Showing papers on "Silicon dioxide published in 2014"

Effect of Silica Particle Size on Macrophage Inflammatory Responses

Abstract: Amorphous silica particles, such as nanoparticles (<100 nm diameter particles), are used in a wide variety of products, including pharmaceuticals, paints, cosmetics, and food. Nevertheless, the immunotoxicity of these particles and the relationship between silica particle size and pro-inflammatory activity are not fully understood. In this study, we addressed the relationship between the size of amorphous silica (particle dose, diameter, number, and surface area) and the inflammatory activity (macrophage phagocytosis, inflammasome activation, IL-1β secretion, cell death and lung inflammation). Irrespective of diameter size, silica particles were efficiently internalized by mouse bone marrow-derived macrophages via an actin cytoskeleton-dependent pathway, and induced caspase-1, but not caspase-11, activation. Of note, 30 nm-1000 nm diameter silica particles induced lysosomal destabilization, cell death, and IL-1β secretion at markedly higher levels than did 3000 nm-10000 nm silica particles. Consistent with in vitro results, intra-tracheal administration of 30 nm silica particles into mice caused more severe lung inflammation than that of 3000 nm silica particles, as assessed by measurement of pro-inflammatory cytokines and neutrophil infiltration in bronchoalveolar lavage fluid of mice, and by the micro-computed tomography analysis. Taken together, these results suggest that silica particle size impacts immune responses, with submicron amorphous silica particles inducing higher inflammatory responses than silica particles over 1000 nm in size, which is ascribed not only to their ability to induce caspase-1 activation but also to their cytotoxicity.

Electronic structure of silicon dioxide (a review)

Abstract: Silicon dioxide amorphous films are the key insulators in silicon integrated circuits. The physical properties of silicon dioxide are determined by the electronic structure of this material. The currently available information on the electronic structure of silicon dioxide has been systematized.

The effects of oxygen plasma and humidity on surface roughness, water contact angle and hardness of silicon, silicon dioxide and glass

Abstract: For heterogeneous integration in many More-than-Moore applications, surface preparation is the key step to realizing well-bonded multiple substrates for electronics, photonics, fluidics and/or mechanical components without a degradation in performance. Therefore, it is critical to understand how various processing and environmental conditions affect their surface properties. In this paper, we investigate the effects of oxygen plasma and humidity on some key surface properties such as the water contact angle, roughness and hardness of three materials: silicon (Si), silicon dioxide (SiO2) and glass, and their impact on bondability. The low surface roughness, high surface reactivity and high hydrophilicity of Si, SiO2 and glass at lower activation times can result in better bondability. Although, the surface reactivity of plasma-ambient-humidity-treated Si and SiO2 is considerably reduced, their reduction of roughness and increase of hydrophilicity may enable good bonding at low temperature heating due to augmented hydroxyl groups. The decrease of hardness of Si and SiO2 with increased activation time is attributed to higher surface roughness and the formation of amorphous layers of Si. While contact angle and surface roughness results show a correlation with bondability, the role of hardness on bondability requires further investigation.

Fluorescent nanodiamonds embedded in biocompatible translucent shells.

Abstract: H igh pressure high temperature (HPHT) nanodiamonds (NDs) represent extremely promising materials for construction of fl uorescent nanoprobes and nanosensors. However, some properties of bare NDs limit their direct use in these applications: they precipitate in biological solutions, only a limited set of bio-orthogonal conjugation techniques is available and the accessible material is greatly polydisperse in shape. In this work, we encapsulate bright 30-nm fl uorescent nanodiamonds (FNDs) in 10‐20-nm thick translucent (i.e., not altering FND fl uorescence) silica shells, yielding monodisperse near-spherical particles of mean diameter 66 nm. High yield modifi cation of the shells with PEG chains stabilizes the particles in ionic solutions, making them applicable in biological environments. We further modify the opposite ends of PEG chains with fl uorescent dyes or vectoring peptide using click chemistry. High conversion of this bio-orthogonal coupling yielded circa 2000 dye or peptide molecules on a single FND. We demonstrate the superior properties of these particles by in vitro interaction with human prostate cancer cells: while bare nanodiamonds strongly aggregate in the buffer and adsorb onto the cell membrane, the shell encapsulated NDs do not adsorb nonspecifi cally and they penetrate inside the cells.

The investigation of MCM-48-type and MCM-41-type mesoporous silica as oral solid dispersion carriers for water insoluble cilostazol

Abstract: Objective: To explore the suitable application of MCM-41 (Mobil Composition of Matter number forty-one)-type and MCM-48-type mesoporous silica in the oral water insoluble drug delivery system.Methods: Cilostazol (CLT) as a model drug was loaded into synthesized MCM-48 (Mobil Composition of Matter number forty-eight) and commercial MCM-41 by three common methods. The obtained MCM-41, MCM-48 and CLT-loaded samples were characterized by means of nitrogen adsorption, thermogravimetric analysis, ultraviolet-visible spectrophotometry, scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry and powder X-ray diffractometer.Results: It was found that solvent evaporation method was preferred according to the drug loading efficiency and the maximum percent cumulative drug dissolution. MCM-48 with 3D cubic pore structure and MCM-41 with 2D long tubular structure are nearly spherical particles in 300–500 nm. Nevertheless, the silica carriers with similar large specific...

Ion irradiation of the native oxide/silicon surface increases the thermal boundary conductance across aluminum/silicon interfaces

Abstract: The thermal boundary conductance across solid-solid interfaces can be affected by the physical properties of the solid boundary. Atomic composition, disorder, and bonding between materials can result in large deviations in the phonon scattering mechanisms contributing to thermal boundary conductance. Theoretical and computational studies have suggested that the mixing of atoms around an interface can lead to an increase in thermal boundary conductance by creating a region with an average vibrational spectra of the two materials forming the interface. In this paper, we experimentally demonstrate that ion irradiation and subsequent modification of atoms at solid surfaces can increase the thermal boundary conductance across solid interfaces due to a change in the acoustic impedance of the surface. We measure the thermal boundary conductance between thin aluminum films and silicon substrates with native silicon dioxide layers that have been subjected to proton irradiation and post-irradiation surface cleaning procedures. The thermal boundary conductance across the Al/native oxide/Si interfacial region increases with an increase in proton dose. Supported with statistical simulations, we hypothesize that ion beam mixing of the native oxide and silicon substrate within $\ensuremath{\sim}2.2\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ of the silicon surface results in the observed increase in thermal boundary conductance. This ion mixing leads to the spatial gradation of the silicon native oxide into the silicon substrate, which alters the acoustic impedance and vibrational characteristics at the interface of the aluminum film and native oxide/silicon substrate. We confirm this assertion with picosecond acoustic analyses. Our results demonstrate that under specific conditions, a ``more disordered and defected'' interfacial region can have a lower resistance than a more ``perfect'' interface.

Creating sub-50 nm nanofluidic junctions in a PDMS microchip via self-assembly process of colloidal silica beads for electrokinetic concentration of biomolecules

Abstract: In this work we describe a novel and simple self-assembly process of colloidal silica beads to create a nanofluidic junction between two microchannels. The nanoporous membrane was used to induce ion concentration polarization inside the microchannel and this electrokinetic preconcentration system allowed rapid concentration of DNA samples by ~1700 times and of protein samples by ~100 times within 5 minutes.

Effect of mesoporous silica nanoparticles on dentinal tubule occlusion: an in vitro study using SEM and image analysis.

Abstract: The occlusion of dentinal tubules is considered to be an effective strategy to treat dentin hypersensitivity. This in vitro study introduced mesoporous silica nanoparticles (MSNs) for tubular occlusion to achieve deeper sealing. Further, MSNs with independently encapsulated calcium and phosphates (as calcium and phosphate sources) (Ca(2+)/PO₄(3-)@MSNs) were introduced to achieve improved efficacy of tubular occlusion and remineralization. MSNs or Ca(2+)/PO₄(3-)@MSNs were proportionally mixed with distilled water to make their respective desensitizing slurries, which were used to treat dentin surfaces. The efficacy of tubular occlusion was evaluated using scanning electron microscopy (SEM) images and an image analyzer, and compared with that achieved with Green-Or -a commonly used densitizer. The results demonstrated that both MSNs and Ca(2+)/PO₄(3-)@MSNs almost completely occluded dentinal tubules and formed a deeper seal which penetrated about 105 μm deep into the dentinal tubules. Significant differences in tubular occlusion were observed between Green-Or densitizer and MSNs or Ca(2+)/PO₄(3-)@MSNs. The novel MSNs-based nanomaterials showed great potential as a treatment option for dentin hypersensitivity.

Poly(γ-glutamic acid)/silica hybrids with calcium incorporated in the silica network by use of a calcium alkoxide precursor

Abstract: Current materials used for bone regeneration are usually bioactive ceramics or glasses. Although they bond to bone, they are brittle. There is a need for new materials that can combine bioactivity with toughness and controlled biodegradation. Sol-gel hybrids have the potential to do this through their nanoscale interpenetrating networks (IPN) of inorganic and organic components. Poly(γ-glutamic acid) (γ-PGA) was introduced into the sol-gel process to produce a hybrid of γ-PGA and bioactive silica. Calcium is an important element for bone regeneration but calcium sources that are used traditionally in the sol-gel process, such as Ca salts, do not allow Ca incorporation into the silicate network during low-temperature processing. The hypothesis for this study was that using calcium methoxyethoxide (CME) as the Ca source would allow Ca incorporation into the silicate component of the hybrid at room temperature. The produced hybrids would have improved mechanical properties and controlled degradation compared with hybrids of calcium chloride (CaCl2), in which the Ca is not incorporated into the silicate network. Class II hybrids, with covalent bonds between the inorganic and organic species, were synthesised by using organosilane. Calcium incorporation in both the organic and inorganic IPNs of the hybrid was improved when CME was used. This was clearly observed by using FTIR and solid-state NMR spectroscopy, which showed ionic cross-linking of γ-PGA by Ca and a lower degree of condensation of the Si species compared with the hybrids made with CaCl2 as the Ca source. The ionic cross-linking of γ-PGA by Ca resulted in excellent compressive strength and reduced elastic modulus as measured by compressive testing and nanoindentation, respectively. All hybrids showed bioactivity as hydroxyapatite (HA) was formed after immersion in simulated body fluid (SBF).

Adsorption and Release of siRNA from Porous Silica

Abstract: Porous silica particles are potential transfection agents for nucleic acid-based therapies because of their large specific surface areas and pore volumes and the ease with which they can be chemically modified to maximize the loading of cargo and to effect targeting in vivo. Here, we present a systematic study of the effects of pore size and pore modification on the adsorption and release of short, interfering RNA (siRNA) from a mesoporous silica particle developed in our laboratory. Using adsorption isotherms and release experiments, we found that the short polyamine diethylenetriamine was the best chemical modification for achieving both the adsorption and release of large amounts of siRNA. The degree of functionalization with diethylenetriamine caused drastic changes in the loading capacity and binding strength of siRNA to silica with relatively large pores (8 nm and larger), but the degree of functionalization had a weaker effect in narrow pores (4 nm). Multilayer adsorption could occur in materials with large pores (15 nm). Release experiments showed that intermediate pore sizes and intermediate degrees of functionalization resulted in the best compromise between maximizing loading (from strong adsorption) and maximizing release. Capillary electrophoresis and quantitative, real-time PCR demonstrated that siRNA was released intact and that these particles functioned as a transfection agent of mammalian cells in vitro.

Synthesis and Organic Surface Modification of Luminescent, Lanthanide-Doped Core/Shell Nanomaterials (LnF3@SiO2@NH2@Organic Acid) for Potential Bioapplications: Spectroscopic, Structural, and in Vitro Cytotoxicity Evaluation

Abstract: A facile coprecipitation reaction between Ce(3+), Gd(3+), Tb(3+), and F(-) ions, in the presence of glycerine as a capping agent, led to the formation of ultrafine, nanocrystalline CeF3:Tb(3+) 5%, Gd(3+) 5% (LnF3). The as-prepared fluoride nanoparticles were successfully coated with an amine modified silica shell. Subsequently, the obtained LnF3@SiO2@NH2 nanostructures were conjugated with 4-ethoxybenzoic acid in order to prove the possibility of organic modification and obtain a new functional nanomaterial. All of the nanophosphors synthesized exhibited intense green luminescence under UV light irradiation. Based on TEM (transmission electron microscopy) measurements, the diameters of the cores (≈12 nm) and core/shell particles (≈50 nm) were determined. To evaluate the cytotoxic activity of the nanomaterials obtained, their effect on human erythrocytes was investigated. LnF3 nanoparticles were bound to the erythrocyte membrane, without inducing any cytotoxic effects. After coating with silica, the nanoparticles revealed significant cytotoxicity. However, further functionalization of the nanomaterial with -NH2 groups as well as conjugation with 4-ethoxybenzoic acid entailed a decrease in cytotoxicity of the core/shell nanoparticles.

Porous silicon carbon composite microsphere with yolk-eggshell structure and preparation method therefor

Abstract: The invention provides a porous silicon carbon composite microsphere with a yolk-eggshell structure and a preparation method therefor, and belongs to the lithium ion battery electrode material technology field. The porous silicon carbon composite microsphere takes a porous submicron silicon sphere mpSi as a core with a diameter of 400-900 nm, and takes porous carbon mpC as a shell with a thickness of 10-60 nm. The inner diameter of a cavity Void is 800-1400 nm. The composition of the silicon carbon composite microsphere can be described as mpSi@Void@mpC. In addition, In the preparation method, cheap silicon dioxide is taken as a silicon source, silicon dioxide is conversed into silicon materials with electrochemical activities through a magnesiothermic reduction method. The size of gaps can be regulated and controlled through control of etching conditions. The preparation method is advantaged in that the material structure can be controlled, the cost is low, the process is simple, and the composite microsphere is convenient for large-scale production.

Cerium Oxide Coating of Titanium Dioxide Pigment to Decrease Its Photocatalytic Activity

Abstract: The use of cerium oxide coating of titanium dioxide pigments to decrease photocatalytic activity was studied. A large decrease in the photocatalytic activity of titanium dioxide particles coated with cerium oxide was obtained even with a tiny coating amount of 0.2 wt %, and these particles were more stable than those with the conventional 2.0 wt % film coating of silicon dioxide or 1.5 wt % aluminum oxide. The combination film coatings of cerium oxide and silicon or aluminum oxide showed smaller decreases in photocatalytic activity. Both Ce(III) and Ce(IV) oxide coatings gave highly decreased photocatalytic activity, even when the cerium oxide coating did not completely cover the surface. It was inferred that the efficient decrease of photocatalytic activity was because the unpaired electrons in the 4f orbital of cerium enabled the coating film to capture electrons and holes that were produced when titanium dioxide was exposed to ultraviolet irradiation.

Uranium Incorporation into Amorphous Silica

Abstract: High concentrations of uranium are commonly observed in naturally occurring amorphous silica (including opal) deposits, suggesting that incorporation of U into amorphous silica may represent a natural attenuation mechanism and promising strategy for U remediation. However, the stability of uranium in opaline silicates, determined in part by the binding mechanism for U, is an important factor in its long-term fate. U may bind directly to the opaline silicate matrix, or to materials such as iron (hydr)oxides that are subsequently occluded within the opal. Here, we examine the coordination environment of U within opaline silica to elucidate incorporation mechanisms. Precipitates (with and without ferrihydrite inclusions) were synthesized from U-bearing sodium metasilicate solutions, buffered at pH ∼ 5.6. Natural and synthetic solids were analyzed with X-ray absorption spectroscopy and a suite of other techniques. In synthetic amorphous silica, U was coordinated by silicate in a double corner-sharing coordination geometry (Si at ∼ 3.8-3.9 A) and a small amount of uranyl and silicate in a bidentate, mononuclear (edge-sharing) coordination (Si at ∼ 3.1-3.2 A, U at ∼ 3.8-3.9 A). In iron-bearing synthetic solids, U was adsorbed to iron (hydr)oxide, but the coordination environment also contained silicate in both edge-sharing and corner-sharing coordination. Uranium local coordination in synthetic solids is similar to that of natural U-bearing opals that retain U for millions of years. The stability and extent of U incorporation into opaline and amorphous silica represents a long-term repository for U that may provide an alternative strategy for remediation of U contamination.

Silicon dioxide aerogel material and preparation method thereof

Abstract: The invention relates to a silicon dioxide aerogel material and a preparation method thereof. The method comprises the following steps: by using water glass as silicon source, adding an acid-containing organic solvent free of chlorine ions and fluorine ions to generate a precipitate of sodium ions, potassium ions and other metal salt ions, filtering to remove the precipitate to obtain high-purity silica sol, carrying out a sol-gel process, aging, acidifying, modifying, and drying to obtain the silicon dioxide aerogel material. The acidification before modification enhances the surface reaction activity of the silicon gel, thereby obviously enhancing the modification effect and efficiency. The method has the advantages of low cost and simple and efficient technique, is beneficial to mass high-efficiency production, is free of chlorine ions and fluorine ions in the whole technical process, and enhances the equipment operation safety and reliability; and the product can be used for heat preservation and thermal insulation of nuclear power and liquefied natural gas equipment and pipelines with higher requirement for corrosion resistance, and can also be used for thermal insulation in the field of aerospace, petrochemical engineering, track transportation, ships, automobiles, construction and the like.

Emission mechanisms of Si nanocrystals and defects in SiO 2 materials

Abstract: Motivated by the necessity to have all silicon optoelectronic circuits, researchers around the world are working with light emitting silicon materials. Such materials are silicon dielectric compounds with silicon content altered, such as silicon oxide or nitride, enriched in different ways with Silicon. Silicon Rich Oxide or silicon dioxide enriched with silicon, and silicon rich nitride are without a doubt the most promising materials to reach this goal. Even though they are subjected to countless studies, the light emission phenomenon has not been completely clarified. So, a review of different proposals presented to understand the light emission phenomenon including emissions related to nanocrystals and to point defects in SiO2 is presented.

Adsorption of lysozyme on hyaluronic acid functionalized SBA-15 mesoporous silica: a possible bioadhesive depot system.

Abstract: Silica-based ordered mesoporous materials are very attractive matrices to prepare smart depot systems for several kinds of therapeutic agents. This work focuses on the well-known SBA-15 mesoporous silica and lysozyme, an antimicrobial protein. In order to improve the bioadhesion properties of SBA-15 particles, the effect of hyaluronic acid (HA) functionalization on lysozyme adsorption was investigated. SBA-15 samples having high (H-SBA) and low (L-SBA) levels of functionalization were analyzed during the three steps of the preparations: (1) introduction of the -NH2 groups to obtain the SBA-NH2 samples; (2) functionalization with HA to obtain the SBA-HA matrices; (3) adsorption of lysozyme. All silica matrices were characterized through N2-adsorption/desorption isotherms, small-angle X-ray scattering, transmission electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The whole of the experimental data suggests that a high level of functionalization of the silica surface allows for a negligible lysozyme adsorption mainly due to unfavorable electrostatic interactions (H-SBA-NH2) or steric hindrance (H-SBA-HA). A low degree of functionalization of the silica surface brings about a very good performance toward lysozyme adsorption, being 71% (L-SBA-NH2) and 63% (L-SBA-HA) respectively, compared to that observed for original SBA-15. Finally, two different kinetic models--a "pseudo-second order" and a "intraparticle diffusion"--were compared to fit lysozyme adsorption data, the latter being more reliable than the former.

Graphene-mediated surface enhanced Raman scattering in silica mesoporous nanocomposite films

Abstract: Silica mesoporous nanocomposite films containing graphene nanosheets and gold nanoparticles have been prepared via a one-pot synthesis using silicon tetrachloride, gold(III) chloride tetrahydrate, a 1-N-vinyl-2-pyrrolidone dispersion of exfoliated graphene and Pluronic F127 as a structuring agent. The composite films have shown graphene-mediated surface-enhanced Raman scattering (G-SERS). Graphene has been introduced as dispersed bilayer sheets while gold has been thermally reduced in situ to form nanoparticles of around 6 nm which preferentially nucleate on the surface of the graphene nanosheets. The presence of graphene and gold nanoparticles does not interfere with the self-assembly process and the formation of silica mesoporous films ordered as 2D hexagonal structures. The material has shown a remarkable analytical enhancement factor ranging from 80 up to 136 using rhodamine 6G as a Raman probe. The films have been characterised by grazing incidence X-ray diffraction, FTIR and UV-vis spectroscopy studies; transmission electron microscopy and spectroscopic ellipsometry have been used to study the morphology, thickness and porosities of the samples. Raman spectroscopy has been employed to characterise the graphene nanosheets embedded into the mesoporous films and the enhanced Raman scattering.

High performance transistors based on the controlled growth of triisopropylsilylethynyl-pentacene crystals via non-isotropic solvent evaporation

Abstract: Triisopropylsilylethynyl-pentacene (TIPS-PEN) has proven to be one of the most promising small molecules in the field of molecular electronics, due to its unique features in terms of stability, performance and ease of processing Among a wide variety of well-established techniques for the deposition of TIPS-PEN, blade-metered methods have recently gained great interest towards the formation of uniform crystalline films over a large area Following this rationale, we herein designed a versatile approach based on blade-coating, which overcomes the problem of anisotropic crystal formation by manipulating the solvent evaporation behaviour, in a way that brings about a preferential degree of crystal orientation The applicability of this method was evaluated by fabricating field-effect transistors on glass as well as on silicon dioxide/silicon (SiO2/Si) substrates Interestingly, in an attempt to improve the rheological and wetting behaviour of the liquid films on the SiO2/Si substrates, we introduced a polymeric interlayer of polystyrene (PS) or polymethylmethacrylate (PMMA) which concurrently acts as passivation and crystallization assisting layer In this case, the synergistic effects of the highly-ordered crystalline structure and the oxide surface modification were thoroughly investigated The overall performance of the fabricated devices revealed excellent electrical characteristics, with high saturation mobilities up to 072 cm2 V−1 s−1 (on glass with polymeric dielectric), on/off current ratio >104 and low threshold voltage values (<−5 V)

Fungus-Mediated Preferential Bioleaching of Waste Material Such as Fly - Ash as a Means of Producing Extracellular, Protein Capped, Fluorescent and Water Soluble Silica Nanoparticles

Abstract: In this paper, we for the first time show the ability of the mesophilic fungus Fusarium oxysporum in the bioleaching of waste material such as Fly-ash for the extracellular production of highly crystalline and highly stable, protein capped, fluorescent and water soluble silica nanoparticles at ambient conditions. When the fungus Fusarium oxysporum is exposed to Fly-ash, it is capable of selectively leaching out silica nanoparticles of quasi-spherical morphology within 24 h of reaction. These silica nanoparticles have been completely characterized by UV-vis spectroscopy, Photoluminescence (PL), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Energy dispersive analysis of X-rays (EDAX).