced Cr(VI) in 150 min.

Radiation synthesis and heavy metal ions removal of cellulose microsphere based adsorbent

A novel cellulose-based adsorbent was successfully prepared by radiation induced grafting of glycidyl methacrylate onto the surface of cellulose microspheres, followed by epoxy ring-opening reaction to introduce iminodiacetic acid disodium (IDA). The characterization of the obtained adsorbent was investigated in detail. To evaluate the adsorption performance of the novel adsorbent in comparison with commercial adsorbent D850, batch and column mode adsorption experiments against Cu (II) and Ni (II) were conducted. The equilibrium time for Cu (II) and Ni (II) were 20 and 30 min, which is much shorter than that of commercial adsorbent. The adsorption capacity of the adsorbent for Cu (II) and Ni (II) reached 96.90 and 111.11 mg/g, respectively. Applicability of the novel adsorbent on the actual wastewater generated from electroplating plants was also investigated. It was found that the novel adsorbent possessed a higher adsorption/desorption velocity and broadly similar adsorption capacity with the commercial adsorbent, signifying the effective adsorption performance of the developed grafted adsorbent.

Self-assembled NiO microspheres for efficient inverted mesoscopic perovskite solar cells

Perovskite solar cells (PSCs) with both normal (n-i-p) and inverted (p-i-n) mesoscopic structures usually exhibit higher efficiency than their planar counterparts because the mesoporous charge transport layers can supply heterogeneous nucleation sites for growing high quality perovskite crystals and enlarged charge separation area for better charge extraction. However, comparing with the achieved extremely high or even the certified world record efficiency of mesoscopic PSCs, the significant improvement of inverted mesoscopic PSCs has yet been made, mainly owing to the lack of suitable p-type semiconductors for preparing mesoporous hole transport layers (HTLs). Here, an emulsion-based bottom-up self-assembly strategy is used to prepare NiO microspheres from well-dispersed NiO nanocrystals. The self-assembled NiO microspheres are further used to fabricate mesoporous NiO HTLs of the inverted mesoscopic PSCs. The as-prepared mesoporous NiO HTL with self-assembled NiO microspheres can provide more suitable graded energy alignment, better charge carrier dynamics and reduced dark recombination in the device comparing with the inverted planar PSC with NiO nanocrystal HTL, contributing to obviously enhanced photovoltaic performance and nearly eliminated photocurrent-voltage hysteresis. Due to the general strategy of emulsion-based bottom-up self-assembly for microspheres synthesis, it will overcome the shortage of p-type materials for preparing efficient inverted mesoscopic PSCs.

Better RAFT Control is Better? Insights into the Preparation of Monodisperse Surface-Functional Polymeric Microspheres by Photoinitiated RAFT Dispersion Polymerization

Efficient synthesis of polymeric microspheres with high uniformity, well-defined surface functionality, and precise diameter and composition has long been a challenging goal in polymer science. Herein, we exploited photoinitiated reversible addition–fragmentation transfer (RAFT) dispersion polymerization of methyl methacrylate using poly(glycerol monomethacrylate)-based macromolecular chain transfer agents (macro-CTAs). We showed that the use of a binary mixture of macro-CTA and CTA with poor controllability was crucial for obtaining monodisperse poly(methyl methacrylate) (PMMA) microspheres. Evolution of PMMA microspheres during the polymerization was followed by scanning electron microscopy and 1H NMR spectroscopy, confirming a linear evolution of particle volume with monomer conversion. PMMA microspheres with better colloidal stability were obtained when increasing the amount of macro-CTA used in photoinitiated RAFT dispersion polymerization. Finally, a two-stage photoinitiated RAFT dispersion polymerization was also explored by adding additional monomers in the second stage. We demonstrated that the particle size of polymeric microspheres could be precisely controlled by adding different amounts of the monomer in the second stage. Moreover, polymeric microspheres composed of two polymers were also prepared by adding a different monomer in the second stage. This study not only optimizes reaction conditions for preparing monodisperse surface-functional polymeric microspheres but also provides mechanistic insights into photoinitiated RAFT dispersion polymerization.

Synthesis and application of porous oil-sorbent microspheres: Characterization, retention capacity and sorption kinetics

The article focuses on the study of oil spill cleanup in an aquatic media by comparing the oil sorption capacities of three polymeric sorbents. Styrene - dodecyl methacrylate – DVB with toluene as porogen (P3) showed a highest removal ability of 5 times its weight. However, key aspect of this research is associated with the retention capacities of the sorbents. The loss in weight measured over time was found to be numerically insignificant for all the three sorbents. Water contact angle for the sorbents i.e., P1, P2, P3 were found to be 113.3°, 107.2° and 97.5° respectively. SEM results confirmed the entrapment of oil between the polymer molecules thereby confirming the phenomenon of sorption. The sorption kinetics of oil over the sorbent surface was followed the pseudo-second order model. The prepared sorbents can be successfully employed for the recovery of oil spills from water sources.

A One-Step Ultrasonic Spray Pyrolysis Approach to Large-Scale Synthesis of Silica Microspheres

This paper proposes a novel and simple one-step ultrasonic spray pyrolysis (USP) approach to prepare silica (SiO2) microspheres, in which only one chemical reagent—silica sol, is used as precursor. In this approach, aerosol droplets of silica sol generated by a ultrasonic nebulizer are transformed into its SiO2 microspheres through water evaporation, precipitation, drying, dehydration and densification in a tube furnance. The products were investigated by scanning electron microscopy, X-ray diffraction, energy dispersive spectrometer, Fourier transform infrared spectroscopy and thermogravimetry, respectively. Above characterizations showed that all the products were dry, unifrom, regular and smooth silica microspheres. The SiO2 concentrations of silica sols have a significant influence on the diameters and size distributions of the products. The microspheres prepared using silica sol with a low mass concentration (e.g. 10%) showed a narrow size distribution; most microspheres ranged from 1.0 to 1.4 μm in diameter. This approach shows great potential in large-scale synthesis of silica microspheres for two reasons: 1) USP is a continuous large-scale method; 2) silica sols are nontoxic and have been industrially produced.

Facile one-step hydrothermal synthesis of SnO2 microspheres with oxygen vacancies for superior ethanol sensor

This work reports a facile one-step hydrothermal method to synthesize the microsphere SnO2 particles without using any organic agent. The experiment results show that the obtained SnO2 microspheres consisting number of nanocrystalline particles of 2–5 nm in size. Oxygen vacancies are also existing on the surface of the SnO2 microspheres. The as-prepared SnO2 microspheres possess mesoporous structure of remarkably high specific surface area (111.27 m2g-1). The gas sensing properties of the as-prepared SnO2 microspheres for ethanol was investigated. The response and recovery time of SnO2 sensor surprisingly reached to 3 s and 24 s respectively under 100 ppm flow of ethanol at an operating working temperature of 230 °C. The response of sensor for 100 ppm of ethanol is enhanced to 24.9 at 230 °C. The excellent ethanol-sensing performance of the fabricated sensor has been attributed to its small grain size, high specific surface area and number of oxygen vacancies of SnO2. These results indicating that the SnO2 microspheres obtained in this work is a promising and excellent ethanol-sensor material.

Synthesis and Characterizations of Biodegradable Polyurethane Microspheres with Dexamethasone for Drug Delivery

This manuscript reports on the synthesis of biodegradable polyurethanes (PU) using poly(e-caprolactone) diol and fabrication of microspheres containing dexamethasone (DEX). Biodegradable PUs with different isocyanate ratios were successfully synthesized using PCL diol as a polyol. The PU with a high isocyanate ratio exhibited a low average molecular weight, high melting point, high Young’s modulus, low tensile strength, low elongation to break, low hydrolytic degradation rate, and fast release profile of DEX. These results can be used to optimize properties so as to be suitable for specific applications. Our next goal is to evaluate the performance of PU microspheres as an injectable cartilage filler through in vitro and in vivo studies. In addition, the biodegradable PUs can be used for tissue-engineered scaffolds using three-dimensional printing.

Facile Synthesis of IrCu Microspheres Based on Polyol Method and Study on Their Electro-Catalytic Performances to Oxygen Evolution Reaction.

The development of Ir-based catalyst with high efficiency for oxygen evolution reaction (OER) in acidic conditions is of great significance to the development of clean energy, but it still remains a significant challenge for shape controlled synthesis of Ir-based catalysts. This article presented a facile one-pot synthesis method that is based on polyol method for preparing IrCu microspheres. In the process of synthesis, formaldehyde solution and ethylene glycol were used as reducing agent and solvent, respectively, while poly(vinylpyrrolidone) was used as surfactant and dispersant, and all of them played important roles in the successful synthesis of Ir-Cu microspheres. The Ir-Cu microspheres, as synthesized, showed well sphere shape and smooth surface, while their alloy features were quite clear and the composition could be adjusted. Benefitting from the synergistic electronic effect between the Iridium and Cupric atoms from the alloy, the IrCu0.77 microspheres exhibited excellent electrocatalytic activity towards OER in 0.1 M HClO4 electrolyte, and to achieve 10 mA cm−2, IrCu0.77 microspheres only required the overpotential of 282 mV, which was much lower than that of commercial Ir/C catalysts.

Hydrothermal synthesis of hierarchical hollow hydroxyapatite microspheres with excellent fluoride adsorption property

Abstract Hierarchical hollow hydroxyapatite microspheres (HHHMs) were fabricated by a facile hydrothermal process and used as an adsorbent for removing fluoride from aqueous solutions. The adsorbent was characterized by microscopic, spectroscopic, diffractometric and thermal analysis techniques. The adsorption kinetics, adsorption isotherms, and the effects of both the initial solution pH and coexisting anions on fluoride adsorption were evaluated. The results showed that the excellent fluoride adsorption capacity of the HHHMs was related to their hierarchical porous hollow structure and large specific surface area. Furthermore, the adsorption kinetics of the HHHMs were accurately described by the pseudo-second-order kinetic model, the adsorption isotherms were perfectly fitted by the Langmuir isotherms model. The adsorption process was pH dependent. The fluoride adsorption capacity decreased the most in the presence of carbonate, followed by phosphate and sulfate, and then nitrate and chloride, which had equal effect on the fluoride adsorption process. Moreover, the adsorption mechanism was studied by FT-IR, XPS, and pHpzc analysis. The results confirmed that the interaction of fluoride with the HHHMs was mainly dominated by ion exchange, electrostatic interactions, and hydrogen bonding. All these results indicated that the low-cost and scalable production of HHHMs has excellent applicability for wastewater treatment.

Fabrication of highly efficient heterostructured Ag-CeO2/g-C3N4 hybrid photocatalyst with enhanced visible-light photocatalytic activity

On the basis of hydrothermal synthesis of Ag-CeO2 microspheres, Ag-CeO2/g-C3N4 composite photocatalyst with heterostructure was prepared by simple solvent evaporation of Ag-CeO2 and g-C3N4. To characterize the composition, structure, morphology and light absorption properties of the as-prepared Ag-CeO2/g-C3N4 composites, XRD, FTIR XPS, SEM, TEM, PL, BET and UV-vis DRS were used, respectively. The as-prepared photocatalyst was subjected to photocatalytic degradation of pollutants, and the prepared composite material has excellent photocatalytic activity for photodegradation of methylene blue (MB). The research shows that the photocatalytic properties of Ag-CeO2/g-C3N4 composites were related to the mass ratio of Ag-CeO2 microspheres and g-C3N4 nanosheets. When the ratio of Ag-CeO2 microspheres: g-C3N4 is 1:5, the composites have the highest photocatalytic activity, which was 9.6 and 3.3 times that of single Ag-CeO2 and g-C3N4, respectively. The improvement of photocatalytic activity is attributed to the heterostructure between the composite materials and the addition of noble metal silver, and the degradation of methylene blue by the visible light irradiation material is greatly improved. Finally, an attempt was made to analyze the principle of photocatalytic degradation of pollutants in prepared materials.

Mesoporous TiO2 microspheres with improved efficiency for photooxidation of volatile organic compounds

Mesoporous hierarchical TiO2 microspheres have been prepared using titanium alkoxide and crown ether as a structure-directing agent in combination with a small amount of surfactant by sol–gel synthesis with or without hydrothermal treatment and characterized by SEM, TEM, XRD and BET measurements. Microspheres with a size range from 0.6 to 3.0 μm have been formed by agglomeration of primary anatase nanoparticles with crystallite size of ca. 10 nm. Almost all TiO2 microspheres have shown superior activity in photooxidation of volatile organic compounds to CO2 significantly higher than that of TiO2 Evonik P-25. Hydrothermal treatment of particles has increased photocatalytic activity of titania microspheres. It has been established that the introduction of small amounts of additives to the reacting system, in particular palmitic acid, during the synthesis of TiO2 microspheres not only significantly affects the texture characteristics of the obtained materials, but also significantly increases their photocatalytic activity. The outstanding photocatalytic activity of microspheres is a consequence of the dominant contribution of the developed mesopore system (large pore volume and diameter) in their hierarchical structural organization, which is formed by aggregation and agglomeration of anatase nanoparticles. Photoactivity of TiO2 microspheres is not always determined by the specific surface area of the sample.

Facile Controlled Synthesis of Spinel LiMn2O4 Porous Microspheres as Cathode Material for Lithium Ion Batteries.

Although the electrochemical properties of porous LiMn2O4 microspheres are usually improved compared to those of irregular LiMn2O4 particles, the effects of the different synthesis conditions on the preparation of the porous LiMn2O4 microspheres are rarely discussed in detail. In the present work, porous LiMn2O4 microspheres were successfully synthesized by using molten LiOH and porous Mn2O3 spheres as a template. Multiple factors were considered in the preparation process, including reagent concentration, pH, adding mode, heating time, etc. The morphology of the MnCO3 template was crucial for the preparation of porous LiMn2O4 microspheres and it was mainly affected by the concentration of reactants and the pH value of the solution during the precipitation process. During the lithiation of Mn2O3 microspheres, the heating temperature and the ratio between Mn2O3 and lithium salt were the most significant variables in terms of control over the morphology and purity of the LiMn2O4 microspheres. Furthermore, we demonstrated that the porous LiMn2O4 microspheres presented better rate capability and cyclability compared to commercial LiMn2O4 powder as cathode materials for lithium-ion batteries (LIBs). This study not only highlights the shape-controllable synthesis of LiMn2O4 microspheres as promising cathode materials, but also provides some useful guidance for the synthesis of porous LiMn2O4 microspheres and other LIB' electrode materials.

Interaction of femtosecond laser radiation with titanium in a liquid hydrocarbon medium

A method for the synthesis of microspheres coated with titanium carbide is described. The processes occurring in the region of the action of laser radiation are considered. The formation of microspheres was carried out by the action of femtosecond laser radiation on the surface of titanium located in the reaction medium - the ultimate hydrocarbon. The hydrocarbon source was the medium in which the treatment was carried out. The obtained microspheres have an average size of 1-3 μm and can be used in applications of additive engineering, powder metallurgy as the main raw material, or as an alloying additive.

Synthesis of Cu2O microspheres with hollow and solid morphologies and their gas sensing properties

Cu2O microspheres with hollow and solid features were successfully prepared via a convenient liquid phase reducing method. Interestingly, we found that the discrepancy in morphology arose from a simply changing on the adding sequence of aqueous sodium dodecyl sulfate (SDS) and CuCl2 with other conditions unchanged. Based on experimental results, the feasible formation mechanisms of both morphologies were deduced, where the relative concentration of SDS and CuCl2 was a crucial factor that effect the resultant morphologies. In comparison with the solid microspheres, the hollow Cu2O exhibited superior gas sensing performance. The significant performance might ascribe to its unique hollow structure, contributing to plenty of active sites existed on both the inner and outer surface and unrestricted gas diffusion in the hollow microspheres.

Titanium Oxide Microspheres with Tunable Size and Phase Composition.

Due to their unique physical and chemical properties, monodisperse titanium oxide microspheres can be used in dye-sensitized solar cells, as cosmetic pigments, and for other applications. However, the synthesis of microspheres with narrow size distribution, desired phase composition, and porosity is still a challenge. In this work, spherical titania particles with controllable size, crystallinity, and pore size were obtained by Ti(OnBu)4 hydrolysis in ethanol. The influence of NaOH addition on the particles’ size and morphology was investigated for the first time. Particle diameter can be tailored from 300 nm to 1.5 μm by changing water and NaOH concentrations. Particle size was analyzed by the statistical processing of scanning electron microscopy (SEM) images and differential centrifugal sedimentation (DCS) measurements. Optical properties of the microspheres were studied by diffuse reflectance UV-Vis spectroscopy. Thermal and hydrothermal treatment allowed transforming amorphous phase in as-prepared particles into nanocrystalline anatase and/or rutile. Transmission electron microscopy (TEM) study of the lamellae, cut out from spherical particles using focused ion beam (FIB), revealed that as-synthesized microspheres are non-hollow, homogeneous, and crystallize throughout the whole volume of the particle. The spherical particles possess photoprotective properties; the highest sun protection factor (SPF) was observed for amorphous microspheres.

Hollow amorphous microspheres of nickel phosphate: Synthesis using adenosine 5′-triphosphate disodium salt as a new organic phosphorus source and their application as electrode materials in supercapacitors

High-performance electrode materials are long-cherished for electrochemical energy storage, especially the application in supercapacitors. In this work, an efficient and green hydrothermal process followed by calcination is applied for the fast synthesis of hollow amorphous nickel phosphate microspheres. Instead of traditional inorganic phosphorus, adenosine 5′-triphosphate disodium salt (ATP) as organic phosphorus source is employed which is conductive to build hollow microsphere structure as well as pore channels. The formation mechanism of target product is studied thoroughly by exploring the influence of the reaction temperature and time on the morphology and crystallinity. Benefiting from the construction of hollow amorphous microsphere, our nickel phosphate material achieves a remarkable electrochemical performance with the specific capacitance of 1034 F g−1 at the current density of 0.5 A g−1, and the energy density is 26.75 W h kg−1 at a power density of 750.00 W kg−1, which forecasts to be an ideal electrode material in the aspect of energy storage devices.