Sonochemical Synthesis of Spherical Silica Nanoparticles and Polymeric Nanocomposites

In this work spherical SiO₂ nanoparticles were synthesized by sonochemical method using a new Schiff-base as a capping agent. The silica nanoparticles were obtained by hydrolysis of tetraethyl orthosilicate in aqueous alcohol solution. The effect of different parameters such as molar concentration of Schiff-base ligands and ultrasonic irradiation on the morphology and size of the products was examined. The results demonstrated that applying the appropriate amount of Schiff-base could be effective in control of particle size. The influence of SiO₂ nanostructures on the flame retardancy of the poly styrene, poly vinyl alcohol, cellulose acetate and ethyl cellulose was studied. In-situ and ex situ nanocomposites were investigated and results confirm that flame retardancy of in situ nanocomposites were better than ex situ samples. HO···Si–O–Si···OH barrier prevents reaching of flame, heat and oxygen to the polymeric nanocomposites.     

Sonochemical and solvothermal synthesis of methanol {2-[(2-hydroxy-1,1-dimethyl-ethylimino)-methyl]phenolato}-dioxidomolybdenum(VI) complex and its decomposition to MoO<Subscript>3</Subscript> nanoparticles

As a new precursor to prepare nano molybdenum trioxide, methanol {2-[(2-hydroxy-1,1-dimethylethylimino)-methyl]phenolato}dioxidomolybdenum(VI) complex (1) with the Schiff base ligand (H₂L) is synthesized by two different methods: solvothermal and sonochemical. Nanoparticles of 1 are obtained by one-pot solvothermal treatment of methanolic solutions of the ligand and di-oxomolybdenyl acetylacetonate at 150°C for 24 h and for improving the quality of nanostructures by sonochemical method with two types of solvents, different concentrations of initial reagents and also different sonication times. The thermal stability of nanosized compound 1 is studied by thermal gravimetric (TG) analysis and differential scanning calorimetry (DSC). Nanoparticles of orthorhombic α-MoO₃ are obtained by calcination of nanostructures of compound 1 at 700°C. All compounds and the obtained molybdenum trioxide nanostructures are characterized by elemental analysis, FT-IR, UV-Vis spectroscopy, X-ray powder diffraction (XRD), and scanning electron microscopy (SEM).     

Syntheses and structures of 2-bromo-4-chloro-6- (cyclopropyliminomethyl)phenol and its zinc(II) complex

A new Schiff-base ligand 2-bromo-4-chloro-6-(cyclopropyliminomethyl)phenol and its zinc(II) complex have been synthesized and characterized by elemental analyses, infrared spectroscopy, ¹H NMR, ¹³C NMR, and single crystal X-ray determinations. The ligand and the complex crystallized in the space groups Pnma and P2₁/c, respectively. In the complex, the Zn atom is four-coordinate tetrahedral coordination with two imine N and two phenolate O atoms from two Schiff-base ligands. The bond lengths related to the donor atoms in the complex are different from those in the ligand. The coordination of the ligand to the zinc also was supported by IR spectra.     

Synthesis and DNA binding studies of Ni(II), Co(II), Cu(II) and Zn(II) metal complexes of N1,N5-bis[pyridine-2-methylene]-thiocarbohydrazone Schiff-base ligand

The thiocarbohydrazone Schiff-base ligand with a nitrogen and sulphur donor was synthesized through condensation of pyridine-2-carbaldehyde and thiocarbohydrazide. Schiff-base ligands have the ability to conjugate with metal salts. A series of metal complexes with a general formula [MCl2(H2L)]·nH2O (MNi, Co, Cu and Zn) were synthesized by forming complexes of the N1,N5-bis[pyridine-2-methylene]-thiocarbohydrazone (H2L) Schiff-base ligand. These metal complexes and ligand were characterized by using ultraviolet-visible (UV-Vis), Fourier Transform Infrared (FT-IR), 1H and 13C NMR spectroscopy and mass spectroscopy, physicochemical characterization, CHNS and conductivity. The biological activity of the synthesized ligand was investigated by using Escherichia coli DNA as target. The DNA interaction of the synthesized ligand and complexes on E. coli plasmid DNA was investigated in the aqueous medium by UV-Vis spectroscopy and the binding constant (Kb) was calculated. The DNA binding studies showed that the metal complexes had an improved interaction due to trans-geometrical isomers of the complexes than ligand isomers in cis-positions.     

Syntheses and characterization of a new nano-structured bismuth(III) bromide coordination polymer; new precursor for preparation of bismuth(III) bromide and bismuth(III) oxide nanostructures

Nanoparticles of a Bi(III) coordination polymer, {[Bi(μ-4,4′-bipy)Br₄] · (4,4′-Hbipy)} _n (1) (4,4′-bipy = 4,4′-bipyridine), were synthesized by a sonochemical method. The new nanoparticles were characterized by scanning electron microscopy, X-ray powder diffraction (XRD), IR spectroscopy, and elemental analyses. Compound 1 was structurally characterized by single-crystal X-ray diffraction. The thermal stabilities of 1 as bulk and at nanosize were studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The Bi₂O₃ and BiBr₃ nanostructures were obtained by calcinations of nanostructure of 1 in air and argon.     

Shape control of nanostructured TiO2 using a Schiff base ligand via sol–gel hydrothermal method

Employing a Schiff base ligand in a hydrothermal sol–gel method for preparation of TiO₂ nanostructures was studied. The as-prepared products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectrum, electron dispersive X-ray spectroscopy and ultraviolet–visible spectroscopy. It is shown that in the controlled reaction conditions, a Schiff base ligand containing hard atoms is capable of driving the growth mechanism in a way that anisotropic shapes of TiO₂ nanostructures are formed. Considering the structure of the Schiff base ligand, the possible growth mechanism of TiO₂ nanostructures is proposed. The optical studied as well as calculated molecular orbital structure of ligand by density functional theory is done.     

Synthesis and Characterization of Cu2S Nanostructures Via Hydrothermal Method by a Polymeric Precursor

Cu₂S nanostructures were synthesized successfully via hydrothermal approach with new precursor. The precursor was characterized via thermal gravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR). The products were characterized with X-ray diffraction, scanning electron microscopy, transition electron microscopy, energy-dispersive X-ray spectroscopy, FT-IR, room temperature photoluminescence spectroscopy and ultraviolet–visible spectroscopy. The effect of different parameters such as Cu²⁺/TGA mole ratio, reaction time and temperature were investigated on product size and morphology.     

Syntheses,crystal structures,and antibacterial activities of two cobalt(III) complexes

Syntheses, structures, and antimicrobial activities of cobalt(III) complexes with two tetradentate Schiff-base ligands, (BA)₂en?=?bis(benzoylacetone)ethylenediimine dianion and (acac)₂en?=?bis(acetylacetone)ethylenediimine dianion, and two axial pyridines (py) have been investigated. These complexes were characterized by FT-IR, ¹H-NMR, UV-Vis spectroscopy, and elemental analysis. The crystal structures of the complexes were determined by X-ray crystallography. Single-crystal X-ray diffraction analyses revealed that both complexes have distorted octahedral environments, Schiff-base ligand coordinates cobalt in four equatorial positions, and the two axial positions are occupied by pyridines. The pyridines and Schiff-base ligands are involved in N–H···O hydrogen bonds with perchlorate. Biological activities of the ligands and metal complexes have been studied on Staphylococcus aureus, Escherichia coli, and Bacillus subtilis by the well diffusion method. The activity data show the metal complexes to be more potent than the parent ligand against two bacterial species.     

Syntheses and crystal structures of two copper(II) complexes derived from 2-bromo-4-chloro-6-[(2-morpholin-4-ylethylimino)methyl]phenol

Two new copper(II) complexes, [CuL₂] (1) and [Cu₂L₂(NCS)₂] · 2CH₃CN (2) (HL = 2-bromo-4-chloro-6-[(2-morpholin-4-ylethylimino)methyl]phenol), have been synthesized and characterized by elemental analyses, infrared spectroscopy, and single-crystal X-ray diffraction. Complex 1 was synthesized by reaction of HL with copper(II) acetate in methanol, while 2 was synthesized by adding ammonium thiocyanate to a methanol/acetonitrile (V : V = 2 : 1) solution of 1. Complex 1 crystallizes in the P2₁/n space group, and the thiocyanato-bridged dinuclear copper(II) complex, 2, crystallizes in the Pbcn space group. The Cu in 1 is four-coordinate square-planar with two imine N and two phenolate O atoms from two Schiff-base ligands. The Cu in 2 is five-coordinate square-pyramidal with NNO donor atoms of one Schiff-base ligand and one N atom of a bridging thiocyanate ligand defining the basal plane, and with one S atom of another bridging thiocyanate ligand occupying the apical position.     

PbTe nanostructures: Microwave-assisted synthesis by using lead Schiff-base precursor,characterization and formation mechanism

Pure cubic phase lead telluride (PbTe) nanostructures have been produced by using a Schiff-base complex as a precursor in the presence of microwave irradiation. The Schiff base used as ligand was derived from salicylaldehyde and ethylenediamine. The Schiff-base complex was marked as [Pb(salen)]. In addition, the effect of the irradiation time and the type of reducing agent on the morphology and purity of the final products was investigated. The as-synthesized PbTe nanostructures were characterized extensively by techniques like X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The microwave formation mechanism of the PbTe nanostructures was studied by XRD patterns of the products. Although it was found that both ionic and atomic mechanisms could take place for the preparation of PbTe, the main steps were according to the atomic reaction process, which could occur between elemental Pb and Te.     

Synthesis, characterization, and crystal structure of two zinc(II) halide complexes with the symmetrical bidentate Schiff-base ligand (3,4-MeO-ba)2en

Abstract  

In this study two zinc(II) halide complexes with the Schiff-base ligand (3,4-MeO-ba)₂en [N,N′-bis(3,4-dimethoxybenzylidene)ethane-1,2-diamine] have been synthesized and characterized by elemental analyses (CHN), single-crystal X-ray diffraction, Fourier-transform infrared (FT-IR), and ¹H nuclear magnetic resonance (NMR) spectroscopy. The metal-to-ligand ratio was found to be 1:1 within the formula ZnX₂((3,4-MeO-ba)₂en) (X = Br, I). Crystal structure analysis reveals that the coordination geometry around the zinc(II) ions in the two isotypic complexes is distorted tetrahedral. The Schiff-base ligand (3,4-MeO-ba)₂en acts as a chelating ligand and coordinates via two N atoms to the metal center and adopts an (E,E) conformation. The coordination spheres of the metal atoms are completed by the two halide atoms, which are also involved in weak non-classical hydrogen-bonding interactions of the type C–H···X–Zn.     

Co-templating synthesis of highly dispersed 1D ZnO nanostructures in amorphous SiO2 under hydrothermal condition

One-dimensional (1D) ZnO nanostructures were grown in amorphous SiO₂ matrix by a co-templating method under hydrothermal condition. Using ethylenediamine (EDA) groups grafted mesoporous silica MCM-41 as a co-template, the growth of 1D ZnO nanostructures was oriented by soft EDA groups and confined inside the hard mesochannels of MCM-41. The microstructure and morphology of the 1D-ZnO-nanostructures/SiO₂ composite were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). All these results indicate that the 1D ZnO nanostructures were synthesized and highly dispersed in the amorphous SiO₂ matrix. Blue-shifted exciton absorption was observed from the co-templating synthesized sample.     

树枝状钯纳米结构的控制合成及硝基苯加氢反应的催化活性

以氯钯酸为前驱体, 苯甲醇为还原剂和溶剂, 十六烷基吡咯烷酮(PVP)为稳定剂, 在微波辐射下制备了分散均匀、形貌均一的树枝状钯纳米结构. 产物用透射电子显微镜(TEM), X射线粉末衍射(XRD), X射线光电子能谱(XPS)进行了表征, 表明所制备的Pd纳米颗粒呈树枝状, 形貌单一, 分散均匀, 是由许多近似圆形的小颗粒自组装而成的二级结构. 对树枝状钯催化硝基苯加氢反应进行探究, 表明树枝状钯的催化活性比市售的钯碳催化剂的催化活性高.     

Coordination compounds from the planar tridentate Schiff-base ligand 2-methoxy-6-((quinolin-8-ylimino)methyl)phenol (mqmpH) with several transition metal ions: Use of [Fe(mqmp)(CH3OH)Cl2] in the catalytic oxidation of alkanes and alkenes

Four coordination compounds were synthesized in high yields from different transition metal ions (Fe^III, Co^II, and Cu^II) and an in situ generated Schiff-base ligand, i.e. 2-methoxy-6-((quinolin-8-ylimino)methyl)phenol (mqmpH). The compounds were characterized by single-crystal X-ray diffraction, ESI-MS, IR spectroscopy, and ligand-field spectroscopy. The iron(III) complex is an efficient catalyst for the oxidation of alkanes and alkenes, under relatively mild conditions and with dihydrogen peroxide as terminal oxidant.     

Synthesis and Characterization of CdCO3 Nanostructures via Simple Hydrothermal Method

CdCO₃ nanostructures were synthesized via simple hydrothermal method by Cd(NO₃)₂, ethylenediamine and hydrazine as reagents. The products were characterized with X-ray diffraction scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. Different parameter’s effect on product size and morphology were investigated.     

Synthesis, Characterization, Photoluminescence and Photocatalytic Properties of CeO2 Nanoparticles by the Sonochemical Method

Uniform CeO₂ nanoparticles were synthesized via a facile sonochemical reaction between ceric ammonium nitrate and ammonia. Nanoparticles were synthesized via a surfactant free reaction at room temperature in solvent of water. Products were characterized using X-ray diffraction, scanning electron microscopy, photoluminescence (PL) spectroscopy, and energy dispersive X-ray analysis. The effect of different parameters such as precursor, power of pulsation, surfactant and reaction time on the morphology of the products was investigated. It was found that the as-obtained CeO₂ nanoparticles exhibit a strong PL peak at 381 nm at room temperature that can be ascribed to the high level transition in the CeO₂ semiconductor. The photocatalytic behavior of CeO₂ nanoparticles was evaluated using the degradation of a methyl orange aqueous solution under ultraviolet light irradiation. The results show that CeO₂ nanoparticles are promising materials with excellent performance in photocatalytic applications.     

Synthesis and structures of 3-chloro-N′-(2-hydroxy-benzylidene)benzohydrazide and its oxovanadium(V) complex

A new Schiff-base 3-chloro-N ′ -(2-hydroxybenzylidene)benzohydrazide (H₂BBH) and its oxovanadium(V) complex [VO(BBH)(OCH₃)]₂ have been synthesized and characterized by elemental analysis, infrared (IR) spectra, and single-crystal X-ray determination. Both the ligand and the complex crystallized in the monoclinic space group P2₁ /c. The Schiff-base coordinates to V through the phenolate O, the imine N, and the enolic O. In the centrosymmetric dimeric oxovanadium(V) complex, the V atom is six-coordinate in an octahedral geometry. The bond lengths related to the donor atoms in the complex are different from those in the ligand. The coordination of the ligand to V is also supported by IR spectra.     

Preparation and characterization of templated porous carbons from sucrose by one-pot method and application as a CO2 adsorbent

The templated porous carbons were prepared from sucrose by one-pot method. In this method in which the pre-synthesis of the hard template is eliminated, the porous carbons were produced by organic-inorganic self-assembly of sucrose, tetraethyl ortosilicate (TEOS), Pluronic P123 and n-butanol in an acidic medium, and subsequent carbonization. The synthesis parameters such as sucrose amount, TEOS molar ratio and carbonization temperature were evaluated for describing their effects on the pore structures of the synthesized carbons. The prepared porous carbons were characterized by N₂ adsorption, thermogravimetric analysis (TGA), Raman spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) techniques. The carbon dioxide adsorption uptakes of the obtained porous carbons were determined at 1 bar and 273 K. The templated carbon obtained with the lowest TEOS molar ratio exhibited the highest BET surface area of 1289 m²/g and micropore volume of 0.467 cm³/g, and showed the highest CO₂ uptake of 2.28 mmol/g.     

Sonochemical synthesis of hollow PbS nanospheres

PbS hollow nanospheres with diameters of 80-250 nm have been synthesized by a surfactant-assisted sonochemical route. The nanostructures were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), (high-resolution) transmission electron microscopy [(HR)TEM], and scanning electron microscopy (SEM) images. Structural characterization indicates that shells of the hollow spheres are composed of PbS nanoparticles with diameters of about 12 nm. The formation of the hollow nanostructure was explained by a vesicle-template mechanism, in which sonication and surfactant play important roles. Furthermore, uniform silica layers were successfully coated onto the hollow spheres via a modified St?ber method to enhance their performance for promising applications.     

Synthesis and crystal structure of Ni(II) complexes of 2′-(3,5-dibromo-2-hydroxybenzylidene)-3,5-dihydroxybenzoylhydrazide

A new mononuclear nickel(II) complex incorporating a Schiff-base ligand, [NiL₂](DMF)₄ (HL = 2′-(3,5-dibromo-2-hydroxybenzylidene)-3,5-dihydroxybenzoylhydrazide), has been synthesized and characterized by IR, UV-Vis, elemental analysis and X-ray crystal structure analysis. HL is an anionic tridentate ligand. The nickel atom is hexacoordinated with two oxygen atoms from keto group and two oxygen atoms from hydroxy group and two nitrogen atoms from amide, with the two nitrogen atoms occupying the axial positions forming a distorted octahedral coordination sphere.