由有机和无机金属前躯体自蔓延高温合成碳包覆磁纳米粒子(英文)

介绍了一项由自蔓延高温合成(SHS)碳包覆磁纳米粒子的系统研究。采用还原剂NaN3和三种不同氧化剂-聚四氟乙烯、六氯乙烷和六氯苯,实施了SHS制备。研究了金属前躯体(Fe(CO)5或K3[Fe(CN)6])对产物的得率、反应热、形貌、结构和磁性能的影响。结果表明:有机铁前躯体和C2Cl6氧化剂反应体系可获得磁性最佳、得率最高的产物。     

Role of organic molecules on upconversion luminescence of LaF3 nanoparticles

Yb and Er codoped LaF₃ nanocrystals were synthesized and studied. The upconversion luminescence properties of nanocrystals capped with different ligands are mainly dependent on the ligands, especially for the red emission which is sensitive to the nonradiative relaxation. The chelation between the ligands and rare earth ions can affect the morphology and fluorescent properties of samples. The chelating ligands will reduce the nonradiative quenching by isolating the RE ions from surrounding environment. So the upconversion luminescence properties of the samples vary correspondingly.     

磁性金属合金纳米粒子的合成与自组装

介绍了用高温液相法合成FePt、CoPt、FeCoPt和FeCoAg等磁性纳米粒子及其自组装的原理和方法，讨论了这些纳米粒子所具有的优异性能，并且指出了它们的最新应用。     

The role of organic molecules in molecular sieve synthesis

During the last 15 years, organic quaternary species, ions and amines, have been extensively employed as ‘templating’ additives in both aluminosilicate and aluminophosphate molecular sieve syntheses. A ‘template theory’ was evolved to explain the structure-directing effect of these organic species. The charge distribution and the size and geometric shape of a template are believed to be the causes for structure-directing. Meanwhile, data available in the literature also strongly suggest that gel chemistry, i.e. hydroxyl ion concentration, Si0₂/Al₂O₃ ratio, temperature, etc., is extremely important. The basic questions to be answered by the ‘template theory’ are: (1) How can one template give rise to so many different structures? (2) How can so many templates, differing in size and shape, all direct the same structure? (3) On the other hand, why do certain structures not form in the absence of a specific template molecule?In this article we intend to carefully review much of the synthesis data available in the literature and to examine the importance of the basic gel chemistry as well as of the templating effect. Also, we want to explore the close relationship of these two effects in molecular sieve synthesis.Based on the data reviewed, we propose that during the hydrothermal synthesis of molecular sieves, both gel chemistry and template species can play important roles in the formation of a specific structure, but that templating becomes operative only in the environment of the right ‘gel chemistry’.     

Bio-inspired strategy for on-surface synthesis of silver nanoparticles for metal/organic hybrid nanomaterials and LDI-MS substrates

A strategy for the on-surface synthesis of silver nanoparticles (AgNPs) on a variety of two-?to three-dimensional material surfaces, utilizing polydopamine, an emerging surface modifying agent, is reported in this paper. This material-independent platform for AgNP synthesis is useful for fabricating organic/inorganic hybrid nanomaterials and for preparing substrates for laser desorption-ionization time-of-flight mass spectrometry (LDI-ToF MS).     

Role of pH in the green synthesis of silver nanoparticles

The role of pH in the green synthesis of silver nanoparticles (AgNPs) is investigated. For the reduction synthesis of AgNPs we use silver nitrate, glucose, sodium hydroxide and starch respectively to serve as precursor, reducing agent, accelerator and stabilizer. The effect of NaOH addition on the nature of AgNPs is systematically studied. Two reaction pathways are proposed to explain the formation of AgNPs, keeping in view the pH changes that occur on addition of different amounts of NaOH. The aqueous sol of AgNPs prepared at different pH values display different surface plasmon resonance (SPR) behavior. This is explained in terms of size and size distribution of AgNPs.     

Deposition and STM characterization of luminescent organic molecules on metal substrates

The porphyrin-based molecules including H₂TBPP, ZnTBPP and P_tTBPP as well as the perinone derivatives (PD) molecules were deposited on Au(100), Au(111) and Cu(100) substrates in the form of single molecule, molecular line, submonolayer, monolayer and multilayer. The features of the performed molecular nanostructures were characterized by an ultrahigh vacuum scanning tunneling microscopy (STM) at room temperature. The observed molecular topographies matched very well with the molecule structures in spite of the fact that the molecular adsorption states were influenced by different metal surface. STM-induced photon emission was generated from the surface of H₂TBPP multilayer structures on Au(100) in tunneling junction when the applied bias exceeds the “turn-on” voltages ∼− 1.6 V or + 1.3 V at 0.5 nA.     

MOFs材料合成及其对有机气体吸附研究进展

讨论了金属有机骨架(MOFs)材料的不同合成方法,并结合国内外研究现状分别分析了IRMOFs、MILs、ZIFs和PCN等系列MOFs材料对有机气体吸附的研究进展,比较其性能及分析研究中的难点,对MOFs材料在有机气体吸附领域的应用进行了展望。     

Role of metal and dielectric nanoparticles in the performance enhancement of silicon solar cells

The suitability of using spherical metal and dielectric nanoparticles on the top of a silicon solar cell has been investigated. An enhancement index factor (EIF) for each wavelength of light and an averaged EIF for the AM 1.5 solar spectrum, weighted by the photon flux, has been introduced. These factors estimate the effect of the nanoparticles in improving the performance of the solar cells, considering the absorption loss due to joule heating, fraction of radiation scattered into the substrate and the front scattered radiation pattern. A systematic comparison between silver and dielectric nanoparticles (silica, silicon nitride, titanium dioxide) shows that titanium dioxide and silicon nitride nano particles of sizes ≥100?nm exhibit larger enhancements compared to that of silver nanoparticles of similar sizes. Further, as the dielectric constant of the dielectric nanoparticles increases, the optimal particle size corresponding to maximal enhancement shifts towards lower value. At optimal particle sizes, the enhancement is 1.5–2 times greater than that due to silver nanoparticles.     

Complexes of cobalt nanoparticles and polyfunctional curcumin as antimicrobial agents

Although antimicrobials like penicillin and tetracycline have been documented to be most popular antimicrobials, micro-organisms, especially bacteria, are becoming resistant to more and more antimicrobial agents and hence the main future research in antimicrobial therapy is to develop novel materials which could work as effective antimicrobials. In this context, using direct reduction method, 10 nm Co nanoparticles have been synthesized and further functionalized with curcumin. The characterization showed FCC structured Co nanoparticles to be electrostatically bound to curcumin using the hydroxyl linkage, retaining the magnetic moment of Co as well as the diaryl heptanoid chromophore group of curcumin with the loading percentage of~ 89%. These samples when subjected to Escherichia coli, gram negative bacterium, the antimicrobial activity of Co:curcumin was found to be much enhanced as compared to only Co and only curcumin. The results have been correlated to the mechanism in presence of moisture, which possibly suspends the Co:curcumin complex in the medium, which, due to intimate contact between the biocidal agent and the microorganism, renders the microbial agent ineffective. The synthesized system exhibited a combination of the ability of curcumin to penetrate the cell barrier and render antimicrobial action along with the chelating capacity of Co:curcumin complex. In the same way that strong metal-ligand bonds are vital for the efficiency of metal chelators of toxic metals, these strongly bound metal complexes may prove to be better antimicrobial agents, binding them to the bacterial walls.     

Reliable synthesis of bismuth nanoparticles for heavy metal detection

A reliable and facile pathway is described here for preparing high-quality bismuth nanoparticles. Combined with hydrothermal method and confined growing effect of polymer, bismuth nanoparticles with uniform size and shape were obtained with remarkable productivity. The nanoparticles is proved to be pure Rhombohedral structure Bi crystals with R-3m space group and the diameter of the nanoparticles is about 80 nm with a quite narrow particle size distribution. Those bismuth nanoparticles were predicted to grow from a rolling process by sheet-like Bi nanocrystal intermediates. The obtained bismuth nanoparticles were used to prepare modified electrode for the detection of Cd²⁺ and Pb²⁺ in water solution by stripping analysis. Compared with naked glassy carbon electrodes, the modified electrode showed two obvious responses at −0.85 V and −0.62 V, corresponding to the reduction process of Pb²⁺ and Cd²⁺ and this well-resolved stripping response can be observed when the concentration is as low as 10 μg/L, indicating potential application in electroanalysis for environmental inspection.     

Directing the assembly of charged organic molecules by a hydrophilic-hydrophobic nanostructured monolayer at electrified interfaces

Nanostructured monolayers of water-insoluble amphiphilic 5-alkoxy-isophthalic acids direct the reversible self-assembly of water-soluble positively and negatively charged molecules under electrochemical control. The surface potential is in control of the monolayer composition, structure, and guest dynamics.     

In-situ synthesis of gold nanoparticles in nitrogen-doped titania nanosheets via layer-by-layer assembly method

Self-assembled multilayer films of nitrogen-doped exfoliated titania nanosheets and Au nanoparticles (NP) were fabricated via layer-by-layer assembly method followed by solar irradiation treatment. Au NP were found to form by in-situ reduction and thus disperse homogeneously between nitrogen-doped titania nanosheet galleries and the composite films of disordered structure, as confirmed by transmission electron microscope and X-ray diffractometer. Ultraviolet-visible absorption spectra in the multilayer buildup process indicated that plasmon resonance of the multilayer films was enhanced and red-shifted due to the changes of surrounding medium. It is found that nearly equal amounts of nanosheets were assembled and golds were reduced in each deposition cycle. X-ray photoelectron spectroscopy observation revealed that the interaction between the two components affects the distribution of electrons of Au, which causes the negative shift of the binding energy of Au NP. Compared with pure nitrogen-doped (N-doped) titania nanosheets, the higher hydroxyl density on the surface of such multilayer films was confirmed to be beneficial to efficiently separating the photogenerated electrons and holes, and as a result enhancing their photocatalytic activities.     

Self-assembly of organic acid molecules on the metal oxide surface of a cupronickel alloy

Corrosion of the metal oxide surface of cupronickel (CuNi) alloys is a problem in applications such as household water pipes, industrial pipelines, and marine vessels. On other substrates, thin films have been used as barriers to corrosion. Here, the formation of self-assembled monolayers (SAMs) on the CuNi metal oxide surface has been investigated. Stable, well-ordered SAMs of octadecylphosphonic acid (ODPA) and 16-phosphonohexadecanoic acid (COOH-PA) were formed on the metal oxide surface of CuNi foils (55% Cu/45% Ni) using a solution deposition method. The ODPA modified surfaces could be used to provide a non-reactive barrier that inhibits corrosion of the CuNi metal oxide surface. Meanwhile, COOH-PA films could be used for further surface reactions such as surface initiated polymerization, in which polymer coatings are grown directly from a well-ordered film. Film-modified surfaces were characterized using diffuse reflectance infrared Fourier transform spectroscopy, contact angle analysis, and matrix assisted laser desorption ionization time of flight mass spectrometry. The ability of the films to inhibit corrosion by limiting oxidation of the CuNi surface was assessed using cyclic voltammetry.     

Controllable synthesis of uncapped metal nanoparticle assembly at the air–water interface

A two-dimensional self-assembly of uncapped Ag nanoparticles was prepared at the air–water interface. In the experiment, ethanol was added into the Ag-based colloid to reduce the surface charge density on the nanoparticles and the air–water interfacial energy, leading to the nanoparticles adsorption and assembling at the air–water interface. It was found that the array structure was controllable. The ordered nanoparticle array could be changed to a fractal structure by varying gradually the amount of the added ethanol. Moreover, it was demonstrated that the assembly was sensitive to the surface charge density on the particles, the Debye length in the colloid and the interfacial tension between nanoparticle/water (air).     

In situ synthesis of metal nanoparticles in polymer matrix and their optical limiting applications

We present an overview of the simple and environmentally benign protocol we have developed recently, for the in situ generation of metal nanoparticles inside polymer films by mild thermal annealing, leading to free-standing as well as supported thin films of nanoparticle-embedded polymer. The fabrication chemistry is discussed and spectroscopic/microscopic characterizations of silver and gold nanoparticles in poly(vinyl alcohol) film are presented. Optical limiting characteristics of the silver-polymer system are investigated in detail and preliminary results for the gold-polymer system are reported.