Search Results (50)

A new approach to the synthesis of a nanosized and hierarchical titanosilicate, TS-1, is presented. Instead of using specific solid or additional mesoporous templates or individual additives to slow down the hydrolysis of titanium alkoxides, it is proposed that the titanosilicate TS-1 can be obtained from gels synthesized with hydrolysis catalysts (HNO₃ and tetrapropylammonium hydroxide). When nitric acid catalyzes tetraethyl orthosilicate (TEOS) hydrolysis, the resulting crystalline TS-1 that can be obtained has uniform particle sizes (150–180 nm), is anatase-free, and contains up to 46–67% of mesopores. When a base catalyst is applied, the obtained material’s features are opposite. Moreover, acid-promoted TS-1 samples catalyze cyclohexene H₂O₂-oxidation via a heterolytic route to the cyclohexane epoxide with 67% selectivity, which is non-typical. Full article

The development of a silane coupling agent with an aminopropyl structure as a nucleating agent for poly(ethylene terephthalate) (PET) is reported in this study. The tri–block oligomers nucleating agent was formed by 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane/oxalic acid/low molecular weight PET (LPOBD). It was subsequently cross-linked with tetraethyl orthosilicate to form LPOBD-T. Composites of LPOBD/PET and LPOBD-T/PET were prepared by melt blending, and their thermal and crystallization behaviors were analyzed using XRD, DSC, TG, and POM. The results indicated that not only did the triblock polymer nucleating agent LPOBD exhibit a strong nucleation effect, but the crosslinked LPOBD-T also demonstrated superior crystallization performance. Specifically, the crystallinity of the 1 wt% LPOBD-T/PET composite increased by 3.3%, the crystallization temperature rose by 21.1 °C, and the t_1/2 was reduced by 53 s. Moreover, the crystalline morphology was more uniform. These findings indicate that the tri-block oligomers synthesized from a silane coupling agent serve as effective nucleating agents for PET. Full article

Polydimethylsiloxane (PDMS) has been extensively employed in electrical insulation applications owing to its excellent thermal stability, hydrophobicity, and dielectric properties. However, its inherent mechanical limitations require structural reinforcement to enhance its performance under more demanding operational conditions. In this study, the mechanical, thermal, and surface properties of PDMS-SiO₂ nanocomposites synthesized via in situ sol–gel process was systematically investigated. The influence of different SiO₂ nanoparticle concentrations (5, 10, and 15 wt%), sol–gel catalyst type (acidic and alkaline), and tetraethyl orthosilicate (TEOS) crosslinking agent ratios (15:1, 10:1, 5:1) was evaluated. Tensile mechanical testing, dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA) revealed that the incorporation of SiO₂ notably improved both the mechanical strength and thermal stability of the composites. The 5-15b and 10-15a composites exhibited the highest tensile stress and viscoelastic modulus among all samples. Furthermore, the composites retained key functional properties, including hydrophobicity, high volumetric electrical resistivity (~10¹¹ Ω·cm), and strong adhesion. These findings confirm the potential of in situ PDMS-SiO₂ nanocomposites for use as high-performance insulating coatings in advanced electrical applications. Full article

A superhydrophilic silica coating was prepared using a sequential dipping process involving acid-catalyzed silica, base-catalyzed silica, and 3-(trihydroxysilyl)propanesulfonic acid. Acid-catalyzed and base-catalyzed silica particles with varying diameters were synthesized by hydrolyzing tetraethyl orthosilicate using HCl and NH₃·H₂O as catalysts, respectively. 3-(Trihydroxysilyl)propanesulfonic acid was obtained by oxidizing mercaptopropyl trimethoxysilane with hydrogen peroxide under acidic conditions. The resulting silica coating exhibited exceptional superhydrophilicity, with a water static contact angle of 5.0°, and demonstrated underwater superoleophobicity, with a hexadecane underwater contact angle exceeding 140°. Surfaces coated with the superhydrophilic silica coatings showed excellent performances in oil–water separation, anti-protein adsorption, and anti-fogging applications. Full article

α-Pinene is a very valuable natural raw material for organic syntheses, which is of increasing interest to scientists due to its renewability and relatively low price. This work presents the studies on the oxidation of α-pinene in the presence of two mesoporous titanium-silicate catalysts: standard Ti-SBA-15 and Ti-SBA-15 material, which was obtained by a new and green way using orange peel waste as bio-templates (Ti-SBA-15_orange peels). For the synthesis of the Ti-SBA-15 catalysts, the following raw materials were used: Pluronic P123 as the template (template usually used in the synthesis of SBA-15 materials), tetraethyl orthosilicate as the silicon source, hydrochloric acid, deionized water, and tetraisopropyl orthotitanate as the titanium source. For the synthesis of Ti-SBA-15_orange peels, a catalyst was also properly prepared, and orange peel waste as the co-templates (renewable templates) were used. The two obtained Ti-SBA-15 materials were characterized by the following instrumental methods: XRD, SEM, EDX, UV-Vis, and FTIR. Moreover, the specific surface area and pore size distribution were investigated for these catalysts with help from the nitrogen adsorption–desorption method. Catalytic tests of the obtained catalysts were performed in the oxidation of α-pinene with oxygen and by the method which did not use any solvent (α-pinene was simultaneously the raw material and solvent in this process). During the catalytic tests, the effect of temperature, catalyst content, and reaction time on the selectivities of the appropriate products and the conversion of α-pinene were studied. Depending on the conditions of the oxidation process, the catalyst obtained with the use of orange peels as co-templates showed similar or even higher activity than the standard Ti-SBA-15 catalyst. Full article

In this study, Fe₃O₄ was used as a magnetic core, combined with the characteristics of mesoporous adsorbents, to prepare a novel magnetic mesoporous composite material named MMC. Cetyltrimethylammonium bromide (CTAB) and tetraethyl orthosilicate (TEOS) were used as functional monomers, and a simple etching method was employed. The resulting MMC was used as an effective adsorbent for the magnetic solid-phase extraction of trace residues of six bisphenol endocrine disruptors (bisphenol A, bisphenol B, bisphenol C, bisphenol F, bisphenol AF, and bisphenol AP) from environmental water and food samples. Characterization results indicated that the surface of MMC exhibited a distinct wormhole-like mesoporous structure, with the successful incorporation of CTAB functional groups and Si-OH. The crystal structure of Fe₃O₄ remained stable throughout the preparation process. Mapping analysis confirmed the uniform distribution of CTAB functional groups without aggregation and demonstrated high magnetic intensity, enabling rapid separation and collection under an external magnetic field. Extraction and elution conditions were optimized, and tests were conducted for interfering substances such as humic acid, glucose, fructose, and sucrose under optimal parameters. The results showed that recovery rates were not significantly affected. The quality evaluation of the method demonstrated good linearity, a broad linear range, low limits of detection and quantification, and satisfactory recovery rates. Blank and spiked analyses were conducted for seven real samples, including environmental water (rivers and lakes) and food samples (dairy, juice, and carbonated beverages), with satisfactory spiked recovery rates achieved. Thus, the developed analytical method enables the analysis and detection of trace residues of various bisphenol pollutants in complex matrices, such as environmental water and food samples, providing a valuable reference for trace analysis of similar contaminants in complex matrices. Full article

Background/Objectives: This study assessed the effects of formulation components on the long-term stability of a previously described tetraethyl orthosilicate-based drug delivery system. Early stability studies of a product concept are crucial not only to provide information on the overall system stability and individual components’ contributions to it, but also to identify opportunities for dosage form optimization and to define its use case. Methods: We assessed the time-dependent thixogel properties—specifically, mechanical strength, thixotropy, release of model drug, and dry substance—in both real-time and accelerated shelf-life determination set-ups. Results: Our findings indicate that the concentration and molecular weight of hyaluronic acid, one of the main constituents of the investigated thixotropic systems, are key determinants of formulation stability. We further showed that changes in both of these parameters reflect on the drug release properties and stiffness of the formulation and could inform subsequent product development based on several use cases. Conclusions: Overall, this study provides an understanding of some key factors that would need to be considered prior to and in the final product development process of thixogels in preparation for commercialization. Full article

Numerous scientific studies have been conducted in recent decades with the aim to study targeted application of zeolites in various industries, ecology, agronomy and medicine. The biggest advances, however, have been documented in medical and veterinary research of the natural zeolite, clinoptilolite. Although the exact biological mechanisms of action of the zeolite clinoptilolite are not completely elucidated, obtained results point to its antioxidative, immunomodulatory and detoxifying effects, the latter partially based on release of soluble and bioavailable silica forms from the surface material. The studied zeolite clinoptilolite materials have different geographical origins which confer to the physicochemical differences in the material. In addition, the production process of the material for oral applications differs between different producers which also accounts for different properties of the surface upon mechanical activation. Recently, a well-characterized zeolite clinoptilolite material, namely the PMA-zeolite, has been tested in different clinical applications and has shown potential as supportive therapy in inflammatory conditions, osteoporosis as well as during tumor chemotherapy. We accordingly present a comprehensive review of the PMA-zeolite effects in the clinical applications and discuss its probable mechanisms of effect in vivo. Full article

In this paper, we conduct a comprehensive investigation into PVA fiber modified with SiO₂ to improve the mechanical properties of oil-well cements. Specifically, SiO₂ was coated onto the surface of polyvinyl alcohol fiber (PVAF) as its silicon source via a sol-gel process by using tetraethyl orthosilicate (TEOS), while hydrochloric acid and ammonia were respectively used as the catalyst in the sol (hydrolysis) and the gel (condensation) processes. The PVAF microstructure was then characterized with the scanning electron microscope (SEM), while the effects of the modified PVAF on both mechanical and rheological properties of oil-well cements were examined. Due to the fact that SiO₂ can be uniformly coated onto the PVAF surface, such modified PVAF can slightly improve the rheology of the cement slurry, while the raw PVAF exhibits poor dispersion at a high dosage. Compared with those of cement stone without PVAF after curing for 28 days at 60 °C, the flexural strength, compressive strength, and elastic modulus of the cement stone incorporated with the modified PVAFs were enhanced by 37.7%, 66.1%, and 50.0%, respectively. The SEM test (EDX) test, XRD test, and thermogravimetric test prove that the SiO₂ coating on the PVAF surface can promote the hydration of cement clinker and can react with Ca(OH)₂ to generate CSH gel. The SiO₂ grafted onto the surface of PVAFs can improve the bond strength at the fiber/cement matrix interface, thus improving the mechanical properties of cement stone. Full article

This study deals with the combination of two corrosion protection strategies for aluminium: barrier protection (provided by a 3.8 μm thick hybrid sol–gel coating) and aluminium pore sealing via the use of a 100 nm thick layer of aluminium oxide. A Si–O–Zr hybrid sol–gel coating (TMZ) was synthesised by combining two separately prepared sols (i) tetraethyl orthosilicate and 3-methacryloxypropyl trimethoxysilane and (ii) zirconium(IV) n-propoxide chelated with methacrylic acid. The synthesis of the Si–O–Zr hybrid sol–gel was evaluated at various stages using real-time infrared spectroscopy. A 100 nm thick Al₂O₃ film was prepared via thermal atomic layer deposition at 160 °C using trimethyl aluminium and water as precursors. The coating and film properties were assessed via focused ion beam/scanning electron microscopy coupled with energy-dispersive X-ray spectrometry. Sealing with the Al₂O₃ film did not affect the microstructure and composition of the underlying sol–gel coating. The coating’s corrosion performance in 0.1 M NaCl solution was evaluated using electrochemical impedance spectroscopy. Compared to individual coatings, the multilayer TMZ/Al₂O₃ coating ensured prolonged (more than three weeks) durable corrosion protection for the aluminium. The impedance magnitude increased by two orders compared to the uncoated substrate (|Z|_{10 mHz} from 16 kΩ cm² to almost 830 MΩ cm²). Thus, the pore sealing of the sol–gel coating using an ALD alumina film produced a protective multilayer coating system, with |Z|_{10 mHz} remaining above 5 MΩ cm² after four weeks in NaCl solution. Full article

This study presented a novel corrosion protective coating based on polyacrylic/siloxane-silica (PEHA-SS) deposited on lightweight cast aluminium alloy AlSi7Mg0.3. The synthesis of PEHA-SS comprises organic monomer 2-ethylhexyl acrylate and organically modified silane 3-(trimethoxysilyl)propyl methacrylate as well as an inorganic silane, tetraethyl orthosilicate. The steps during the synthesis process were monitored using real-time infrared spectroscopy. The coating deposited onto the AlSi7Mg0.3 surface was characterised using various techniques, including infrared spectroscopy, 3D contact profilometry, and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The corrosion resistance of the coated alloy in sodium chloride solutions was evaluated using electrochemical impedance spectroscopy. The accelerated testing of the uncoated and coated sample was performed using the Machu test. This novel, nine micrometres thick PEHA-SS coating achieved durable corrosion (barrier) protection for the AlSi7Mg0.3 alloy in 0.1 M NaCl during the first four months of immersion or under accelerated corrosion conditions in a Machu chamber containing NaCl, acetic acid, and hydrogen peroxide at 37 °C. Full article

This study was intended to exploit the possibility of using the quick gelation of alcogel that is induced by adding catalytic imidazole into a silicate-oligomer-based solution. For this purpose, the experimental viability of the direct observation of the gelation behavior was actually examined. The silicate oligomer, derived from tetraethyl orthosilicate hydrolyzed under an acidic condition (pH ~ 5), was used as the quickly gelling mother solution. The capability of the oligomer solution to form a non-flowable matter in only a few seconds when triggered by the addition of the catalytic solution of imidazole is promising, for example, for stabilizing a sandy ground surface, due to its simplicity. From the practical viewpoint, how long the gelation could take (=gel time) is a crucial parameter when the choice of an appropriate gelling chemical species needs to be made. Thus, this study focused its interest on as simple an experimental method as possible for evaluating the gel time of the gelling systems that actually underwent instantaneous gelation. The silicate oligomer solution was an appropriate material both in its quick gelling behavior and environmental friendliness. For such quick gelation, rheological approaches are not applicable for detecting the boundary in the mechanical properties that delineate the regime of “gel”. In this study, instead, direct observation was employed to capture the short interval during which the gelation was completed. The silicate-oligomer-based gelling solution was observed to lose its flowability within only 0.2 s, as it was seen to come off the bottom of the shaken cylinder at 5 Hz. For a more quantitative estimation, the same gelling solution was observed by high-speed motion picture. The high-speed motion picture could clearly capture the instantaneous gelation as a sudden arrest of the flow. The sub-millisecond direct observation of the gelation behavior revealed that the timescale of the instantaneous termination of the flow was as quick as 1 ms in order of magnitude. Such instantaneous gelation in the sub-millisecond-order timescale could not be forecasted from the observable megascopic gelation, which appeared to last from 10² ms to 10³ ms in our naked-eye observation. The noteworthy gap between the timescale of the naked-eye-observed gelation and that of the true gel time at a localized spot determined by the high-speed motion picture should be noted to avoid excess agitation, which can result in total collapse into gel fragments of the just solidifying or already solidified gel under strong deformational influence by mechanical agitation, for example. Full article

Owing to their composition-tunable and narrow emissions and high photoluminescence quantum yield (PLQY), inorganic halide perovskite quantum dots (IPQDs) are a promising option for wide color gamut displays. However, their practical applications have been limited by their lattice structure instability and surface defect states. Herein, CsPbBr₃:KBF₄@SiO₂ with improved stability and optical properties is successfully synthesized with a two-step optimization of fluorine (F) anion doping and SiO₂ in situ coating. Compared with bromide (Br), higher electronegativity and a smaller radius of F lead to stronger binding energy with Pb²⁺. Also, F anions can occupy surface Br vacancies. Then, benefiting from the acidic environment provided by BF₄⁻ hydrolysis, tetraethyl orthosilicate (TEOS) can be more easily hydrolyzed on the CsPbBr₃:KBF₄ surface to generate SiO₂ coating, thus further passivating lattice defects and improving environmental stability. Importantly, the PLQY of CsPbBr₃:KBF₄@SiO₂ achieves 85%, and the stability has been greatly improved compared with pure CsPbBr₃. Finally, CsPbBr₃:KBF₄@SiO₂/PDMS, CsPbI₃/PDMS, and CsPbCl₃/PDMS composites with narrow emissions are applied to replace traditional phosphors as color converters for direct-view light-emitting diode (LED) displays or liquid crystal display (LCD) backlights. The color gamut reaches 118.22% under the NTSC standard. Concerning the display field, it suggests likely applications in the future. Full article

The superhydrophobic feature is highly desirable for oil/water separation (OWS) operation to achieve excellent separation efficiency. However, using hazardous materials in fabricating superhydrophobic surfaces is always the main concern. Herein, superhydrophobic filters were prepared via an eco-friendly approach by anchoring silica particles (SiO₂) onto the cotton fabric surface, followed by surface coating using natural material—myristic acid via a dip coating method. Tetraethyl orthosilicate (TEOS) was used in the synthesis of SiO₂ particles from the silica sol. In addition, the impact of the drying temperature on the wettability of the superhydrophobic filter was investigated. Moreover, the pristine cotton fabric and as-prepared superhydrophobic cotton filters were characterised based on Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) and contact angle (CA) measurement. The superhydrophobic cotton filter was used to perform OWS using an oil-water mixture containing either chloroform, hexane, toluene, xylene or dichloroethane. The separation efficiency of the OWS using the superhydrophobic filter was as high as 99.9%. Moreover, the superhydrophobic fabric filter also demonstrated excellent durability, chemical stability, self-healing ability and reusability. Full article

Growing environmental concerns drive efforts to reduce packaging waste by adopting biodegradable polymers, coatings, and films. However, biodegradable materials used in packaging face challenges related to barrier properties, mechanical strength, and processing compatibility. A composite gel was developed using biodegradable compounds (prolamin, d-mannose, citric acid), as a coating to increase the oxygen barrier of food packaging materials. To improve gel stability and mechanical properties, the gels were physically cross-linked with particles synthesized from tetraethyl orthosilicate and tetramethyl orthosilicate precursors. Additionally, biocompatibility assessments were performed on human keratinocytes and fibroblasts, demonstrating the safety of the gels for consumer contact. The gel properties were characterized, including molecular structure, morphology, and topography. Biocompatibility of the gels was assessed using bioluminescent ATP assay to detect cell viability, lactate dehydrogenase assay to determine cell cytotoxicity, and a leukocyte stimulation test to detect inflammatory potential. A composite gel with strong oxygen barrier properties in low-humidity environments was prepared. Increasing the silane precursor to 50 wt% during gel preparation slowed degradation in water. The addition of citric acid decreased gel solubility. However, higher precursor amounts increased surface roughness, making the gel more brittle yet mechanically resistant. The increase of precursor in the gel also increased gel viscosity. Importantly, the gels showed no cytotoxicity on human keratinocytes or fibroblasts and had no inflammatory effects on leukocytes. This composite gel holds promise for oxygen barrier food packaging and is safe for consumer contact. Further research should focus on optimizing the stability of the oxygen barrier in humid environments and investigate the potential sensitizing effects of biodegradable materials on consumers. Full article