Journal of Sol-Gel Science and Technology最新文献

Value added materials made from agricultural residues are very attractive since they contribute in reducing environmental waste and enhancing economic sustainability. Two deposition methods were investigated where silica xerogel from sugarcane leaves (a waste from sugarcane industry) was used as a support for the synthesized gold nanoparticles. Biogenic silica was refluxed with sodium hydroxide at 80 °C to form sodium silicate solution. The gold nanoparticles were either synthesized in the sodium silicate solution or separately to form silica/Au nanoparticles through a sol-gel method. Ultraviolet (UV)-visible spectroscopy, x-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray fluorescence spectroscopy (XRF), energy dispersive x-ray (EDX) and nitrogen adsorption-desorption were used to characterize the produced Si/Au nanoparticles. The two investigated methods resulted in distinctive deposition of gold nanoparticles on a silica xerogel support and also significantly different textural properties. The produced silica/gold nanoparticles had a Brunauer-Emmett-Teller (BET) surface area of up to 619 m²/g, pore diameter of 8.3 nm and pore volume of 1.28 cm³.g⁻¹.

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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