Silicate Spheres Research Articles

SiO2@Cu core: antibacterial, "shell" active agents synthesized through sol-gel

We examined the capacity of SiO2@Cu core-shell nanoparticles to inhibit Escherichia coli and Streptococcus mutaus. Before and after the addition of silicate, copper showed a surface plasmon resonance (SPR) with a peak in the 620–630 nanometers' region. SiO2@cu core-shell nanoparticle manufacturing was further demonstrated to have a spherical shape, as demonstrated in TEM. The crystal structure of the SO2 @cu we found matches the X-ray diffraction patterns for the nanoparticles, which display Face-Centered Cubic (FCC) copper. The infrared Fourier transform (FT-IR). Explains more about the studied interaction of the produced copper NPs with silica. This demonstrated Cu deposition on the spherical silicate (SiO2) surface and the mean size of these nanoparticles was 139 nanometers. SiO2@Cu core-shell nanoparticles were definitely the cause of the inhibitory zone, and they were effective against Escherichia coli bacteria and Streptococcus mutans within ranges of 12–20 mm and 28–34 mm, respectively.

Optimization of the Zr-loading on siliceous support catalysts leads to a suitable Lewis/Brønsted acid sites ratio to produce high yields to γ-valerolactone from furfural in one-pot

The study for the production of γ-valerolactone from furfural in one-pot has been carried out using ZrO2 supported on silica spheres. The catalysts synthesized were characterized by XRD, UV-vis, HR-TEM, N2 adsorption, IR, pyridine adsorption-IR and NH3-TPD in order to determine their physicochemical characteristics. Both, Lewis and Brønsted acid sites are necessary to produce γ-valerolactone from furfural, because they are involved in different steps of the reaction. Accordingly, a reaction mechanism has been proposed. Lewis acid sites of ZrO2 interacting with the –OH surface groups of the siliceous spheres can generate Brønsted acid sites in the supported Zr catalysts, which are absent in both pure ZrO2 and the silica spheres. Then, by controlling the amount of Zr in the supported catalysts, the relative amount of Lewis and Brønsted acid sites can be optimized to obtain the highest yields to γ-valerolactone. The Zr-loading of the optimal supported catalyst was ca. 7 wt% Zr, which reached a γ-valerolactone yield of 72.4 % after 8 h at 180 °C using 2-propanol as a solvent and hydrogen donor.

Fabrication of hierarchical flower-shaped cobalt silicate spheres with boosting performance for lithium storage

As a new type of electrode material, transition metal silicates anode has drawn increasing attention owing to high theoretical capacity, sufficient reserves and nontoxicity. Herein, a unique flower-shaped cobalt silicate was fabricated via an alkali-assisted hydrothermal synthesis method, which feathered large specific surface area and abundant meso-pores. Serving as an anode material for lithium ion batteries, the hierarchical CoSiO 2 material exhibited excellent cycling stability (1111 mAh g −1 at 0.1 A g −1 after 200 cycles) and superior rate capability (411 mAh g −1 at 10 A g −1 ). The novel structure of F–CoSiO 2 anode not only provided abundant active sites for electrochemical reactions and effectively facilitated the migration of Li ions during charge-discharge process, but also contributed to the primary pseudocapacitive charge storage behaviors. This work may open up opportunities in structure design and represent the enormous potential of hierarchical transition metal silicate as practical advanced electrode for lithium storage. • A novel flower-shaped CoSiO 2 anode material for lithium ion batteries was designed and fabricated firstly. • The 3D architecture assembled by 2D nanosheets generated large surface area and abundant mesopores. • The hierarchical structure greatly shortened mass diffusion and fascinated the transport of Li ions. • The CoSiO 2 material exhibited remarkable cycling and rate performance.

Spherical red-emitting X1-Y2SiO5:Eu and α-Y2Si2O7:Eu phosphors with high color purity: The evolution of morphology, phase and photoluminescence upon annealing

Spherical silicate phosphor has widespread application in display or lighting industry. By using spherical silica particles as the core, we successfully prepared shell-thickness-controllable core/shell spherical particles, which can then be controllably converted to spherical X1-Y2SiO5:Eu (YSO:Eu) and α-Y2Si2O7:Eu (YPS:Eu) particles upon annealing. Even after 1000–1200 °C annealing, both X1-YSO:Eu and α-YPS:Eu particles still had the spherical shape and narrow size distribution. The shell thickness and annealing temperature synergistically controlled the phase evolution upon annealing. Thinner shell of around 30 nm, having extremely high chemical reaction activity, promoted the formation of spherical X1-YSO:Eu particles at 1000 °C and α-YPS:Eu particles at 1100 °C. Shell of around 85 nm produced spherical X1-YSO:Eu particles at 1100 °C and α-YPS:Eu particles at 1200 °C. Thicker shell also promoted the formation of spherical particles, but these particles usually had the mixed silicate phases. The phase-dependent photoluminescence properties were investigated in detail. Both spherical X1-YSO:Eu and α-YPS:Eu phosphors emitted reddish-orange color, with nearly 100% color purity and dominant wavelength of around 601 nm, which would absorb great attention for the application in display or lighting devices.

Non-aqueous synthesis of homogeneous molybdenum silicate microspheres and their application as heterogeneous catalysts in olefin epoxidation and selective aniline oxidation

In this work, a novel synthesis of homogeneous molybdenum silicate spheres under non-aqueous conditions is presented. A preparation method is based on the condensation of molybdenum metal–organic framework-based precursor solution prepared via a microwave-assisted approach from bis(acetylacetonato)dioxomolybdenum and biphenyl-4,4′-dicarboxylic acid with 3-aminopropyltriethoxysilane under non-aqueous conditions. The as-prepared product was calcined at 500 °C to obtain amorphous and porous molybdenum silicate microspheres with homogeneously distributed molybdenum species within silicate matrix. The microspheres exhibit an average size of about 480 nm. This material was further studied as a heterogeneous catalyst for the epoxidation of olefins via the model catalytic epoxidation of cyclohexene with cumylhydroperoxide. High catalytic activity at the moderate temperature (65 °C) with the conversion of 86% after 2 h and the high selectivity to cyclohexene oxide has been achieved. In addition, molybdenum silicate microspheres exhibit catalytic activity and high selectivity in the oxidation of aniline to nitrosobenzene.

MIXING PROCESSES AND EQUIPMENT. CONSTRUCTION MIXTURES AND MIXTURES FOR MANUFACTURING CONSTRUCTION MATERIALS. LECTURE 9

The article presents materials of Lecture 9 Theory of carrying and lifting, construction and road vehicles and equipment, which describes mixing machines, concrete mixtures, their dosage, quality and homogeneity. The process of concrete mixing and energy aspects of its production are described. The data on mixers used for producing mortars and clay suspensions are presented. The design of a special mixer for producing polystyrene-silicate mineralized granules and the production technology for hollow silicate spheres based on the working process of a special mixer are described.

A highly uniform CuO@SiO2 porous sphere with improved electrochemical sensing performance for the accurate determination of vanillin in food samples

A porous sphere of CuO@SiO2 was obtained by simple calcination of the copper silicate (CuSiO3) sphere. The formation of the porous sphere was studied in detail with the support of various physical characterization techniques. The CuO@SiO2 was coated on an electrode surface where it demonstrates high catalytic activity for the electro-oxidation of vanillin in phosphate buffer solution (PBS; pH 7.0). The modified electrode has good surface adsorption (1.861 × 10−10 mol cm−2) and rate constant (2.866 × 105 cm3 mol−1 s−1) characteristics for vanillin detection. The CuO@SiO2-modified surface exhibited good linear range (0.05 μM–1.2 μM and 6.2 to 111.2 μM), detection limit (53 nM), sensitivity (2.88 μA μM−1 cm−2), selectivity, stability, and reproducibility. The CuO@SiO2-modified electrode was further examined for the determination of vanillin in real samples including biscuits and chocolates with satisfactory recoveries.

Porous cotton/magnesium silicate composite films as high-performance adsorbents for organic dye removal

Layered silicates are a promising adsorbent for removing various pollutants from wastewater. Herein, a cotton/magnesium silicate composite film is successfully synthesized with a hierarchically porous structure. The composite film can be separated from the treated solution and avoid the potential risk of secondary pollution. The porous magnesium silicate spheres constructed by thin nanosheets are in situ deposited on the surface of cotton fibers using silica spheres as the template under the hydrothermal condition, showing a high specific surface area of 523.1 m2 g−1. Due to the presence of abundant adsorption sites and effective diffusion paths, the composite film exhibits an excellent adsorption property to methylene blue (194.4 mg g−1). The adsorption isotherms and mechanisms are also briefly investigated.

One-step preparation of sustained-release ASDs using mesoporous spherical silica

Preparing amorphous solid dispersions (ASDs) is one of the most important approaches in formulation studies to improve the oral bioavailability of poorly water-soluble drugs. Although a large number of studies have reported the validity of ASDs, most are focused on immediate-release formulations. Therefore, the principal aim of the present study is to establish a practical approach for preparing a sustained-release ASD pellet using mesoporous spherical silica by a Wurster-type fluidized bed granulator. The mesoporous spherical silica used in the present study has a porous structure with silica of different pore sizes. As a model drug, indomethacin (IND) was layered onto the mesoporous spherical silica in an amorphous state, but a clear difference was found in the degree of amorphization and drug release rate of each kind of silica. Moreover, the dissolution profiles of IND after layering with a pH-independent sustained-release polymer on spherical silicate using a Wurster-type fluidized bed granulator were evaluated. Mesoporous silica, with small pore size, showed an ideal sustained-release profile with much smaller polymer amounts compared with larger-pore-size silica. In this approach, the pore size of mesoporous spherical silica was a very important factor to prepare sustained-release ASDs efficiently and stably.

Mesostructured Hollow Siliceous Spheres for Adsorption of Dyes

AbstractA facile and one‐pot strategy for the preparation of novel diamino‐functionalized hollow siliceous spheres (DAF‐HSS) is suggested. Field‐emission scanning electron microscopy (FE‐SEM) images of DAF‐HSS showed a monodispersed hollow sphere morphology. Also, TEM images revealed that the DAF‐HSS has a porous structure with parallel semi‐long‐range channels. DAF‐HSS material was used as an adsorbent for the removal of hazardous monocationic dyes in aqueous solution. Neutral red (NR) and crystal violet (CV) were selected as model compounds. Isotherm and kinetic studies were carried out and their different linear forms were applied and compared. The equilibrium data fitted better with the Langmuir model.

Development of Bulk Lightweight Spherosilicate Material Technology Based on Sublimation of Expanded Polystyrene Granules

The paper discusses the technology for producing bulk lightweight spherosilicate materials as an alternative to expanded vermiculite-based thermal insulation products. The technology is based on the idea of using granulated expanded polystyrene to create a core of silicate spheres coated with special liquid glass-based mixture and treated with carbon dioxide in the process of forming polystyrene-silicate mineralized granules to ensure quick hardening thereof. The paper also reviews a device and operation of the special equipment developed by the authors, such as a mixer for producing polystyrene-silicate mineralized granules and electric drum furnace for roasting spheres and subliming expanded polystyrene granules.

Development of the technology of spherosilicate bulk lightweight materials by the method of sublimation of expanded polystyrene granules

The technology of obtaining spherosilicate bulk lightweight materials as an alternative to expanded vermiculite thermal insulation material is considered. The technology is based on the idea of using granular polystyrene foam as cores of silicate spheres coated with a special composition based on liquid glass with carbon dioxide treatment in the process of formation of polystyrene-silicate mineralized granules for their quick hardening. The device and the operation of special equipment developed by the authors are considered in conjunction with the main technological operations: a mixer for producing polystyrene-silicate mineralized granules and an electric drum furnace for firing spheres and sublimating polystyrene foam granules. Ill. 7. Ref. 13.

Dynamics of Dust Particles of Different Structure: Application to the Modeling of Dust Motion in the Vicinity of the Nucleus of Comet 67P/Churyumov–Gerasimenko

We consider the estimates of the main forces acting on dust particles near a cometary nucleus. On the basis of these estimates, the motion of dust particles of different structure and mass is analyzed. We consider the following forces: (1) the cometary nucleus gravity, (2) the solar radiation pressure, and (3) the drag on dust particles by a flow of gas produced in the sublimation of cometary ice. These forces are important for modeling the motion of dust particles relative to the cometary nucleus and may substantially influence the dust transfer over its surface. In the simulations, solid silicate spheres and homogeneous ballistic aggregates are used as model particles. Moreover, we propose a technique to build hierarchic aggregates—a new model of quasi-spherical porous particles. A hierarchic type of aggregates makes it possible to model rather large dust particles, up to a millimeter in size and larger, while no important requirements for computer resources are imposed. We have shown that the properties of such particles differ from those of classical porous ballistic aggregates, which are usually considered in the cometary physics problems, and considering the microscopic structure of particles is of crucial significance for the analysis of the observational data. With the described models, we study the dust dynamics near the nucleus of comet 67P/Churyumov–Gerasimenko at an early stage of the Rosetta probe observations when the comet was approximately at 3.2 AU from the Sun. The interrelations between the main forces acting on dust aggregates at difference distances from the nucleus have been obtained. The dependence of the velocity of dust aggregates on their mass has been found. The numerical modeling results and the data of spaceborne observations with the Grain Impact Analyzer and Dust Accumulator (GIADA) and the Cometary Secondary Ion Mass Analyzer (COSIMA) onboard the Rosetta probe are compared at a quantitative level.

Preparation and characterization of mesoporous calcium‐doped silica‐coated TiO2 scaffolds and their drug releasing behavior

AbstractThree dimensional titanium dioxide (TiO2) scaffolds are receiving attention for the reconstruction of damaged bone tissue. Although these scaffolds show sufficient mechanical properties, their bioactivity is significantly lower than that of bioactive glass scaffolds. Sol‐gel derived mesoporous bioactive glasses exhibit high bioactivity in vitro and can also be loaded with drugs and growth factors due to their tunable pore size. Hence, the main aim of this work is to produce and characterize TiO2 scaffolds coated with sol‐gel derived mesoporous calcium silicate spheres (MCS) and to test their in vitro bioactivity and drug delivery properties. TiO2 scaffolds were coated with different wt% of MCS using a simple dip coating method. The bioactivity of the MCS‐coated TiO2 scaffolds was tested in vitro in simulated body fluid (SBF). TiO2 scaffolds coated with 2 wt% and 4 wt% MCS showed bioactivity after 1 week of immersion in SBF. The formation of hydroxyapatite (HA) was confirmed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X‐ray diffraction analysis (XRD). Ibuprofen drug loading and release rate were investigated in MCS and MCS coated TiO2 scaffolds. A 3 weeks in vitro drug release test was performed and the amount of drug released by MCS was measured by UV‐Vis spectroscopy. The MCS were successfully loaded with Ibuprofen, as model drug. Sustained drug release was measured, proving the applicability of MCS as drug delivery carriers. Thus, TiO2 scaffolds with enhanced functionalities were produced exploiting MCS coating.

Dual-responsive electrochemical immunosensor for detection of insulin based on dual-functional zinc silicate spheres-palladium nanoparticles

In this study, described an electrochemical immunoassay for insulin that is based on the use of zinc silicate spheres loaded with palladium nanoparticles (Zn2SiO4-PdNPs) that act as dual-function labels. The Zn2SiO4-PdNPs display high electrocatalytic activity towards the reduction of H2O2 and high sensitivity in chronoamperometry. The Zn2SiO4-PdNPs decrease the electron transfer rate between the electrolyte and the surface of the electrode, which can increase the changed current and enhance the sensitivity of the immunosensor as detected by square wave voltammetry (SWV). Electrodeposited gold is used as the matrix material. The icosahedral gold nanocrystals are coated with the primary antibodies formed a 3D mode to against abundant of insulin. Under optimal conditions, the assay has a linear response in the 0.1pgmL−1 to 50ngmL−1 insulin concentration range, and the limit of detection of the SWV and CA methods are 0.25 fg mL−1 and 80 fg mL−1, respectively. Moreover, the immunosensor holds an outstanding analytical performance for the insulin detection and has promising potential in clinical diagnosis.

Fabrication of Hierarchical Hollow Manganese Silicate Spheres for the Simultaneous Enhanced Determination of 2‐Aminophenol and 4‐Aminophenol

AbstractWe developed a new electrochemical method for the simultaneous determination of 2‐aminophenol (2‐AP) and 4‐aminophenol (4‐AP) based on hollow manganese silicate spheres. The hierarchical hollow structure of manganese silicate submicrometer spheres was formed by the assemblage of numerous nanobubbles, as confirmed by scanning electron microscopy and transmission electron microscopy images. As sensing material for the simultaneous determination of 2‐AP and 4‐AP for the first time, the electrochemical performances of 2‐AP and 4‐AP were studied in detail. The detection limits (S/N=3) for 2‐AP and 4‐AP were as low as 18 and 11 nM, respectively.

Application of spherical silicate to prepare solid dispersion dosage forms with aqueous polymers

The objective of this study is to prepare and characterize solid dispersions of nifedipine (NP) using porous spherical silicate micro beads (MB) that were approximately 100μm in diameter with vinylpyrrolidone/vinyl acetate copolymer (PVP/VA) and a Wurster-type fluidized bed granulator. Compared with previously reported solid dispersion using only MB, the supersaturation of NP dissolved from the proposed system of MB and PVP/VA was maintained during dissolution tests. The proposed system produced a solid dispersion product coated on MB, and morphology was maintained after the coating process to prepare solid dispersion; therefore, the powder characteristics, such as flowability of the proposed solid dispersion product, was tremendously preferable to that of the conventional spray-dried solid dispersions of NP with PVP/VA, expecting to make the consequent manufacturing processes easy for development. Another advantage in the terms of manufacturing is its simple process to prepare solid dispersion by spraying the drug and polymer that were dissolved in an organic solvent onto a MB in a Wurster-type fluidized bed granulator, thus, simplifying the optimization and scale-up with ease.

Inside Back Cover: Manipulation of Shell Morphology of Silicate Spheres from Structural Evolution in a Purely Inorganic System (Chem. Asian J. 6/2015)

Inside Back Cover: Manipulation of Shell Morphology of Silicate Spheres from Structural Evolution in a Purely Inorganic System (Chem. Asian J. 6/2015)

Manipulation of shell morphology of silicate spheres from structural evolution in a purely inorganic system.

We have investigated the structural transformation of solid silica spheres into various more complex spherical structures including flower-like, thick or thin nanosheet-shelled and porous shelled spheres. In the absence of organic additives, sodium salts contained in this inorganic reaction system apparently direct the silica dissolution and regrowth of dissolved silicate at the nanometer-scale, leading to the formation of a nanosheet network rather than solid aggregates. Subsequent removal of the salts by simple water washing results in voids in the siloxane network and a significant availability of surface silanol groups so that the resulting nanosheets and spheres composed of them possess large surface areas, pore volumes, and morphological flexibility, which can be varied by an applied stimulus. The results represent a rare example of the transformation of a simple silicate structure into a much more complex spherical structure involving a purely inorganic reaction system.

Platinum-group minerals in the Limoeiro Ni–Cu–(PGE) sulfide deposit, Brazil: the effect of magmatic and upper amphibolite to granulite metamorphic processes on PGM formation

The Limoeiro Ni–Cu–(platinum-group elements (PGE)) deposit is a recent discovery associated with an igneous tubular conduit system in northeastern Brazil. Representative ores from the deposit have been used for platinum-group minerals (PGM) identification and for PGE in base metal sulfides (BMS) quantification. Ninety-eighty percent of the PGM in the massive sulfide ores is homogeneous Pt–Ni–Bi-bearing merenskyite (PdTe2) enclosed primarily by pyrrhotite, suggesting that it is formed by exsolution from monosulfide solid solution (MSS). Merenskyite gradually but systematically becomes poorer in Pt and Ni with increasing fractionation, which is interpreted to reflect a transition to a more evolved sulfide liquid that segregated in the eastern parts of the intrusion. In massive sulfide ores, merenskyite forms unusually large (up to 5000 μm2) euhedral grains, commonly in contact with spherical silicate inclusions. BMS hosts 12–16 % of the Pd, with the remainder hosted by PGM, which is interpreted to indicate that merenskyite recrystallized from a PGE-bearing bismuthotelluride metamorphic melt formed during high-grade metamorphism. Sperrylite (PtAs2) is the second most abundant PGM (18 % of PGM in disseminated ore) and in contrast to merenskyite occurs mainly as very small (median of 25 μm2) inclusions in high-temperature silicates and oxides, interpreted to have crystallized at high temperatures directly from sulfide blebs that formed and were transported within the Limoeiro magma conduit.