Crystalline Silica Nanoparticles Research Articles

Efficacy of Olive Stones and Corncobs Crystalline Silica Nanoparticles (SiO2, NPs) Treatments on Potato Tuber Moths (Phthorimaea Operculella)

Morphological and microstructural properties of silica (SiO2) are essential factors that need to be considered during the experimental applications. In this report, SiO2 nanoparticles (NPs) have been prepared at different concentrations from SiO2 powder derived from olive stones and corncobs by an alkali leaching extraction method. Thermal treatment has been used to modify the morphological and microstructural properties of the extracted SiO2. X-ray diffraction (XRD) shows that the extracted amorphous SiO2 has been transformed into a crystalline phase after the thermal treatment. Nitrogen adsorption–desorption measurements revealed significant reduction in both the specific surface area (SABET) and the total pores volume (Vtotal) of the derived SiO2 samples after the thermal treatment. The acquired thermal treatment properties of SiO2 found to have high impacts on the influence of the SiO2 NPs on the survival and development of larvae and pupae of P. opercullela. SiO2 NPs prepared from the crystalline silica samples exhibited less efficiency on suppressing potato tuber moth comparing to SiO2 NPs of the amorphous silica powders. Varied effects on biological parameters including larvae mortality, pupae weight, larval and pupal development time, fecundity and fertility are also linked to the SiO2 NPs source type and showed concentration depending manner effects. SiO2 NPs are conditionally effective as an alternative pesticide against P. opercullela, based on their sources, mesoporous structures and concentrations.

Atomistic study of the effect of grain size and reinforcement particle on mechanical behavior of magnesium / silica nanocomposite

In the present study, the atomistic simulations were carried out to investigate the mechanical properties and deformation mechanisms of nanocrystalline magnesium with different grain sizes. Also, the effect of reinforcement particle position and structure on the mechanical behavior of nanocrystalline magnesium / (amorphous/crystalline) silica nanocomposite under uniaxial compression loading was studied by using the molecular dynamics method. Firstly, eight structure with the mean grain sizes from 5 to 24 nm of nanocrystalline magnesium were constructed using the Voronoi tessellation method, and used to study the deformation mechanism. The simulation results showed that the sample with an average grain size of 14 nm had the optimum mean flow stress. Furthermore, by increasing the average grain size to values close to coarse-grained structures (> 25 nm), an increasing in the dislocation density and elastic modulus was observed. Moreover, there are two distinct deformation mechanisms activated by decreasing grain size. The first one, the dislocation-dominated deformation mechanism, belonged to large average grain size (≥ 14 nm) samples, and the second one, the grain boundary sliding deformation mechanism, was observed in small grain-sized simulation samples. In the following, nanocrystalline Mg nanocomposite simulation samples with different amorphous silica nanoparticle positions were studied, and it was observed that the presence of nanoparticle in the triple junction among three grains had the main effect on the strength of nanocomposites compared to the samples with nanoparticle at the grain boundary or inside the grain. Accordingly, the maximum strength and fracture strain was observed in the simulation samples with nanoparticles in the triple junctions. The investigated structures showed that the partial dislocations and aggregation of FCC structure stacking faults as lamella structure defects were observed in all simulated nanocomposite samples. Also, the local atomic shear strain contour obtained by simulation of nanocrystalline magnesium reinforced by amorphous and crystalline silica nanoparticles showed different responses of amorphous and crystalline nanoparticles during compression loading. Furthermore, amorphous and crystalline silica with the same size have different effects on the mechanical properties of the magnesium: in which, amorphous silica not only increases the ultimate compressive strength but also increases the strain before fracture compared to crystalline silica. The results of this research can expand the use of amorphous ceramic nanoparticles as reinforcement instead of crystalline ceramic nanoparticles in the development of nanocomposite materials.

On the structure-properties relationship of amorphous and crystalline silica nanoparticles reinforced magnesium matrix nanocomposites

In this study, the structure-properties relationship of magnesium matrix nanocomposites was studied. Using an accumulative extrusion (AE) process, the matrix was reinforced by adding 0.25, 0.5 and 1 wt% crystalline and amorphous silica nanoparticles separately. The mechanical behavior of nanocomposite strips was investigated by hardness and uniaxial compression tests. The results indicated that the Mg/0.5%SiO2-Am had the best room temperature compressive properties. An increase of 28.5% in compressive yield strength after extrusion and 235% after annealing was measured. Ultimate compressive strength (UCS) was increased by 20% without reduction in the nanocomposite ductility compared to the pure magnesium strip. FESEM and OM were used for microstructural analysis and revealed no visible cracks or distinct defects between magnesium layers after AE passes. It is found from the EDS analysis that the reinforcement distribution after the AE process was uniform with few agglomerates. Texture analysis using X-ray diffraction and EBSD after the AE process for samples reinforced with 0.5 wt% of amorphous and crystalline silica nanoparticles indicated a negligible difference in the basal plane orientation of the monolithic and nanocomposite magnesium strips after the AE process along extrusion direction. On the other hand, increasing the basal plane peak intensity after annealing for the sample reinforced with amorphous silica compared to the sample reinforced with crystalline silica indicated a weakening of basal texture. Furthermore, the EBSD analysis showed that amorphous silica nanoparticles are more effective than crystalline silica in grain refinement.

Atomistic-level study of the mechanical behavior of amorphous and crystalline silica nanoparticles

Molecular dynamics method was used to simulate and investigate the mechanical behavior of amorphous and crystalline silica during nanoindentation and uniaxial compression tests in the nanoscale. Also, the hardness and elastic moduli were experimentally checked by nanoindentation tests. The MD nanoindentation simulation results show that the amorphous silica has an indentation modulus less than the crystalline one, and the elastic strain of the amorphous silica is higher than crystalline silica. In contrast, the amorphous silica has a lower hardness. The uniaxial compression test results show that both structures have three deformation stages during the tests. The first stage corresponds to the linear elastic region; the second stage indicates the elastic-plastic region for crystalline silica, and yielding stage in the amorphous silica. The last stage corresponds to the fracture region for crystalline structure and densification for the amorphous structure. By comparing the area under stress-strain curves of the two structures, it can be concluded that the absorbed energy under external stress in the amorphous silica is three times greater than that in the crystalline one. Moreover, the nanoindentation tests of SPS samples made of amorphous and crystalline silica were performed, and the results confirmed that the crystalline silica has higher hardness and indentation modulus than the amorphous silica. Also, comparing the indentation moduli obtained by simulation and experimental tests shows that the indentation modulus predicted by simulation is in good agreement with that obtained based on experimental results.

Fabrication of crystalline silica nanoparticles-embedded nanocomposites and their enhanced mechanical, thermal and insulating properties

Abstract Crystalline silica nanoparticles exhibit superior physical properties to amorphous phase when incorporated in nanocomposites. In this paper, we introduce the crystalline silica nanoparticles–embedded nanocomposites (CSN–nanocomposite) as a high-performance insulation material, and discuss their improved macro/microscopic properties according to the CSN contents. Monodisperse CSN particles (50 nm in size) are produced via facile and cost-effective top-down grinding methods, and their surfaces are modified with organic ligands to endure homogeneous dispersion and chemical crosslinking with epoxy matrix. With the aid of optimal hybridization of the CSN and the matrix, the CSN–nanocomposite exhibits high optical transparency, enhanced mechanical strength, increased thermal conductivity, and improved electrical insulating property.

High-throughput, quantitative assessment of the effects of low-dose silica nanoparticles on lung cells: Grasping complex toxicity with a great depth of field

The toxicity of manufactured fumed silica nanoparticles (NPs) remains poorly investigated compared to that of crystalline silica NPs, which have been associated with lung diseases after inhalation. Amorphous silica NPs are a raw material for manufactured nanocomposites, such as cosmetics, foods, and drugs, raising concerns about their potential toxicity. The size of the NPs was determined by dynamic light scattering and their shape was visualized by atomic force microscopy (10 ± 4 nm). The pertinent toxicological concentration and dynamic ranges were determined using viability tests and cellular impedance. We combined transcriptomics and proteomics to assess the cellular and molecular effects of fumed silica in A549 human alveolar epithelial cells. The “no observed transcriptomic adverse effect level” (NOTEL) was set to 1.0 μg/cm2, and the “lowest observed adverse transcriptional effect level” (LOTEL) was set at 1.5 μg/cm2. We carried out genome-wide expression profiles with microarrays and identified, by shotgun proteomics, the exoproteome changes in lung cells after exposure to NP doses (0.1, 1.0, 1.5, 3.0, and 6.0 μg/cm2) at two time points (24 h and 72 h). The data revealed a hierarchical, dose-dependent cellular response to silica NPs. At 1.5 μg/cm2, the Rho signaling cascade, actin cytoskeleton remodeling, and clathrin-mediated endocytosis were induced. At 3.0 μg/cm2, many inflammatory mediators were upregulated and the coagulation system pathway was triggered. Lastly, at 6.0 μg/cm2, oxidative stress was initiated. The proteins identified in the extracellular compartment were consistent with these findings. The alliance of two high-throughput technologies allowed the quantitative assessment of the cellular effects and molecular consequences of exposure of lung cells to low doses of NPs. These results were obtained using a pathway-driven analysis instead of isolated genes. As in photography, toxicogenomics allows, at the same time, the visualization of a wide spectrum of biological responses and a “zoom in” to the details with a great depth of field. This study illustrates how such an approach based on human cell culture models is a valuable predictive screening tool to evaluate the toxicity of many potentially harmful emerging substances, alone or in mixtures, in the framework of future regulatory reinforcements.

Inexpensive approach for production of high-surface-area silica nanoparticles from rice hulls biomass.

In this study, we prepared amorphous and crystalline silica nanoparticles from rice hulls biomass using pyrolysis technique at different processing temperatures such as 923, 973, 1023, 1073, 1123 and 1173 K. X-ray fluorescence studies show that the purity of all the synthesised silica nanoparticles is in the range of 98-99.7%. X-ray diffraction studies reveal that amorphous silica nanoparticles are formed at 923-1023 K, whereas crystalline particles at 1073-1173 K. Morphology and microstructure of silica nanoparticles are studied by scanning electron and transmission electron microscopes. Silica nanoparticles obtained at different processing temperatures yield particle size in the range of 6-100 nm. Chemical composition and surface functionalities of the particles are examined by energy-dispersive X-ray diffraction and Fourier transform infrared spectroscopic studies. The developed method effectively uses rice hulls biomass as a green natural source in the synthesis of amorphous and crystalline silica nanoparticles with high-specific surface area. The optimised processing temperature (1023 K) enables amorphous silica nanoparticles to have high-specific surface area of 538 m(2)g(-1).

Tamoxifen citrate: a glimmer of hope for silicosis

BackgroundInhalation of crystalline silica nanoparticles causes pulmonary damage resulting in progressive lung fibrosis. Currently, there is no effective treatment for silicosis. Tamoxifen citrate is a selective estrogen receptor modulator, which is one of the adjuvant treatment choices for breast cancer. It is also known with its inhibitory effect on the production of transforming growth factor-beta (TGF-β) and studied for the anti-fibrotic effect in some fibrotic diseases. The aim of the study was to determine the effect of tamoxifen citrate on the prevention of pulmonary fibrosis and the treatment of silicosis. MethodsA total of 100 adult female Wistar Albino rats (200–250 g) were used in this study. The rats were divided into five groups including 20 rats in each. Rats were exposed to silica for 84 d in all groups. In group 1, rats were sacrificed on the day 84 without receiving treatment. In group 2, rats received 1 mg/kg tamoxifen (tmx1 + 1), from the first day of the study for the whole 114 d of the study. In group 3, (tmx10 + 10) rats were given 10 mg/kg tamoxifen from the first day of the study for the whole 114 d of the study. In group 4 (tmx1), rats were started 1 mg/kg of tamoxifen on day 84 and were given until day 114. In group 5 (tmx10), rats were fed with 10 mg/kg tamoxifen starting from day 84 to day 114. All rats except group 1 were sacrificed on 114 day of the study. Lung inflammation and fibrosis scores, serum TGF β levels, lung smooth muscle antigen and tissue transforming growth factor β (t-TGF-β) antibody staining levels, and number of silicotic rats were compared between groups. ResultsSilicosis was caused successfully in all rats in group 1. There were six silicotic rats in group 3 and it was the lowest number of all groups. Plasma TGF-ß levels and fibrosis score were significantly lower in all groups when compared with the control group. Tamoxifen could have preventive or treating effects in silicosis and found that lung fibrosis score was significantly lower in rats treated with tamoxifen. ConclusionsTamoxifen treatment after and/or before induction of silicosis decreased lung fibrosis score with blood TGF-β levels. We hope that this study may introduce a new indication as prophylactic use of tamoxifen in high-risk groups for silicosis and for treatment of silicosis.

Physiological pathway of human cell damage induced by genotoxic crystalline silica nanoparticles

We disclosed a specific biological pathway for the observed cell damage when stimulated by the crystalline SiO2 nanoparticles (NPs), i.e., both mitochondrion multiplication and DNA fragmentation occur upon the initial reactive oxygen species (ROS) generation, with the former causing further increases of the ROS level in the cell, and eventually leads to catastrophic effect on cell physiology. Such damage becomes nontrivial only in the absence of p53 gene, which regulates cells' anti-oxidation and detoxification. This genotoxic effect is absent in cells treated with amorphous SiO2 NPs.

Fungus-Mediated Biotransformation of Amorphous Silica in Rice Husk to Nanocrystalline Silica

Rice husk is a cheap agro-based waste material, which harbors a substantial amount of silica in the form of amorphous hydrated silica grains. However, there have been no attempts at harnessing the enormous amount of amorphous silica present in rice husk and its room-temperature biotransformation into crystalline silica nanoparticles. In this study, we address this issue and describe how naturally deposited amorphous biosilica in rice husk can be bioleached and simultaneously biotransformed into high value crystalline silica nanoparticles. We show here that the fungus Fusarium oxysporum rapidly biotransforms the naturally occurring amorphous plant biosilica into crystalline silica and leach out silica extracellularly at room temperature in the form of 2-6 nm quasi-spherical, highly crystalline silica nanoparticles capped by stabilizing proteins; that the nanoparticles are released into solution is an advantage of this process with significant application and commercial potential. Calcination of the silica nanoparticles leads to loss of occluded protein and to an apparently porous structure often of cubic morphology. The room-temperature synthesis of oxide nanomaterials using microorganisms starting from potential cheap agro-industrial waste materials is an exciting possibility and could lead to an energy-conserving and economically viable green approach toward the large-scale synthesis of oxide nanomaterials.