Magnetically‐Confined Fe‐Mn Bimetallic Oxide Encapsulation as an Efficient and Recoverable Adsorbent for Arsenic(III) Removal

Synthesis of bimetallic‐oxide‐encapsulated magnetic nanoparticles is still significantly challenging and has rarely been attempted previously, due to the effects of lattice mismatch, weak chemical interactions and variances in growth rates between different components, as well as the difficulty in process control for uniform co‐deposition. In the present work, Fe‐Mn bimetallic oxide (FMBO) nanoplatelet encapsulated magnetic nanoparticles (Mag‐FeMn) are prepared by controlled engineering of the interparticle coupling of Fe₃O₄ and FMBO, with its multifunctional capabilities highlighted in terms of the potentially superior As(III) sequestration and convenient recoverability. Multiple characterization techniques are employed to examine the derived morphologies and to accurately resolve both compositionally and magnetically the hierarchical structure in detail. The synthesized magnetic composites retain highly porous structure with the main components of Fe₂O₃, FeOOH, Fe₃O₄, and Mn₃O₄. Mag‐FeMn exhibits a quite competitive high capacity for As(III) capture (56.1 mg g^–1), whereby As(III) oxidation coupled with synchronous sorption contributes to the improved performance. The unique heterostructure of FMBO encapsulation with an embedded magnetic core would be applicable to help with rational synthesis of other bimetallic oxide encapsulated magnetic nanoparticles, and definitely shows promise for the development of new nanotechnology enabled approaches for adsorption‐based water purification.     

Tracking of transplanted mesenchymal stem cells labeled with fluorescent magnetic nanoparticle in liver cirrhosis rat model with 3-T MRI

In vivo visualization of transplanted stem cells with noninvasive technique is essential for the monitoring of cell implantation, homing and differentiation. At present, superparamagnetic iron oxide (SPIO) is most commonly used for cell labeling. However, stem cells lack phagocytic capacity and transfection agent is required for sufficient internalization of SPIO for cellular imaging. However, the potential hazards of transfection agents are not fully investigated. Instead of SPIO, we used commercially available new tagging material, fluorescent magnetic nanoparticle (MNP) containing rhodamine B isothiocyanate within a silica shell (Biterials, Seoul, Korea). This tagging material does not require transfection agents for the cell labeling. In addition to that, the core of this MNP is composed of ferrite and the inner portion of silica shell contains fluorescent materials, therefore, it has both magnetic and optical features. This study was designed to track intrasplenically injected bone marrow mesenchymal stem cells (MSCs) labeled with fluorescent MNP in liver cirrhosis rat model with 3-T magnetic resonance equipment. We compared magnetic resonance imaging (MRI) of livers in rats which were injected with non-labeled stem cells or labeled stem cells with MNP or SPIO. We found that the respective liver-to-muscle contrast-to-noise ratios at 3 and 5 h after MNP or SPIO-labeled stem cell injection was significantly lower than that of pre-injection and non-labeled group. There was no significant difference between MNP-labeled group and SPIO-labeled group. We can effectively detect intrasplenically injected MNP-labeled MSCs in an experimental rat model of liver cirrhosis with 3-T MRI.     

Ultrathin silver‐coated gold nanoparticles as suitable substrate for surface‐enhanced Raman scattering

Surface‐enhanced Raman scattering (SERS) is an extremely powerful tool for the analysis of the composition of bimetallic nanoparticle (BNP) surfaces because of the different adsorption schemes adopted by several molecules on different metals, such as Au and Ag. The preparation of BNPs normally implies a change in the plasmonic properties of the core metal. However, for technological applications it could be interesting to synthesize core–shell structures preserving these original plasmonic properties. In this work, we present a facile method for coating colloidal gold nanoparticles (NPs) in solution with a very thin shell of silver. The resulting bimetallic Au@Ag system maintains the optical properties of gold but shows the chemical surface affinity of silver. The effectiveness of the coating method, as well as the progressive silver enrichment of the outermost part of the Au NPs, has been monitored through the SERS spectra of several species (chloride, luteolin, thiophenol and lucigenin), which show different behaviors on gold and silver surfaces. A growth mechanism of the Ag shell is proposed on the basis of the spectroscopic and microscopic data consisting in the formation and deposit of Ag clusters on the Au NP surface. Copyright © 2009 John Wiley & Sons, Ltd.     

Interaction between rhodanine and silver species on a nanocolloidal surface and in the solid state

This paper discusses and compares molecular interactions of rhodanine (Rd), the heterocyclic compound containing N, S, and O atoms, with two forms of silver species, i.e. Ag(I) ions and silver nanocolloidal particles. Vibrational spectroscopic and powder crystallography studies on coordination of Ag(I) ions in the solid state, supported by density functional theory, clearly indicate complexation through the nitrogen (the deprotonated imino group) and exocyclic sulfur atoms. Molecules of the complex are arranged in a one‐dimensional infinite polymeric chain structure that intertwines to give a helix motif. On the other hand, adsorption geometry of Rd on the silver surface was determined by using surface‐enhancement Raman scattering (SERS) spectroscopy. Observed differences between the SERS and the normal Raman spectra of Rd suggest that Rd adsorbs on the silver species after the rearrangement of the keto‐thione form into the enol‐thiol tautomer in acidic and neutral solutions. This leads to adsorption on this silver species through the thiolate ion. On the other hand, the alkaline pH forces first N‐deprotonation of Rd, and, in consequence, the obtained anion of the keto‐thione form interacts with the silver surface as a result of the presence of lone pairs of nitrogen and sulfur atoms, similar to the case discussed for the solid state. Copyright © 2009 John Wiley & Sons, Ltd.     

Direct visual evidence for chemical mechanisms of SERRS via charge transfer in Au20–pyrazine–Au20 junction

The essence of the chemical mechanism for surface‐enhanced resonance Raman scattering (SERRS) is the charge transfer (CT) between the metal and the molecule at the resonant electronic transition, which results in the mode‐selective enhancement in the SERRS spectrum. The site‐orientated CT can directly interpret the mode‐selective chemical enhancement in SERRS. However, it is a great challenge to intutively visualize the orientation and site of the CT. In this paper, for the pyrazine–Au₂ complex, a three‐dimensional (3D) cubic representation is built to provide direct visual evidence for chemical mechanisms of SERRS via CT from the Au₂ cluster to pyrazine at the resonant electronic transition. The relationship between the mode‐selective enhancements in SERRS and the site‐orientated CT was clearly revealed. The intracluster excitation (analog of plasmon excitation in large naonoparticles) was also visualized by the 3D cubic presentation, which provided the direct evidence of local electromagnetic field enhancement of SERRS. To study the quantum size effect and the coupling effect of the nanoparticles, the photoexcitation mechanisms of the Au₂₀–pyrazine complex and the Au₂₀–pyrazine–Au₂₀ junction were also investigated. The tunneling charge transfer from one Au₂₀ cluster to another Au₂₀ cluster outside the pyrazine in Au₂₀–pyrazine–Au₂₀ junction was also revealed visually. The calculated normalized extinction spectra of Au nanoparticles using the generalized Mie theory reveal that the resonance peak is red‐shifted due to the coupling between particles. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of gold nanoparticle size on acoustic cavitation using chemical dosimetry method

When a liquid is irradiated with high intensities of ultrasound irradiation, acoustic cavitation occurs. Acoustic cavitation generates free radicals from the breakdown of water and other molecules. Cavitation can be fatal to cells and is utilized to destroy cancer tumors. The existence of particles in liquid provides nucleation sites for cavitation bubbles and leads to decrease the ultrasonic intensity threshold needed for cavitation onset. In the present investigation, the effect of gold nanoparticles with appropriate amount and size on the acoustic cavitation activity has been shown by determining hydroxyl radicals in terephthalic acid solutions containing 15, 20, 28 and 35 nm gold nanoparticles sizes by using 1 MHz low level ultrasound. The effect of sonication intensity in hydroxyl radical production was considered.The recorded fluorescence signal in terephthalic acid solutions containing gold nanoparticles was considerably higher than the terephthalic acid solutions without gold nanoparticles at different intensities of ultrasound irradiation. Also, the results showed that the recorded fluorescence signal intensity in terephthalic acid solution containing finer size of gold nanoparticles was lower than the terephthalic acid solutions containing larger size of gold nanoparticles. Acoustic cavitation in the presence of gold nanoparticles can be used as a way for improving therapeutic effects on the tumors.     

Au_(38)团簇上小分子H_2O和O_2共同吸附的第一性原理研究

利用密度泛函理论(DFT)计算的方法,对O_2,H_2O单独吸附和共吸附在Au_(38)团簇上的吸附性质进行了结构,能量和电子分析.计算结果表明,O_2倾向于吸附在edge位,H_2O则倾向于吸附在top位.Au(100)表面较之Au(111)表面更有利于O_2,H_2O的吸附,这与实验结果相符合.H_2O和O_2共吸附研究表明,H_2O的存在促进了O_2的吸附.Mulliken和分态密度(PDOS)分析得出:在共吸附中,H_2O将部分电子转移给了O_2,促进了O_2的活化与解离,并生成了类似H_2O_2的中间态,从而为催化氧化反应提供了O活性物种.     

Pd/Au纳米结构制备和粒子组分自旋的谱学性能研究

为研究Pd/Au纳米结构制备和电催化性能、控制粒子大小组分和自旋,用油浴热分解方法制备了核/壳纳米结构Pd/Au双金属合金纳米颗粒,采用PVP和多元醇作表面活性剂和稳定剂,依据溶液浓度、颗粒大小、吸附能控制晶相获得了均匀、一致的2层和3层Pd/Au纳米样品,并采用HAADF和HRTEM测试了纳米结构尺寸形貌,用EDS测试了成分分布,试验产物用TEM/XRD进行了表征,结果表明,Pd/Au具有面心立方八面体结构,与Au/Pd核壳不同,纳米Pd/Au具有活性、耐久性、电催化性和稳定性。     

Growth and Characterization of CIS Thin Films Prepared by Ion Beam Sputtering Deposition

Copper indium diselenide （CuInSe2） thin films were prepared by ion beam sputtering Cu, In and Se targets continuously on BK7 glass substrates and the three-layer film was then annealed in the same vacuum chamber. X-ray diffraction shows that the CuInSe2 thin films have a single chalcopyrite structure with preferential （112） orientation. Scanning electron microscopy reveals that the CIS thin films consist of uniform and densely packed grain clusters. Energy dispersive x-ray spectroscopy demonstrates that the elemental composition of CIS films approaches the stochiometric composition ratios of 1：1：2. Raman measurement shows that the main peak is at about 174cm^-1 and this peak is identified as the A1 vibrational mode from chaicopyrite ordered CulnSe2. Optical transmission and absorption spectroscopy measurement reveal an energy band gap of about 1.05 eV and an absorption coefficient of 10^5 cm^-1. The film resistivity is about 0.01 Ωcm.     

离子液体存在下银的电沉积及其表面增强拉曼散射活性研究

离子液体作为一种绿色介质,在电化学领域的应用研究正在兴起,并已引起了研究者的浓厚兴趣。运用循环伏安法研究了离子液体(1-丁基-3-甲基咪唑硝酸盐,[bmim]NO₃)添加剂存在时,AgNO₃溶液中的Ag在玻碳电极上的电化学沉积行为。研究表明,离子液体的加入对Ag的沉积具有阻化作用。采用扫描电镜(SEM)对沉积层的表面形貌进行表征,结果显示离子液体的存在可使沉积层更加致密,Ag颗粒的尺寸减小。以甲基橙为探针分子,研究了在加入及不加[bmim]NO₃添加剂的AgNO₃溶液中电沉积所得银颗粒膜的表面增强拉曼散射(SERS)效应,增强因子分别为1.7×105和1.1×105,表明在离子液体存在下制得的Ag颗粒膜具有相对较好的SERS活性。