Layer Of Silica Particles Research Articles

Preparation and characterization of anti-stain self-cleaning coating on ceramic

The sedimentation of various pollution on the ceramic surfaces decreases their apparent quality and increases their contaminating effect. While self-cleaning coatings help to solve this problem. In this research, two layers of silica particles with different particle sizes and one layer of perfluorodecyltriethoxysilane are deposited on ceramic surfaces in a micro/nano setting to impose a hierarchical structure and low surface free energy resulting in a self-cleaning characteristic. Different settings of layers and concentration of the main constituents are applied and the samples are analyzed by dynamic light scattering (DLS), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analyses as well as contact angle measurement tests. The highest static contact angle and the lowest sliding angle of water drop on the coated surface are 116° and 19°, respectively. Also, the static contact angle of water on the coated ceramics exceeds to 100° after immersion in the water for two days and the coated surfaces show improved resistance against stains. Moreover, the experimental results are statistically analyzed and numerically optimized.

Increasing chemisorbed silane coupling agents in surface‐treated layer of silica particles

AbstractIn the surface treated inorganic particles with silane coupling agent (SCA), chemisorbed and physisorbed molecules are present in the treated layer. Increasing the amount of chemisorption by increasing the molecular weight of SCAs was investigated. Oligomers formed via self‐condensation during storage more than 10 days at room temperature for 3‐methacryloxypropyltrimethoxysilane‐treated silica particles. Monomeric SCA evaporates easily by heating. The oligomers restrict evaporation, and heating increases the chemisorption. The influence of molecular weight of SCA was investigated. In the case of amino group, the amount of chemisorbed was greater for aminoethylaminooctyltrimethoxysilane with high molecular weight than for 3‐aminopropyltriethoxysilane. For SCAs with hydrocarbon chains, the amount of chemisorption was lower for both low molecular weight molecules and decyltrimethoxysilane (D) with a high molecular weight. For fluorocarbon chains, the amount of chemisorption was lower for low molecular weight molecules, whereas it increased significantly by heating for high molecular weight type of 1H,1H,2H,2H‐heptadecafluorodecyltriethoxysilane (F). Wide‐angle X‐ray diffraction analysis of F‐treated silica particles showed that the fluorocarbon chains formed an ordered structure. There was no such indication for the D‐treated system. This ordered structure seems to influence on higher chemisorption for F‐treated systems.

Abstract P-34: Cryo-EM Study of Submicrocapsules with a Shell of Nanoparticle Heteroaggregates and Polyelectrolyte Layers

Background: Currently, different approaches of active and passive targeted drug delivery are being developed. One of the most promising methods of targeted drug delivery is the use of capsules. For instance, colloidosomes—capsules consisting of the shell formed by colloidal particles at the interface of the emulsion—can be used for targeted delivery of antitumor drugs or any other drugs in liquid form. Here we present results of cryo-EM study of submicrocapsules with the soybean oil core and with the shell consisting of SiO2 nanoparticles and detonation nanodiamonds (DNDs) stabilized with chitosan and alginate. Methods: Сryo-electron tomography (Cryo-ET) was used to identify the morphological features of the submicrocapsules. Preliminary screening of samples and cryo-ET data collection were performed using Titan Krios cryo-EM (ThermoFisher Scientific, US) equipped with Falcon 2 direct electron detector. The restoration of the tomographic series was carried out using IMOD software. Eman2 was used for segmentation and UCSF Chimera was used for visualization of the 3D model. Submicron capsules were obtained by stabilizing oil droplets with a mixture of SiO2 nanoparticles and DNDs. To form a stable shell, an additional layer of silica particles and polyelectrolyte layers of alginate/chitosan were applied to the droplets of the dispersed phase of the emulsion by physical adsorption. Results: Cryo-EM data showed the presence of submicrocapsules with a diameter in the range of 200-900 nm. Although a significant fraction of submicrocapsules was found to be partially destroyed, results of cryo-ET study of intact capsules demonstrated that silicon dioxide nanoparticles form a net, while DNDs form clusters. Conclusion: Here we demonstrate the results of the study of submicron capsules with a shell of silica nanoparticles and DNDs. It was found that a uniform distribution of DNDs is not a prerequisite for the creation of submicron capsules that contradicts the theoretical model.

Multistate and On-Demand Smart Windows.

Composite films consisting of wrinkles on top of the elastomeric poly(dimethylsiloxane) film and a thin layer of silica particles embedded at the bottom is prepared as on-demand mechanoresponsive smart windows. By carefully varying the wrinkle geometry, silica particle size, and stretching strain, different initial optical states and a large degree of optical transmittance change in the visible to near infrared range with a relatively small strain (as small as 10%) is achieved. The 10% pre-strain sample has shallow wrinkles with a low amplitude and shows moderate transmittance (60.5%) initially and the highest transmittance of 86.4% at 550 nm when stretched at the pre-strain level. Stretching beyond the pre-strain level leads to a drastic decrease of the transmittance at 550 nm, 39.7% and 70.8% with an additional 10% and 30% strain, respectively. The large drop of optical transmittance is the result of combined effects from the formation of secondary wrinkles and nanovoids generated around the particles. The 20% pre-strain sample has wrinkles with a moderate amplitude, showing 36.9% transmittance in the initial state, and the highest transmittance of 71.5% at 550 nm when stretched to the pre-strain level. Further stretching leads to increased opacity similar to that seen from the 10% pre-strain sample.

Synthesis of polystyrene coated by sand (PCS) as a novel media in modified biological aerated filters (BAF) for advanced municipal wastewater treatment: a comparative assessment

In this study a novel media, polystyrene coated by sand (PCS) was made and then applied in a -pilot-scale down-flow biological aerated filter (BAF), named PCS BAF. The efficiency of PCS BAF reactor was compared with efficiencies of puzzolana BAF, gravel BAF, and polystyrene BAF in advanced domestic wastewater treatment through three stages. The inner structure of BAFs consisted of a media with a height of 150 cm for biological attached growth that was modified by a 20 cm layer of silica particles at the bottom of columns to increase the reactors' performance. The physical and chemical parameters of turbidity, BOD5, TCOD, and SCOD, as well as parameters related to backwashing were investigated for BAFs' efficiency. Results of this research indicated that PCS BAF can decrease the turbidity, BOD5, TCOD, and SCOD in the influent, from 20 NTU, 22, 53, and 36 mg/L, to a rate of 1.3 NTU, 9, 26, and 21 mg/L in the effluent, respectively. Moreover, the backwashing time required for PCS BAF was less than half of the other three BAF reactors and the backwashing interval was about once every 19 d.

Effects of Colloidal Crystals, Antibiotics, and Surface-Bound Antimicrobials on Pseudomonas aeruginosa Surface Density

We examined the effect of a crystalline layer of silica particles in the size range 0.5-4 μm on the adsorption and surface growth of Pseudomonas aeruginosa. Growth on these colloidal crystal monolayers (CCMs) was compared to growth on a flat plate of silica. All surfaces were coated with a thin film of silica to provide chemical uniformity of the different topographies. The results showed that the CCM reduces the density of colony forming units (CFU) on the solid by 99-99.9% when the suspension load was 103 CFU. We also examined the interaction between the CCM and either antibiotics or a chemically bound antimicrobial. The addition of 20 μg/mL tobramycin after an initial 24 h growth period caused a further decrease in CFU counts of about 99-99.9% for all topographies. The percentage reduction as a result of the antibiotics was similar for all topographies, which suggested that there was no particular synergy between the topography and antibiotics. On the other hand, the additive nature of the two effects suggested promise for clinical studies: the large percentage reduction in CFU density on addition of the antibiotic to a flat surface was maintained on the topography, even starting from a much lower CFU density. A similar result was obtained for the combination of CCM and a covalently bound layer of antimicrobial poly(allylamine hydrochloride) (PAH). The PAH reduced the CFU, and the CCM caused a further reduction; the two factors behaved approximately independently. Overall the CCM was found to be very effective at reducing the density of adsorbed P. aeruginosa both with and without the additional reductions caused by antibiotics or surface-bound antimicrobials.

An analytical evaluation of historic glazed tiles from Makli and Lahore, Pakistan

The composition and production of pre-modern glazed tiles in Pakistan are not well understood. Here, 38 glazed tile samples sourced from various monuments at Makli Hill and Lahore Fort in Pakistan, dating mainly from the sixteenth and seventeenth centuries CE, were investigated with scanning electron microscopy and energy dispersive X-ray spectrometry for a comprehensive technological study to understand the methods used in their production. The analyses were supplemented by laser ablation-inductively coupled plasma-mass spectrometry to more fully characterise the raw materials used for the glazes. The Makli tile bodies are composed of clay-based ceramic whereas those from Lahore are stonepaste. Both are coated with soda-lime-silica glazes made using plant ash. Cobalt, copper, lead‑tin yellow and lead‑tin orange are identified as the glaze colorants. White glazes do not have an added opacifier or colorant, but are white due to the presence of an underlying layer of silica particles. Technological variations between the Makli and Lahore tiles are highlighted in the discussions, the former found to resemble traditional kashi ware of Sindh-Multan in their make-up, while the latter matches Mughal tile-work that prevailed for a while locally in the seventeenth century.

A silica coated paper substrate: development and its application in paper spray mass spectrometry for rapid analysis of pesticides in milk.

A novel silica coated paper substrate is developed through a facile vacuum filtration method by using the commercially available silica particles as the coating material and corn starch as the adhesive agent. Unlike the commercial silica coated paper (namely grade SG81 paper), the resulting paper substrate was covered by a layer of silica particles on the top side of the paper, and no cellulosic fibers were exposed at its surface. After loading a solution sample on its surface, the coated silica particles allowed the target analytes to remain at the top side rather than penetration through the substrate. Owing to this effect and the special interactions with analytes, the as-prepared silica coated paper demonstrated superior performance in the analysis of different pesticides in milk using paper spray mass spectrometry to the uncoated filter paper and grade SG81 paper. Compared to the other two papers, paper spray analysis using the as-prepared paper improved the estimated lower limit of quantitation of seven pesticides (alachlor, acetochlor, pretilachlor, butachlor, metolachlor, napropamid and benzeneacetamide) in milk by a factor of 2 to 19-fold depending on the pesticide. This study offers a novel paper substrate for paper spray in high sensitivity analysis of target analytes in a complex foodstuff matrix without any pretreatment.

Preparation of Dually, pH- and Thermo-Responsive Nanocapsules in Inverse Miniemulsion

pH- and thermo-sensitive nanocapsules were successfully synthesized via inverse miniemulsion copolymerization of N-isopropyl acrylamide (NIPAM), N,N'-methylene bisacrylamide (MBA), and a functional monomer, 4-vinyl pyridine (4-VP). The size and size distribution of nanocapsules were measured by dynamic light scattering (DLS). The particle morphology was observed by transmission electron microscopy (TEM). The final morphology of particles was strongly influenced by the hydrophobicity of functional monomers. The use of a hydrophilic functional monomer, acrylic acid, led to the formation of solid particles, while the use of the more hydrophobic functional monomer, 4-VP, resulted in the formation of nanocapsules. The particle morphology, size, and size distribution were investigated in terms of the content of 4-VP, MBA, and the type and content of surfactant. The pH- and thermo-sensitivities were characterized by measuring the size variation with the change of temperature and pH. The organic-inorganic nanocapsules were prepared by coating a layer of silica particles on the surface of the sensitive nanocapsules.

Pitting Corrosion of Silica-Coated Type 304 Stainless Steel Under Thin Electrolyte Layers

Abstract The pitting corrosion behavior of Type 304 (UNS S30400) stainless steel (SS) under an electrolyte droplet with a layer of silica particles on the surface was investigated using a Kelvin probe. Droplets of 2.5 M magnesium chloride (MgCl2) solution were placed on an electrophoretically silica-coated steel surface and exposed to a constant low relative humidity. As a result of water evaporation, the chloride concentration increased and pitting corrosion initiated, which was detected by a sudden drop in open-circuit potential. Metastable pits repassivated slower under the silica particle layer than on bare stainless steel. Pits on silica-coated Type 304 SS initiated within a narrow chloride concentration and time range unlike pits on bare Type 304 SS. Pit growth rate was not influenced by the silica layer, but the particles acted as diffusion barrier. A mechanism for pit growth under a layer of inert particles was proposed.

Superoleophobic Cotton Textiles

Common cotton textiles are hydrophilic and oleophilic in nature. Superhydrophobic cotton textiles have the potential to be used as self-cleaning fabrics, but they typically are not super oil-repellent. Poor oil repellency may easily compromise the self-cleaning property of these fabrics. Here, we report on the preparation of superoleophobic cotton textiles based on a multilength-scale structure, as demonstrated by a high hexadecane contact angle (153 degrees for 5 microL droplets) and low roll-off angle (9 degrees for 20 microL droplets). The multilength-scale roughness was based on the woven structure, with additional two layers of silica particles (microparticles and nanoparticles, respectively) covalently bonded to the fiber. Superoleophobicity was successfully obtained by incorporating perfluoroalkyl groups onto the surface of the modified cotton. It proved to be essential to add the nanoparticle layer in achieving superoleophobicity, especially in terms of low roll-off angles for hexadecane.

Engineered Multilayer Colloidal Crystals with Tunable Optical Properties

Multilayer colloidal crystals with a perfectly defined architecture have been fabricated by the successive depositions of layers of silica particles with various diameters onto a substrate. The composite materials have been characterized by scanning electron microscopy (SEM) and near-infrared (NIR) spectroscopy. Our results establish that the optical properties of these multilayer systems can be tailored by adjusting either the thickness or the stacking order of each component crystal. The versatility of our approach has been further exploited to fabricate a multilayer colloidal crystal consisting of many alternating layers of two different spheres sizes.

Mixed Colloidal Dispersions of Silica and Hematite

Abstract The colloidal behavior of mixed dispersions containing hematite (diameter=138.9 nm) and silica (diameter=7.0 nm) has been studied by measuring the stability ratio, zeta potential, and particle size. When various particle numbers of silica were added to a constant particle number of hematite, different colloidal behavior was observed, depending on the pH. In a pH region where the two solids were oppositely charged, hematite particles showed a dispersion-coagulation-redispersion process with increasing particle number of silica, resulting in a coating layer of silica particles on the hematite surface. On the other hand, in a region where both solids were negative, the addition of silica enhanced the stability of the hematite.