Synthesis of mixed metallic nanoparticles by spark discharge

Short spark discharges (2 μs) were successfully applied to generate mixed particles a few nanometres in diameter by fast quenching. Alloyed Cr–Co electrodes were applied to demonstrate this. Further it was shown that if the anode and the cathode are different materials, the discharge process mixes the vapour of both materials, forming mixed nanoparticles. Electron microscopy (TEM, SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses were performed on the collected particles to study their size, morphology, composition and structure. The average compositions of the particles were measured by inductively coupled plasma (ICP). In addition, online measurements of the particle size distribution by mobility analysis were carried out. In the case of alloyed electrodes (Cr–Co), the relative concentration of the elements in the nanoparticulate sample was consistent with the electrode composition. When using electrodes of different metals (Au–Pd and Ag–Pd) the individual nanoparticles showed a range of mixing ratios. No surface segregation was observed in these mixed noble metal particles. Crystalline nanoparticulate mixed phases were found in all cases.     

液相法制备金属纳米粒子

液相法是在均相溶液中，利用各种途径引发化学反应，通过均相或异相成核及随后的扩散生长而制备出粒径分布窄且表面功能化的纳米尺度材料．介绍了液-液两相法、反相胶束、高温液相法等制备单分散金属纳米粒子的方法和高温液相法制备金属纳米粒子的影响因素，以及近年来在金属纳米粒子的制备和性能研究上的进展，尤其是Co等多种磁性纳米粒子的制备、磁性研究．     

Layer by layer growth of silver chloride nanoparticle within the pore channels of SBA-15/SO3H mesoporous silica (AgClNP/SBA-15/SO3K): Synthesis,characterization and antibacterial properties

The growth of silver chloride nanoparticles within the pore channels of functionalized SBA-15 mesoporous was achieved by sequential dipping steps in alternating bath of potassium chloride and silver nitrate under ultrasound irradiation at pH=9. The effects of sequential dipping steps in growth of the AgCl nanoparticles have been studied. The growth and formation of AgCl nanoparticles inside the sulfonated SBA-15 were characterized by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Antibacterial activity of the synthesized materials was investigated against Escherichia coli (E.coli) using the conventional diffusion-disc method. The materials showed high antibacterial activity.     

Compaction of agglomerates of aerosol nanoparticles: A compilation of experimental data

The compacting behavior of agglomerated aerosol nanoparticles in the size range between 7 and 150 nm was investigated using available literature data. We observed a characteristic behavior, which can be described by three separate steps. When comparing the first step, the compaction from agglomerates into spherules, differences could be observed for nanoparticles of different materials. It is seen from the available data that smaller particles compact at lower temperatures. For most materials where data available (Ag, Au, Fe, W, PbS and SnO₂), the compaction temperatures were found to lie in a temperature interval, between 1/3 and 1/2 of the bulk melting temperature. For the data available on TiO₂, on the other hand, the compaction temperature corresponds to about 2/3 of the bulk melting temperature. Thus, a fundamental difference might exist in the sintering behavior of titania as compared with other materials. This difference may be attributed to a lower degree of cleanliness of the titania particles.     

Engineering Protein Venoms as Self-Assembling CXCR4-Targeted Cytotoxic Nanoparticles

Protein venoms are effective cytotoxic molecules that when conveniently targeted to tumoral markers can be exploited as promising anticancer drugs. Here, it is explored whether the structurally unrelated melittin, gomesin, and CLIP71 could be functionally active when engineered, in form of GFP fusions, as self-assembling multimeric nanoparticles. Incorporated in modular constructs including a C-terminal polyhistidine tag and an N-terminal peptidic ligand of the cytokine receptor CXCR4 (overexpressed in more than 20 human neoplasias), these venoms are well produced in recombinant bacteria as proteolytically stable regular nanoparticles ranging between 12 and 35 nm. Being highly fluorescent, these materials selectively penetrate, label, and kill CXCR4⁺ tumor cells in a CXCR4-dependent fashion. The obtained data support the concept of recombinant venoms as promising drugs, through the precise formulation as tumor-targeted nanomaterials for selective theragnostic applications in CXCR4⁺ cancers.     

Processing, properties and some novel applications of magnetic nanoparticles

Magnetic nanoparticles have been prepared by various soft chemical methods including self-assembly. The bare or surface-modified particles find applications in areas such as hyperthermia treatment of cancer and magnetic field-assisted radioactive chemical separation. We present here some of the salient features of processing of nanostructured magnetic materials of different sizes and shapes, their properties and some possible applications. The materials studied included metals, metal-ceramic composites, and ferrites.     

Organometal Halide Perovskites: Bulk Low‐Dimension Materials and Nanoparticles

Organometal halide perovskites (hybrid perovskites) contain an anionic metal–halogen‐semiconducting framework and charge‐compensating organic cations. As hybrid materials, they combine useful properties of both organic and inorganic materials, such as plastic mechanical properties and good electronic mobility related to organic and inorganic material, respectively. They are prepared from abundant and low cost starting compounds. The perovskite stoichiometry is associated with the dimensionality of its inorganic framework, which can vary from three to zero, 3D consisting of corner‐sharing MX₆ octahedra, and 0D consisting of isolated octahedra. Small‐sized organic cations can fit into the MX₆ octahedra of the 3D framework and in all dimensions organic cations surround the inorganic framework. Regarding the low dimensionality in the material, this refers to at least one of its dimensions being shorter than approximately 100 nanometers. These materials should be considered as genuine nanomaterials or as bulk materials depending on whether they have three or less than three dimensions on the nanoscale, respectively. In principle, hybrid perovskite nanoparticles can be prepared with different shapes and with inorganic framework dimensionalities varying from 0D to 3D, and this also applies to the bulk material. This report is mainly focused on the unique properties of organometal halide perovskite nanoparticles.     

Nanoparticles Engineering for Lithium‐Ion Batteries

Lithium‐ion batteries (LIBs) have been extensively investigated due to the ever‐increasing demand for new electrode materials for electric vehicles (EVs) and clean energy storage. A wide variety of nano/microstructured LIBs electrode materials are hitherto created via self‐assembly, ranging from 0D nanospheres; 1D nanorods, nanowires, or nanobelts; and 2D nanofilms to 3D nanorod array films. Nanoparticles can be utilized to build up integrated architectures. Understanding of nanoparticles’ self‐assembly may provide information about their organization into large aggregates through low‐cost, high‐efficiency, and large‐scale synthesis. Here, the focus is on the recent advances in preparing hierarchically nano/microstructured electrode materials via self‐assembly. The hierarchical electrode materials are assembled from single component, binary to multicomponent building blocks via different driving forces including diverse chemical bonds and non‐covalent interactions. It is expected that nanoparticle engineering by high‐efficient self‐assembly process will impact the development of high‐performance electrode materials and high‐performance LIBs or other rechargeable batteries.     

Influence of synthesis conditions on structural,optical and magnetic properties of iron oxide nanoparticles prepared by hydrothermal method

The iron oxide nanoparticles were synthesized by a simple hydrothermal method at different heating temperatures and pH conditions. The synthesized materials were characterized by X-ray diffractometer, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, UV–visible spectrometer and vibrating sample magnetometer. With increment in pH of the synthesized materials were resulted in orthorhombic (goethite) and cubic (magnetite) structures at pH 6 and 12, respectively. The banding nature of synthesized materials was analyzed by infrared spectra. The synthesized powders at 130?°C showed higher percent of nanorods (length = 90–120 nm) in addition to lower percentage of nanoparticles. The material at pH 12 consisted of maximum nanoparticles with size = 10–60 nm with small agglomerations. Band gap energy of synthesized materials was 2.2–2.8 eV. Herein, the reaction conditions tuned the saturation magnetization (M_S). The maximum M_S (59.38 emu/g) was obtained at pH 12 and lower M_S (0.65 emu/g) was observed at pH 6 due to intrinsic property of goethite phase.     

Highly sensitive and selective trimethylamine sensors based on WO3 nanorods decorated with Au nanoparticles

One-dimensional tungsten oxide (WO₃) gas sensing materials have been widely used for the detection of trimethylamine (TMA) gas. Furthermore, it is believed that an effective method to improve the gas sensing performance is to introduce noble metals into sensing materials. In this work, a novel gas sensing material was prepared by decorating Au nanoparticles on WO₃ nanorods. Based on field emission scanning electron microscopy (FESEM/EDS), X-ray diffraction (XRD), and transmission electron microscopy (TEM), the morphology and microstructure of as-prepared samples were characterized. Results show that Au nanoparticles with diameter of 13–15 nm are loaded on the surface of WO₃ nanorods with length of about 1–2 µm and width of 50–80 nm. Gas sensing tests reveal that the Au@WO₃ sensor has remarkably enhanced response to TMA gas compared with pure WO₃ nanorods. In addition, and the gas sensing mechanism has been investigated based on the experimental results. The superior sensing features indicate the present Au@WO₃ nanocomposites are promising for gas sensors, which can be used in the detection of the trimethylamine gas and this work provides insights and strategies for the fabrication of sensing materials.     

Nonresonant Nonlinearity of Silver Nanoparticles

Results of experimental investigations of the process of nonlinear refraction in composite materials based on silver nanoparticles in the region far from the plasma surface resonance of the nanoparticles (λ = 1064 nm) are presented. The reflection Z-scanning technique was used for measurements, which made it possible to determine both the sign and the values of nonlinear refractive indices and real parts of the 3rd-order nonlinear susceptibility of composite materials. The mechanism responsible for the process of nonlinear refraction in specimens is discussed. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 5, pp. 650–653, September–October, 2005.     

层层自组装金纳米粒子表面等离子体引发光电流应用于等离子体增感太阳能电池

等离子体增感太阳能电池中,层层自组装金纳米粒子的表面等离子体共振能产生光电电流,金纳米粒子层的光电转换效率随表面等离子体共振强度的提升而增加。等离子体增感太阳能电池初步试验光电转换效能为0.75%。利用模型仿真电荷分离的现象、光电电流的产生,以及表面等离子体共振和光电电流产生之间的关系来解释实验结果。在未来,通过优化等离子体增感太阳能电池组件,可以进一步提升其转换效率。这在表面等离子体激活太阳能电池及等离子体太阳能电池领域将有很大应用潜力。     

Photonic crystals for applications in photoelectrochemical processes: Photoelectrochemical solar cells with inverse opal topology

Photonic crystal structures, that present strong light localization effects near photonic band gap frequency regions, can be very useful to maximize chemical processes of phototoactive materials. One example is the use of photonic crystals to improve solar energy harvesting in photoelectrochemical solar cells. Here, we describe the optical monitoring synthesis of macroporous materials, with inverse opal topology, made of transition metal and rare-earth oxide nanoparticles. Through the optical properties we can obtain information concerning both infiltration and over layer growth. Finally, we report on the efficiency improvement of photoelectrochemical cells when titania inverse opal topology is used.     

Luminescence of charge transfer sensitizers anchored to metal oxide nanoparticles

The photoluminescence (PL) properties of inorganic charge transfer sensitizers anchored to nanometer sized metal oxide particles are presented. The charge transfer sensitizers are inorganic coordination compounds such as ruthenium tribipyridine, Ru(bpy)²⁺₃, which have long lived metal-to-ligand charge transfer (MLCT) excited states. The metal oxides are insulators or semiconductor materials in the form of powders, colloidal solutions, and porous nanocrystalline films. Time resolved PL decays from this and related sensitizers anchored to metal oxide surfaces are highly non-exponential. The MLCT excited states are quenched on semiconducting metal oxide particles by an apparent electron transfer mechanism. With some assumptions electron transfer rates from the MLCT excited states to the nanostructured surface are calculated. The PL properties of sensitizers bound to porous nanocrystalline TiO₂ films can be controlled electrochemically.     

Strain Directed Assembly of Nanoparticle Arrays Within a Semiconductor

The use of strain to direct the assembly of nanoparticle arrays in a semiconductor is investigated experimentally and theoretically. The process uses crystal strain produced by a surface structure and variations in layer composition to guide the formation of arsenic precipitates in a GaAs-based structure grown at low temperature by molecular beam epitaxy. Remarkable patterning effects, including the formation of single and double one-dimensional arrays with completely clear fields are achieved for particles in the 10-nm size regime at a depth of about 50-nm from the semiconductor surface. Experimental results on the time dependence of the strain patterning indicates that strain controls the late stage of the coarsening process, rather than the precipitate nucleation. Comparison of the observed particle distributions with theoretical calculations of the stress and strain distributions reveals that the precipitates form in regions of maximum strain energy, rather than near extremum points of hydrostatic stress or dilatation strain. It is therefore concluded that the patterning results from modulus differences between the particle and matrix materials rather than from other strain related effects. The results presented here should be useful for extending strain directed assembly to other materials systems and to other configurations of particles.     

Influence of annealing conditions on the properties of reinforced silver-embedded silica matrix from the cheap silica source

The influence of annealing conditions on the properties of reinforced silver-embedded silica matrix was systematically investigated in the present study. The samples were prepared via a recently reported method using sodium silicate as a silica precursor. Aluminium ions were used to reinforce and improve the chemical durability of silver-embedded silica; and the mole ratio of the precursors was fixed at Al/Ag = 1. The properties of the final product were examined in relation to its counterparts; namely pure silica, aluminium-embedded silica (without silver), and silver doped silica (without aluminium). The materials were heat treated at the range of 600-1000 °C under the constant supply of argon (inert atmosphere). The properties of the final product were compared with those of the previously reported materials prepared via the same method but calcined in air. The current material was found to have pure silver nanoparticles (without AgCl nanoparticles) while the previous material had both silver and AgCl nanoparticles. The results demonstrate that materials with more desirable properties can be obtained by this newly developed technique while utilizing sodium silicate, which is relatively cheap, as a silica precursor. This may significantly boost the industrial production of the silver-embedded silicas for various applications.     

Characterization of nanoparticles of lidocaine in w/o micro emulsions using small-angle neutron scattering and dynamic light scattering

Microemulsions (MEs) are of special interest because a variety of reactants can be introduced into the nanometer-sized aqueous domains, leading to materials with controlled size and shape [1,2]. In the past few years, significant research has been conducted in the reverse ME-mediated synthesis of organic nanoparticles [3,4]. In this study, a w/o ME medium was employed for the synthesis of lidocaine by direct precipitation in w/o microemulsion systems: water/isopropylpalmitat/Tween80/Span80. The particle size as well as the location of nanoparticles in the ME droplet were characterized by means of dynamic light scattering (DLS) and small angle neutron scattering (SANS). It is observed that lidocaine precipitated in the aqueous cores because of its insolubility in water. Hydrodynamic radius and gyration radius of microemulsion droplets were estimated as ∼15 nm and ∼4.50 nm from DLS and SANS respectively. Furthermore, different size parameters obtained by DLS and SANS experiments were compared     

核壳结构磁性复合纳米材料的可控合成与性能

具有核/壳结构的磁性复合纳米材料是十分重要的功能材料,其综合物性受材料微结构的影响,而这很大程度上又取决于复合体系的可控合成.本文综述了近二十年来有关核/壳磁性复合纳米材料的制备、表征及性能研究方面的进展,讨论的体系主要有：铁氧体基永磁/软磁（反铁磁）复合纳米材料、非磁性体包覆磁性核而成的复合纳米材料、用磁性颗粒催化合成的碳基复合纳米材料、基于交换偏置效应而设计的复合纳米材料、核-壳同轴结构的一维复合纳米材料和核/壳/壳三元结构的磁性复合纳米材料等.构建复合体系的组分包括M型永磁铁氧体、3d过渡金属（及其合金、氧化物、碳化物）、多铁化合物、非磁性体（比如绝缘体、半导体、有机分子）和碳材料等,着重分析了复合纳米材料的热稳定性、光致发光性能、光电催化能力、电化学特性、微波吸收性能、磁电阻效应、永磁体性能、高频软磁特性、交换偏置效应及其相关现象.最后,对核/壳结构磁性复合纳米材料的未来发展趋势进行了展望,并在基础研究和改性应用方面提出了一些建议.     

纳米Ag颗粒表面等离子激元对上转换材料光致发光性能影响的研究

本文采用共烧结工艺将纳米Ag颗粒引入Yb³⁺, Er³⁺共掺的NaYF₄上转换材料中, 利用X射线衍射及扫描电子显微镜技术对制备的NaYF₄材料进行结构特性和表面形貌的表征, 通过吸收谱及荧光光谱测试技术对NaYF₄材料光吸收及光发射特性进行表征. 通过对纳米Ag颗粒引入量的优化, 获得了Yb³⁺, Er³⁺共掺的NaYF₄上转换材料荧光发射峰的增强, 300—800 nm全光谱范围内增益达28%, 在544 nm处获得最大增益55%, 具有显著的荧光增强效果. 同时分析了不同数量纳米Ag颗粒的引入对NaYF₄材料吸收谱及光致发光特性影响, 指出了表面等离子激元的光猝灭及共振吸收增强作用机理.     

Two‐Dimensionally Ordered Plasmonic and Magnetic Nanostructures on Transferable Electron‐Transparent Substrates

Discovery of new plasmonic behaviors from nanostructured materials can be greatly accelerated by the ability to prepare and characterize their near‐field behaviors with high resolution in a rapid manner. Here, an efficient and cost‐effective way is reported to make 2D periodic nanostructures on electron‐transparent substrates for rapid characterization by transmission electron microscopy. By combining nanosphere lithography with a substrate float‐off technique, large areas of electron‐transparent periodic nanostructures can be achieved. For this study, the synthesis of plasmonic nanostructures of Ag, magnetic nanostructures of Co, and bimetallic nanostructures of Ag–Co are investigated. Characterization of the materials by a combination of transmission electron microscopy, far‐field optical spectroscopy, and magnetization measurements reveals that this new approach can yield useful nanostructures on transparent, flexible, and transferable substrates with desirable plasmonic and/or magnetic properties.