Commercial Silica Particles Research Articles

Organically modified mesoporous silica as a performance additive in tubular quenched polypropylene films

Mesoporous silica nanoparticles were synthesized by base-catalyzed hydrolysis of tetraethyl orthosilicate in the water-acetone medium. For surface modification of mesoporous silica, commercially available silane, 3-(trimethoxysilyl)propyl methacrylate was reacted with mono-thioglycerol via 2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl (TEMPO) aided thiol-ene reaction, and the obtained silane was incorporated on the surface of neat mesoporous silica to graft extended alkyl chains terminating in hydroxyl groups. The prepared MSNs were characterized by thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), nitrogen adsorption-desorption analysis, scanning electron microscopy, and dynamic light scattering. These MSNs were compared to conventionally used commercial silica as an additive in tubular quenched polypropylene films (TQPP) for their anti-blocking, thermal, mechanical, optical, and barrier properties. Organic modification of MSNs decreased the blocking force in TQPP films. The mechanical properties including % elongation and tensile strength increased for TQPP films with mesoporous silica, while it decreased for films containing commercial silica. Both modified and unmodified MSNs decreased haze and enhanced gloss in TQPP films, showing improved optical properties as compared to commercial silica particles. In TQPP film with modified MSNs, a reduced value of the water contact angle was obtained, indicating better wettability of the surface of the TQPP film.

Pseudomorphic synthesis of bimodal porous silica microspheres for size-exclusion chromatography of small molecules

In this work, mesoporous silica microspheres with bimodal porous structures for size exclusion chromatography (SEC) supports were synthesized via a pseudomorphic transformation method by using 3.5 and 5 μm commercial silica particles as sources and cetyltrimethylammonium bromide (CTAB) as a template. The effects of the synthetic conditions on the pore size distribution were examined, including the temperature, reaction time and the molar ratio of SiO2:NaOH. Bimodal porous silicas (BPSs) with pore sizes of 3.01 and 12.80 nm were obtained with SiO2:NaOH:CTAB:H2O=1:0.1:0.1:20 at 80 °C for 24 h. The BPSs were bonded with diol groups to produce a stationary phase for SEC. The column performance was evaluated with three types of samples, namely, dextran (70 KDa-62 Da), polyethene glycol (PEG) (20 KDa-32 Da) and three biomolecules (36 KDa-1.36 KDa). The column that was packed with a 3.5 μm stationary phase showed excellent resolution for molecular weights of less than 1 KDa with high column efficiency. Carbohydrate samples (dextran (MW=1296), dextran (MW=972), sucrose (MW=342), glucose (MW=180) and glycerol (MW=92)) were separated. Heptaethylene glycol, hexaethylene glycol, pentaethylene glycol, tetraethylene glycol, triethylene glycol, and diethylene glycol were resolved in a PEG200 sample. In summary, this work shows the advantages of bimodal mesopores in SEC for small molecules less than 1 kDa. In the pseudomorphic synthesis, the pore size can be regulated by template micelles. Thus, the development SEC supports with high accuracy for a specified molecular weight range is expected since the pore size can be regulated by the surfactant template.

Thermal stability of superhydrophobic and oleophobic silica nanoparticle spray coating

Superhydrophobic surfaces are known to offer high water repellency, however many industries such as the petrochemical and automotive industry need not only water resistant surfaces but also require oil resistant surfaces. Oleophobic coatings repel/reduce adhesion of viscous liquids and oil to the surface. Nano-coatings like silica nanoparticle coatings are known to offer both superhydrophobic and oleophobic properties. In this study, we evaluated both functionalized (FSP) and non-functionalized commercial silica particles (NFSP) and functionalized silica nanoparticles (FSN). Some of the key issues with employing both superhydrophobic and oleophobic coatings are durability and thermal stability. In our studies, we assessed the thermal stability of silica nanoparticle spray coatings, targeting a thermal stability of 500 °C. Our results indicated that the FSN coating exhibited both high water (≥ 150°) and oil (≥140°) contact angle at lower temperatures (100 °C) and was thermally stable up to 400 °C, in which the WCA and OCA only decreased by 10–13 °.

Synthesis of Ba2CaZn2Si6O17:Eu2+ Phosphors: Synthesis, Microstructure and Luminescence Characteristics

In this investigation, Ba2CaZn2Si6O17:Eu2+ phosphor (BCZSOE) was successfully synthesized through the facile solid-state approach. Accordingly, spherical/commercial SiO2 particles were used through synthesizing BCZSOE phosphors. The crystal structure and microstructure of the produced phosphors were characterized using powder X-ray diffraction, field emission scanning electron microscope and high-resolution transmission electron microscope (HRTEM) instruments, while the luminescence properties of BCZSOE materials were analyzed by a photoluminescence (PL) analyzer. It was interestingly found that the use of spherical silica resulted in an uniform grain size distribution of BCZSOE phosphor in the range of 120–180 nm. In addition, the HRTEM images showed that the soaking time within the solid-state procedure was one of the most important parameters for the successful synthesis of BCZSOE compound. The luminescence emission spectra revealed that the use of silica spheres gave rise to the enhanced emission intensity than that of commercial silica particles. In addition, it was concluded that the emission bands at the wavelengths of 447 and 505 nm were due to the substitution of Ca2+ and Ba2+ by Eu2+ ions, respectively.

Selective and Efficient Arsenic Recovery from Water through Quaternary Amino-Functionalized Silica.

The free-radical graft polymerization of acryloxyethyl-trimethylammonium chloride onto commercial silica particles was studied experimentally for extraction of arsenic ions from water. Two steps were used to graft acryloxyethyl-trimethylammonium chloride (Q) onto the surface of nanosilica: anchoring vinyltrimethoxysilane (VTMSO) onto the surface of silica to modify it with double bonds and then grafting Q onto the surface of silica with potassium persulfate as an initiator. The products were characterized by Fourier-transform infrared (FT-IR), the thermogravimetric analysis (TGA), scanning electron microscopy (SEM), 13C, 29Si nuclear magnetic resonance (NMR), and X-ray powder diffraction (XRD). The results showed that it is easy to graft Q onto the surface of silica under radical polimerization. The morphology analysis of silica and modified silica indicated that the silica decreased the size scale after modification. Q/VTMSO-SiO2 was tested for its ability to remove arsenic from drinking water. The results show that the new silica hybrid particles efficiently remove all arsenate ions. In addition, Q/VTMSO-SiO2 showed better sorption capacities for other metal ions (such as copper, zinc, chromium, uranium, vanadium, and lead) than a commercial water filter.

Dental Resin Composites with Enhanced Properties Bycommercial Silica Particles as Fillers

To explore the preparation of novel dental resin composites with enhanced properties, two commercial silica particles with sizes of around 1μm and 40 nm were chosen as inorganic fillers, and firstly surface functionalized by 3-methacryloxypropyltrimethoxysilane (γ-MPS) to incorporate cross-linkable vinyl groups onto the surface of fillers. Then the modified fillers were blended with organic monomers, bisphenolAdiglycidyldimethacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA), to fabricate the resin compositeswith a three-roll mixer.Resin composites with various weight percentage of fillers and component ratio of microparticle and nanoparticle were prepared. Surface functionalization of silica particles was characterized by fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), and mechanical properties degree of conversion, and depth of cure of the resultant resin composites were investigated byuniversal testing machineand FTIR. The results indicated that surface modification of silica particles was successful and the surface organic contents were 3.29% and 4.34%, respectively. Among the studied resin composites, the resin composite with 75 wt.% silica particles (59 wt.% microparticles and 16 wt.% nanoparticles) presented the highest value of depth of cure (5.52 ± 0.07 mm), and optimum mechanical properties such as flexural strength (149.8 ± 3.3 MPa), flexural modulus (13.8 ± 0.06 GPa), compressive strength (340.6 ± 8.3 MPa) and Vicker’smicrohardness (78.26 ± 2.45 HV). The study of dental resin composites fabricated from commercial silica particles with excellent properties might provide a new sight for realizing the preparation of this kind of dental resin composites in an industrial scale.

Uptake of bright fluorophore core-silica shell nanoparticles by biological systems.

Nanoparticles are used in a variety of consumer applications. Silica nanoparticles in particular are common, including as a component of foods. There are concerns that ingested nano-silica particles can cross the intestinal epithelium, enter the circulation, and accumulate in tissues and organs. Thus, tracking these particles is of interest, and fluorescence spectroscopic methods are well-suited for this purpose. However, nanosilica is not fluorescent. In this article, we focus on core-silica shell nanoparticles, using fluorescent Rhodamine 6G, Rhodamine 800, or CdSe/CdS/ZnS quantum dots as the core. These stable fluorophore/silica nanoparticles had surface characteristics similar to those of commercial silica particles. Thus, they were used as model particles to examine internalization by cultured cells, including an epithelial cell line relevant to the gastrointestinal tract. Finally, these particles were administered to mice by gavage, and their presence in various organs, including stomach, small intestine, cecum, colon, kidney, lung, brain, and spleen, was examined. By combining confocal fluorescence microscopy with inductively coupled plasma mass spectrometry, the presence of nanoparticles, rather than their dissolved form, was established in liver tissues.

Styrene grafted natural rubber reinforced by in situ silica generated via sol–gel technique

Abstract The filling of styrene graft natural rubber (ST-GNR) with in situ formed silica was performed using the sol–gel reaction via the latex solution method. The mechanical properties of ST-GNR/NR vulcanizate were improved when using the in situ formed silica to levels higher than those obtained with the commercial ex situ formed silica filled ST-GNR/NR vulcanizates at a comparable silica content of 12 parts by weight per hundred parts of rubber. Transmission electron microscopy analysis revealed that the in situ silica particles were small (∼40 nm diameter) and well dispersed, while the commercial silica particles were larger (∼60 nm diameter) and markedly agglomerated in the rubbery matrix. The mechanical properties of the composites prepared via both the solid rubber and latex solution methods were comparable.

The importance of silica morphology in silica–titania composites with dye sensitized solar functionality

Silica–titania composite dye sensitized solar cells were prepared by synthesizing crystalline titania around silica particles to test dye sensitized solar cell performance under conditions where current would flow primarily in surface regions. Three different commercial silica particles were used in this study — each with a different mean particle size and pore structure to give information about the coverage and connectedness of the chemically-derived surface titania layer. The silica–titania composite materials were characterized using scanning electron microscopy, X-ray diffraction and other techniques. The effect of surface area and porosity of the host silica particles on the morphology of the silica–titania layers and the performance in dye sensitized solar cells is discussed.

In situ silica reinforcement of methyl methacrylate grafted natural rubber by sol–gel process

In situ silica reinforcement of natural rubber (NR) grafted with methyl methacrylate (MMA) (MMA-GNR) was achieved via the sol–gel reaction of tetraethoxysilane (TEOS) by the use of solid rubber and latex solutions. Silica contents within the MMA-GNR as high as 48 and 19 phr were obtained when using the solid rubber and latex solutions, respectively, under optimum conditions. The conversion efficiency of TEOS to silica was close to 95%. The in situ formed silica MMA-GNR/NR composite vulcanizates were prepared. MMA-GNR/NR composite vulcanizates reinforced with the in situ formed silica prepared by either method had similar mechanical properties to each other, but a shorter cure time and higher mechanical properties than those reinforced with the commercial silica at 9 phr. The TEM micrographs confirmed that the in situ formed silica particles were well dispersed within the MMA-GNR/NR composite matrix, whilst the commercial silica particles showed a significant level of agglomeration and a lower level of dispersion.

A Generic Single‐Step Synthesis of Monodisperse Core/Shell Colloids Based on Spontaneous Pickering Emulsification

Monodisperse core–shell colloids are widely applied in various fields such as biomedicine, catalysis, and optics, and are also important for fundamental studies in colloid and interface science. The synthesis of particles with a well-defined core–shell morphology still comprises several separate steps such as core preparation, its subsequent functionalization with a coupling agent and the deposition of one or several shells. This multi-step approach towards composite colloids has some serious drawbacks. First, both coupling chemistry and synthetic pathways need to be specifically designed for the materials involved. Second, multi-step reactions often require intermediate purifications or separations that not only reduce the net yield but also hamper the up-scaling of composite-colloid synthesis for applications such as those referred to above. In this communication we report a novel single-step synthesis of monodisperse latex-based core–shell colloids that completely relies on self-assembly of the components involved (Fig. 1). Recently we discovered that nano-particles may induce spontaneous emulsification of oil in water to thermodynamically stable, monodisperse Pickering emulsions. This novel emulsification phenomenon, first observed for magnetite (Fe3O4) nano-particles, turns out to be quite generic since also cobalt ferrite (CoFe2O4) and commercial silica particles (Ludox) lead to stable Pickering emulsions. It was also shown that using the chemically reactive oil (methacryloxypropyltrimethoxysilane, TPM), Pickering emulsions could be polymerized by addition of a radical initiator (potassiumpersulphate, KPS) resulting in stable colloidal dispersions (Fig. 2a and b). Here we investigate the use of such particle-stabilized emulsions (hereafter TPM-emulsions) in a seeded growth polymethylmethacrylate (PMMA) polymerization, to obtain in one single and simple step, PMMA colloids with various inorganic cores. Initially we focused on TPM-emulsions merely as a source for monodisperse inorganic cores to seed a surfactant-free PMMA polymerization. However, exploring what would happen when TPM-emulsions are prepared directly in the presence of methylmethacrylate (MM) we noticed that, surprisingly, MM does not interfere at all with the TPM emulsification. In fact, during the latter emulsification, MM remains present as a separate oil phase (Fig. 2c insert). Addition of a water-soluble radical initiator, however, not only induces polymerization of the TPM-emulsion droplets to solid spheres, but simultaneously also triggers the polymerization of PMMA shells onto these spheres. Thus the floating MM phase (Fig. 2) acts as a monomer source for this PMMA shell formation and, indeed, the shell thickness continues to grow until the whole MM phase is consumed. It turns out that, in addition, polymerized TPM-emulsions are also excellent seeds dispersions for growing polystyrene shells via surfactant free emulsion polymerization, as well as silica shells via the classical Stober synthesis, showing that the spontaneous Pickering emulsification allows for the preparation of polymeric as well as inorganic composite model colloids. C O M M U N IC A TI O N

Photocatalytic Decolorization and Mineralization of Dyes with Nanocrystalline TiO2/SiO2 Materials

The application of photocatalytic technologies for the treatment of dyeing effluents from the textile industry has been shown to be economically competitive, especially when solar light drives the process. However, improvements in the catalysts are required to facilitate the separation stage. This work addresses the synthesis and characterization of nanocrystalline TiO2 (n-TiO2) incorporated into commercial silica particles and the activity of these materials in the photocatalytic treatment of three different azo dyes. The characterization of the n-TiO2/SiO2 photocatalysts shows differences in the average crystallite size that lead to significant differences in the values of the band gap energy of the semiconductor and also in activity. The molecular structure of the dyes also influences the kinetics of degradation, being almost independent of the TiO2 loading for Methyl Orange, which is opposite to the cases of Congo Red and Trypan Blue. This different behavior could arise from the existence of mass-tran...

Use of specially designed columns for antioxidants and antimicrobials enrichment by preparative supercritical fluid chromatography

A new, specially designed column has been developed for fractionation of supercritical fluid extract of rosemary by using a preparative supercritical fluid chromatography system (Prep-SFC). The column evaluated in this work was prepared using a new packing method consisting of a combination of slurry and supercritical CO2 with commercial silica particles coated with a stationary phase commonly used in gas chromatography, such as SE-54 (5% phenyl-, 95% methylsilicone). The new packing procedure provided columns with reasonable efficiencies, with high stability and useful at high-pressure range. A 25cm×10mm i.d. column packed with silica particles coated with 3% of SE-54 was prepared, and its separation power was tested for isolating fractions with high antioxidant and/or antimicrobial activity from a supercritical rosemary extract. The SFC conditions were selected based on a previous work done with a commercial LC-Diol packed column (130bar, 80°C), and different percentages of modifier in the mobile phase were tested (5 and 10%). Two cyclones were employed to collect the fractions which were then characterized by HPLC-diode array detection (DAD), GC, and in vitro antioxidant and antimicrobial assays. The use of coated packed columns allowed the fractionation of a complex mixture of rosemary supercritical extract with a minimum amount of modifier in the mobile phase (5% ethanol). At the optimum conditions it was possible to obtain two very active fractions in terms of antioxidant and antimicrobial activity, with no residual rosemary aroma and with improved activities compared to the original supercritical extract.

SiO 2/Cr monolayers and formation of polyethylene films

1,3,5-tribenzylhexahydro-1,3,5-triazine-CrCl 3 (TAC-CrCl 3) was supported on monodisperse Stöber silica and on commercial silica particles. The monolayers of these catalyst particles were successfully prepared with Langmuir–Blodgett technique. The effect of TAC-CrCl 3 molecules on the ordering and film-forming of the silica particles was investigated. The particles arrange in domains of hexagonal ordering, but the ordering of particles in the monolayer decreases with increasing Cr loading. These hybrid monolayers are active polymerization catalysts. After polymerization, a relatively rough layer of polyethylene molecules covers the catalyst monolayer and this layer is hydrophobic. The monolayers and the polymers coating films were characterized by IR, UV–vis-NIR, and SEM. The method provides a way to fabricate polyethylene films on silica monolayers.

Preparation of mesoporous carbon templated by silica particles for use as a catalyst support in polymer electrolyte membrane fuel cells

Mesoporous carbons were prepared using commercial silica particles and a formaldehyde–resorcinol resin as a template and carbon precursor, respectively. By changing the molar ratio of template to carbon precursor, mesoporous carbons with different mesoporosities (MC- X, X represents the molar ratio of template to carbon precursor) were produced. The resulting MCs had a high-surface area and large pore volume. In particular, the highest mesoporosity was observed for MC-3. Pt catalysts-supported on MC- X were prepared using formaldehyde as a reducing agent for use as a cathode catalyst in a polymer electrolyte fuel cell (PEMFC). The size of Pt crystallite was dependent on the properties of corresponding carbon support. As a whole, a carbon support with a high-surface area and high-mesoporosity served the best in terms of a high-dispersion of Pt nanoparticles. In a unit cell test of the PEMFC, a Pt catalyst with a high-mesoporosity and fine dispersion of metal showed an enhanced performance. The findings indicate that the surface area combined with the mesoporosity had a positive influence on the metal dispersion and the distribution of ionomer, leading to the enhanced cell performance.

Preparations of silica slurry for wafer polishing via controlled growth of commercial silica seeds

Silica slurry in aqueous medium for wafer polishing was prepared by sol-gel reaction of silicon alkoxide utilizing commercial silica particles as seeds that were grown stepwise through intermittent additions of tetraethylorthosilicate (TEOS) as a silica precursor. Before the growth reaction, the commercial silica particles were pre-treated in the vibratory mill partially filled with zirconia ball and the sonicator to ensure good dispersion. The alcohol left after growth reaction was removed by vacuum distillation and repeated washings with distilled water followed by centrifugations. Then, the alcohol-free silica particles were redispersed in water. The dispersion stability of the silica slurries was examined by measuring surface charge of silica particles and rheological properties. Finally, wafer-polishing performance of the prepared silica slurries was considered by measuring the polishing (or removal) rate, and RMS (root mean square) roughness of the polished wafer surface. For the polishing, MEA (monoethanolamine) and TMAH (tetramethylammonium hydroxide) were used as polishing accelerators. The polishing result showed that the removal rate was nearly independent of the concentrations of MEA and TMAH in the range of 0.3-0.5 wt% and 100-500 ppm, respectively. One of the most interesting features is that hydrothermal treatment of the prepared silica slurries in autoclave increased the removal rate as high as ten times. Although the removal rate was increased by the increased size of the abrasive particle, surface roughness of the polished wafer surface was deteriorated.