Composés isomorphes MeX2O4: Dilatation thermique anisotrope et ordre magnétique dans MnSb2O4

Using X-ray diffraction data, the anisotropic thermal expansion coefficients α_a and α_c of two isomorphic compounds MnSb₂O₄ and NiSb₂O₄ are linked to the anisotropic elastic constants of these tetragonal structures and compared to the ZnSb₂O₄, SnPb₂O₄ thermal expansion coefficients. The anomalous thermal expansion observed for MnSb₂O₄ in the 6–115 K range (maximum of α_c at 70 K) is related to the ordering of Mn²⁺ ion magnetic moments. Using neutron diffraction, two kinds of antiferromagnetic order are observed for MnSb₂O₄ and NiSb₂O₄. At 6 K the value of the resultant moment is approximately 1.8 μ_B for NiSb₂O₄ and 3.8 μ_B for MnSb₂O₄. A critical temperature of T_c = 115 K is proposed for MnSb₂O₄ based on the use of X-ray diffraction data alone.     

Synthesis and crystal structures of the manganous antimonates Mn2Sb2O7 and MnSb2O6

Mn₂Sb₂O₇ has been prepared by the solid state reaction of MnCO₃ and Sb₂O₃ at 1100°C, and its crystal structure determined from X-ray powder diffraction data. The compound is trigonal P3₁21 with a = 7.191, c = 17.398 Å, and the structure is fluorite-related, but not a distorted pyrochlore. The relationship between this structure and that of pyrochlore is discussed. MnSb₂O₆ was formed as a reaction intermediate and its structure has also been determined. This phase is trigonal P321 with a structure related to that of Na₂SiF₆ and is apparently a new polymorph, since MnSb₂O₆ has previously been stated to have either the orthorhombic columbite or the tetragonal trirutile structure.     

Facile and eco-benign synthesis of a novel MnFe2O4@SiO2@Au magnetic nanocomposite with antibacterial properties and enhanced photocatalytic activity under UV and visible-light irradiations

The purpose of this research is to prepare novel, inexpensive, eco-friendly and efficient magnetic nanocomposites for degradation of pollutant from wastewater and their potential antibacterial activity. To reach this goal, we have synthesized magnetic MnFe₂O₄@SiO₂@Au (MnFe@Si@Au) nanocomposites through ultrasound assisted co-precipitation technique in presence of carbohydrate and Crataegus fruits extract, for the first time. The influence of capping agents including sucrose, glucose, PVA and reducing agents such as C. microphylla and C. pentagyna on the morphology, size, purity, photocatalytic and antibacterial behavior of magnetic nanocomposites were investigated. The FT-IR, XRD, VSM, EDS, FE-SEM, TEM and BET analysis were performed to confirm the formation of magnetic nanocomposites. MnFe@Si@Au nanocomposites have shown promising potential in degradation of organic contaminants including rhodamine b (RhB), 2-naphthol (2-NPH), methyl violet (MV), erythrosine (ER) and eriochrome black T (EBT) under both radiation conditions. The results show that degradation of the anionic contaminants is more than cationic contaminants under UV and visible irradiations. As well as, these synthesized spherical MnFe@Si@Au nanocomposites show excellent antibacterial activities against P. aeruginosa, K. pneumoniae and P. mirabilis bacteria. In addition to the features mentioned, another prominent feature of this nanocatalyst is retaining their photocatalytic activity after five cycles of utilization.     

Tin-derivative sandwich-type polyoxometalates supported on Nd-doped TiO2 nanoparticles as efficient and reusable catalysts in the oxidation of sulfides and alcohols

New nanocomposites, including different loading levels of sandwich-type polyoxometalates [(HOSn^IVOH)₃(XW₉O₃₄)₂]^n? (X = As (1), P (2) n = 12 and Si (3) n = 14) on Nd-doped TiO₂ nanoparticles were prepared by a simple impregnation method. The nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, Fourier transform infrared (FTIR), and energy-dispersive X-ray spectroscopy. Compounds 1–3 were successfully loaded on Nd-doped crystallized anatase-phase TiO₂ nanoparticles of 20–25 nm. Catalytic activities of nanocomposites were examined by carrying out the oxidation of sulfides and alcohols with H₂O₂. Simple synthesis method, reusability, and low amounts of the heterogeneous catalysts with a slight excess of H₂O₂ and mild reaction conditions make these oxidation reactions an environmentally benign chemical process.     

PEGylation of chitosan for improved solubility and fiber formation via electrospinning

PEG-N-chitosan and PEG-N,O-chitosan were synthesized via reductive amination and acylation of chitosan, respectively. The structures were confirmed by FTIR and H¹NMR. The extents of PEGylation increased with reducing chain lengths of either chitosan (M _v = 137–400 kDa) or poly(ethyelene glycol) (PEG, M _n = 500–2 kDa). Water solubility were easily achieved at degree of substitution (DS) as low as 0.2 for either derivtive whereas the PEG-N,O-chitosan at DS = 1.5 was soluble in organic solvents, including CHCl₃, DMF, DMSO and THF. None of the aqueous solutions of PEG-N-chitosan or PEG-N,O-chitosan alone could be electrospun into fibers. Electrospinning of PEG550-N,O-chitosan145 at 25% in DMF produced fibrous structure intermixed with beads. The efficiency of fiber formation and the uniformity of fibers were improved by increasing the solution viscosity using a cosolvent or reducing the solution surface tensions with a non-ionic surfactant. Ultra-fine fibers with diameters ranging from 40 nm to 360 nm and an average diameter of 162 nm were efficiently generated from electrospinning of 15% PEG550-N,O-chitosan145 in 75/25 (v/v) THF/DMF cosolvents with 0.5% Triton X-100^TM.     

Les antimonites antiferromagnetiques MnSb2O4 et NiSb2O4

Neutron diffraction has been used to study the variation of antiferromagnetic order in the antimony isomorphous MnSb₂O₄ (T_N ～ 60 K) and NiSb₂O₄ (T_N ～ 46 K). The magnetic moments have been related to the Mn²⁺ and Ni²⁺ spins and magnetostrictive effects have been interpreted. The influence of the method of synthesis is mentioned: polycrystalline MnSb₂O₄ has been obtained from hydrothermal synthesis. Orthorhombic distortions are not connected with magnetic interactions but with structural defects.     

Comparison of photocatalytic and antibacterial activities of allotropes of graphene doped Sm2O3 nanocomposites: Optical,thermal, and structural studies

This study mainly focuses on the synthesis of two allotropes of graphene, graphene oxide (GO) and reduced graphene oxide (rGO), by the modified Hummers' method and chemical reduction method, respectively. Sm₂O₃/GO and Sm₂O₃/rGO nanocomposites were further synthesized in the presence of the cationic surfactant CTAB via the sol–gel method followed by the reflux method. Synthesized nanocomposites were subjected to characterization by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and UV–Visible spectroscopy to explore structural, thermal, optical, and photocatalytic properties. Characteristic FTIR peaks were observed in nanocomposites, and the bond length of the Sm-O bond was calculated. The Coats-Redfern method was employed to calculate the kinetics and thermodynamic parameters. Hexagonal crystallite shapes of Sm₂O₃/GO and Sm₂O₃/rGO nanocomposites with 11.8 and 13.13 nm crystallite sizes and 3.9 and 2.5 eV optical band gaps were observed. The photocatalytic efficiency of Sm₂O₃/GO and Sm₂O₃/rGO nanocomposites was assessed against the degradation of methylene blue in the presence of sunlight, and its degradation was confirmed through FTIR. The antimicrobial activities were also performed against the bacterial strains Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus.     

Facile preparation of Nd_2Zr_2O_7–ZrO_2 nanocomposites as an effective photocatalyst via a new route

Nd_2Zr_2O_7–ZrO_2 nanocomposites were prepared via a facile process with propylene glycol as novel connecting agent and benzene tricarboxylic acid as a new complexing agent. The as-obtained Nd_2Zr_2O_7–ZrO_2 nanocomposites were characterized by transmission electron microscopy(TEM), UV–vis diffuse reflectance spectroscopy, energy dispersive X-ray microanalysis(EDX), Fourier transform infrared(FT-IR)spectroscopy, field emission scanning electron microscopy(FESEM), and X-ray diffraction(XRD). According to the morphological studies of the as-synthesized nanocomposites, it was found that the shape and particle size of Nd_2Zr_2O_7–ZrO_2 nanocomposites depended on the space-filling template type, dosage of space-filling template and tricarboxylic acid as complexing agent. Nd_2Zr_2O_7–ZrO_2 nanocomposites with different shapes and grain sizes have been synthesized. The photocatalytic behavior of as-produced Nd_2Zr_2O_7–ZrO_2 nanocomposites was also investigated through photodegradation of methylene blue dye and 2-naphthol as water pollutants.     

Polypyrrole/γ-Fe2O3 magnetic nanocomposites synthesized in supercritical fluid

Polypyrrole/iron oxide (PPy/γ-Fe₂O₃) nanocomposites were synthesized by in situ oxidative polymerization of pyrrole in the presence of surface modified γ-Fe₂O₃ in supercritical carbon dioxide (scCO₂). The structural properties of nanocomposite particles thus obtained were characterized by FT-IR, thermal analysis (TGA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). It was found that ca. 50 nm γ-Fe₂O₃ nanoparticles were well dispersed in PPy powder in TEM pictures. X-ray photoelectron spectroscopy (XPS) analysis also support that all γ-Fe₂O₃ nanoparticles are encapsulated by PPy. Magnetic property of the nanocomposites was measured by SQUID, which indicated that the nanocomposites are superparamagnetic. The effects of different loadings of γ-Fe2O3 on the polymerization were also investigated.     

Preparation of CoFe2O4/sawdust and NiFe2O4/sawdust magnetic nanocomposites for removal of oil from the water surface

In this study, CoFe₂O₄/Sawdust and NiFe₂O₄/Sawdust magnetic nanocomposites were synthesized using a hydrothermal method, and then characterized using X-ray powder diffraction, Infrared, scanning electron microscopy, Brunauer–Emmett–Teller/Barrett–Joyner–Halenda, and vibrating-sample magnetometer techniques. In this study, unmodified sawdust (US), modified sawdust (MS), unmodified CoFe₂O₄/sawdust (UCS), modified CoFe₂O₄/sawdust (MCS), unmodified NiFe₂O₄/sawdust (UNS), and modified NiFe₂O₄/Sawdust (MNS) magnetic nanocomposites, which are inexpensive, economical, environmentally friendly absorbents, and have a high selective hydrophobic, were used for the removal of oil from the water surface. The results show that the UCS, MCS, UNS, and MNS magnetic nanocomposites can selectively absorb the oil spreading on the water surface, due to its superhydrophobicity and superoleophilicity, and can be easily collected from water under the influence of a magnetic field. In addition, the results showed that the absorbents reach their equilibrium at the 30-min mark. Among all the absorbents, the MNS magnetic nanocomposite showed the maximum absorption capacity (18.172 g/g) at the 40-min mark. The results of the kinetic studies showed that the second-order kinetic equation with the highest correlation coefficient had the best fit with the experimental results.     

One-pot synthesis of 2H-indazolo[2,1-b]phthalazine-triones via nano γ-Al2O3/BF3/Fe3O4 as an efficient catalyst and theoretical DFT study on them

Experimental and computational studies were carried out for the synthesis of 2H-indazolo[2,1-b]phthalazine-triones using γ-Al₂O₃/BF₃/Fe₃O₄ as a nanocatalyst in optimized and solvent-free conditions. The most significant features of the existing protocol are easy preparation of the catalyst, short reaction times, environmentally benign, and milder reaction conditions. The analysis data were reported using the experimental results of this investigation, such as: H-NMR, FT-IR (Fourier-transform infrared spectroscopy), X-ray diffraction, vibrating-sample magnetometer, Thermal gravimetric analysis (TG-DTG), nitrogen adsorption isotherm, Field Emission Scanning Electron Microscopy, and Transmission electron microscopy images of nanocatalyst. In this study, 2H-indazolo[2,1-b]phthalazine-triones have also been theoretically investigated using DFT-B3LYP/6-31G method. Also, some of the physical chemistry properties have examined for conformers of products, which there was good agreement between the computational results and obtained experimental for the products.     

Synergistic Effect Between Sb2O3 Nanoparticles–Trichloromelamine and Carbon Nanotube on the Flame Retardancy and Thermal Stability of the Cellulose Acetate

Sb₂O₃ nanoparticles were synthesized via a simple surfactant-free sonochemical reaction. Multi-walled carbon nanotubes (MWCNT) have been successfully functionalized with amino groups. Cellulose acetate (CA) as a polymeric matrix was choosing in this work. In order to improve the thermal stability and flame retardancy of the CA, nanoparticles, aminated-MWCNT and trichloromelamine (TCM) were added to the polymeric matrix. The nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy and UL-94 analysis. Flame retardancy of the nanocomposite was improved as a result of synergistic effect between Sb₂O₃ and TCM. Result show that thermal decomposition of the nanocomposites was shifted towards higher temperatures.     

Graphene anchored with ZnFe2O4 nanoparticles as a high-capacity anode material for lithium-ion batteries

Heterostructured ZnFe₂O₄–graphene nanocomposites are synthesized by a facile hydrothermal method. The as-prepared ZnFe₂O₄–graphene nanocomposites are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) analysis and galvanostatic charge and discharge measurements. Compared with the pure ZnFe₂O₄ nanoparticles, the ZnFe₂O₄–graphene nanocomposites exhibit much larger reversible capacity up to 980 mAh g⁻¹, greatly improved cycling stability, and excellent rate capability. The superior electrochemical performance of the ZnFe₂O₄–graphene nanocomposites could be attributed to the synergetic effect between the conducting graphene nanosheets and the ZnFe₂O₄ nanoparticles.     

SbxZn1-xO1+x/2及其壳聚糖复配物的制备和抗菌性能

采用溶胶-凝胶法制备了SbxZn1-xO1+x/2及其壳聚糖的复配物,通过X-射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等表征了样品的物相结构、组成和微观形貌。以大肠杆菌、白色念珠菌和金黄色葡萄球菌为测试菌种,研究了样品的抗菌性能。结果表明,SbxZn1-xO1+x/2的抗菌活性优于纯ZnO,其中x=0.05的样品活性最好;复配物的抗菌活性明显优于单一组分,当Sb0.05Zn0.95O1.025和壳聚糖质量比mSZ/mCS=2时,样品抗菌性能最佳。     

Ni@NiO核-壳纳米球的合成及其电化学生物传感应用研究

利用无模板水热法合成了镍纳米球,并通过部分氧化制备了Ni@NiO核壳结构的纳米复合物。合成的镍球和Ni@NiO复合物的尺寸可以通过简单调节反应条件来控制。运用XRD、EDS、TEM和SEM等测试方法对合成样品的形貌和组成进行了表征。Ni和Ni@NiO复合材料均有较好的磁性,其磁性用磁滞回线进行了表征。此外,Ni@NiO纳米复合物可以和血红蛋白结合构建过氧化氢生物传感器,该生物传感器对过氧化氢表现出很好的生物电催化活性,且具有较低的检测限和较宽的线性响应范围。该复合材料对于血红蛋白催化还原过氧化氢具有米氏响应和较小的米氏常数,表明Ni@NiO能较好地保持血红蛋白原有的活性。     

Bacitracin‐Conjugated Superparamagnetic Iron Oxide Nanoparticles: Synthesis,Characterization and Antibacterial Activity

Bacitracin‐conjugated superparamagnetic iron oxide (Fe₃O₄) nanoparticles were prepared by click chemistry and their antibacterial activity was investigated. After functionalization with hydrophilic and biocompatible poly(acrylic acid), water‐soluble Fe₃O₄ nanoparticles were obtained. Propargylated Fe₃O₄ nanoparticles were then synthesized by carbodiimide reaction of propargylamine with the carboxyl groups on the surface of the iron oxide nanoparticles. By further reaction with N₃‐bacitracin in a Cu^I‐catalyzed azide–alkyne cycloaddition, the magnetic Fe₃O₄ nanoparticles were modified with the peptide bacitracin. The functionalized magnetic nanoparticles were characterized by powder X‐ray diffraction, X‐ray photoelectron spectroscopy, TEM, zeta‐potential analysis, FTIR spectroscopy and vibrating‐sample magnetometry. Cell cytotoxicity tests indicate that bacitracin‐conjugated Fe₃O₄ nanoparticles show very low cytotoxicity to human fibroblast cells, even at relatively high concentrations. In view of the antibacterial activity of bacitracin, the biofunctionalized Fe₃O₄ nanoparticles exhibit an antibacterial effect against both Gram‐positive and Gram‐negative organisms, which is even higher than that of bacitracin itself. The enhanced antibacterial activity of the magnetic nanocomposites allows the dosage and the side effects of the antibiotic to be reduced. Due to the antibacterial effect and magnetism, the bacitracin‐functionalized magnetic nanoparticles have potential application in magnetic‐targeting biomedical applications.     

Spectral,morphological, and antibacterial studies of conducting copolymers,Ppy‐MA,and their nanocomposites,Ag@Ppy‐MA

Pyrrole and methyl anthranilate were copolymerized in different molar ratios in the presence of, H₂O₂, and FeSO₄ at ambient temperature and pressure to obtain efficient conducting copolymers, Ppy‐MA. These conducting copolymers, Ppy‐MA, were in situ reacted with silver nanoparticles to generate nanocomposites, Ag@Ppy‐MA, which exhibit enhanced electrical conductivity. The spectra and morphology of different copolymers, Ppy‐MA, and their nanocomposites, Ag@Ppy‐MA, were analyzed using Fourier transform infrared, SEM, tunneling electron microscopy, X‐ray diffraction, thermogravimetric analysis, and differential thermal analysis. These studies have shown that the nanocomposites, Ag@Ppy‐MA, are thermally more stable and good electrical conductors as compared with their copolymers, Ppy‐MA. The antibacterial activity of the copolymers, Ppy‐MA, prepared from different monomer ratios and their nanocomposites, Ag@Ppy‐MA, has been carried out using disk diffusion method. The copolymers, Ppy‐MA, and its nanocomposites, Ag@Ppy‐MA, were screened against the standard drug Ciprofloxacin. The results clearly suggest that the nanocomposites, Ag@Ppy‐MA, are better antibacterial agent as compared with their copolymers, Ppy‐MA. Copyright © 2016 John Wiley & Sons, Ltd.     

2D ZnO/Fe3O4 nanocomposites as a novel catalyst-promoted green synthesis of novel quinazoline phosphonate derivatives

In this research a novel and efficient procedure for the preparation of phosphonate derivatives using the reaction of 2,4-dihydroxyacetophenone, isopropenylacetylene, 2-amino-N-alkyl benzamide, dialkyl acetylenedicarboxylates and trimethyl phosphite or triphenyl phosphite in the presence of reusable 2D ZnO/Fe₃O₄ nanocomposites in water at room temperature was investigated. The 2D ZnO/Fe₃O₄ nanocomposites were synthesized using ionic liquid [OMIM]Br as a stabilizer and soft template. In addition, the power of antioxidant for some prepared compounds was studied using trapping of radicals by DPPH and a ferric reduction activity potential experiment. As a result, compound 6f displayed a noteworthy power for trapping of free radicals and 6b exhibited excellent reducing power compared with standards (BHT and TBHQ). Moreover, the antimicrobial power of some prepared quinazolinone phosphonates was proved by employing the disk diffusion experiment on two kinds of bacteria, Gram-positive and -negative bacteria. The obtained outcomes of disk diffusion test showed that these compounds prevented bacterial growth. Some advantages of this procedure are: short time of reaction, high yields of product and easy separation of catalyst and products.     

A Novel Approach for Generation of Oxygen Vacancies in Trirutile MnSb2O6 and Their Impact on Photocatalytic Degradation of MO Dye

Visible light-driven photocatalysis has gained much attention due to its light-harnessing characteristics and is extensively used in wastewater remediation. This paper presents a novel oxygen-deficient manganese antimonate, MnSb₂O_6-x, with a trirutile structure as an effective visible-light-driven photocatalyst for dye degradation. The synthesized samples were subjected to XRD, UV-Vis DRS, SEM-EDS, Raman, XPS, and PL analyses to study their physic chemical properties. The influence of sequential or single heating during the preparation method on the generation of oxygen vacancies is evaluated using UV-Vis DRS, XPS, ESR, and Raman techniques. The oxygen-deficient MnSb₂O₆ could achieve up to 85 % of MO degradation in 180 min under visible light irradiation, and its reusability up to six cycles was also investigated. In addition, the mechanism of dye degradation was supported with a scavenger test, and the degradation activities are correlated to the electron-hole pair separation as convinced from the PL spectra. The simple and unique method of oxygen vacancy generation can inspire the development of antimonates with oxygen deficiencies, which have significant scope of application in environmental and energy conservation.     

Preparation and characterization of magnetic Co0.5Zn0.5Fe2O4-chitosan nanoparticles as surfactants in oilfield

Chitosan nanoparticles with magnetic properties can be potentially used as separation materials in adsorption of oil for enhanced oil recovery. Different from the traditional surfactants, the novel magnetic Co_0.5Zn_0.5Fe₂O₄-chitosan nanoparticles are of excellent biodegradation and a high level of controllability. The Co_0.5Zn_0.5Fe₂O₄-chitosan nanoparticles with core-shell structure were prepared successfully. The image of transmission electron microscope and the scanning electron microscopy showed that the cubic-shape magnetic Co_0.5Zn_0.5Fe₂O₄-particles were encapsulated by the spherical chitosan nanoparticles. The size of the Co_0.5Zn_0.5Fe₂O₄-chitosan nanoparticles was below 100 nm. The saturated magnetization of the Co_0.5Zn_0.5Fe₂O₄-chitosan nanoparticles could reach 80 emu g^?1 and showed the characteristics of superparamagnetism at the same time. The evaluation on the interfacial properties of the product demonstrated that the interfacial tension between crude oil and water could be reduce to ultra-low values (to about 10^?3 mN m^?1) when the magnetic Co_0.5Zn_0.5Fe₂O₄-chitosan nanoparticle was used in several blocks in Shengli Oilfield without other additives. Meanwhile, the magnetic Co_0.5Zn_0.5Fe₂O₄-chitosan nanoparticles possessed good salt-resisting capacity.