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Band gap engineered zinc oxide nanostructures <i>via</i> a sol–gel synthesis of solvent driven shape-controlled crystal growth
摘要： A reliable sol–gel approach, which combines the formation of ZnO nanocrystals and a solvent driven, low shape-controlled, crystal-growth process to form well-organized ZnO nanostructures at temperature is presented. The sol of ZnO nanocrystals showed shape-controlled crystal growth with respect to the solvent type, resulting in either nanorods, nanoparticles, or nanoslates. The solvothermal process, along with the solvent polarity facilitate the shape-controlled crystal growth process, augmenting the concept of a selective adhesion of solvents onto crystal facets and controlling the final shape of the nanostructures. The XRD traces and XPS spectra support the concept of selective adhesion of solvents onto crystal facets that leads to yield different ZnO morphologies. The shift in optical absorption maxima from 332 nm in initial precursor solution, to 347 nm for ZnO nanocrystals sol, and finally to 375 nm for ZnO nanorods, evidenced the gradual growth and ripening of nanocrystals to dimensional nanostructures. The engineered optical band gaps of ZnO nanostructures are found to be ranged from 3.10 eV to 3.37 eV with respect to the ZnO nanostructures formed in different solvent systems. The theoretical band gaps computed from the experimental XRD spectral traces lie within the range of the optical band gaps obtained from UV-visible spectra of ZnO nanostructures. The spin-casted thin film of ZnO nanorods prepared in DMF exhibits the electrical conductivity of 1.14 × 10?3 S cm?1, which is nearly one order of magnitude higher than the electrical conductivity of ZnO nanoparticles formed in hydroquinone and ZnO sols. The possibility of engineering the band gap and electrical properties of ZnO at nanoscale utilizing an aqueous-based wet chemical synthesis process presented here is simple, versatile, and environmentally friendly, and thus may applicable for making other types of band-gap engineered metal oxide nanostructures with shape-controlled morphologies and optoelectrical properties.
关键词： electrical conductivity,ZnO nanostructures,optical band gap,shape-controlled crystal growth,sol–gel synthesis
更新于2025-11-19 16:56:42
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Facile Sol-gel Synthesis of Metaloxide Nanoparticles in a Cellulose Paper Template
摘要： Ensembles of free standing particles of titanium, zinc, copper and iron oxides of 6-109 nm in size were sol-gel synthesized with a use of a cellulose paper as a template. The calcination time as short as 60 min at 550°C in air was found to be sufficient for the formation of crystalline single phase TiO2 or ZnO nanoparticles, Cu2O+CuO or Fe2O3+Fe3O4 nanocomposites and to burn out the organic components. The impurities initially present in the cellulose (Сa, Na, Cl) were detected in the synthesized compounds.
关键词： Sol-gel synthesis,Zinc oxide,Nanoparticle,Copper oxides,Cellulose,Iron oxides,Titanium oxide
更新于2025-09-23 15:22:29
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A sola??gel synthesis to prepare size and shape-controlled mesoporous nanostructures of binary (IIa??VI) metal oxides
摘要： A base-catalyzed sol–gel approach combined with a solvent-driven self-assembly process at low temperature is augmented to make manganese oxide (Mn3O4), copper oxide (CuO), and magnesium hydroxide (Mg(OH)2) nanostructures with size- and shape-controlled morphologies. Nanostructures of Mn3O4 with either hexagonal, irregular particle, or ribbon shape morphologies with an average diameter ranged from 100 to 200 nm have been prepared in four di?erent solvent types. In all morphologies of Mn3O4, the experimental XRD patterns have indexed the nanocrystal unit cell structure to triclinic. The hexagonal nanoparticles of Mn3O4 exhibit high mesoporocity with a BET surface area of 91.68 m2 g?1 and BJH desorption average pore diameter of ～28 nm. In the preparation of CuO nanostructures, highly nanoporous thin sheets have been produced in water and water/toluene solvent systems. The simulated XRD pattern matches the experimental XRD patterns of CuO nanostructures and indexes the nanocrystal unit cell structure to monoclinic. With the smallest desorption total pore volume of 0.09 cm3 g?1, CuO nanosheets have yielded the lowest BET surface area of 18.31 m2 g?1 and a BHJ desorption average pore diameter of ～16 nm. The sol of magnesium hydroxide nanocrystals produces highly nanoporous hexagonal nanoplates in water and water/toluene solvent systems. The wide angle powder XRD patterns show well-de?ned Bragg's peaks, indexing to a hexagonal unit cell structure. The hexagonal plates show a signi?cantly high BET surface area (72.31 m2 g?1), which is slightly lower than the surface area of Mn3O4 hexagonal nanoparticles. The non-template driven sol–gel synthesis process demonstrated herein provides a facile method to prepare highly mesoporous and nanoporous nanostructures of binary (II–VI) metal oxides and their hydroxide derivatives, enabling potential nanostructure platforms with high activities and selectivities for catalysis applications.
关键词： catalysis applications,size and shape-controlled morphologies,mesoporous nanostructures,binary (II–VI) metal oxides,sol–gel synthesis
更新于2025-09-23 15:19:57
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Fluorolytic Sol–Gel Synthesis of Nanometal Fluorides: Accessing New Materials for Optical Applications
摘要： The potential of fluorolytic sol–gel synthesis for a wide variety of applications in the field of optical materials is reviewed. Based on the fluorolytic sol–gel synthesis of nanometal fluorides, sols of complex fluorometalates have become available that exhibit superior optical properties over known classical binary metal fluorides as, for instance, magnesium fluoride, calcium fluoride, or strontium fluoride, respectively. The synthesis of transparent sols of magnesium fluoroaluminates of the general composition MgxAlFy, and fluoroperovskites, [K1?xNax]MgF3, is reported. Antireflective coatings fabricated from MgF2, CaF2, MgxAlFy, and [K1?xNax]MgF3 sols and their relevant properties are comprehensively described. Especially the heavier alkaline earth metal fluorides and the fluorperovskites crystallizing in a cubic crystal structure are excellent hosts for rare earth (RE) metals. Thus, the second chapter reflects the synthesis approach and the properties of luminescent systems based on RE-doped alkaline earth metal fluorides and [K1?xNax]MgF3 phases.
关键词： nanometal fluorides,antireflective coatings,sol–gel synthesis,luminescent materials
更新于2025-09-19 17:15:36
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Novel KFeO<sub>2</sub> nanoparticles for dye-sensitized solar cell
摘要： Novel KFeO2 nanoparticles for dye-sensitized solar cell. Environmentally clean and green source of energy is solar energy that can meet the increasing demand for energy. Recent trends in solar energy reflect that delafossite materials getting more attention because of its low-cost production and easy method of synthesis, non-toxic nature, environment-friendly nature, degradability compared to the silicon. In this direction, delafossite KFeO2 nanoparticles have synthesized by chemical method and used as photo-anode material for dye-sensitized solar cells (DSSC). The structural, morphological, optical and photovoltaic properties of KFeO2 nanoparticles have been investigated. Transmission electron microscopy (TEM) study reveals that the KFeO2 nanoparticles exhibit spherical morphology with particle size 12 nm. Rietveld refinement of x-ray diffraction (XRD) patterns of KFeO2 reflects, its orthorhombic phase with Pbca space group. The optical study reveals that the bandgap of the KFeO2 nanoparticles lying in the visible range of spectrum, i.e., 1.88 eV. The DSSC has been fabricated using KFeO2 nanoparticles. The power conversion efficiency parameters is 0.84 V; 4.72 mA/cm2; 64% and 2.54% respectively, for open-circuit voltage (VOC), short circuit current–density (JSC), fill factor (FF) and Power conversion efficiency for fabricated DSSC. It has been found that the efficiency of fabricated DSSC has been decrease to 2.27% after 45 days.
关键词： Dye sensitized solar energy materials,KFeO2,Sol-gel synthesis,Nanoparticles
更新于2025-09-19 17:13:59
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ZnO and TiO2 Nanostructured Dye sensitized Solar Photovoltaic Cell
摘要： The performance of nanostructured metal oxides (ZnO and TiO2) based dye sensitized solar cells (DSSC) were investigated. Natural dye, chlorophyll extracted from fresh spinach leaves, was used as sensitizer for fabrication of the cells. ZnO was synthesized by chemical bath deposition technique.The Field emission scanning electron microscopic (FESEM) images show hexagonal patterned ZnO nano-towers of 5 μm length and ~ 1 μm diameter. TiO2 was synthesized by sol-gel method.The FESEM images show that the TiO2 nano-rods of 2 μm length and ~ 300 nm diameter.TiO2 based DSSC was possessed better efficiency of 0.27% as compare to ZnO based DSSC of 0.13%.
关键词： Diffused Reflectance Spectra,Chlorophyll dye,Dye sensitized solar cells,Chemical and sol-gel synthesis
更新于2025-09-16 10:30:52
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Stabilization of cubic phase in scandium-doped zirconia nanocrystals synthesized with sol-gel method
摘要： A new room-temperature synthesis of nanocrystals of scandium doped zirconium oxide by sol-gel method is reported. The structure of the obtained product is checked with standard structural analysis methods. The crystal phase of ZrO2-Sc2O3 nanocrystals changes from monoclinic to tetragonal and cubic with the increase in scandium concentration. The importance of the cubic phase, which appears at 10 mol% and refines at 16 mol% of Sc2O3 concentration, is emphasized. The UV-Vis absorption spectra of the product are measured, and its bandgap is evaluated from the fundamental absorption edge. The value of the bandgap was calculated as 5.65 eV for the cubic phase.
关键词： scandium-doped zirconia nanocrystals,UV-Vis spectra,sol-gel synthesis,stabilization of cubic phase
更新于2025-09-11 14:15:04
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The Effect of Process Parameters on the Amorphous Citrate Sol-gel Synthesis of Cu-doped Ca12Al14O33
摘要： Ca12Al14O33 (C12A7) is a highly functional material due to its ability to act as an anionic source and its conversion from a wide band-gap insulator to a conductive oxide material as a function of processing. Cationic doping, on the order of 1 mol%, of C12A7 has been shown to have profound effects on the physical properties of the material. One such cation, Cu, increases the catalytic efficiency and drastically alters the electronic landscape. The amorphous citrate sol-gel synthesis technique is widely used to synthesize doped C12A7 materials as it promises homogeneous cationic dispersion and a fine and controlled grain size. This promise relies on the formation of a homogeneous citrate resin of cationic citrate species, homogeneous decomposition of cation citrate species, and homogeneous crystallization of the desired phase. In this report, theoretical complex diagrams are calculated to determine the optimal pH for citrate resin formation in the Cu-C12A7 system. The resin decomposition and crystallization kinetics are characterized through high-temperature X-ray diffraction and thermogravimetric analysis. The optimal pH range for the citrate resin homogeneity was theoretically determined to be a range from 3 to 6, and experimental characterization shows that raising the pH from <1 to 4 leads to Cu-C12A7 phase purity, reduces grain size by 30%, and inhibits CaCO3 formation to lower the synthesis temperature from ~900 °C to 840 °C. This report highlights the importance of sol-gel solution chemistry and the corroboration of XRD analysis with microstructural analysis.
关键词： C12A7,Citrate sol-gel synthesis,Doped synthesis,Ca12Al14O33,In-situ X-ray Diffraciton
更新于2025-09-10 09:29:36
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White-Light Emitting Di-Ureasil Hybrids
摘要： White-light emitting materials have emerged as important components for solid state lighting devices with high potential for the replacement of conventional light sources. Herein, amine-functionalized organic-inorganic di-ureasil hybrids consisting of a siliceous skeleton and oligopolyether chains codoped with lanthanide-based complexes, with Eu3+ and Tb3+ ions and 4,4'-oxybis(benzoic acid) and 1,10-phenanthroline ligands, and the coumarin 1 dye were synthesized by in situ sol–gel method. The resulting luminescent di-ureasils show red, green, and blue colors originated from the Eu3+, Tb3+, and C1 emissions, respectively. The emission colors can be modulated either by variation of the relative concentration between the emitting centers or by changing the excitation wavelength. White light emission is achieved under UV excitation with absolute quantum yields of 0.148 ± 0.015, 0.167 ± 0.017, and 0.202 ± 0.020 at 350, 332, and 305 nm excitation, respectively. The emission mechanism was investigated by photoluminescence and UV–visible absorption spectroscopy, revealing an efficient energy transfer from the organic ligands to the Ln3+ ions and the organic dye, whereas negligible interaction between the dopants is discerned. The obtained luminescent di-ureasils have potential for optoelectronic applications, such as in white-light emitting diodes.
关键词： lanthanide complexes,di-ureasil organic–inorganic hybrids,in situ sol–gel synthesis,white light emission,coumarin 1
更新于2025-09-10 09:29:36
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Sol-gel synthesis and characterization of ZnAl2O4 powders for transparent ceramics
摘要： The sol-gel synthesis of ZnAl2O4 ceramic powders from alkoxide and acetate sources of metals, as well as the microstucture and the hardness of the hot-pressed ZnAl2O4 specimens were considered. ZnAl2O4 powders were prepared by the hydrolysis of an alcohol solution of aluminium isopropoxide using an aqueous solution of zinc acetate followed by heat treatment. The thermal evolution of the ZnAl2O4 precursor was investigated. The effect of calcination temperature on the morphology and the specific surface area of ZnAl2O4 powders were also studied. The sintering of the resultant powders to the high transparent ceramic using a hot pressing with 1 wt% ZnF2, as a sintering additive was successfully demonstrated. The in-line transmittance of ZnAl2O4 ceramics (1 mm thickness) achieved 80% in the visible region and 85 % at 5 μm; Vickers hardness was 11.6 GPa.
关键词： transparent ceramic,powders,sol-gel synthesis,ZnAl2O4
更新于2025-09-10 09:29:36