Silica Coatings Research Articles

Effect of Sr, Mg and Fe substitution on the physico-chemical and biological properties of Si[sbnd]Ca[sbnd]P multilayer scaffolds

In this work, a new combination of ceramic materials is proposed for bone tissue engineering applications. Multilayer scaffolds consisting of a core composed mainly of calcium pyrophosphate and external coatings of silica and calcium doped with Fe3+, Sr2+ and Mg2+ were prepared. To study the influence of the arrangement of dopant ions in the external coatings, two different scaffolds were developed: scaffolds 3J consisting of a single external coating with 9mol% of Fe3+, Sr2+ and Mg2+ ions; and scaffolds 3S comprising three external coatings, each containing 3mol% of Fe3+, Sr2+ and Mg2+ ions. Scaffolds were physico-chemically characterized and evaluated for in vitro bioactivity and cellular response in the presence of MG-63 cells. The results showed that the core scaffold displayed no in vitro bioactivity or good cellular response, but served as a support for the external coatings given its mechanical resistance. The cell viability of scaffolds 3J and 3S increased more than 100% in relation to the core, and also improved cell proliferation and adhesion resulting in a dense layer of cells that covered the scaffolds’ entire surface. The arrangement of ions in the external coatings did not influence the cellular response, but determined the bioactivity rate.

Silica Coating of Ferromagnetic Iron Oxide Magnetic Nanoparticles Significantly Enhances Their Hyperthermia Performances for Efficiently Inducing Cancer Cells Death In Vitro.

Increasing the biocompatibility, cellular uptake, and magnetic heating performance of ferromagnetic iron-oxide magnetic nanoparticles (F-MNPs) is clearly required to efficiently induce apoptosis of cancer cells by magnetic hyperthermia (MH). Thus, F-MNPs were coated with silica layers of different thicknesses via a reverse microemulsion method, and their morphological, structural, and magnetic properties were evaluated by multiple techniques. The presence of a SiO2 layer significantly increased the colloidal stability of F-MNPs, which also enhanced their heating performance in water with almost 1000 W/gFe as compared to bare F-MNPs. The silica-coated F-MNPs exhibited biocompatibility of up to 250 μg/cm2 as assessed by Alamar Blues and Neutral Red assays on two cancer cell lines and one normal cell line. The cancer cells were found to internalize a higher quantity of silica-coated F-MNPs, in large endosomes, dispersed in the cytoplasm or inside lysosomes, and hence were more sensitive to in vitro MH treatment compared to the normal ones. Cellular death of more than 50% of the malignant cells was reached starting at a dose of 31.25 μg/cm2 and an amplitude of alternating magnetic field of 30 kA/m at 355 kHz.

Effect of Modified Silica Materials on Polyvinyl Chloride (PVC) Substrates to Obtain Transparent and Hydrophobic Hybrid Coatings

In this research, we report a simple and inexpensive way to prepare transparent and hydrophobic hybrid coatings through deposition of different silica materials on polyvinyl chloride (PVC) substrates. The silica materials were prepared using an acid-catalyzed sol–gel method at room temperature (25 ± 2 °C), using alkoxysilanes: tetraethoxysilane (TEOS), as the silica source, and ethoxydimethylvinylsilane (DMVES), triethoxyoctylsilane (OTES), and trimethoxyhexadecylsilane (HDTMES), as modifier agents. The obtained materials were characterized (either as powders or as thin films) by Fourier-transform infrared spectroscopy (FTIR), UV/Vis spectroscopy, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and water contact-angle measurements. UV/Vis spectra showed that the PVC substrate coated with the silica material containing TEOS/DMVES/OTES had a transmittance of about 90% in the wavelength range of 650–780 nm. The water contact angles increased from 83° for uncoated PVC substrate to ~94° for PVC substrates coated with the sol–gel silica materials. These PVC films with hybrid silica coatings can be used as the materials for outdoor applications, such as energy-generating solar panel window blinds or PVC clear Windmaster outdoor blinds.

Antibiofilm activity of nanosilver coatings against Staphylococcus aureus

Implant infections due to bacterial biofilms constitute a major healthcare challenge today. One way to address this clinical need is to modify the implant surface with an antimicrobial nanomaterial. Among such nanomaterials, nanosilver is arguably the most powerful one, due to its strong and broad antimicrobial activity. However, there is still a lack of understanding on how physicochemical characteristics of nanosilver coatings affect their antibiofilm activity. More specifically, the contributions of silver (Ag)+ ion-mediated vs. contact-based mechanisms to the observed antimicrobial activity are yet to be elucidated. To address this knowledge gap, we produce here nanosilver coatings on substrates by flame aerosol direct deposition that allows for facile control of the coating composition and Ag particle size. We systematically study the effect of (i) nanosilver content in composite Ag silica (SiO2) coatings from 0 (pure SiO2) up to 50 wt%, (ii) the Ag particle size and (iii) the coating thickness on the antibiofilm activity against Staphylococcus aureus (S. aureus), a clinically-relevant pathogen often present on the surface of surgically-installed implants. We show that the Ag+ ion concentration in solution largely drives the observed antibiofilm effect independently of Ag size and coating thickness. Furthermore, co-incubation of both pure SiO2 and nanosilver coatings in the same well also reveals that the antibiofilm effect stems predominantly from the released Ag+ ions, which is especially pronounced for coatings featuring the smallest Ag particle sizes, rather than direct bacterial contact inhibition. We also examine the biocompatibility of the developed nanosilver coatings in terms of pre-osteoblastic cell viability and proliferation, comparing it to that of pure SiO2. This study lays the foundation for the rational design of nanosilver-based antibiofilm implant coatings.

Anticorrosion and Cytocompatibility Assessment of Graphene-Doped Hybrid Silica and Plasma Electrolytic Oxidation Coatings for Biomedical Applications.

Magnesium AZ31 alloy substrates were coated with different coatings, including sol–gel silica-reinforced with graphene nanoplatelets, sol–gel silica, plasma electrolytic oxidation (PEO), and combinations of them, to improve cytocompatibility and control the corrosion rate. Electrochemical corrosion tests, as well as hydrogen evolution tests, were carried out using Hanks’ solution as the electrolyte to assess the anticorrosion behavior of the different coating systems in a simulated body fluid. Preliminary cytocompatibility assessment of the different coating systems was carried out by measuring the metabolic activity, deoxyribonucleic acid quantification, and the cell growth of premyoblastic C2C12-GFP cell cultures on the surface of the different coating systems. Anticorrosion behavior and cytocompatibility were improved with the application of the different coating systems. The use of combined PEO + SG and PEO + SG/GNP coatings significantly decreased the degradation of the specimens. The monolayer sol–gel coatings, with and without GNPs, presented the best cytocompatibility improvement.

Method for High-Yield Hydrothermal Growth of Silica Shells on Nanoparticles.

Coating processes are commonly used in materials science to protect a core or modify material properties. We describe a hydrothermal coating process using TEOS (tetraethyl orthosilicate), a widely used precursor for silica coatings, on three representative template materials (carbon nanotubes, silica, and polystyrene nanoparticles) with different properties and shapes. We compare the efficiency of previously published protocols for silica coatings at room temperature and atmospheric pressure with the hydrothermal process at 160 °C and 3 bar. The hydrothermal method achieves higher yields and thicker silica coatings with the same amount of precursor when compared to the conventional way, thus offering higher effectiveness. Furthermore, the hydrothermal coating process yields more homogeneous shells with a higher density, making hydrothermal coating the method of choice when mechanical integrity and low permeability of the coating are required.

Rapid Microwave-Assisted Synthesis of Organo-Modified Nanostructured Silica Coatings with Tunable Water-Repellence Properties

A simple method to fabricate organo-modified silane coatings for water-repellent surface modification was proposed, by using a microwave sol-gel synthesis of hybrid materials. Low-cost fluorine-free tetraethoxysilane (TEOS) and dodecyltriethoxysilane (DDTES) were used as silane derivatives. The organo-modified silica coatings were prepared by the drop-casting method and were characterized by UV-VIS, FTIR spectroscopy, and AFM and SEM microscopy. The morphology of the film show the existence of submicrometer scale roughness due to the aggregation of modified silica nanoparticles. Contact angles of water and diiodomethane on surfaces modified with as prepared nanostructured film were determined in order to assess the hydrophobic and oleophobic properties. The TEOS/DDTES ratio was proved to be a crucial factor in tuning the wettability properties. The results suggest that significant increase of hydrophobicity could be achieved by using non-fluorinated cost-effective silica nanomaterials produced with a rapid ecofriendly method.

Plasma-assisted template removal and consolidation of silica coatings on polycarbonate

This paper presents a fast and efficient method of removing the template from silica thin films on polycarbonate. Radiofrequency-generated oxygen plasma induced the decomposition of the non-ionic surfactant. The reference samples were silica coatings on silicon, which had different pore sizes. We removed the surfactant by solvent extraction and calcination from these samples. Grazing incidence angle X-ray diffraction analysis shows a highly ordered arrangement of mesopores. The formation of the face-centred cubic structure of mesopores is independent of the substrate and the template removal method. Atomic force microscopy analysis showed open-pore channels after oxygen plasma etching. It also proved that the ammonia treatment increases the hardness of the layer. A short air-plasma treatment is effective for the consolidation of the silica layer and improves the abrasion resistance of the layer on polycarbonate. Air plasma treatment is an alternative to the long heat treatment process. We performed environmental tests according to the relevant ISO standards for optical coatings. Air plasma treated silica coatings have passed all the weathering tests. Therefore, it can be used in outdoor applications, such as a protective layer for the plastic cover of LED street lights. These thin films on polycarbonate have at least one year of service life and are weather-resistant. Plasma treatment can consolidate the silica network and the thin films on polycarbonate have high light transmission (T = 98.8 %).

Super-Hydrophobic Nanostructured Silica Coating on Aluminum Substrate for Moist Air Condensation

Super-Hydrophobic Nanostructured Silica Coating on Aluminum Substrate for Moist Air Condensation

The Influence of Organically Modified Derivatives of Silica on the Structure and the Wetting Angle Values of Silica Coatings

The surrounding environment often acts in a destructive way on materials we apply in our everyday life. The best way to protect them against such activity is to cover the basic materials with coatings possessing different properties, tailored to their applications. Anticorrosive layers are one of the biggest groups of such protective coatings, especially those containing silica or its derivatives. Depending on a type of silica precursor and a method of deposition, one can obtain coatings of different structures and properties. In this work, three different silica precursors were applied: TEOS (tetraethylorthosilane), DDS (dimethyldiethoxysilane) and AerosilTM (the powder silica). Sols of different concentrations of the aforementioned precursors as well as commercially available preparations (Sarsil H1 4/2 and SILOXAN W290) were applied for thin films deposition by a dip coating or an infiltration method. The substrates could be divided in two groups: metallic (steel and titanium or titanium alloys) and porous (represented by old brick, sandstone and limestone). Following the deposition process, the layers on metallic substrates were additionally annealed at 500 °C to improve their adhesion and mechanical properties, while those on porous materials were dried in air. All prepared coatings were primarily studied by FTIR spectroscopy and X-ray diffraction. The morphology of their surfaces was imaged by SEM and AFM microscopies, which also allowed determination of the roughness of obtained materials. The measurements of wetting angle values enabled to find the relationship between the surface topography, the type of silica precursor and the hydrophobic/hydrophilic properties of the samples. The results confirmed the hydrophobic properties of coatings obtained by the infiltration technique on the porous materials and the high hydrophilicity of the annealed thin film deposited on the metallic substrates.

Fabrication of New Multifunctional Cotton/Lycra Composites Protective Textiles through Deposition of Nano Silica Coating.

This study aims to develop multifunctional pile cotton fabrics by implementing different compositions of lycra yarns with different densities of the cotton fabric under study. Highly dispersed silica nanoparticles (SiO2 NPs) with small sizes—in the range of 10–40 nm—were successfully prepared and were analyzed using scanning electron microscopy (SEM). The particle size distribution of nano silica was determined via dynamic laser scattering (DLS) and measurements of its zeta potential. Cotton/lycra fabrics were treated using prepared SiO2 NPs in presence of ethylenediaminetetraacetic acid (EDTA) as a crosslinking agent. Energy dispersive X-ray (EDX) analysis and scanning electron microscopy (SEM) were used to characterize the nano-treated fabrics and assure homogeneous dispersion of SiO2 NPs on the cotton/lycra composites. Additionally, the nanoparticles were screened for their in vitro antibacterial activity against human pathogens such as Gram-positive Staphylococcus aureus and Bacillus cereus and Gram-negative Escherichia coli and Pseudomonas aeruginosa strains. The functional properties of the new composite pile cotton fabrics include excellent antibacterial, highly self-cleaning, and excellent UV protection factor (UPF) properties.

A high value utilization process for coal gasification slag: Preparation of high modulus sodium silicate by mechano-chemical synergistic activation

Coal gasification coarse slag (CGCS) is solid waste generated during coal gasification. The mainly treatment method of CGCS is storage and landfill, which causes severe environmental pollution and waste of land resources. Sodium silicate can be synthesized using CGCS after impurities are removed for the high content of amorphous silica. In this work, a novel method of acid activation depolymerization–dilute alkali dissociation is proposed to synthesize high-modulus, low-impurity sodium silicate using CGCS under mild conditions. In the acid activation depolymerization process, the content of impurities such as CaO and Fe2O3 can be reduced from over 30% to below 3%. SiO2 composition can be enriched from 35.75% to 60.60%. The SiOAl bond is broken, the coordination structures of Q4(2Al) and Q4(3Al) are depolymerized, and the reactive Q4(0Al) and Q3(0Al) coordination structures of amorphous silica are formed. Numerous defects appear in the aluminosilicate structure, exposing a large number of active SiOH bonds. Efficient desilicated ratio is increased from 7.59% to 73.45%. During the process of dilute alkali dissociation, a large number of reactive SiOSi bonds with network structure defects are broken with the destruction of hydroxyl groups, while SiO and SiOH bonds are formed. Amorphous silica is leached into the liquid phase in the form of oligomers, and high-modulus sodium silicate can be obtained. Under optimal conditions, the removal ratio of amorphous silica and modulus of sodium silicate can reach 80% and 3.53, respectively. The synthesized sodium silicate can be used to produce hydrated silica, adhesives and surface coatings. This process not only reduces pollution, but also alleviates the shortage of high-purity quartz sand resources and promotes the clean development of coal chemical enterprises.

Applying Softener Doped Silica Coating to Cotton Denim Fabrics

ABSTRACT Present study, the surface of cotton denim fabrics which are one of the most used products in daily life was modified with silica coatings prepared with sol-gel technique. Cationic and nonionic softeners were used as additives to silica-based sols prepared separately in acidic and alkaline conditions. Characterization test results showed that coating could be obtained on fiber surfaces with the all applied treatments. The rigidity of the fabric caused by silica sols can be reduced slightly by adding both cationic and nonionic softeners. The applied coating processes slightly increased the air permeability. It was concluded that decreasing the rigidity of the silica coatings could improve the abrasion and tear strength of the denim fabrics to a certain level.

Improved Solvothermal Synthesis of γ-Fe2O3 Magnetic Nanoparticles for SiO2 Coating.

Monodisperse magnetic γ-Fe2O3 nanoparticles (MNPs) were prepared by a simple, improved, one-pot solvothermal synthesis using SDS and PEG 6000 as double capping reagents. This double protecting layer afforded better MNP uniformity (Z average 257 ± 11.12 nm, PDI = 0.18) and colloidal stability. Materials were characterized by DLS, SEM, TEM, XPS, and XRD. The use of these MNPs in the synthesis of core–shell structures with uniform and tunable silica coatings was demonstrated, as silica coated MNPs are important for use in a range of applications, including magnetic separation and catalysis and as platforms for templated nanogel synthesis.

One pot synthesis of luminescent Mn doped ZnSe nanoparticles and its silica based water dispersible formulation for targeted delivery of doxorubicin

The manganese doped zinc selenide nanoparticles (ZnSe:Mn NPs) were synthesized by thermolysis method using oleic acid and oleylamine as a capping agent, 1-octadecene as solvent. Coating of mesoporous silica was done on ZnSe:Mn (ZnSe:Mn@mSilica) which was further functionalized with amine functional groups by treating with (3-aminopropyl)trimethoxysilane. Further pegylation was done to achieve water dispersibility by conjugating carboxyl groups of poly(ethylene glycol) diacid with the amine groups. These pegylated NPs were subsequently treated with ethylenediamine followed by acrylic acid. Conjugation of tris-(hydroxymethyl-aminomethan) was performed by Michael-type addition reaction to afford ZnSe:Mn@mSilica-PEG-Tris-OH. These TRIS functionalized NPs exhibited broad emission ranging from 590-620 nm that is an indicative for their suitability in diagnosis and monitoring progress of cancer treatment. To explore the usefulness of increased surface area because of mesoporosity, doxorubicin was loaded on ZnSe:Mn@mSilica-PEG-Tris-OH NPs through silyl ether linkage and evaluated for cytotoxicity against WEHI-164 mouse fibrosarcoma and RAJI human hematopoietic origin cancer cell lines. A decrease in 12 % of cell viability of WEHI-164 cells while 30% decrease in RAJI cell lines (IC 50 ≈ 45 nM) were observed. This shows that our formulation has more cytotoxic in RAJI cancer cell lines than that of WEHI-164 cancer cells. These results revealed that the formulation has potential for the application in drug delivery and diagnosis in chemotherapeutics.

Ammonia-vapour-induced two-layer transformation of mesoporous silica coatings on various substrates

We prepared mesoporous silica layers by sol-gel dip-coating technique on various substrates (silicon, polycarbonate, microscope glass and quartz) with the aid of a pore-forming triblock copolymer (Pluronic PE10500). The freshly deposited layers were aged in an aqueous ammonia solution atmosphere. Two types of thermal curing were implemented depending on the substrates: a low-temperature heat treatment at 120 °C for 13 hours or a high-temperature heat treatment at 480 °C for 1 hour. We carried out the porogen extraction of the copolymer molecules from the low-temperature heat-treated samples in a water washing step.Optical spectroscopy measurements gave evidence of a significantly improved and long-lasting light transmission of coatings. The maximum light transmission was 98.3% on glass and 97.6% on polycarbonate after 4 years of storage. TEM investigations showed thin layers with distorted face centred cubic structure.Spectroscopic ellipsometry and ellipsometric porosimetry studies showed a “two-layer” structure. The applied synthesis technique promoted the formation of a double layer structure with relatively thick (10–25 nm) pore sizes. The pseudomorphic transformation rearranged the silica/copolymer structure in presence of ammonia. The transformation was incomplete and resulted in a low porosity (23–34%) upper-layer and a high porosity (40–76%) lower-layer.

Effect of Ce(III) and Ce(IV) ions on the structure and active protection of PMMA-silica coatings on AA7075 alloy

This work investigates the effect of Ce(III) and Ce(IV) additives on the structure and anti-corrosion properties of poly(methyl methacrylate) (PMMA)-silica coatings on AA7075 aluminium alloy. The results revealed that intermediate Ce(IV) loadings (500 and 1000 ppm) result in a dense hybrid network with a less defective polymeric phase, extending the service time of AA7075 up to 835 days in 3.5% NaCl. Although both additives provide long-term protection, the self-healing ability was observed only for Ce(IV) addition, favoured by the formation of oxides/hydroxides at pH∼3. These properties make the 4 μm-thick PMMA-silica-Ce(IV) coatings very interesting for chromium-free protection technologies.

Numerical Analysis of Silica Coating Effect on Pt Cathode Catalyst in Polymer Electrolyte Fuel Cells

In order to accelerate the development of polymer electrolyte fuel cells (PEFCs), it is important to optimize the structure of catalyst layers (CLs) including Pt particles, ionomer loading, and porosity, resulting in the improvement of performance. Numerical analysis can assist in designing the optimized CLs without trial and error. In this study, the effects of silica-coated Pt catalysts (SiO2/Pt/C) were investigated by experimental measurements and numerical analysis in order to obtain manufacturing guidelines by designing optimized CLs for PEFCs. In the experimental results, the SiO2/Pt/C showed lower performance than non-coated Pt catalysts (Pt/C) under relative humidity (RH) of 80% at 80°C. In the case of the SiO2/Pt/C, the addition of two parameters including the enhancement of proton conductivity and an increase in the oxygen diffusion resistance in the CLs, attributed to silica layers, were considered. The distribution of current density at 0.8 A cm−2 of the SiO2/Pt/C at each humidity condition (100%RH, 80%RH, 60%RH, 40%RH) is more homogeneous and reached closer to the gas diffusion layer compared to those of the Pt/C. The result indicates that it is possible to improve durability by increasing the reaction located near the polymer electrolyte membrane. For both catalysts, the overvoltages at 0.8 A cm−2 were similar to each other, except for that of proton resistance in ionomer and oxygen diffusion in the ionomer.

Coating of colloidal silica on glass surfaces with bbk nano silica as raw material

Due to the colloidal silica has many applications such as coating, a catalyst precursor, a nano-size filler, investment casting, semiconductor wafer polishing, and an inorganic binder, it still attracting to be studied. The colloidal silica layer has been coated on a glass substrate using the spray-coating process. Two kinds of colloidal silica were prepared, i.e., the colloidal silica formed by mixing of nano-silica from Balai Besar Keramik (BKK) and the silane hexamethyldisilazane (HMDS), and the colloidal silica polishing Mastermet (0.06 mm) commercial as a comparison. The HMDS percent was varied at 10, 20, and 30 vol.%. The contact angle measurement obtained the hydrophobic properties of the samples, and a UV-Vis spectrophotometer measured the transmittance samples. A water contact angle of 94.9° is achieved at 10% HMDS. For all samples, the transmittance of the before and after coated glass substrate can reach an average of 89% to 90%. From this study, it is concluded that the BBK nano-silica has met the commercial requirements that are the hydrophobic property in the contact angle and the transmittance.

Real-time monitoring of airborne molecular contamination on antireflection silica coatings using surface acoustic wave technology

Real time monitoring of contamination on antireflection (AR) silica coatings in high peak power laser systems (HPLs) is critically needed in order to avoid reductions of transmission and laser damage to optical surfaces. Herein we proposed to apply a surface acoustic wave (SAW) sensor to real-time monitor trace amounts of airborne molecular contaminants (AMCs) adsorbed on the AR silica coatings. The silica coating is found to be susceptible to AMCs because of its mesoporous structure, huge surface area and polar nature. The adsorbed AMCs caused the increased mass on the silica coating of the SAW sensor, which resulted in a significant increase of its frequency shift. The fabricated sensor showed a high sensitivity of ∼-490 mm2 ng−1Hz and an excellent linearity vs. the areal density of adsorbed AMCs since the frequency shift of the sensor is linearly related to the change of mass of the silica coating.