Silica Particle Size Research Articles

Synthesis of High-Performance Photonic Crystal Film for SERS Applications via Drop-Coating Method

Silica nanospheres with a well-controlled particle size were prepared via a nucleation-to-growth synthesis process. A facile method is proposed for improving the self-assembly behavior of silica colloidal particles in droplet coatings by the simple controlling of the drying temperature. It is shown that a periodically arranged, opal-structured, photonic crystal film with a large area of approximately 4.0 cm2 can be prepared, even when the particle size is up to 840 nm. When the band gap of the silica photonic crystals falls in the visible-light region, the crystals exhibit distinct structural colors. Moreover, the wavelength of the reflected light increases with an increasing particle size of silica. When the photonic band gap overlaps the wavelength of the laser source, the overall Raman spectrum intensity is significantly enhanced. Accordingly, the proposed nucleation-to-growth process and drop-coating method provides a cheap and simple approach for the manufacture of uniform sized silica and surface-enhanced Raman scattering substrates, respectively.

Ejecta distribution and transport property of fused silica under the laser shock loading

Laser-induced particle ejection on the exit surface of fused silica serves as an important contaminant source in a high-power laser system. The transport process of molten silica particles in a gas environment or vacuum is important in understanding the change in size and temperature of silica particles, which influence the ultra-clean manufacturing of optical components. In this paper, the ejection process of fused silica is investigated using molecular dynamics simulation. The results show that the geometry of a surface scratch influences the mass of the microjet. With shallower groove depth and a smaller vortex angle, the mass of the microjet is less under shock loading. The size of ejected particles tends to decrease gradually and does not change any more eventually. Besides, these particles become dispersed during the transport process in a vacuum. On the other hand, background gas suppresses the particle flow and slows down the particle flow. As the ejected particles compress gas, vapor and small clusters (N < 50) are stripped from the microjet continuously. Eventually, the number of nanoparticles that exceed the free surface decreases to zero. The stripped small clusters behind the head of the microjet recombine with other clusters, which change the volume density of ejected particles near the free surface. The higher velocity of ejected particles induces a stronger gas stripping effect, which makes an increase in the number of small clusters (N < 50). The results can help understand the behavior of particle ejection and the transport process of silica particles in a gas environment or vacuum, especially in the field of laser-induced particle ejection on the exit surface or the laser ablation of fused silica producing aerosol.

Synthesis and characterization of composite SiO2–Al2O3–Fe2O3 core–shell microspheres

The aim of this study was the synthesis and structural characterization of SiO2–Al2O3 microspheres with SiO2 core and (100 − x)Al2O3·xFe2O3 (x = 0, 5, and 10 mol%) shell. Smooth spherical silica particles of uniform size around 1 μm have been synthesized as core material based on the Stober method. In order to enhance the specific surface area, the silica particles were coated with a thin nanostructurated shell, about 15 nm, of aluminum and iron oxides (100 − x)Al2O3·xFe2O3 (x = 0, 5, and 10 mol%). The embedding of iron oxide in the covering shell was related to potential applications of these composite biomaterials for contrast enhancement in magnetic resonance imaging (MRI) and at the same time for local treatments of cancer by hyperthermia. The XRD results point out the amorphous structure of the obtained core–shell particles. The TEM images evidence continuous shell coating of silica spherical microparticles and the XPS analysis of the surfaces prove the occurrence of iron oxide on the outermost layer of the microspheres. Both FTIR and XPS results evidence the formation of Al–O–Si linkage proving that Al2O3 and SiO2 are chemically bonded in the investigated core–shell microspheres.

Influence of Silica Particle Size on the Corrosion Behavior of Electroplated Silica-Ni Hybrid Layer.

Silica–Ni hybrid layers were electroplated on a Q235 steel plate in a Watt nickel plating solution with varying sizes of silica, and a pure nickel layer was prepared as a blank sample. The surface morphology, composition, and crystal structure of the electroplated layers were examined using a field emission scanning electron microscope (FESEM), an energy-dispersive spectrometer (EDS), and a X-ray diffractor (XRD). The corrosion resistance of the samples was evaluated by the experiments of potentiodynamic polarization, electrochemical impedance spectroscopy, and salt spray test in NaCl solutions. The results showed that the smaller the particle size of silicon, the higher the content of silicon in the layer was, and the better the corrosion resistance of the layer was. However, when the particle size is 10 nm, agglomeration would happen, which leads to a decrease in the corrosion resistance performance, 50 nm silica–Ni hybrid layer showed the optimal corrosion resistance with the highest silica content.

Immobilization of [VCl3(N-2,6-Me2C6H3)] Complex on Silica Supports: Synthesis and Catalytic Testing for Ethylene Polymerization

The heterogenization of 2,6-dimethylarylimido–vanadium(V) dichloride via chemical tethering on insoluble silica supports is reported. The effects of the silica particle size, drying conditions, and the reaction time were investigated. The drying conditions of the support were found to be a crucial parameter: drying temperatures over 400 °C were needed to achieve successful catalysis. The supported catalytic systems were characterized by Fourier-transform infrared (FT-IR) spectroscopy, transmission electron microscopy–energy-dispersive X-ray (TEM-EDX), and inductively coupled plasma mass spectroscopy (ICP-MS), while the polymers were characterized by FT-IR, differential scanning calorimetry (DSC), and rheology. Ethylene polymerization tests were performed employing the prepared heterogenized catalysts with methylaluminoxane/diethylaluminum chloride as a cocatalyst. The supported catalyst precursor, when activated with diethylaluminum chloride, promotes the synthesis of polyethylene with seemingly controlled particle size in the absence of reactor fouling, suggesting the successful immobilization of the complex over the inert support. The resulting polymer shows features of ultrahigh-molecular-weight polyethylene (UHMWPE). These findings present a proof-of-concept for a new approach toward the heterogenization of arylimido–vanadium complexes.

Self-pinning of silica suspension droplets on hydrophobic surfaces

HypothesisSelf-pinning induced by the aggregation of particles at the edge of a pinned drop is a pre-requisite for the coffee ring formation. The edge (three-phase contact line) of a suspension drop on a hydrophobic surface would depin and shrink in the early stage of evaporation process. It is plausible to conjecture that the self-pinning of silica suspension drops depends on the particle size and surface property. ExperimentsTwo substrate materials, the alkylsilane coated surfaces and the polydimethylsiloxane surfaces, and three different sizes of silica particles are used to explore the criterion of self-pinning of silica suspension drops on these hydrophobic surfaces. The evaporation process of droplets is recorded and further analyzed. FindingsThe pinning concentration of silica suspensions of a fixed size linearly depends on the receding contact angle of the surface, irrelevant to the substrate material and initial particle concentration. The pinning concentration decreases along with an increase in particle size. In addition, the pinning concentrations of bi-dispersed silica (e.g. 400 + 1000 nm) suspensions have an excellent agreement with that of larger size (1000 nm) particle system. That implies that the larger particle dominates the system of bi-dispersed silica suspensions to initiate the self-pinning, further verified by SEM images.

Effect of Silica Particle Size on the Physical and Mechanical Properties of Lightweight Ceramic Composites

Ceramics hold all traditional, scientific and engineering raw materials or fabricated products used in different applications especially that performed at high temperatures through high-tempers. The remarkable progress made recently in the advancement of technology has related a prerequisite for a seriously huge number of parts with controlled porosity. In ceramic manufacturing, acquiring a porous item of such parameters and at the same time demonstrating appropriate mechanical strength isn`t a simple issue. The powder-mixing system was utilized to fabricate kaolin-silica fired composites. The main purpose of the paper was to prepare ceramic bodies rich in pores with the goal that it will have a lightweight structure. Different wt.% of silica having distinctive two-particle sizes are blended with kaolin, and afterwards, they shaped by semi-dry pressing in a hardened steel mould under 3-ton loads and sintered at four various temperatures, 900, 1000, 1100 and 1200 �C. Evaluating of composite`s physical properties showed that a good level of porosity was obtained, and it was extended; especially in mixtures contain a coarse particle size. These results are enhanced by acceptable evident comes from good apparent solid density and good strength.

Plasmonic Janus Microspheres Created from Pickering Emulsion Drops.

Metal nanostructures have been created in a film format to develop unique plasmonic properties. Here, well-defined metal nanostructures are designed on the surface of microspheres to provide plasmonic microgranules. As conventional techniques are inadequate for nanofabrication on spherical surfaces, photocurable emulsion drops with a regular array of silica particles are employed at the interface to create periodic nanostructures. The silica particles, originating from the dispersed phase, fully cover the interface by forming a non-close-packed hexagonal array after drop generation, and slowly protrude to the continuous phase during aging while their interparticle separation decreases. Therefore, hexagonal arrays of spherical dimples with controlled geometry and separation are created on the surface of microspheres by photocuring the drops and removing the particles. Directional deposition of either aluminum or gold results in a continuous film with a hexagonal array of holes on the outermost surface and isolated curved disks in dimples, which renders the hemisphere of microspheres plasmonically colored. The resonant wavelength is controlled by adjusting the aging time, metal thickness, and size of silica particles, providing various plasmonic colors. This granular format of the plasmonic Janus microspheres will open a new avenue of optical applications including active color pixels, optical barcodes, and microsensors.

Understanding the role of solvent properties on reaction kinetics for synthesis of silica nanoparticles

The effect of various alcoholic solvents and their compositions on the size of silica particles synthesized through hydrolysis and condensation of tetraethyl orthosilicate (TEOS) is studied. The alcohols used are: Methanol, ethanol, propanol, i-propanol, butanol, pentanol, hexanol, octanol, decanol and do-decanol. Ethanol was used as a co-solvent with the higher molecular weight alcohols. Silica particles of size between 100 nm and 2 µm were obtained by changing solvent composition. Concentrations of total soluble silica and silicic acid were measured and used for exploring the kinetics of hydrolysis and condensation reactions. Polarity, steric hindrance and viscosity of solvent were found to have a strong influence on the rate constants and size of silica nanoparticles. An attempt is made to correlate both final particle size and rate constants with dielectric constant, Wiener index and viscosity of the solvent.

Importance of Mesoporous Silica Particle Size in the Stabilization of Amorphous Pharmaceuticals-The Case of Simvastatin.

In this paper, the role of mesoporous silica (MS) particle size in the stabilization of amorphous simvastatin (SVT) is revealed. For inhibiting recrystallization of the supercooled drug, the two MS materials (Syloid® XDP 3050 and Syloid® 244 FP) were employed. The crystallization tendency of SVT alone and in mixture with the MS materials was investigated by Differential Scanning Calorimetry (DSC) and Broadband Dielectric Spectroscopy (BDS). Neither confinement of the SVT molecules inside the MS pores nor molecular interactions between functional groups of the SVT molecules and the surface of the stabilizing excipient could explain the observed stabilization effect. The stabilization effect might be correlated with diffusion length of the SVT molecules in the MS materials that depended on the particle size. Moreover, MS materials possessing different particle sizes could offer free spaces with different sizes, which might influence crystal growth of SVT. All of these factors must be considered when mesoporous materials are used for stabilizing pharmaceutical glasses.

Formation of mesoporous silica particles with hierarchical morphology

The transformation of mesoporous silica morphology from monoliths to spherical particles was investigated at room temperature in Pluronic F127/TEOS system as a function of HCl acid catalyst concentration to understand and control the mechanism. It is shown that the specific surface area and the size of mesoporous spherical silica particles can simply be adjusted by the catalyst concentration without using any additives or post-treatment. Above 3 M acid concentration, novel monodisperse micron sized spherical silica with hierarchical order of two levels was obtained. These silica spheres were formed of densely packed distorted hexagonal platelets of 20–30 nm in diameter. Within these platelets mesoporous channels were oriented along a single direction, however the platelets were randomly oriented in the spherical particles. Controlling the agglomeration of mesoporous silica primary particles by the concentration of the acid catalyst to obtain micron-sized spherical particles is novel. This approach allows the synthesis of particles whose sizes can be controlled in the range of ~1–4 μm and specific surface area in the range of ~200–500 m2/g. The morphology of the particles transforms from spherical shape to mesoporous monoliths at acid concentrations below 1 M due to slow hydrolysis and condensation. These results are important in understanding the role of catalyst concentration on the formation mechanism of different morphologies of mesoporous silica.

Pharmaceutical Characterization and In Vivo Evaluation of Orlistat Formulations Prepared by the Supercritical Melt-Adsorption Method Using Carbon Dioxide: Effects of Mesoporous Silica Type.

Orlistat, an anti-obesity drug, has two critical issues—the first is its low efficacy due to low water solubility and the second is side effects such as oily spotting due to its lipase inhibition. The present study was designed to propose a solution using a formulation with mesoporous silica to simultaneously overcome two issues. Orlistat was loaded onto mesoporous silica by the supercritical melt-adsorption (SCMA) method, using carbon dioxide (CO2). Various types of mesoporous silica were used as adsorbents, and the effects of the pore volume, diameter and particle size of mesoporous silica on the pharmaceutical characteristics were evaluated by various solid-state characterization methods and in vitro and in vivo studies in relation to pharmacological efficacy and the improvement of side effects. The results showed that the pore volume and diameter determine loadable drug amount inside pores and crystallinity. The dissolution was significantly influenced by crystallinity, pore diameter and particle size, and the inhibition of lipase activity was in proportion to the dissolution rate. In vivo studies revealed that the serum triglyceride (TG) concentration was significantly decreased in the group administered amorphous orlistat-loaded Neuisilin®UFL2 with the highest in vitro dissolution rate and lipase activity inhibition in comparison to the commercial product. Furthermore, oily spotting tests in rats revealed that undigested oil was adsorbed onto mesoporous silica after orlistat was released in the gastro-intestinal tract, and it correlated with in vitro result that oil adsorption capacity was dependent on the surface area of empty mesoporous silica. Therefore, it was concluded that mesoporous silica type plays a major role in determining the pharmaceutical characteristics of orlistat formulation prepared using SCMA with CO2 for improving the low solubility and overcoming the side effects.

Flash Chromatography System: A Practical Tool for Demonstrating the Influence of Column Characteristics on Chromatographic Resolution

A flash purification system using prepacked cartridges containing different silica weights and particle sizes was employed to demonstrate the influence of column characteristics on chromatographic ...

Aesthetic Effects on Granite of Adding Nanoparticle TiO2 to Si-Based Consolidants (Ethyl Silicate or Nano-Sized Silica)

Considering that consolidant products are commonly used in the cultural heritage field and the titanium oxide nanoparticles (TiO2) have been used to develop photocatalyst films to induce self-cleaning property, the scientific research on consolidants doped with TiO2 is justified. However, the addition of TiO2 can affect to the physical properties of the cultural heritage object, questioning the adequacy of the procedure. In this paper, we evaluated the influence of nanoparticle TiO2 addition to two different commercial consolidant products (ethyl silicate or nano-sized silica) on the appearance and the color of a granite and the penetration through its fissure system. The stone was previously subjected to high temperature simulating the effect of a fire and the subsequent tap water jet to cool down. Therefore, different concentrations of nanocrystalline TiO2 (0.5, 1, and 3 wt %) were considered. The different compositions were also studied considering the compactness, the extent and the thickness of the superficial xerogel coating, and as well the penetration of the consolidant. The minimal TiO2 concentration tested (0.5 wt %) implied a low-medium risk of incompatibility as an intervention in cultural heritage field, because its low-medium potential as inducer of visible color changes of the granite surface. Regardless of the TiO2 content, the nano-sized silica induced surface xerogel coatings more compact and continue than those formed in the ethyl silicate coated surfaces. Higher penetration rates were identified in the granite treated with nano-sized silica colloidal solution, while ethyl silicate was only found in the first few µm. It was found that penetration could depend on the application procedure, the solvent of the consolidant and the silica particle size. The TiO2 addition reduced the penetration of the nano-sized silica consolidant.

Nano-SiO2@[DABCO(CH2CH2CO2H)]+[Br]− as an efficient and recyclable SCILL for water mediated facile synthesis of thiol-substituted N-aryl pentasubstituted pyrroles

Nano sized silica supported DABCO based amphoteric ionic liquid coated combined catalytic system Nano-SiO2@[DABCO(CH2CH2CO2H)]+[Br]− has been synthesised in a very simple and convenient way. This newly synthesised SCILL has been characterised via FT-IR, SEM, HRTEM and EDAX spectra. The high efficiency of this catalyst was unquestionably recognised when 31 new thiol induced penta-substituted pyrroles were synthesised in water via two different schemes in high yields. This recyclable, quasi heterogeneous catalyst shows synergetic catalytic effect of acidic nano sized silica particles and amphoteric DABCO based ionic liquid.

Fabrication and properties of amorphous silica particles by fluorination of zircon using ammonium bifluoride

A method to prepare amorphous silica particles from zircon has been developed using the fluorination method through a three-step process: the fluorination of zircon using ammonium bifluoride at 230 ℃, the sublimation of (NH4)2SiF6 at 300 ℃ and the hydrolysis of (NH4)2SiF6. During above progress, the composition and phases of materials produced during fluorination of zircon were analyzed; the chemical reaction of silica with ammonium bifluoride, the sublimation behavior of (NH4)2SiF6 and its composition were determined; the effect of hydrolysis temperature (30 ℃, 45 ℃ and 60 ℃) on the hydrolysis ratio of Si and the size of silica particles were investigated. The results indicated that (NH4)3ZrF7 and (NH4)2SiF6 formed after the fluorination of zircon at 230 ℃ for 5 h. (NH4)2SiF6 started to sublimate at 175 ℃, but the sublimation dominated at 280 ℃ and ended at 300 ℃. The hydrolysis results indicated that uni-modal silica particles in micrometer size range were produced at 45 ℃, while bi-modal particles in a variety of sizes ranging from nanometer to micrometer were produced at 30 ℃ and 60 ℃. The amorphous silica particles obtained at 45 ℃ exhibited high purity above 99.96 wt.%, narrow size distribution (average: 254 ± 17 nm), high specific surface (136.8 m2/g), high dibutyl phthalate (DBP)-absorption (2.7 cm3/g), low density (0.532 g/cm2) and pH (5.7). Therefore, the amorphous silica obtained has potential application as filler in plastic and rubber compounding. After the hydrolysis process, ammonium bifluoride can be recycled through the evaporation of NH4F solution. Thus, this work provides a novel strategy for processing zircon by ammonium bifluoride to produce amorphous silica particles and recycle of ammonium bifluoride.

Controllable synthesis of silica nanoparticle size and packing efficiency onto PVP‐functionalized PMMA via a sol–gel method

ABSTRACTThis study aimed to investigate synthesis and adsorption behavior of silica nanoparticles onto polyvinylpyrrolidone (PVP)‐functionalized poly(methyl methacrylate) under various conditions such as methanol/water ratio, ammonium hydroxide concentration, polymer contents, tetraethylorthosilicate contents, and total volume of solvent via sol–gel method. First, the copolymerization of methyl acrylate as a comonomer and 1‐dodecanethiol as a chain transfer agent increased the thermal stability of the product; however, the uniformity of the PMMA particles decreased because of the chain transfer reaction. Second, the adsorption behavior and size of silica nanoparticles could be controlled by adjusting the silica synthesis conditions. The adsorbed silica particle size was greatly influenced by the ammonium hydroxide concentration and the addition of water further enhanced the size increase. However, increasing the water content reduced the packing efficiency of the adsorbed silica particles. Increasing the PVP‐functionalized PMMA content at a fixed TEOS content linearly decreased the silica particle size. But TEOS concentration did not significantly affect the silica particle size. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 662–672

The effect of particle size and concentration on the ballistic resistance of different shear thickening fluids

Shear thickening fluids (STF) have the unique property of increased energy dissipation combined with increased elastic modulus making it ideal for shock absorption applications. The study investigates the effect of particle size and concentration of colloidal silica on the rheological parameters of STF. The particle size of colloidal silica ranged from 100 to 750 nm. Intended for the ballistic performance of STF, the present work also studies the ballistic performance of STF which is a suspension made up of silica of different colloidal particle concentrations in polyethylene glycol (PEG).

In vitro cytotoxicity study of virgin, ethylenediaminetetraacetic acid- and hexamethylenetetramine-capped silica particles synthesized by precipitation method

Silica particles synthesized by precipitation method were in situ capped with Ethylenediaminetetraacetic acid (EDTA) and Hexamethylenetetramine (HMTA) compounds aiming to increase their biocompatibility. XRD, FTIR, TG/DSC, DLS and SEM analyses were performed to determine the crystalline structure, attached functional groups, thermal behaviour, size and morphology of silica particles. XRD analysis showed the amorphous structure of synthesized particles. FTIR results confirmed the formation of SiO2 particles and pointed about the functional groups (−CN, −CO,−OH etc.) attached on surface. Thermal analysis results showed that weight loss was due to removal of water and gradual degradation of EDTA molecules with rise of temperature, i.e. above 220 °C. The dynamic laser scattering measurements (zeta potential) depicted the strongest electrophoretic stability (− 30 mV) of EDTA-capped silica than virgin (− 13 mV) and particles capped with HMTA(− 24 mV). The SEM results revealed that virgin and silica particles capped with EDTA ligand exhibited spherical morphology with an average particle size of 210 nm and 280 nm, respectively. Whereas, HMTA-capped silica partilces showed hexagonal morphology with an average particle size of 240 nm. The in vitro cytotoxicity analysis was also carried out using human HepG2w, ATCC® HB-8065™ cell culture of 100 µg/ml concentration in Dulbecco’s Modified Eagle Medium (DMEM) solution maintained at 37 °C in the presence of CO2 environment. The results revealed that silica particles capped with EDTA (0.07 g) have shown remarkable biocompatibility (~ 96%) than virgin silica (~ 69%) due to bearing better hydrophobic characteristics. However, HMTA decomposed during synthesis which induced toxicity and agglomeration among silica particles. As a result, poor biocompatibility (~ 65%) was observed.

The influences of technological parameters on the ultraviolet photocatalytic reaction rate and photocatalysis-assisted polishing effect for SiC

Abstract At first, aiming at ultraviolet (UV) photocatalysis-assisted polishing of single-crystal 6H-SiC (silicon carbide), the particle size and zeta potential of colloidal silica abrasives on photocatalytic reaction conditions were detected. By doing so, it was guaranteed that colloidal silica abrasives retained their stability with the assistance of photocatalysis. Afterward, the effects of various factors (including light intensity, H2O2 concentration, TiO2 concentration, and pH) on the reaction rate of UV photocatalysis were explored and an orthogonal experiment was conducted on the four factors. The test results showed that H2O2 concentration and light intensity delivered the most significant and the least influences on the rate of photocatalytic reaction, respectively. As the rate of photocatalytic reaction increased, the material removal rate (MRR) increased while the surface roughness Ra generally decreased. In terms of the influence on MRR, the four factors were, in descending order: H2O2 concentration, pH, light intensity, and TiO2 concentration; as for the influence on surface roughness Ra, the four factors were, in descending order: pH, H2O2 concentration, TiO2 concentration, and light intensity. The difference in rank of the four factors arose because MRR was mainly affected by the rate of photocatalytic reaction while surface quality (roughness) was synchronously influenced by the reaction rate and the stability of abrasives. At a light intensity at 1000 mW/cm2, H2O2 concentration of 4.5 vol%, TiO2 concentration of 3 g/L, and a pH of 11, the optimal polished surface can be attained, with a surface roughness Ra of 0.423 nm.