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In this work, Bi3+ doped NaNbO 3 materials have been prepared successfully by the hydrothermal method at low temperature and pressure. The influence of Bi3+ dopant on the structural, morphological/optical properties of NaNbO 3 nanomaterials is investigated. The perovskite-type structure for the pristine and doped samples is characterized within the orthorhombic structure and the unit cell parameteres increase as the dopant concentration increases. The σ DC conductivity for the investigated samples shows that 3 % of Bi induces a decrease from 9.26 10–5 S/m to 3.27 10−5 S/m and the obtained results for the conductivity were interpreted taking into account VRH and CBH theoretical models. [ABSTRACT FROM AUTHOR]

Cobalt ferrite nanopowders were synthesized by means of the sol-gel method, using citric acid as a chelating agent, and various alcohols as gelling agent: ethanol (ET), ethylene glycol (EG), polyvinyl alcohol (PVA), 1,3 propanediol (PD) and a mixture of PVA and EG. The simultaneous TG/DTA analysis revealed different thermal behaviours of the synthesized gels, depending on the gelling agent. The powders obtained at 500 °C and annealed at 700 °C and 1000 °C contain a single CoFe 2 O 4 phase. Scanning electron microscopy (SEM) revealed the influence of the gelling agent on the morphology of cobalt ferrite particles. The coercivity and the saturation magnetization of the powders obtained at 500 °C showed a strong dependence on the crystallite size, determined by the nature of the gelling agent. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a study regarding the cobalt ferrite obtaining in the Co x Fe3−x O4 system, where x =0.5; 1.0; 1.5 by two different synthesis methods. The Co(II) and Fe(III) complexes method leads to the thermal decomposition at 300°C for this precursor with the pure cobalt ferrite (CoFe2O4) formation for x =1 or mixed with γ-Fe2O3 for x =0.5 and Co3O4 for x =1.5. By co-precipitation followed by ultrasonic milling synthesis method the pure cobalt ferrite is obtained at 90°C for x =1 or mixed with Fe3O4 for x =0.5 and Co3O4 for x =1.5. When the initial samples are heated at 400°C, the identified oxide phase is identical for the same value of x. The obtained powders were investigated by X-ray diffraction (XRD), FTIR spectrometry and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDX). The final product has nanometric size and has a strong tendency to agglomerated, thus influencing the saturation magnetization value. The shape of the magnetization curves is influenced by the presence of the secondary phases for x ≠1. [Copyright &y& Elsevier]

Abstract: ZnGa2O4 phosphor doped with Eu3+ ions was synthesized by hydrothermal method using two concentrations: 3.34mol% and 1.67mol% of Eu3+. The crystal structure was investigated by means of X-ray diffraction, scanning electron microscopy and atomic force microscopy. The results indicate that the material consisting of ZnGa2O4:Eu3+ nanoparticles exhibits good crystalinity, with cubic spinel structure. The powders were found to have 4.74eV of ZnGa2O4:Eu3+ (3.34mol%) and 4.69eV of ZnGa2O4:Eu3+ (1.67mol%) band gaps, respectively. The luminescent analysis of the materials shows that the trivalent europium ions doped in this material are localized in different sites, substituting both Zn2+ and Ga3+. The emission spectra of the europium-doped samples, originating from 5D0–7F J (J =0–4) transitions, suggests the existence of three different site symmetry of Eu3+ ions, tetrahedral (Zn2+), distorted octahedral (Ga3+) and low octahedral (Ga3+) sites, respectively. [Copyright &y& Elsevier]

• Montmorillonite functionalized with LaMnO 3 were carried out for the first time. • By functionalization, physico-chemical properties of hybrid materials are improved. • HER and OER catalytic properties of electrodes modified have been studied. [Display omitted] Hybrid materials based on montmorillonite functionalized with LaMnO 3 perovskitic structures were obtained for the first time by ultrasonic method with sonotrode immersed in the reaction medium, followed by heat treatment at a temperature of 600 °C. The clay mineral montmorillonite (Mmt), sodium montmorillonite (Mmt-Na+) and functionalized material (Mmt-LMO) were characterized by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM/Edx) techniques. The XRD patterns of Mmt-LMO composites show both the presence of the perovskitic phase with orthorhombic structure, and a mixture of aluminosilicates, corresponding to the montmorillonite clay minerals. The (Mmt), (Mmt-Na+) minerals and (Mmt-LMO) hybrid material were used to manufacture modified electrodes whose catalytic properties for the oxygen and hydrogen evolution reactions were investigated in alkaline medium. Based on electrochemical experimental results, some of these electrodes are catalytically active toward the hydrogen evolution reaction and the more performant ones were investigated further and it was found that the electrode modified with the composition containing 6 mg LaMnO 3 functionalized montmorillonite and 10 µL Nafion solutions have the best electrocatalytic properties. At the current density of −10 mA/cm2 the electrode exhibits an over potentialfor hydrogen evolution of −0.48 V and its Tafel slope was measured to be 70 mV/dec. This study complements the extant scientific knowledge relevant to the water splitting domain. [ABSTRACT FROM AUTHOR]

An efficient fast hydrothermal method was used to synthesize Co 1-x Pd x Fe 2 O 4 (x = 0, 0.05, 0.1 and 0.5) nanocrystalline powders, where Co2+ was substituted with Pd2+ ions. The materials crystallize within the spinel structure (Fd-3m) with crystallites sizes varying between 5.6 and 17.6 nm. The particles present a cubic shape for x = 0 and x = 0.1 samples and the presence of Pd in samples was confirmed by Energy-dispersive X-Ray spectroscopy (EDX) analysis. The magnetic hysteresis loops indicate that the saturation magnetization decreases with the increase once with of the Pd2+ amount substitution (from ~52 emu/g for x = 0–~7 emu/g for x = 0.5). • Pd substituted CoFe2O4 materials were obtained for the first time by a fast method. • Cubic shape morphology for x = 0 and x = 0.1 Pd substituted CoFe2O4 materials. • The saturation magnetization decreases with the increase of the Pd2+ amount. [ABSTRACT FROM AUTHOR]

The study herein reports the synthesis by hydrothermal method at 200 °C for 12 h, followed by heat treatment at 600 °C for 6 h of NaNbO 3 materials, undoped and Zr-doped at different concentrations (1, 2 and 3%). The influence of Zr doping in NaNbO 3 compounds on the morpho-structural and optical properties as well as their dependence on dopant concentration was studied by X-ray diffraction (XRD), transmission electron microscopy (TEM-HRTEM/EDX), Fourier transform-infrared (FT-IR), Raman and Ultraviolet-Visible (UV-Vis) spectroscopy. An orthorhombic structure (P mc 2 1 space group) is characteristic for undoped NaNbO 3 and 1% Zr-doped NaNbO 3 materials, while 2 and 3% Zr-doped NaNbO 3 present the tetragonal symmetry (P4/mbm space group). Results show different morphologies depending on the dopant concentration (cubic shape particles for undoped and 1% Zr sample while for 2 and 3% Zr wire-like morphology is observed) and a slight increase of the optical band gap with increasing Zr concentration from 3.61 eV (undoped NaNbO 3) to 3.73 eV (3% Zr: NaNbO 3). [ABSTRACT FROM AUTHOR]

Iron phosphate materials have attracted a lot of attention due to their potential as cathode materials for lithium-ion rechargeable batteries. It has been shown that lithium insertion or extraction depends on the Fe mixed valence and reduction or oxidation of the Fe ions' valences. In this paper, we report a new synthesis method for the Fe3(PO3OH)4(H2O)4 mixed valence iron phosphate. In addition, we perform temperature-dependent measurements of structural and physical properties in order to obtain an understanding of electronic–structural interplay in this compound. Scanning electron microscope images show needle-like single crystals of 50 μm to 200 μm length which are stable up to approximately 200 °C, as revealed by thermogravimetric analysis. The crystal structure of Fe3(PO3OH)4(H2O)4 single crystals has been determined in the temperature range of 90 K to 470 K. A monoclinic isostructural phase transition was found at ~213 K, with unit cell volume doubling in the low temperature phase. While the local environment of the Fe2+ ions does not change significantly across the structural phase transition, small antiphase rotations occur for the Fe3+ octahedra, implying some kind of electronic order. These results are corroborated by first principle calculations within density functional theory, which also point to ordering of the electronic degrees of freedom across the transition. The structural phase transition is confirmed by specific heat measurements. Moreover, hints of 3D antiferromagnetic ordering appear below ~11 K in the magnetic susceptibility measurements. Room temperature visible light absorption is consistent with the Fe2+/Fe3+ mixed valence. [ABSTRACT FROM AUTHOR]

In this research paper, the thermal behaviour of the mixed valence iron oxides Fe3(PO4)2(OH)2 is presented in both air and vacuum atmosphere. The structure, morphology and the magnetic properties of the iron phosphates samples obtained at selected temperatures were carefully investigated. The electrocatalytic properties of synthetic barbosalite Fe3(PO4)2(OH)2 materials for the oxygen and hydrogen evolution reactions (OER and HER) were investigated in a wide pH range, using graphite electrodes modified with different compositions containing the catalyst. The best results were obtained for the compositions with 6 mg barbosalite. During the HER experiments, overpotentials of − 300 and − 350 mV were observed at the current density of − 10 mA cm−2 in strong alkaline and in strong acidic media, respectively. During the OER studies performed in strong acidic solution and in neutral environment, overpotentials of 320 and 690 mV were obtained at the current density of 10 mA cm−2. These findings complement the existing scientific literature relevant to the water splitting domain. Furthermore, the visible light absorption ability of synthetic Fe2+Fe3+2(PO4)2(OH)2 materials was also evaluated. [ABSTRACT FROM AUTHOR]

Ag-doped LaMnO3 nanoparticles have been synthesized through sol–gel process using citric acid as a chelating agent. Silver effect on physicochemical properties was studied. The physicochemical properties and electrical performance of the obtained materials were also investigated, using thermogravimetric analysis (TGA) and X-ray diffraction (XRD) techniques. Thermogravimetric analysis shows that for the studied materials a decomposition stage between 3.7% and 4.1% can be observed, and mass increases from the LMN-Ag1 to the LMN-Ag3 sample. Also, in all those three situations an endothermic process with a maximum around 600 °C is observed. The diffractograms of the perovskite materials showed single-phase crystalline with high purity and rhombohedral structure with R-3c space group. The electrical measurements show that the conductivity spectrum is formed by both the static component σDC corresponding to the low frequencies and the component σAC corresponding to high frequencies. The values of σDC of samples are significantly influenced by the silver ions concentration. [ABSTRACT FROM AUTHOR]

Two samples of NaTaO3 perovskite materials were prepared by the standard hydrothermal method at the same reaction temperature (600 °C) but with different sintering times: 6 hours for sample S1 and 12 hours for sample S2. Using X-ray diffraction (XRD), it shows that samples S1 and S2 are mixtures of Na-Ta oxides (Ta2O5 and the prevailing phase NaTaO3). The scanning electron microscopy analysis (SEM), shows that the grains are connected each other in agglomerated clusters of size about few hundred nanometers. The frequency (f) dependencies of complex impedance, Z(f) = Z'(f) – i Z''(f) of the samples, over the frequency range 20 Hz – 2 MHz, at room temperature are presented. The real component Z' of the complex impedance decreases with increasing frequency and the imaginary component Z'' has two maximum corresponding to two relaxation processes. The results obtained from the complex impedance spectroscopy, Z''(Z') showed the appearance of two semicircles, corresponding to grain and grain boundary mechanism. Experimental results have been fitted with two parallel RC equivalent circuits connected in series and the parameters R and C have been evaluated. [ABSTRACT FROM AUTHOR]

Pharmaceuticals and pesticides are emerging contaminants problematic in the aquatic environment because of their adverse effects on aquatic life and humans. In order to remove them from water, photocatalysis is one of the most modern technologies to be used. First, newly synthesized photocatalysts were successfully prepared using a sol–gel method and characterized by different techniques (XRD, FTIR, UV/Vis, BET and SEM/EDX). The photocatalytic properties of TiO2, ZnO and MgO nanoparticles were examined according to their removal from water for two antibiotics (ciprofloxacin and ceftriaxone) and two herbicides (tembotrione and fluroxypyr) exposed to UV/simulated sunlight (SS). TiO2 proved to be the most efficient nanopowder under UV and SS. Addition of (NH4)2S2O8 led to the faster removal of both antibiotics and herbicide fluroxypyr. The main intermediates were separated and identified for the herbicides and antibiotic ciprofloxacin. Finally, the toxicity of each emerging pollutant mixture and formed intermediates was assessed on wheat germination and biomass production. [ABSTRACT FROM AUTHOR]

Ni 11□ (HPO 3) 8 (OH) 6 nanorods were the focus of three different studies. First, the thermal behaviour of the material was investigated and it outlined a good thermal stability up to 400 °C. Second, a comparative electrochemical study concerning the OER performance in alkaline medium of several graphite electrodes modified with the nickel phosphite was performed. The most promising electrodes were further characterised electrochemically and the electrode modified with Nafion solution and 5 mg Ni 11□ (HPO 3) 8 (OH) 6 exhibited the smallest overpotential value at the 10 mA cm−2 anodic current density (0.59 V), as well as the smallest Tafel slope (0.081 V dec−1). Furthermore, the constant potential electrolysis test revealed that this electrode is fairly stable within a time span of 300 min. Third, the capacity of Ni 11□ (HPO 3) 8 (OH) 6 nanorods to remove MB and RhB were investigated under simulated visible light irradiation and positive results were obtained for the application as visible-light active photocatalyst. All this together corroborated with the eco-friendly nature of the materials, reinforces the fact that the phosphite type compound is a promising candidate for the design of new multifunctional and advanced materials. • Ni 11□ (HPO 3) 8 (OH) 6 acts as OER catalyst in alkaline medium. • Positive results were obtained for application as visible-light active photocatalyst. • Ni 11□ (HPO 3) 8 (OH) 6 has a good thermal stability in air up to 400 °C. [ABSTRACT FROM AUTHOR]

Nitrogen containing lanthanum manganite perovskite material has been successfully synthesized through sol-gel method using urea (CH 4 N 2 O) as a nitrogen source. The obtained powders were followed thermal treatment at low temperature. In order to achieve a comparative study on the obtained materials, three concentrations of urea were used (0.05; 0.1 and 0.15%). The characteristic of the materials were examined by differential thermal analysis (TG/DTA/HF), X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), scanning/transmission electron microscope (SEM/TEM), energy-dispersive X-ray spectroscopy (EDX) and electrochemical measurements were made. The XRD patterns show that all analyzed sample are well crystallized and present a perovskite single phase with the cubic structure, space group: Pm-3m, with the average size of crystallites around 30 nm. All the N-doped LaMnO 3 perovskites exhibit remarkable electrocatalytic effect on the redox reaction of potassium ferricyanide improving redox peak current. Image 1 • Nitrogen doped LaMNO 3 materials was carried out for the first time. • Electrochemical behaviour of N–LaMnO 3 on graphite electrode was investigated. • By sol-gel technique was obtained nanometric particles with different morphologies. [ABSTRACT FROM AUTHOR]