Modified Sol Gel Method Research Articles

Pure monoclinic n-BiVO4 prepared by modified sol–gel method for high efficiency photodegradation of methylene blue under solar light irradiation

Pure monoclinic n-BiVO4 prepared by modified sol–gel method for high efficiency photodegradation of methylene blue under solar light irradiation

Enhancing Thermochemical Energy Storage Performance of Perovskite with Sodium Ion Incorporation

Perovskite materials are promising for thermochemical energy storage due to their ability to undergo redox cycling over a wide temperature range. Although BaCoO3 exhibits excellent air cycling properties, its heat storage capacity in air remains suboptimal. This study introduces Na into the lattice structure to enhance oxygen vacancy formation and mobility. DFT+U simulations of the surface structure of Na-doped BaCoO3−δ indicate that incorporating Na improves surface stability and facilitates the formation of surface oxygen vacancies. NaxBa1−xCoO3−δ compounds were synthesized using a modified sol–gel method, and their properties were investigated. The experimental results demonstrate that Na doping significantly enhances the redox activity of the material. The heat storage capacity increased by above 50%, with the Na0.0625Ba0.9375CoO3−δ solid solution achieving a heat storage density of up to 341.7 kJ/kg. XPS analysis reveals that Na doping increases the concentration of surface defect oxygen, leading to more active oxygen release sites at high temperatures. This enhancement in redox activity aligns with DFT predictions. During high-temperature cycling, the distribution of Na within the material becomes more uniform, and no performance degradation is observed after 300 cycles. Even after 450 cycles, Na0.0625Ba0.9375CoO3−δ retains over 96% of its initial redox activity, significantly outperforming fresh BaCoO3−δ. These findings elucidate the mechanism by which Na doping enhances the thermochemical heat storage performance of BaCoO3−δ and provide new insights for the design of perovskite-based materials.

Investigation of rare earth metal ions (Sm and Er) doped CoMoO4 polymorphs for photocatalytic dye degradation

Cobalt molybdate (CoMoO4) and its rare earth doped variants have emerged as promising photocatalysts for degrading dye pollutants in wastewater. The photocatalysts were prepared using a modified sol-gel method, employing ammonium heptamolybdate tetrahydrate and cobalt (II) nitrate hexahydrate as precursors. The incorporation of samarium and erbium as a dopant was hypothesized to improve the photocatalytic activity of CoMoO4 by altering its band structure and creating defect sites for improved dye adsorption and degradation. The structural and optical properties of the synthesized photocatalysts were characterized using various techniques. The photocatalytic performance of CoMoO4, Sm:CoMoO4 and Er:CoMoO4 was evaluated by monitoring the degradation of MB dye under light irradiation. The results reveal that Sm:CoMoO4 and Er:CoMoO4 catalysts achieve a degradation efficiencies of 99 % and 97 %, respectively, highlighting the potential of rare earth-doped CoMoO4 as an efficient photocatalyst for the remediation of dye contaminated wastewater.

Efficient Degradation of Ofloxacin by Magnetic CuFe2O4 Coupled PMS System: Optimization, Degradation Pathways and Toxicity Evaluation.

Magnetic CuFe2O4 was prepared with the modified sol-gel method and used for enhanced peroxymonosulfate (PMS) activation and ofloxacin (OFL) degradation. The OFL could almost degrade within 30 min at a catalyst dosage of 0.66 g/L, PMS concentration of 0.38 mM, and initial pH of 6.53 without adjustment, using response surface methodology (RSM) with Box-Behnken design (BBD). In the CuFe2O4/PMS system, the coexisting substances, including CO32-, NO3-, SO42-, Cl- and humic acid, have little effect on the OFL degradation. The system also performs well in actual water, such as tap water and surface water (Mei Lake), indicating the excellent anti-interference ability of the system. The cyclic transformation between Cu(II)/Cu(I) and Fe(III)/Fe(II) triggers the generation of active radicals including SO4•-, •OH, •O2- and 1O2. The OFL degradation pathway, mainly involving the dehydrogenation, deamination, hydroxylation, decarboxylation and carboxylation processes, was proposed using mass spectroscopy. Moreover, the toxicity assessment indicated that the end intermediates are environmentally friendly. This study is about how the CuFe2O4/PMS system performs well in PMS activation for refractory organic matter removal in wastewater.

Quantum yield and thermal sensitivity of SrGd2O4:Yb, Tm up-conversion nanoparticles

Luminescence thermometry is an effective method for temperature measurements using the remote operating mode. In this work, a series of Tm3+ (1 at%) and Yb3+ (2, 4, and 6 at%) ions doped SrGd2O4 up-conversion (UC) nanoparticles were synthesized by the modified sol-gel method, and fully characterized toward optimization of their composition and optical characteristic. Crystallization of single-phase nanoparticles with homogeneous doping was confirmed by XRPD, TEM/HRTEM, and STEM/EDS analysis in all samples, independently of their stoichiometry. The UC emissions recorded under 976 nm excitation revealed typical Tm3+ transitions, showing that the optimal sensitizer doping concentration is 4 at%. For this sample, a lifetime of 342 μs, and a total quantum yield of 1.12 % were determined at room temperature for the emission observed in the Vis part of up-conversion spectra. The temperature-dependent emission spectra, measured from 263 to 363 K, implied its excellent temperature-sensing capabilities. The luminescent intensity ratio (LIR) was employed for blue I479/485 and IR I795/807 Tm3+ emissions. The absolute and relative temperature sensitivity continuously decreases with the increase of the temperature, showing the values of 4.05x10−3 K-1 and 0.41 % K−1 (for blue) and 3.8x10−3 K-1 and 0.31 % K−1 (for IR) at the temperature of 300 K. The results indicate that SrGd2O4 doped with 4 % Yb3+ and 1 % Tm3+ may be employed for reliable temperature measurement over an investigated temperature range.

Optimization of furfural production from xylose over sulfated titanium-niobium mixed oxides catalyst in biphasic system

The present study investigates the use of SO42-/TiO2Nb2O5 (STNO) catalyst prepared through the modified sol-gel method in the process of xylose dehydration to furfural. The reaction was carried out in a biphasic solvent consisting of toluene and water. The catalyst used in this study was subjected to several characterization methods, including Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The textural properties of the catalyst were evaluated by conducting N2 adsorption and desorption measurements using the Brunauer-Emmett-Teller (BET) method. The impact of catalyst dosage, resident time, xylose concentration, and reaction temperature in the dehydration of xylose to produce furfural was explored. The study employed response surface methodology to identify the optimal operational parameters that would result in the highest furfural selectivity. At a reaction temperature of 150 °C and a reaction time of 180 min, a maximum conversion of xylose of 98 mol%, furfural selectivity of 74 mol%, and a furfural yield of 63 mol% was obtained. The activation energy for the synthesized catalyst was determined to be 26.7 KJ/mol. The results of this investigation show the great potential that sulfated titanium-niobium mixed oxides have in transforming biomass resources into value-added compounds.

Preparation and adsorptive performance study of amino modified-crosslinked composite aerogel for VOCs in wooden furniture

Abstract There is a lack of standards for harmful VOC substances in furniture products in China, and furniture’s peculiar smell is still a hot concern for society. Amino modified-crosslinked composite aerogel was prepared using a modified sol-gel method by incorporating chitosan and inorganic silica as the inorganic phase, and it was added to polyurethane coating (PU paint) and wooden substrate. Results indicated that the prepared amino modified-crosslinked composite aerogel had a pore size of 12 μm to 16 μm, retaining the lightweight structure and mesoporous characteristics of the gel while containing the active organic groups of chitosan. It exhibited a certain adsorption capacity for VOCs in both PU paint and wooden substrate, with the highest adsorption efficiency observed in fir, reaching 72.86%. These results demonstrate the feasibility of this method and suggest a new approach to pollution prevention and control in wooden furniture. It holds promising potential for scalable applications.

Cobalt-doped ZnO nanoparticles and PLD-deposited thin film forms: structure, optical properties and nature of magnetic anisotropy.

Cobalt-doped zinc oxide nanoparticles (NPs) were synthesized using a modified sol-gel method. Thereafter, the obtained powder was deposited on a Suprasil glass substrate by employing a pulsed laser deposition (PLD) technique. X-ray diffraction analysis with Rietveld refinement confirmed a hexagonal wurtzite ZnO phase belonging to the P63 mc space group for both samples in the NP and thin film forms. In particular, the thin film exhibited an intensive (002) XRD peak, indicating that it had a preferred c-axis orientation owing to the self-texturing mechanism. No segregated secondary phases were detected. The crystallite structure, morphology, and size were investigated using high-resolution transmission electron microscopy (HRTEM). To study the crystalline quality, structural disorder, and defects in the host lattice, we employed Raman spectroscopy. UV-vis-NIR spectroscopy was performed to confirm the nature of the Co-doped ZnO NP powder and the film. The chemical states of oxygen and zinc in the thin film sample were also investigated via X-ray photoelectron spectroscopy (XPS). The M-T curve could be successfully fitted using both the three-dimensional (3D) spin-wave model and Curie-Weiss law, confirming the mixed state existence of weak ferromagnetic (FM) and paramagnetic (PM) phases. Magnetic interaction was quantitatively studied and explained by polaronic percolation of bound magnetic polarons (BMPs). Analysis of magnetic symmetry of the topological antiferromagnetic as-deposited thin film using torque measurements was performed. Based on a phenomenological model, it was revealed that the structure gives rise to uniaxial magneto-crystalline anisotropy (UMA) with the magnetic easy axis parallel to the c-axis.

Enhanced Photocatalytic Performance under Ultraviolet and Visible Light Illumination of ZnO Thin Films Prepared by Modified Sol-Gel Method.

Semiconductor oxides are frequently used as active photocatalysts for the degradation of organic agents in water polluted by domestic industry. In this study, sol-gel ZnO thin films with a grain size in the range of 7.5-15.7 nm were prepared by applying a novel two-step drying procedure involving hot air treatment at 90-95 °C followed by conventional furnace drying at 140 °C. For comparison, layers were made by standard furnace drying. The effect of hot air treatment on the film surface morphology, transparency, and photocatalytic behavior during the degradation of Malachite Green azo dye in water under ultraviolet or visible light illumination is explored. The films treated with hot air demonstrate significantly better photocatalytic activity under ultraviolet irradiation than the furnace-dried films, which is comparable with the activity of unmodified ZnO nanocrystal powders. The achieved percentage of degradation is 78-82% under ultraviolet illumination and 85-90% under visible light illumination. Multiple usages of the hot air-treated films (up to six photocatalytic cycles) are demonstrated, indicating improved photo-corrosion resistance. The observed high photocatalytic activity and good photo-corrosion stability are related to the hot air treatment, which causes a reduction of oxygen vacancies and other defects and the formation of interstitial oxygen and/or zinc vacancies in the films.

Regenerable Ni-Au/La2O3 catalysts for dry reforming of methane

Dry reforming of methane (DRM) has been proposed as an effective way of converting CO2 and CH4, two major greenhouse gases, into synthesis gas (H2 + CO), a ubiquitous feedstock for various chemical industries. Ni-based bimetallic catalysts have been widely explored as an attractive route to improve DRM activity, selectivity, and stability. In this study, we synthesized LaNiO3 (LNO) and 1% Au-doped LaNiO3 (Au/LaNiO3 – A/LNO) using the modified sol-gel method. The material properties were studied using various characterization techniques, including XRD, BET, H2-TPR, TPO, STEM-HAADF with EDX mapping, Raman spectroscopy, and XPS. Ni nanoparticles with sizes ranging from 10 to 70 nm were successfully exsolved from the perovskite material after reduction at 800 °C. DRM activity of the reduced catalysts was probed from 400 to 800 °C. The Au-doped LNO exhibits significant enhancement in DRM activity at a lower temperature range (600–700 °C) compared to LNO. The A/LNO was also shown to retard coke formation and improve the selectivity for DRM. A computational study using density functional theory (DFT) reveals that the Ni3Au sites have a lower methane activation barrier due to the formation of NiAu alloy and the synergetic effect between Ni and Au.

Greenly engineered bimetallic Ag-ZnO nanohybrids for synergistic antibacterial enhancement

The escalating issue of infectious agents developing resistance to traditional antibiotics has spurred ongoing research into effective and broad-spectrum antimicrobial solutions. This study focuses on the fabrication of silver-zinc oxide Nanohybrids (A-ZnO-NHs) with varying silver content (1 %, 3 %, 5 %) using a simplified modified sol–gel method, further enhanced by a green synthesis approach utilizing orange peel extract for the generation of silver nanoparticles. The physicochemical characteristics of the A-ZnO-NCs were thoroughly examined. X-ray diffraction analysis verified the presence of Ag nanoparticles within the zinc oxide and scanning electron microscopy revealed the nanoscale silver particles uniformly distributed on the spherical zinc oxide nanoparticles. Transmission electron microscopy indicated that the Ag-ZnO-NCHs ranged in size from 10 to 20 nm. X-ray photoelectron spectroscopy analysis confirmed the formation of strong chemical bonds between the silver and zinc oxide surfaces in the nanohybrids. This study explored into the structural, morphological, and antimicrobial characteristics of the A-ZnO-NHs at different compositions. The bactericidal efficiency of the A-ZnO-NHs was assessed against both gram-positive and gram-negative bacterial strains. The impact of the A-ZnO-NHs on the cellular structure and chemical composition of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) was also explored. The findings revealed that the A-ZnO-NHs with 3 % silver content demonstrated higher antimicrobial activity against E. coli and S. aureus compared to other compositions and pure zinc oxide nanoparticles. The antimicrobial activity decreases when the concentration of silver increases because the silver particles agglomerate together, reducing their surface area and lessening their effectiveness as antibacterial agents, despite their potential for various applications.

Cobalt- and copper-doped NASICON-type LATP polymer composite electrolytes enabling lithium titania electrode for solid-state lithium batteries with high-rate capability and excellent cyclic performance

This study reports cobalt- and copper-doped NASICON-type Li1.5Al0.5Ti1.7(PO4)3 (LATP) polymer composite solid-state electrolytes (CSEs) enabling Li4Ti5O12 (LTO) electrode with high-rate capability and excellent cyclic performance for solid-state lithium batteries. The fast Li+ conductor of Co- and Cu-doped LATP powders was successfully synthesized through a modified sol-gel method followed by thermal calcination. The equivalent series resistance as the linear decreasing function of the dopant concentration can be viewed, whereas the ionic conductivity showed an increasing function of the dopant amount. This reveals that the dopant concentration plays a positive role in facilitating the ionic conduction, and the ionic conductivity achieves as high as 3.18 × 10−4 S cm−1 (Co-doping) and 2.99 × 10−4 S cm−1 (Cu-doping) at ambient temperature. The changes in lattice characteristics and microstructure that the Co and Cu doping rely on are responsible for the elevated conductivity. The solid-state cell equipped with LTO-supported CSEs demonstrated not only high-rate capability at 5C (with a capacity retention of 84.6 % compared to the original capacity at 0.2C), but also superior cyclic stability with excellent Coulombic efficiency (> 99.2 %) over 425 cycles using Co- and Cu-doped LATP ceramics. With the aid of fast Li+ NASICON-type ceramics, the CSEs establish a conductive ionic pathway that facilitates Li+ ionic transport within the electrolyte while reducing the interfacial electrolyte/electrode resistance in solid-state cells (Li||CSE||LTO).

Structural and microstructural properties of Al-doped NSMO manganites prepared through modified sol–gel method

Structural and microstructural properties of Al-doped NSMO manganites prepared through modified sol–gel method

Changes in microstructure, magnetocaloric effect and critical behavior of La0.8Sr0.2MnO3 manganites by K/Co doping

We prepared La0.8-xKxSr0.2Mn0.95Co0.05O3 (0 ⩽ x ⩽ 0.1) (LKSMCO) through the modified sol-gel method (S-G) and its structure. Then, the magnetic, magnetocaloric, and critical behavior were analyzed. LKSMCO was confirmed to be the rhombohedral structure within the R-3c space group (No.167) using transmission electron microscopy and X-ray diffraction. For validating the chemical composition of LKSMCO, X-ray photoelectron spectroscopy and EDS were applied, showing that K+ was successfully doped. Phase transition of LKSMCO from paramagnetic to ferromagnetic phase near Curie temperature (Tc) was confirmed with a Magnetic Property Measurement System (MPMS). Using normalization and Banerjee's criterion, LKSMCO was demonstrated to be the second-order magnetic phase transition (SOMPT). As shown from the applied magnetic field, the maximal magnetic entropy (−ΔSMmax) of LKSMCO near Tc was 3.87 J/(kg K) (x= 0.00), 4.28 J/(kg K) (x= 0.05) and 4.44 J/(kg K) (x= 0.10). We employed the Kouvel-Fisher approach (KF) and modified Arrott plots to confirm the values of γ, δ, and β. This indicates that critical exponents of LKSMCO were consistent with the Mean-filed model.

Photocatalytic activity under visible light of Ni:TiO2-NiTiO3 synthesized through a modified sol-gel method

Photocatalytic activity under visible light of Ni:TiO2-NiTiO3 synthesized through a modified sol-gel method

Metal-Doped NASICON/Polymer Composite Solid Electrolyte for Lithium Titania Anode in Lithium-Ion Batteries.

This study reports five types of metal-doped (Co, Cu, Sn, V, and Zr) NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP)/polymer composite solid electrolytes (CSEs) enabling Li4Ti5O12 (LTO) anodes to have high rate capability and excellent cycling performance. The high Li+-conductivity LATP samples are successfully synthesized through a modified sol-gel method followed by thermal calcination. We find that the cation dopants clearly influence the substitution of Al for Ti, with the type of dopant serving as a crucial factor in determining the ionic conductivity and interfacial resistance of the solid electrolyte. The CSE containing poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and Sn-LATP shows an ionic conductivity of 1.88 × 10-4 S cm-1 at ambient temperature. The optimum conductivity can be attributed to alterations in the lattice parameters and Li+ transport pathways owing to Sn doping. The solid-state cell equipped with the LTO-supported CSE containing Sn-LATP fillers demonstrates both excellent high rate capability at 5 C (with a capacity retention of 86% compared to the value measured at 0.2 C) and superior cycling stability, maintaining high Coulombic efficiency (>99.0%) over 510 cycles. These findings indicate that the proposed CSE is highly promising for use in solid-state lithium batteries with desirable charge-discharge properties and high durability.

Ultrathin High-Entropy Fe-Based Spinel Oxide Nanosheets with Metalloid Band Structures for Efficient Nitrate Reduction toward Ammonia.

Spinel oxides with tunable chemical compositions have emerged as versatile electrocatalysts, however their performance is greatly limited by small surface area and low electron conductivity. Here, ultrathin high-entropy Fe-based spinel oxides nanosheets are rationally designed (i.e., (Co0.2Ni0.2Zn0.2Mg0.2Cu0.2)Fe2O4; denotes A5Fe2O4) in thickness of ≈4.3nm with large surface area and highly exposed active sites via a modified sol-gel method. Theoretic and experimental results confirm that the bandgap of A5Fe2O4 nanosheets is significantly smaller than that of ordinary Fe-based spinel oxides, realizing the transformation of binary spinel oxide from semiconductors to metalloids. As a result, such A5Fe2O4 nanosheets manifest excellent performance for the nitrate reduction reaction (NO3 -RR) to ammonia (NH3), with a NH3 yield rate of ≈2.1mmol h-1 cm-2 at -0.5V versus Reversible hydrogen electrode, outperforming other spinel-based electrocatalysts. Systematic mechanism investigations reveal that the NO3 -RR is mainly occurred on Fe sites, and introducing high-entropy compositions in tetrahedral sites regulates the adsorption strength of N and O-related intermediates on Fe for boosting the NO3 -RR. The above findings offer a high-entropy platform to regulate the bandgap and enhance the electrocatalytic performance of spinel oxides.

Promoting effect and kinetic analysis of Fe-Co bimetallic doping on the LaMnO3 catalytic activity for methane combustion

To enhance the catalyst’s properties, a modified sol–gel method is developed in this study, and a unique perovskite catalyst, LaMnxFeyCo1-x-yO3, is successfully synthesized by doping Fe-Co into the lattice of LaMnO3. The catalytic activity of the synthesized catalysts is initially determined by applying them to methane oxidation. Then, the structural, chemical, and surface properties of these catalysts are systematically evaluated utilizing XRD, BET, O2-TPD, H2-TPR, SEM, and XPS analyses. The modified LaMn0.8Fe0.15Co0.05O3 is shown to exhibit excellent activity (T90 at 486.5 ℃) in methane catalytic combustion, comparable to several standard noble metal materials. Experimental findings indicate that such perovskite structures have a larger specific surface area, an elevated molar ratio of Mn4+, desirable low-temperature reducibility, and excellent oxygen mobility relative to the original LaMnO3. Meanwhile, more efficient electron transfer from Mn4+/Mn3+ redox cycles, as well as the emergence of oxygen defects, significantly contribute to the robust interaction between Fe-Co and LaMnO3. Further reaction kinetic analysis is conducted to determine changes in species components and identify possible catalytic pathways. Notably, Fe-Co co-doping leads to an improvement in the increase of lattice oxygen and CH4 adsorption. In addition, the MVK kinetic mechanism governs methane combustion over LaMn0.8Fe0.15Co0.05O3. This study provides new insights into enhancing energy conversion performance and efficient utilization of ventilation air methane (VAM) through the implementation of highly efficient perovskites.

Optoelectronic properties of fluorine and antimony-doped tin dioxide nanoparticles

Nano-sized tin dioxide SnO2 (TO) has garnered great potential for use in optoelectronic applications, gas sensors, and solar cell technology thanks to its unique properties. These properties can be further enhanced by altering dopants and crystallinity. To achieve these aims, we successfully synthesized nanoparticles of fluorine (F) and antimony (Sb) doped tin dioxide by using a modified sol-gel method. The synthesis process involved supercritical drying of ethyl alcohol. The effect of doping on TO sample microstructure, optical and electrical properties was studied, which is crucial to understanding its potential applications. The X-ray diffraction pattern reveals that the nanoparticles crystallized in the tetragonal rutile structure with a size varying from 22 to 25 nm depending on element doping. The structural analysis was further proved by Raman spectroscopy and FTIR investigations. The optical band gap energy decreases upon the doping, as evidenced by the Eg values of 3.88, 3.87, and 3.72 eV corresponding to, FTO, and ATO respectively. This result proves that our compounds are good candidates for optoelectronic applications. Further, the electrical properties proved the semiconductor behavior for all the samples. Its conductivity is thermally activated, with a decrease in activation energy observed upon the addition of dopants. Moreover, the temperature dependence of the exponents's’of the (ac) conductivity proves that the conduction mechanism varies with dopants. The decrease of s values for undoped and FTO samples revealed a dominant correlated barrier hopping, while the increase of ‘s’ for ATO confirmed the tunneling hopping mechanism. Furthermore, the representation of real and imaginary parts of impedance has also been analyzed. Thus, the obtained results open exciting opportunities for using these samples in many fields that foster the combination of optical and electrical properties.

TiO2–SiO2 nanocomposite via a novel sol-gel method with the addition of an energy monitoring device: Synthesized, characterization and anti-bacterial applications

The present paper successfully employs a modified sol-gel method to synthesize TiO2–SiO2 nanocomposites. By incorporating a hygrometer and energy monitoring devices, we achieved real-time monitoring of the drying process and optimized temperature control. Energy consumption during the drying process was observed, revealing that higher temperatures result in shorter drying times. The lowest energy consumption was recorded at 80 °C, while the optimal temperature, obtained from the conversion of the optimization diagram, occurred at 77 °C. Characterization was performed using different tools such as XRD, FT-IR analysis, XPS, FE-SEM-EDS, and HRTEM to determine the size and distribution of elements, crystal structure, and chemical bonds. Furthermore, an anti-bacterial test was conducted, revealing that the nanocomposite exhibited superior antibacterial properties against Staphylococcus aureus and Escherichia coli. Meeting the required standards, the TiO2–SiO2 nanocomposite produced by this method shows the potential to create a cleaner and more efficient environment in medical and industrial applications.