Search Results (65)

The siliceous precursor was hydrolyzed from tetraethylorthosilicate (TEOS) under acidic conditions, followed by the addition of sodium aluminate and sodium hydroxide. Y zeolite was subsequently obtained through hydrothermal crystallization under alkaline conditions. Key synthesis parameters, including reactant molar ratios, crystallization temperature, and time, were systematically varied to optimize the synthesis conditions. The synthesized products were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption analysis, and inductively coupled plasma (ICP) elemental analysis. Well-crystallized Y zeolite with a silica-alumina ratio (SAR) of 5.55 was successfully synthesized via TEOS hydrolysis catalyzed by sulfuric acid at a low crystallization temperature of 85 °C. The catalytic performance of benzyl phenyl ether, a lignin model compound, over NiY catalyst was evaluated in a high-pressure reactor. The results indicate that the catalytic efficiency of Y zeolite synthesized using TEOS as the silicon source under acidic hydrolysis conditions is significantly superior to Y zeolite prepared using alkaline silica sol as the silicon source. Full article

Developing a durable multifunctional superhydrophobic coating on polymeric films that can be industrially scalable is a challenge in the field of surface engineering. This article presents a novel method for a scalable technology using a simple single-step fabrication of a superhydrophobic coating on polymeric films that exhibits excellent water-repelling and UV-blocking properties, along with impressive wear resistance and chemical robustness. A mixture of titanium precursors, tetraethylorthosilicate (TEOS), hydrophobic silanes and silica nano/micro-particles is polymerized directly on a corona-treated polymeric film which reacts with the surface via siloxane chemistry. The mixture is then spread on polymeric films using a Mayer rod, which eliminates the need for expensive equipment or multistep processes. The incorporation of silica nanoparticles along with titanium precursor and TEOS results in the formation of a silica–titania network around the silica nanoparticles. This chemically binds them to the activated surface, forming a unique dual-scale surface morphology depending on the size of the silica nanoparticles used in the coating mixture. The coated films were shown to be superhydrophobic with a high water contact angle of over 180° and a rolling angle of 0°. This is due to the combination of dual-scale micro/nano roughness with fluorinated hydrocarbons that lowered the surface free energy. The coatings exhibited excellent chemical and mechanical durability, as well as UV-blocking capabilities. The results show that the coatings remain superhydrophobic even after a sandpaper abrasion test under a pressure of 2.5 kPa for a distance of 30 m. Full article

In this work, the structure of silica thin films synthesized with three different SiO₂ precursors and obtained by the sol–gel method and dip coating technique was studied. Additionally, the influence of Ag addition on the obtained silica sols and then gel structure was investigated. Silica coatings show antireflective properties and high thermal resistance, as well as hydrophobic or hydrophilic properties. Three different silica precursors, TEOS (tetraethylorthosilicate), DDS (dimethyldietoxysilane) and Aerosil^TM, were selected for the synthesis. DDS added to silica sol act as a pore size modifier, while Ag atoms are known for their antibacterial activity. Coatings were deposited on two different substrates: steel and titanium, dried and annealed at 500 °C in air (steel substrate) and in argon (titanium substrate). For all synthesized films, IR (infrared) spectroscopic studies were performed together with GID and XRD (Grazing Incidence Diffraction, X-ray Diffraction) measurements. The topography and morphology of the surface were traced by SEM and AFM microscopic methods, providing information on the samples’ roughness, particle sizes and thickness of the particular layers. The wetting angle values were also measured. GID and XRD measurements pointed to the distinct contribution of an amorphous phase in the samples, allowing us to recognize the crystalline phases and calculate the silver crystallite sizes. The FTIR spectra gave information on the first coordination sphere of the studied samples. Full article

A series of nanospherical-shaped silicates containing heteroatoms (Al, Zr or Ti) were successfully synthesized using tetraethylorthosilicate (TEOS) or silica colloids as a silicon source. These metallosilicate nanospheres were used as silicon nutrients to obtain silicalite zeolites with micro-mesoporosity and improved textural properties. The results demonstrated that TEOS acted as a suitable silicon source to produce amorphous silicates and a spherical-type zeolite architecture with Zr and Ti heteroatoms included in their framework, with preferable particle size and crystallinity. The surface functionality of the mesostructured nanospheres and zeolite silicates provide active centers for the esterification of glycerol with acetic acid (EG) reaction. The dispersion of Cu entities on the surface of the zeolites achieved high glycerol conversions selectively producing triacetin in comparison with Fe counterparts. Full article

“Core/shell” composites are based on a ferrite core coated by two layers with different properties, one of them is an isolator, SiO₂, and the other is a semiconductor, TiO₂. These composites are attracting interest because of their structure, photocatalytic activity, and magnetic properties. Nanocomposites of the “core/shell” МFe₂O₄/SiO₂/TiO₂ (М = Zn(II), Co(II)) type are synthesized with a core of MFe₂O₄ produced by two different methods, namely the sol-gel method (SG) using propylene oxide as a gelling agent and the hydrothermal method (HT). SiO₂ and TiO₂ layer coating is performed by means of tetraethylorthosilicate, TEOS, Ti(IV) tetrabutoxide, and Ti(OBu)₄, respectively. A combination of different experimental techniques is required to prove the structure and phase composition, such as XRD, UV-Vis, TEM with EDS, photoluminescence, and XPS. By Rietveld analysis of the XRD data unit cell parameters, the crystallite size and weight fraction of the polymorphs anatase and rutile of the shell TiO₂ and of the ferrite core are determined. The magnetic properties of the samples, and their activity for the photodegradation of the synthetic industrial dyes Malachite Green and Rhodamine B are measured in model water solutions under UV light irradiation and simulated solar irradiation. The influence of the water matrix on the photocatalytic activity is determined using artificial seawater in addition to ultrapure water. The rate constants of the photocatalytic process are obtained along with the reaction mechanism, established using radical scavengers where the role of the radicals is elucidated. Full article

A novel organic–inorganic gliclazide-loaded composite bead was developed by an ionic gelation process using acidified CaCl₂, chitosan and tetraethylorthosilicate (TEOS) as a crosslinker. The beads were manufactured by crosslinking an inorganic silicone elastomer (-OH terminated polydimethylsiloxane, PDMS) with TEOS at different ratios before grafting onto an organic backbone (Na-alginate) using a 3² factorial experimental design. Gliclazide’s encapsulation efficiency (EE%) and drug release over 8 h (% DR 8 h) were set as dependent responses for the optimisation of a pharmaceutical formula (herein referred to as ‘G op’) by response surface methodology. EE % and %DR 8 h of G op were 93.48% ± 0.19 and 70.29% ± 0.18, respectively. G op exhibited a controlled release of gliclazide that follows the Korsmeyer–Peppas kinetic model (R² = 0.95) with super case II transport and pH-dependent swelling behaviour. In vitro testing of G op showed 92.17% ± 1.18 cell viability upon testing on C2C12 myoblasts, indicating the compatibility of this novel biomaterial platform with skeletal muscle drug delivery. Full article

This work introduces the synthesis of hybrid polymer electrolytes based on polyethylene oxide (PEO) and electrolyte solution bis(trifluoromethane)sulfonimide lithium salt/ionic liquid 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (LiTFSI/EMIMTFSI) with in situ produced and dispersed silica particles by the sol–gel method. Conventional preparation of solid polymer electrolytes was followed by desolvation of lithium salt in a polymer matrix of PEO, which, in some cases, additionally contains plasticizers. This one-pot synthesis is an alternative route for fabricating a solid polymer electrolyte for solid-state batteries. The presence of TFSI- reduces the crystallinity of the PEO matrix (plasticizing effect), increases the dissociation and solubility of LiTFSI in the PEO matrix because of a highly delocalized charge distribution, and reveals excellent thermal, chemical, and electrochemical stability. Tetraethylorthosilicate (TEOS) was chosen due to the slow reaction rate, with the addition of (3-glycidyoxypropyl)trimethoxysilane (GLYMO), which contributes to the formation of a silica network. FTIR studies confirmed the interactions between the silica, the polymer salt, and EMIMTFSI. Impedance spectroscopy measurements were performed in a wide range of temperatures from 25 to 70 °C. The electrochemical performance was explored by assembling electrolytes in LiCoO₂ (LCO), NMC(811), and LiFePO₄ (LFP) coin half-cells. The HPEf15 shows a discharge capacity of 143 mA/g for NMC(811) at 0.1 C, 134 mA/g for LCO, and 139 mA/g for LFP half-cells at 0.1 C and 55 °C. The LFP half-cell with a discharge capacity of 135 mA/g at 0.1 C (safety potential range of 2.8 to 3.8) obtained a cyclability of 97.5% at 55 °C after 100 cycles. Such a type of electrolyte with high safety and good electrochemical performance provides a potential approach for developing a safer lithium-ion battery. Full article

High-performance coating could be used to protect steels in engineering. The GPTMS-TEOS hybrid coatings were successfully prepared using (3-glycidoxypropyl) trimethoxysilane (GPTMS) and tetraethylorthosilicate (TEOS) as reaction raw materials and diethylenetriamine (DETA) as both a curing agent and catalyst at room temperature. The hybrid coating contained amorphous SiO₂ and was characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The DETA content of the hybrid coating has a significant impact on the performance of the coating. As the DETA content increases, the thermal stability of the hybrid coating increases at 400–600 °C due to the production of more SiO₂ in the amine-rich state. However, the gelation time decreases dramatically, preventing the hybrid coating from better infiltrating the surface of the steel substrate. In addition, there are not enough silicon hydroxyl groups to bond with the hydroxyl groups on the surface of carbon steel and adhesion is significantly reduced. Therefore, hybrid coatings with a moderate DETA content (NH:epoxy ratio equivalent to 1:1) show the best corrosion resistance, with a third-order magnitude increase in corrosion resistance compared to that of carbon steel. Full article

The ordered mesoporous silica MCM-48 with cubic Ia3d structure was synthesized using the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) as a template agent and tetraethylorthosilicate (TEOS) as a silica source. The obtained material was first functionalized with (3-glycidyloxypropyl)trimethoxysilane (KH560); further, two types of amination reagents were used: ethylene diamine (N2) and diethylene triamine (N3). The modified amino-functionalized materials were characterized by powder X-ray diffraction (XRD) at low angles, infrared spectroscopy (FT-IR) and nitrogen adsorption–desorption experiments at 77 K. Characterization from a structural point of view reveals that the ordered MCM-48 mesoporous silica has a highly ordered structure and a large surface area (1466.059 m²/g) and pore volume (0.802 cm³/g). The amino-functionalized MCM-48 molecular sieves were tested for CO₂ adsorption–desorption properties at different temperatures using thermal program desorption (TPD). Promising results for CO₂ adsorption capacities were achieved for MCM-48 sil KH560-N3 at 30 °C. At 30 °C, the MCM-48 sil KH560-N3 sample has an adsorption capacity of 3.17 mmol CO₂/g SiO₂, and an efficiency of amino groups of 0.58 mmol CO₂/mmolNH₂. After nine adsorption–desorption cycles, the results suggest that the performance of the MCM-48 sil KH N2 and MCM-48 sil KH N3 adsorbents is relatively stable, presenting a low decrease in the adsorption capacity. The results reported in this paper for the investigated amino-functionalized molecular sieves as absorbents for CO₂ can be considered as promising. Full article

In this study, a process is developed for the fabrication of buried top-gated graphene transistors with Al₂O₃ as a gate dielectric, yielding devices that can be suitable for not only flexible electronics but also laser-induced graphene (LIG)-based technology implementations. A new processing option is presented with the use of tetraethyl-orthosilicate (TEOS) as an etch stop for contact via etching of Al₂O₃. Buried locally gated Al/Al₂O₃ graphene field-effect transistors (GFETs) are fabricated with Dirac points as low as 4 V, with a metal-to-graphene contact resistance as low as ∼1.7 kΩ·µm, and an average hole mobility of 457.97 cm²/V·s with a non-uniformity of 93%. Large device variation and non-uniformity in electrical performance are not uncommon for graphene-based devices, as process-induced defects play a major role in such variation. AFM, SEM, Raman spectroscopy, and model fitting indicated that the rough Al/Al₂O₃ surface was the main factor for the observed device variation. AFM analysis indicated a graphene surface roughness Ra of 16.19 nm on top of the buried Al/Al₂O₃ gate in contrast to a Ra of 4.06 nm over Al₂O₃/SiO₂. The results presented indicate the need to reduce device variability and non-uniformity by improving transfer methods, as well as the use of smoother surfaces and compatible materials. The presented analyses provide a framework with which other researchers can analyze and correlate device variation and non-uniformities while methods to reduce variability are investigated. Full article

Plasmonic nanostructures represent a suitable platform for the detection of biomolecule interactions. Their surface functionalization can be performed through different strategies. Optimal thickness, homogeneity, and hydrophilicity of the functional layer can play a crucial role in defining the sensing capabilities required to perform bioassays. In this framework, a combination of tetraethylorthosilicate (TEOS) and a commercial polymer (MCP) was evaluated to improve these features. In our more recent studies, we focused on plasmon-enhanced fluorescence for the detection of a microbial-derived synthetic oligonucleotide. An effective improvement of the fluorescence signal was detected for the combined TEOS and MCP coating. Full article

Textile materials with fluorescent, repellent, or antimicrobial properties are increasingly used in common applications. Obtaining multi-functional coatings is of wide interest, especially for applications related to signaling or to the medical field. In order to increase the performance (color properties, fluorescence lifetime, self-cleaning or antimicrobial properties) of textile materials with special uses, a series of research was carried out regarding the modification of surfaces with nanosols. In this study, coatings with multiple properties were obtained by depositing nanosols on cotton fabrics generated through sol–gel reactions. These multifunctional coatings are hybrid materials in which the host matrix is generated using tetraethylorthosilicate (TEOS) and network modifying organosilanes:dimethoxydimethylsilane (DMDMS) or dimethoxydiphenylsilane (DMDPS) in a 1:1 mass ratio. Two curcumin derivatives were embedded in siloxane matrices, a yellow one (CY) that is identical to bis-demethoxycurcumin (one of the natural constituents in turmeric) and a red dye (CR) that has a N,N-dimethylamino group grafted in position 4 of the dicinnamoylmethane skeleton of curcumin. The nanocomposites obtained by embedding curcumin derivatives in siloxane matrices were deposited on cotton fabric and studied in relation to the dye and the type of host matrix. Fabrics coated with such systems provide a hydrophobic surface, have fluorescent and antimicrobial properties, change color depending on the pH, and therefore can be used in various fields where textiles provide signaling properties, self-cleaning, or antibacterial protection. The coated fabrics maintained their good multifunctional properties even after several washing cycles. Full article

Superhydrophobic poly(vinylidene fluoride) (PVDF) membranes were obtained by a surface treatment consisting of oxygen plasma activation followed by functionalisation with a mixture of silica precursor (SiP) (tetraethyl-orthosilicate [TEOS] or 3-(triethoxysilyl)-propylamine [APTES]) and a fluoroalkylsilane (1H,1H,2H,2H-perfluorooctyltriethoxysilane), and were benchmarked with coated membranes without plasma activation. The modifications acted mainly on the surface, and the bulk properties remained stable. From a statistical design of experiments on surface hydrophobicity, the type of SiP was the most relevant factor, achieving the highest water contact angles (WCA) with the use of APTES, with a maximum WCA higher than 155° for membranes activated at a plasma power discharge of 15 W during 15 min, without membrane degradation. Morphological changes were observed on the membrane surfaces treated under these plasma conditions, showing a pillar-like structure with higher surface porosity. In long-term stability tests under moderate water flux conditions, the WCA of coated membranes which were not activated by oxygen plasma decreased to approximately 120° after the first 24 h (similar to the pristine membrane), whilst the WCA of plasma-treated membranes was maintained around 130° after 160 h. Thus, plasma pre-treatment led to membranes with a superhydrophobic performance and kept a higher hydrophobicity after long-term operations. Full article

The present research aims to investigate the chemical and morphological properties of the methylated silica xerogels produced via the co-gelation approach combined with surface silylation. In the sol–gel synthesis, methyltrimethoxysilane (MTMS) and tetraethylorthosilicate (TEOS) were utilized as silica precursors and trimethylchlorosilane (TMCS) served as a silylating agent. Structural changes were observed depending on the MTMS/TEOS molar ratio and on the post-synthesis-performed surface silylation of the xerogels. Post-synthesis silylation plays a critical role in the exchanging of the surface silanols with methyl groups, preserving the monolithic form. The morphological and structural changes were followed by SEM, ²⁹Si-MAS-NMR, FTIR spectroscopy, nitrogen porosimetry, and contact angle measurements. The results have shown significant structural variations depending especially on the MTMS content. With an increasing MTMS content, the morphology of the samples has changed from a micro/mesoporous texture to a meso/macroporous texture. A higher degree of methyl substitution has been achieved for the silylated samples both confirmed by the FTIR and ²⁹Si-NMR results. On the other hand, only the samples with a high MTMS content could preserve their structural integrity after evaporative drying, and all have exhibited a high degree of hydrophobicity with θ > 140°. Full article

The gel electrolyte significantly influences gel valve-regulated lead acid battery performance. To address this, the paper describes the preparation of novel polymer gel electrolytes using poly (vinyl alcohol) (PVA) and tetraethylorthosilicate (TEOS) for valve-regulated lead–acid batteries. FTIR technique is used to confirm the chemical reaction between PVA and TEOS. Electrochemical analyses such as cyclic voltammetry and electrochemical impedance spectroscopy were applied to optimize the concentration of PVA-TEOS polymer gel electrolyte. The optimum concentration of polymer gel electrolyte was determined as 20 wt% of TEOS in PVA (PE-1) with higher anodic peak and lower Rs and Rct values. The Galvanostatic charge–discharge tests were performed on the optimized gel system prototype battery. The highest capacity of 6.86 × 10⁻⁵ Ah at a current density of 0.2 mA cm⁻² was achieved with an excellent capacity retention ratio of 85.7% over 500 cycles. The exceptional cycle performance and high capacity make PVA-TEOS gel electrolyte a promising candidate for practical battery application. Full article