Nanosized Silicon Dioxide Research Articles

Influence of Nanosized Silicon Oxide on the Luminescent Properties of ZnO Nanoparticles

For practical use of nanosized zinc oxide as the phosphor its luminescence quantum yields should be maximized. The aim of this work was to enhance luminescent properties of ZnO nanoparticles and obtain high-luminescent ZnO/SiO2composites using simpler approaches to colloidal synthesis. The luminescence intensity of zinc oxide nanoparticles was increased about 3 times by addition of silica nanocrystals to the source solutions during the synthesis of ZnO nanoparticles. Then the quantum yield of luminescence of the obtained ZnO/SiO2composites is more than 30%. Such an impact of silica is suggested to be caused by the distribution of ZnO nanocrystals on the surface of silica, which reduces the probability of separation of photogenerated charges between the zinc oxide nanoparticles of different sizes, and as a consequence, there is a significant increase of the luminescence intensity of ZnO nanoparticles. This way of increasing nano-ZnO luminescence intensity facilitates its use in a variety of devices, including optical ultraviolet and visible screens, luminescent markers, antibacterial coatings, luminescent solar concentrators, luminescent inks for security printing, and food packaging with abilities of informing consumers about the quality and safety of the packaged product.

Effect of SiO 2 nano-particles and nano-wires on microstructure and pinning properties of YBa 2 Cu 3 O 7-d

A comparative study of the effects of nanosized silicon oxide nano-particle (NP) and nano-wire (NW) additions during the final processing stage on the microstructure and superconducting properties of polycrystalline YBa2Cu3Oy (YBCO, or Y-123) was carried out. Samples were synthesized in air using a standard solid state reaction technique by adding nanosized entities up to 1 wt. %. Phases, microstructure, superconductivity, have been systematically investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrical measurements. TEM investigation shows the presence of inhomogeneities embedded in the superconducting matrix along with the presence of columnar defects in the case of SiO2 nano-particles added, however nano-wires tend to agglomerate by entangling with each other in the inter-grain regions. The critical current density of the samples was examined using current–voltage, ac-susceptibility and magnetization measurements. The results are discussed in the framework of Bean's critical state model. Flux pinning force density is calculated and the possible pinning mechanisms prevalent in sintered samples are determined. The flux creep activation energy is determined in the light of vortex dynamics exhibited by the frequency dependence of the AC susceptibility. We have clear indication that a relatively low concentration of nanosized silicon oxide improves the pinning properties of Y-123 and we also validated the impact of the shape of nanosized inclusions on the superconducting properties.

The Effect of Uv Irradiation on the Structure and Properties at Elevated Temperature of a “Linear Polyethylene–Nanosized Silicon Dioxide” Crystallising System

For the case of a large-tonnage plastic (linear polyethylene) containing additions of nanosized silicon dioxide, it has been shown experimentally that thermomechanical and photochemical action on the obtained polymer nanocomposites leads to a change in the molecular and supermolecular structure of the polymer such that there is an increase in the strength of the materials at a temperature exceeding the equilibrium temperature of melting of polyethylene, and an increase in their softening point.

Inhibited corrosion-promotion activity of graphene encapsulated in nanosized silicon oxide

The corrosion-promotion activity of graphene is inhibited when graphene is encapsulated in insulating SiO2 because SiO2 can act as a spacer isolating graphene from the metal substrate so as to prevent graphene–metal micro-galvanic corrosion. Incorporating rGO@SiO2 nanosheets into a polymer coating also greatly enhances the corrosion resistance of the coating.

Characteristics of pulsed plasma-chemical synthesis of silicon dioxide nanoparticles

This paper investigates the effect of plasma-chemical synthesis modes of nanosized silicon dioxide initiated by a pulsed electron beam on the geometric size distribution of the product nanoparticles. Findings show that the particles are enlarged following multiple exposures to a pulsed electron beam. Meanwhile, when adding a buffer gas into the initial mixture, the size of the particles decreases.

Ecotoxicological Effect of Nano-silicon Dioxide Particles on Daphnia Magna

Engineering nanoparticles (ENPs) have been widely used in many areas in virtue of its special physical and chemical properties. And ENPs are one of the major innovative scientific and economic growth things, which may present a variety of questions for organisms and environment. This paper analyzed the ecotoxicological effect of the nanosized silicon dioxide (Nano-SiO2) and the normal sized silicon dioxide (Nor-SiO2) within 24 hours as its bulk counterpart to Daphnia magna with different concentration. To assess the aquatic ecosystem safety, EC50 value for immobilization and LC50 value for mortality were measured respectively. The results show that the toxicity of Nano-SiO2 has obviously dose-dependent effect but the Nor-SiO2 has not, evidently. The optical microscope and digital camera also been used to observe and record the biological form of Daphnia magna during the exposure and in this study we found that D. magna can uptake and adsorb Nano-SiO2 but only apparently show uptaking to its bulk counterpart. The conclusions of results suggest that there is potential harm to aquatic environment in using Nano-SiO2, and it should deserve special concern.

Mechanochemical Reaction in a Polymer–Nanosized Silicon Dioxide System

We have used IR spectroscopy and x-ray diffraction to study "mechanocomposites" obtained by joint mechanical activation of polymers (polyamide, Sevilen, and poly-N-vinylpyrrolidone) with nanosized silicon dioxide in a highenergy ball mill. We have established that for <10 wt.% polymer in the initial mixture, mechanocomposites are formed with chemical bonding between components via bridges of adsorbed water.

Study of the process of the formation of Mg(Fe0.8Ga0.2)2O4 − δ films on Si

Conditions of the synthesis of magnetic semiconductor films of composition Mg(Fe0.8Ga0.2)2O4−δ on silicon have been optimized. As the barrier layer, which prevents the interaction between the film and the substrate during high-temperature crystallization of the films, a film of nanosized silicon dioxide was used. This, together with a high homogeneity of the composition of the target, allowed us to obtain Mg(Fe0.8Ga0.2)2O4−δ films on silicon characterized by the saturation magnetization (37 A m2/kg) that noticeably exceeds that for the volumetric analog (28 A m2/kg).

The study on SiO2 nanoparticles and nanowires added YBCuO: Microstructure and normal state electrical properties

The effects of nanosized silicon oxide nanoparticles and nanowires additions on the microstructure and the normal state transport properties of polycrystalline YBa2Cu3Oy (YBCO, or Y-123) were systematically studied. Samples were synthesized in air using a standard solid state reaction technique by adding nanosized entities up to 3wt.%. Phases, microstructure, superconductivity, have been systematically investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrical measurements. When nanosized SiO2 entities are added to the YBCO the orthorhombic structure is maintained. SEM results reveal that the grain size is reduced with increasing the content of SiO2. TEM investigation shows the presence of inhomogeneities embedded in the superconducting matrix along with the presence of columnar defects in the case of SiO2 nanoparticles added samples. Nanowires tend to agglomerate by entangling with each other in the intergrain regions. To analyze the normal state properties of the samples, the percolation theory based on localized states is applied. A change from Coulomb gap to variable-range hopping mechanisms is observed as a result of increasing the nano-entities concentration. The SiO2 nanowires addition modifies the electrical behavior of samples from metallic to insulating with a much lower concentration comparatively to SiO2 nanoparticles addition. The localization length d and the range hopping R of samples are estimated.

Electro-Physical Properties of Composites with Nano-Sized Oxides

Polymer matrix nano-sized oxide composites were fabricated by using a modified injection molding in which nano-sized silicon oxide and nano-sized magnesium oxide were contained. Thermal decomposition and evaporation of organic resin depended on the composition of the composites. Nano-sized oxides were uniformly distributed in the composites produced by a modified injection molding combining vacuum degassing and curing at a moderate temperature. 0.2 wt.% of silicon oxide addition to epoxy resin showed the maximum electric field of 3.6, whereas, 2.0 wt.% of magnesium oxide addition was required to reach the same value of electrical field. Both of thermal conductivity and thermal diffusivity of the nano-sized silicon oxide-epoxy composites tended to be increased with silicon oxide content. The relative permittivity of the nano-sized silicon oxide-epoxy composites increased from 5.16 to 5.31 by adding 0.6 wt.% silicon oxide, whereas, magnesium oxide addition up to 2.0 wt.% little influenced to the permittivity. Epoxy matrix-nano-sized silicon oxide composites were more suitable than magnesium oxide for the high performance capacitance.

English

The aim of this work was to improve the&nbsp;in vitro&nbsp;dissolution of simvastatin through development of self-nanoemulsifying tablets. Various modified oils, surfactant and co-surfactant mixtures were used to prepare different self-nanoemulsifying drug delivery systems (SNEDDS) whose composition was optimized using drug-solubility, ternary phase diagram, system stability and droplet size distribution studies. Optimized SNEDDSs, with acceptable surfactant ratio, stability and particle size (nano-range) upon dilution with simulated gastric fluid (SGF, pH 1.2) under gentle agitation conditions, were loaded onto microcrystalline cellulose and nano-size colloidal silicon dioxide powders using loading factor (Lf) = 0.2 and excipient ratio (R) = 20. Prepared powders were compressed into tablets and the&nbsp;in vitroperformance of the prepared self-nanoemulsifying tablets was investigated. Results revealed that systems with 10% relatively polar oils (C8), 60% Cremophore&reg;&nbsp;RH 40 (surfactant), and 30% Transcutol&reg;&nbsp;HP (co-surfactant), acquired good self-nanoemulsification properties either in liquid or tableted forms. Prepared self-nanoemulsifying tablets demonstrated significantly higher dissolution rates, compared to direct compression tablets (DCT) and marketed tablet (Zocor&reg;). In conclusion, self-nanoemulsifying tablets were able to introduce simvastatin successfully in a unique immediate-release solid dosage form. &nbsp; Key words:&nbsp;Simvastatin, self-nanoemulsifying tablets, self-nanoemulsifying drug delivery systems (SNEDDS), droplet size.

Stability of a nanopowder boundary-layer flow on a concave plate

Using hot-wire probe measurements, the mean and fluctuating velocities in a boundary layer on a concave plate immersed in the flow of a nanosized silicon dioxide powder are studied. A region of destabilization of disturbances is detected.

Injury on Blood Systems Caused by Silicon Dioxide Nanoparticles

Nano-sized silicon dioxide (SiO2) is widely utilized in artificial bone, artificial tooth, interventional catheters and drug delivery system，so it is imperative to study SiO2 NPs on the role of the body damage. Consulted with standard reference of GB/T16886, 20 and 80 nm SiO2 NPs were selected to prepare suspension (1mg/ml) for subacute systemic toxicity; 2000mg/ml suspension for MTT; and extracts (0.1g/ml) for hemolytic test. The results show that the hemolysis rate are all more than 5%, after its continuous injection of 2W nanoparticles into SD rats and New Zealand Rabbits, the alterations on the hemoglobin, hematocrit, mean corpuscular volume and other indicators have gained in blood routine test, and there was a marked inhibition on the L929 cells of SiO2 NPs. Therefore, these two kinds of particle size of SiO2 NPs have certain extent of injury effect on the blood system, and the contact time of NPs in the blood compatibility evaluation has play a more important role than the others.

Applying dry powder coatings to pharmaceutical powders using a comil for improving powder flow and bulk density

A method for applying nano-sized silicon dioxide guest particles onto host pharmaceutical particles (a.k.a. “dry-coating” or “nanocoating”) has been developed using conventional pharmaceutical processing equipment. It has been demonstrated that under selected conditions, a comil can be used to induce sufficient shear to disperse silicon dioxide particles onto the surfaces of host particles such as active pharmaceutical ingredients (API) without significant host particle attrition. In accordance with previous studies on dry coating, the dispersed silicon dioxide adheres to the host particle surface through van der Waals attractions, and reduces bulk powder cohesion. In this work, laboratory and pilot scale comils were used to dry coat pharmaceutical API and excipient powders with 1% w/w silicon dioxide by passing them through the mill with an appropriate combination of screen and impeller. In general, the uncoated powders exhibited poor flow and/or low bulk density. After dry coating with a comil, the powders exhibited a considerable and in some cases outstanding improvement in flow performance and bulk density. This coating process was successful at both the laboratory and pilot scale with similar improvements in flow. The superior performance of the coated powders translated to subsequent formulated blends, demonstrating the benefit of using nanocoated powders over uncoated powders. This particle engineering work describes the first successful demonstration of using a traditional pharmaceutical unit operation that can be run continuously to produce uniform nanocoating and highlights the substantial improvements to powder flow properties when this approach is used.

Adverse Effect of Nano-Silicon Dioxide on Lung Function of Rats with or without Ovalbumin Immunization

BackgroundThe great advances of nanomaterials have brought out broad important applications, but their possible nanotoxicity and risks have not been fully understood. It is confirmed that exposure of environmental particulate matter (PM), especially ultrafine PM, are responsible for many lung function impairment and exacerbation of pre-existing lung diseases. However, the adverse effect of nanoparticles on allergic asthma is seldom investigated and the mechanism remains undefined. For the first time, this work investigates the relationship between allergic asthma and nanosized silicon dioxide (nano-SiO2).Methodology/Principal FindingsOvalbumin (OVA)-treated and saline-treated control rats were daily intratracheally administered 0.1 ml of 0, 40 and 80 µg/ml nano-SiO2 solutions, respectively for 30 days. Increased nano-SiO2 exposure results in adverse changes on inspiratory and expiratory resistance (Ri and Re), but shows insignificant effect on rat lung dynamic compliance (Cldyn). Lung histological observation reveals obvious airway remodeling in 80 µg/ml nano-SiO2-introduced saline and OVA groups, but the latter is worse. Additionally, increased nano-SiO2 exposure also leads to more severe inflammation. With increasing nano-SiO2 exposure, IL-4 in lung homogenate increases and IFN-γ shows a reverse but insignificant change. Moreover, at a same nano-SiO2 exposure concentration, OVA-treated rats exhibit higher (significant) IL-4 and lower (not significant) IFN-γ compared with the saline-treated rats. The percentages of eosinophil display an unexpected result, in which higher exposure results lower eosinophil percentages.Conclusions/SignificanceThis was a preliminary study which for the first time involved the effect of nano-SiO2 to OVA induced rat asthma model. The results suggested that intratracheal administration of nano-SiO2 could lead to the airway hyperresponsiveness (AHR) and the airway remolding with or without OVA immunization. This occurrence may be due to the Th1/Th2 cytokine imbalance accelerated by the nano-SiO2 through increasing the tissue IL-4 production.

One step sol–gel method for the formation of etch free texturing, anti-reflection coatings, and p–n junction for silicon solar cells

This study evaluated one step sol–gel process for the simultaneous formation of surface texturing without a series of chemical etching processes, as well as anti-reflection coatings without complicated vacuum processes and p–n junctions. The solutions for this process were prepared from a proper combination of precursors containing phosphorus and nano-size silicon dioxide particles. The specimen heat treated at 1000 °C showed the lowest reflectivity of 9% at a wavelength of 650 nm. In addition, the I–V test confirmed formation of a p–n junction. Therefore, the production of solar cells may be reduced to two steps, sol–gel and electrode printing.

Effects of nano-sized silicon dioxide on the structures and activities of three functional proteins

Nanomaterials are finding increasing use in industrial production and daily life. However, human exposure to them may cause health risks. Nano-SiO 2 was selected as a representative nanomaterial and its potential effects were investigated in terms of its interactions with cytochrome c (cyt c), deoxyribonuclease (DNase II) and hemoglobin (Hb). The interactions accorded with Langmuir isothermal adsorption; the saturation binding numbers for cyt c, DNase II and Hb were 42 ± 5, 24 ± 2 and 1.1 ± 0.1 μmol/g nano-SiO 2 particle at pH 7.4, respectively, and the corresponding stability constants were 6.15 × 105, 1.79 × 106 and 2.6 × 107 M −1. On the basis of the binding constants and of ζ-potential fluorescence and circular dichroism (CD) measurements and scanning electronic microscopy (SEM), it was found that the three functional proteins can bridge nano-SiO 2 particles via charge attraction and hydrogen bonding and aggregate them into coralloid forms. The interactions also changed the secondary structures of the proteins and inhibited their static and dynamic activities. It may reasonably be deduced that exposure to nano-size silicon dioxide particles e.g. as drug carriers may have an unfavorable effect on human health by inactivating functional proteins.

A novel method to detect unlabeled inorganic nanoparticles and submicron particles in tissue by sedimentation field-flow fractionation

A novel methodology to detect unlabeled inorganic nanoparticles was experimentally demonstrated using a mixture of nano-sized (70 nm) and submicron (250 nm) silicon dioxide particles added to mammalian tissue. The size and concentration of environmentally relevant inorganic particles in a tissue sample can be determined by a procedure consisting of matrix digestion, particle recovery by centrifugation, size separation by sedimentation field-flow fractionation (SdFFF), and detection by light scattering.BackgroundLaboratory nanoparticles that have been labeled by fluorescence, radioactivity, or rare elements have provided important information regarding nanoparticle uptake and translocation, but most nanomaterials that are commercially produced for industrial and consumer applications do not contain a specific label.MethodsBoth nitric acid digestion and enzyme digestion were tested with liver and lung tissue as well as with cultured cells. Tissue processing with a mixture of protease enzymes is preferred because it is applicable to a wide range of particle compositions. Samples were visualized via fluorescence microscopy and transmission electron microscopy to validate the SdFFF results. We describe in detail the tissue preparation procedures and discuss method sensitivity compared to reported levels of nanoparticles in vivo.ConclusionTissue digestion and SdFFF complement existing techniques by precisely identifying unlabeled metal oxide nanoparticles and unambiguously distinguishing nanoparticles (diameter<100 nm) from both soluble compounds and from larger particles of the same nominal elemental composition. This is an exciting capability that can facilitate epidemiological and toxicological research on natural and manufactured nanomaterials.

Sorption and Desorption of Phenanthrene onto Iron, Copper, and Silicon Dioxide Nanoparticles

The sorption and desorption of phenanthrene by three engineered nanoparticles including nanosize zerovalent iron (NZVI), copper (NZVC), and silicon dioxide (NSiO2) were investigated. The sorption of phenanthrene onto NSiO2 was linear and reversible due to the hydrophilic properties of NSiO2. In comparison, sorption of phenanthrene onto NZVI and NZVC was nonlinear and irreversible, which was potentially due to the existence of significantly heterogeneous surface energy distribution patterns detected by a standard molecular probe technique. Naphthalene exerted significant competitive sorption with phenanthrene for NZVI and NZVC, and the isotherm of phenanthrene changed from being significantly nonlinear to nearly linear when naphthalene was simultaneously absorbed. A surface adsorption mechanism was proposed to explain the observed sorption and competition of phenanthrene on both NZVI and NZVC. In contrast, no competition was observed for sorption onto NSiO2. The sorption of phenanthrene on all three nanoparticles significantly decreased with increasing pH. The sorption irreversibility of phenanthrene on NZVI and NZVC were significantly enhanced with decreasing pH. A pH-dependent hydrophobic effect and dipole interactions between the charged surface (electron acceptors) and phenanthrene with electron-rich pi systems (electron donors) were proposed to explain the observed pH-dependent sorption.

Growth of dense single-walled carbon nanotubes in nano-sized silicon dioxide holes for future microelectronics

Dense and aligned single-walled carbon nanotubes (SWCNTs) were synthesised in nano-sized silicon dioxide holes patterned using electron beam lithography for microelectronics applications. Carbon nanotubes are new materials with potential uses for interconnects and field effect transistors (FETs) of LSI. As single-walled carbon nanotubes have lower resistance than multi-walled carbon nanotubes in close-packed arrangements and show both metallic and semiconducting behaviour, there is a great deal of interest in using dense SWCNTs for low resistive interconnects and high current transistors. Here, we report not only a method for fabrication of SWCNTs in nano-sized holes, but also differences in growth rate and Raman spectroscopy of CNTs in holes of various sizes. The growth rate of CNTs in the holes decreased as the hole size was reduced, due to the amount of carbon radicals diffusing to the catalyst particles at the bottom of the holes.