Comparison of Genotoxicity and Pulmonary Toxicity Study of Modified SiO2 Nanomaterials

Surface-modified nano-SiO2 is a common additive in many products. However, the safety of nano-SiO2 products under various modifications is still unclear. In this study, we investigated the genotoxicity and acute pulmonary toxicity of nano-SiO2 with or without modification. The samples used in this study included: sample A (SA, 55.16 nm, 411.3 mg/mL), modified sample A (mSA, 82.29 nm, 37.7 mg/mL), sample B (SB, 22 nm, 358.0 mg/mL), and modified sample B (mSB, 86.64 nm, 37.7 mg/mL). In the genotoxicity study, we conducted an Ames test, chromosomal aberration test (CA), and a micronucleus (MN) test. The SA, mSA, and mSB groups showed negative results in all these genotoxicity tests. Only SB showed a weakly positive reaction in these assays, but the genotoxicity could be reversed after S9 metabolism or modification. In the acute pulmonary toxicity test, the rats were given an intratracheal instillation (IT) (0.5 mL/kg) of diluted samples and sacrificed after 1 or 14 days. The mortality rate, number of leukocytes and cytokines of TNF-α in the bronchoalveolar lavage fluid (BALF), and the pathology in the lungs were determined. The results revealed that mSA posed acute toxicity in rats. After modification, the pulmonary toxicity was increased in mSA but decreased in mSB on Day 1, and no significant difference was observed on Day 14. In conclusion, there was no observed genotoxicity in either SA or SB, while mSA posed acute inhalation toxicity to rats that decreased in mSB after modification. This indicates that the decrease in pH level in SA and decrease in the solid content in SB are considered after the trifluorosilane surface-modified amorphous nano-silica.

Effects of dry particle coating with nano- and microparticles on early compressive strength of portland cement pastes

It is known that nano-and microparticles have been very popular in recent years since their advantages. However, due to the very small size of such materials, they have very high tendency to agglomeration particularly for nanoparticles. Therefore, it is critical that they are properly distributed in the system to which they are added. This paper investigated the effects of dry particle coating with nano-and microparticles to solve the agglomeration problem. For a clear evaluation, paste samples were preferred to detemine the compressive strength. Nano-SiO2 and nano-CaCO3, micro-CaCO3 and micro-SiO2, also known as silica fume, were selected as particulate additives. It was studied by the addition of various percentages (0.3, 0.7, 1, 2, 3 and 5%) of nano-and microparticles in cementitious systems, replacing cement by weight with and without dry particle coating. Dry particle coating was made by using a high-speed paddle mixer. Portland cement and additive particles were mixed at 1500 rpm for 30 seconds in high-speed powder mixer designed for this purpose. The 3-day compressive strength of the cement-based samples to which particles were added at the specified rates was determined and the effect of the dry particle coating on the early strength was investigated. According to the results, it was observed that the production of paste with the dry particle coating technique gave higher compressive strength compared to the production of paste directly in early period. Especially with dry particle coating, compressive strength increased more than 100% in paste samples containing 0.3% nano-SiO2 compared to direct addition without coating.

The Effects of Silicon Dioxide Nanoparticles and Zinc Oxide Nanoparticles on Waste Land soil Bacterial and Fungal Isolates

Objective: Different bacterial and fungal isolates were collected from the wasteland municipality site, Tambaram. The antimicrobial activity of two types of nanoparticles ZnO & SiO2 [Zinc oxide and Silicon dioxide] against several types of Gram-negative bacteria and fungi was investigated in this work. Methods: P. aeruginosa, B. subtilis, Penicillium oxalicum and Aspergillus fumigatus were isolated from 5 soil samples taken from three sites of Tambaram Municipality wasteland (Chennai). After collecting the samples, we used culturing and biochemical tests to identify the microbes and then used a chemical approach to make ZnO and SiO2 nanoparticles with altered structure and morphological features. Minimum inhibitory concentration (MIC) was used to assess the antibacterial activity of these nanoparticles against various microorganisms. Results: The best inhibition zone was found in Pseudomonas sps and Bacillus sps growth at concentrations of 10 µg/ml and 5 µg /ml of nano-ZnO, respectively, whereas the lower inhibition zone was found in Penicillium oxalicum and Aspergillus fumigatus at a dosage of 2.5 µg /ml of the same nanoparticle. It was also discovered that no inhibitory zone existed in any of the bacteria and fungi at a concentration of 10 µg /ml nano-SiO2. We found that all of the bacteria and fungi we tested were completely inhibited at a concentration of 1.25 g/ml nano-ZnO (MIC), with no antibacterial activity below this concentration. When compared to data that showed that all tested bacteria were not completely inhibited even at a concentration of 0.625 g/ml of nano-SiO2. Conclusion: In comparison to the two nanoparticles (ZnO and SiO2), nano-ZnO outperformed nano-SiO2 in inhibiting most bacteria and fungi at the quantities tested in wasteland soil.

Increase of Solid Polymer Electrolyte Ionic Conductivity Using Nano-SiO2 Synthesized from Sugarcane Bagasse as Filler

The synthesize of solid polymer electrolyte (SPE) based on polyethylene oxide (PEO), NaClO4 and nano-SiO2 was carried out by solution cast technique. Nano-SiO2 was synthesized from sugarcane bagasse using sol-gel method. FTIR analysis was carried out to investigate the bonding between nano-SiO2 and PEO/NaClO4. The morphology of the SPE was characterized using SEM. XRD and DSC analysis showed that SPE crystallinity decreased as nano-SiO2 concentration was increased. Mechanical analyses were conducted to characterize the SPE tensile strength and elongation at break. EIS analysis was conducted to measure SPE ionic conductivity. The PEO/NaClO4 SPE with the addition of 5% nano-SiO2 from sugarcane bagasse at 60 °C produced SPE with the highest ionic conductivity, 1.18 × 10−6 S/cm. It was concluded that the addition of nano-SiO2 increased ionic conductivity and interface stability at the solid polymer electrolyte-PEO/NaClO4.