Types Of Silica Research Articles

Evaluation of the cellular effects of silica particles used for dermal application

ABSTRACT The cellular effects of 5 types of spherical amorphous silica particles whose particle size were 4.2–12.8 μm for cosmetic use and two types of crystalline silica whose particle size were 2.4 and 7.1 μm particles for industrial use were examined. These silica particles were applied to HaCaT human keratinocytes for 24 hr. Crystalline silica enhanced IL-8 and IL-6 expression and caused cell membrane damage. Crystalline silica also enhanced HO-1 gene expression; however, the level of intracellular ROS did not change. Compared with crystalline silica, the cellular effects of the spherical silica employed in this study were minor. Cellular uptake of particles was observed for all of silica particle types. Cellular uptake of crystalline silica was observed 1 hr after exposure, and internalized silica particles were present in the cytoplasm. When HaCaT cells were exposed to crystalline silica for 1 hr and incubated for 23 hr in culture medium without silica particles, IL-8 expression was still detected. In addition, silica particles exerted negligible effects using a 3D skin tissue model. Thus, the following conclusions may be drawn. (1) cellular effects exerted by spherical silica are less compared to crystalline silica. (2) phagocytosis of particles is an important first step in the cellular effects of silica particles. (3) spherical silica particles might exert little, if any, effect on healthy skin attributed to no apparent cellular uptake.

In Ukrainian

Aromatic organic acids are among the common environmental pollutants that enter the water with washouts from agricultural lands, wastewater from chemical and pharmaceutical industries. Taking into account the high toxicity of aromatic substances, the important task of water purification is the removal of their trace amounts. This problem can be solved by using chemically modified inorganic materials, such as silicas, which have high mechanical, chemical, hydrolytic, and radiation stability. Therefore, they do not lose their sorption capacity during long-term use and do not pollute water with sorbent degradation products. The purpose of this work is the synthesis of a sorption-active material for removal of toxic aromatic acids by chemical immobilization of β-cyclodextrin functional groups on an aerosilogel (highly dispersed type of amorphous silica). A β-cyclodextrin-containing aerosilogel was synthesized by two-stage liquid-phase chemical modification of hydroxylated silica surface. Using the methods of IR spectroscopy, spectrophotometry, thermogravimetry, pH metry, low-temperature adsorption-desorption of nitrogen, chemical and elemental analysis of the surface, the surface structure and its quantitative chemical composition, and also parameters of porous structure of initial and chemically modified aerosilogels were determined. Sorption of benzoic, salicylic and β-resorcylic acids on aerosilogels from aqueous buffer solutions with pH=1 was studied. The insignificant contribution of silanol and aminopropyl groups and complete participation of chemically fixed β-cyclodextrin in the sorption of aromatic acids were proved. The results obtained are analyzed using kinetic models for pseudo-first and pseudo-second order processes, as well as Langmuir and Freundlich models for equilibrium adsorption on homogeneous and heterogeneous surfaces. It has been found that the sorption kinetic processes are well described by a pseudo-first order equation (in the presence of one type of functional groups on the surface) and a pseudo-second order equation for bi- and trifunctional aerosilogels. Experimental results on the equilibrium sorption of aromatic acids on β-cyclodextrin-containing aerosilogel are in good agreement with the Langmuir adsorption equation. This is evidence of decisive contribution of grafted oligosaccharide groups to the sorption of organic acids. The proposed chemical approach to increasing the sorption activity of aerosilogel can be used to obtain specific chromatographic carriers, as well as inorganic sorbents for the effective removal of small amounts of highly toxic organic substances from water and aqueous solutions.

Photodegradation of acetaminophen and ibuprofen in iron supported in SBA-15 under UV irradiation

In this research, the photodegradation of Acetaminophen and (RS)-2-(4-isobutylphenyl)propanoic acid was evaluated by the heterogeneous photo-Fenton process using solid catalysts of iron nitrate (Fe(NO3)3) supported on mesoporous silica type SBA-15 under UV irradiation. This study began with the synthesis of the SBA-15 support and then by the preparation of the iron salt catalysts by means of the impregnation method at incipient volume and subsequently they were calcined. Afterwards, its chemical characterization, chemical composition, specific surface area and morphology were carried out by Scanning Electron Microscopy, and Scanning Transmission Electron Microscopy, Energy Dispersive Spectroscopy, Atomic Absorption Spectroscopy, X-ray Photoelectron Spectroscopy, Transmission Electron Microscopy, this result confirms the presence of iron incorporated in the support, low-angle X-ray diffractograms are observed to show a diffraction peak (100), which indicates that the material has a structure mesoporous similar to SBA-15, the textural characterization will be obtained from the adsorption–desorption isotherms of N2 at −196.15 °C, Infrared Spectroscopy with Fourier transform, Spectroscopy Ultraviolet Visible by Diffuse Reflectance it is observed that the samples of 2FeSBA-15 and 5FeSBA-15 present higher percentages of isolated species of Fe3+ and the photocatalytic study, determination of nitrates, it is observed that the 5FeSBA-15 catalyst in the presence of H2O2 was the best for drugs degradation, being 99 % for Acetaminophen and Ibuprofen at 60 and 40 min of reaction respectively. The study of radical inhibitors was carried out, observing that hydroxyl radicals are the most active species in the degradation of both drugs, variations were made in the effect of Fe loading, initial concentration, amount of catalyst, temperature, pH, amount of H2O2, in order to obtain the best reaction conditions, a number of five cycles were carried out with each of the drugs. This project will be possible research in the development of topics directed towards water treatment.

Cadmium and lead ions adsorption on magnetite, silica, alumina, and cellulosic materials

The adsorption of small particles on the surface of an adsorbent depends on interfacial dynamics and associated parameters, including the adsorbate reactivity, adsorbent surface activity, and matrix porosity and tortuosity. Herein, the effect of the surfaces of magnetite, silica/alumina, and silica-cellulose matrix on cadmium adsorption is termed using spectroscopic methods. Atomic absorption spectroscopy was used to determine the adsorption of metal ions in the solid–liquid interfaces by the batch method with different pH, metal concentrations, and contact times. Cadmium (II) were well adsorbed on the magnetite-inorganic surface (around 90% adsorption) rather than other types of semi-organic surfaces, silica, silica-alumina and other cellulosic materials (less than 60% adsorption for Cadmium (II) and 80% of Lead (II) ions). The presence of lead (II) changed the cadmium adsorption behaviour, indicating that adsorption–desorption was a physical interaction on different surfaces. Most absorptions are pH-dependent, stable for Cadmium ions and vary for Lead ions. Moreover, the adsorption analysis using Langmuir and Freundlich isotherms showed no significant characteristics of chemical interaction of the ions with the surfaces as indicated by low R2 values (both around 0.5) for magnetite materials higher for cellulose materials of Langmuir and Freundlich isotherms. This study is beneficial for various fields, such as material science and environmental chemistry, which will play an essential role in the future.

Theoretical analysis of thermal annealing kinetics of radiation defects in silica

The literature data on the annealing kinetics of the basic radiation defects in different types of silica after gamma- and neutron irradiation were analyzed in terms of diffusion-controlled reactions. The defect migration energies and relevant pre-factors are determined. It is shown that the annealing kinetics in several gamma and neutron irradiated samples could be explained as the recombination of the E′ centers (an oxygen vacancy) with two mobile hole defects, similarly to our recent observation in neutron irradiated sapphire. The mechanism of the relevant processes and a role of OH content are discussed.

Tuning the size and concentration of functional molecules coated onto mesoporous silica nanoparticles for efficient therapeutic protein delivery

In this work, the importance of the size and concentration of binding sites in mesoporous nanostructures on their performance for protein delivery is reported. Various types of carboxyl-functionalized mesoporous silica (MS) nanoparticles, i.e., SA(x)-MS, PA1(x)-MS and PA2(x)-MS, where x = 5, 10, 15, 20 and 30 mg, were synthesized by using succinic anhydride (SA) and polyacrylic acid with two molecular weights (i.e., 1800 (PA1) and 100,000 (PA2)), respectively. The particles were thoroughly characterized by TGA, FTIR, STEM and zeta potential measurement techniques and then, their biomedical performance was investigated by using a model therapeutic protein, lysozyme. The carboxyl functional molecules concentration (CCOOH) on the particles was increased as a function of the functional molecules type and quantity in the synthesis reaction environment. The maximum CCOOH values were recorded for SA(10)-MS, PA1(15)-MS and PA2(15)-MS, being 827, 1662 and 2137 µmol.g−1, respectively. However, SA(10)-MS, PA1(15)-MS and PA2(10)-MS particles led to the highest lysozyme loading yield values of 63.1%, 90.0% and 71.5% as well as the loading capacities of 631, 900 and 715 mg.g−1, respectively. The controlled lysozyme release rate and some protein conformational changes favored the in vitro antibacterial activity of lysozyme molecules carried by the particles, which followed the order of PA1(15)-MS > PA2(10)-MS > SA(10)-MS.

Effect and mechanism of two different types of waterproof admixtures and silica fume on the hydration and mechanical properties of natural hydraulic lime

In this study, the effect and mechanism of two different types of waterproof admixtures, silica fume and their composite usage on the hydration and mechanical properties of natural hydraulic lime were evaluated. Specifically, X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and scanning electron microscopy were utilized to investigate the phase composition, micromorphology, and chemical state in-depth. The results showed that, combination of two waterproof admixtures with cementitious matrix via forming Si-O-Si bond and calcium-containing compound weakened the contact between water and cementitious matrix, leading to retardation of hydration. However, silane impregnant more or less promoted formation of hydrated product thanks to the reaction between polycondensated silane and Ca(OH)2, and improved mechanical strength of natural hydraulic lime-based mortars. Hydration and carbonation of natural hydraulic lime was inhibited by bulk modification with silicone-acrylic latex. Partial substitution of natural hydraulic lime by silica fume promoted the hydration and hardening process of cementitious system, leading to improvement of mechanical strength. What is more important, composite modification compensated strength weakening which was the common shortcoming caused by bulk modification of cementitious system with waterproof admixtures.

Reactive Compatibilization of Impact Copolymer Polypropylene and Organically Modified Mesoporous Silica to Prepare Composites Possessing Enhanced Mechanical Properties

Mesoporous silica was evaluated as functionalized filler in impact copolymer polypropylene (ICP) in its original form as well as after organic modification. Mesoporous silica was synthesized by base-catalyzed hydrolysis of tetraethyl orthosilicate in the water–acetone medium. The organic modification of mesoporous silica was carried out using commercially available silane with a terminal unsaturated bond and by synthesizing silane precursor by chemical treatment via TEMPO-initiated thiol–ene chemistry to introduce alkyl chains terminating in hydroxyl groups. The characterization for all types of mesoporous silica prepared was done using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), solid-state nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) analysis, X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM). ICP–mesoporous silica composites were prepared using 1, 5, and 10 phr mesoporous silica and organically modified mesoporous silica loading via reactive compatibilization and were tested for their thermal, morphological, rheological, and mechanical properties. The addition of mesoporous and organically modified mesoporous silica enhanced thermal stability and nucleation with respect to neat ICP. Tensile and flexural moduli were improved while maintaining their impact strength. Analysis of rheological properties revealed a rise in zero-shear rate viscosity in ICP–mesoporous silica composites. DMA studies showed higher storage and loss modulus with the addition of mesoporous silica in ICP.

Combined effect of nano-silica and silica fume to improve concrete workability and compressive strength: a case study and an overview of the literature.

Several types of amorphous silica generate pozzolanic reactions at micro- and nano-scale, which can improve concrete macro-structural characteristic. However, their addition can raise the viscosity of the mixture, thus decreasing its workability. In the present work is proposed an experimental setup to determine concrete compression and manageability performance adding Silica Fume (SF), 0.0, 6.5, 8.5, 10.0% w/b, colloidal silica (nSi), 0.0, 0.5, 1.0, 1.5, 2.0, 2.5% w/b and SF-nSi combined, 0.0-0.0, 0.2-8.5, 0.2-10% w/b, and an extensive overview of the literature for concrete mixtures with SF, nSi and SF-nSi combined. The results show that the addition of SF can increase compressive strength by 12%, nevertheless, can also lead to decreases in manageability of the sample (e.g., a decrease by 67% for a dosage of 10.0% w/b). On the other hand, nSi can increase compressive strength by up to 25% with a dosage of 2.5% and can increase the manageability by 78% for dosages greater than 0.5% w/b. When combining the two materials, an increase in compressive strength was observed, along with a loss of workability. A statistical analysis of the data found in literature is proposed, highlighting interesting trends of behavior between SF and nSi with workability and compressive strength, as well as a lack of research for slump outcomes and for the effects of combined additives in concrete.

On the dissolution of sponge silica: Assessing variability and biogeochemical implications

The dissolution of the biogenic silica that constitutes the skeletons of silicifying organisms is an important mechanism for regenerating dissolved silicon in the ocean. The silica skeletons deposited to the seafloor after the organisms die keep dissolving until becoming definitively buried. The low dissolution rate of sponge skeletons compared to that of diatom skeletons favors their burial and makes sponges (Phylum Porifera) to function as important silicon sinks in the oceans. However, it remains poorly understood whether the large variety of siliceous skeletons existing in the Porifera involves similar variability in their dissolution rates, which would affect the general conceptualization of these organisms as silicon sinks. Herein we investigated kinetics of silica dissolution for major types of skeletons in the three siliceous lineages of Porifera, following standardized digestion conditions in 1% sodium carbonate with orbital agitation at 85°C. The results are compared with those of a previous study conducted under identical conditions, which considered diatom silica, sponge silica, and lithogenic silica. Unexpectedly, the silica of homoscleromorph sponges dissolved only a bit slower than that of freshly cultured diatoms and as fast as diatom earth. However, the rest of sponge skeletons were far more resistant, although with some differences: the isolated spicules of hexactinellid sponges dissolved slightly faster than when forming frameworks of fused spicules, being hexactinellid frameworks as resistant to dissolution as the silica of demosponges, irrespective of occurring in the form of isolated spicules or frameworks. The experiments also indicated that the complexation of sponge silica with aluminum and with chitin does not increase its resistance to dissolution. Because the rapidly-dissolving homoscleromorph sponges represent less than 1% of extant sponges, the sponge skeletons are still conceptualized as important silicon sinks due to their comparative resistance to dissolution. Yet, the turnover of silica into dissolved silicon will always be faster in environments dominated by hexactinellids with isolated spicules than in environments dominated by other hexactinellids and/or demosponges. We discuss whether the time required for a given silica type to completely dissolve in 1% sodium carbonate could be a predictor of its preservation ratio in marine sediments.

Hydrogen gas permeation in peroxide‐crosslinked ethylene propylene diene monomer polymer composites with carbon black and silica fillers

AbstractThis study investigated the effect of two types of fillers, carbon black (CB) and silica, on the H2 permeation of peroxide‐crosslinked ethylene propylene diene monomer (EPDM) polymers at different pressures (1.2–9.0 MPa). The H2 uptake was linearly correlated with the exposure pressure in all specimens. The H2 solubility in the filled EPDM composites also increased linearly with an increase in the filler content. The H2 solubility was determined by the absorption of polymer networks and adsorption at the filler surface in the CB‐filled EPDM. Meanwhile, the H2 solubility in neat and silica‐filled EPDM was dominated by the polymer network absorption. In the filled EPDM, H2 diffusivity decreased because the filler increased the tortuosity of the polymer. The effects of filler on H2 permeation were largest in the high‐abrasion and semi‐reinforcing furnaces, while the effects were lowest in the silica filler. This trend was associated with the surface area and interface of the fillers. The correlations of the average diffusivity (or permeability) with the filler content and crosslink density of the composites were observed and discussed. From the resulting relationships, we can predict the H2 permeation properties of the compounded EPDM candidates, when used as seal materials, under high‐pressure environment in H2‐refueling stations.

New Mesoporous Silica Materials Loaded with Polyphenols: Caffeic Acid, Ferulic Acid and p-Coumaric Acid as Dietary Supplements for Oral Administration.

In this study, two types of mesoporous silica with different pore structures and volumes were synthesized by the soft-templating method. The two types of mesoporous silica, type MCM-41 and MCM-48, were loaded with three polyphenols-caffeic acid, p-coumaric acid and trans-ferulic acid-in the same ratio of mesoporous silica:polyphenol (1:0.4 w/w). The materials obtained were characterized from a morphological and structural point of view through different analysis techniques. Through X-ray diffraction (XRD), the crystallization plane and the ordered structure of the mesoporous silica were observed. The difference between the two types of materials containing MCM-41 and MCM-48 was observed through the different morphologies of the silica particles through scanning electron microscopy (SEM) and also through the Brunauer-Emmet-Teller (BET) analysis, that the surface areas and volumes of pores was different between the two types of mesoporous silica, and, after loading with polyphenols, the values were reduced. The characteristic bands of silica and of polyphenols were easily observed by Fourier-transform infrared spectroscopy (FTIR), and, through thermogravimetric analysis (TGA), the residual mass was determined and the estimated amount of polyphenol in the materials and the efficient loading of mesoporous silica with polyphenols could be determined. The in vitro study was performed in two types of simulated biological fluids with different pH-simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). The obtained materials could be used in various biomedical applications as systems with controlled release of natural polyphenols and the most suitable application could be as food supplements especially when a mixture of such materials is used or when the polyphenols are co-loaded within the mesoporous silica.

Flexible photonics in low stiffness doped silica for use in fibre reinforced polymer composite materials

The production of a flexible photonic device in doped silica with a Young's modulus that is significantly less than that of traditional silica glass is described. Here the purpose of reducing the modulus is to make planar sensors more applicable for integration into fibre reinforced polymer composite structures. The flexible planar substrate (58 μm thick) consists of three doped silica layers, fabricated using sacrificial silicon wafer processing. It is demonstrated that a Young's modulus of around 40 GPa can be achieved in comparison to a value above 70 GPa for typical silica glass. The optical response of a few mode waveguide that is direct UV written within the central core layer of the flexible glass platform is described. The mechanical stiffness of the platform is determined using nano-indentation tests and confirmed in mechanical tests that demonstrate clearly the flexible nature of the platform. To assess usability for applications integrated into structures undergoing mechanical loading the fatigue lifetime for one million bending cycles is investigated. No degradation to the optical response was observed under the performed testing.

CO2-assisted fabrication of silica gel adsorbent in honeycomb rotary wheels for air dehumidification.

A honeycomb rotary wheel fabricated from sheet adsorbent of silica gel is a competitive drying facility for air dehumidification in modern drying and air conditioning industries due to its large contacting area (3,000 m2/m3) and the rapid diffusion of the adsorbate compared to silica gel pellets. The delicate preparation procedure of hygroscopic silica gel is paramount for improved adsorption capacity by optimizing the surface area, pore size, and pore volume of silica gel. In this article, silica gel adsorbent in a honeycomb rotary wheel was fabricated by neutralizing the impregnated water glass solution with a modulus of 3.3 on the glass fiber sheet of the honeycomb matrix using CO2 at different pressure at room temperature instead of corrosive acids. The as-obtained silica gel absorbent was characterized by XRD, scanning electron microscopy (SEM), specific surface area and pore size analysis, and dynamic vapor/gas sorption analysis. The results showed that the as-obtained silica gel adsorbent is uniform in size and tunable in terms of specific surface area, pore size, pore volume, and adsorption capacity by CO2 pressure. The typical silica gel fabricated by CO2 of 0.25 MPa with a specific surface area of 764.86 m2/g, an average micropore size with a diameter of 2.94 nm, and a pore volume of 0.45 ml/g delivers a saturated adsorption capacity of as high as 287.24 mg/g at RH 50%, which is the best in adsorption performance compared to the previously reported results. This provides a new strategy for environment-friendly manufacturing of silica gel adsorbent in honeycomb rotary wheels for air dehumidification.

Authigenic silica in continental lacustrine shale and its hydrocarbon significance

Taking lake basin shales of the Triassic Yanchang Formation in the Ordos Basin, NW China and the Cretaceous Qingshankou Formation in the Songliao Basin, NE China as research objects, the characteristics and origins of different types of silica in the shales have been studied by means of core observation, thin section identification, cathodoluminescence, X-ray diffraction analysis, scanning electron microscope (SEM), electron probe and rock pyrolysis. The results shows that the origins of silica include felsic mineral dissolution, tuffite devitrification, clay mineral transformation and siliceous mineral metasomatism. The silica formed by feldspar dissolution commonly appears as spots and veins, with low degree of crystallization, and is largely aqueous opal mineral, with an average SiO2 content of 67.2%. Silica formed by devitrification of tuffite mainly occurs in two forms, amorphous silica and authigenic quartz with better crystal shape. The authigenic silica formed during the transformation of clay minerals is embedded in the clay minerals in the form of micron-scale plates and small flakes, or mixed with clay minerals in a dispersed state. The authigenic quartz formed by siliceous mineral metasomatism is in better angular crystal shape, and has an average SiO2 content of 87%. The authigenic siliceous mineral content is positively correlated with the content of terrigenous felsic minerals. The pressure solution of felsic minerals is the main source of authigenic siliceous minerals, followed by the transformation of clay minerals, and the organic matter has some boost on the formation of authigenic silica. The authigenic siliceous materials of different origins have different geological characteristics and occurrence states from terrigenous quartz, which would affect the storage performance, seepage capacity and fracturing effect of continental shale. Although the organic-rich shale has high silica content, different from terrigenous quartz, authigenic silica in this kind of shale mostly floats and disperse in clay minerals, which would have negative effect on the formation of complex fractures in fracturing, fracture support ability after fracturing, and formation of effective seepage channels. Calculating the brittleness index of shale intervals only based on the composition of brittle minerals cannot accurately characterize mechanical characteristics of continental shale oil reservoirs, and would affect comprehensive evaluation and selection of continental shale oil “sweet spots”.

Heterogeneous Percolation in Poly(methylvinylsiloxane)/Silica Nanocomposites: The Role of Polymer–Particle Interaction

Agglomeration and linking of nanoparticles or aggregates lead to the formation of percolated particle networks and alter the mechanical enhancement in polymer nanocomposites. Although critical behaviors have been widely studied, the solidlike behavior is only well described under the condition of the uniform dispersion of nanoparticles. In this work, we illustrate the role of particle–polymer interaction in the uniformity of particle dispersion and mechanical enhancement. Two types of silica with different interfacial adhesion energies with poly(methylvinylsiloxane) were adopted, resulting in different uniformities of particle dispersion. The critical percolation concentrations from the yield shear stress and yield first normal stress difference are identical. A lower interfacial adhesion energy leads to a higher critical concentration. The preshear stress only affects the critical concentration but does not change the critical exponents, which rely on the particle–polymer interaction. The mechanical enhancement, expressed as the power-law dependence of the yield stresses on the filler content, exhibits extraordinarily large power-law exponents for nanocomposites with lower interfacial adhesion energy, seriously deviating from the theoretical prediction in homogeneous dispersion systems. Based on the structural information from small-angle X-ray scattering (SAXS)/ultrasmall-angle X-ray scattering (USAXS) and transmission electron microscopy (TEM), we propose a model describing the heterogeneous percolation of loose aggregates in the presence of compact aggregates. This model shows that the heterogeneity of aggregates, including the fraction of compact aggregates and their fractal dimension, is the key factor in the scaling relationship between the yield stress and the particle volume fraction.

Insights into the microbial life in silica-rich subterranean environments: microbial communities and ecological interactions in an orthoquartzite cave (Imawarì Yeuta, Auyan Tepui, Venezuela).

Microbial communities inhabiting caves in quartz-rich rocks are still underexplored, despite their possible role in the silica cycle. The world’s longest orthoquartzite cave, Imawarì Yeuta, represents a perfect arena for the investigation of the interactions between microorganisms and silica in non-thermal environments due to the presence of extraordinary amounts of amorphous silica speleothems of different kinds. In this work, the microbial diversity of Imawarì Yeuta was dissected by analyzing nineteen samples collected from different locations representative of different silica amorphization phases and types of samples. Specifically, we investigated the major ecological patterns in cave biodiversity, specific taxa enrichment, and the main ecological clusters through co-occurrence network analysis. Water content greatly contributed to the microbial communities’ composition and structures in the cave leading to the sample clustering into three groups DRY, WET, and WATER. Each of these groups was enriched in members of Actinobacteriota, Acidobacteriota, and Gammaproteobacteria, respectively. Alpha diversity analysis showed the highest value of diversity and richness for the WET samples, while the DRY group had the lowest. This was accompanied by the presence of correlation patterns including either orders belonging to various phyla from WET samples or orders belonging to the Actinobacteriota and Firmicutes phyla from DRY group samples. The phylogenetic analysis of the dominant species in WET and DRY samples showed that Acidobacteriota and Actinobacteriota strains were affiliated with uncultured bacteria retrieved from various oligotrophic and silica/quartz-rich environments, not only associated with subterranean sites. Our results suggest that the water content greatly contributes to shaping the microbial diversity within a subterranean quartzite environment. Further, the phylogenetic affiliation between Imawarì Yeuta dominant microbes and reference strains retrieved from both surface and subsurface silica- and/or CO2/CO-rich environments, underlines the selective pressure applied by quartz as rock substrate. Oligotrophy probably in association with the geochemistry of silica/quartz low pH buffering activity and alternative energy sources led to the colonization of specific silica-associated microorganisms. This study provides clues for a better comprehension of the poorly known microbial life in subsurface and surface quartz-dominated environments.

Effect of black sand nanoparticles on physical-mechanical properties of butyl rubber compounds

A novel type of silica namely black sand (BS) with silane coupling agent was chosen as reinforcing filler in butyl rubber (IIR). BS was obtained from the beach area of Rosetta in Egypt. The filler was characterized by Fourier-transform infrared (FTIR), X-ray diffraction (XRD), and transmission electron microscope (TEM). The XRD analysis showed that BS is composed mainly of Albite (Sodium Aluminium Silicate) up to 64% approximately. Novel nanocomposites were prepared via a two-roll mill by incorporating different concentrations of BS nanoparticles (5,10, 15, 20,30 and 40 phr) in IIR. The effects of filler loading on shape factor, curing characteristics, and mechanical and dynamic properties of IIR vulcanizates were investigated. The modulus of IIR vulcanizates was used to predict the shape factor of BS aggregation in the polymer. The data indicated that cure time decreased with the increase in filler loading, and the change in scorch time is less. It was found that the shape factor is independent of the concentration. With an increase in the filler loading, tensile and elongation of the composites were significantly increased, especially at 30 phr. The bound rubber content increased with increasing BS content up to 30 phr exhibiting the rubber-filler interaction. The reinforcing factor, R (related to the difference in tan δ peak height at the glass transition temperature (Tg) for the filled and unfilled rubbers), also demonstrated that the BS-IIR interaction was stronger than for unfilled rubber. Since 30 phr black sand loaded IIR composite showed superior physical-mechanical properties. In general, the results indicated that the black sand filler was an effective reinforcement material for the butyl rubber.

Tribromide immobilized on surface of magnetic nanoparticles modified tris(triazine-triamine): A versatile and highly active catalyst for oxidation of sulfides and oxidative coupling of thiols

In this article, we show that tribromide heterogenized on the surface of silica-coated magnetic nanoparticles modified with N2,N4,N6-tris(aminomethyl)-1,3,5-triazine-2,4,6-triamine [Fe3O4@SiO2-tris(triazine-triamine)-Br3] is a novel and efficient reusable nanocatalyst for the oxidation of sulfides to sulfoxides and oxidative coupling of thiols to disulfides using hydrogen peroxide as green oxidant. The structure of the as-fabricated Fe3O4@SiO2-tris(triazine-triamine)-Br3 was characterized by a series of spectroscopic techniques including FT-IR spectroscopy, SEM, TEM, EDX, VSM, XRD and TGA techniques. TEM and SEM analysis confirmed that the typical silica shell thickness was assessed to be around 20 nm. Recycling studies revealed that the Fe3O4@SiO2-tris(triazine-triamine)-Br3 could be easily recovered by a simple magnetic separation and recycled at least 6 times without deterioration in catalytic activity.

A comparative study on the modulatory role of mesoporous silica nanoparticles MCM 41 and MCM 48 on growth and metabolism of dicot Vigna radiata

With the advent of nanoscience, nanotechnology and their applications in various fields, mesoporous silica nanoparticles have gained popularity due to their stability, biocompatibility, unique honeycomb-like structures - ordered and random by nature, large surface to volume ratio, porosity, active surfaces, high loading capacity, ease of interactions with solvent, solute and suspended particles. These multitudes of intrinsic properties have motivated us towards an interdisciplinary detailed study on applications of mesoporous silica with an intention in increasing efficacy of productivity, growth if any, in plant life. This study aims at finding modus operandi of the structural uniqueness and eccentricity of various types of mesoporous silica in maneuvering their own functionality as a potential regulator for growth of seedlings of model plant Vigna radiata. We undertook characterization of surface, morphology, epitome of porosity for MCM 41 and MCM 48 using various experimental techniques followed by application of the same to growing seedlings at various dosages. It turned out that mesoporous silica nanoparticles, inarguably have higher efficacy in promoting plant growth, reducing stress, and enhancing basic metabolic rates at optimum dosage. Optimal operation point was determined at effective dosages for MCM 41 and MCM 48 those are being much lower than that of conventional silica nanoparticles. This optimum dosage is attributed to the structures of the nanoparticles used and implied further that higher pore volume, higher surface to volume ratio in case of MCM 41 at higher dosage lead to better adsorption of ions and functionality in contrast to that of MCM 48.