Microwave‐associate synthesis of Co3O4 nanoparticles as an effcient nanocatalyst for the synthesis of arylidene barbituric and Meldrum's acid derivatives in green media

In this study, Co₃O₄ nanocatalysts were constructed in environmentally appropriate conditions using controlled, effective, and facile microwave method. The final nanostructures were characterized by SEM, XRD, and TEM analyses. The products had a small size distribution, homogeneous morphology, and crystallographic structures associated with the formation of Co₃O₄ nanostructures. Moreover, EDS mapping analysis confirmed the existence of Co and O elements in the final structure, and the magnetic properties of the samples were investigated by VSM. The application of this nanostructure in a catalytic process was further examined, and the results suggested that it could be used as a novel candidate for the synthesis of arylidene barbituric and Meldrum^,s acid through Knoevenagel condensation of aldehydes by barbituric and Meldrum^,s acid in aqueous media. The high yield of these nanocatalysts would be justified by the nature of the nanostructure as well as the experimental procedure developed in this study, which affected the physicochemical features of the products.     

Synthesis of Fluorinated Polyurethane/Polyacrylate Hybrid Emulsion Initiated by 60Co γ-Ray and Properties of the Latex Film

Based on the solvent-free method, novel fluorinated polyurethane/polyacrylate hybrid emulsions, dodecafluoroheptyl methacrylate (DFMA) as fluorinated monomer, were successfully prepared via emulsion polymerization without traditional emulsifier. For the purpose of increasing the grafting ratio of polyurethane and polyacrylate, ⁶⁰Co γ-ray radiation polymerization had been adopted to enhance the hardness of latex film. The chain structure and polymerization progress were confirmed by the analysis of Fourier transform infrared spectroscopy. The grafting ratio of polymethyl methacrylate and polyurethane was obtained by calculating the ratio of N–H peak integral area and Ph(C=C) peak integral area. The effect of DFMA content on thermal stability, mechanical property and water resistance were investigated systematically by thermal weight loss analysis, tensile strength test, absorbed water ratio and water contact angle.     

基于偶氮联吡啶配体的银和钴配位聚合物的构筑与性质

通过将2个4,4''-联吡啶基团用偶氮基团连接,我们合成了新的配体顺式-和反式-1,2-二（（4,4''-联吡啶）-3-氮烯）（cis-L和trans-L）,并利用trans-L与银离子和钴离子构筑了配位聚合物{[Ag₂（trans-L）（ClO₄）₂]·4CH₃CN}_n（1）和{[Co（trans-L）₂（H₂O）₂]（ClO₄）₂}_n（2）。其中1为一维梯形链,链与链之间通过π-π以及Ag…Ag相互作用堆积;2为三维无限dendrimer结构,其Co中心具有合适的氧化还原电位,在以荧光素为光敏剂的条件下,可作为光催化剂实现光解水放氢。     

还原氧化石墨烯/碳纳米管/Co_3O_4三元复合材料的制备与电化学性能

将低温水热反应和低温热处理相结合,制备了含还原氧化石墨烯(RGO)、碳纳米管(CNTs)和Co3O4的三元纳米复合材料RGO-CNTs-Co3O4;利用X射线衍射仪、扫描电子显微镜、透射电子显微镜分析了合成产物的相组成和微观结构,分析了其形成过程;并利用电化学测试装置测定了其作为锂离子电池负极材料的电化学性能.结果表明,在合成反应过程中,氧化石墨烯被还原剂肼还原为石墨烯,同时在石墨烯和CNTs表面生成氢氧化钴;再经低温热处理得到RGO-CNTs-Co3O4三元复合材料.Co3O4纳米颗粒均匀分散在由RGO片层和CNTs组成的三维网络结构中;这种三维网络结构既有利于电子和离子的传输,又能够有效抑制Co3O4在脱嵌锂过程中因体积变化引起的结构破坏.总体而言,合成的新型三元复合材料具有高的比容量以及良好的循环性能与倍率性能.     

Synthesis and Magnetic Properties of Pt3Co/Fe3O4 Nanocomposites

Bimagnetic Pt₃Co/Fe₃O₄ nanocomposite is synthesized in aqueous solution. The nanoparticles are characterized with TEM, FTIR, and magnetic measurements. The as‐synthesized nanocomposite exhibits ferromagnetic properties at room temperature due to the exchange coupling between Pt₃Co and Fe₃O₄. Magnetic properties of Pt₃Co/Fe₃O₄ nanoparticle can be tuned by varying of the molar ratio of iron to platinum. Pt₃Co/Fe₃O₄ nanoparticles exhibit higher saturation magnetization when the molar ratio of iron to platinum is 1.     

LiCoO2 Hollow Nanofibers by Co‐Electrospinning Sol‐Gel Precursor

LiCoO₂ xerogel hollow nanofibers were first prepared by co‐electrospinning the sol precursor, and the polycrystalline LiCoO₂ hollow nanofibers were obtained after calcination of the xerogel fibers. The obtained hollow nanofibers made up of 20～30 nm nanocrystals were about 100 nm to several micrometers in outer diameter. The hollow nanofibers were detected by means of SEM, TEM, TG, DSC, FTIR, and XRD techniques.     

Transition Metal Complexes of a Salen–Fullerene Diad: Redox and Catalytically Active Nanostructures for Delivery of Metals in Nanotubes

A covalently‐linked salen–C₆₀ (H₂L) assembly binds a range of transition metal cations in close proximity to the fullerene cage to give complexes [M(L)] (M=Mn, Co, Ni, Cu, Zn, Pd), [MCl(L)] (M=Cr, Fe) and [V(O)L]. Attaching salen covalently to the C₆₀ cage only marginally slows down metal binding at the salen functionality compared to metal binding to free salen. Coordination of metal cations to salen–C₆₀ introduces to these fullerene derivatives strong absorption bands across the visible spectrum from 400 to 630 nm, the optical features of which are controlled by the nature of the transition metal. The redox properties of the metal–salen–C₆₀ complexes are determined both by the fullerene and by the nature of the transition metal, enabling the generation of a wide range of fullerene‐containing charged species, some of which possess two or more unpaired electrons. The presence of the fullerene cage enhances the affinity of these complexes for carbon nanostructures, such as single‐, double‐ and multiwalled carbon nanotubes and graphitised carbon nanofibres, without detrimental effects on the catalytic activity of the metal centre, as demonstrated in styrene oxidation catalysed by [Cu(L)]. This approach shows promise for applications of salen–C₆₀ complexes in heterogeneous catalysis.     

Pentafluorobenzoato‐dimolybdenum(II) Solvate and Co‐crystal Complexes with Benzene and Naphthalin

The quadruply bonded Mo₂⁴⁺ complex Mo₂(DAniF)₃(OOCC₆F₅) ( 1 ) [DAniF = N,N′‐bis(4‐methoxyphenyl)formamidinate] was synthesized. The solvate Mo₂(DAniF)₃(OOCC₆F₅) · (C₆H₆) ( 2 ) and co‐crystal Mo₂(DAniF)₃(OOCC₆F₅) · (C₁₀H₈) ( 3 ) complexes were obtained by self‐assembly of crystals of 1 with benzene and naphthalin, respectively. Compounds 1 , 2 , and 3 were structurally characterized by single‐crystal X‐ray diffraction. In monomer 1 , the Mo–Mo bond length of 2.0874(6) Å is typical for dimolybdenum quadruple bonds. The solvate complex 2 was stabilized by weak π–π stacking interactions between the benzene molecule and the pentafluorophenyl ring (as indicated by a center‐to‐center distance of 3.838(10) Å and a center‐to‐plane distance of 3.712(4) Å between phenyl and pentafluorophenyl ring) and intermolecular C–H ··· F–C interactions (the shortest F ··· H distance is 2.560(2) Å). In complex 3 , a one‐dimensional chain was formed by C–H ··· F–C interactions between the hydrogen atoms in naphthalin and the fluorine atoms in the monomer (H ··· F distances of 2.582(2) Å). Information on the structures in solution of the three crystals was obtained by ¹H NMR spectroscopy.     

吸电子和亲水性Co-卟啉促进电催化氧还原反应的研究

研究影响电催化氧还原反应活性的因素对于合理设计高效的氧还原反应催化剂至关重要。调节催化剂电子结构通常被用于精确调控电催化氧还原反应活性。然而, 该反应发生在液/气/固界面, 很少有报道调控分子催化剂的亲疏水性来提高其催化活性。在此, 我们报道了两种钴卟啉NO₂-CoP（5,10,15,20-四（4-硝基苯基）钴卟啉）和5F-CoP（5,10,15,20-四（五氟苯基）钴卟啉）并研究了其电催化氧还原反应性能。通过同时调控meso-位取代基的电子结构和亲水性能, NO₂-CoP显示出比5F-CoP更高的电催化氧还原反应活性, 其半波电位向阳极方向移动近60 mV。NO₂-CoP比5F-CoP具有更好的亲水性。理论计算表明, NO₂-CoP比5F-CoP更容易有效地与O₂分子结合形成Co^III-O₂^·-。这项工作提供了一个简单而有效的策略, 通过使用吸电子和亲水取代基来提高钴卟啉的氧还原反应活性。该策略对于设计和开发其他用于电催化的分子催化剂体系也具有重要的启发意义。     

A Highly Sensitive and Selective Non-enzymatic Hydrogen Peroxide Sensor Based on Nanostructured Co3O4 Thin Films Using the Sol-gel Method

In this work we report an easy and efficient way to fabricate nanostructured cobalt oxide (Co₃O₄) thin films as a non-enzymatic sensor for H₂O₂ detection. Co₃O₄ thin films were grown on ITO glass substrates via the sol-gel method and characterized with several techniques including X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and optical absorbance. The Co₃O₄ thin films’ performance regarding hydrogen peroxide detection was studied in a 0.1 M NaOH solution using two techniques, cyclic voltammetry (CV) and amperometry. The films exhibited a high sensitivity of 1450 μA.mM⁻¹.cm⁻², a wide linear range from 0.05 μM to 1.1 mM, and a very low detection limit of 18 nM. Likewise, the Co₃O₄ thin films produced showed an exceptional stability and a high selectivity.