Modified Sol Gel Method Research Articles

Structure and phase transitions in niobium and tantalum derived nanoscale transition metal perovskites, Ba(Ti,MV)O3, M=Nb,Ta.

The prospect of creating ferroelectric or high permittivity nanomaterials provides motivation for investigating complex transition metal oxides of the form Ba(Ti, MV)O3, where M = Nb or Ta. Solid state processing typically produces mixtures of crystalline phases, rarely beyond minimally doped Nb/Ta. Using a modified sol-gel method, we prepared single phase nanocrystals of Ba(Ti, M)O3. Compositional and elemental analysis puts the empirical formulas close to BaTi0.5Nb0.5O3-δ and BaTi0.5Ta0.5O3-δ. For both materials, a reversible temperature dependent phase transition (non-centrosymmetric to symmetric) is observed in the Raman spectrum in the region 533-583K (260-310°C); for Ba(Ti, Nb)O3, the onset is at 543K (270°C); and for Ba(Ti, Ta)O3, the onset is at 533K (260°C), which are comparable with 390-393K (117-120°C) for bulk BaTiO3. The crystal structure was resolved by examination of the powder x-ray diffraction and atomic pair distribution function (PDF) analysis of synchrotron total scattering data. It was postulated whether the structure adopted at the nanoscale was single or double perovskite. Double perovskites (A2B'B″O6) are characterized by the type and extent of cation ordering, which gives rise to higher symmetry crystal structures. PDF analysis was used to examine all likely candidate structures and to look for evidence of higher symmetry. The feasible phase space that evolves includes the ordered double perovskite structure Ba2(Ti, MV)O6 (M = Nb, Ta) Fm-3m, a disordered cubic structure, as a suitable high temperature analog, Ba(Ti, MV)O3Pm-3m, and an orthorhombic Ba(Ti, MV)O3Amm2, a room temperature structure that presents an unusually high level of lattice displacement, possibly due to octahedral tilting, and indication of a highly polarized crystal.

Probing the structural and optical properties of Eu-doped LiAl5O8 using X-ray absorption and hard X-ray excited optical luminescence

X-ray absorption and hard X-ray excited optical luminescence were used to probe the structural and optical properties of LiAl5O8 doped with different Eu concentrations produced by the modified sol-gel method. X-ray diffraction studies revealed that all samples produced have a cubic spinel unit cell of LiAl5O8 and that some impurities of the EuAlO3 phase were observed at concentration limits of 4 and 5 %. Based on the XAS results, they show the stabilization of europium in both the trivalent and bivalent states and reveal that Eu3+ ion can stabilize both in distorted octahedral configurations (non-centrosymmetric) and in the form of pentagonal bipyramid sites. The XEOL spectra were excited at Eu LIII-edge is composed of typical emission peaks attributed to the emission of Eu3+ ions and contaminating ions (Cr3+ and Fe3+). An XEOL luminescence mechanism was also discussed based on the XEOL emission spectra.

Sulfate-functionalized ternary metal oxide/Polypyrrole nanocomposites: Synergistic enhancement in Photocatalytic, Corrosion inhibition, Magnetic, and Electrical properties

The effect of functionalization of conducting polymer/metal nanocomposites with sulfate functional groups on their physical, chemical, mechanical, optical, and electrical properties was investigated. Vanadium, Manganese, and Zinc oxide nanoparticles were prepared by the modified Sol-gel method. Conducting polymer, Polypyrrole was synthesized by the chemical oxidation method. Polypyrrole + ternary metal oxide nanocomposites were synthesized by in situ technique. The characterization of functionalized nanocomposites was carried by Raman spectroscopy, FTIR, UV–visible, magnetic, SEM, and XRD techniques. The photocatalytic, anticorrosive, magnetic, optical, and electrical properties of functionalized nanocomposites were investigated. The functionalized nanocomposites show 85 % corrosion inhibition efficiency. The functionalized nanocomposites degrade 87 % of the methyl blue dye in 120 min under UV light. The magnetic study shows the paramagnetic character of functionalized nanocomposites. The optical band gap of functionalized nanocomposites decreases to 0.5 eV, showing a high order of conductivity. The sulfate-functionalized ternary metal oxide/polypyrrole nanocomposites show synergistic enhancement in their photocatalytic, electrical, magnetic, and anticorrosive properties.

Effect of Co doping on the structure and magnetic properties of Bi0.8Ba0.2FeO3 nanoparticles

A series of Bi[Formula: see text]Ba[Formula: see text]Fe[Formula: see text]CoxO3 ([Formula: see text], 0.05, 0.10, and 0.15) samples were synthesized using the tartaric acid modified sol–gel method. The crystal structure of the prepared samples was analyzed by XRD, and the samples co-doped with Ba and Co were all rhombohedral distorted structures with the R3c space group. With an increase in the doping amount, a reduction in lattice parameters was observed along with crystallite sizes consistently being below 62[Formula: see text]nm. Mössbauer spectral analysis at room temperature reveals a good fit with two sextets and a doublet, all attributed to the Fe[Formula: see text] state. This suggests that the charge balance within the samples is maintained through the generation of oxygen vacancies in the system. The hysteresis loops of all samples revealed the weak ferromagnetic of the Co-doped Bi[Formula: see text]Ba[Formula: see text]FeO3 nanoparticles. With the increase in Co doping, the magnetic parameters such as saturation magnetization and coercive field significantly improved.

A Porous Fluoride-Substituted Bovine-Derived Hydroxyapatite Scaffold Constructed for Applications in Bone Tissue Regeneration.

Hydroxyapatite is widely used in bone implantation because of its similar mineral composition to natural bone, allowing it to serve as a biocompatible osteoconductive support. A bovine-derived hydroxyapatite (BHA) scaffold was developed through an array of defatting and deproteinization procedures. The BHA scaffold was substituted with fluoride ions using a modified sol-gel method to produce a bovine-derived fluorapatite (BFA) scaffold. Fourier-transform infrared spectroscopy and X-ray diffraction analysis showed that fluoride ions were successfully substituted into the BHA lattice. According to energy dispersive X-ray analysis, the main inorganic phases contained calcium and phosphorus with a fluoride ratio of ~1-2 wt%. Scanning electron microscopy presented a natural microporous architecture for the BFA scaffold with pore sizes ranging from ~200-600 μm. The BHA scaffold was chemically stable and showed sustained degradation in simulated-body fluid. Young's modulus and yield strength were superior in the BFA scaffold to BHA. In vitro cell culture studies showed that the BFA was biocompatible, supporting the proliferative growth of Saos-2 osteoblast cells and exhibiting osteoinductive features. This unique technique of producing hydroxyapatite from bovine bone with the intent of producing high performance biomedically targeted materials could be used to improve bone repair.

Facile synthesis of magnetic-fluorescent iron oxide-geothermal silica core/shell nanocomposites via modified sol–gel method

Facile synthesis of magnetic-fluorescent iron oxide-geothermal silica core/shell nanocomposites via modified sol–gel method

Highly Efficient Transformation of Tar Model Compounds into Hydrogen by a Ni-Co Alloy Nanocatalyst During Tar Steam Reforming.

Hydrogen (H2) production from coal and biomass gasification was considered a long-term and viable way to solve energy crises and global warming. Tar, generated as a hazardous byproduct, limited its large-scale applications by clogging and corroding gasification equipment. Although catalytic steam reforming technology was used to convert tar into H2, catalyst deactivation restricted its applicability. A novel nanocatalyst was first synthesized by the modified sol-gel method using activated biochar as the support, nickel (Ni) as the active component, and cobalt (Co) as the promoter for converting tar into H2. The results indicated that a high H2 yield of 263.84 g H2/kg TMCs (Tar Model Compounds) and TMC conversion of almost 100% were obtained over 6% Ni-4% Co/char, with more than 30% increase in hydrogen yield compared to traditional catalysts. Moreover, 6% Ni-4% Co/char exhibited excellent resistance to carbon deposition by removing the nucleation sites for graphite formation, forming stable Ni-Co alloy, and promoting the char gasification reaction; resistance to oxidation deactivation due to the high oxygen affinity of Co and reduction of the oxidized nickel by H2 and CO; resistance to sintering deactivation by strengthened interaction between Ni and Co, high specific surface area (920.61 m2/g), and high dispersion (7.3%) of Ni nanoparticles. This work provided a novel nanocatalyst with significant potential for long-term practical applications in the in situ conversion of tar into H2 during steam reforming.

Highly stable FeNiMnCaO catalyst for integrated CO2 capture and hydrogenation to CO

The integrated CO2 capture from flue gas and hydrogenation can be realized by the consecutive calcium-looping (CaL) and reverse-water–gas-shift (RWGS) reactions. However, the incompatibility between the catalysis and adsorption components aggravates the sintering and deactivation of metal particles and CaO base material during the high-temperature process. Herein, we prepared a highly efficient and stable FeNiMnCaO material via a modified sol–gel method for in situ CaL and RWGS reaction, exhibiting a CO2 adsorption capacity of 13.2 mmol g−1 at 40 cycles with 58.0 % CO2 conversion and 100 % CO selectivity at 700 °C. The highly-dispersed Fe and Ni species in the developed catalyst not only suppressed the sintering of MnCaO, but also synergistically benefited the RWGS reaction, where FeOx species promoted CO2 adsorption and metallic Ni facilitated H2 dissociation. The reaction followed the H-assisted association formate mechanism, in which adsorption of CO2 occurred at the FeOx-CaO interface with the aid of the hydroxyl surface groups to form bidentate bicarbonates, followed by dehydration to bidentate formate and decomposition to CO and H2O in the presence of Ni-dissociated reactive H* species.

Synthesis of Eu-doped K0.5Na0.5NbO3 ceramics and their luminescent and dielectric properties

K0.5Na0.5NbO3:xEu sol–gel powders and bulk samples were synthesized by means of a modified sol–gel method. Two types of samples were obtained via sintering at two temperatures. X-ray diffraction revealed the presence of the perovskite phase in materials obtained at both temperatures. Eu3+ emission and excitation studies were conducted to determine its luminescence response. For K0.5Na0.5NbO3:xEu sinters, the excitation spectra included narrow peaks in the VIS range due to the 5D0–7F1 and 5D0–7F2 relaxation processes. These transitions were indicative of the presence of Eu3+ at sites of low symmetry. Dielectric studies indicated that Eu2O3 affected the observed phase transitions. The influence of sintering temperature on structure and physicochemical properties was discussed.

Ce-doped MgO films on AZ31 alloy substrate for biomedical applications: preparation, characterization and testing

Magnesium ions, MgO nanoparticles and thin films, magnesium alloys and cerium compounds are materials intensively studied due to their corrosion protection, antibacterial and pharmacological properties. In this work, we have designed, prepared and investigated, novel thin films of MgO doped with cerium, deposited on Mg alloy (AZ31) for temporary implants, in order to enhance their life time. More precisely, we report on microstructure and corrosion behavior of MgO pure and doped with 0.1 at % Ce films, fabricated by sol–gel route coupled with spin-coating technique, on AZ31 alloy substrate. A modified sol–gel method that start from magnesium acetylacetonate, cerium nitrate and 2–methoxyethanol (as a stabilizer for the sol) was been used successfully for cerium doped MgO sol precursor preparation. The structure and morphology of the surface of the coatings, before and after immersion for 7–30 d in Hank’s solution at 37 °C, were characterized by x-ray diffraction (XRD), scanning electron microscopy, high-resolution transmission electron microscope, x-ray photoelectron spectroscopy and Fourier infrared transmittance spectrum (FT–IR). A comparison between the corrosion protection of undoped MgO and MgO doped with 0.1 at % Ce coatings on the AZ31 alloy substrate is performed by electrochemical tests and immersion tests using open circuit potential and electrochemical impedance spectroscopy in Hank’s solution, at 37 °C. The electrochemical results showed that the protection of the AZ31 alloy substrate against corrosion was better with the doped with 0.1 at % Ce MgO film deposited than with pure MgO coting. The investigations of the films after immersion in Hank’s solution, at 37 °C, for 7, 21 and 30 d indicated that the grown layer on the film is bone like apatite that suggests a good bioactivity of 0.1 at % Ce–doped MgO coating. Our work demonstrates that the performance corrosion protection of the biodegradable magnesium alloys used for orthopedic applications, in simulated physiological environments (Hank and Ringer) can be enhanced through coating with Ce3+ doped MgO sol–gel thin film.

Lithium and cobalt co-doped mesoporous bioactive glass nanoparticles promote osteogenesis and angiogenesis in bone regeneration.

Healing of severe fractures and bone defects involves many complex biological processes, including angiogenesis and osteogenesis, presenting significant clinical challenges. Biomaterials used for bone tissue engineering often possess multiple functions to meet these challenges, including proangiogenic, proosteogenic, and antibacterial properties. We fabricated lithium and cobalt co-doped mesoporous bioactive glass nanoparticles (Li-Co-MBGNs) using a modified sol-gel method. Physicochemical analysis revealed that the nanoparticles had high specific surface areas (>600m2/g) and a mesoporous structure suitable for hydroxyapatite (HA) formation and sustained release of therapeutic ions. In vitro experiments with Li-Co-MBGNs showed that these promoted angiogenic properties in HUVECs and pro-osteogenesis abilities in BMSCs by releasing Co2+ and Li+ ions. We observed their antibacterial activity against Staphylococcus aureus and Escherichia coli, indicating their potential applications in bone tissue engineering. Overall, our findings indicate the feasibility of its application in bone tissue engineering.

Effect of Pr and Mn co-substitution on Structural and Optical Properties of Bismuth Ferrite

One of the most recent developments in the area of modern optics arises due to perovskite materials. The ABO3 perovskite materials like bismuth ferrite is an appealing alternative for various optical devices. Hence, in the present study, Praseodymium (Pr) and Manganese (Mn) co-substituted bismuth ferrite ceramics are prepared by the modified sol-gel method and the correlation between structural and optical properties with the variation in co-substitution concentration has been investigated. Rietveld refinement of X-ray diffraction patterns demonstrates a structural phase change in crystal symmetry from rhombohedral to orthorhombic phase with the increase in concentration for x ≥ 0.025. Lattice deformation in the co-substituted samples is confirmed by Fourier Transform Infrared (FTIR) and Raman spectra. UV–vis diffuse reflectance spectra confirm the strong absorption of light in the visible region. Furthermore, optical energy band gap decreases from 1.95 eV to 1.50 eV with increase in concentration from x = 0.000 to x = 0.100. The refractive index attains the maximum value i.e. 6.16 for x = 0.025 whereas it drops to minimum value of 4.06 for x = 0.100. This demonstrates that the structural modification in bismuth ferrite can be used to tune its optical parameters for the device applications.

Synthesis of bioactive glass 60SiO2-33CaO-4P2O5-3Ag2O and its application in toothpaste

This work is related to the synthesis of silver-doped bioactive glass material 60SiO2-33CaO-4P2O5-3Ag2O by the modified sol-gel method based on hydrothermal reaction. Several physical-chemical methods such as TG-DSC, XRD, SEM, and TEM were used to evaluate the synthetic bioglass. TG-DSC shows that the processing temperature to form bioglass from dried gel is at 600 oC. XRD confirms the formation of silver crystalline phase on the amorphous phase of glass. SEM and TEM show the porous structure of the glass material containing nano-sized particles. Experiment with cells showed good biocompatibility of the bioglass material with the fibroblast L929 cell-line. Ag-doped bioglass material was mixed to make toothpaste with excellent antibacterial property. All Staphylococcus aureus and Pseudomonas aeruginosa bacteria were destroyed when exposed to toothpaste containing bioglass.

Efficient removal of methyl orange and ciprofloxacin by reusable Eu-TiO2/PVDF membranes with adsorption and photocatalysis methods.

The presence of methyl orange (MO) and ciprofloxacin (CIP) in wastewater poses a serious threat to the environment and human health. Titanium dioxide nanoparticles (TiO2 NPs) are widely studied as photocatalysts for wastewater treatment. However, TiO2 NPs have the drawbacks of high energy required for activation, fast electron-hole pair recombination and difficulty in recovering from water. To overcome these problems, europium decorated titanium dioxide/poly(vinylidene fluoride) (Eu-TiO2/PVDF) membranes were successful prepared in this work by combining the modified sol-gel method and the immersion phase inversion method. The Eu-TiO2/PVDF membranes obtained with the increase of Eu-TiO2 NPs content during the preparation process were named M1, M2 and M3, respectively. The pure PVDF membrane without the addition of Eu-TiO2 NPs was named M0, which was prepared by the immersion phase inversion method and served as a reference. The prepared Eu-TiO2/PVDF membranes could not only adsorb MO, but also degrade CIP under visible-light irradiation. Moreover, the Eu-TiO2/PVDF membranes exhibited adsorption-photocatalytic activity towards a mixture of MO and CIP under visible-light irradiation. Last but not the least, the Eu-TiO2/PVDF membranes exhibited excellent recyclability and reusability, opening the avenue for a possible use of these membranes in sewage-treatment plants.

Fabrication and characterization of novel ZnO-loaded mesoporous bioactive glass nanospheres with enhanced physiochemical properties and biocompatibility for bone tissue engineering

Novel ZnO-modified mesoporous bioactive glass nanospheres (MBNs) were developed by a modified sol-gel method and their physiochemical behavior and cytocompatibility were systematically evaluated. Compared to previous researches, an offered synthesis method resulted in much less compositional deviation between the nominal and real compositions, while retaining spherical shape and dispersion of the nanoparticles. The MBNs exhibited a higher specific surface area (280–343 m2/g) and a larger pore volume than various ZnO-loaded bioactive glasses prepared before. In contrast to most mesoporous bioceramics doped with ZnO, the current nanoparticles revealed an excellent bioactivity within 14 days immersion in simulated body fluid (SBF). Furthermore, an optimum ZnO content for enhanced viability of bone marrow mesenchymal stem cells cultured with ionic extracts of the nanoparticles is 0.5%. Thanks to a high particle dispersion, good textural properties, bioactivity, and high cytocompatibility, the prepared nanoparticles can be recommended as promising filler materials dental/bone tissue engineering.

A-site K-doped lanthanum manganite nanocrystalline La0.67Ba0.33MnO3 for room-temperature micro-scale magnetic cooling

Bulk nanocrystalline La0.67Ba0.33−xKxMnO3 (with x = 0, 0.05, 0.1, and 0.2) manganites have been prepared by the modified sol-gel method (Pechini). The single-phase rhombohedral crystal structure with the R-3c (no. 167) space group was verified by X-ray diffraction (XRD) and sustained by Rietveld refinement. As follows from the results of XRD structural analyses, the increase in K-doping triggers an increase in the distortion of the MnO6 octahedra, which eventually causes the narrowing of the eg bandwidth. Mn is in a mixed valence state of Mn4+/Mn3+ as inferred by X-ray photoelectron spectroscopy. Magnetic measurements confirm that the Curie temperature decreases from 348 K for La0.67Ba0.33MnO3 to 316 K for La0.67Ba0.13K0.20MnO3. The increasing of the Mn4+ ion concentration at the B-site sublattice and A-site ionic disorder (σ2) breaks up the double exchange interaction between the Mn3+ and Mn4+ ions. The ferromagnetic to paramagnetic second-order magnetic phase transition at TC is also confirmed by electron paramagnetic resonance. According to magnetic field-dependent magnetization isotherms at different temperatures, La0.67Ba0.13K0.20MnO3 shows a relatively large magnetocaloric effect (1400 mJ cm−3 K−1 at 316 K under 5 T applied magnetic field), which raises the possibility of using this material for room-temperature micro-scale magnetic cooling.

Phase Transformation and Photoluminescence Properties of MgTiO3:Mn4+ Synthesis by Modified Sol–Gel Method

Phase Transformation and Photoluminescence Properties of MgTiO3:Mn4+ Synthesis by Modified Sol–Gel Method

Signature of Superconductivity in Pressurized La4Ni3O10

The discovery of high-temperature superconductivity near 80 K in bilayer nickelate La3Ni2O7 under high pressures has renewed the exploration of superconducting nickelate in bulk materials. The extension of superconductivity in other nickelates in a broader family is also essential. Here, we report the experimental observation of superconducting signature in trilayer nickelate La4Ni3O10 under high pressures. By using a modified sol-gel method and post-annealing treatment under high oxygen pressure, we successfully obtained polycrystalline La4Ni3O10 samples with different transport behaviors at ambient pressure. Then we performed high-pressure electrical resistance measurements on these samples in a diamond-anvil-cell apparatus. Surprisingly, the signature of possible superconducting transition with a maximum transition temperature (T c) of about 20 K under high pressures is observed, as evidenced by a clear drop of resistance and the suppression of resistance drops under magnetic fields. Although the resistance drop is sample-dependent and relatively small, it appears in all of our measured samples. We argue that the observed superconducting signal is most likely to originate from the main phase of La4Ni3O10. Our findings will motivate the exploration of superconductivity in a broader family of nickelates and shed light on the understanding of the underlying mechanisms of high-T c superconductivity in nickelates.

Distinguishable photocatalytic activity of nano polyaniline with quantum dots metal oxide as photocatalysts for photodegradation of Dianix blue dye and different industrial pollutants

Nanopolyaniline (PAN) polymers have recently been under active investigation as promising photocatalysts. In this work, a simple modified sol–gel method is used to make nano PAN polymers, and a chemical polymerization method is used to make nano polyaniline titanium dioxide quantum dots (PAN-TiQD) polymers as an active photocatalyst during the photodegradation of Dianix blue dye as an organic pollutant under xenon light. The traditional colloidal sol–gel method and the microwave-assisted hydrothermal method were used to make TiQD, which was then mixed with nanoPAN to make PAN-5 % TiQD (W/W) nanocomposites. Characterizations like XRD, FTIR, UV and visible diffuse reflectance spectra, TGA, surface area, EDX, and TEM were used to characterize the nanoPAN and PAN-TiQD that were made. Also, the photocatalytic activity of all synthesized polymers was investigated by the photodegradation process of Dianix blue dye as an organic hazardous pollutant in aqueous medium using a xenon photoreactor with an initial power of 75 W/Cm2. The effects of irradiation time and photocatalyst type on the photodegradation process efficiency of Dianix blue dye were examined. After 3 h of photodegradation processes, the photodegradation efficiency of PAN-TiQD reached 69 % compared to 36 % of nanoPAN due to the fact that it contains 5 % TiQD as a highly active catalyst, which reached 91 %. As an added value for this study, a significant contribution is the examination of eight hazardous industrial wastewater samples, which were assessed under direct sunlight and were in accordance with the KSA environmental permissible limit of 1000 ppm.Finally, the recycling processes in the presence of all synthesized catalysts were investigated and evaluated six times. The photodegradation rate of the recycling processes of Dianix blue dye was highly decreased in the presence of nano PAN than PAN-TiQD, while it had a low decreasing percentage in the case of TiQD. The recycling process using sunlight for industrial pollution samples was investigated at one of the KSA textile plants by using six synthetic catalysts and assessing COD and TOC values.

Sodium Promoted FeZn@SiO2-C Catalysts for Sustainable Production of Low Olefins by CO2 Hydrogenation

A prepared FeZnNa@SiO2-C catalyst with graphitized carbon (C)-modified mesoporous SiO2 supports metal nanoparticles with the sol–gel method. The effect of adding metal Na and Zn promoters as a dispersion on the CO2 hydrogenation to low olefins was systematically studied. The results showed that Zn–Na, as a combination, could promote the absorption of CO2 and improved the conversion rate of CO2. Na as an alkaline substance can improve the absorption of more acidic CO2, which could increase the conversion rate of CO2 to 59.03%. Meanwhile, the addition of secondary metal Zn to Fe-based catalysts to form a surface alloy could alter the adsorption of CO2 and the activation of C-O bonds, inhibit the subsequent hydrogenation of olefins to paraffins, and facilitate the reduction of Fe2O3 and the formation of active Fe5C2 species. The formation of active Fe5C2 species was found in TEM and XRD, and the selectivity of the target product was 41.07%. The deep hydrogenation of olefins was inhibited, and the space–time yield (STY) of low olefins was raised again by inhibiting their deep hydrogenations, up to 0.0436. However, the corresponding STY did not increase infinitely with the increase of Na doping, and higher catalytic performance for CO2 hydrogenation could be exhibited when the Na doping reached 6.4%. Compared with Fe@SiO2-C catalyst, Na- and Zn-promoted Fe-based catalysts, prepared by the modified sol-gel method, can be used directly for highly efficient CO2 hydrogenation to low olefins and thus has a more promising application prospect in the future.