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.     

First 3D coordination polymer built from Ho(III) and 2-aminoterephthalate ligand

Novel three-dimensional (3D) coordination polymer {[Ho₂(μ₃-ATA)₂(μ₄-ATA)(H₂O)₄]·2DMF·1/2H₂O}_n (1), built from Ho(III) cations and 2-aminoterephthalate anionic ligands (ATA^2 −) was prepared and studied. The compound 1 contains 1D structural channels with the size 4.1 × 6.8 Å², which propagate along b crystallographic axis. The channels are filled with the solvent molecules. The Ho(III) atom is eight-coordinated with distorted square anti-prismatic geometry. Complex was characterized by single crystal X-ray diffraction, thermogravimetry coupled with simultaneous evolved gas analysis using mass spectrometry (TG/DTG–DTA–EGA), powder X-ray diffraction (PXRD), infrared spectroscopy (FT-IR), solid-state UV–VIS spectroscopy and nitrogen adsorption at 77 K. After the desolvation the 1D structural channels collapse. The process is accompanied by structure transformation, however, according to the TG–DTA–EGA results, the Ho–ATA polymeric framework is stable up to 450 °C.     

Cooperative Effect of 3,3′,4,4′-Benzophenonetetracarboxylic Acid and 1,10-Phenanthroline under Solvothermal Conditions to Afford Two Novel Zinc(II) and Cadmium(II) Complexes

Rational self-assembly of a flexible ligand 3,3′,4,4′-benzophenonetetracarboxylic acid and d¹⁰ transition metal salts in the presence of rigid bidentate ligand 1,10-phenanthroline yields two novel helical coordination polymers with different structural motifs; i.e., [Zn(H₂bbtc)(phen)₂ · 2H₂O] _n (1) and [Cd₂(bbtc)(phen)₄ · 2.25H₂O] _n (2) (H₄bbtc = 3,3′,4,4′-benzophenonetetracarboxylic acid, phen = 1,10-phenanthroline), under solvothermal condition. One is hydrogen bonded and π–π stacked together into a network, and the other is a covalently coordinated 3D framework. The coordination polymers were characterized by FT-IR, UV/VIS and fluorescent spectroscopy, single crystal X-ray diffraction, elemental analysis and differential thermal analysis/thermogravimetry (DTA/TG). The most intriguing structural feature is that each complex exhibits novel helical-spaced chains by reason of two different ligands coordinating to the metal centers. Additionally, compounds 1 and 2 showed good fluorescence properties compared to the free ligands.     

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).     

Hydrothermal Syntheses and Crystal Structures of Three Zn(II) Coordination Compounds Constructed with 3,5-Pyrazoledicarboxylic Acid

Three novel metal–organic coordination compounds, [Zn(Hdcp)(H₂O)₄]·1.5H₂O (1), [Zn(Hdcp)(H₂O)₂]_∞ (2) and [Zn₃(dcp)₂(H₂O)₅]_∞ (3) with the ligand 3,5-pyrazoledicarboxylic acid were prepared by the hydrothermal method. The complexes were structurally characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction. Compound 1 is a mononuclear molecule that is linked into a 3D supramolecular framework via N–H···O and O–H···O hydrogen bonds. In 2, two types of carboxylic bridges were found between Zn^II ions to form a 1D double-chain. The 1D chains were further construct into a 3D structure by hydrogen bonds. Trinuclear 3 consists of 1D bi-infinite parallelogram chains of [Zn₃(dcp)₂(H₂O)₃] trimers. In the basic trinuclear unit a further bridging mode of the ligand is seen where two dcp^3? ligands chelate three Zn^II ions by utilizing five donors of the dcp^3? ligand. The photoluminescent properties of 1, 2 and 3 were investigated.     

Electrokinetic Properties of Vermiculite and Expanded Vermiculite: Effects of pH,Clay Concentration and Mono- and Multivalent Electrolytes

Abstract

In this study, the zeta potential values of vermiculite and expanded vermiculite were measured to determine the effect of pH, clay concentration, and various mono- and multivalent electrolytes including NaCl, KCl, NH₄Cl, NaNO₃, NaClO₄, Na₂SO₄, Na₂CO₃, Na₃PO₄·12H₂O, MgCl₂·6H₂O, CaCl₂·2H₂O, BaCl₂, SrCl₂·6H₂O, CuCl₂·2H₂O, CoCl₂·6H₂O, NiCl₂, AlCl₃, and CrCl₃·6H₂O on the electrokinetic properties of vermiculite samples. It was found that generally the measured zeta potential values of expanded vermiculite for the studied systems were slightly more negative than that of vermiculite. The pH profiles of vermiculite and expanded vermiculite at acidic, natural, and basic pH values were obtained to determine the effect of time on the pH values of clay suspensions. The zeta potential measurements showed that the surface charge of clay particles was negative in water. The isoelectric point of vermiculite and expanded vermiculite were determined as pH 2.30 and 2.57, respectively. Divalent cations (Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺), heavy metal ions (Cu²⁺, Ni²⁺, and Co²⁺) and trivalent cations (Al³⁺ and Cr³⁺) were potential determining ions for vermiculite and expanded vermiculite particles. Moreover, divalent and trivalent cations caused the change of surface charge from negative to positive. On the other hand, monovalent cations (Na⁺, K⁺ and NH₄ ⁺), monovalent anions (Cl^?, NO₃ ^?, and ClO₄ ^?) and multivalent anions (SO₄ ^2?, CO₃ ^2?, and PO₄ ^3?) acted as indifferent ions for these clay particles.     

Preparation of Nano-ZrO2 powder via a microwave-assisted hydrothermal method

ZrO₂ nanocrystals were synthesised by a microwave-assisted hydrothermal method using zirconium oxychloride (ZrOCl₂·8H₂O), yttrium chloride (YCl₃·6H₂O), and liquor ammonia (NH₃·H₂O) as raw materials, triethanolamine (TEOA) as mineraliser, and polyethylene glycol (PEG) as dispersant. The obtained products were characterised with thermogravimetry-differential scanning calorimetry (TG-DSC), Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results show that the concentration of ZrOCl₂·8H₂O had little effect on the material properties, whereas the PEG molecular weight, microwave hydrothermal time and temperature, and the concentration of TEOA greatly influenced the dispersibility of the nano-sized zirconia powders. XRD and FT-IR analyses indicated that the ZrO₂ nanocrystals synthesised by the microwave hydrothermal method had a tetragonal phase without any trace of monoclinic or cubic phases. The optimal parameters for preparing nano-zirconia powders with appreciable crystallinity and crystal forms included the use of PEG1000/PEG2000/PEG4000 dispersants, a microwave hydrothermal time of 30–50 min and a temperature of 200–240 °C, and a TEOA concentration of 0.3–0.5 M. Nano-ZrO₂ powder prepared via our optimised microwave hydrothermal method contained mostly tetrahedral, spherically shaped, highly homogeneous, and well-dispersed 20–30 nm particles.     

Dispersion and Solid State Ion Exchange of VCl3, CrCl3?6H2O, MnCl2?4H2O and CoCl2?6H2O onto the Surface of NaY Zeolite Using Microwave Irradiation

Transition metal/Y zeolites have been prepared by solid state ion exchange with microwave irradiation of mechanical mixtures of VCl₃, CrCl₃ ⋅ 6H₂O, MnCl₂ ⋅ 4H₂O or CoCl₂ ⋅ 6H₂O with NaY zeolite at 900 W in 10–20 min. The prepared transition metal/Y zeolites were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), simultaneous thermal analysis (STA) and surface area measurement (BET). Concentration of dispersed transition metal on zeolite was measured and results revealed that transition metal was dispersed and ion exchanged onto the surface of NaY zeolite.     

One Step Synthesis of NiO Nanoparticles via Solid-State Thermal Decomposition at Low-Temperature of Novel Aqua(2,9-dimethyl-1,10-phenanthroline)NiCl2 Complex

[NiCl₂(C₁₄H₁₂N₂)(H₂O)] complex has been synthesized from nickel chloride hexahydrate (NiCl₂·6H₂O) and 2,9-dimethyl-1,10-phenanthroline (dmphen) as N,N-bidentate ligand. The synthesized complex was characterized by elemental analysis, infrared (IR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy and differential thermal/thermogravimetric analysis (TG/DTA). The complex was further confirmed by single crystal X-ray diffraction (XRD) as triclinic with space group P-1. The desired complex, subjected to thermal decomposition at low temperature of 400 ºC in an open atmosphere, revealed a novel and facile synthesis of pure NiO nanoparticles with uniform spherical particle; the structure of the NiO nanoparticles product was elucidated on the basis of Fourier transform infrared (FT-IR), UV-vis spectroscopy, TG/DTA, XRD, scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDXS) and transmission electron microscopy (TEM).     

Enhancing the electrical conductivity of vanadate glass system (Fe2O3, B2O3, V2O5) via doping with sodium or strontium cations

Novel glass-ceramics of the nominal molar compositions 20Fe₂O₃·20B₂O₃·(60-x)V₂O₅· (xNa₂O or xSrO) (where x?=?0 or 10) were prepared by traditional melt technique. Differential thermal analysis (DTA) was implemented to study the thermal behavior of the prepared glasses. Vanadium pentoxide (V₂O₅), iron vanadate (FeVO₄), sodium vanadate (Na₃VO₄) and strontium vanadate (with different formulae) were crystallized and identified by X-ray diffraction (XRD) analysis under certain conditions of heat-treatment. Further characterization of glass and glass ceramics samples were performed using scanning electron microscope (SEM), density, electrical and dielectric measurements. In conclusion, our study elucidated that the substitution of vanadium by Na⁺ and Sr²⁺ ions enhanced the conductivity at 180?°C from 5.11?×?10^?4 for unmodified glass to 2.93?×?10^?3 and 1.03?×?10^?2?S?cm^?1 for Na- and Sr-modified glasses.     

Hydrothermal synthesis and characterization of nanorods “LixV2−δO4−δ·H2O”

Nanorods “Li_xV_2−δO_4−δ·H₂O” were hydrothermally synthesized with starting agents LiOH·H₂O and V₂O₅, and reducing agent hydrazine monohydrate (NH₂NH₂·H₂O) under alkaline condition at 160 °C. The samples were characterizated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The nanorods obtained have diameters from 80 to 100 nm with length up to several micrometers. Molecular coordination and assembly mechanism can be assumed to explain the formation of one-dimensional nanorods.     

A Novel Binodal (4,9)-Connected 3D Calcium Coordination Polymer: Synthesis, Characterization, Thermal Stability and Luminescent Properties

A novel coordination polymer, namely, [Ca₃(BIPA)₃(H₂O)₃·H₂O] _n (1) has been prepared by the reaction of 5-bromoisophthalic acid (H₂BIPA) with corresponding Ca(II) ions, and characterized by single-crystal X-ray diffraction, element analysis, infrared spectroscopy, thermogravimetric analysis In compound 1, a trimer unit [Ca₃O₁₉] is bridged the carboxylate oxygen atoms, forming an inorganic layer structure. The inorganic layers are linked by the BIPA^2? ligands, resulting in a three-dimensional (3D) pillared layered structure with a binodal (4,9)-connected 3D net structure with Schläfi symbol of (3⁴·4²)(3⁸·4¹⁰·5¹²·6⁶). In compound 1, the carboxylate groups of the BIPA^2? ligands coordinate to calcium ions using different coordinated modes. In addition, the thermal stability and luminescent properties of 1 were also investigated.     

Supramolecular Aggregation of Tetrameric and Homododecameric Water Clusters in a 1D Cobalt(II) Coordination Polymer Containing 1,2,4,5-Benzenetetracarboxylate

A ternary mixed ligand Co(II) coordination polymer, namely, {[Co(L)(btec)_0.5(H₂O)]·3H₂O} _n , (L?=?1,4-bis(thiabendazole)butane, H₄btec?=?1,2,4,5-benzenetetracarboxylic acid) has been hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction analysis. The coordination polymer features a 1D wave-like chain, which is further extended into a 3D supramolecular framework via O–H?O hydrogen bonding interactions. It is noteworthy, the chair-shaped homododecamers and quasirectangle teteramers assemble with the 1D loose-string-like water-btec^4? chain into a unusual boxing-glove-like 2D water layer. Hirshfeld surface analysis and fingerprint plots show that the coordination polymer is stabilized by O–H?O, π?π, O–H?π, and H?H intermolecular interactions. Furthermore, thermal behaviors, luminescence and catalytic properties of the coordination polymer for degradation of methyl orange in a Fenton-like process have been investigated.     

Synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones using ZrOCl2/mont K10 under microwave assisted solvent-free conditions

ZrOCl₂·8H₂O supported on montmorillonite K10 (ZrOCl₂/mont K10) catalyzed Biginelli reaction under solvent-free conditions is reported. The catalysts were characterized by XRD, FTIR, BET surface area analysis, and thermogravimetric analysis. The activity of montmorillonite K10, montmorillonite KSF, ZrOCl₂·8H₂O, SO₄ ^2?/ZrO₂, and ZrOCl₂/mont K10s was investigated by Biginelli reaction of benzaldehyde, ethylacetoacetate and urea. The reactions were carried out by addition of ZrOCl₂/mont K10 to a mixture of aldehyde, ethylacetoacetate and urea/thiourea with thorough stirring in the absence of solvent under conventional heating or microwave irradiation to prepare 3,4-dihydropyrimidin-2(1H)-one/thione derivatives at 80?°C in good yields.     

Assembly,Fluorescent and Adsorption Properties of Two Cadmium(II)/Cobalt(II) Coordination Complexes Functionalized by the Flexible Bis(Pyridyl)-bis(Amide) Ligand

A new cadmium(II) and a new cobalt(II) coordination complexes [Cd₅(BTB)₄(HL)₂]·2H₂O (1) and [Co(HBTB)(L)]·2H₂O (2) [H₃BTB?=?1,3,5-tri(4-carboxylphenyl)benzene, L?=?N,N′-bis(3-pyridyl)octandiamide] were prepared under the solvothermal conditions by the assembly of cadmium(II)/cobalt(II) chloride, the flexible bis(pyridyl)-bis(amide) ligand L and the aromatic tricarboxylic acid H₃BTB. The structures of complexes 1–2 have been characterized by X-ray single crystal diffraction analyses, infrared spectroscopy (IR), powder X-ray diffraction (PXRD) and thermogravimetric (TG) analyses. Complex 1 is a 3D metal–organic network with the penta-nodal (2,4,4,5,6)-connected {4·6³·8·10}₂{4²·6⁵·8³}₂{4³·6³}₂{4⁶·8⁹}{6}₂ topology constructed from the 3D [Cd₅(BTB)₄]_n^2n? coordiantion framework and the protonated HL ligands. Complex 2 displays a binodal (4,4)-connected {6⁴·8·10}{6} topological 2D layered architecture based on the 1D [Co(HBTB)]_n chains and the 1D [CoL]_n chains, which are further linked by hydrogen bonding interactions to form a 3D supramolecular network. Moreover, the fluorescent properties of the cadmium(II) complex and the dyes adsorption performances of complexes 1–2 have been studied.     

Studies on cermet behavior of Ni doped YSZ

A simple and cost effective combustion process is employed to prepare Ni/YSZ cermet from an aqueous solution containing ZrO(NO₃)₂·6H₂O, Y(NO₃)₃·6H₂O, Ni(NO₃)₂·6H₂O and urea followed by H₂ reduction. As prepared cermet was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy techniques. Processed powder of NiO-YSZ was found to be in crystalline form with homogeneous mixture of YSZ and NiO phases. On reduction, its mixed conductivity is suppressed partially. The impedance and dielectric properties of the cermet were studied over a frequency range 10?Hz to 2?MHz at different temperatures. M ? H behavior at different temperature (down to 5?K) including ZFC and FC at 500?Oe were studied. To understand and corroborate the conductivity behavior and mechanism involved with the magnetic Ni ion mediated YSZ cermet, we have also studied the electric field induced polarization behavior and predict that Ni magnetic ion has specific role towards the contribution of conductivity mechanism generally included in Ni/YSZ cermet used for SOFC applications.     

Metal Chelates with Some Cellulose Derivatives: V. Synthesis and Characterization of Some Iron(III) Complexes with Cellulose Ethers

Two types of monoligand complexes of FeCl₃, Fe(NO₃)₃ and Fe₂(SO₄)₃ with hydroxyethyl cellulose (HEC) and carboxymethyl cellulose (CMC) were prepared and characterized. Elemental analysis, UV and IR spectro-scopies, conductance and magnetic measurements were used to assign the mode of coordination in the isolated species. The investigation revealed that Fe(III ) exhibits tetrahedral coordination with HEC and CMC. These ligands act as a bidentate chelating agent via the two oxygen atoms of the vicinal hydroxyl and ether groups (ethoxyl or carboxymethyl groups). The prepared complexes have the formula [(HEC) FeCl]Cl, [(HEC) FeNO₃]NO₃, [(HEC)FeSO₄·H₂O]H₂O, [(CMC)FeCl·H₂O]Cl·2H₂O, [(CMC)Fe·2NO₃]3H₂O and [(CMC)-FeSO₄·H₂O]H₂O. The results also showed that the type of cellulose ether (functional group) and the anion of the metal salts used have an effect on the conductivity, structure and absorptivity of Fe(III ) complexes. © of SCI.     

Hydrothermal Synthesis, Crystal Structure and Characterization of New Coordination Polymer [Co2(pydc)2(H2O)6] n ·2nH2O

A coordination polymer of cobalt(II) containing the pyridine-2,5-dicarboxylate (pydc) ligand and having the composition [Co₂(pydc)₂(H₂O)₆] _n ·2nH₂O was prepared by the hydrothermal method. The coordination polymer was characterised by FTIR, single crystal XRD, SEM, TGA–DTA, and N₂ Temperature Programmed Desorption, Brunauer, Emmett and Teller surface area. The polymer contains two cobalt(II) ions with slightly distorted octahedral geometry. The carboxylate group at the 2-position of pyridine acts as a bridging ligand between two cobalt metal ions and this expansion leads to formation of a 1-D chain-like coordination polymer. The coordination polymer chains are packed together by well-directed hydrogen bonds to generate a three dimensional mesoporous network. The N₂ TPD study shows that the polymer is mesoporous in nature and possesses slit-shaped mesopores with average pore size diameter of 17.78 nm. SEM micrographs show well-defined channels in the solid crystals confirming the porosity of polymer. Thermogravimetric studies indicate the robust nature of the polymer. The polymer undergoes thermal decomposition in well-defined steps leading to the formation of cobaltous oxide as the end-product.     

An aluminoborate directed by [Zn(H2O)4]2 + complex: Synthesis,structure and properties

A novel 3D aluminoborate with [Zn(H₂O)₄]²⁺ cationic complexes as structure-directing agents (SDAs), namely, [Zn(H₂O)₄][Al(B₅O₁₀)]·0.5(H₂O) (1), has been solvothermally prepared and characterized by IR spectroscopy, UV–vis reflection spectroscopy, thermogravimetric (TG) analyses, powder and single crystal X-ray diffraction, respectively. The alternative linkage of AlO₄ tetrahedra and B₅O₁₀ units produces an open-framework aluminoborate with helical 6- and 8-membered ring (MR) channels, as well as large odd 11-MR channels. The [Zn(H₂O)₄]²⁺ templates, generated in situ from solvothermal conditions, are orderly located in the center of the 11-MR channels. The second-harmonic generation (SHG) measurement indicates that 1 exhibits about 0.5 times that of KDP standard (K₂HPO₄).     

Preparation of UC ceramic nuclear fuel microspheres by combination of an improved microwave-assisted rapid internal gelation with carbothermic reduction process

Uranium carbide (UC) ceramic microspheres filled into a cladding are a potential nuclear fuel format for nuclear reactors. Uniform sized ceramic UC microspheres with a diameter of 675?±?10?µm were successfully prepared by an improved microwave-assisted rapid internal gelation process combined with carbothermic reduction. First of all, the nanoparticle carbon was dispersed into the HMUR stock solution, and the C-UO₃·2H₂O gelled microspheres were prepared using an improved microwave-assisted internal gelation process without cooling the initial stock solutions. Next, the gelled microspheres were subjected to a carbothermic reduction process to obtain ceramic UC microspheres. TG and XRD investigations indicated that the C-UO₃·2H₂O microspheres were firstly reduced into UO₂ at a temperature of 700?°C, and were further converted into UC at 1500?°C in argon atmosphere. Crack-free ceramic UC microspheres with a smooth and metallic shiny surface were obtained at a sintering temperature of 1500?°C for 5?h with an initial C/U molar ratio of 3.5.