Diatom Mediated Production of Fluorescent Flower Shaped Silver-Silica Nanohybrid

Fabrication of flower-like nanostructures are gaining attention because of their high surface/volume ratio and extensive adsorption capacity. In the present investigation, flower-shaped, autofluorescent silver-silica (Ag-SiO2) hybrid nanoparticles have been fabricated exploiting diatoms as a source of nanosilica. Two different species of Gedaniella including G. flavovirens and G. mutabilis showed their efficacy in synthesizing fluorescent Ag-SiO2 nanoflowers (NFs) and nanospheres (NSs) against 9 mM silver nitrate solution, respectively. The biogenic nanoconjugate (Ag-SiO2) was characterized by Uv-vis spectroscopy, energy dispersive X-ray spectroscopy (EDS), scanning (SEM) and transmission (TEM) electron microscopy. Production of Ag-SiO2 hybrid nanoparticle was confirmed by observing both Ag and Si signals from a single nanoparticle in an EDS study. The broad and single absorption band at ~420 nm in Uv-vis spectroscopy confirmed proper miscibility and production of hybrid nanoparticles. The Ag-SiO2 nanohybrids revealed autofluorescent property under the blue light region (excitation ~450–490 nm). SEM images of particles synthesized by G. flavovirens revealed the production of microscopic flower shaped Ag-SiO2 particles with several layers of petals. A TEM study confirmed that the synthesized Ag-SiO2 NFs are variable in size with 100–500 nm in diameter. Decolorization of methylene blue after exposure to Ag-SiO2 particles confirmed catalytic activity of synthesized nanostructures. This eco-friendly method provides a new dimension in nanobiotechnology for biogenesis of such hierarchical nanostructure in a cost-effective way.

Simulation of the evolution of agglomerated SiO2 particles in thermal plasma flow

The paper studies the behavior of agglomerated SiO2 particles in thermal plasma processing. The main stages are determined for their transformation to the hollow melt droplets. The proposed model, which includes partial encapsulation of gas, allows describing and analyzing the evolution stages for the particle size and the shell thickness in the ranges of 50-150 μm agglomerated particles and their 0.2-0.6 porosity.

Effects of SiO2 Contaminant on Thermo-Mechanical/Chemical Properties and Lubricity of PFPE Lubricants

Using the molecular dynamics (MD) simulations with ReaxFF potential, two different types of PFPE lubricants (Ztetraol and ZTMD) are prepared on a-C film, and SiO2 particles are adsorbed onto the lubricants at room temperature. From the simulation results, it is observed that the adsorbed SiO2 particles increase the stiffness of PFPE lubricants leading to less airshear displacement. Since Ztetraol has higher mobility with lower viscosity than ZTMD, the adsorbed SiO2 particles penetrate deeper into the Ztetraol lubricants. Accordingly, the effect of SiO2 on the airshear displacement is more obvious to Ztetraol than ZTMD. In addition, the adsorbed SiO2 particles increase the friction force and the amount of lubricant pick-up during the sliding contact with a nanosized a-C tip.

Determination of Two Differently Manufactured Silicon Dioxide Nanoparticles by Cloud Point Extraction Approach in Intestinal Cells, Intestinal Barriers and Tissues

Food additive amorphous silicon dioxide (SiO2) particles are manufactured by two different methods—precipitated and fumed procedures—which can induce different physicochemical properties and biological fates. In this study, precipitated and fumed SiO2 particles were characterized in terms of constituent particle size, hydrodynamic diameter, zeta potential, surface area, and solubility. Their fates in intestinal cells, intestinal barriers, and tissues after oral administration in rats were determined by optimizing Triton X-114-based cloud point extraction (CPE). The results demonstrate that the constituent particle sizes of precipitated and fumed SiO2 particles were similar, but their aggregate states differed from biofluid types, which also affect dissolution properties. Significantly higher cellular uptake, intestinal transport amount, and tissue accumulation of precipitated SiO2 than of fumed SiO2 was found. The intracellular fates of both types of particles in intestinal cells were primarily particle forms, but slowly decomposed into ions during intestinal transport and after distribution in the liver, and completely dissolved in the bloodstream and kidneys. These findings will provide crucial information for understanding and predicting the potential toxicity of food additive SiO2 after oral intake.