Non-hydrolytic Sol Gel Research Articles

Low-temperature preparation of nano-sized Al2TiO5 powder via non-hydrolytic sol-gel route with Al metal as the aluminum source

Al2TiO5 powder was prepared using the non-hydrolytic sol-gel route, with Al powder and titanium tetrachloride as precursor materials. The synthesized powder was characterized via XRD, DSC-TG, TEM, FTIR, FE-SEM, and laser particle size analyzer. The results indicated that Al2TiO5 powder can be synthesized at 750 ℃ via gelation when the aluminum-to-alcohol molar ratio was 1:14 and titanium tetrachloride concentration was 0.9 mol/L. The average particle size of Al2TiO5 powder was 80 nm using reflux gelation and 35 nm with direct drying gelation. The Al metal utilized the hydrogen chloride produced in situ to activate itself and formed Al-O-Ti hetero-bonds through non-hydrolytic polycondensation. The Al-O-Ti hetero-bonds underwent an exothermic reaction at around 695 ℃ to form Al2TiO5. This research has broadened the range of precursor materials available for preparing Al2TiO5 using the non-hydrolytic sol-gel route.

The mechanical and dielectric properties of high-density Ti-doped MgAl2O4 ceramic prepared by non-hydrolytic sol-gel combined with mechanochemical method

The synthesis of MgAl2O4 requires high calcination temperatures which generally result in larger grain sizes and smaller specific surface areas. These factors pose challenges in achieving high-density MgAl2O4 ceramic. This study introduces an innovative approach that has successfully sintered MgAl2O4 ceramic at 1500 ℃ with MgAl2O4 powder prepared using a Non-Hydrolytic Sol-Gel (NHSG) method combined with a mechanochemical method. The sintered MgAl2O4 ceramic with 2 wt% TiCl4 doping displays an apparent porosity of only 0.09 %, a flexural strength of 183 MPa, a relative permittivity of 8.7, a quality factor of 77000 GHz, and a frequency temperature coefficient of −59.4 ppm/℃. The introduction of titanium ions causes lattice distortion and cationic vacancies, which promotes sintering and improves the mechanical and dielectric properties of the resulting ceramic. This study demonstrates the effectiveness of NHSG combined with the mechanochemical method in preparing MgAl2O4 ceramic with enhanced sintering properties.

Removal of Methylene Blue from Aqueous Solution through Adsorption and Heterogeneous Fenton Reaction using Iron Oxides Produced by Different Methods

Direct discharge of industrial wastewater containing dyes into water bodies has contributed to the scarcity of drinking water. As environmental legislation becomes stricter, it is increasingly important to develop efficient methods for wastewater treatment. Traditional methods are commonly costly and have limited efficiency. This study aimed to prepare iron oxides via different synthetic routes and evaluate the effect of synthesis method on the efficiency of these materials as adsorbents and heterogeneous Fenton catalysts for the removal of methylene blue from aqueous solution. Iron oxides were synthesized by non-hydrolytic sol–gel (NHSG) and co-precipitation (CP) methods, followed by hydrothermal treatment for different times. CP oxides demonstrated high efficiency in dye adsorption, particularly the sample subjected to hydrothermal treatment for 6 h (CP-R6). This sample achieved 94.04% removal in 120 min. NHSG materials, by contrast, were less effective. The CP series of materials showed superior catalytic performance in heterogeneous Fenton experiments, with CP-R6 reaching 98.79% decolorization in 240 min. X-ray diffraction analysis indicated that iron oxides were composed of crystalline hematite and maghemite. Scanning electron microscopy revealed that CP materials were more porous and homogeneous than NHSG materials. The results demonstrated the efficiency of the developed iron oxides in removing methylene blue via adsorption and heterogeneous Fenton degradation and clarified how synthesis method influences adsorptive and catalytic properties.

Non-hydrolytic sol-gel synthesis of amine-functionalized silica: Template- and catalyst-free preparation of mesoporous catalysts for CO2 valorization

Carbon dioxide utilization presents an important and topical research topic. However, the performance of catalysts needed for CO2 transformations does not achieve the necessary levels for their widespread application. To this end, we decided to study non-aqueous condensations providing amine-functionalized silica catalysts, possibly active in CO2-epoxide cycloaddition reaction. While non-hydrolytic sol-gel method is well-known for its efficiency in providing highly porous Lewis and Brønsted acid metallosilicates, here we show for the first time its application for the preparation of silica-based catalysts containing basic groups. First, the reaction conditions were screened to reproducibly obtain porous materials with preserved amine moieties. These were identified as follows: silicon tetraacetate and bridging tertiary amine silanes as precursors, toluene as a solvent, and temperature between 160 and 180 °C. In such a way, materials with up to 776 m2 g−1 and 1.58 cm3 g−1 were obtained in one-step process, without any template, after conventional drying step. Next, the amine-functionalized materials were tested in CO2-epoxide coupling providing cyclic organic carbonates with high selectivity (>99 %) and moderate activity (up to 86 % epichlorohydrin conversion after 1 h at 120 °C and 10 bar CO2). The characterization of spent catalysts revealed a presence of cyclic organic carbonates at the catalyst surface as well as conversion of tertiary amine groups to quaternary ammonium moieties.

A Comparative Study of Ni-Based Catalysts Prepared by Various Sol-Gel Routes.

The use of heterogeneous catalysts to increase the development of green chemistry is a rapidly growing area of research to save industry money. In this paper, mesoporous SiO2-Al2O3 mixed oxide supports with various Si/Al ratios were prepared using two different sol-gel routes: hydrolytic sol-gel (HSG) and non-hydrolytic sol-gel (NHSG). The HSG route was investigated in both acidic and basic media, while the NHSG was explored in the presence of ethanol and diisopropyl ether as oxygen donors. The resulting SiO2-Al2O3 mixed oxide supports were characterized using EDX, N2 physisorption, powder XRD, 29Si, 27Al MAS-NMR and NH3-TPD. The mesoporous SiO2-Al2O3 supports prepared by NHSG seemed to be more regularly distributed and also more acidic. Consequently, a simple one-step NHSG (ether and alcohol routes) was selected to prepare mesoporous and acidic SiO2-Al2O3-NiO mixed oxide catalysts, which were then evaluated in ethylene oligomerization. The samples prepared by the NHSG ether route showed better activity than those prepared by the NHSG alcohol route in the oligomerization of ethylene at 150 °C.

Photocatalytic Degradation of Paracetamol and Antibacterial Activity of La-Modified TiO2 Obtained by Non-Hydrolytic Sol–Gel Route

The current study aims to synthesize and analyze both pure and La-doped TiO2, and evaluate the photocatalytic and antibacterial activity of as-prepared samples. Doped and undoped samples were prepared by the non-hydrolytic sol–gel method from titanium(IV) chloride, benzyl alcohol, and lanthanum(III) nitrate followed by thermal treatment. Lanthanum content in synthesized samples was 0.4, 1, and 5 mol%. The resulting nanopowders’ structure and morphology were described using XRD, IR, and UV–Vis analysis. The average particle sizes of pure and doped TiO2 were about 6–15 nm and anatase was found to be a dominant crystalline phase in the samples. It was observed that particle sizes decreased on increasing La content. The photocatalytic activity of the pure and La-doped sol–gel powders was estimated in the decomposition of paracetamol in distilled water using ultraviolet light illumination. Doping with lanthanum ions has been shown to increase the photocatalytic properties on the degradation of paracetamol. Furthermore, the annealed catalysts (pure and La3+ doped) showed increased photocatalytic activity and degradation of the analgesic in comparison with non-annealed materials. In both cases, the highest photocatalytic efficiency is observed at the optimal La3+ (1 mol%) concentration. The antimicrobial activity of 1 mol% La/TiO2 was tested against a reference strain E. coli in the presence of ultraviolet light and in dark conditions. The number of viable bacterial cells was determined by a spread plate method, and kill curves were performed. The results showed that photoactivated 1 mol% La/TiO2 exhibited a strong bactericidal effect, and in concentration, 1 mg/mL efficiently killed bacteria at an initial cell density of about 105 colony forming units in 1 mL within 15 min.

Pressure field assisted non-hydrolytic sol-gel in-situ synthesis of novel seed-pulp-structured C@ZrSiO4 pigments

Novel pressure field assisted non-hydrolytic sol-gel method is developed for the in-situ synthesis of novel seed-pulp-structured C@ZrSiO4 pigments. The obtained pigments, which are composed of in-situ carbon derived from leaving organic groups as core and zircon as shell, were characterized via DSC-TG, XRD, FT-IR, Raman, XPS, SEM, TEM, UV–Vis, and automatic colorimeters. It was found that the pressure field promotes the non-hydrolytic sol-gel heterogeneous polycondensation reaction and the direct transformation of reaction groups into in-situ spherical carbon. Meanwhile, the in-situ spherical carbon was enclosed by heterogeneous condensation bonds wrap and formed a dense structure. The as-prepared pigments exhibited excellent color rendering performance (L* = 21.07, a* = 0.48, b* = 0.75) and thermal stability.

Lowering the synthesis temperature of α‐Al2O3 by increasing the content of pentacoordinate aluminum in the precursors

Abstractα‐Al2O3, commonly known as corundum, plays a significant role in various industrial applications. Typically, the synthesis of α‐Al2O3 requires elevated temperatures exceeding 1200°C, which results in reduced specific surface area and increased particle size due to high‐temperature calcination. In this study, α‐Al2O3 powder was primarily investigated. The precursor was prepared by non‐hydrolytic sol‐gel (NHSG) method, employing alcohols and other nonaqueous oxygen donors in nucleophilic substitution reactions with AlCl3. The precursor was then processed by mechanochemical method, leading to the attainment of α‐Al2O3 at temperatures below 800°C. The resultant α‐Al2O3 was in the form of thin flakes, with significantly increased specific surface areas up to 27.9 m2/g. Upon characterizing the precursors post‐ball milling, a large amount of pentacoordinate aluminum was observed. The pentacoordinate aluminum has activated the alumina lattice and increased the phase transition rate, a key factor in the low temperature preparation of α‐Al2O3. This innovative approach not only simplifies the preparation process but also enables the production of high‐purity, large specific surface area lamellar α‐Al2O3 at lower temperatures, paving the way for more efficient and cost‐effective industrial processes.

Copper, potassium promoted iron on metallosilicate and aluminum oxide supports synthesized via a non-hydrolytic sol-gel for Fischer-Tropsch

We developed a promoted iron based catalyst that converts 20% more CO to diesel than the unpromoted counterparts. The synthesis involves a non-hydrolytic sol-gel method (NHSG) and 0.04 g g−1 copper and 0.02 g g−1 potassium as promoters. The iron catalyst supports included cerium and zirconium metallosilicates and Catalox and Dispal commercial aluminum oxides from Sasol. At 325 ∘C and 20 bar, CO conversion over the Fe/Ce/SiO2-K,Cu, exceeded 85% while at the same conditions it was only 68% over the unpromoted catalyst. Fe/Zr/SiO2-K,Cu converted less CO than the cerium-silicate (75%) but the unpromoted zirconium-silicate only converted 43% of the CO. The conversion and selectivity of the Catalox was about the same as the cerium-silicate, while the Dispal performance was equivalent to the zirconium-silicate. This study also highlights the importance of support and promoters in FTS, demonstrates the potential of the NHSG method to synthesize promoted iron catalysts with various supports and lays the foundation for developing efficient and stable catalysts for converting syngas to hydrocarbons.

Influence of Yb3+ percentage on emission of Er3+ doped into GdVO4 matrix

In this study, we used the non-hydrolytic sol–gel methodology to synthesize gadolinium vanadate particles doped with different Er3+ and Yb3+ molar ratios. Er3+ and Yb3+ chlorides and vanadium alkoxide were used as precursors during the sol–gel synthesis. The resulting powders were treated at 800 °C and characterized by x-ray diffraction and photoluminescence. The x-ray diffractogram displayed peaks attributed to the gadolinium vanadate matrix. Photoluminescence helped to evaluate the Fluorescence Intensity Ratio (FIR), which is important for understanding the nanothermometer property. The FIR of the GdVO4:Er3+/Yb3+ samples containing different Er3+ and Yb3+ molar ratios increased as a function of the laser power, which indicated that the local temperature increased. The excitation spectra obtained at fixed wavelengths of 525 and 555 nm displayed bands at 322, 379, and 489 nm, ascribed to the charge transfer band and Er3+ levels. Upon excitation at 321 nm, the emission spectra in the visible region presented intense bands at 525 and 555 nm, due to Er3+ emission, and excitation at 321 nm led to emission in the infrared region, 980 and 1550 nm. In conclusion, the synthesized system can be employed as a temperature sensor.

Non-hydrolytic sol-gel synthesis of BaTiO3 nano-powder: Effect of calcination temperature and modified titanium source on particles

In this study, BaTiO3 nanopowders were prepared by non-hydrolytic sol-gel (NHSG) method using barium acetate and tetrabutyl titanate (TBT) as precursors and acetylacetone (Hacac) as additive. The effects of acetylacetone modification and calcination temperature on nanoparticle size and crystalline phase were evaluated. The products were analysed by SEM, TEM, DSC/TG, FTIR, XRD, Raman. FTIR analysis showed the formation of Ba-O-Ti bond at the sol stage of the NHSG method. DSC/TG and XRD analyses showed that BaTiO3 was produced at 500 ℃. According to SEM/TEM, the particle size of the powder becomes larger as the temperature increases, meanwhile the addition of acetylacetone can make the final product particle size decrease. Raman analysis showed that BaTiO3 has the presence of tetragonal phase, so the crystalline phases of the product and impurities were analysed by XRD refinement, and the results showed that the relative content of tetragonal phase of BaTiO3 was linearly correlated with the calcination temperature.

Synthesis, chloride-ion diffusion mechanisms, and anisotropic sintering of 2D layered erbium oxychloride nanoplatelets

Ligand-passivated ErOCl nanocrystals have been synthesized using a non-hydrolytic sol–gel method. Anisotropic sintering of ErOCl nanocrystals enhances 2D chloride-ion diffusion along the ab plane, yielding a promising candidate for halide batteries.

Plasmonic effect on the emission intensity of Ce3+ ions doped zirconia-silicate glass

Ce3+:SiO2-ZrO2 samples doped with and without plasmonic nanoparticles of copper were prepared by the easy and economic non-hydrolytic sol–gel method. Structural, morphological, and optical studies were done on the samples after being dried at room temperature and annealed at 800 °C. Fourier transform infrared (FTIR) spectra confirms the formation of the host glass SiO2-ZrO2 from the asymmetric stretching of Si-O-Zr bond. Tetragonal ZrO2 and plasmonic copper nanoparticles formation was affirmed from the X-ray diffraction (XRD) spectra. Transmission electron microscopy (TEM) confirms the formation of plasmonic nanoparticles of copper. UV/Visible spectra show an absorption around 330 nm. The photoluminescence (PL) spectra show emission centered around 469 nm; an enhancement in the PL intensity occurred due to the localized surface plasmon resonance (LSPR) effect of the plasmonic nanoparticles of copper.

Color tunability studies of samarium ions/silver nanoparticles doped titanosilicate glass matrix

The current study aims at synthesizing a titanosilicate glass composite doped with rare earth/plasmonic nanoparticles using a cost effective and easier method of non-hydrolytic sol gel method. The rare earth employed is samarium ions while the plasmonic nanoparticle used is Silver. For densification samples were annealed at 800 0C and further characterized by FTIR, XRD, TEM. Matrix confirmation is done by FTIR spectroscopic studies which confirm the presence of Si-O-Si, Si-O, and Ti-O-Ti bonds. Both XRD and TEM analysis affirm the presence and morphology of Ag and TiO2 nanoparticles respectively. In the photoluminescence analysis the trivalent samarium ions show strong reddish-orange luminescence in the 550–670 nm range. The major peaks are obtained at 581 nm, 662 nm, 605 nm. Each of the spectra obtained show three prominent characteristic emission bands correlated to the transitions 4G5/2 to 6H5/2, corresponding to 581 nm, 4G5/2 to 6H7/2 corresponding to 605 nm, and 4G5/2 to 6H9/2 corresponding to 662 nm. We successfully plotted the CIE colorimetry diagram and it is observed that the effect of plasmonic nanoparticles can tune the relative emission intensity of rare earth ions in CIE colorimetry. Our study highlights the significance of incorporating the rare earth ions doping with plasmonic nanoparticles in the color tunability studies, exhibiting their broad applications in LED devices.

Preparation of HfSiO4 via Non-Hydrolytic Sol-Gel method at low temperatures

Hafnon (HfSiO4) can be applied in electronics, dielectric films, refractory materials, and many other critical application areas. To explore an efficient preparation process of HfSiO4, a novel non-hydrolytic sol-gel (NHSG) method was used to synthesize high-purity HfSiO4 in this study. X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS), thermogravimetric differential scanning calorimetry (TG-DSC), Fourier transform infrared spectroscopy (FT-IR), and infrared thermal imaging (ITI) were used to investigate the synthesis temperature and mechanism of HfSiO4 and the effects of process parameters on its synthesis efficiency. The results show that the prepared sols undergo a highly reactive non-hydrolytic polycondensation reaction at room temperature. High temperature reflux or long time aging step is not necessary to form the strong Hf-O-Si bonds. Furthermore, with the introduction of the mineralizer agent LiF, the synthesis temperature of HfSiO4 can be drastically reduced, and the HfSiO4 with high purity can be synthesized at low temperatures. A moderate molar ratio of silicon to hafnium (Si:Hf) and molar concentration of the solution contribute to improve the synthesis efficiency of HfSiO4, and the purity of HfSiO4 products can reach up to 98.12 %.

Solids containing Si-O-P bonds: is the hydrolytic sol-gel route a suitable synthesis strategy?

AbstractMaterials based on silicon-phosphorus mixed oxides have traditionally attracted interest in electronics, optics, catalysis, and related fields. The preparation of a solid containing stable Si–O–P linkages is a huge challenge due to their intrinsic instability to hydrolysis in a wet atmosphere. On the other hand, most technological applications of these materials, such as protonic conductive membranes in fuel cells and water-tolerant solid acid catalysts, are related to their interaction with water; consequently, suitable synthesis procedures that positively face this tradeoff are mandatory. Besides the traditional high-temperature techniques, sol-gel synthetic methods represent a viable, low-cost alternative, allowing for the preparation of high-purity materials with a homogeneous distribution of the components at the atomic scale. Si–O–P linkages are easily obtained by nonhydrolytic sol-gel routes, but only in inert and dry atmosphere. Conversely, hydrolytic routes offer opportunities to control the structure of the products in a wide range of processing conditions. The present review aims at providing an overall picture of the research on the sol-gel synthesis of phosphosilicate and related materials and theisr different applications, emphasizing how the interest in these systems is still lively, considering both conventional and emerging applications, such as flame retardance. The incorporation of Si–O–P nanostructures in polymer composites, coatings, and textiles is indeed a promising strategy to improve properties like thermal stability and fire resistance; however, their in-situ synthesis brings about additional difficulties related to the reactivity of the precursors. The perspectives linked with the development of Si–P-based materials are finally outlined. Graphical Abstract

Non-hydrolytic sol-gel synthesis of zirconium phosphonates with controlled mesoporosity

We disclose the preparation of high-surface-area mesoporous zirconium phosphonates by the non-hydrolytic sol-gel reactions (NHSG) of Zr(NEt2)4 with trimethylsilylated phosphonates RP(O)(OSiMe3)2 (R = Me, tBu, Ph, OSiMe3), and bis-phosphonates (Me3SiO)2(O)P–X–P(O)(OSiMe3)2 (X = CH2, C6H4, CH2(C6H4)CH2, and CH2(C6H4)2CH2) in dry toluene under ambient pressure. Zirconium phosphonate xerogels are prepared by condensation reaction with the elimination of silylamine Me3SiNEt2. This irreversible reaction provides the amorphous xerogels and drives the formation of the porous structure. The influence of organic moieties bonded to phosphorus atoms on porosity was examined in this study. The final surface area of dried xerogels reached 720 m2 g−1 without any extra templating agent. Xerogels were characterized by 13C, 29Si, and 31P solid-state NMR to define atomic homogeneity and evidence the presence of organic phosphonate substituents and residual amido and trimethylsilyl groups. The amount of residual reactive groups was determined by gravimetric measurements and the thermal analysis (TG-DSC) method. These groups may be applied in post-synthetic surface modification, such as controlling the hydrophobic/hydrophilic properties.The catalytic properties of NHSG-prepared xerogels were tested on a model reaction of aminolysis of styrene oxide in a batch mode employing relatively bulky molecules. Products were identified and quantified by the 1H NMR spectroscopy. Catalyst performance parameters, such as selectivity, conversion, turnover frequency, and others, were exceeded compared to benchmark microporous layered zirconium phosphonate catalysts.

Non-hydrolytic Sol–Gel Routes to Bifunctional Cu–Ta–SiO2 Catalysts for the Upgrading of Ethanol to Butadiene

Non-hydrolytic Sol–Gel Routes to Bifunctional Cu–Ta–SiO₂ Catalysts for the Upgrading of Ethanol to Butadiene

#5333 IMPROVING AUTOPHAGY FLUX BY TFEB ACTIVATION WITH CERIA NANOPARTICLES ATTENUATED CHRONIC KIDNEY INJURY IN CELLULAR AND ANIMAL MODELS OF FABRY DISEASE

Abstract Background and Aims Fabry disease (FD) is a lysosome storage disease (LSD) characterized by significantly reduced intracellular autophagy function. This contributes to the progression of intracellular pathologic signaling and can lead to organ injury. Phospholipid–polyethyleneglycol-capped Ceria-Zirconia antioxidant nanoparticles (PEG-CZNPs) have been reported to enhance autophagy flux. We accessed the action mechanisms of PEG-CZNPs in autophagy regulation and checked the effect on chronic kidney injury in cellular and animal models of FD. Method PEG-CZNPs were synthesized using a non-hydrolytic sol-gel reaction method. HK-2 cells were transfected with α-galactosidase A (α-GLA) shRNA for permanent cellular model of FD. For in-vivo study 4-week-old male B6;129-Glatm1Kul/J mice were treated for 48 weeks with 10mg/kg of PEG-CZNPs twice per week via intraperitoneal injection. PCR, immunoblotting, immunoflouresce assay, electron microscopy analysis, ICP-MS, biochemical and histological analysis were done Results TFEB tanslocated to the nucleus by treatment with PEG-CZNPs. Autophagy flux was evaluated with chloroquine. Autophagy flux was enhanced by PEG-CZNPs treatment. To show whether TFEB plays the important role in autophagy flux, we transfected HK-2 cells with siTFEB. Autophagy flux significantly decreased after knockdown of TFEB with PEG-CZNPs treatment. We next assessed upper signaling pathway of TFEB by PEG-CZNPs. TFEB dephosphorylation was independent of both mTOR and ERK but GSK3ß signaling pathway showed massive impact on TFEB dephosphoryation by PEG-CZNPs. PEG-CZNPs decrease intracellular globotriaosyceramide (Gb3) accumulation and decreased the levels of Collagen type IV, αSMA and MMP9 expression in cellular model of FD. Gb3 levels were significantly reduced in the kidney tissues and the levels of Fibronectin, Collagen type 4 and αSMA was decreased by PEG-CZNPs in animal model of FD. Conclusion These results suggested PEG-CZNPs promote autophagy flux through GSK3ß -TFEB signaling pathways, showed the beneficial effect on renal fibrosis in cellular and animal models of FD. It thus provided a new insights of the potential therapeutics on FD.

Low-temperature synthesis of ultrafine Cr,Mg-codoped Al2TiO5 nanocrystals as high-temperature green ceramic pigment

Tialite (Al2TiO5) is attracting as a high-temperature ceramic host matrix, but the decomposition of Al2TiO5 at 780–1280 °C is a serious obstacle for practical application. Herein we prepared successfully ultrafine Cr,Mg-codoped Al2TiO5 green ceramic pigment with the nanocrystal sizes less than 50 nm and high-temperature stability of up to 1200 °C via nonhydrolytic sol-gel (NHSG) method followed by heating treatment of 750 °C. The effects of Cr and Mg content on phase composition, crystal structure, thermal stability and color property were well investigated. The optimum Cr,Mg-codoped Al2TiO5 pigment with 20 mol% Mg and 6 mol% Cr exhibited an excellent green color (L* = 76.94, a* = −9.62, b* = 14.17), which can be reasonably maintained in exposed air by a heating treatment at 1200 °C for 10 h or in transparent ceramic glaze at 1200 °C for 30 min. These enhanced performances were mainly attributed to synergistic effect of Cr and Mg doping, which hindered the tendency of Al2TiO5 toward decomposition, indicative of its potential application in high-temperature ceramic decoration.