室温下快速合成超小Fe3+掺杂BiF3纳米粒子

室温下快速合成了Fe³⁺掺杂的BiF₃超小纳米粒子,只需要反应1 min,较小的Fe³⁺离子即可替代BiF₃晶格中较大的Bi³⁺离子.随着Fe³⁺掺杂量的增加,BiF₃：Fe³⁺纳米粒子的粒径不断减小,当Fe³⁺的掺杂量达到0.119时,可以得到尺寸约为6.9 nm的Fe³⁺掺杂BiF₃超小纳米粒子.此外,Fe³⁺离子的掺杂使BiF₃：Fe³⁺-x样品的能带结构发生了显著变化.制备的Fe³⁺掺杂BiF₃超小纳米粒子在光催化剂和荧光材料方面具有潜在的应用价值.     

CoFe2-xRExO4(RE=Tb,Dy)纳米晶薄膜的化学合成及磁性

以溶胶-凝胶法制备了稀土铽或镝掺杂的钴尖晶石铁氧体纳米晶薄膜.考察了Tb或Dy的掺杂量及晶化条件对晶相的影响.结果表明,稀土离子的掺杂量x超过0.3时,样品很难形成尖晶石单相.原子力显微镜对纳米晶薄膜表面形貌的观测显示,溶胶-凝胶法制备的薄膜粒度可控制在20～50nm,且具有较高的表面平整度.对于厚度为200nm的薄膜,均方根粗糙度仅为4～5nm.磁特性研究发现,掺杂Tb或Dy的样品矫顽力明显提高.     

深冷状态下纳米镝铁氧体磁粒子磁性能的研究

采用湿化学法制备出稀土Dy3+掺杂的纳米Fe3O4磁粒子,用月桂酸进行了表面修饰,研究了磁粒子在室温和深冷(200.2～56.5 K)状态下的磁性能.经X射线衍射分析发现,适量的Dy3+掺杂不会改变纳米Fe3O4磁粒子的晶型结构.透射电镜(TEM)照片表明,制备出的纳米磁粒子成球性好,且大部分磁粒子的粒径在14 nm左右.通过磁性测量仪、振动样品磁强计(VSM)对磁性能进行了表征.磁化曲线表明掺杂引起磁性能发生变化,磁粒子室温下无剩磁和矫顽力,具有超顺磁性;深冷状态下出现剩磁和矫顽力,且随温度的降低,剩磁和矫顽力增大,不具有超顺磁性,饱和磁化强度略高于室温值.     

羧甲基纤维素/Fe3O4复合纳米磁性材料的制备、表征及吸附性能的研究

采用改进的氧化沉淀法在羧甲基纤维素(CMC)体系中制备了以磁性纳米Fe₃O₄为核心, 外层包覆羧甲基纤维素的复合磁性纳米材料. 用透射电镜、X射线衍射、红外光谱、Zeta电位和震动样品磁强计对复合纳米Fe₃O₄进行了表面形貌、结构和磁学的表征. 在此基础上研究了复合纳米Fe₃O₄对Cu^2＋的吸附性能, 探讨了溶液pH、反应时间和 Cu^2＋的初始浓度对其吸附性能的影响. 实验结果表明, 复合Fe₃O₄粒子为反尖晶石型, 平均粒径在40 nm左右, 羧甲基纤维素在Fe₃O₄粒子表面是化学吸附, 复合Fe₃O₄粒子的饱和磁化强度为36.74 emu/g, 在中性溶液中Cu^2＋的吸附量最高, 吸附平衡时间为1.5 h, 二级动力学模型能够很好地拟合吸附动力学数据, 吸附等温数据符合Langmuir模型. 复合纳米Fe₃O₄对Cu^2＋的吸附机理主要为表面配位反应.     

Gd2ZnTiO6∶Dy3+, Eu3+单基质白光荧光粉的制备与发光性能

采用溶胶-凝胶法制备出Dy³⁺, Eu³⁺共掺杂Gd₂ZnTiO₆白光荧光粉. 通过X射线衍射(XRD)、 扫描电子显微镜(SEM)、 光致发光(PL)光谱对荧光粉的物相、 形貌及荧光性质进行了表征. 结果表明, 所制备的样品均为双钙钛矿结构, 属于单斜晶系(空间群: P2₁/n), 形貌为2~5 μm无规则形状的颗粒. 在392 nm近紫外光的激发下, Gd₂ZnTiO₆∶Dy³⁺,Eu³⁺荧光粉展现出Dy³⁺的蓝光、 黄光发射以及Eu³⁺的特征红光发射. 此外, 通过调节Dy³⁺和Eu³⁺的掺杂浓度, 可实现低色温的暖白光发射. 基于样品优异的荧光性能, 该荧光粉在近紫外激发白光LED中具有一定的开发潜力.     

TiO2纳米管电极金属离子掺杂的表征

采用浸渍法对TiO₂纳米管电极进行Zn²⁺、Fe³⁺、Cu²⁺离子的掺杂改性,并进行了各种性能表征.扫描电镜(SEM)及X射线衍射光谱(XRD)结果表明,金属离子掺杂后的TiO₂纳米管电极依然保持了良好的表面形态及锐钛矿晶型,纳米管的直径为60-100 nm,其晶面主要为101面;可见紫外漫反射光谱(DRS)分析表明,进行掺杂的TiO₂纳米管电极的光学性质有不同程度的改变,Zn²⁺、Fe³⁺和Cu²⁺掺杂的TiO₂纳米管电极的禁带宽度分别为3.37 eV3、.14 eV、2.86 eV.这表明掺Cu²⁺的TiO₂纳米管电极的吸收边带发生了明显的红移.     

基于能量传递可调光色荧光粉Ca2LaTaO6∶ Dy3+, Sm3+的发光性质及其发光二极管器件应用

通过固相反应法设计了Dy³⁺, Sm³⁺共掺杂双钙钛矿结构Ca₂LaTaO₆(CLTO)光色可调的白光发光二极管(LED)荧光粉. 通过Rietveld精修计算, 确定了Ca₂LaTaO₆的晶体结构参数和Dy³⁺, Sm³⁺离子的晶格占位, 并用密度泛函理论(DFT)计算了禁带宽度. 激发/发射光谱和荧光衰减行为证实了共掺杂体系中Dy³⁺到Sm³⁺的能量传递. Dy³⁺→Sm³⁺的能量传递机制为电偶极-电偶极相互作用, 离子间的临界距离为1.176 nm. 基于Dy³⁺→Sm³⁺的能量传递, 可通过调节Dy³⁺/Sm³⁺离子的掺杂浓度比, 使发光颜色从黄色转变为黄红色, 并实现白光发射. 利用该荧光粉与紫外芯片结合制作成白光发光二极管器件, 并确定了这些LED器件的发光效率、 CIE色度坐标、 相关色温(CCT)和显色指数(CRI)等. 结果表明, 这些荧光粉在紫外激发的白光LED中具有潜在的应用价值.     

水滑石型磁性纳米载药粒子的制备及其体外药物释放性能研究

通过调变镁铁尖晶石的含量, 采用一步共沉淀法制备了一系列具有核壳结构的水滑石型磁性纳米载药粒子, 对其微结构、热稳定性、磁性和药物释放性能进行了系统的研究. 结果表明这种磁性纳米载药粒子是一种具有以镁铁尖晶石为核层、双氯酚酸(Diclofenac, DIC)插层水滑石(DIC-LDH)为壳层的复合纳米粒子, 粒径在90～180 nm之间. 其中壳层DIC-LDH的晶粒尺寸D₁₁₀和层板电荷密度随磁核含量的增大而逐渐减小. 磁性纳米载药粒子的载药量随磁核含量的增大而逐渐减小, 而其比饱和磁化强度则随着磁核含量的增大逐渐增大. 体外释放实验表明, 无外加磁场时, 磁核含量增大, 壳层DIC-LDH粒径减小, 磁性纳米载药粒子药物释放速率逐渐增大|外加1500 G磁场时, 磁核含量增大, 磁致团聚程度增大, 其药物释放速率逐渐减小.     

供体-锯齿型碳纳米管-受体的非线性光学响应对管径的依赖性

用密度泛函 B3LYP 方法得到一系列不同管径的氨基-硝基双取代纳米管NH₂-(n,0)CNT-NO₂ (n＝5～10)的几何结构. 用CAM-B3LYP 方法计算了体系的第一超极化率(β₀). 研究表明, β₀ 对管径大小有着极强的依赖性. 特别是对偶数纳米管(n＝6, 8 和10), 其β₀ (5.5×10³～9.8×10⁴ au)是奇数纳米管β₀ (1.0×10³～2.8×10³ au)的5～35 倍.     

水热法制备掺杂铁离子的TiO2纳米粒子及其光催化反应研究

以TiCl⁴为前驱体,采用水热法制备了掺杂铁离子的TiO₂纳米粒子,利用XRD对不同条件下制备的产物进行了表征,探讨了反应温度、胶体溶液pH值和反应时间对水热反应的影响.考察了所制备的Fe³⁺-TiO₂纳米粒子光催化降解罗丹明B的催化性能,实验发现,制备的掺杂0.1%Fe³⁺-TiO₂纳米粒子与纯TiO₂相比,具有更好的催化活性.     

Synthesis and characterization of pure and Li2O doped ZnFe2O4 nanoparticles via glycine assisted route

Nanoparticles of zincl ferrite have been synthesized by the combustion method and the effect of lithia doping on their structural, morphological and magnetic properties have been studied in detail. The samples were characterized by IR, XRD, SEM, TEM and VEM. The powder XRD patterns confirm the single phase spinel structure for the synthesized materials. Transmission electron microscopy analysis revealed spherical Zn-ferrite particles with a narrow size distribution. 0.69 wt% Li₂O-doping results in a decrease of the magnetization and increase of coercivity of the nanoparticles. This observation implies that, besides size, doping causes also significant structural rearrangements which in turn induce changes in the strength and the number of Fe³⁺(A)–O–Fe³⁺(B) superexchange interactions.     

The impact of highly paramagnetic Gd3+ cations on structural,spectral, magnetic and dielectric properties of spinel nickel ferrite nanoparticles

In this work, fabrication of Gd³⁺ substituted nickel spinel ferrite (NiGd_xFe_2-xO₄) nanoparticles was carried out via co-precipitation route. X-ray powder diffraction (XRD) confirmed the spinel cubic structure of NiGd_xFe_2-xO₄ nanoparticles. XRD data also facilitated to determine the divalent and trivalent metal cations distribution at both A and B sites of the ferrite lattice. Site radii, hopping and bond lengths were also calculated from XRD data. The spectral studies elucidated the formation of cubic spinel ferrite structure as well as stretching vibrations of M–O (metal–oxygen) bond at A and B sites of ferrites, represented by two major bands υ₁ and υ₂ respectively. FESEM analysis confirmed the irregular morphology of NiGd_xFe_2-xO₄ nanoparticles. EDX spectrographs estimated the elemental compositions. The dielectric attributes were explained on the basis of the Debye-relaxation theory and Koop’s phenomenological model. At higher applied frequencies (AC) no prominent dielectric loss was observed. Magnetic parameter variations can be attributed to the substitution of the rare earth cations having larger ionic radii as compared to the radii of Fe³⁺ ions. Moreover, spin canting, magneto-crystalline anisotropy and exchange energy of electrons also helped in magnetic evaluation. Due to small coercivity values NiGd_xFe_2-xO₄ nanoparticles can be employed significantly in high-frequency data storage devices.     

Preparation of Mg/Fe spinel ferrite nanoparticles from Mg/Fe-LDH microcrystallites under mild conditions

Mg/Fe spinel ferrite nanoparticles were prepared by aging Mg²⁺/Fe²⁺/Fe³⁺-LDH (layered double hydroxides) suspension at temperature below 100 °C. The yield of Mg/Fe spinel ferrite nanoparticles was dependent on the aging temperature and the molar ratio of ferrous ions in the LDH precursors. It was found that the majority of iron atoms was assembled into the lattice of spinel ferrite when the LDH precursors were aged at 95 °C for 18 h, and the formation of Mg/Fe spinel ferrite was favored with a higher molar ratio of ferrous ion in the LDH precursors. To the best knowledge of us, it is the first report on preparation of spinel ferrite under such a mild condition of below 100 °C from Mg²⁺/Fe²⁺/Fe³⁺-LDH microcrystallites.     

Cyanide-bridged [Fe8M6] clusters displaying single-molecule magnetism (M=Ni) and electron-transfer-coupled spin transitions (M=Co)

Cyanide‐bridged metal complexes of [Fe₈M₆(μ‐CN)₁₄(CN)₁₀ (tp)₈(HL)₁₀(CH₃CN)₂][PF₆]₄?n CH₃CN?m H₂O (HL=3‐(2‐pyridyl)‐5‐[4‐(diphenylamino)phenyl]‐1H‐pyrazole), tp^?=hydrotris(pyrazolylborate), 1 : M=Ni with n=11 and m=7, and 2 : M=Co with n=14 and m=5) were prepared. Complexes 1 and 2 are isomorphous, and crystallized in the monoclinic space group P2₁/n. They have tetradecanuclear cores composed of eight low‐spin (LS) Fe^III and six high‐spin (HS) M^II ions (M=Ni and Co), all of which are bridged by cyanide ions, to form a crown‐like core structure. Magnetic susceptibility measurements revealed that intramolecular ferro‐ and antiferromagnetic interactions are operative in 1 and in a fresh sample of 2 , respectively. Ac magnetic susceptibility measurements of 1 showed frequency‐dependent in‐ and out‐of‐phase signals, characteristic of single‐molecule magnetism (SMM), while desolvated samples of 2 showed thermal‐ and photoinduced intramolecular electron‐transfer‐coupled spin transition (ETCST) between the [(LS‐Fe^II)₃(LS‐Fe^III)₅(HS‐Co^II)₃(LS‐Co^III)₃] and the [(LS‐Fe^III)₈(HS‐Co^II)₆] states.     

Production of Zinc-Doped Yttrium Ferrite Nanopowders by the Sol–Gel Method

Zinc-doped yttrium orthoferrite nanocrystals having the perovskite structure were prepared by coprecipitation of yttrium, zinc, and iron hydroxides. The limiting zinc doping level of the yttrium ferrite to yield a ZnFe₂O₄ spinel second phase was determined. The yttrium orthoferrite particle size was found to be a nonmonotone function of dopant concentration. The specific magnetization of yttrium ferrite nanocrystals increases with increasing zinc doping level from 0.242 A m²/kg (in undoped YFeO₃) to 1.327 A m²/kg (the ratio (1–x)YFeO₃: xZn (x = 0.4)) at Т = 300 K in 1250-kA/m field. A zinc ferrite impurity in samples enhances the ferromagnetism of the material.     

Redox‐Inert Fe3+ Ions in Octahedral Sites of Co‐Fe Spinel Oxides with Enhanced Oxygen Catalytic Activity for Rechargeable Zinc–Air Batteries

Bimetallic cobalt‐based spinel is sparking much interest, most notably for its excellent bifunctional performance. However, the effect of Fe³⁺ doping in Co₃O₄ spinel remains poorly understood, mainly because the surface state of a catalyst is difficult to characterize. Herein, a bifunctional oxygen electrode composed of spinel Co₂FeO₄/(Co_0.72Fe_0.28)_Td(Co_1.28Fe_0.72)_OctO₄ nanoparticles grown on N‐doped carbon nanotubes (NCNTs) is designed, which exhibits superior performance to state‐of‐the‐art noble metal catalysts. Theoretical calculations and magnetic measurements reveal that the introduction of Fe³⁺ ions into the Co₃O₄ network causes delocalization of the Co 3d electrons and spin‐state transition. Fe³⁺ ions can effectively activate adjacent Co³⁺ ions under the action of both spin and charge effect, resulting in the enhanced intrinsic oxygen catalytic activity of the hybrid spinel Co₂FeO₄. This work provides not only a promising bifunctional electrode for zinc–air batteries, but also offers a new insight to understand the Co‐Fe spinel oxides for oxygen electrocatalysis.     

镧掺杂对大洋锰结核制备铁氧体磁性的影响

大洋锰结核又称铁锰结核、多金属结核,常见于4 000～6 000 m的海底沉积物表层,在世界各大洋底均有分布,预计总储量超过3×1012 t[1].天然锰结核含有Mn和Fe,以及Cu、Co、Ni、铂族和稀土等60多种金属元素,其中锰占20%～30%,铁约占3～20%[2].从化学成分而言,大洋锰结核与Mn-铁氧体(铁酸锰)十分接近.以锰结核为原料合成Mn-铁氧体可以为这种天然资源的开发利用提供新思路.     

Obtaining of Ni<Subscript>0.65</Subscript>Zn<Subscript>0.35</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>/SiO<Subscript>2</Subscript> nanocomposites by thermal decomposition of complex compounds embedded in silica matrix

This article presents the results of our investigation on the obtaining of Ni_0.65Zn_0.35Fe₂O₄ ferrite nanoparticles embedded in a SiO₂ matrix using a modified sol–gel synthesis method, starting from tetraethylorthosilicate (TEOS), metal (Fe^III,Ni^II,Zn^II) nitrates and ethylene glycol (EG). This method consists in the formation of carboxylate type complexes, inside the silica matrix, used as forerunners for the ferrite/silica nanocomposites. We prepared gels with different compositions, in order to obtain, through a suitable thermal treatment, the nanocomposites (Ni_0.65Zn_0.35Fe₂O₄)_x–(SiO₂)_100–x (where x=10, 20, 30, 40, 50, 60 mass%). The synthesized gels were studied by differential thermal analysis (DTA), thermogravimetry (TG) and FTIR spectroscopy. The formation of Ni–Zn ferrite in the silica matrix and the behavior in an external magnetic field were studied by X-ray diffraction (XRD) and quasi-static magnetic measurements (50 Hz).     

Heterotrimetallic Coordination Polymers: {CuIILnIIIFeIII} Chains and {NiIILnIIIFeIII} Layers: Synthesis,Crystal Structures,and Magnetic Properties

The use of the [Fe^III(AA)(CN)₄]^? complex anion as metalloligand towards the preformed [Cu^II(valpn)Ln^III]³⁺ or [Ni^II(valpn)Ln^III]³⁺ heterometallic complex cations (AA=2,2′‐bipyridine (bipy) and 1,10‐phenathroline (phen); H₂valpn=1,3‐propanediyl‐bis(2‐iminomethylene‐6‐methoxyphenol)) allowed the preparation of two families of heterotrimetallic complexes: three isostructural 1D coordination polymers of general formula {[Cu^II(valpn)Ln^III(H₂O)₃(μ‐NC)₂Fe^III(phen)(CN)₂ {(μ‐NC)Fe^III(phen)(CN)₃}]NO₃ ? 7 H₂O}_n (Ln=Gd ( 1 ), Tb ( 2 ), and Dy ( 3 )) and the trinuclear complex [Cu^II(valpn)La^III(OH₂)₃(O₂NO)(μ‐NC)Fe^III(phen)(CN)₃] ? NO₃ ? H₂O ? CH₃CN ( 4 ) were obtained with the [Cu^II(valpn)Ln^III]³⁺ assembling unit, whereas three isostructural heterotrimetallic 2D networks, {[Ni^II(valpn)Ln^III(ONO₂)₂(H₂O)(μ‐NC)₃Fe^III(bipy)(CN)] ? 2 H₂O ? 2 CH₃CN}_n (Ln=Gd ( 5 ), Tb ( 6 ), and Dy ( 7 )) resulted with the related [Ni^II(valpn)Ln^III]³⁺ precursor. The crystal structure of compound 4 consists of discrete heterotrimetallic complex cations, [Cu^II(valpn)La^III(OH₂)₃(O₂NO)(μ‐NC)Fe^III(phen)(CN)₃]⁺, nitrate counterions, and non‐coordinate water and acetonitrile molecules. The heteroleptic {Fe^III(bipy)(CN)₄} moiety in 5 – 7 acts as a tris‐monodentate ligand towards three {Ni^II(valpn)Ln^III} binuclear nodes leading to heterotrimetallic 2D networks. The ferromagnetic interaction through the diphenoxo bridge in the Cu^II?Ln^III ( 1 – 3 ) and Ni^II?Ln^III ( 5 – 7 ) units, as well as through the single cyanide bridge between the Fe^III and either Ni^II ( 5 – 7 ) or Cu^II ( 4 ) account for the overall ferromagnetic behavior observed in 1 – 7 . DFT‐type calculations were performed to substantiate the magnetic interactions in 1 , 4 , and 5 . Interestingly, compound 6 exhibits slow relaxation of the magnetization with maxima of the out‐of‐phase ac signals below 4.0 K in the lack of a dc field, the values of the pre‐exponential factor (τ_o) and energy barrier (E_a) through the Arrhenius equation being 2.0×10^?12 s and 29.1 cm^?1, respectively. In the case of 7 , the ferromagnetic interactions through the double phenoxo (Ni^II–Dy^III) and single cyanide (Fe^III–Ni^II) pathways are masked by the depopulation of the Stark levels of the Dy^III ion, this feature most likely accounting for the continuous decrease of χ_M T upon cooling observed for this last compound.     

Study on synthesis of superparamagnetic spinel cobalt ferrite nanoparticles as layered double hydroxides by co-precipitation method

Cobalt ferrite layered double hydroxide (LDH) nanoparticles with cubic structure were synthesized by the co-precipitation method: addition of NaOH solution to a solution of Co²⁺ and Fe³⁺. Formation of nanoparticles was confirmed by XRD, SEM, TEM, PSA, FT-IR, TGA, DSC, and magnetic characteristics were measured using VSM. Crystals produced by calcination at 900°C possessed high coercivity and pronounced physical and chemical stability. Nanoparticles of CoFe₂O₄ formed outer layers with poor crystallization on the surface of cobalt ferrite nanocrystals.