Journal of Sol-Gel Science and Technology最新文献

We investigated the effect of heating rates during post-baking on the minimum resolution widths of film patterns prepared from positive-type photosensitive random-structure oligomeric silsesquioxanes (oligo-SQs) with only phenyl (Ph) or both Ph and methyl (Me) groups (Ph group content ≥50 mol%) as substituents. Previously, increasing the Me group content produced 20 μm minimum widths. This was attributed to flow, fusion, and wrinkling during post-baking at 60 °C/min, and partly attributed to enhanced silanol (Si-OH) group reactivity during early stages of post-baking. Here, film patterns for high-definition optical devices fabricated from oligo-SQs with only Ph groups, or with the highest Me group content, produced desired 10 μm widths when heated slowly at 6 °C/min or 3 °C/min, respectively. The decreased widths were attributed to reduced flowability because of enhanced Si-OH group reactivity during heating and the changes and bulkiness of the oligo-SQ molecular structure. The Si-OH reactivity may have been enhanced by the activation of molecular chain motions with increased Me group content and the lower weight-average molecular weight. Structural changes and substituent bulkiness may have also suppressed the chain motions.

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A proof of principle study toward developing a novel methodology which could be applicable for a non-invasive monitoring of the release of cargo molecules from therapeutic and diagnostic nanoparticles, as well as for possible monitoring of tissue pH variations. This was achieved by quantifying changes in longitudinal relaxation time (T₁) before and after the pH-responsive release of contrast agents, for magnetic resonance imaging (MRI), from the pores of mesoporous silica nanoparticles (MSNs). The pores were filled with the FDA-approved contrast agent Gadobutrol (GdB), and its retention inside the pores ensured by covalent attachment of β-cyclodextrin monoaldehyde to hydrazine-functionalized MSN, through acidification-cleavable hydrazone linkage. The release kinetics of GdB was measured by fluorescence spectroscopy which revealed that the release of the contrast agent was enhanced at pH 5.0 in comparison to the release at pH 6.0 and 7.4. Furthermore, the changes in T₁, occurring in response to the enhanced release of GdB from the pores of MSN at weakly acidic conditions, were successfully demonstrated by MRI measurements. It is envisioned that this approach using contrast agent-loaded nanoparticles before the treatment with the drug-filled analogs, could be applied in the future for tracking the locations and efficacies of nanomedicines for therapeutic cargo delivery.

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Tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), and their mixtures were used for the cosolvent-free synthesis of macroporous silica gels as precursors for monolithic silica glasses. The liquid-state ²⁹Si nuclear magnetic resonance (NMR) spectroscopy of precursor solutions indicated that cross-transesterification between TMOS and TEOS was completed in a few hours at 20 °C in the presence of an acid catalyst, whereas it was negligible when the catalyst was absent. In the precursor solutions prepared from TMOS, phase separation occurred after gelation, resulting in translucent gels. In contrast, in the solutions prepared from TEOS or a mixture of TMOS and TEOS at a TMOS mole fraction of 0.8, the phase separation can be induced before gelation, and opaque xerogels were easily obtained without fracture. The average size of macroscopic particles and macroporous structures were uniform over opaque xerogels prepared from TEOS. In contrast, in opaque xerogels prepared from the TMOS-rich mixture of TMOS and TEOS, the average particle size and macroscopic porosity inside them were notably smaller than those of the subsurface, probably because of a large exotherm upon gelation and the resulting temperature gradient in the gelling solutions. Such spatial morphology distribution made the sintering of the opaque gels into clear silica glasses difficult. Opaque gels prepared from TEOS and translucent gels prepared from solutions containing TMOS were transformed to clear silica glasses in high yields of ~99% by sintering in a helium atmosphere at 1050–1350 °C.

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Transparent hydrophobic glass materials had played an important role in our daily life, but some problems such as complex or expensive manufacturing processes, poor wear resistance and opacity limited its applications. In this paper, a composite silica sol composed of modified SiO₂ nanoparticles and transparent special water-based silicone resin was prepared. An organic-inorganic hybrid coating was formed on the glass surface by a simple spraying method to produce a hydrophobic surface with high transparency and durability. Perfluorinated polyether (PFPE) chains with lower surface energy were introduced into the silica sol prepared above. The composite coatings had both the low surface energy of fluorine-containing substances and the rough structure. The surface topography, static water contact angle, self-cleaning performance, anti-fouling performance, wear resistance, adhesion performance, acid and alkali resistances of the coating were tested. The results showed that the maximum water contact angle of the prepared transparent hydrophobic glass can reach 140°. The coating had good adhesion performance, wear resistance, self-cleaning and acid resistant, but poor alkaline resistance.

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Semiconducting Cu₂O have excellent optical and electronic properties and are more promising candidates for advanced electronic applications. In the current study, pure and 3.125%, 6.25%, and 12.5% Zn doped Cu₂O compositions were studied using density functional theory in the framework of wien2k-code. Experimentally, uniform and smooth thin films of these compositions were successfully synthesized through the spin coating technique. The elemental composition and morphology were studied using energy-dispersive X-ray spectroscopy and field emission scanning electron microscopy, respectively. Crystallographic analysis of thin films shows a cubic phase structure having space-group 224 Pn-3m. The total density of states confirms the overlapping of states at the Fermi level for Zn-doped compositions. The significant variations in thermoelectric parameters observed with change of temperature for pure and Zn substituted Cu₂O compositions, especially the Seebeck-coefficient values vary from 2.5 × 10⁻⁴ to 5.5 × 10⁻⁵ VK⁻¹ for these cuprous oxide compositions. The optical-parameter such as absorption and extinction coefficient curves reached maxima at the highest photon energies. The enhancement in transmittance power and reduction in the band gap energy from 2.08 eV to 1.75 eV with the substitution of Zn material enhanced the availability of these compositions for advanced applications.

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Indium tin oxide (ITO), a critical n-type semiconductor material, has widely used in the field of photoelectric material due to its significant conductivity and transparency. In addition, it also has excellent gas sensitivity. In this paper, a unique ITO, hollow spherical ITO powders were prepared by hydrothermal method using PEG-4000 & DL-aspartic acid (DLAA) and PEG-400 & ethylene diamine tetra acetic acid (EDTA) as two composite templates. The preparation conditions of the hollow spherical ITO powders with 2.2 μm diameter were obtained: the precipitator is urea, the molar ratio of DLAA and In³⁺ is 3:1, the temperature of hydrothermal reaction is 120 °C, the time of hydrothermal reaction is 10 h, the molar ratio of PEG-4000 and In³⁺ is 5:1, the temperature and time of calcination is 450 °C and 3 h respectively. Ultimately, hollow spherical ITO powders were prepared and the resulting samples were analyzed for a range of properties. The properties showed as follow: the specific surface area was 64.107 g/m², the resistivity is 164.03 Ω.cm. The formation mechanism of the hollow spherical ITO powders was discussed systematically. Significantly, unique ITO powders with hollow spherical have been obtained by template method, which has application potential in the gas sensitivity of ITO powders.

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Cement-based composites comprise a binder matrix with or without aggregates. Hydration of cement is an exothermic reaction that releases considerable quantities of heat, causes drying shrinkage. Hydrogels can help mitigate such cracking as their hydrophilic characteristics and 3D crosslinked structure enables them to absorb and directly release water into the cement matrix over time. This study aims to synthesize and analyze the effect of adding hybrid nanocomposite hydrogels with different concentrations (0, 10, and 20% w/v) of Cloisite-Na⁺ nanoclay in their fresh and hardened cement mortar states. The hydrogels were synthesized via free radical polymerization, and four cementitious mortar samples (M, M0, M10, and M20). The results demonstrated that the density of all the mortars in the fresh state was ~2.16 ± 0.01 g.cm⁻³, but a decreasing trend was observed that could attributed to the increase of air incorporation into the mortar. At 28 days, the results indicated that the hydrogel with 20% Cloisite-Na⁺ was the most efficient, causing a reduction of ~4.4% in water absorption by the mortar. For all, three curing conditions considered, all mortars demonstrated considerable shrinkage over time. However, the controlled curing indicated that M20 mortars demonstrated 31% less shrinkage compared to the control sample. The scientific relevance of incorporating hydrogels into cement mortars lies in their ability to effectively address critical issues related to shrinkage-induced cracking and deterioration. Moreover, the use of hydrogels aligns with sustainable construction practices by reducing the need for additional water and minimizing the environmental impact associated with cement materials production.

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Porosity and thermal stability are the main constraints that determine the performance of zirconia (ZrO₂) for a wide range of applications, including adsorption, catalysis, filtration, etc. Here, we have proposed the rational design of electrospun ZrO₂ nanofibers (NFs) with high surface areas and good thermal stability. Water vapor pre-treatment was used to modify the surface structure of the NFs with the removal of soft templates at a lower temperature. In addition, amorphous B₂O₃ was introduced into the ZrO₂ NFs to improve the thermal stability of the porous structure. The as-prepared NFs had high surface area of 380 m²/g and even 300 m²/g after heat treatment at 450 °C. The catalytic activity of modified ZrO₂ NFs as support materials in bromination reaction of phenol red was tested. And a high specific bromination activity of 3.02 mmol h⁻¹ g⁻¹ was obtained. This work could provide promising strategies for preparing electrospun porous oxide NFs with high surface area and good thermal stability in order to optimize performance.

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The current research reports the influence of particle size and concentration of Al₂O₃ additive on protective performance of double-layer coating of silane /multi-walled carbon nanotube (MWCNT) deposited on AZ91 magnesium alloy through sol-gel dip coating. The main objective of Al₂O₃ incorporation to the base silica is to seal different types of defects in the coating and increase the surface hardness, anti-wear, and anticorrosion properties of the coatings which can be beneficial for real-world applications of AZ91 magnesium alloy in industries such as automotive, aircraft, and aerospace. For this purpose, several coatings with different Al₂O₃ contents of various sizes (50 nm, 100 nm, 300 nm, and 1 μm) were deposited on AZ91 magnesium alloy with thicknesses of about 5–10 µm. It was found that the optimal Al₂O₃ contents depend on their particle size; such that 1.5, 2, 3, and 5 wt% of Al₂O₃ were determined as the optimal values for particle sizes of 50, 100, 300, and 1000 nm, respectively. Results revealed that incorporation of an optimal amount of Al₂O₃ into double-layer coating improved the corrosion resistance where, the polarization resistance of the coatings containing the optimal contents of Al₂O₃ with particle sizes of 50 nm, 100 nm, 300 nm, and 1 μm were 360.1, 265.3, 240.8, and 157.2 kΩ.cm², respectively. Moreover, the coating comprising 1.5 wt% Al₂O₃ with a particle size of 50 nm exhibited denser, finer, and lower porosity.

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Nano-bioactive glass 60SiO₂-36CaO-4P₂O₅ (mol.%) was synthesized by using the sol-gel method without using acid catalysts. Two sol precursors, tetraethyl orthosilicate and triethyl phosphate, were tested for hydrolysis at different temperatures and times. Experimental observation shows that the precursors tetraethyl orthosilicate, triethyl phosphate, and calcium nitrate tetrahydrate were hydrolyzed in the solvent system H₂O/C₂H₅OH (weight ratio of 1/8) at 80 °C. In a hydrothermal reactor, the resulting sol was transformed into a gel, and then the dried gel was transformed into a glass material by heating treatment. Physical-chemical methods such as TG-DSC, XRD, FTIR, BET, and SEM-TEM were used to evaluate synthesized glass. Additionally, the glass material was assessed for its bioactivity in SBF solution (Simulated Body Fluid), and biocompatibility with fibroblast cells (L-929) following the ISO10993-5 standard. Research results show that the glass 60SiO₂-36CaO-4P₂O₅ (mol.%) synthesized in this study is an amorphous material with particle size at the nanoscale, forming a mesoporous structure. The synthesized glass can be bioactive by forming an apatite mineral layer when soaked in SBF solution, and it is biocompatible with L-929 cells.

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