Amorphous Silica Nanoparticles Research Articles

Effects of process variable on synthesis and characterization of amorphous silica nanoparticles using sodium silicate solutions as precursor by sol–gel method

The recent rapid urban growth has resulted into high demand for virgin materials thus causing more accumulation of solid wastes (urban mines). As a result, efforts are now geared towards urban mining approach based on re-using and recycling in order to ensure sustainability and environmental protection. In this regard, the present work synthesized pure amorphous silica nanoparticles using sodium silicate solutions produced from recycled glass powder under varying process parameter. In this work, the process variable used was NaOH concentration (3.0, 4.0 and 5.0 mol/L). 20 g of glass powder was reacted with 160 ml of 3.0, 4.0 and 5.0 mol/L NaOH solutions respectively in a 250 ml Erlenmeyer flask placed on a heating plate connected with a reflux condenser to maintain the volume of the mixture and stirred continuously at a speed of 60 rpm for 180 mins under reaction temperature of 200 °C. The solutions were filtered to obtain a sodium silicate solution (SSLS) samples. Hydrochloric acid (3 mol/L) was added gently into the respective SSLS while continuously stirred to obtain a white gel mixture. The gel was left to age for 18 h at room temperature (25 °C), then filtered and washed repeatedly using deionized water until a neutral pH is reached; then dried in an electric-powered oven at 80 °C for 12 h to obtain highly pure white silica powder. The results showed that the nano-size range between 0.025 μm (25 nm) to 0.067 μm (67 nm).

One-step fabrication of transparent superhydrophobic surface

A self-cleaning, transparent superhydrophobic silica-based surface with water contact angle (CA)/sliding angle (SA) 168°/2° was fabricated by simple one-step thermal oxidation of silicone grease. Microstructural studies (FESEM/TEM) confirmed the presence of a sponge-like pore structure of amorphous silica nanoparticle having a diameter of around 20 ± 2.2 nm. EDS analysis confirms the presence of C, Si, and O in coated substrates. Also, phase and thermal studies (XRD, FTIR, and TG-DSC) analysis showed the thermo-oxidative decomposition of silicone grease results in superhydrophobic –H2C-Si-O-Si-CH2- network structure at 400 °C followed by thermally stable superhydrophilic HO-Si-O-Si-OH network structure at 500 °C. The coated surface showed excellent stability towards corrosive liquids (1 M NaCl, NaOH, HCl aqueous solution, and hot water) and exposed temperature up to 400 °C. The maximum visible light transparency of the superhydrophobic glass was 92.4% compared to the uncoated glass (93.3%). Thus, making transparent superhydrophobic surfaces by a simple and straightforward process can be potentially used in self-cleaning glasses for various engineering applications.

Nanoscale Anatomy of Iron‐Silica Self‐Organized Membranes: Implications for Prebiotic Chemistry

AbstractIron‐silica self‐organized membranes, so‐called chemical gardens, behave as fuel cells and catalyze the formation of amino/carboxylic acids and RNA nucleobases from organics that were available on early Earth. Despite their relevance for prebiotic chemistry, little is known about their structure and mineralogy at the nanoscale. Studied here are focused ion beam milled sections of iron‐silica membranes, grown from synthetic and natural, alkaline, serpentinization‐derived fluids thought to be widespread on early Earth. Electron microscopy shows they comprise amorphous silica and iron nanoparticles of large surface areas and inter/intraparticle porosities. Their construction resembles that of a heterogeneous catalyst, but they can also exhibit a bilayer structure. Surface‐area measurements suggest that membranes grown from natural waters have even higher catalytic potential. Considering their geochemically plausible precipitation in the early hydrothermal systems where abiotic organics were produced, iron‐silica membranes might have assisted the generation and organization of the first biologically relevant organics.

Nanoscale Anatomy of Iron‐Silica Self‐Organized Membranes: Implications for Prebiotic Chemistry

Iron‐silica self‐organized membranes, so‐called chemical gardens, behave as fuel cells and catalyze the formation of amino/carboxylic acids and RNA nucleobases from organics that were available on early Earth. Despite their relevance for prebiotic chemistry, little is known about their structure and mineralogy at the nanoscale. Studied here are focused ion beam milled sections of iron‐silica membranes, grown from synthetic and natural, alkaline, serpentinization‐derived fluids thought to be widespread on early Earth. Electron microscopy shows they comprise amorphous silica and iron nanoparticles of large surface areas and inter/intraparticle porosities. Their construction resembles that of a heterogeneous catalyst, but they can also exhibit a bilayer structure. Surface‐area measurements suggest that membranes grown from natural waters have even higher catalytic potential. Considering their geochemically plausible precipitation in the early hydrothermal systems where abiotic organics were produced, iron‐silica membranes might have assisted the generation and organization of the first biologically relevant organics.

A Landscape of lncRNA Expression Profile and the Predictive Value of a Candidate lncRNA for Silica-Induced Pulmonary Fibrosis.

Silicosis is the most common type of pneumoconiosis with the fastest progress and the most serious harm. At present, there is still a lack of effective treatment for silicosis, and the molecular mechanism of silicosis is very complex, which is not completely clear. This study aimed to identify crucial long noncoding RNA (lncRNA)-mRNA networks for silica-induced pulmonary fibrosis using microarray data from Gene Expression Omnibus database, including human lung epithelial cells Beas-2B and continuously exposed to 5 μg/mL amorphous silica nanoparticles for 40 passages. Differently expressed genes were calculated by "DESeq2" R package. Then we selected the differently expressed mRNAs (DEmRNAs) and differently expressed long noncoding RNAs (DElncRNAs) data construct lncRNA-mRNA coexpression network using weighted gene coexpression network analysis (WCGNA). A total of 1140 DEmRNA and 1406 DElncRNAs were identified, including 20 upregulated DEmRNAs, 1120 downregulated DEmRNAs as well as 213 upregulated DElncRNAs and 1193 downregulated DElncRNAs. Furthermore, we demonstrate that lncRNA AK131029 was specifically overexpressed in silicosis. Loss-of-function assay indicated that silencing AK131029 of inhibited cell proliferation in human lung fibroblast cells. In conclusion, this study preliminarily indicates that lncRNA AK131029 may play a role in pulmonary fibrosis.

Increasing the Resistance of the Body to Adverse Cytotoxic Effects of Amorphous Silicon Dioxide Nanoparticles

Introduction: Amorphous silicon dioxide nanoparticles of (SiNPs) are among the most common nanomaterials today. Besides, industrial aerosols formed by condensation and containing a significant proportion of SiNPs are spontaneously produced by a number of pyrometallurgical and welding processes. A significant number of individuals are therefore exposed to SiNPs in the occupational setting or polluted ambient air and while using this nanomaterial. The purpose of our experimental study was to develop a preventive method promoting the resistance of the organism to adverse cytotoxic effects of amorphous silicon dioxide nanoparticles. Materials and methods: White laboratory rats received a monthly course of a specially developed bioprophylactic complex (BPC) before a single intratracheal instillation of a SiNPs suspension at a concentration of 0.5 mg/mL. The suspension was obtained by laser ablation of thin sheet targets of the appropriate material of 99.99 % purity in sterile deionized water. The average diameter of SiNPs was 43 ± 11 nm. Cytological (the number of bronchoalveolar macrophages and neutrophils and their ratio) and cytochemical indices of the bronchoalveolar lavage (BAL) fluid (alkaline phosphatase, alanine aminotransferase, gamma-glutamyl transpeptidase, amylase, and lactate dehydrogenase) were evaluated at 24 hours after the injection. The bioprophylactic complex was administered to the animals with feed and drink and included monosodium glutamate, fish oil rich in omega-3 polyunsaturated fatty acids (PUFAs), iodine, and an antioxidant complex of selenium, quercetin (rutoside), and vitamins A, E, and C. Conclusions: Our findings show that changes in both cytological and biochemical BAL parameters proved a positive health effect of premedication that helped reduce cytotoxicity of SiNPs exposure.

Effect of Silicon Dioxide Nanoparticles on Syrian Hamsters Infected by Opisthorchis felineus: 1H MRS Study of the Brain.

In recent years, silicon dioxide nanoparticles have been widely used in medicine and the pharmaceutical industry, however, their effect on the brain has hardly been studied. We assessed the effects of long-term consumption of 5-nm amorphous silicon dioxide nanoparticles (SiO2-NPs) by Syrian hamsters infected with the trematodes Opisthorchis felineus on the hippocampus and frontal cortex. Spectroscopic determination of brain neurometabolites, performed using a horizontal Magnetic Resonance Imaging system at 11.7 Tesla magnetic field, has shown that the ratio of the excitatory neurotransmitters (glutamate + glutamine + aspartate) to the inhibitory ones (GABA + glycine) was higher in the animals infected with O. felineus. However, pre-consumption of the SiO2-NPs solution prevented this imbalance. In addition, the protective effect of SiO2-NPs on the level of myo-inositol and glycine was found. It is concluded that the use of SiO2-NPs can neutralize the negative effects of infectious factors on the brain.

The Size-dependent Cytotoxicity of Amorphous Silica Nanoparticles: A Systematic Review of in vitro Studies.

With the increasing production and application of engineered amorphous silica nanoparticles (aSiNPs), people have more opportunities to be exposed to aSiNPs. However, the knowledge of its adverse health effects and related mechanisms is still limited, compared with the well-studied crystalline micron-sized silica. Since small differences in the physical–chemical properties of nanoparticles could cause significant differences in the toxic effect, it is important to distinguish how these variations influence the outcoming toxicity. Notably, particle size, as one of the essential characterizations of aSiNPs, is relevant to its biological activities. Thus, the aim of this systematic review was to summarize the relationship between the particle size of aSiNPs and its adverse biological effects. In order to avoid the influence of complicated in vivo experimental conditions on the toxic outcome, only in vitro toxicity studies which reported on the cytotoxic effect of different sizes aSiNPs were included. After the systematic literature retrieval, selection, and quality assessment process, 76 eligible scientific papers were finally included in this review. There were 76% of the studies that concluded a size-dependent cytotoxicity of aSiNPs, in which smaller-sized aSiNPs possessed greater toxicity. However, this trend could be modified by certain influence factors, such as the synthetic method of aSiNPs, particle aggregation state in cell culture medium, toxicity endpoint detection method, and some other experimental conditions. The effects of these influence factors on the size-dependent cytotoxicity of aSiNPs were also discussed in detail in the present review.

Occupational exposure to graphene and silica nanoparticles. Part I: workplace measurements and samplings

Few-Layers Graphene (FLG) are able to improve the performance of materials, due to their chemical-physical properties. Engineered amorphous silica nanoparticles (SiO2NPs) are among the most widespread nanomaterials (NMs) in the world. Such nanomaterials are two case studies of the research project ‘NanoKey’ that integrated the exposure assessment through personal measurements and sampling in the workplace, as described in the present work (part I), with the biomonitoring of exposed workers (reported in part II). Measurement campaigns were conducted according to OECD and WHO harmonized approach in two production sites. The set of instruments included real-time devices for high-resolution measurements at the nanoscale and time-integrated samplers for the off-line gravimetric analysis and chemical and morphological (SEM-EDS) characterization of exposure in order to identify the contribution of production compared to the background. Values of particle number concentration (PNC) and lung deposited surface area (LDSA) within the FLG production resulted higher than the background far field (FF), even if they are always similar to the near field (NF) ones: the average diameter (Davg) during the production was higher than the NF background but always lower than the FF values. SEM-EDS analysis highlighted the presence of structures comparable to those produced. During the SiO2NPs production, the PBZ values showed PNC and LDSA levels higher than the background, with a decrease in the Davg probably due to NPs emission. SEM-EDS confirms the presence of rare silica nanoparticles. Since the exposure to airborne NMs cannot be excluded in both production sites, a prevention-through-design approach to mitigate the potential risk for workers has been recommended.

Amorphous silica nanoparticles accelerated atherosclerotic lesion progression in ApoE\u2212/\u2212 mice through endoplasmic reticulum stress-mediated CD36 up-regulation in macrophage

BackgroundThe biosafety concern of silica nanoparticles (SiNPs) is rapidly expanding alongside with its mass production and extensive applications. The cardiovascular effects of SiNPs exposure have been gradually confirmed, however, the interaction between SiNPs exposure and atherosclerosis, and the underlying mechanisms still remain unknown. Thereby, this study aimed to explore the effects of SiNPs on the progression of atherosclerosis, and to investigate related mechanisms.ResultsWe firstly investigated the in vivo effects of SiNPs exposure on atherosclerosis via intratracheal instillation of ApoE−/− mice fed a Western diet. Ultrasound microscopy showed a significant increase of pulse wave velocity (PWV) compared to the control group, and the histopathological investigation reflected a greater plaque burden in the aortic root of SiNPs-exposed ApoE−/− mice. Compared to the control group, the serum levels of total triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C) were elevated after SiNPs exposure. Moreover, intensified macrophage infiltration and endoplasmic reticulum (ER) stress was occurred in plaques after SiNPs exposure, as evidenced by the upregulated CD68 and CHOP expressions. Further in vitro, SiNPs was confirmed to activate ER stress and induce lipid accumulation in mouse macrophage, RAW264.7. Mechanistic analyses showed that 4-PBA (a classic ER stress inhibitor) pretreatment greatly alleviated SiNPs-induced macrophage lipid accumulation, and reversed the elevated CD36 expression induced by SiNPs.ConclusionsOur results firstly revealed the acceleratory effect of SiNPs on the progression of atherosclerosis in ApoE−/− mice, which was related to lipid accumulation caused by ER stress-mediated upregulation of CD36 expression in macrophage.Graphical abstract

Toxic Impacts of Amorphous Silica Nanoparticles on Liver and Kidney of Male Adult Rats: an In Vivo Study.

The toxic effects of the amorphous silica nanoparticles have not been thoroughly studied. Moreover, the majority of the in vivo investigations were performed using an inhalation exposure method. The current study aimed to explore the potential toxic effects of silica nanoparticles (SiNPs) after the treatment of adult male rats with two different concentrations (500 and 1000 ppm) via drinking water for 28 days. The genotoxicity, antioxidant status, and liver and kidney functions were assessed. Besides, histopathological and immunohistochemical evaluations were performed. The results showed a significant elevation in the malondialdehyde (MDA) level concurrent with a reduction in total reduced glutathione (GSH) concentration and catalase activity in the 1000-ppm SiNP-exposed rats as well as increase in ALT and AST activity confirmed by various histopathological alterations detected in liver. Also, in the 1000-ppm SiNP-exposed animals, there was an elevation in urea and creatinine levels confirmed by histopathological alterations detected in kidneys. Immunohistochemical findings in both liver and kidneys indicated strong expression of caspase-3 in the 1000-ppm SiNP-treated rats compared with the control and 500-ppm SiNP-treated groups. Such findings indicated that the 1000-ppm SiNPs exerted severe hepato-renal toxic impacts when compared with the control and 500-ppm SiNP-exposed rats.

Synthetic amorphous silica nanoparticles: toxicity, biomedical and environmental implications

Natural silica and silicates are predominantly crystalline and constitute the most abundant components of the Earth’s crust. Man-made silica is typically amorphous and manufactured in tonnage quantities for commercial use and, more recently, for burgeoning medical applications, making synthetic amorphous silica nanoparticles (SASNs) arguably the most abundant nanoparticles on Earth. Despite the abundance of silica and SASNs, misconceptions remain regarding what silica is and its medical and environmental implications. SASNs are often considered to be toxic regardless of their source, but, here, we emphasize that all silica nanoparticles are not created equal and explore how composition, synthesis, processing and environmental exposure effect toxicity. Despite having comparable size, shape and nominal composition, SASNs prepared by pyrolytic or colloidal processes can have drastically different toxicities, which, to date, is not generally recognized by the research community. In this Review, we begin with a survey of relationships between synthetic methods and material structure, followed by structure–toxicity relationships. Next, we explore the environmental implications of SASNs exposure and provide a review of the emerging biomedical uses of SASNs in therapy, imaging and theranostics. We conclude with our vision for the field and suggest that minimal SASN characterization standards are needed for reporting and understanding their biological or environmental behaviours and implications. Synthetic amorphous silica nanoparticles are produced in tonnage quantities for a range of commercial uses. In this Review, the synthesis–structure–property relationships of synthetic amorphous silica nanoparticles are outlined, with an emphasis on biomedical applications and environmental implications.

Designing Colloidal Silica-Bonded Porous Structures of In-situ Mullite for Thermal Insulation

Abstract: Colloidal silica (CS) is a promising raw material for refractory castable ceramics. It consists of stable suspensions of synthetic amorphous silica nanoparticles that behave simultaneously as liquid medium and binder for ceramic particles and as a porogenic agent and highly reactive source of silica to promote in-situ reactions. The setting mechanism of CS balances two opposite effects. Adding more CS to a suspension increases the bonding potential for gelling reactions and strengthening; on the other hand, it also introduces more water into the system, enhancing pore content. Such effects can be advantageously employed in the preparation of porous structures from aqueous suspensions and applied as high-temperature thermal insulators. The present study addresses the production of porous structures of in-situ mullite attained from aqueous suspensions of highly porous transition alumina particles bonded with colloidal silica. Different grades of CS and transition aluminas were combined to present suitable workability (flowability and gelling time) and to generate stoichiometric mullite or mullite-alumina porous structures after sintering.

Toxicologic Evaluation for Amorphous Silica Nanoparticles: Genotoxic and Non-Genotoxic Tumor-Promoting Potential.

Amorphous silica nanoparticles (SiO2NPs) have been widely used in medicine including targeted drug/DNA delivery, cancer therapy, and enzyme immobilization. Nevertheless, SiO2NPs should be used with caution due to safety concerns associated with unique physical and chemical characteristics. The objective of this study was to determine the effects of SiO2NPs on genotoxic and non-genotoxic mechanisms associated with abnormal gap junctional intercellular communication (GJIC) in multistage carcinogenesis. The SiO2NPs exhibited negative responses in standard genotoxicity tests including the Ames test, chromosome aberration assay, and micronucleus assay. In contrast, the SiO2NPs significantly induced DNA breakage in comet assay. Meanwhile, SiO2NPs inhibited GJIC based on the results of scrape/loading dye transfer assay for the identification of non-genotoxic tumor-promoting potential. The reduction in expression and plasma membrane localization of Cx43 was detected following SiO2NP treatment. Particularly, SiO2NP treatment increased Cx43 phosphorylation state, which was significantly attenuated by inhibitors of extracellular signal-regulated kinases 1/2 (ERK1/2) and threonine and tyrosine kinase (MEK), but not by protein kinase C (PKC) inhibitor. Taken together, in addition to a significant increase in DNA breakage, SiO2NP treatment resulted in GJIC dysregulation involved in Cx43 phosphorylation through the activation of mitogen-activated protein kinase (MAPK) signaling. Overall findings of the genotoxic and non-genotoxic carcinogenic potential of SiO2NPs provide useful toxicological information for clinical application at an appropriate dose.

Synthesis and photoluminescence properties of the Eu(III)-containing silica nanoparticles via a mechanochemical solid-state reaction between SiO2 and EuCl3·6H2O

In this study, Eu3+-containing amorphous silica nanoparticles and Eu compounds were successfully synthesized via a mechanochemical solid-state reaction between silica nanoparticles and EuCl3·6H2O. This reaction was induced by a grinding process, and the states of Eu3+ in the silica/europium composites were investigated. The silica/europium composites exhibited orange–red color luminescence owing to the 5D0–7F0, 5D0–7F1, and 5D0–7F2 transitions, which indicated the presence of Eu3+ in the silica framework and the newly formed Eu compounds such as EuOCl and Eu(OH)2Cl. The mechanochemical reaction because of the grinding process effectively induced an interaction between the silica surface and europium chloride; subsequently, Eu(OH)2Cl was formed in the silica/europium composites. Additionally, the Eu(OH)2Cl in the silica/europium composite exhibited a higher thermal stability than that of simple Eu(OH)2Cl, indicating that the mechanochemical reaction mediated the formation of Eu(OH)2Cl and new chemical bonding between the newly formed Eu(OH)2Cl and the silica surface, providing improved thermal stability to Eu(OH)2Cl. Thus, we successfully prepared silica nanoparticles containing not only Eu(III) in the silica framework but also Eu compounds that exhibit unique chemical bonding during a mechanochemical reaction.

Production and characterization of silica nanoparticles from fly ash: conversion of agro-waste into resource

A chemical method to synthesize amorphous silica nanoparticles from the incinerated paddy straw has been introduced. The synthesis was conducted through the hydrolysis by alkaline-acidic treatments. As a result, silica particles produced with the sizes were ranging at 60–90 nm, determined by high-resolution microscopy. The crystallinity was confirmed by surface area electron diffraction. Apart from that, chemical and diffraction analyses for both rice straw ash and synthesized silica nanoparticles were conducted by X-ray diffraction and Fourier-transform infrared spectroscopy. The percentage of silica from the incinerated straw was calculated to be 28.3. The prominent surface chemical bonding on the generated silica nanoparticles was with Si–O–Si, stretch of Si–O and symmetric Si–O bonds at peaks of 1090, 471, and 780 cm−1, respectively. To confirm the impurities of the elements in the produced silica, were analyzed using X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. The stability of silica nanoparticles was investigated using thermogravimetric analysis and zeta potential. The measured size from zeta potential analysis was 411.3–493 nm and the stability of mass reduction was located at 200 °C with final amount of mass reduced ∼88% and an average polydispersity Index was 0.195–0.224.

Pyrogenic and Precipitated Amorphous Silica Nanoparticles Differentially Affect Cell Responses to LPS in Human Macrophages.

Previous work has demonstrated that precipitated (NM-200) and pyrogenic (NM-203) Amorphous Silica Nanoparticles (ASNPs) elicit the inflammatory activation of murine macrophages, with more pronounced effects observed with NM-203. Here, we compare the effects of low doses of NM-200 and NM-203 on human macrophage-like THP-1 cells, assessing how the pre-exposure to these nanomaterials affects the cell response to lipopolysaccharide (LPS). Cell viability was affected by NM-203, but not by NM-200, and only in the presence of LPS. While NM-203 stimulated mTORC1, neither ASNPs activated NFκB or the transcription of its target genes PTGS2 and IL1B. NM-200 and NM-203 caused a block of the autophagic flux and inhibited the LPS-dependent increase of Glutamine Synthetase (GS) expression. Both ASNPs suppressed the activation of caspase-1, delaying the LPS-dependent secretion of IL-1β. Thus, ASNPs modulate several important pathways in human macrophages, altering their response to LPS. NM-203 had larger effects on autophagy, mTORC1 activity and GS expression than NM-200, confirming the higher biological activity of pyrogenic ASNPs when compared with precipitated ASNPs.

Comprehensive Analysis of SiNPs on the Genome-Wide Transcriptional Changes in Caenorhabditis elegans.

BackgroundLarge-scale production and application of amorphous silica nanoparticles (SiNPs) have enhanced the risk of human exposure to SiNPs. However, the toxic effects and the underlying biological mechanisms of SiNPs on Caenorhabditis elegans remain largely unclear.PurposeThis study was to investigate the genome-wide transcriptional alteration of SiNPs on C. elegans.Methods and ResultsIn this study, a total number of 3105 differentially expressed genes were identified in C. elegans. Among them, 1398 genes were significantly upregulated and 1707 genes were notably downregulated in C. elegans. Gene ontology analysis revealed that the significant change of gene functional categories triggered by SiNPs was focused on locomotion, determination of adult lifespan, reproduction, body morphogenesis, multicellular organism development, endoplasmic reticulum unfolded protein response, oocyte development, and nematode larval development. Meanwhile, we explored the regulated effects between microRNA and genes or signaling pathways. Pathway enrichment analysis and miRNA-gene-pathway-network displayed that 23 differential expression microRNA including cel-miR-85-3p, cel-miR-793, cel-miR-241-5p, and cel-miR-5549-5p could regulate the longevity-related pathways and inflammation signaling pathways, etc. Additionally, our data confirmed that SiNPs could disrupt the locomotion behavior and reduce the longevity by activating ins-7, daf-16, ftt-2, fat-5, and rho-1 genes in C. elegans.ConclusionOur study showed that SiNPs induced the change of the whole transcriptome in C. elegans, and triggered negative effects on longevity, development, reproduction, and body morphogenesis. These data provide abundant clues to understand the molecular mechanisms of SiNPs in C. elegans.

Synthesis of SiO2-Nanoparticles from Rice Husk Ash and its Comparison with Commercial Amorphous Silica through Material Characterization

Silica is a major inorganic component of rice husk and present in the form of nanoparticle in it. Therefore, it is possible to extract high purity amorphous silica nanoparticles by simple thermo-chemical treatments. So, in this study amorphous silica nanoparticles were tried to produce from rice husk ash through an eco-friendly chemical treatment approach. Characteristics of the extracted nanoparticles were validated by comparing with commercial grade amorphous silica nanoparticles using several material characterization techniques. From X-ray diffraction analysis and Transmission electron microscopy-Selected area electron diffraction patterns, the amorphous behavior was observed for both silica samples, while from Fourier-transform infrared spectroscopy spectra, predominantly siloxane and silanol groups were found. From Scanning Electron, Transmission Electron and Atomic Force Microscopy images, the presence of primary nanoparticles were evidenced along with secondary micro-particles, maybe due to their agglomeration. The diameter of particle was in the range of 17.71 ± 7.53 nm and 19.49 ± 13.03 nm for the extracted silica and commercial grade amorphous silica, respectively. Hence, this silica nanoparticles can be utilized in the field of microelectronics, sensors, nano-additives etc.

Atomic Structure and Morphology of Fumed Silica

The comparative analysis of atomic structure and morphology of fumed silica nanoparticles prepared under different synthesis conditions are studied using TEM, FTIR, quantum chemistry, and low-temperature nitrogen adsorption methods. It was determined that the structure of amorphous silica nanoparticles is formed by branched chain-like clusters of the length of 0.6-2.4 nm that correspond to proto-particles or nuclei of nanoparticles. A linear part of the smallest clusters is consisted of two tetrahedra SiO4 with common oxygen atom and oppositely directed vertices. The inter-tetrahedral average angle of Si ‒ O ‒ Si bonds is about 180˚. It is shown that textural porosity of fumed silica powder depends on the initial degree of aggregation of nanoparticles. The average mesopores (1 nm < R < 25 nm) volume is in the rage of 0.26-0.60 cm3∙g-1 for materials pretreated at different temperatures. It is found out that the mean mesopores radius decreases from 34 nm to 10 nm with decreasing average size of silica nanoparticles. The micropores (R < 1 nm) contribution to the total pore volumes is small for all materials (0.003-0.029 cm3∙g-1).