Synthesis and characterization of FeVO4 nanoparticles

Iron vanadate (FeVO₄) nanoparticles were synthesized by simple co-precipitation method using various surfactants such as ethylene glycol, polyethylene glycol 200 and polyethylene glycol 400 as the structure directing agents. Systematic investigations on the structural, morphological and magnetic properties of the materials have been studied. The lattice constants of the triclinic structure of FeVO₄ were calculated from the X-ray diffraction (XRD) analyses. The average grain size was estimated to be around 35 nm, which increased with increasing the calcination temperature. The stretching and bending vibrations of Fe-O were evaluated from the FT-IR spectra. Using VSM magnetometer, magnetic property was investigated through magnetic susceptibility and magnetization measurements. FeVO₄ exhibits two magnetic ordering temperatures at T ≈ 20 K and 14 K, which is due to two different chemical environments of Fe ligands such as octahedral FeO₆ and trigonal bipyramidal FeO₅ in a six-column doubly bent chain, respectively.     

Synthesis and characterization of Co3O4 hollow spheres

Co₃O₄ hollow spheres were hydrothermally prepared at 130 °C for 16 h in the presence of Poly-vinylpyrrolidone (PVP). The as-prepared products were characterized by powder X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), infrared spectrum (IR), X-ray photoelectron spectrum (XPS), and optical absorption spectrum. PVP surfactant plays important roles in the formation of Co₃O₄ hollow spheres. These Co₃O₄ hollow spheres have average diameters of ca. 350 nm, and the wall thickness around the shell is about 42 nm. The possible formation mechanism of hollow Co₃O₄ spherical structures has simply been proposed.     

Synthesis and characterization of C3N4 nanowires and pseudocubic C3N4 polycrystalline nanoparticles

C₃N₄ nanowires and pseudocubic C₃N₄ polycrystalline nanoparticles have been synthesized by the reaction between C₃N₃Cl₃ and NaN₃ with Zn powder as catalyst. The process was carried out using a constant-pressure benzene thermal method at 40 MPa and 220 °C. The prepared nanowires have a diameter range of 3-6 nm and length range of 100-200 nm, while the diameters of the nanoparticles range from 10 nm to 40 nm. The as-prepared samples were characterized by X-ray powder diffraction (XRD), Fourier transform spectroscopy (FTIR), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS).     

Synthesis and characterization of Bi2Fe4O9 powders

Bi₂Fe₄O₉ have been successfully prepared using ethylenediaminetetraacetic (EDTA) acid as a chelating agent and ethylene glycol as an esterification agent. Heating of a mixed solution of EDTA, ethylene glycol, and nitrates of iron and bismuth at 140 °C produced a transparent polymeric resin without any precipitation, which after pyrolysis at 250 °C was converted to a powder precursor for Bi₂Fe₄O₉. The precursors were heated at 400–800 °C in air to obtain Bi₂Fe₄O₉ powder and differential scanning calorimetry (DSC), thermogravimetric (TG), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques were used to characterize the precursors and the derived oxide powders. XRD analysis showed that well-crystallized and single-phase Bi₂Fe₄O₉ with orthorhombic symmetry was obtained at 700 °C for 2 h and BiFeO₃ and Fe₂O₃/FeCO₃ were intermediate phases before the formation of Bi₂Fe₄O₉. Bi₂Fe₄O₉ powders show weak ferromagnetism at room temperature.     

Synthesis, characterization and photocatalytic properties of nanosized Bi2WO6, PbWO4 and ZnWO4 catalysts

Nanosized Bi₂WO₆, PbWO₄ and ZnWO₄ photocatalysts were synthesized by a mild hydrothermal crystallization process. The physical and photophysical properties of the catalysts were characterized by X-ray diffractometry, Brunauer-Emmet-Teller surface area and porosity measurements, transmission electron microscopy, Raman spectra, and diffused reflectance spectroscopy. The rhodamine-B photodegradation in aqueous medium was employed as a probe reaction to test the photoactivities of the as-prepared samples under four irradiation wavelengths. Bi₂WO₆ not only presented the photocatalytic activity in the wide spectral scope, including UV and visible light but also exhibited the strong photosensitized capability to transform RhB under visible light irradiation (λ > 490 nm). ZnWO₄ only displayed relatively high photoactivity under UV irradiation. However, PbWO₄ showed poor photoactivity under any light irradiation. On the basis of the calculated density functional theory (DFT), the photocatalytic mechanisms were discussed.     

Fabrication and characterization of the photoluminescent properties of Tb doped one-dimensional GdPO4 nanorods

In this letter, one-dimensional GdPO₄:Tb³⁺ nanostructures were successfully synthesized by an easy hydrothermal method at 120 °C and 150 °C. Their morphology and structure were characterized and their photoluminescent properties were investigated, including excitation and emission spectra as well as fluorescent dynamics. Results indicated that one-dimensional GdPO₄:Tb³⁺ nanorods formed at low temperature. The hydrothermal temperature did not affect their morphology and size. The crystal structure of GdPO₄:Tb³⁺ nanostructures belongs to monoclinic phase. According to excitation and emission spectra, the strong green emission of Tb³⁺ ions from ⁵D₄-⁷F₅ transitions and the energy transfer from Gd³⁺ to Tb³⁺ ions were observed.     

A novel green luminescent material AlPO4:Tb

A novel green phosphor Tb³⁺ doped AlPO₄ was synthesized by conventional solid-state reaction method. The phosphor showed prominent luminescence in green due to the ⁵D₄-⁷F₅ transition of Tb³⁺. Structural characterization of the luminescent material was carried out with X-ray powder diffraction (XRD) analysis. The XRD measurements indicated that there are no crystalline phases other than AlPO₄. Luminescence properties were analyzed by measuring the excitation and photoluminescence spectra. Photoluminescence measurements indicated that the phosphor exhibited bright green emission at about 542 nm under UV excitation. It is shown that the 3 mol% of doping concentration of Tb³⁺ ions in AlPO₄:Tb³⁺ phosphor is optimum. The measured chromaticity for the phosphors AlPO₄:Tb³⁺ under UV excitation is (0.32, 0.53).     

Synthesis, characterization, and evaluation of lubrication properties of composites of ordered mesoporous carbons and luminescent CePO4:Tb nanocrystals

Having new potential applications in forging processes in mind, composites of an ordered mesoporous carbon and luminescent metal phosphate nanocrystals were synthesized for the first time. Three kinds of CMK-3/CePO₄:Tb nanocomposites were prepared by treating a mesoporous CMK-3 host with different lanthanide phosphate precursor solutions. Characterization of the obtained nanocomposites by small-angle X-ray scattering, wide-angle X-ray diffraction, transmission electron microscopy, thermogravimetry, and nitrogen physisorption analysis showed that in two cases, the nanocrystals (ca. 2–3 nm in size) were located inside the mesopores, whereas in the third case the nanocystals (ca. 6 nm in size) merely adhered to the outer surfaces of the carbon particles. The CMK-3 and the two nanocomposites had ordered hexagonal structures (space group p6mm); all the materials possessed amorphous carbon walls. After combustion of the nanocomposites, the residues upon excitation with UV light exhibited the typical green luminescence of Tb³⁺. A preliminary evaluation of the lubrication properties of the CMK-3 and one nanocomposite material was performed. The friction factors determined by means of ring upsetting tests revealed that the carbon materials were able to lower frictional forces although they were 3–4 times less efficient than a commercial graphite-based reference lubricant.     

Novel ternary g-C3N4/Fe3O4/MnWO4 nanocomposites: Synthesis,characterization, and visible-light photocatalytic performance for environmental purposes

The g-C₃N₄/Fe₃O₄/MnWO₄ nanocomposites were prepared by a refluxing-calcination procedure. Visible-light-induced photocatalytic experiments showed that the g-C₃N₄/Fe₃O₄/MnWO₄ (10%) nanocomposite has excellent ability to degrade a range of contaminants including rhodamine B, methylene blue, methyl orange, and fuchsine, which is about 7, 10, 25, and 31 times of the g-C₃N₄ photocatalyst, respectively. Reactive species trapping experiments revealed that superoxide anion radicals play major role in the photodegradation reaction of rhodamine B (RhB). After the treatment process, the utilized photocatalyst was magnetically recovered and reused with negligible loss in the photocatalytic activity, which is vital in the photocatalytic processes. Finally, a mechanism was proposed for the enhanced interfacial carrier separation and transfer and the improved photocatalytic performance.     

Polymer-assisted synthesis and luminescence properties of MgAl2O4:Tb nanopowder

In the present work, terbium doped magnesium alluminate (MgAl₂O₄:Tb) nanopowder was synthesized by a polyacrylamide gel method. Structure, morphology and luminescence spectra were investigated by X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), and photoluminescence spectroscopy (PL) measurements. The results showed that the single-phase MgAl₂O₄ could be formed at a relatively low temperature about 800 °C without unreacted Al₂O₃ and MgO phases. Powders with nanosized microstructures were formed. The polyacrylamide gel method resulted in a powder with smaller particle size and fewer agglomerates than the conventional sol-gel method. Luminescence analysis indicated that, the prepared MgAl₂O₄:Tb powders had strong green emission with ⁵D₄-⁷F₅ as the most prominent group. The emission intensity increased with increasing the calcination temperature.     

Hydrothermal synthesis and luminescent properties of Y2O3:Tb and Gd2O3:Tb microrods

One-dimensional (1D) Y₂O₃:Tb³⁺ and Gd₂O₃:Tb³⁺ microrods have been successfully prepared through a large-scale and facile hydrothermal method followed by a subsequent calcination process in N₂/H₂ mixed atmosphere. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (IR), thermogravimetric analysis (TGA), energy-dispersive X-ray spectra (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), photoluminescence (PL) and cathodoluminescence (CL) spectra as well as kinetic decays were used to characterize the samples. The as-formed products via the hydrothermal process could transform to cubic Y₂O₃:Tb³⁺ and Gd₂O₃:Tb³⁺ with the same morphology and slight shrinking in size after a postannealing process. Both Y₂O₃:Tb³⁺ and Gd₂O₃:Tb³⁺ microrods exhibit strong green emission corresponding to ⁵D₄ → ⁷F₅ transition (542 nm) of Tb³⁺ under UV light excitation (307 and 258 nm, respectively), and low-voltage electron beam excitation (1.5 → 3.5 kV), which have potential applications in fluorescent lamps and field emission displays.     

Synthesis, characterization and magnetic properties of CoFe2O4 nanorods

In this work, we demonstrated a new precursor route to synthesize CoFe₂O₄ one-dimensional (1D) nanorods. CoFe₂O₄ nanorods were prepared via the thermal decomposition of CoFe₂(C₂O₄)₃ nanorod precursor, which was prepared by solvothermal method without the assistance of template or surfactant. The microstructure and magnetic property of the obtained products were characterized by x-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), thermogravimetric (TG) and differential thermal analysis (DTA) and vibrating sample magnetometer (VSM). The results showed that the as-prepared CoFe₂O₄ nanorods were built by magnetic nanoparticles after calcining the precursor nanorods at different temperatures, and the size variation of magnetic nanoparticles with calcination temperatures leaded to variable magnetic properties.     

Synthesis and characterization of NiAl2O4 nanoparticles obtained through gelatin

Nanoparticles of NiAl₂O₄ were synthesized by heating (500-1000 °C) the dried resin resultant of a mixture in aqueous solution of gelatin, NiCl₂·6H₂O and AlCl₃·6H₂O. The particle size and microstrain were calculated from the line broadening of X-ray powder diffraction peaks through the Rietveld method refinement: these are 3.9-16 nm and − 0.743-0.139%, respectively. The NiAl₂O₄ nanoparticles were characterized by X-ray powder diffraction (XRPD), thermo gravimetric analysis (TG), BET and TEM techniques.     

A new yellowish green luminescent material SrMoO4:Tb

A novel yellowish green phosphor tervalent terbium (Tb³⁺) doped strontium molybdate (SrMoO₄) was synthesized by conventional solid-state reaction method and its crystal structure and luminescent properties are investigated in this paper. The X-ray diffraction patterns (XRD) showed that the phosphor sintered at 750 °C for 3 h was a pure SrMoO₄ phase. The excitation spectrum consisted of two bands and the two excitation peaks located at 375 nm and 488 nm respectively. The emission spectrum was composed of four narrow bands, in which the strongest emission was located at 548 nm. The particle size analysis indicated that the median particle size D₅₀ = 2.89 μm and range of particle size distribution was narrow. These results showed that the SrMoO₄:Tb³⁺ phosphor was a promising yellowish green phosphor for ultraviolet light emitting diode (UVLED) and blue LED based white LED. The appropriate concentration of Tb³⁺ was 5 mol% for the highest emission intensity at 548 nm. Natrium ion (Na⁺) was found to be a promising charge compensator for SrMoO₄:Tb³⁺ phosphor.     

Synthesis and characterization of Mo doped hierarchically porous SO4/ZrO2 solid acid catalyst

A novel hierarchically porous molybdenum-promoted SO₄²⁻/ZrO₂ solid acid with nanocrystallized framework of tetragonal phase and high surface area has been synthesized via a composite surfactant-assisted route combined with a hydrothermal treatment process. The XRD, N₂-adsorption, TEM, and FT-IR pyridine adsorption were used for the structural analysis and acidic characterization. The results show that the novel mesoporous solid acid exhibits classical tetragonal phase and excellent catalytic performance in the esterification reaction of acetic acid with n-butanol and can preserve the acid better than normal solid acids after several recycle experiments. This hierarchically zirconia solid acid has a good potential as catalysts in some chemical reactions such as esterification.     

Synthesis and structural characterization of the normal spinel Li[Ni2]O4

Room-temperature electrochemical extraction of lithium from nearly stoichiometric, layered LiNiO₂ gives the solid-solution system Li_1?xNiO₂. Monitoring the temperature dependence of the X-ray-diffraction pattern of Li_0.5NiO₂ has revealed a first-order transformation above 150°C to the cubic, normal spinel phase Li[Ni₂]O₄. This spinel phase is stable to 300°C     

Synthesis and characterization of nanocrystalline MgAl2O4 spinel via sucrose process

Nanocrystalline MgAl₂O₄ spinel powder was synthesized using metal nitrates and a polymer matrix precursor composed of sucrose and polyvinyl alcohol (PVA). The precursor and the calcined powders were characterized by simultaneous thermal analysis (STA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). According to XRD results, the inceptive formation temperature of spinel via this technique was between 600 and 700 °C. The calcined powder at 800 °C for 2 h has faced shaped morphology and its crystallite size is in the range of 8-12 nm. Further studies also showed that the amount of polymeric matrix to metal ions has significant influence on the crystallite size of synthesized magnesium aluminate spinel powder.     

Hydrothermal synthesis and photoluminescence of SrWO4:Tb novel green phosphor

Tb³⁺-doped SrWO₄ phosphors with a scheelite structure have been prepared by hydrothermal reaction. X-ray powder diffraction, field-emission scanning electron microscopy, photoluminescence excitation and emission spectra and decay curve were used to characterize the resulting samples. Scanning electron microscopy image showed that the obtained SrWO₄:Tb³⁺ phosphors appeared to be nearly spherical and their sizes ranged from 1 to 3 μm. Photoluminescence spectra indicated the phosphors emitted strong green light centered at 545 nm under ultraviolet light excitation. Because 12 at.% SWO₄:Tb³⁺ phosphor exhibits intensive green emission under 254 nm excitation in comparison with the commercial green fluorescent lamp phosphor (LaPO₄:Ce,Tb), the excellent luminescence properties make it a new promising green phosphor for fluorescent lamps application.     

Photoluminescence properties of Y2O3:Tb and YBO3:Tb green phosphors synthesized by hydrothermal method

In this work, two Tb³⁺ activated green phosphors: Y₂O₃:Tb³⁺ and YBO₃:Tb³⁺ were prepared by hydrothermal method. Photoluminescence properties of both phosphors were studied in details. Both phosphors exhibit similar luminescent characteristics symbolized by the dominant green emission at 545 nm. Concentration quenching occurs at the Tb³⁺ concentration of 1.60 atomic% and 2.57 atomic% for Y₂O₃:Tb³⁺ and YBO₃:Tb³⁺, respectively. Luminescence decay properties were characterized to better understand the mechanism of concentration quenching. Based on the calculation, the concentration quenching in both phosphors was caused by the dipole–dipole interaction between Tb³⁺ ions.     

Observation on long afterglow of Tb in CaWO4

The Tb³⁺ doped CaWO₄ phosphors are synthesized via high temperature solid state reaction. The X-ray diffraction shows that small amount of Tb³⁺ does not have a significant influence on the structure of CaWO₄. A broad absorption band of the WO₄²⁻ group is observed from photoluminescence and the energy transfer from WO₄²⁻ group to Tb³⁺ ions induces the f-f transition. The cross-relaxation between two adjacent Tb³⁺ ions weakens ⁵D₃-⁷F_j transitions and enhances the ⁵D₄-⁷F_j transitions, leading to a green long afterglow of the phosphors. The thermoluminescence curves centered around 75 °C reveal the trap depth for afterglow generation is about 0.74-0.77 eV. The optimum Tb³⁺ concentration for afterglow properties is about 1%. A deep hole trap is induced when Tb³⁺ concentration exceeds 1% and it suppresses the thermoluminescence and the decay properties.