Core–shell nanoparticles (CSNs) have attracted considerable attention because of their promising applications in a wide range of fields. Recently, substantial efforts have been focused on the ...development of facile and versatile methods for preparing CSNs with mesoporous SiO2 or TiO2 shells because of their fascinating properties, such as high surface area, large pore channels and high pore volume. This Research News reviews the recent progress in facile, versatile and reproducible approaches which are simply extended from the well‐known Stöber method to construct mesoporous SiO2 and TiO2 shells for uniform multifunctional core–shell nanostructures. Several strategies, including the surfactant‐templating process, the long‐chain organosilane‐assisted approach, the phase transfer assisted surfactant‐templating process, and the kinetics‐controlled coating approach, are discussed. In addition, new trends in this field for the creation of multifunctional CSNs and novel nanostructures are highlighted.
The Stöber method is a well‐known and versatile process for synthesizing silica spheres with controllable particle size, narrow size distribution, smooth surface, and porosity. This contribution highlights recent advances on the extension of the Stöber method to construct mesoporous SiO2 and TiO2 shells for uniform multifunctional core–shell nanostructures.
•Fabrication of zinc ferrite thin film LPG and CO2 gas sensors.•Morphological growth of nanorods.•Significant advancement towards the fabrication of a reliable LPG sensor.•A new pathway to produce ...nanorods as sensorial material.
In the present communication, nanorods of zinc ferrite was synthesized and fabricated by employing sol–gel spin coating process. The synthesized material was characterized using X-ray diffraction, scanning electron microscopy, acoustic particle sizer, atomic force microscopy, UV–visible absorption and infrared spectroscopic techniques. Thermal properties were investigated using differential scanning calorimetry. The XRD reveals cubic spinel structure with minimum crystallite size 10nm. SEM image of the film shows porous surface morphology with uniform distribution of nanorods. The band gap of the zinc ferrite nanorods was found 3.80eV using the Tauc plot. ZnFe2O4 shows weak super paramagnetic behavior at room temperature investigated using the vibrating sample magnetometer. Further, the liquefied petroleum gas (LPG) and carbon dioxide gas (CO2) sensing properties of the fabricated film were investigated at room temperature (25°C). More variations in electrical resistance were observed for LPG in comparison to CO2 gas. The parameters such as lattice constant, X-ray density, porosity and specific surface area were also calculated for the better understanding of the observed gas sensing properties. High sensitivity and percentage sensor response, small response and recovery times, good reproducibility and stability characterized the fabricated sensor for the detection of LPG at room temperature.
ZnO nanoparticles (ZnO-NPs) were prepared by a sol–gel combustion method from a zinc acetate precursor and acetic acid. The ZnO-NPs were synthesized at calcination temperatures of 650 °C and 750 °C ...for 1 h. The synthesized ZnO-NPs were characterized by X-ray diffraction analysis (XRD) and TEM. The XRD results revealed that the sample product was crystalline with a hexagonal wurtzite phase. High-magnification transmission electron microscopy (TEM) showed single-crystal ZnO-NPs with nearly spherical shapes. The crystalline development in the ZnO-NPs was investigated by X-ray peak broadening. The Williamson–Hall (W–H) analysis and size–strain plot method were used to study the individual contributions of crystallite sizes and lattice strain on the peak broadening of the ZnO-NPs. The physical parameters such as strain, stress and energy density values were calculated more precisely for all the reflection peaks of XRD corresponding to the wurtzite hexagonal phase of ZnO lying in the range of 20°–100° from the modified form of the W–H plot assuming a uniform deformation model (UDM), uniform stress deformation model (USDM), uniform deformation energy density model (UDEDM) and by the size–strain plot method (SSP). The results obtained showed that the mean particle size of the ZnO-NPs estimated from the TEM, W–H analysis and the SSP method were highly intercorrelated.
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The synthesis of crystalline hydroxyapatite (HA) nanoparticles with expected microstructure is of primary importance because the process directly relates to the phase purity, morphology, and particle ...size of the final HA particles. In this work, different morphologies of HA powders were prepared via wet precipitation (HA–Wp) and sol–gel synthesis (HA–Sg) methods. The results showed that pure HA powders were successfully obtained via the two different methods, in which HA–Wp presented smaller crystallite size in accordance with the larger specific area compared with HA–Sg powders. A high surface area of 97.4m2g−1 was obtained in HA-Wp powder, whereas that of HA–Sg powder was 9.0m2g−1. Upon calcinations at 800–1000°C, the calcined powders were found to be Ca-deficient apatites as HA-Wp and HA–Sg powders decomposed to the secondary phase of β-TCP at 900°C and 1000°C, respectively. Microstructural analysis showed significant difference in terms of HA morphologies produced via the two methods. The HA-Wp powder consisted of nanoscale needle-like structures with soft agglomerated particles, whereas HA–Sg powder exhibited nanoglobular-like structures with hard agglomerated particles. The characteristics of nanocrystalline HA powder obtained from wet chemical precipitation is known to exhibit high surface activity as a bone substitute material.
Yttria dispersion-strengthened tungsten with both enhanced strength and ductility was synthesized through sol–gel method followed by sintering and high-temperature swaging. The sol–gel synthesis ...process involving a molecular-level doping leads to a unique nanostructure that Y2O3 nano-particles were homogeneously dispersed in tungsten grains interior. The nanosized Y2O3 particles in sol–gel synthesized W-1%Y2O3 are stable in size even under a high sintering temperature of 2300 °C. The swaged sol–gel W-1%Y2O3 show ductility at a relative low temperature of 250 °C, which is about 100 °C and 250 °C lower than that of spark-plasma-sintered sol–gel W-1%Y2O3 and ball-milling synthesized W-1%Y2O3, respectively. The sol–gel method provides a promising access to high-performance nanostructured tungsten materials with both high strength and ductility, and can be easily scaled for industrial production.
•Yttria dispersion-strengthened W was synthesized by sol–gel method plus swaging.•Y2O3 nano-particles were homogeneously dispersed in tungsten grains interior.•The nanosized Y2O3 particles in W-1%Y2O3 are stable in size even at 2300 °C.•The swaged sol–gel W-1%Y2O3 show ductility at a relative low temperature of 250 °C.•The sol–gel method is promising for preparation of nanostructured tungsten materials.
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The chemical composition of a LaMnO3 perovskite was modified sequentially by an improved sol–gel method to include cobalt centers in some B sites formerly occupied by Mn. In this way, ...a representative set of materials of general formula LaMn1-xCoxO3 was obtained whose composition extends from LaMnO3 to LaCoO3. These perovskites, as promising materials for oxygen reduction or oxygen evolution reactions, were characterized by several imaging (SEM), spectroscopic (XPS, EDX) and diffraction (XRD) techniques to elucidate their structure and to demonstrate the existence of composition differences between the catalytic surface and the bulk material. Specifically, it was found that lanthanum ions prevail at the surface of the catalyst but high cobalt-substitution levels stimulate the surface enrichment in B cations in their respective higher oxidation states (Mn4+ and Co3+ against Mn3+ and Co2+). This phenomenon opens the possibility of tuning their electrocatalytic properties and to synthesize suitable materials for electrochemical reactions involving molecular oxygen.
A series of n-alkanes/silica composites as form-stable phase change materials (PCMs) were synthesized in a sol–gel process using sodium silicate precursor. The chemical compositions and structures of ...the synthesized composites were characterized by Fourier transform infrared spectroscopy. Scanning electric micrographs show an irregularly spherical morphology of the n-alkanes/silica composites, and transmission electric micrographs confirm that the n-alkanes have been well encapsulated by silica. These n-alkanes/silica composites keep a good sharp stability due to the support of silica wall even if the n-alkanes are in molten state. The differential scanning calorimetric analysis indicates that the phase change behaviors and characteristics of the n-alkanes/silica composites strongly depend on the carbon atom number in n-alkanes, and meanwhile, the encapsulated n-alkanes have a high thermal storage capability. The investigation on thermal performance demonstrated that the n-alkanes/silica composites achieved a high thermal conductivity, low supercooling, and good work reliability as a result of the encapsulation of n-alkanes with highly thermal conductive inorganic silica. Moreover, the thermal stability of the composites was also improved due to the protection of silica wall toward the encapsulated n-alkanes. It is anticipative that, owing to the easy availability and low cost of sodium silicate, the synthetic technology developed by this work has a high feasibility in the industrial manufacture of the form-stable PCMs.
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•The n-alkanes/silica composites were synthesized using sodium silicate precursor.•The composites have a good shape stability with variation of ambient temperature.•The phase change behaviors of the composites depend on carbon number of n-alkanes.•The thermal conductivity, working reliability, and thermal stability were enhanced.
CO + 3H2 → CH4 + H2O.
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•A Ni@SiO2core–shell catalyst was prepared by a sol–gel method.•Nano-sized Ni was stabilized even with a high Ni content.•This was far superior for CO ...methanation than the conventional Ni/SiO2 catalyst.•This was selective for selective CO methanation in CO2.
The specific catalytic activity of a supported metal catalyst increases with an increase in the number of active sites per mass of catalyst, which can be accomplished by increasing the metal content and/or decreasing the particle size of the metal. However, this leads to sintering of metal particles during the reaction, especially in highly exothermic reactions such as CO methanation. In this study, we prepared different SiO2-supported Ni catalysts by wet impregnation and sol–gel methods, and applied them to CO methanation. The prepared catalysts were characterized with N2 physisorption, X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), temperature-programmed reduction with H2 (H2-TPR), and transmission electron microscopy (TEM). Some problems associated with the wet impregnation method, such as sintering of Ni and the inability to load the silica with large amounts of Ni, were avoided by using the sol–gel method, in which size-controlled NiO was first synthesized using a polymer stabilizing agent, and then coated with a mesoporous silica shell through a polymerization approach. The prepared 55wt% Ni@SiO2 catalyst exhibited the co-presence of Ni nanoparticles (mean size=8.0±4.4nm) and nanorods (mean length=15.5±13nm, mean width=8.1±4.4nm). This catalyst was far superior for CO methanation than the conventional 33wt% Ni/SiO2 catalyst prepared by wet impregnation, in which the Ni particle size was 24.5nm. The 55wt% Ni@SiO2 catalyst also exhibited excellent catalytic performance for selective CO methanation in the presence of an excessive amount of CO2.
Clean energy production and environmental remediation are imperative for sustainable future. Specially, exploration of multifunctional catalyst, for production of low-cost and eco-friendly hydrogen ...(H2) fuel as well as efficient decomposition of emerging pollutants are certainly needed. This study investigates magnesium manganese oxide (MgMnO3), a perovskite oxide, synthesized by simple citrate sol–gel technique, and its structural, morphological, optical, and photoelectrochemical properties were analyzed for the photodegradation of ciprofloxacin (CIP) antibiotic, methylene blue (MB) dye, and photoelectrochemical (PEC) water splitting. The cubic spinel crystal structure of MgMnO3 was confirmed through powder X-ray diffraction (XRD) analysis. FE-SEM images of the MgMnO3 material revealed a cauliflower-like morphology, consisting of an assembly of microspherical grains of varying sizes. UV–Vis spectroscopy exhibited broad absorption in the UV–Visible region, and the Tauc plot estimated a band gap of 1.54 eV. The MgMnO3 catalyst showed 88% and 96% for photodecomposition of CIP (10 mg/L) and MB (10 mg/L), respectively, using 35 mg and 30 mg of catalyst quantity over 90 min. In addition, MgMnO3 photoelectrode showcases superior photoelectrochemical behavior, exhibiting maximal photocurrent density of 13.21 mA cm−2 measured at 1.2 V vs. RHE and achieving a solar-to-hydrogen conversion efficiency of 2.45% compared to MgO and MnO2 photoelectrode. EIS measurements of MgMnO3 show enhanced charge transfer and recombination kinetics. Notably, the MgMnO3 electrode reveals outstanding photoelectrochemical durability, maintaining its stability even after continuous illumination for 9 h. Improved PEC properties could be attributed to wider light absorption, enhanced photo-induced charge-separations, and electron mobility. Thus, present study established an efficient and enduring multifunctional catalyst, catering photocatalytic degradation and PEC H2 generation.
•MgMnO3 perovskite nanoarchitecture was synthesized using a citrate sol–gel technique.•Maximum degradation of 88% and 96% for the CIP and MB, respectively.•A remarkable photocurrent density of 13.21 mA cm−2 at 1.2 V vs. RHE was achieved.•High solar-to-hydrogen conversion efficiency of 2.45% with excellent stability up to 9 h.•EIS results show excellent charge transfer and transport properties.
Polymer derived silicon oxycarbide (SiOC) ceramics are investigated as potential anodes for lithium ion batteries. Different SiOC ceramics are prepared by pyrolysis (1000°C and 1400°C under ...controlled argon atmosphere) of polysiloxanes ceramic precursors. Preceramic polymers are synthesized using the sol–gel method. Phenyltriethoxysilane (PhTES) and methyltriethoxysilane (MTES) have been used as starting precursors and mixed with different ratios in order to tailor the chemical composition and the structure of the final product. The obtained SiOC ceramics are amorphous with various content of free carbon phase (from approx. 25 to 40wt.%). The presence of disordered carbons in the ceramic structure is confirmed by the appearance of a well pronounced D band at 1330cm−1 in the Raman spectra. Additionally, 29Si MAS-NMR spectra show the presence, in the structure of the materials pyrolysed at 1000°C, of mixed bond tetrahedra such as: SiO3C, SiO2C2, SiOC3 and SiO4 units. Pyrolysis at an elevated temperature (1400°C) promotes the phase separation into oxygen rich (SiO4) and carbon rich (SiC4) units with consumption of mixed bonds. Carbon rich SiOC samples exhibit significant reversible capacity and enhanced cycling stability (up to 600mAhg−1 measured at a slow current rate of C/20 after 140cycles of continuous charging–discharging with increasing current density). However, the high irreversible capacity of the first few cycles remains an issue to be solved.
•New silicon oxycarbide SiOC materials were studied as anodes for Li-ion batteries.•The chemical composition and the structure influence the electrochemical activity.•The SiOC samples exhibit a high recovered capacity and long-life stability.•The best electrochemical performance was achieved for carbon-rich samples.
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