Ultrasound and Microwave-Assisted Co-precipitation Synthesis of La<Subscript>0.75</Subscript>Sr<Subscript>0.25</Subscript>MnO<Subscript>3</Subscript> Perovskite Nanoparticles from a New Lanthanum(III) Coordination Polymer Precursor

In the present study nano-sized strontium-doped lanthanum manganite, La_0.75Sr_0.25MnO₃ (LSM), were synthesized by three simple different methods (a) co-precipitation, (b) ultrasonic and (c) microwave-assisted co-precipitation. A lanthanum(III) coordination polymer, [pyda.H]₂[La₂(pydc)₄(H₂O)₄]·2H₂O, where [pyda.H]⁺?=?2,6-diaminopyridinium, and (pydc)^2??=?2,6-pyridinedicarboxylate, was used as a new precursor. The products were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), field emission scanning electron microscope (FESEM), thermal gravimetric (TG) and differential thermal analyses (DTA), as well as by Energy-dispersive X-ray spectroscopy (EDX). The XRD results showed that the crystal lattice of the product obtained was orthorhombic perovskite structure. The porosity, particle size and homogeneity of calcinated LSM were strongly dependent on the preparation method. In addition, the results proved that the product formation time was decreased considerably when ultrasonic or microwave irradiation methods were used.     

Synthesis and Characterization of Ferromagnetic BaFe<Subscript>2</Subscript>O<Subscript>4</Subscript> Nanocrystals Using Novel Ionic Precursor Complex [Fe(opd)<Subscript>3</Subscript>]<Subscript>2</Subscript>[Ba(CN)<Subscript>8</Subscript>]

The following investigation reports the synthesis of novel complex [Fe(opd)₃]₂[Ba(CN)₈] and preparation of BaFe₂O₄ nanoparticles through thermal decomposition without using any surfactant. The complex was characterized via Furrier transform infrared spectroscopy (FT-IR), ultra violet-visible spectroscopy (UV–vis), conductivity measurement and elemental analysis. The synthesized crystals of inorganic precursor complex was transferred to furnace, where they were calcined under normal atmosphere condition at 900 °C for 4 h. Formation of BaFe₂O₄ was supported by FT-IR and energy-dispersive X-ray analysis. Hexagonal structure of nano-oxide was confirmed on powder X-ray diffraction. Furthermore, uniform morphology of nanocrystals were reported by scanning electron microscopy. The saturation magnetization (22 emu/g), remanent magnetization (6 emu/g) and coercivity (400 Oe) reported on vibrating sample magnetometer curve illustrates the promising industrial and medicinal applications of prepared mixed oxide.     

Preparation of Zinc(II) Oxide Nanoparticles from a New Nano-Size Coordination Polymer Constructed from a Polypyridyl Amidic Ligand; Spectroscopic, Photoluminescence and Thermal Analysis Studies

A new zinc(II) coordination polymer, {[Zn(bpcdp)₂(DMF)₄](ClO₄)₂·(H₂O)₂}_n (1) bpcdp = 2,6-bis(4-pyridinecarboxamide)pyridine has been synthesized and characterized by IR, ¹HNMR and ¹³CNMR spectroscopy. The single crystal X-ray data of compound 1 shows the zinc(II) atom has been considered as octahedral with ZnN₂O₄ coordination sphere. Two nitrogen atoms of bpcdp ligand and four oxygen atoms of DMF molecules have occupied coordination sphere around zinc(II) atoms. The prepared zinc(II) coordination polymer grows in three-dimensional network by hydrogen bonding and π–π stacking interaction. The nanostructure of compound 1 were obtained by sonochemical process and studied by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), IR and NMR spectroscopy. Thermal stabilities of single crystalline and nano-size samples of compound 1 were studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The ZnO nanoparticles were obtained by direct calcination of compound 1 at 400 °C and by thermolysis in oleic acid at 200 °C. The obtained zinc(II) oxide nanoparticles were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).     

Synthesis and Characterization of Superparamagnetic NiBaO<Subscript>2</Subscript> Nano-Oxide Using Novel Precursor Complex [Ba(H<Subscript>2</Subscript>O)<Subscript>8</Subscript>][Ni(dipic)<Subscript>2</Subscript>]

In this paper, for the first time, synthesis of [Ba(H₂O)₈][Ni(dipic)₂] complex and preparation of NiBaO₂ nano-oxide are reported through thermal decomposition under surfactant free condition. This novel complex was characterized by Fourier transform infrared spectroscopy (FT-IR), ultra violet–visible spectroscopy, conductivity measurement and elemental analysis. Formation of novel nanoparticles was supported by FT-IR and energy-dispersive X-ray spectroscopy and the orthorhombic structure of nanocrystals was confirmed by powder X-ray diffraction analysis. In addition, size distribution as well as uniform morphology of prepared nano-oxide were recorded by dynamic light scattering analysis and field-emission scanning electron microscopy, respectively. Magnetic features measured by vibrating sample magnetometer, illustrate superparamagnetic behavior of the oxide.     

One-dimensional Coordination Polymer as New Precursor for Preparation of Fe2O3 Nano-particles

A Fe(II) one-dimensional coordination polymer, [Fe(pyterpy)₂](SCN)₂.MeOH (1), which pyterpy is 4′-(4-Pyridyl)-2,2′:6′,2′-terpyridine, has been synthesized by using branched tube and characterized by elemental analysis, X-ray powder diffraction (XRD) and IR spectroscopy. Iron(III) oxide nano-particles were obtained by thermolysis of compound 1 in oleic acid (surfactant) at 286 °C under air atmosphere. The Fe₂O₃ nano-particles were characterized by XRD and scanning electron microscopy. This study demonstrates that the Fe(II) coordination polymers are suitable precursors for the simple one-pot preparation of iron oxide nano-materials.     

Recyclable Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@Tween20@Ag Nanocatalyst for Catalytic Degradation of Azo Dyes

Silver nanoparticles supported on superparamagnetic iron oxide (SPION)-Tween20 nanocomposite were prepared by a combined polyol and chemical reduction routes. The morphology, composition and structure of Fe₃O₄@Tween20@Ag nanocatalyst were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy, energy dispersive X-ray spectroscopy, thermal gravimetric analyzer, and X-ray powder diffraction. In addition the magnetic properties were evaluated with vibrating sample magnetometry. It was found that Fe₃O₄@Tween20@Ag nanocatalyst could catalyze the degradation of various organic azo dyes and could easily be recovered from the reaction medium with external magnet. Also, the magnetic catalyst can be succesfully recycled and reused for at least five successive degradation cycles of methyl orange, methylene blue and Rhodamine B, confirming a high recycling efficiency. The cost effective and recyclable Fe₃O₄@Tween20@Ag nanocatalyst provide an novel nanomaterials architecture for environmental remediation applications.     

Facile Preparation of LaFeO<Subscript>3</Subscript>/rGO Nanocomposites with Enhanced Visible Light Photocatalytic Activity

The present work demonstrates a facile route for preparing LaFeO₃/rGO nanocomposites comprising of metal oxide nanoparticles and graphene. Structural, morphology, optical and photocatalytic studies of the samples were characterized using powder X-ray diffraction (XRD), FT-IR, Raman, high resolution scanning electron microscopy (HRSEM), high resolution transmission electron microscope (HRTEM), atomic force microscopy (AFM), thermogravimetry (TGA), X-ray photoelectron spectroscopy, UV–visible and photocatalytic. LaFeO₃/rGO nanocomposites believed as an effective photocatalyst for the degradation of methyl orange (MO) dye under visible light irradiation. The inclusion of carbon enhances the light absorption of LaFeO₃, resulting in the enhanced photocatalytic activity of the nanocomposite. The degradation of MO dye under visible light source was completely achieved using LaFeO₃/rGO as a catalyst.     

Sol-gel synthesis and features of the structure of Au-In<Subscript>2</Subscript>O<Subscript>3</Subscript> nanocomposites

The specific features of the chemical state of gold and indium oxide in Au-In₂O₃ (0.01–1.0 wt % Au) nanocomposites have been investigated by the methods of X-ray diffraction analysis, electron microscopy, infrared and optical spectroscopy, electron paramagnetic resonance, and thermal analysis. Xerogels, powders, and films obtained by the introduction of HAuCl₄ into the indium hydroxide sol and thermal treatment at 50–700°C have been studied. The mutual influence of the components on the size of the Au and In₂O₃ particles and the state of their surface has been established. It has been shown that the synthesis of Au-In₂O₃ by the sol-gel method leads to the formation of nanosized indium oxide particles with the high concentration of hydroxyl groups on surfaces and favors the stabilization of gold in the form of nanoclusters and ion forms.     

Direct Synthesis of Cd3OSO4 Nano-particles From a New Three-dimensional Cadmium(II) Coordination Polymer Precursor

A new three-dimensional Cd(II) coordination polymer, {[Cd₃(3-pyc)₄(NCS)₂(H₂O)₄]·2H₂O} _n (1); 3-Hpyc = 3-pyridinecarboxylic acid, was prepared and characterized by elemental analyses and IR spectroscopy. Compound 1 was structurally characterized by single-crystal X-ray diffraction. The structural determination shows that the compound is a new 3D coordination polymer has different environments containing CdO₅NS and CdO₂N₄ units. This polymeric precursor has been used in the preparation of Cd₃OSO₄ nanoparticles by thermolysis in oleic acid. The new nano-structure of Cd₃OSO₄ was characterized by scanning electron microscopy and X-ray powder diffraction. This study demonstrates that coordination polymers may be suitable precursors to the preparation of desirable nanoscale materials.     

A study of the lithium intercalation into nanoparticles of LiCoO<Subscript>2</Subscript> from an aqueous solution

Nanoparticles of lithium cobalt oxide (LiCoO₂) were synthesized by means of a citrate sol–gel combustion route. The particles were characterized by scanning and transmission electron microscopies (SEM and TEM), energy-dispersive X-ray spectroscopy, and X-ray diffraction (XRD) measurements. Near spherical nanoparticles of around 100 nm were observed in SEM and TEM micrographs. XRD data indicated that the as-prepared nanoparticles presented pure phase of LiCoO₂ with R-3m symmetry. The kinetics of electrochemical intercalation of lithium into the nanoparticles were investigated by means of cyclic voltammetry (CV), chronoamperometry, and electrochemical impedance spectroscopy (EIS) with special emphasis on the application potential as cathode material for aqueous rechargeable lithium batteries. CV studies of the nanoparticles at slow scan rate of 0.1 mV s⁻¹ between 600 and 820 mV versus Ag/AgCl, demonstrated that the nanoparticles represented well-defined reversible peaks. The non-linear chemical diffusion of lithium into the nanoparticles was explored by EIS. In this regards, the results were discussed based on an equivalent circuit, distinguishing the kinetic properties of lithium intercalation. The kinetic parameters of lithium intercalation were obtained using the equivalent circuit, which were in good agreement with the experimental results. The changes of kinetic parameters of lithium intercalation with potential were also discussed in detail.     

Investigation of a new lead-free Bi<Subscript>0.5</Subscript>(Na<Subscript>0.40</Subscript>K<Subscript>0.10</Subscript>)TiO<Subscript>3</Subscript>-(Ba<Subscript>0.7</Subscript>Sr<Subscript>0.3</Subscript>)TiO<Subscript>3</Subscript> piezoelectric ceramic

Lead-free piezoelectric compositions of the (1-x)Bi_0.5(Na_0.40K_0.10)TiO₃-x(Ba_0.7Sr_0.3)TiO₃ system (when x = 0, 0.05, 0.10, 0.15, and 0.20) were fabricated using a solid-state mixed oxide method and sintered between 1,050°C and 1,175°C for 2 h. The effect of (Ba_0.7Sr_0.3)TiO₃ [BST] content on phase, microstructure, and electrical properties was investigated. The optimum sintering temperature was 1,125°C at which all compositions had densities of at least 98% of their theoretical values. X-ray diffraction patterns that showed tetragonality were increased with the increasing BST. Scanning electron micrographs showed a slight reduction of grain size when BST was added. The addition of BST was also found to improve the dielectric and piezoelectric properties of the BNKT ceramic. A large room-temperature dielectric constant, ε _r (1,609), and piezoelectric coefficient, d ₃₃ (214 pC/N), were obtained at an optimal composition of x = 0.10.     

Fabrication of Silver Nanoparticles and 3D Interpenetrated Coordination Polymer Nanorods from the Same Initial Reagents

Nanorods of the three-dimensional coordination polymer, [Ag₂(μ ₂-py-4-c)₂] _n (1) [py-4-c⁻ = pyridine-4-carboxylate], have been synthesized by sonochemical process. The single-crystal X-ray data of compound 1 shows the formation of a 3D interpenetrated silver(I) coordination polymer, which has agostic interactions around the silver(I) ions and two types of Ag^I ions with O₂NAg1···O₂H, N₂ Ag2···O₂H₂ coordination spheres. Silver nanoparticles were fabricated from thermal decomposition of 1 nanorods. These nanostructures were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The thermal stability of 1 was studied by thermo gravimetric (TG) and differential thermal (DT) analysis.     

Preparation and characterization of spindle-like Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> mesoporous nanoparticles

Magnetic spindle-like Fe₃O₄ mesoporous nanoparticles with a length of 200 nm and diameter of 60 nm were successfully synthesized by reducing the spindle-like α-Fe₂O₃ NPs which were prepared by forced hydrolysis method. The obtained samples were characterized by transmission electron microscopy, powder X-ray diffraction, attenuated total reflection fourier transform infrared spectroscopy, field emission scanning electron microscopy, vibrating sample magnetometer, and nitrogen adsorption-desorption analysis techniques. The results show that α-Fe₂O₃ phase transformed into Fe₃O₄ phase after annealing in hydrogen atmosphere at 350°C. The as-prepared spindle-like Fe₃O₄ mesoporous NPs possess high Brunauer-Emmett-Teller (BET) surface area up to ca. 7.9 m² g^-1. In addition, the Fe₃O₄ NPs present higher saturation magnetization (85.2 emu g^-1) and excellent magnetic response behaviors, which have great potential applications in magnetic separation technology.     

Preparation of Cadmium(II) Oxide Nanoparticles from a New One-Dimensional Cadmium(II) Coordination Polymer Precursor; Spectroscopic and Thermal Analysis Studies

A one-dimensional Cd(II) coordination polymer containing 2-pyridinecarboxylate (2-pyc⁻) and iodide anions [Cd(μ-2-pyc)(μ-I)] _n (1), is synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis and X-ray crystallography. The single-crystal X-ray data show that the coordination number for the Cd²⁺ ion is five. The thermal stability of 1 was studied by thermogravimetry and differential thermal analyzes. Cd(II)O nanoparticles were prepared by direct calcination of 1 at different temperatures. The Cd(II)O nanoparticles were characterized by X-ray powder diffraction and scanning electron microscopy. The results show that the morphology of the Cd(II)O nanoparticles is dependent upon the thermolysis temperature.     

A Novel 3D Photoactive Coordination Polymer with Alternate Cd(H<Subscript>2</Subscript>O)<Superscript>2+</Superscript> and Mg(Hen)<Superscript>3+</Superscript> Units and Sandwich-Shaped Cluster Linkages

A novel organic–inorganic hybrid, cadmium(II)-magnesium(II)-molybdenum(V) phosphate, {Cd[(PO₄)₂(HPO₄)₂Mo₆O₁₁(OH)₄]₂}[Cd(H₂O)]₂[Mg(Hen)]₂{Cd[(PO₄)₃(HPO₄)Mo₆O₁₀(OH)₃Cl₂]₂}·(H₂en)₄·(Hen)₂·(en)₂·9H₂O (en = ethylenediamine), was prepared under hydrothermal conditions and characterized by single-crystal X-ray diffraction, X-ray powder diffraction, elemental analysis, inductively coupled plasma (ICP) analysis, thermogravimetric analysis, fluorescence, FT-IR and bond valence sum calculations. As revealed by single-crystal X-ray diffraction studies, the sandwich-shaped clusters of [Cd(Mo₆P₄)₂] are interconnected by additional [Mg(Hen)] units and [Cd(H₂O)] fragments to form an extended three-dimensional supramolecular framework with channels occupied by ethylenediamine molecules, protonated ethylenediamine cations and water molecules. Luminescent measurement of the title compound exhibits intensive blue and greenish-blue radiation emission upon excitation with ultraviolet light.     

Soft Template Synthesis of Super Paramagnetic Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles a Novel Technique

The present study reports a facile technique for the synthesis of crystalline super paramagnetic nano ferrite (Fe₃O₄) particles using diethyl amine as a soft template. The spectral properties of Fe₃O₄ nanoparticles were characterized by UV–visible and Fourier Transform Infrared (FTIR) spectroscopies while the crystalline structure and particle size was estimated using X-Ray diffraction (XRD) as well as transmission electron microscopy (TEM) techniques. The super paramagnetic behavior of Fe₃O₄ nanoparticles was determined using vibrating sample magnetometer (VSM) at 300 K. The results of the studies revealed that this technique could be adopted to synthesize agglomerate free super paramagnetic Fe₃O₄ nanoparticles which may find potential application in the filed of biosensor and corrosion protective coatings.     

Synthesis and crystal structure of the low-temperature modification of Li<Subscript>12</Subscript>Zn<Subscript>4</Subscript>(P<Subscript>2</Subscript>O<Subscript>7</Subscript>)<Subscript>5</Subscript>

The crystal structure of a low-temperature modification of the Li₁₂Zn₄(P₂O₇)₅ compound has been determined by full-profile analysis from the X-ray powder diffraction data. The compound crystallizes in the monoclinic crystal system (a = 5.130(1) Å, b = 13.454(1) Å, c = 8.205(1) Å, β = 90.36(1)°, space group P2₁/n, Z = 4) and has a framework structure in which the zinc and lithium atoms statistically occupy equivalent positions.     

Heat treatment of silica-fiber-reinforced BN-Si<Subscript>3</Subscript>N<Subscript>4</Subscript> matrix composite

A new wave-transparent composite reinforced by silica fibers with a hybrid matrix comprising BN and Si₃N₄ was prepared by precursor infiltration and pyrolysis, and it was heat-treated at elevated temperatures. The variations of the composite during heat treatments were characterized and investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The as-received composite exhibits good mechanical properties, and it is almost amorphous. When treated at 1600°C, it turned brittle, and silica fibers in it were fused; the composite showed a good crystalline form. When treated at 2100°C, the composite broke into pieces, and the composition showed only BN. Si₃N₄ was decomposed, and silica fibers were volatilized. The presence of BN probably affected the phase transitions of silica fibers. __________ Translated from Novye Ogneupory, No. 8, pp. 49–52, August 2007.     

Electrochemical properties of microwave-assisted reflux-synthesized Mn<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles in different electrolytes for supercapacitor applications

The nanosized Mn₃O₄ particles were prepared by microwave-assisted reflux synthesis method. The prepared sample was characterized using various techniques such as X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), Raman analysis, and transmission electron microscopy (TEM). Electrochemical properties of Mn₃O₄ nanoparticles were investigated using cyclic voltammogram (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge analysis in different electrolytes such as 1 M KCl, 1 M Na₂SO₄, 1 M NaNO₃, and 6 M KOH electrolytes. XRD pattern reveals the formation of single-phase Mn₃O₄ nanoparticles. The FT-IR and Raman analysis also assert the formation of Mn₃O₄ nanoparticles. The TEM image shows the spherical shape particles with less than 50 nm sizes. Among all the electrolytes, the Mn₃O₄ nanoparticles possess maximum specific capacitance of 94 F g⁻¹ in 6 M KOH electrolyte calculated from CV. The order of capacitance obtained by various electrolytes is 6 M KOH > 1 M KCl > 1 M NaNO₃ > 1 M Na₂SO₄. The EIS and galvanostatic charge–discharge results further substantiate with the CV results. The cycling stability of Mn₃O₄ electrode reveals that the prepared Mn₃O₄ nanoparticles are a suitable electrode material for supercapacitor application.     

Preparation and properties of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> nanorods as supercapacitor material

Co₃O₄ nanorods have been successfully synthesized by thermal decomposition of the precursor prepared via a facile and efficient microwave-assisted hydrothermal method, using cetyltrimethylammonium bromide (CTAB) with ordered chain structures as soft template for the first time. The obtained Co₃O₄ was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical measurements. The results demonstrate that the as-synthesized nanorods are single crystalline with an average diameter of about 20 to 50 nm and length up to several micrometers. Preliminary electrochemical studies, including cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) measurements, are carried out in 6 M KOH electrolyte. Specific capacitance of 456 F g⁻¹ for a single electrode could be achieved even after 500 cycles, suggesting its potential application in electrochemical capacitors. This promising method could provide a universal green chemistry approach to synthesize other low-cost and environmentally friendly transition metal hydroxide or oxide.