Showing papers on "Silicon dioxide published in 2012"

How to Prepare Reproducible, Homogeneous, and Hydrolytically Stable Aminosilane-derived Layers on Silica

Abstract: Five functional silanes—3-aminopropyltriethoxysilane (APTES), 3-aminopropyltrimethoxysilane (APTMS), N-(2-aminoethyl)-3-aminopropyltriethoxysilane (AEAPTES), N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTMS), and N-(6-aminohexyl)aminomethyltriethoxysilane (AHAMTES)—were assessed for the preparation of hydrolytically stable amine-functionalized silica substrates. These can be categorized into three groups (G1, G2, and G3) based on the intramolecular coordinating ability of the amine functionality to the silicon center. Silanizations were carried out in anhydrous toluene as well as in the vapor phase at elevated temperatures. Aminosilane-derived layers prepared in solution are multilayers in nature, and those produced in the vapor phase have monolayer characteristics. In general, vapor-phase reactions are much less sensitive to variations in humidity and reagent purity, are more practical than the solution-phase method, and generate more reproducible results. Intramolecular catalysis by the amine fun...

Processing pathway dependence of amorphous silica nanoparticle toxicity: colloidal vs pyrolytic.

Abstract: We have developed structure/toxicity relationships for amorphous silica nanoparticles (NPs) synthesized through low-temperature colloidal (e.g., Stober silica) or high-temperature pyrolysis (e.g., fumed silica) routes. Through combined spectroscopic and physical analyses, we have determined the state of aggregation, hydroxyl concentration, relative proportion of strained and unstrained siloxane rings, and potential to generate hydroxyl radicals for Stober and fumed silica NPs with comparable primary particle sizes (16 nm in diameter). On the basis of erythrocyte hemolytic assays and assessment of the viability and ATP levels in epithelial and macrophage cells, we discovered for fumed silica an important toxicity relationship to postsynthesis thermal annealing or environmental exposure, whereas colloidal silicas were essentially nontoxic under identical treatment conditions. Specifically, we find for fumed silica a positive correlation of toxicity with hydroxyl concentration and its potential to generate r...

An overview of the fundamentals of the chemistry of silica with relevance to biosilicification and technological advances

Abstract: Biomineral formation is widespread in nature, and occurs in bacteria, single-celled protists, plants, invertebrates, and vertebrates. Minerals formed in the biological environment often show unusual physical properties (e.g. strength, degree of hydration) and often have structures that exhibit order on many length scales. Biosilica, found in single-celled organisms through to higher plants and primitive animals (sponges), is formed from an environment that is undersaturated with respect to silicon, and under conditions of approximately neutral pH and relatively low temperatures of 4-40 °C compared to those used industrially. Formation of the mineral may occur intracellularly or extracellularly, and specific biochemical locations for mineral deposition that include lipids, proteins and carbohydrates are known. In most cases, the formation of the mineral phase is linked to cellular processes, an understanding of which could lead to the design of new materials for biomedical, optical and other applications. In this contribution, we describe the aqueous chemistry of silica, from uncondensed monomers through to colloidal particles and 3D structures, that is relevant to the environment from which the biomineral forms. We then describe the chemistry of silica formation from alkoxides such as tetraethoxysilane, as this and other silanes have been used to study the chemistry of silica formation using silicatein, and such precursors are often used in the preparation of silicas for technological applications. The focus of this article is on the methods, experimental and computational, by which the process of silica formation can be studied, with an emphasis on speciation.

Photon-manipulated drug release from a mesoporous nanocontainer controlled by azobenzene-modified nucleic acid.

Abstract: Herein a photon-manipulated mesoporous release system was constructed based on azobenzene-modified nucleic acids. In this system, the azobenzene-incorporated DNA double strands were immobilized at the pore mouth of mesoporous silica nanoparticles. The photoisomerization of azobenzene induced dehybridization/hybridization switch of complementary DNA, causing uncapping/capping of pore gates of mesoporous silica. This nanoplatform permits holding of guest molecules within the nanopores under visible light but releases them when light wavelength turns to the UV range. These DNA/mesoporous silica hybrid nanostructures were exploited as carriers for the cancer cell chemotherapy drug doxorubicin (DOX) due to its stimuli-responsive property as well as good biocompatibility via MTT assay. It is found that the drug release behavior is light-wavelength-sensitive. Switching of the light from visible to the UV range uncapped the pores, causing the release of DOX from the mesoporous silica nanospheres and an obvious cytotoxic effect on cancer cells. We envision that this photocontrolled drug release system could find potential applications in cancer therapy.

Mechanism of cellular uptake of genotoxic silica nanoparticles

Abstract: Mechanisms for cellular uptake of nanoparticles have important implications for nanoparticulate drug delivery and toxicity. We have explored the mechanism of uptake of amorphous silica nanoparticles of 14 nm diameter, which agglomerate in culture medium to hydrodynamic diameters around 500 nm. In HT29, HaCat and A549 cells, cytotoxicity was observed at nanoparticle concentrations ≥ 1 μg/ml, but DNA damage was evident at 0.1 μg/ml and above. Transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy confirmed entry of the silica particles into A549 cells exposed to 10 μg/ml of nanoparticles. The particles were observed in the cytoplasm but not within membrane bound vesicles or in the nucleus. TEM of cells exposed to nanoparticles at 4°C for 30 minutes showed particles enter cells when activity is low, suggesting a passive mode of entry. Plasma lipid membrane models identified physical interactions between the membrane and the silica NPs. Quartz crystal microbalance experiments on tethered bilayer lipid membrane systems show that the nanoparticles strongly bind to lipid membranes, forming an adherent monolayer on the membrane. Leakage assays on large unilamellar vesicles (400 nm diameter) indicate that binding of the silica NPs transiently disrupts the vesicles which rapidly self-seal. We suggest that an adhesive interaction between silica nanoparticles and lipid membranes could cause passive cellular uptake of the particles.

Deposition of silicon dioxide on hydrophobic surfaces

Abstract: Methods for forming silicon dioxide thin films on hydrophobic surfaces are provided For example, in some embodiments, silicon dioxide films are deposited on porous, low-k materials The silicon dioxide films can be deposited using a catalyst and a silanol In some embodiments, an undersaturated dose of one or more of the reactants can be used in forming a pore-sealing layer over a porous material

Adsorption and release of biocides with mesoporous silica nanoparticles

Abstract: In this proof-of-concept study, an agricultural biocide (imidacloprid) was effectively loaded into the mesoporous silica nanoparticles (MSNs) with different pore sizes, morphologies and mesoporous structures for termite control. This resulted in nanoparticles with a large surface area, tunable pore diameter and small particle size, which are ideal carriers for adsorption and controlled release of imidacloprid. The effect of pore size, surface area and mesoporous structure on uptake and release of imidacloprid was systematically studied. It was found that the adsorption amount and release profile of imidacloprid were dependent on the type of mesoporous structure and surface area of particles. Specifically, MCM-48 type mesoporous silica nanoparticles with a three dimensional (3D) open network structure and high surface area displayed the highest adsorption capacity compared to other types of silica nanoparticles. Release of imidacloprid from these nanoparticles was found to be controlled over 48 hours. Finally, in vivo laboratory testing on termite control proved the efficacy of these nanoparticles as delivery carriers for biopesticides. We believe that the present study will contribute to the design of more effective controlled and targeted delivery for other biomolecules.

Comparison of non-crystalline silica nanoparticles in IL-1β release from macrophages

Abstract: Background Respirable crystalline silica (silicon dioxide; SiO2, quartz) particles are known to induce chronic inflammation and lung disease upon long-term inhalation, whereas non-crystalline (amorphous) SiO2 particles in the submicrometre range are regarded as less harmful. Several reports have demonstrated that crystalline, but also non-crystalline silica particles induce IL-1β release from macrophages via the NALP3-inflammasome complex (caspase-1, ASC and NALP3) in the presence of lipopolysaccharide (LPS) from bacteria. Our aim was to study the potential of different non-crystalline SiO2 particles from the nano- to submicro-sized range to activate IL-1β responses in LPS-primed RAW264.7 macrophages and primary rat lung macrophages. The role of the NALP3-inflammasome and up-stream mechanisms was further explored in RAW264.7 cells.

DNA-capped mesoporous silica nanoparticles as an ion-responsive release system to determine the presence of mercury in aqueous solutions

Abstract: We have developed DNA-functionalized silica nanoparticles for the rapid, sensitive, and selective detection of mercuric ion (Hg2+) in aqueous solution. Two DNA strands were designed to cap the pore of dye-trapped silica nanoparticles. In the presence of ppb level Hg2+, the two DNA strands are dehybridized to uncap the pore, releasing the dye cargo with detectable enhancements of fluorescence signal. This method enables rapid (less than 20 min) and sensitive (limit of detection, LOD, 4 ppb) detection, and it was also able to discriminate Hg2+ from twelve other environmentally relevant metal ions. The superior properties of the as-designed DNA-functionalized silica nanoparticles can be attributed to the large loading capacity and highly ordered pore structure of mesoporous silica nanoparticles, as well as the selective binding of thymine-rich DNA with Hg2+ . Our design serves as a new prototype for metal-ion sensing systems, and it also has promising potential for detection of various targets in stimulus-re...

Thermal contact resistance across nanoscale silicon dioxide and silicon interface

Abstract: Silicon dioxide and silicon (SiO2/Si) interface plays a very important role in semiconductor industry. However, at nanoscale, its interfacial thermal properties have not been well understood so far. In this paper, we systematically study the interfacial thermal resistance (Kapitza resistance) of a heterojunction composed of amorphous silicon dioxide and crystalline silicon by using molecular dynamics simulations. Numerical results have shown that Kapitza resistance at SiO2/Si interface depends on the interfacial coupling strength remarkably. In the weak interfacial coupling limit, Kapitza resistance depends on both the detailed interfacial structure and the length of the heterojunction, showing large fluctuation among different samples. In contrast, it is almost insensitive to the detailed interfacial structure or the length of the heterojunction in the strong interfacial coupling limit, giving rise to a nearly constant value around 0.9×10−9m2KW−1 at room temperature. Moreover, the temperature dependent K...

Iron(III)-Doped, Silica Nanoshells: A Biodegradable Form of Silica

Abstract: Silica nanoparticles are being investigated for a number of medical applications; however, their use in vivo has been questioned because of the potential for bioaccumulation. To obviate this problem, silica nanoshells were tested for enhanced biodegradability by doping iron(III) into the nanoshells. Exposure of the doped silica to small molecule chelators and mammalian serum was explored to test whether the removal of iron(III) from the silica nanoshell structure would facilitate its degradation. Iron chelators, such as EDTA, desferrioxamine, and deferiprone, were found to cause the nanoshells to degrade on the removal of iron(III) within several days at 80 °C. When the iron(III)-doped, silica nanoshells were submerged in fetal bovine and human serums at physiological temperature, they also degrade via removal of the iron by serum proteins, such as transferrin, over a period of several weeks.

Inhibitory Effect of Dissolved Silica on H2O2 Decomposition by Iron(III) and Manganese(IV) Oxides: Implications for H2O2-Based In Situ Chemical Oxidation

Abstract: The decomposition of H2O2 on iron minerals can generate •OH, a strong oxidant that can transform a wide range of contaminants. This reaction is critical to In Situ Chemical Oxidation (ISCO) processes used for soil and groundwater remediation, as well as advanced oxidation processes employed in waste treatment systems. The presence of dissolved silica at concentrations comparable to those encountered in natural waters decreases the reactivity of iron minerals toward H2O2, because silica adsorbs onto the surface of iron minerals and alters catalytic sites. At circumneutral pH values, goethite, amorphous iron oxide, hematite, iron-coated sand, and montmorillonite that were pre-equilibrated with 0.05–1.5 mM SiO2 were significantly less reactive toward H2O2 decomposition than their original counterparts, with the H2O2 loss rates inversely proportional to SiO2 concentrations. In the goethite/H2O2 system, the overall •OH yield, defined as the percentage of decomposed H2O2 producing •OH, was almost halved in the ...

Increasing the oral bioavailability of poorly water-soluble carbamazepine using immediate-release pellets supported on SBA-15 mesoporous silica.

Abstract: Background and methods: The aim of this study was to develop an immediate-release pellet formulation with improved drug dissolution and adsorption. Carbamazepine, a poorly water-soluble drug, was adsorbed into mesoporous silica (SBA-15-CBZ) via a wetness impregnation method and then processed by extrusion/spheronization into pellets. Physicochemical characterization of the preparation was carried out by scanning electron microscopy, transmission electron microscopy, nitrogen adsorption, small-angle and wide-angle x-ray diffraction, and differential scanning calorimetry. Flowability and wettability of the drug-loaded silica powder were evaluated by bulk and tapped density and by the angle of repose and contact angle, respectively. The drug-loaded silica powder was formulated into pellets to improve flowability.

Study on the Adsorption Mechanism of DNA with Mesoporous Silica Nanoparticles in Aqueous Solution

Abstract: Among the numerous adsorption strategies for DNA adsorption into mesopores, the salt-solution-induced adsorption method has a great application potential in nucleic acids science; thus, it is important to understand the adsorption mechanism. This work demonstrates the mechanistic aspects underlying the adsorption behaviors of DNA with mesoporous silica nanoparticles (MSNs) in aqueous solution. The driving forces for the adsorption process can be categorized into three parts: the shielded electrostatic force, the dehydration effect, and the intermolecular hydrogen bonds. Compared to the adsorption behaviors of DNA with a solid silica nanosphere, we find some unique features for DNA adsorption into the mesopores, such as increasing the salt concentration or decreasing the pH value can promote DNA adsorption into the mesoporous silica. Further analysis indicates that the entrance of DNA into mesopores is probably controlled by the Debye length in solution and DNA can generate direct and indirect hydrogen bonds in the pores with different diameters. The following desorption study depicts that such types of hydrogen bonds result in different energy barriers for the desorption process. In summary, our study depicts the mechanism of DNA adsorption within mesopores in aqueous solution and sets the stage for formulating MSNs as carriers of nucleic acids.

Electrodeposition of Crystalline and Photoactive Silicon Directly from Silicon Dioxide Nanoparticles in Molten CaCl2

Abstract: Silicon is a widely used semiconductor for electronic and photovoltaic devices because of its earth-abundance, chemical stability, and the tunable electrical properties by doping. Therefore, the production of pure silicon films by simple and inexpensive methods has been the subject of many investigations. The desire for lower-cost silicon-based solar photovoltaic devices has encouraged the quest for solar-grade silicon production through processes alternative to the currently used Czochralski process or other processes. Electrodeposition is one of the least expensive methods for fabricating films of metals and semiconductors. Electrodeposition of silicon has been studied for over 30 years, in various solution media such as molten salts (LiF-KF-K2SiF6 at 745 8C and BaO-SiO2-BaF2 at 1465 8C ), organic solvents (acetonitrile, tetrahydrofuran), and room-temperature ionic liquids. Recently, the direct electrochemical reduction of bulk solid silicon dioxide in a CaCl2 melt was reported. [7] A key factor for silicon electrodeposition is the purity of silicon deposit because Si for the use in photovoltaic devices is solargrade silicon (> 99.9999% or 6N) and its grade is even higher in electronic devices (electronic-grade silicon or 11N). In most cases, the electrodeposited silicon does not meet these requirements without further purification and, to our knowledge, none have been shown to exhibit a photoresponse. In fact, silicon electrodeposition is not as straightforward as metal deposition, since the deposited semiconductor layer is resistive at room temperature, which complicates electron transfer through the deposit. In many cases, for example in room-temperature aprotic solvents, the deposited silicon acts as an insulating layer and prevents a continuous deposition reaction. In some cases, the silicon deposit contains a high level of impurities (> 2%). Moreover, the nucleation and growth of silicon requires a large amount of energy. The deposition is made even more challenging if the Si precursor is SiO2, which is a very resistive material. We reported previously the electrochemical formation of silicon on molybdenum from a CaCl2 molten salt (850 8C) containing a SiO2 nanoparticle (NP with a diameter of 5– 15 nm) suspension by applying a constant reduction current. However this Si film did not show photoactivity. Here we show the electrodeposition of photoactive crystalline silicon directly from SiO2 NPs from CaCl2 molten salt on a silver electrode that shows a clear photoresponse. To the best of our knowledge, this is a first report of the direct electrodeposition of photoactive silicon. The electrochemical reduction and the cyclic voltammetry (CV) of SiO2 were investigated as described previously. [8] In this study, we found that the replacement of the Mo substrate by silver leads to a dramatic change in the properties of the silicon deposit. The silver substrate exhibited essentially the same electrochemical and CV behavior as other metal substrates, that is, a high reduction current for SiO2 at negative potentials of 1.0 V with the development of a new redox couple near 0.65 V vs. a graphite quasireference electrode (QRE) (Figure 1a). Figure 1b shows a change in the reduction current as a function of the reduction potential, and the optical images of silver electrodes before and after the electrolysis, which displays a dark gray-colored deposit after the reduction. Figure 2 shows SEM images of silicon deposits grown potentiostatically ( 1.25 V vs. graphite QRE) on silver. The amount of silicon deposit increased with the deposition time, and the deposit finally covered the whole silver surface (Figure 2). High-magnification images show that the silicon deposit is not a film but rather platelets or clusters of silicon crystals of domain sizes in the range of tens of micrometers. The average height of the platelets was around 25 mm after a 10000 s deposition (Figure 2b), and 45 mm after a 20000s deposition (Figure 2c), respectively. The edges of the silicon crystals were clearly observed. Contrary to other substrates, silver enhanced the crystallization of silicon produced from silicon dioxide reduction and it is known that silver induces the crystallization of amorphous silicon. Energy-dispersive spectrometry (EDS) elemental mapping (images shown in the bottom row of Figure 2) revealed that small silver islands exist on the top of the silicon deposits, which we think is closely related to the growth mechanism of silicon on silver. The EDS spectrum of the silicon deposit (Figure 3a) suggested that the deposited silicon was quite pure and the amounts of other elements such as C, Ca, and Cl were below the detection limit (about 0.1 atom%). Since the oxygen signal was probably from the native oxide formed on exposure of the deposit to air and silicon does not form an alloy with silver, the purity of silicon was estimated to be at least 99.9 atom%. The successful reduction of Si(4+) in silicon dioxide to elemental silicon (Si) was confirmed by Xray photoelectron spectroscopy (XPS) of the silicon deposit [*] Dr. S. K. Cho, Dr. F.-R. F. Fan, Prof. A. J. Bard Center for Electrochemistry, Department of Chemistry and Biochemistry, The University of Texas at Austin Austin, TX 78712 (USA) E-mail: ajbard@mail.utexas.edu

In vitro degradation behavior of silica nanoparticles under physiological conditions.

Abstract: Understanding the degradability of silica nanoparticles is significant for the rational design of desired nanomaterials for various biomedical applications. However, the effect of the intrinsic properties of silica nanoparticles, such as particle shape, surface chemistry, and porosity, on kinetic degradation process under different extrinsic conditions has still received little attention. Herein, mesoporous silica nanoparticles (MSNs) with different aspect ratios (ARs, 1, 2, and 4), the corresponding PEG-functionalized MSNs, and amorphous Stober spherical silica nanoparticles were specially designed and their degradation was evaluated in in vitro simulated physiological media. The results show that shape, surface properties and porosity of nanoparticles, as well as the component of simulated physiological media, play important roles in tuning the degradation kinetics and behaviors. Sphere-shaped MSNs have a faster degradation rate than rod-shaped counterparts. Naked MSNs are eroded from particle external surface, while PEGylated MSNs from interior of particles. And spherical MSNs display more extensive degradation than amorphous silica nanoparticles. The presence of fetal bovine serum (FBS) in Dulbecco's Modified Eagle's Medium (DMEM) can accelerate the degradation process. These results can provide useful guidelines for the rational design of silica nanoparticles for biomedical applications.

Nano-silicon/carbon composite material and preparation method therefor

Abstract: The invention relates to a nano silicon-carbon composite negative pole material for a lithium ion battery and a preparation method thereof. The nano silicon-carbon composite material with carbon-supported nano silicon is formed by taking a porous electrode constituted by silicon dioxide and carbon as a raw material and performing in-situ electrochemical reduction on the silicon dioxide through a fused salt electrolysis method. The materials, namely the silicon and carbon are connected through nano silicon carbide, the connection is of metallurgical grade bonding, and the electrochemical circulation stability of the nano silicon-carbon composite material is further improved. The preparation method of the nano silicon-carbon composite material, provided by the invention, comprises the following steps: compounding a porous block body constituted by the carbon and the silicon dioxide powder with a conductive cathode current collector for being used as a cathode, taking graphite or an inert anode as an anode, placing in a CaCl2 electrolyte or a mixed salt fusant electrolyte containing CaCl2 to constitute an electrolytic bath, applying an electrolysis direct current voltage between the cathode and the anode, controlling the electrolysis voltage, the electrolysis current density and the electrolysis electric quantity, reducing the silicon dioxide in the porous block body to nano silicon by electrolysis, and preparing the nano silicon-carbon composite material for the lithium ion battery in the cathode.

Delamination Propensity of Pharmaceutical Glass Containers by Accelerated Testing with Different Extraction Media

Abstract: The delamination of pharmaceutical glass is a serious issue, as it can cause glass particles to appear in vials, a problem that has forced a number of drug product recalls in recent years. In Type I pharmaceutical glass vials, delamination occurs generally at the bottom and shoulder, where extensive flaming during the conversion process can favor a strong evaporation of alkali and borate species and the formation of heavily enriched silica layers. The contact with parenteral preparations dissolved in an alkaline medium increases the rate of glass corrosion, while the differential hydration of these layers can cause the detachment of flakes. The purpose of this study was to investigate the effect of the pH and the composition of the extraction solutions on the propensity of different glass types to delaminate. Repeated autoclave extractions at 121 °C were carried out on different glass types with different extraction media, including organic extractants like citric and glutaric acid. When vials were in contact with alkaline solutions and similarly aggressive media, an increase in silica extraction values indicated glass corrosion and an increasing risk for further delamination. Under such conditions expansion 33 glass is extensively corroded, showing high silica concentration and heavy flaking as compared to other glass types. Sulfur-treated glass also showed early flaking, even if SiO2 concentration was very low. A similar ranking was observed with extractions carried out with glutaric and citric acids, but at far much higher SiO2 concentration levels. Extractions with 0.9% KCl solution can be used as an accelerated test to highlight the propensity of a glass to delaminate, but in no case it can be taken as a guarantee that the glass will not delaminate when exposed to the pharmaceutical drug, whose extraction ability requires case-by-case study. LAY ABSTRACT: How can injectable drug manufacturers prevent glass delamination? The issue of delamination is a serious one, as it can cause glass particles to appear in vials, a problem that has forced a number of drug product recalls in recent years. To combat this, pharmaceutical and biopharmaceutical manufacturers need to understand the reasons for glass delamination. The most recent cases of product recall due to the presence of particles in the filling liquid have involved borosilicate glass containers carrying drugs made of active components with known ability to corrode glass and to dissolve the silica matrix. Sometimes these ingredients are dissolved in an alkaline medium that dramatically increases the glass corrosion and potentially causes the issue. As this action is strongly affected by time and temperature, flaking may become visible only after a long incubation during storage and requires systematic monitoring to be detected at its early stage. If the nature of the filling liquid is the driving force of the phenomenon, other factors are of primary importance. The surface morphology created during vial forming is a key issue, being a function of the forming temperature that is higher in the cutting step and the forming of the bottom. Delamination occurs generally on the vial9s bottom and shoulder, where extensive flaming can favor a strong evaporation of alkali and borate species and the formation of heavily enriched silica layers. When these layers are in contact with a solution, they are subject to a differential re-hydration that may result in cracking and detachment of scales. The purpose of this investigation is to identify testing conditions and parameters that can be used as indicators of an incipient delamination process. Extractions with 0.9% KCl solution for 1 h at 121 °C can be used to simulate a long-term contact with aggressive pharmaceutical preparations, while SiO2 concentration in the extract solution can be taken as an index of glass dissolution. The conclusions developed by this study can provide pharmaceutical manufacturers with information needed to help prevent glass delamination in their processes.

Hierarchically Structured Metal Oxide/Silica Nanofibers by Colloid Electrospinning

Abstract: We present herein a new concept for the preparation of nanofibrous metal oxides based on the simultaneous electrospinning of metal oxide precursors and silica nanoparticles. Precursor fibers are prepared by electrospinning silica nanoparticles (20 nm in diameter) dispersed in an aqueous solution of poly(acrylic acid) and metal salts. Upon calcination in air, the poly(acrylic acid) matrix is removed, the silica nanoparticles are cemented, and nanocrystalline metal oxide particles of 4-14 nm are nucleated at the surface of the silica nanoparticles. The obtained continuous silica fibers act as a structural framework for metal oxide nanoparticles and show improved mechanical integrity compared to the neat metal oxide fibers. The hierarchically nanostructured materials are promising for catalysis applications, as demonstrated by the successful degradation of a model dye in the presence of the fibers.

Porous silicon based anode material formed using metal reduction

Abstract: A porous silicon based material comprising porous crystalline elemental silicon formed by reducing silicon dioxide with a reducing metal in a heating process followed by acid etching is used to construct negative electrode used in lithium ion batteries. Gradual temperature heating ramp(s) with optional temperature steps can be used to perform the heating process. The porous silicon formed has a high surface area from about 10 m2/g to about 200 m2/g and is substantially free of carbon. The negative electrode formed can have a discharge specific capacity of at least 1800mAh/g at rate of C/3 discharged from 1.5V to 0.005V against lithium with in some embodiments loading levels ranging from about 1.4 mg/cm2 to about 3.5 mg/cm2. In some embodiments, the porous silicon can be coated with a carbon coating or blended with carbon nanofibers or other conductive carbon material.

Controlling Nanostructures of Mesoporous Silica Fibers by Supramolecular Assembly of Genetically Modifiable Bacteriophages

Abstract: A useful virus: The synthesis of a new family of mesoporous silica fibers is reported. Monodisperse filamentous bacteriophages self-assembled into highly ordered hexagonal lattices that were used as templates for the formation of silica nanostructures. Removal of the bacteriophage assembly through calcination led to the formation of mesoporous silica fibers with pore structures precisely defined by the bacteriophage assembly (see picture).

Synthesis of Monodisperse, Hierarchically Mesoporous, Silica Microspheres Embedded with Magnetic Nanoparticles

Abstract: We report a preparation method for the synthesis of monodisperse magnetic polymer/silica hybrid microspheres using polymer microspheres incorporated with magnetic nanoparticles as a novel template. Monodisperse, hierarchically mesoporous, silica microspheres embedded with magnetic nanoparticles were successfully fabricated after the calcination of the hybrid microspheres. The magnetic nanoparticles were encapsulated in silica and distributed over the whole area of the porous microspheres without leakage. The resulting inorganic materials possess highly useful properties such as high magnetic nanoparticle loading, high surface area, and large pore volumes. The hierarchically mesoporous magnetic silica microspheres resulted in a high bovine serum albumin (BSA) protein adsorption capacity (260 mg/g) and a fast adsorption rate (reaching equilibrium with 8 h).

One-pot synthesis of spheres-on-sphere silica particles from a single precursor for fast HPLC with low back pressure.

Abstract: Spheres-on-sphere (SOS) silica particles are prepared in a one-pot scalable synthesis from mercaptopropyltrimethoxysilane with hydrophilic polymer and cationic surfactant under alkaline conditions. The SOS particles exhibit solid-core porous-shell properties. The fast separation of small molecules and proteins with low back pressure are demonstrated by high-performance liquid chromatography (HPLC) for the columns packed with SOS-particles.

Effects of composition and thermal annealing on the mechanical properties of silicon oxycarbide films

Abstract: There is an increasing trend to incorporate silicon carbide (SiC) into silicon oxides to improve the mechanical properties, thermal stability, and chemical resistance. In this work the silicon oxycarbide (SiOC) films were deposited by RF magnetron co-sputtering from silicon dioxide and silicon carbide targets. Subsequently rapid thermal annealing was applied to the as-deposited films to tune the mechanical properties. Energy dispersive spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and ellipsometry were employed to characterize the compositions and microstructure of the films. The residual stress of the films was calculated from the film–substrate curvature measurement using Stoney's equation. The film stress changed from compressive to tensile after annealing, and it generally increased with carbon contents. The Young's modulus and hardness were investigated by the depth-sensing nanoindentation, which were found to increase with the carbon content and annealing temperature. A thorough microstructural analysis was conducted to investigate the effect of carbon content and annealing temperature on the mechanical properties of SiOC films.

Method for manufacturing silicon photoelectric diode

Abstract: The invention provides a method for manufacturing a silicon photoelectric diode, which belongs to the field of manufacturing semiconductor devices. The invention particularly relates to the method for manufacturing the silicon photoelectric diode. The method comprises the following steps of: adopting an insulator upper silicon wafer as a substrate, wherein the insulator upper silicon wafer comprises a support silicon chip, a silicon dioxide buried layer and a device layer; processing an isolated groove of a closed ring first on the device layer by adopting a dry etching process; growing a silicon dioxide layer with a certain thickness on the upper surface of the device layer of the insulator upper silicon wafer; performing ion implantation doping on the device layer by penetrating the silicon dioxide layer to obtain a P type doped region and an N type doped region; and growing a titanium metal layer and an aluminum metal layer with certain thicknesses on the upper surface of the device layer successively by adopting a sputtering method, and performing photoetching to form a positive electrode and a negative electrode to finally obtain a silicon photoelectric diode structure. The method for manufacturing the silicon photoelectric diode has the advantages of simple process, high reliability, good repeatability and stability, and can be integrated with other devices.