Synthesis,Characterization And Magnetic Properties Of Iron Selenide-Amine Hybrid Nanomaterials

Superconducting β-FeSe nanoplates,((3-Fe3Se4)4[Fe(teta)1.5](teta=triethylenetetramine)hybrid nanoplates,(Fe2.5Se4)2[Fe(en)2](en=ethylenediamiane)hybrid nanobelts and Fe3_xSe4(dien)2(dien=diethylenetriamine)hybrid nanoparticles are synthesized by a chemical solutions method with soluble iron and selenium salts as the precursors.Their growth mechanism,phase composition,structural and magnetic properties are systematically studied.Novel iron selenide-amine hybrid nanomaterials can be controllably constructed by building Fe-amine organic complexes and inorganic FeSe,fragments in chemical solution processes,which could not only enrich the hybrid material system,but also exhibit expectation in future multi-functional applications for their outstanding magnetic properties.Single crystal β-FexSe superconducting nanosheets are synthesized by low temperature solvothermal method using soluble ferrous sulfate and selenium powder as the precursors.The growth of β-Fe,Se nanosheets are dominated by a Se diffusion mechanism.Precise tuning the stoichiometry in β-Fe,Se gives rise to a controllable transition of AFM-SC-AFM order.Depending on the ratio of Fe/Se,the superconducting transition temperature of β-FexSe nanosheets increases from 3.2 K to 10 K.With the highest magnetic field up to 14 T at 2 K,the superconducting transition is still observed,indicating the upper critical magnetic field of theas-prepared β-FeSe is higher than 14 T.Resistance measurements of a singleβ-FeSe nanoplate show that no superconducting transition was found in the range of 2-300 K,due to oxidation in the air during the micro-nanofabrication of the test device.(β-Fe3Se4)4[Fe(teta)1.5]hybrid nanoplates with room temperature ferrimagnetism are synthesized by organic solvent liquid phase method.Tetragonal crystal structure and the space group of 14cm(108)are determined by selected area electron diffraction and X-ray diffraction methods.(β-Fe3Se4)4[Fe(teta)1.5]is self-assemblyed by β-Fe3Se4 superstructure and Fe(teta)1.5 complex.The room-temperature and low-temperature hysteresis loops show that the(β-Fe3Se4)4[Fe(teta)1.5]hybrid nanoplates are ferrimagnetic.The thermal magnetic curve of the(β-Fe3Se4)4[Fe(teta)1.5]nanoplates between 5 and 900 K reveal the Curie temperature(Tc)higher than 530 K.The growth process of the hybrid nanoplates is related to reaction temperature.By increasing the reaction temperature from 433 K to 523 K,the size of the hybrid nanostructures can be tuned from 100 nm to 4 μm,and their shapes vary from nanoparticles and nanobelts to nanoplates,which are attributed to the increase of iron in the inorganic buliding units of hybrid materials.In the case of hybrid nanoplates synthesized at 483 K,a giant coercivity value reaching 11 kOe is obtained at 5 K,exhibiting excellent hard magnetic properties.Ferrimagnetic(Fe2.5Se4)2[Fe(en)2]can not be synthesized directly by a solvothermal method.Here,(Fe2.5Se4)2[Fe(en)2]nanobelts have been synthesized by converting(β-Fe3Se4)4[Fe(teta)1.5]hybrid nanoplates under a facile amine-exchange strategy.The cell parameters of orthorhombic(β-Fe3Se4)4[Fe(teta)1.5]are a=21.405 A,b=10.506 A,c=7.721 A,with the space group of Pcca(54).Magnetic measurements demonstrate strong ferrimagnetic interactions below 220 K in the(Fe2.5Se4)2[Fe(en)2]nanobelts.The transformation mechanism from(p-Fe3Se4)4[Fe(teta)1.5]precursor to(Fe2.5Se4)2[Fe(en)2]hybrid nanobelts was studied by controlling the reaction time.Fe3-xSe4(dien)2 hybrid nanostructures with room-temperature ferrimagnetism have been synthesized by a one-pot high-temperature organic-solution-phase method.Fe3-xSe4(dien)2 has regular hexahedron morphology with a length,width and height of 700,600 and 400 nm,respectively.Its crystal structure is orthogonal and belongs to C2221 space group.The cell parameters are a=9.23 A,b=18.01 A,c=11.61 A,respectively.Magnetic measurements reveal the Tc of Fe3-xSe4(dien)2 nano hexahedrons is higher than 470 K.Growth mechanism study shows that the morphology of Fe3-xSe4(dien)nanostructures can be engineered by adjusting the stoichiometric ratio of Fe and Se.With increasing the reaction time from 3 h to 8 h and 20 h,Fe atoms gradually diffuse into the hybrid nanoparticles,resulting in the formation of Fe2.93Se4(dien)2 hybrid hexahedrons,Fe3.19Se4(dien)2 hybrid nanobelts and Fe3.46Se4(dien)2 hybrid nanoplates.The excellent ferrimagnetic properties of Fe2.93Se4(dien)2 may be attributed to the unique combination of inorganic β-Fe1-xSe2 fragments and Fe(dien)2 complexes.