Diluted magnetic semiconductor properties in Zn<Subscript>1−x</Subscript>Cu<Subscript>x</Subscript>O nanoparticles synthesized by sol gel route

Nanoparticles of ZnO:Cu Diluted Magnetic Semiconductor (DMS) are prepared using sol gel method. The structural, optical and EPR properties of them are investigated. The XRD patterns of them show the formation of polycrystalline and hexagonal wurtzite structure without any secondary phase formation. The average size of particles ranges from 14 to 19 nm. In the optical absorption study of the samples, a red shit of optical band edge and a narrowing of the optical band gap are observed when Cu concentration is increased. The PL measurements illustrate 392 nm UV radiation of the near band-edge emissions of ZnO, blue emission at 450 nm and orange emission at 628 nm. The cause of decrease in intensity of these emission lines is the sincerely enhanced non-radiative transitions when Cu is doped in ZnO. EPR measurements provide substantial evidence for the presence of defect states and enhancement of exchange interaction.     

Preparation of Cd-doped SnO<Subscript>2</Subscript> nanoparticles by sol–gel route and their optical properties

Nanocrystalline cadmium doped tin oxide (SnO₂) powders of about 2.5–4.5 nm in size have been synthesized by using different solvents via sol–gel method. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDX), Transmission electron spectroscopy (TEM), UV-Vis absorption and Photoluminescence (PL) spectroscopy. The PL emission spectra revealed that the band centered at 452 nm might be related with oxygen vacancies. A spherical, small rod and slice like morphologies of the prepared Cd-SnO₂ nanoparticles were observed in the SEM and TEM studies. The presence of Cd modifies the structural, morphological and optical properties of the tin oxide nanoparticles.     

Preparation and characterization of nanocrystalline CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> deposited on SiO<Subscript>2</Subscript>: in situ sol–gel process

In situ base catalyst assisted sol–gel process is used for the synthesis of nanocrystalline CoFe₂O₄ deposition on SiO₂ particles. The SiO₂ particles were prepared using base catalyst assisted sol–gel process and the consecutive formation and deposition of nanocrystalline CoFe₂O₄ on SiO₂ particles was monitored using Powder X ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermo Gravimetric And Differential Thermal Analysis (TG/DTA), Scanning Electron Microscopy and Energy Dispersive X ray Spectroscopy (SEM–EDS) and High Resolution Transmission Electron Microscopy (HRTEM). The crystallite size of CoFe₂O₄ is calculated using Scherrer’s formula and it is found to be 8 nm. The HRTEM images and selective area electron diffraction (SAED) results confirmed the formation of nanocrystalline CoFe₂O₄ particles deposited over SiO₂ spheres.     

Structural,optical and photoluminescence properties of Zn<Subscript>1−x</Subscript>Ce<Subscript>x</Subscript>O (x = 0, 0.05 and 0.1) nanoparticles by sol–gel method annealed under Ar atmosphere

Ce doped ZnO nanoparticles (Zn_1−xCe_xO, x = 0.0, 0.05 and 0.1) have been synthesized by sol–gel method at annealing temperature of 500 °C for 1 h under Ar atmosphere. The synthesized samples have been characterized by powder X-ray diffraction (XRD), energy dispersive X-ray studies, UV–Visible spectrophotometer and fourier transform infrared (FTIR) spectroscopy. The XRD measurements indicate that the prepared nanoparticles have a hexagonal wurtzite structure and CeO₂ crystallites. The calculated average crystalline varied from 21.97 to 15.62 nm with increase in Ce concentrations. The increase in lattice parameters reveals the substitution of Ce into ZnO lattice. The presence of functional groups and the chemical bonding is confirmed by FTIR spectra. PL spectra of the Zn_1−xCe_xO system show that the shift in near band edge emission from 386 to 363 nm and a shift in blue band emission from 517 to 485 nm which confirms the substitution of Ce into the ZnO lattice.     

High-temperature stable transition aluminas nanoparticles recovered from sol–gel processed chitosan-AlO<Subscript>x</Subscript> organic–inorganic hybrid films

Five and ten weight percent-alumina-containing chitosan-AlO_x films were prepared via sol–gel processing. The films were AlO_x-agglomerate-free. These organic–inorganic films were degraded by heating at 500?°C. The solid powder residues were found by means of thermogravimetry, X-ray diffractometry, infrared spectroscopy, and electron microscopy to consist of alumina (Al₂O₃) nanoparticles entraping volatile components, whose thermal removal encouraged ambient oxygen uptake. The surface microstructure and morphology of the recovered alumina nanoparticle were inspected by high-resolution transmission and scanning electron microscopy. Also, the surface chemistry and texture were evaluated by X-ray photoelectron spectroscopy and N₂ sorptiometry. Coalescences of globular nanoparticles of γ-/η-Al₂O₃ were the dominant composition of the 800?°C calcination product of the recovered alumina, irrespective of the alumina-content of the film. Upon increasing the calcination temperature up to 1100?°C, an enhanced polymorphic transition into agglomerated nanoparticles of the seldom encountered Iota-(ι-)Al₂O₃ took place. The high thermal stability of the otherwise unstable transition aluminas (at ≥950?°C) may suggestively owe to its polymorphic interdependence and/or persistent nanoscopic nature (average particle size?=?ca. 3–4?nm; specific surface area?=?ca. 80–60?m²/g). The surface chemical composition for the recovered transition aluminas nanopowders promises versatile acid–base properties for catalysis applications. Accordingly, the highly abundant bio-waste, chitosan, was successfully utilized as a novel synthesis medium for catalytic-grade alumina nanoparticles.

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The highly abundant bio-waste material, chitosan, is successfully employed as a synthetic medium for catalytic-grade alumina nanoparticles. This novel sol–gel synthesis process resulted in nearly 100%-recovery of nanoparticle transition γ-/η- and ι-Al₂O₃ and may be utilized in fabricating other materials/metal oxides

     

Synthesis of mixed metal oxide nanoparticles of SnO<Subscript>2</Subscript> with SrO via sol–gel technology: their structural,optical, and electrical properties

Mixed metal oxides of tin with strontium (xSnO₂.SrO) in different molar ratio {where x?=?1 (1), 2 (2), 4(3); SnO₂ doped with Sr⁺²(4), SnO₂ doped with Sr⁺² and co-doped with F^?(5)} have been prepared by sol–gel technology in basic medium using SnCl₂.2H₂O as precursor in isopropanol as solvent. Structural analysis by XRD patterns have shown formation of particles at nanoscale and phase separation of SnO₂ in tetragonal rutile framework in these mixed metal oxides. This fact was further supported by TEM. SEM images of all these samples have shown formation of various geometrical patterns ranging from spherical particles to nanorods. In the IR spectra of all these oxides, Sr–O absorption bands were present only in sample (1). UV–Vis spectroscopy has shown reduction in optical band gap in mixed metal oxides and the lowest value of band gap was observed for sample (3). Photoluminescence spectra of all these derivatives are found to be almost similar again indicated retention of tetragonal rutile SnO₂ framework. I–V curves of all these oxides are non-linear and lowest resistance was observed for sample (3). This fact was further supported by impedance measurements.

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Structural and low temperature Raman scattering studies in SrTi<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Co<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>3</Subscript> nanoparticles synthesized by sol–gel method

We investigate effects of Co dopant concentration on the structure and low temperature Raman scattering properties in SrTi_1−x Co _x O₃ (x = 0.00, 0.10, 0.20, 0.30) nanoparticles prepared by sol–gel method. The dopant induced changes are studied by XRD, and Raman scattering measurements. The results show an average particle size of about 20 nm depending on the Co content and the lattice parameters decrease as increasing the Co content. In the Raman spectra, a broad structure in the region 100–500 cm⁻¹ is almost absent and the peaks in the region 600–800 cm⁻¹ show different weights with respect to SrTiO₃, relating to structural changes. The anomalous change in the area ratio of Raman peaks as function of temperature suggests a phase transition in our samples in the range of 110–130 K. These results indicate that the Co ion has replaced the site of Ti in unit cell. This novel route also demonstrates the advantage of synthesizing the compound with low annealing temperature.     

Single-phased white-light emitting CaAl<Subscript>2</Subscript>Si<Subscript>2</Subscript>O<Subscript>8</Subscript>: Eu<Superscript>2+</Superscript>, Mn<Superscript>2+</Superscript> phosphors prepared by a sol–gel method

CaAl₂Si₂O₈: Eu²⁺, Mn²⁺ phosphors have been prepared by a sol–gel method. X-ray diffractometer, spectrofluorometer and UV–Vis spectrometer were used to characterize structural and optical properties of the samples. The results indicate that anorthite (CaAl₂Si₂O₈) directly crystallizes at 1000 °C in the sol–gel process. CaAl₂Si₂O₈: Eu²⁺, Mn²⁺ phosphors show two emission bands excited by ultraviolet light. Blue (around 415 nm) and yellow (around 575 nm) emissions originate from Eu²⁺ and Mn²⁺, respectively. With appropriate tuning of Mn²⁺ content, CaAl₂Si₂O₈: Eu²⁺, Mn²⁺ phosphors exhibit different hues and relative color temperatures.     

Mg<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>SiO<Subscript>4</Subscript> compound obtained via sol–gel method: structural,morphological and electrochemical properties

Prospective cathode materials Mg_2-xMn _x SiO₄ (0.0?≤?x?≤?0.4) for magnesium-ion secondary battery were synthesized using sol gel method. Crystalline structure, morphology, particle size, electrical and electrochemical properties of the samples were investigated. X-ray diffraction patterns of the materials exhibited no extra peak for x?≤?0.6 indicated that Mg_2-xMn _x SiO₄ materials were successfully synthesized. Mn doping in magnesium site did not affect the formation of single phase, and this probably due to the low concentration of Mn to induces structural changes. Mn doping contributed to the enhancement of the electrochemical performance of Mg₂SiO₄. For this work, Mg_1.4Mn_0.6SiO₄ which possesses the largest unit cell volume, smallest charge transfer resistance, and highest conductivity value showed the most promising electrochemical performance compared to the other samples. These results indicated the suitability of the Mg_2-xMn _x SiO₄ to be exploiting further for potential applications as solid electrolytes in electrochemical devices and strengthen the fact that doping could be an effective way to enhanched the structural, electrical and electrochemical performance of materials.

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Aqueous germanate solution,alternative sol–gel precursor for preparation of Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript> diluted magnetic semiconductors

The solids content and gelation time of aqueous germanate solution were examined in this work. Samples of 5, 10 and 20 mol% Mn doped Ge were prepared by using the aqueous germanate solution as a liquid Ge precursor. No second phase such as Mn₅Ge₃ was detected in the 5 and 10 mol% Mn doped samples, implying that Mn ions were uniformly diluted into the Ge host matrix. The 5 and 10 mol% Mn-doped Ge samples exhibit room-temperature ferromagnetic behaviors that are likely originated from the RKKY (Ruderman–Kittel–Kasuya–Yosida)-like interaction between the localized Mn ions in the Ge matrix. Therefore, the aqueous germanate solution can be an alternative sol–gel precursor for preparation of the Mn _x Ge_1−x diluted magnetic semiconductors (DMSs).     

Synthesis of Ca<Subscript>3</Subscript>Al<Subscript>6</Subscript>Si<Subscript>2</Subscript>O<Subscript>16</Subscript>: Ce<Superscript>3+</Superscript>, Tb<Superscript>3+</Superscript> phosphors by sol–gel method and optical properties

Ca₃Al₆Si₂O₁₆: Ce³⁺, Tb³⁺ phosphors have been prepared by sol–gel method. The structure and photoluminescence properties were studied with careful. The results indicated that the single-phased Ca₃Al₆Si₂O₁₆ phosphors crystallize at 1,000 °C for 2 h in conventional furnace. With appropriate concentrations of Ce³⁺ and Tb³⁺ ions into Ca₃Al₆Si₂O₁₆ matrix, these materials exhibit blue phosphors and white light under ultraviolet radiation. White-light emission can be achieved because of a 400 nm emission ascribed to transitions of Ce³⁺ ions and three sharp peaks at 487, 543, 585 nm, respectively, resulting from transitions of Tb³⁺ ions.     

Y<Subscript>2</Subscript>O<Subscript>3</Subscript>:Eu<Superscript>3+</Superscript>,Tb<Superscript>3+</Superscript> thin films prepared by sol–gel method: structural and optical studies

Y₂O₃: Eu³⁺,Tb³⁺ transparent, high density and optical quality thin films were prepared by the sol–gel dip-coating technique. Yttrium (III) 2,4-pentadionate was used as a precursor by its hydrolysis in ethanol. The doping agents were incorporated in the form of europium and terbium nitrate. Structural, morphological and optical properties of prepared films were investigated for different annealing temperatures in order to establish the ideal processing route that enhances the luminescent properties. X-ray diffraction (XRD) analysis shows the cubic phase for 10-layer films and annealing temperatures higher than 500°C. At 700°C, highly densified (4.52 g cm⁻³) and very smooth films (1.4 nm at 700°C) are produced, composed of crystallites with a grain size of 11 nm. The film thickness, refractive index and porosity, as well as the luminescent properties, were found to vary with treatment temperature.     

Effect of the degree of doping on the size and magnetic properties of nanocrystals La<Subscript>1 – <Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>FeO<Subscript>3</Subscript> synthesized by the sol–gel method

Nanopowders La_1–x Zn _x FeO₃ (nominal degree of doping x _nom = 0, 0.05, 0.075, 0.1, 0.15, 0.2, 0.3, and 0.4) were synthesized by the sol–gel method using aqueous ammonia as a precipitator and were then annealed at 950°C for 60 min. From the data of X-ray powder diffraction analysis and local electron probe microanalysis, the maximum actual limit of doping of lanthanum ferrite with zinc was determined: x = 0.072. The dependence of the particle size on the Zn²⁺ content was found to be nonmonotonic. The magnetic characteristics (specific magnetization J, coercivity H _c, and magnetic susceptibility χ) of samples at temperatures of 300 and 100 K in fields of up to 1300 kA/m. It was shown that, with increasing degree of doping, J increases from 0.188 A m²/kg (at x = 0) to 0.245 A m²/kg (at x = 0.072), and χ varies nonmonotonically from 11.5 × 10^–6 (at x = 0) to 15.3 × 10^–6 (at x = 0.072) (at 300 K). With decreasing measurement temperature to 100 K, the magnetization and susceptibility monotonically increase.     

Photoluminescence and photocatalytic properties of Er<Superscript>3+</Superscript>-doped In<Subscript>2</Subscript>O<Subscript>3</Subscript> thin films prepared by sol–gel: application to Rhodamine B degradation under solar light

The effect of Er³⁺ doping (1%) on the structural, optical and photocatalytic properties of In₂O₃ thin films deposited on quartz substrates by spin coating was investigated. The In₂O₃:1% Er³⁺ films, annealed in the temperature range 800–1000 °C, were characterized by X-ray diffraction, scanning electron microscopy (SEM), atomic force microscopy, UV–Vis spectroscopy, ellipsometry and photoluminescence (PL). The films are polycrystalline with a cubic structure and the lattice parameter increases with the incorporation of Er³⁺ owing to its larger radius. The SEM images of the film show a granular morphology with large grains (~ 200 nm). The doped In₂O₃ film exhibits less transparency than In₂O₃ in the UV–visible region with band gaps of 3.42 and 3.60 eV, respectively. PL shows strong lines at 548 and 567 nm, assigned to Er³⁺ under direct excitation at 532 nm. The energy diagram of the junction In₂O₃:1% Er³⁺/Na₂SO₄ (0.1 M) solution plotted from physical and photoelectrochemical characterizations shows the feasibility of the films for Rhodamine B (RhB) degradation under solar light. The conduction band at 2.22 V deriving from the In³⁺:5s orbital is suitably positioned with respect to the O₂/O ₂ ^· level (~ 1.40 V_SCE), leading to oxidation of 32% of 10 ppm RhB within 40 min of solar irradiation.     

In situ sol–gel fabrication of new poly(amide–ether–imide)/titania (TiO<Subscript>2</Subscript>) nanocomposite thin films containing <Emphasis Type=SmallCaps>l</Emphasis>-leucine moieties

In this study, the synthesis, morphology, and thermal properties of amino acid containing polyimide/titania nanohybrid films are investigated. At first, a chiral diamine containing l-leucine moieties in the structure (synthesized previously) was polymerized with 4,4′-oxydiphthalic anhydride in extremely dry conditions. Resulted poly(amic acid) (PAA) was mixed with a moisture-sensitive titania precursor (tetraethyl orthotitanate [Ti(OEt)₄]) and casted to a dust-free glass plate. The water derived from thermal imidization of PAA hydrolyzed Ti(OEt)₄ to titania nanoparticles with almost spherical shapes. The thermogravimetric analysis of various nanocomposites confirms the improvement in the thermal stability with the increase in the percentage of titania nanoparticle. The transmission electron microscopy of nanohybrid films with 3%, 5%, and 10% w/w of titania contents confirms well dispersion of nanoparticles in the polymer ground. The X-ray diffraction spectra showed that the titania contents have amorphous structure.