Growth-Temperature Dependence of Magnetic and Magneto-Transport Properties of Epitaxially Grown MnAs/GaAs Hybrid Multilayers

We successfully fabricated epitaxial MnAs/GaAs multilayers with a total thickness of 300 nm using molecular beam epitaxy. The periodicity of the samples was fixed at 5 nm/5 nm and the growth-temperature dependence of the magnetic and magneto-transport properties were studied. All samples studied exhibited ferromagnetism above room temperature. The magnetic anisotropy and magnetoresistance are strongly dependent on the growth temperature. These results indicate that it is possible to manipulate the magnetic and magneto-transport properties by changing the growth temperature.     

银纳米簇用于食品包装污染物的检测及其抗菌性能的应用

目的介绍荧光银纳米簇(AgNCs)的合成方法、荧光特性、抗菌活性,及其在食品包装中的应用。方法总结国内外AgNCs在食品包装检测领域的应用,以及其作为新型抗菌材料体现出的强大抗菌效力,提出AgNCs的不足之处和可能的解决方法。结论 AgNCs由于其光漂白性低、荧光量子产率高、经济效益好,可作为荧光材料设计生物传感器用于检测食品包装内的污染物。此类生物传感器具有检测快速、灵敏与特异性识别的优点。同时AgNCs具有大的表面积与体积比,高的局部表面Ag浓度、高迁移率及低毒性等特点,使其抗菌性能优于传统的银纳米材料,由此,展望了新型抗菌检测双重功效AgNCs传感器的设计。     

Cu掺杂ZnO纳米粒子的光学性能及铁磁性

利用溶胶凝胶法制备了纳米结构的Cu掺杂ZnO基稀磁半导体,通过X射线衍射分析表明,样品为纯相ZnO纤锌矿结构,磁性测量表明样品在室温下呈室温铁磁性,铁磁性来源为氧化锌晶格中的缺陷与Cu2+离子之间的交换作用。室温光致发光(PL)谱观察到紫外带边和可见光区两个发射峰,且随着Cu掺杂量增加,紫外峰淬灭,可见峰发射增强。     

Polymorphism of Phosphine‐Protected Gold Nanoclusters: Synthesis and Characterization of a New 22‐Gold‐Atom Cluster

A new Au₂₂ nanocluster, protected by bis(2‐diphenyl‐phosphino)ethyl ether (dppee or C₂₈H₂₈OP₂) ligand, has been synthsized and purified with high yield. Electrospray mass spectrometry shows that the new cluster has a formula of Au₂₂(dppee)₇, containing 22 gold atoms and seven dppee ligands. The cluster is found to be stable as a solid, but metastable in solution. The new cluster has been characterized by UV‐Vis‐NIR absorption spectroscopy, collision‐induced dissociation, and ³¹P‐NMR. The properties of the new cluster have been compared with the previous Au₂₂(dppo)₆ nanocluster (dppo = 1,8‐bis(diphenyl‐phosphino)octane or C₃₂H₃₆P₂), which contains two fused Au₁₁ units. All the experimental data indicate that the new Au₂₂(dppee)₇ cluster is different from the previously known Au₂₂(dppo)₆ cluster and represents a new Au₂₂ core, which contains most likely one Au₁₁ motif with several Au₂(dppee) or Au(dppee) units. The Au₂₂(dppee)₇ cluster provides a new example of the ligand effects on the nuclearity and structural polymorphism of phosphine‐protected atom‐precise gold nanoclusters.     

新型电工钢片磁性能无损检测传感器及应用

介绍了一种新型电工钢片磁性能无损检测传感器及其测量原理 ,同时讨论了该传感器的设计原则并给出了典型数据及仿真测试结果     

不同直径玻璃包覆非晶微丝的制备及其磁性能

采用熔融拉丝法制备了直径范围分别在6.1～28.0μm和14.0～35.2μm之间的玻璃包覆非晶Fe基和Co基合金微丝, 测试了不同合金直径和不同玻璃包覆层厚度的玻璃包覆合金微丝样品的静磁性能. 结果表明: 轴向矫顽力和轴向剩磁比随着微丝直径的增大而降低, 随着玻璃包覆层的增大而升高; 径向剩磁比的变化趋势则相反. 微丝合金直径和玻璃包覆层厚度改变, 静磁性能变化的主要原因是作用在合金芯上的内应力的变化, 导致了具有不同磁畴结构的合金内芯区和合金外壳区体积比的改变.     

Ionic Gel Modulation of RKKY Interactions in Synthetic Anti‐Ferromagnetic Nanostructures for Low Power Wearable Spintronic Devices

To meet the demand of developing compatible and energy‐efficient flexible spintronics, voltage manipulation of magnetism on soft substrates is in demand. Here, a voltage tunable flexible field‐effect transistor structure by ionic gel (IG) gating in perpendicular synthetic anti‐ferromagnetic nanostructure is demonstrated. As a result, the interlayer Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction can be tuned electrically at room temperature. With a circuit gating voltage, anti‐ferromagnetic (AFM) ordering is enhanced or converted into an AFM–ferromagnetic (FM) intermediate state, accompanying with the dynamic domain switching. This IG gating process can be repeated stably at different curvatures, confirming an excellent mechanical property. The IG‐induced modification of interlayer exchange coupling is related to the change of Fermi level aroused by the disturbance of itinerant electrons. The voltage modulation of RKKY interaction with excellent flexibility proposes an application potential for wearable spintronic devices with energy efficiency and ultralow operation voltage.     

残余应力对SrRuO3薄膜磁学及电输运性能的影响

采用射频磁控溅射法在单晶SrTiO₃ (STO)衬底和硅(Si)衬底上制备出不同取向的SrRuO₃ (SRO)薄膜, 对薄膜的残余应力进行了分析, 并研究了应力对不同取向SRO薄膜磁学性能与电输运特性的影响。根据X射线衍射(XRD)结果分析可知, Si基SRO薄膜为多晶单轴取向薄膜, 且应力来源主要为热失配拉应力; STO基SRO薄膜为外延薄膜, 其应力主要为热失配压应力和外延压应力; 磁学性能测试表明, (001)取向SRO薄膜比(110)取向薄膜拥有更高的居里温度T_C; 压应力提高了(001)取向SRO薄膜的T_C, 却降低了(110)取向薄膜的T_C。电阻性能测试表明, 对于在同种类型衬底上沉积的SRO薄膜, (001)取向的薄膜的剩余表面电阻比(RRR)高于(110)取向的薄膜。另外, 拉应力引起了薄膜微结构的无序度增加, 弱化了表面电阻率的温度依赖性, 提高了金属绝缘体转变温度(T_MI)。     

Facile Aqueous‐Phase Synthesis of Biocompatible and Fluorescent Ag2S Nanoclusters for Bioimaging: Tunable Photoluminescence from Red to Near Infrared

Low toxicity and fluorescent nanomaterials have many advantages in biological imaging. Herein, a novel and facile aqueous‐phase approach to prepare biocompatible and fluorescent Ag₂S nanoclusters (NCs) is designed and investigated. The resultant Ag₂S NCs show tunable luminescence from the visible red (624 nm) to the near infrared (NIR; 724 nm) corresponding to the increasing size of the NCs. The key for preparing tunable fluorescent Ag₂S NCs is the proper choice of capping reagent, glutathione (GSH), and the novel sulfur‐hydrazine hydrate complex as the S^2? source. As a naturally occurring and readily available tripeptide, GSH functions as an important scaffold to prevent NCs from growing large nanoparticles. Additionally, GSH is a small biomolecule with several functional groups, including carboxyl and amino groups, which suggests the resultant Ag₂S NCs are well‐dispersed in aqueous solution. These advantages make the as‐prepared Ag₂S NCs potentially applicable to biological labeling as well. For example, the resultant Ag₂S NCs are used as a probe for MC3T3‐EI cellular imaging.     

Fe_3O_4@MgO纳米复合材料的制备及其对Pb~(2+)的吸附性能

采用两步化学沉淀法制备了Fe_3O_4@MgO纳米复合材料,研究了纳米复合材料对Pb~(2+)的吸附性能。结果表明,所制备的复合材料具有较高的顺磁性和稳定性,其饱和磁化强度为58.07 emu/g,初始氧化增重温度为125℃,对Pb~(2+)有较好的吸附能力,在50 min内可以达到吸附平衡,最大吸附量为711.5 mg/g,其吸附过程符合准二级动力学模型和Langmuir等温吸附模型。     

Nanohybrids with Magnetic and Persistent Luminescence Properties for Cell Labeling,Tracking, In Vivo Real‐Time Imaging,and Magnetic Vectorization

Once injected into a living organism, cells diffuse or migrate around the initial injection point and become impossible to be visualized and tracked in vivo. The present work concerns the development of a new technique for therapeutic cell labeling and subsequent in vivo visualization and magnetic retention. It is hypothesized and subsequently demonstrated that nanohybrids made of persistent luminescence nanoparticles and ultrasmall superparamagnetic iron oxide nanoparticles incorporated into a silica matrix can be used as an effective nanoplatform to label therapeutic cells in a nontoxic way in order to dynamically track them in real‐time in vitro and in living mice. As a proof‐of‐concept, it is shown that once injected, these labeled cells can be visualized and attracted in vivo using a magnet. This first step suggests that these nanohybrids represent efficient multifunctional nanoprobes for further imaging guided cell therapies development.     

Facile Synthesis of Bimetallic Ag/Ni Core/Sheath Nanowires and Their Magnetic and Electrical Properties

This paper describes a facile method for coating Ag nanowires with uniform, ferromagnetic sheaths made of polycrystalline Ni. A typical sample of these core/sheath nanowires had a saturation magnetization around 33 emu g^?1. We also demonstrated the use of this magnetic property to align the nanowires by simply placing a suspension of the nanowires on a substrate in a magnetic field and allowing the solvent to evaporate. The electrical conductivity of these core/sheath nanowires (2 × 10³ S cm^?1) was two orders of magnitude lower than that of bulk Ag (6.3 × 10⁵ S cm^?1) and Ni (1.4 × 10⁵ S cm^?1). This is likely caused by the transfer of electrons from the Ag core to the Ni sheath due to the difference in work function between the two metals. The electrons are expected to experience an increased resistance due to spin‐dependent scattering caused by the randomized magnetic domains in the polycrystalline, ferromagnetic Ni sheath. Studies on the structural changes to the Ni coating over time under different storage conditions show that storage of the nanowires on a substrate under ambient conditions leads to very little Ni oxidation after 6 months. These Ag/Ni core/sheath nanowires show promise in areas such as electronics, spintronics, and displays.     

Thermal Transport Properties of Layered Materials: Identification by a New Numerical Algorithm for Transient Measurements

Transient methods are widely used to determine thermal transport properties. In some situations they can be used for homogeneous media to measure several properties either simultaneously or separately. In this context an analytic model is available and a well-posed inverse problem of parameter identification has to be solved. The examination of composite media is more complicated. The algorithm proposed here allows simultaneous determination of the thermal conductivity and thermal diffusivity of layered dielectrics by transient measurements. It is based on a plane source that acts both as a resistive heater and temperature sensor. For the technique to be successful two essential aspects have to be considered: firstly, the mathematical modeling of the measured data (the forward problem) and secondly, the problem of ill-posedness of the inverse problem. For the proposed measurement configuration, a new fast data analysis algorithm based on an analytic solution for the forward problem is presented. In principle, a numerical solution such as an FEM solution of the heat conduction equation can be used instead of the analytical one, but the computational effort is much greater. The inverse problem is formulated as an output-least-squares problem, which leads to a transcendent algebraic system of equations. The method was successfully tested for different situations.Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22--27, 2003, Boulder, Colorado, U.S.A.     

The Shortening of MWNT‐SPION Hybrids by Steam Treatment Improves Their Magnetic Resonance Imaging Properties In Vitro and In Vivo

Carbon nanotubes (CNTs) have been advocated as promising nanocarriers in the biomedical field. Their high surface area and needle‐like shape make these systems especially attractive for diagnostic and therapeutic applications. Biocompatibility, cell internalization, biodistribution, and pharmacokinetic profile have all been reported to be length dependent. In this study, further insights are gotten on the role that the length of CNTs plays when developing novel contrast agents for magnetic resonance imaging (MRI). Two samples of CNTs with different length distribution have been decorated with radio‐labeled iron oxide nanoparticles. Despite characterization of the prepared hybrids reveals a similar degree of loading and size of the nanoparticles for both samples, the use of short CNTs is found to enhance the MRI properties of the developed contrast agents both in vitro and in vivo compared to their long counterparts.     

Laser‐Induced Freestanding Graphene Papers: A New Route of Scalable Fabrication with Tunable Morphologies and Properties for Multifunctional Devices and Structures

The recently emergent laser‐induced graphene (LIG) technology has endowed the fabrication of smart devices with one‐step processing and scalable/designable features. Graphene paper (GP), an important architecture of 2D layered carbon, however, is never produced through LIG. Herein, a novel strategy is reported for production of freestanding GP through LIG technology. It is first determined that the unique spatial configuration of polyimide (PI) paper is critical for the preparation of GP without the appearance of intense shape distortion. Benefiting from the mechanism, the as‐produced laser‐induced graphene paper (LIGP) is foldable, trimmable, and integratable to customized shapes and structures with the largest dimension of 40 × 35 cm². Based on the processing–structure–property relationship study, one is capable of controlling and tuning various physical and chemical properties of LIGPs, rendering them unique for assembling flexible electronics and smart structures, e.g., human/robotic motion detectors, liquid sensors, water–oil separators, antibacterial media, and flame retardant/deicing/self‐sensing composites. With the key findings, the escalation of LIGP for commercialization, roll‐to‐roll manufacturing, and multidisciplinary applications are highly expected.     

用恒热流法测定多孔介质的热质迁移特性参数

设计了一种测定多孔介质热质迁移特性的实验装置。通过测定该装置中多孔介质的局部温含量和温度，结合恒热流下一维半无限大多孔介质热质迁移微分方程的解，得到了石英砂、玻璃珠等多孔介质的质扩散系数、热质扩散系数、名义热扩散系数、名义导热系数等热质迁移特性参数以及这些参数随湿含量、温度的变化。此外，还讨论了加热功率、初始湿含量等因素对测量的影响。     

Co掺杂ZnO块材的晶体结构和磁性能研究

采用固相法制备了Zn1-xCoxO（x=0．05-0．25）块材,烧结温度和Co含量对Zn1-xCoxO（x=0．05-0．25）块材的晶体结构和室温磁性能影响强烈,当x≤0．1,烧结温度从800增加到1100℃时,Zn1-xCoxO（x=0．05-0．25）呈现出单相结构,但当x〉0．1,烧结温度为800℃时,样品中出现CoO相;随着烧结温度提高到900℃,样品再次获得纯的单相结构。为了获得高的饱和磁化强度Ms,最佳烧结温度应该根据Co含量进行调整。在最佳烧结温度条件下,当x从0．05提高到0．1时,Ms从0．79增加到了1．06μB/Co,但当x继续提高到0．2和0．25时,Ms分别降低到了0．59和0．41μB/Co。