Diameter Silica Particles Research Articles

Influence of Surface Roughness on Interfacial Properties of Particle Networks

The behavior of colloidal particles near fluid interfaces has attracted significant scientific interest, as particles minimize the contact area between the two fluid phases, stabilizing interfacial systems. This study explores the influence of surface roughness on the properties of particle monolayers at the air–water interface, focusing on colloidal silica particles and fumed silica particles of similar hydrodynamic diameter. This research involves comparing low-surface-area (LSA) and medium-surface-area (MSA) fumed silica particles with spherical colloidal silica particles (250 nm in diameter). Utilizing a Langmuir trough, the interfacial particle networks are compressed and expanded. Analysis of surface pressure isotherms reveals that fumed silica particle monolayers form networks at a lower particle surface coverage compared to spherical particles. The spherical particle monolayer exhibits a higher apparent surface elasticity, indicating greater resistance to the applied compression compared to fumed silica networks. Additionally, monolayers formed by fumed silica particles display hysteresis even after successive compressions and expansions due to irreversible particle interlocking and the formation of multilayered aggregates. These findings provide insights into the impact of surface roughness on the behavior of particle monolayers at fluid interfaces, offering valuable information for designing and optimizing mechanisms involved in emulsion and foam stabilization.

ALKBH5 mediates silica particles-induced pulmonary inflammation through increased m6A modification of Slamf7 and autophagy dysfunction

Silica particles are commonly encountered in natural and industrial activities. Long-term environmental exposure to silica can result in silicosis, which is characterized by chronic inflammation and abnormal tissue repair in lung. To uncover the role of m6A modification in silica-induced pulmonary inflammation, we conducted this study using established mouse and macrophage models. In this study, the aerodynamic diameter of silica particles was approximately 1–2 µm. We demonstrated that silica exposure in mice caused pulmonary inflammation and increased global m6A modification levels, the downregulation of alkB homolog 5 (ALKBH5) might contribute to this alteration. Besides, we found that F4/80, a macrophage-specific biomarker, was co-expressed with ALKBH5 through dual immunofluorescent staining. In vitro studies using MeRIP assays suggested that Slamf7 was a target gene regulated by m6A modification, and specific inhibition of ALKBH5 increased Slamf7 expression. Mechanistically, ALKBH5 promoted m6A modification of Slamf7, which decreased Slamf7 mRNA stability in an m6A-dependent manner, ultimately regulating Slamf7 expression. In addition, silica exposure activated PI3K/AKT and induced macrophage autophagy. Inhibition of Slamf7 promoted autophagy, reduced the secretion of pro-inflammatory cytokines, and improved silica-induced pulmonary inflammation. In summary, ALKBH5 can regulate silica-induced pulmonary inflammation by modulating Slamf7 m6A modification and affecting the function of macrophage autophagy.

Boosting Thermoelectric Power Factor of Carbon Nanotube Networks with Excluded Volume by Co-Embedded Microparticles.

Carbon nanotube (CNT) networks embedded in a polymer matrix have been extensively studied as a flexible thermoelectric transport medium over the recent years. However, their power factor has been largely limited by the relatively inefficient tunneling transport at junctions between CNTs and the low-density conducting channels throughout the networks. This work demonstrates that significant power factor enhancements can be achieved by adding electrically insulating microscale particles in three-dimensional CNT networks embedded in the polymer matrix. When silica particles of a few μm diameters were co-embedded in single-walled CNT (SWCNT)-polydimethylsiloxane (PDMS) composites, both the electrical conductivity and the Seebeck coefficient were simultaneously enhanced, thereby boosting the power factor by more than a factor of six. We found that the silica microparticles excluded a large volume of the composite from the access of CNTs and caused CNT networks to form around them with the polymer as a binder, resulting in improved network connectivity and alignment of CNTs. Our theoretical calculations based on junction tunneling transport for three-dimensional CNT networks show that the significant power factor enhancement can be attributed to the enhanced tunneling with reduced junction distance between CNTs. Additional power factor enhancement by a factor of three was achieved by sample compression, which further reduced the mean junction distance to enhance tunneling but also reduced the geometric factor at the same time, limiting the enhancement of electrical conductivity.

Fabrication of light trapping structures specialized for near-infrared light by nanoimprinting for the application to thin crystalline silicon solar cells

Vehicle-integrated photovoltaics (VIPV) are gaining attention to realize a decarbonized society in the future, and the specifications for solar cells used in VIPV are predicated on a low cost, high efficiency, and the ability to be applied to curved surfaces. One way to meet these requirements is to make the silicon substrate thinner. However, thinner substrates result in lower near-infrared light absorption and lower efficiency. To increase light absorption, light trapping structures (LTSs) can be implemented. However, conventional alkali etched pyramid textures are not specialized for near-infrared light and are insufficient to improve near-infrared light absorption. Therefore, in this study, as an alternative to alkaline etching, we employed a nanoimprinting method that can easily fabricate submicron-sized LTSs on solar cells over a large area. In addition, as a master mold fabrication method with submicron-sized patterns, silica colloidal lithography was adopted. As a result, by controlling silica coverage, diameter of silica particles (D), and etching time (tet), the density, height, and size of LTSs could be controlled. At the silica coverage of 40%, D = 800 nm, and tet = 5 min, the reduction of reflectance below 65% at 1100 nm and the theoretical short-circuit current gain of 1.55 mA/cm2 was achieved.

Fabrication and optical characteristics of opal photonic crystal films and heterostructures

The relevance of fabrication and investigation of opals and opal-based structures is due to their ability to control the emission and propagation of light. Using the method of vertically moving meniscus we obtain both single opal films and two-film heterostructures. By examining reflectance spectra, we analyze the influence of the ratio of synthesis components on silica particle diameter. Features of the heterostructure reflectance spectrum are also discussed by considering the contribution of light scattering by the interface.

A Facile and Cost-Effective Method to Prepare a Robust Superhydrophobic RTV Silicone Coating

A facile and cost-effective layer-by-layer assembly method is reported for the fabrication of a superhydrophobic coating using room temperature vulcanized silicone rubber and silica particles of different diameters. The superhydrophobic coating shows a contact angle of 154.6° and a rolling angle of 9°. The coating exhibits excellent self-cleaning properties and corrosion resistance with good softness and mechanical durability. The sample maintains its good superhydrophobicity, even after a series of tests by knife scratching, cutting, and hammering. The fabrication method has great advantages in terms of efficiency, cost, simple procedure and conditions. Its wide application in different substrates and the use of environment-friendly materials are also beneficial to the large-scale production of the coating.

Surfactant-free syndiotactic polystyrene aerogel foams via Pickering emulsion

This work investigates fabrication of aerogel foams from syndiotactic polystyrene (sPS) using silica-based Pickering emulsion method. A large fraction of micrometer size voids (macrovoids) is created inside porous thermo-reversible sPS gels by dispersing water droplets without the use of surfactants before gelation of sPS solution. The method used in this work alleviates two critical concerns of surfactant-stabilized emulsion templating method, namely the sensitivity of emulsion stability to temperature and the difficulty of removing the surfactants from aerogel foams. Hydrophobic silica particles of diameter 50–70 nm are used to stabilize Pickering emulsion of micrometer size water droplets in emulsions of sPS solution in toluene at 110 °C. Emulsion stability shows weak dependence on temperature and on water volume fraction. The sPS chains form thermo-reversible gels when cooled to room temperature and lock the water droplets inside the gel. The aerogel foams, recovered via supercritical drying, show high porosity and coexisting macrovoids and macropores. The most probable macrovoid size varies in the range of 50–600 μm and is strongly dependent on water volume fraction. The silica particles are found localized on macrovoid surfaces.

Validation of a Homogeneous Incremental Centrifugal Liquid Sedimentation Method for Size Analysis of Silica (Nano)particles

Silica nanoparticles display many unique physicochemical properties that make them desirable for use in a wide variety of consumer products and composite materials. Accurately measuring the size of these nanoparticles is important for achieving the desired nanoscale functionality of the final product and for regulatory compliances. This study covers the validation of a centrifugal liquid sedimentation method for accurate measurement of the Stokes diameter of silica particles with a near-spherical shape and dimensions in the nanometer and sub-nanometer scale range. The validated method provided unbiased results in the range of 50 nm to 200 nm, with a lower limit of detection of ≤20 nm. The relative standard uncertainties for precision, quantified in terms of repeatability and day-to-day variation, ranged from 0.2% to 1.0% and from <0.1% to 0.5%, respectively. The standard uncertainty for trueness was assessed at 4.6%. Within its working range, the method was found robust with respect to the type of cuvette, light factor, operator, and for defining the meniscus of the sample suspension. Finally, a relative expanded measurement uncertainty of 10% confirmed the satisfactory performance of the method.

Design of sustainable lip gloss formulation with biosurfactants and silica particles.

The main objective of this study was to design a sustainable lip gloss from water-in-oil emulsions by understanding the rheology of combining biosurfactants (rhamnolipids and sophorolipids) with silica particles (Aerosil powders). The different parameters consisted of the silica particle diameter size, the concentration of the particles within the formulation, alongside the different types of biosurfactant and oils used. The experimental results could provide information on the formulation design of cosmetic emulsions such as lip products and foundations. One parameter was varied each time, while the rest were kept constant in order to determine their effect on the viscosity profile of the formulations. A traditional mechanical rheometer was used in order to measure the bulk viscosity profiles of the different formulations, over a wide range of shear stress applied. The larger silica particle diameter size indicated an increase in the viscosity of the formulations, as yield stress was also generated for the specific diameter of 14nm. It was also found that as the particle concentration increased, the viscosity increased as well. Rhamnolipids and sophorolipids indicated very similar behaviour, meaning that the biosurfactant acts as an emulsifier and does not impact the system's rheological behaviour. The replacement of silicone oil with other natural oils was only successful with canola, and castor oil, since jojoba, squalene and mineral oil were not stabilized. The lip gloss was designed by water-in-oil emulsions which were stabilized by biosurfactants and the rheology of the oil phase was enhanced by silica particles. The formulation rheology gave a stable emulsion, the shear-thinning effect ensured easy applicability, whereas the viscosity and elasticity provided nice hold on the lips.

Disposable Micropipette Tip for Purifying DNA Fragments

A novel functional micropipette tip for DNA purification, called DNAtip, is described based on a novel coating process. The functional layer is prepared by an internal coating with silica particles supported into a polyvinyl alcohol (PVA) film. The coating layer is stabilized by simultaneous radiation-induced crosslinking to avoid its dissolution. Three types of silica particles of different diameters: micron, sub-micron, and nano sizes are studied. In addition, pH of the coating solution and concentration of the silica particles were optimized. Tips coated with fumed silica showed the highest absorption capacity of a plasmid DNA with an acceptable purity. Different linear dsDNA fragments were used for evaluating the absorption capacity and size discrimination of fragments. The recovery in the range of 700 ng and 200 ng per tip was measured for dsDNA fragments in the range of 400 bp to 2 kbp and 50 bp to 500 bp respectively. DNA PCR fragments contaminated with BSA were successfully purified with sufficient quality to be sequenced or enzymatically digested. This disposable tip device, useful for plasmids or DNA fragments purification, is a novel lab-on-a-tip device, which can effectively improve automate genetic engineering procedures.

Laser induced graphene /ceramic membrane composite: Preparation and characterization

In this work, laser induced graphene (LIG) was successfully fabricated on microporous ceramic membranes. The surface area, morphology, and chemical characterizations were performed on the LIG layer. Water contact angle measurements showed the hydrophobicity of LIG. Pure water and solvents with different polarities were used to understand the solvent flux behavior of LIG membrane. The LIG membrane showed very high non-polar solvent fluxes and remarkably low water permeability, and thus, the transport through the LIG membrane is related to dipole moment and dielectric constant, represented by solvent polarity. The LIG membrane achieved 90% rejection for 255 nm diameter silica particles, suggesting the presence of submicron size connecting pore channels that dominate the transport mechanism.

Pore Diameter of Mesoporous Silica Modulates Oxidation of H2O2-Sensing Chromophore in a Porous Matrix.

Hydrogen peroxide (H2O2) is an attractive chemical because of its bleaching properties in paper and pulp industry and as a disinfectant in the food, water, and medical industries. However, it is important to monitor the residual H2O2 level after its usage and prevent any unintended health problems or chemical reactions. Most H2O2 sensors often utilize fluorophores or electrical circuitry that requires an additional irradiation or a digital display. To this end, this study presents a 3,3',5,5'-tetramethylbenzidine (TMB)/horseradish peroxidase (HRP)-loaded patch that alerts the presence of high H2O2 levels by generating a visible blue color. We hypothesized that water-insoluble TMB immobilized within mesoporous silica particles of proper pore diameter and structure would act as a colorimetric indicator through the H2O2-mediated oxidation within a cross-linked patch. We examined this hypothesis by immobilizing TMB molecules in mesoporous silica particles with 2 and 7 nm diameter cylindrical pores as well as on nonporous silica particles. Then, we loaded these TMB-silica particles and HRP in a porous alginate patch via sequential in situ cross-linking reaction and lyophilization. In the presence of 25-5000 μM H2O2, which simulate H2O2 concentrations found in residual disinfecting fluids, the patch loaded with TMB-mesoporous silica particles with 7 nm diameter pores generated a distinct blue color with varying intensities depending on the H2O2 concentration. The design principles demonstrated in this study should be applicable to a broad array of sensors to be integrated into a moldable, three-dimensional matrix.

Polymer-assisted shapeable synthesis of porous frameworks consisting of silica nanoparticles with mechanical property tuning

We report the shapeable synthesis of porous silica frameworks using polyacrylamide (PAAm) gel as an organic template and hydrolyzed silicon alkoxide as a silica source. Macroscopically shaped porous frameworks—such as plates, tablets and sheets—comprised of 20- to 40-nm diameter silica particles are obtained via PAAm–silica precursor gels. The mechanical properties (i.e., hardness and Young’s modulus) of the silica frameworks depend on the packing density and are controlled by changing the silica content in PAAm gels. Shapeable synthesis of porous silica frameworks was achieved in an aqueous system using polyacrylamide (PAAm) gel as an organic template and hydrolyzed silicon alkoxide as a silica source. Macroscopically shaped frameworks comprised of 10- to 50-nm diameter silica particles are obtained via PAAm–silica precursor gels. The mechanical properties of the silica frameworks depending on the packing density are controlled by changing the silica content in PAAm gels.

Creating innovative composite materials to enhance the kinetics of CO2 capture by hydroquinone clathrates

This study addresses both the preparation of a reactive medium composed of porous particles impregnated with hydroquinone (HQ), an organic compound capable of forming gas clathrates, and an evaluation of the kinetic performance of these composite materials for CO2 capture. Two types of porous silica particles of different sizes and pore diameters were tested. The porous particles were impregnated with HQ by a dry impregnation (DI) method in a fluidized bed, and by a wet impregnation (WI) method. The impregnation effectiveness of the two methods is discussed, and the reactivity of the composite materials formed in terms of CO2 capture and storage capacity is studied experimentally. The experimental results showed that the HQ adheres well on the silica without any chemical modification of the deposit’s structure. We demonstrated that the impregnation technique plays a very important role in the kinetics of CO2 capture. A series of experiments performed using a magnetic suspension balance at 3.0MPa and 323K showed that the silica-based impregnated particles reversibly capture and store CO2, and that the CO2 capture kinetics are significantly enhanced compared to the results obtained with pure powdered HQ. Finally, we demonstrated that CO2 capture is faster with dry-impregnated particles.

Deterioration process of the hybrid films during wear test — Polyacrylate emulsion modified by silica particles

The hybrid materials are widely used in various fields for excellent performance. However, there are few researches studying their failure process. In order to prepare the hybrid materials with better performance, the failure process needs to be well studied. Two kinds of silica/polyacrylate films are successfully prepared to study the effect of organic-inorganic interaction on performance. The average diameter of silica particles is measured to be around 342 nm by scanning electron microscope (SEM). Wear test demonstrates the hybrid film, which is obtained by grafting polyacrylate onto silica particles, possesses more excellent properties than the one filled directly with silica particles. The stronger interaction between organic and inorganic components leads to a better distribution of inorganic particles within the polymer matrix. In this work, a model is presented to illustrate the deterioration process of the hybrid films, which allows us to further understand the hybrid materials.

Shear thickening fluids using silica-halloysite nanotubes to improve the impact resistance of p-aramid fabrics

In this study, p-aramid (Kevlar) fabrics were impregnated with silica and silica-halloysite nanotube based shear thickening fluids to improve the impact resistance performance. Shear thickening fluids (STF) were synthesized using spherical silica particles of 100nm diameter. Two virgin STF were prepared using silica concentrations of 60% and 65% (w/w). Then, halloysite nanotube (Hal nanotube) compounded STF were synthesized by adding Hal nanotube of 0.05, 0.1, 0.2 and 0.5% (w/w) with the existing STF. Rheological study confirmed more intense shear thickening behavior in silica-Hal nanotube compounded STF. Impact resistance of p-aramid fabrics increased drastically after the impregnation with STF. Further improvement in impact resistance was observed after silica-Hal nanotube compounded STF impregnation.

In situ preparation and characterization of polyimide/silica composite hemispheres by inverse aqueous emulsion technique and sol-gel method

In this paper, micron-scale polyimide/nano-silica (PI/nano-SiO2) composite hemispheres were fabricated by employing inverse aqueous emulsion technique and sol-gel method. Homogeneous inverse emulsion was obtained through using the precursor solution as dispersed phase which contained poly(amic acid) ammonium salt (PAAS), tetraethyl orthosilicate (TEOS) and deionized water, liquid paraffin (LP) as continuous phase, and Span80 as surfactant. The PI/SiO2 hybrid hemispheres could be got by adding excess dehydrating agent into the emulsion. The Fourier transform infrared (FT-IR) results demonstrated that PAAS had been converted to polyimide (PI) after adding the dehydrating agent into the emulsion and that the success of the reaction between TEOS molecules. The research showed that the morphologies of PI/SiO2 hybrid hemispheres, compared with the pure PI hemispheres, were still hemispherical and did not change with the varied silica contents. The surfaces of these samples were without clear interface between the SiO2 particles and the polymer matrix. And, the SEM images of the hybrid hemispheres after hydrofluoric acid (HF) etching or high temperature calcination showed that the SiO2 particles were well dispersed in the organic component, and the diameter of silica particles was nano-scale. The EDX results of the spheres which were after etching in hydrofluoric acid solution or after calcination showed that some 99.98 % of the silica particles were removed and the success of the removal of the organic component, respectively. Furthermore, thermal gravimetric analysis (TGA) results showed that the thermal stability of PI hemispheres could be improved by incorporating the inorganic component.

Synthesis of Silica Particles with Precisely Tailored Diameter

A modified seeded growth process of silica particles with a continuous addition of tetraethyl orthosilicate (TEOS) was presented to control the diameter of silica particles. The diameter of particles was monitored by dynamic light scattering to control the addition of TEOS. The increase in the diameter of the silica particles with time and the addition of TEOS was investigated. The diameter of silica seeds increased from 193 nm to 446 nm in 4 h. The final diameter of silica particles was tailored within the range of ±5 nm to the target diameter. Silica particles with diameter of 446 nm were synthesized and assembled into photonic crystals with a pseudo band gap centered at just 1000 nm. The feasibility and practicability of this modified seeded growth process was verified.

Effect of Silica Particle Size on Macrophage Inflammatory Responses

Amorphous silica particles, such as nanoparticles (<100 nm diameter particles), are used in a wide variety of products, including pharmaceuticals, paints, cosmetics, and food. Nevertheless, the immunotoxicity of these particles and the relationship between silica particle size and pro-inflammatory activity are not fully understood. In this study, we addressed the relationship between the size of amorphous silica (particle dose, diameter, number, and surface area) and the inflammatory activity (macrophage phagocytosis, inflammasome activation, IL-1β secretion, cell death and lung inflammation). Irrespective of diameter size, silica particles were efficiently internalized by mouse bone marrow-derived macrophages via an actin cytoskeleton-dependent pathway, and induced caspase-1, but not caspase-11, activation. Of note, 30 nm-1000 nm diameter silica particles induced lysosomal destabilization, cell death, and IL-1β secretion at markedly higher levels than did 3000 nm-10000 nm silica particles. Consistent with in vitro results, intra-tracheal administration of 30 nm silica particles into mice caused more severe lung inflammation than that of 3000 nm silica particles, as assessed by measurement of pro-inflammatory cytokines and neutrophil infiltration in bronchoalveolar lavage fluid of mice, and by the micro-computed tomography analysis. Taken together, these results suggest that silica particle size impacts immune responses, with submicron amorphous silica particles inducing higher inflammatory responses than silica particles over 1000 nm in size, which is ascribed not only to their ability to induce caspase-1 activation but also to their cytotoxicity.

Thermal conductivity of heat treated mesoporous silica particles

The thermal conductivity of mesoporous silica particles prepared as fine powder and heat treated between 150 and 700°C has been studied. Mesostructured silica particles of 30nm diameter were synthesized through a derived sol–gel method in the presence of a cationic surfactant. The thermal conductivity was found to be ranged from 0.03 to 0.08Wm−1K−1 according to treatment and packing while the density, the porous volume and the specific surface area of materials varied between 350 and 700kg/m3, 0.01 and 1.21cm3/g, and 10 and 420m2/g, respectively. The analyses carried-out with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, manometric adsorption/desorption of nitrogen, Fourier transform infrared spectrometry and solid-state nuclear magnetic resonance of 29Si nucleus revealed that the thermal conductivity was modified in agreement with the structural changes subsequent to dehydration, decomposition of organic matter, loss of hydroxyl groups and sintering of silica particles.