Search Results (2,363)

Double perovskites are represented by the formula A₂BB’O₆ and AA’BB’O₆. These materials have been synthesized using the solid-state reaction, sol–gel, Pechini, and hydrothermal methods. X-ray fluorescence, X-ray diffraction, magnetic measurements, transmission electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction, synchrotron X-ray diffraction, neutron powder diffraction, extended X-ray absorption fine structure, and Raman spectroscopy have been used for the characterization of double perovskites. X-ray diffraction, synchrotron X-ray diffraction, and neutron powder diffraction coupled with the Rietveld method determine the crystal structure of a sample. These materials present various properties and applications. The present review aims (i) to report a process to determine the symmetry, apparent size, and apparent strain using the Rietveld method; (ii) show how experimental characterization techniques complement each other in the investigation of double perovskites; (iii) describe how the synthesis method can help in the uncovering of double perovskites with improved properties; and (iv) exemplify some of the main applications of double perovskites. Full article

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine CAS: 1912-24-9) is a widely used herbicide that has been connected to a variety of negative human health and environmental effects. Various bacterial strains utilize a six-step enzyme cascade to fully degrade atrazine. The third step in this pathway, N-isopropylammelide aminohydrolase (AtzC), produces the first non-toxic intermediate, cyanuric acid. As such, AtzC, paired with enzymes catalyzing the first two steps in this pathway, triazine hydrolase (TrzN) and hydroxyatrazine (2-(N-ethylamino)-4-hydroxy-6-(N-isopropylamino)-1,3,5-triazine) N-ethylaminohydrolase (AtzB), can effectively degrade atrazine. All three of these enzymes were successfully encapsulated in tetramethyl orthosilicate (TMOS) gels using the sol–gel method, producing active biomaterials. These materials showed increased protection against proteolytic digestion by the endopeptidase trypsin, as well as increased thermal and pH stability when compared to their non-encapsulated counterparts. AtzB:sol and AtzC:sol also showed increased stability over time compared to soluble enzyme. A combination of all three biomaterials, TrzN:sol, AtzB:sol, and AtzC:sol, was shown to be effective at fully degrading 50 µM atrazine to cyanuric acid in just over an hour and a half, thus establishing a potential bioremediation enzyme cascade for atrazine. Full article

Environmental pollution and sustainability issues require environmentally friendly solutions. In this study, we synthesized copper oxide nanoparticles (CuO NPs) using a sol––gel method with Croton macrostachyus bark extract for application in environmental remediation and as an antimicrobial agent. The uncalcined CuO NPs (200 mg/mL) demonstrated strong antimicrobial activity, with inhibition zones of 22 ± 1.3 mm against Staphylococcus aureus and 11 ± 0.7 mm against Escherichia coli. Moreover, the nanoparticles efficiently catalyzed the reduction of 4-nitrophenol, achieving 98.79% degradation within 8 min (K_app = 0.507 min⁻¹). These findings show that CuO NPs synthesized from the extract of Croton macrostachyus provide a sustainable and efficient approach for addressing both environmental pollution and antibacterial resistance. Full article

Rare-earth oxides possess distinctive electronic configurations, tunable oxidation states, and inherent structural robustness, making them highly attractive for advanced energy storage applications. Among these, neodymium oxide (Nd₂O₃) stands out due to its high surface redox activity, structural stability, and favorable band alignment, enabling efficient charge storage in electrochemical devices. In this study, Nd₂O₃ electrodes were synthesized via a sol–gel method with systematically varied precursor concentrations (1 mM, 3 mM, and 5 mM) to elucidate the impact of synthesis on crystallinity, morphology, and electrochemical performance. X-ray diffraction (XRD) confirmed the formation of the hexagonal Nd₂O₃ phase, with the 3 mM sample (Nd-2) exhibiting the sharpest reflections, indicative of enhanced crystallinity and reduced lattice defects. X-ray photoelectron spectroscopy (XPS) revealed trivalent Nd species and both lattice and surface oxygen, providing abundant redox-active sites. Field Emission Scanning Electron Microscope (FE-SEM) showed Nd-2 possessed a hierarchically interconnected fibrous network decorated with fine granules, maximizing active surface area and facilitating rapid ion diffusion. Electrochemical testing demonstrated that Nd-2 achieved an areal capacitance of 20 F cm⁻², a diffusion-controlled pseudocapacitive contribution of ~84.9%, and retained 86.3% capacitance over 12,000 cycles. An asymmetric supercapacitor with Nd-2 and activated carbon delivered an energy density of 0.132 mWh cm⁻², power density of 1.8 mW/cm², and 81.1% capacitance retention over 7000 cycles. These results highlight the critical role of precursor concentration in tailoring structure and electrochemical performance, establishing Nd₂O₃ as a promising electrode for high-performance energy storage devices. Full article

Recently, the state of the art of aerogels (AGs) has been reviewed, reporting first on their classification, based on the chemical origin of their precursors and the different methods existing to prepare them. Additionally, AGs of inorganic origin (IAGs) were contemplated, deeply discussing the properties, specific synthesis, and possible uses of silica and metal oxide-based AGs, since they are the most experimented and patented AGs already commercialized in several sectors. In this second part review, IAGs are examined again, but chalcogenide and metals AGs (CAGs and MAGs) are debated, since they are still too little studied, patented, and marketed, despite their nonpareil properties and vast range of possible applications. First, to give readers unaware of the previous work on AGs, a background about IAGs, all their main subclasses have been reported and their synthesis, including sol–gel, epoxide addition (EA), and dispersed inorganic (DIS) methods, as well as procedures involving the use of pre-synthesized nanoparticles as building blocks, have been discussed. Morphology and microstructure images of materials prepared by such synthetic method have been supplied. Conversely, the methods needed to prepare CAGs and MAGs, topics of this study, have been debated separately in the related sections, with illustrative SEM images. Their possible uses, properties, and some comparisons of their performance with that of other AGs and not AG materials traditionally tested for the same scopes, have also been disserted, reporting several case studies in reader-friendly tables. Full article

Oily wastewater poses severe ecological and health threats, but conventional separation technologies have limitations like low efficiency or high energy consumption. Herein, two superwettable carbon fiber (CF)-based membranes were fabricated for efficient oil–water separation. Using CF (low cost, excellent mechanical stability) as the substrate, Cu-TiO₂@CF (superhydrophilic/underwater superoleophobic, renewable) was prepared via a deep ultraviolet (DUV)-assisted sol–gel method, and OTMS/Cu-TiO₂@CF (superhydrophobic/superoleophilic) was obtained by modifying Cu-TiO₂@CF with octadecyltrimethoxysilane (OTMS) via hydrothermal synthesis. Characterization showed Cu-TiO₂ coatings uniformly covered CF, with strong substrate bonding. Both membranes exhibited outstanding performance: Cu-TiO₂@CF achieved water fluxes of up to 79,839.6 L·m⁻²·h⁻¹ and >97.3% separation efficiency for four oil–water mixtures; OTMS/Cu-TiO₂@CF had a maximum oil flux of 86,593.4 L·m⁻²·h⁻¹ and >98.1% efficiency. Cu-TiO₂@CF regenerated via 10 min UV irradiation (restoring underwater oil contact angle to 153°), while OTMS/Cu-TiO₂@CF achieved recovery through the process of UV irradiation followed by OTMS re-modification. Both membranes maintained stable performance over 100 cycles, demonstrating considerable potential for engineering applications. Full article

In the present scenario, it is believed that the fabrication of cost-effective and environmentally friendly nanomaterials is of great significance for various optoelectronic and electrochemical applications. In the past few years, zinc sulfide and its composites with carbon-based materials, metal oxides, MXenes, metal–organic frameworks (MOFs) and other materials have been prepared for electrochemical applications. The ZnS-based materials exhibit good specific surface area, catalytic activity, and decent conductivity, which makes them promising materials for sensors and supercapacitors (SCs). In this review article, we briefly discuss the synthesis of ZnS using various methods, such as hydrothermal, microwave, sol–gel, electrochemical, and ultrasonication methods. Furthermore, ZnS and its composites for electrochemical sensors are reviewed. The limits of detection, sensitivity, stability, and selectivity of the reported sensors are discussed. Furthermore, studies based on ZnS and its composites for SC applications are reviewed. It was found that ZnS-based composites exhibit good electrochemical performance for SCs. The limitations and prospects of ZnS-based materials are also discussed. We believe that the present review article may be useful for researchers who are involved in the fabrication of ZnS-based materials for SCs and electrochemical sensing applications. Full article

A novel metal oxide catalyst, PdO_x/CuO-ST, was prepared by calcining a Pd-embedded CuBTC precursor and compared with a PdO_x/CuO-SG catalyst synthesized via a sol–gel method. Characterization results indicated that in both catalysts, Pd species were incorporated into the CuO lattice, forming synergistic interactions that lowered the reduction temperature of CuO. The PdO_x/CuO-ST catalyst exhibited superior catalytic activity in the oxidative carbonylation of phenol to diphenyl carbonate when calcined at low temperature, which was attributed to well-dispersed Cu atoms and enhanced Pd–Cu integration. However, high-temperature calcination led to catalyst sintering and the formation of surface-adsorbed oxygen species, which reacted with PdO on CuO to generate inactive Pd_xCu_yO phases, thereby reducing the active Pd²⁺ content and degrading catalytic performance. Under optimized reaction conditions (100 °C, 7 h, Pd/phenol molar ratio = 1/425, and 6.6 MPa), the PdO_x/CuO-ST catalyst achieved a maximum phenol conversion of 79.5% and a diphenyl carbonate selectivity of 84.5%. Stability tests revealed that although the catalyst structure remained intact, deactivation occurred due to Pd leaching and the reduction in active PdO to metallic Pd⁰. Full article

In recent years CO₂ reforming of methane has attracted great interest as it produces high CO/H₂ ratio syngas suitable for the synthesis of higher hydrocarbons and oxygenated derivatives since it is a way for disposing and recycling two greenhouse gases with high environmental impact, CH₄ and CO₂, and because it is regarded as a potential route to store and transmit energy due to its strong endothermic effect. Along with noble metals, all the group VIII metals except for osmium have been studied for catalytic CO₂ reforming of methane. It was found that the catalytic activity of Ni, though lower than those of Ru and Rh, was higher than the catalytic activities of Pt and Pd. Although noble metals have been proven to be insensitive to coke, the high cost and restricted availability limit their use in this process. It is therefore valuable to develop stable Ni-based catalysts. In this contribution, we show how their activity and coking resistivity are greatly related to the size and dispersion of Ni particles. Well-dispersed Ni nanoparticles were achieved by multistep impregnation on a mesoporous silica support, namely SBA-15, obtained through a sol-gel method, using acetate as a nickel precursor and keeping the Ni loading between 5% and 11%. Significant catalytic activity was obtained at temperatures as low as 450 °C, a temperature well below their deactivation temperature, i.e., 700 °C. For the pre-reduced samples, a CO₂ conversion higher than 99% was obtained at approximately 680 °C. As such, their deactivation by sintering and coke formation was prevented. To the best of our knowledge, no Ni-based catalysts with complete CO₂ conversion at temperatures lower than 800 °C have been reported so far. Full article

The manufacturing techniques, structural features, and optical attributes of titanium dioxide (TiO₂) nanoparticles are highlighted in this study. These nanoparticles are notable for their remarkable photocatalytic activity, cheap cost, chemical stability, and biocompatibility. TiO₂ consists of three polymorph structures: anatase, rutile, and brookite. Because of its electrical characteristics and large surface area, anatase is the most efficient for photocatalysis when exposed to UV light. The crystallinity, size, and shape of titania nanoparticles (NPs) are influenced by diverse production techniques. Sol-gel, hydrothermal, solvothermal, microwave-assisted, and green synthesis with plant extracts are examples of common methods. Different degrees of control over morphology and surface properties are possible with each approach, and these factors ultimately affect functioning. For example, microwave synthesis provides quick reaction rates, whereas sol-gel enables the creation of homogeneous nanoparticles. XRD and SEM structural investigations validate nanostructures with crystallite sizes between 15 and 70 nm. Particle size, synthesis technique, and annealing temperature all affect optical characteristics such as bandgap (3.0–3.3 eV), fluorescence emission, and UV-visible absorbance. Generally speaking, anatase has a smaller crystallite size and a greater bandgap than rutile. TiO₂ nanoparticles are used in gas sensing, food packaging, biomedical coatings, dye-sensitized solar cells (DSSCs), photocatalysis for wastewater treatment, and agriculture. Researchers are actively exploring methods like adding metals or non-metals, making new composite materials, and changing the surface to improve how well they absorb visible light. Full article

Vitamin-conjugated metallic nanoparticles (VC-MNPs) have emerged as a transformative platform in nanomedicine that combine the therapeutic potential of vitamins with the structural versatility of metal nanoparticles. They offer a dual advantage of targeted drug delivery and enhanced therapeutic efficacy, enabling precise intervention against infectious and malignant diseases. Vitamin conjugation facilitates receptor-mediated targeting, antioxidant enhancement, and improved biocompatibility, thereby strengthening therapeutic outcomes and reducing off-target effects. This review critically evaluates how vitamin functionalization modulates the synthesis, activity, and clinical translation of VC-MNPs. Diverse synthesis methods including chemical reduction, co-precipitation, sol–gel, and green approaches are evaluated, along with the influence of synthesis parameters on nanoparticle performance. The mechanisms underlying enhanced antimicrobial and anti-cancer efficacy are discussed, highlighting the contributions of vitamin functionalization to cellular uptake, redox balance and metabolic selectivity. Critical challenges in clinical translation are systematically assessed, including nanoparticle stability under physiological conditions, potential toxicity concerns, regulatory approval pathways, and manufacturing scalability requirements. Finally, the paper considers future perspectives, focusing on synthesis innovations, novel therapeutic targets, interdisciplinary collaborations, and pathways for clinical translation. Overall, VC-MNPs represent a promising next-generation platform for precision nanomedicine and sustainable therapeutic design. Full article

Silica aerogels are highly attractive due to their outstanding properties, including their low density, ultralow thermal conductivity, large porosity, high optical transparency, and strong sorption activity. However, their inherent brittleness has limited widespread applications. Constructing a robust, highly porous three-dimensional network is critical to achieving the desired mechanical properties in aerogels. In this study, we introduce a novel synthesis route for fabricating lightweight and mechanically strong aerogels by incorporating poly(ethylene-co-vinyl alcohol) (EVOH) through thermally induced phase separation (TIPS). EVOH exhibits upper critical solution temperature (UCST) behavior in a mixture of isopropanol (IPA) and water, which can be utilized to reinforce the silica skeletal structure. Robust aerogels were prepared via the sol–gel process and TIPS method, followed by supercritical CO₂ drying, yielding samples with bulk densities ranging from 0.136 to 0.200 g/cm³. N₂ physisorption analysis revealed a mesoporous structure, with the specific surface area decreasing from 874 to 401 m²/g as EVOH content increased from 0 to 80 mg/mL. The introduced EVOH significantly enhanced mechanical performance, raising the flexural strength and compressive strength to 0.545 MPa and 18.37 MPa, respectively—far exceeding those of pure silica aerogel (0.098 MPa and 0.74 MPa). This work demonstrates the effectiveness of the TIPS strategy for developing high-strength, low-density silica aerogels with well-preserved porosity. Full article

This study compares the structural, morphological, magnetic, and photocatalytic properties of a pure SiO₂ matrix, a ZnFe₂O₄-doped SiO₂ nanocomposite (both synthesized via the sol-gel method), and bulk ZnFe₂O₄ produced by thermal decomposition. Thermogravimetric analysis (TGA) reveals that metal oxalates form below 200 °C and decompose into metal oxides, which subsequently form ferrite. Fourier-transform infrared (FTIR) spectroscopy confirms the embedding of both undoped and ZnFe₂O₄-doped nanoparticles into the SiO₂ matrix at all investigated annealing temperatures. X-ray diffraction (XRD) consistently reveals the formation of crystalline ZnFe₂O₄, with the crystallite size increasing from 48 to 93 nm upon annealing. Atomic force microscopy (AFM) shows spherical ferrite nanoparticles surrounded by an amorphous layer, with particle growth observed at higher temperatures. Structural parameters derived from XRD (e.g., crystallite size, density, porosity, lattice constant, unit cell volume) and AFM (e.g., particle size, coating thickness) as well as magnetic parameters (saturation magnetization, remanence, anisotropy, coercivity) demonstrate clear dependence on both dopant presence and annealing temperature. Magnetic measurements reveal enhanced properties with increasing ferrite content and heat treatment, with a transition from superparamagnetic behavior at 700 °C to ferrimagnetic behavior above 1000 °C. Scavenger experiments confirmed the involvement of holes, hydroxyl radicals, and superoxide radicals in the photocatalytic process. The photocatalytic efficiency, as evaluated by the Rhodamine B degradation under visible light, highlights the promising potential of the obtained nanocomposite for advanced environmental and technological applications. Full article

In this work, we present the first report on the synthesis via the sol–gel method of a high-entropy (Fe_0.2Co_0.2Cu_0.2Ni_0.2Mn_0.2)Nb₂O₆ with columbite–orthorhombic structure. Polyvinylpyrrolidone (PVP), ammonium niobium oxalate, and equimolar amounts of Fe, Co, Cu, Ni, and Mn ions were used. The refinement of the XRD pattern showed the presence of niobate crystallites with an average size of 48.4 nm and a fraction of 7.6 wt% of a spinel-like phase. At temperatures below 5 K, the DC and AC magnetometry results revealed the presence of a ferromagnetic-like phase due to the niobate phase. The Mössbauer spectrum at 300 K showed a paramagnetic and two magnetically ordered components corresponding to the niobate and the spinel-like phases, respectively. The spectral components were typical of Fe³⁺, indicating the presence of cation vacancies. The elemental mapping obtained from EDS measurements showed compositional homogeneity. The XRF measurements confirmed a composition consistent with nominal values. These results confirm the feasibility of synthesizing entropy-stabilized columbite oxides via the sol–gel route, opening new opportunities for the design of multifunctional ceramics with tunable structural and magnetic properties for high-performance thermal barrier coatings and energy conversion applications. Full article

Tobacco extract contains numerous valuable components, among which nicotine possesses significant potential for high-value applications despite its well-known health risks. However, the efficient extraction of nicotine is challenging due to the complex composition of tobacco extracts and the limitations of conventional separation techniques. In this work, an integrally asymmetric nanofiltration membrane was developed via thermal cross-linking for highly efficient nicotine separation. A poly(aryl ether ketone) (PEK)-based ultrafiltration membrane was first prepared via non-solvent induced phase separation (NIPS), followed by controlled thermal cross-linking to tailor the membrane pore size toward the molecular weight of nicotine. To mitigate pore collapse and enhance flux, TiO₂ nanoparticles were incorporated in situ through a sol–gel method. The resulting thermally cross-linked membrane exhibited a molecular weight cut-off of ~180 Da, a nicotine rejection rate of 93.2%, and a permeation flux of 143 L/(m²·h)—representing a 259% increase over the control membrane. Moreover, the thermally cross-linked membranes demonstrated exceptional chemical stability in various organic solvents and extreme pH conditions. This work offers a feasible and sustainable strategy for fabric high-performance nanofiltration membranes for the targeted extraction of bioactive molecules from complex plant extracts. Full article