Designed synthesis of cobalt and its alloys by polyol process

The role of polyol, precursor and reaction promoting agents in the synthesis of metal and alloy nanoparticles using polyol process has been investigated by analyzing the reaction steps involved in the synthesis of cobalt in Co ion-polyol-[OH⁻] ion system in detail. The reducing potential of polyols and the easiness with which any metal salt can react to form reducible complexes has been evaluated using the orbital molecular theory and the results were experimentally verified. The reduction limit of polyol and their extension using reaction promoting agents such as [OH⁻] ions is also explained. The reduction of cobalt is preceded by various reaction stages of complex/compound formation, which has been fully identified. Furthermore, the reducing form of cobalt has been identified as either cobalt alkoxide or cobalt hydroxide. The results confirmed that the complex forming reactions that take place prior to the formation of the precursor, which finally get reduced to metal, play a decisive role in determining the physical properties of the nanoparticles. The approach can be extended to reduce any metals or alloys using polyol process.     

Hyperbranched polyglycidol assisted green synthetic protocols for the preparation of multifunctional metal nanoparticles

Biocompatible hyperbranched polyglycidol (HBP) has been demonstrated to be an effective reducing and stabilizing agent for the synthesis of highly water-soluble monometallic (Au, Ag, Pt, Pd, and Ru) and bimetallic (Au/Pt, Au/Pd, and Au/Ru) nanoparticles (NPs), which provides a general and green protocol to fabricate metal NPs. The HBP-assisted reduction of metal ions follows an analogous polyol process. The reduction reaction rate increases sharply by increasing the temperature and the molecular weight of HBP. The size of NPs is controllable simply by changing the concentration of the metal precursor. High molecular weight HBP is favorable for the formation of NPs with uniform size and improved stability. By utilizing hydroxyl groups in the HBP-passivation layer of Au NPs, TiO(2)/Au, GeO(2)/Au, and SiO(2)/Au nanohybrids are also fabricated via sol-gel processes, which sets a typical example for the creation of versatile metal NPs/inorganic oxide hybrids based on the as-prepared multifunctional NPs.     

Sound absorption behavior of flexible polyurethane foams including high molecular‐weight copolymer polyol

Noise pollution is an important issue for automotive industries. In this article, the high molecular‐weight copolymer polyol is blended in the polyol mixtures for fabricating flexible polyurethane foams to improve sound absorption efficiency. Changes of cavity size and material density of the foams are negligible by inclusion of copolymer polyol in the polyol mixture, but the closed pore ratio and specific airflow resistance increase for the copolymer polyol content higher than 20 wt% because of changes of phase separation behavior from drainage flow rate reduction that occurs with increased viscosity. Sound absorption efficiency increases with increasing copolymer polyol content up to 20 wt%, but it decreases beyond this point. The sound absorption property mainly results from the closed pore ratio, not from the cavity size. The compression strength increases with increasing copolymer polyol contents by increased amount of hard segments. Therefore, an optimum amount of high molecular‐weight polyol is recommended for enhanced sound absorption property.     

壳聚糖纳米粒子荧光探针的制备和表征

通过低分子量的壳聚糖(LCS)聚阳离子与三聚磷酸钠(TPP)的静电作用制备纳米级壳聚糖微球,并利用壳聚糖链上丰富的氨基与荧光素异硫氰酸酯(FITC)反应从而制备纳米壳聚糖微球荧光探针(NFCS)。结果表明,当壳聚糖分子量为60000,LCS与TPP的质量比为6∶1时,可得到粒度均一的球形纳米粒子,平均粒径为40±3 nm。荧光倒置显微镜观察证实FITC结合到壳聚糖微球上。荧光光谱分析显示NFCS的最大激发波长、最大发射波长与游离态FITC无显著差异。光漂白实验证实NFCS的稳定性比游离态FITC有显著提高。     

Synthesis,thermal properties and crystalline morphology of poly(trimethylene terephthalate)/ZnO nanocomposites prepared by dual in situ polymerization

Poly(trimethylene terephthalate)/ZnO nanocomposites were successfully prepared by dual in situ polymerization. Firstly, ZnO nanoparticles were synthesized by a simple polyol method using 1,3‐propanediol (PDO) as solvent and stabilizer. Then, PTT/ZnO nanocomposites were prepared by in situ polymerization. The results of Fourier transform infrared spectra showed that PTT molecular chains were grafted to the surface of ZnO nanoparticles. The results of ¹H NMR spectra confirmed that propyl ester molecules (as reaction product) were incorporated into PTT molecular chains. It was found that the intrinsic viscosity and molecular weight of synthesized PTT decreased with the addition of ZnO nanoparticles and the incorporation of propyl ester molecules. TEM results showed that ZnO nanoparticles with particle size of 20 ~ 30 nm were well dispersed and fully distributed in the polymer matrix. Besides, the melting temperatures and crystallization temperature decreased gradually and then increased slightly with the increasing loading of ZnO nanoparticles. Because of the strong interaction between ZnO nanoparticles and PTT matrix, the thermal stability of PTT/ZnO nanocomposites was improved. Interestingly, the results of Polarized Optical Microscopy showed that banded spherulites morphology can be observed in all PTT/ZnO nanocomposite samples. However, at higher loading of ZnO nanoparticles, band spacing became larger and was finally disturbed. Copyright © 2016 John Wiley & Sons, Ltd.     

表面富Pd的Ni-Pd/C催化剂的合成及电化学性质研究

应用改进的多元醇法,分步还原制备表面富Pd的N iPd双元合金催化剂.研究表明:由于Pd较容易还原成核,且与N i的合金化程度低,Pd难以在N i颗粒表面实现单层包覆形成N i@Pd核壳结构,而是近似以单相的低合金化形式存在于N i颗粒表面,即形成N i@Pd(N i)的结构.与Pd/C相比,制备的N i@Pd(N i)/C催化剂,其Pd表面的氢吸附峰与吸收峰分辨清晰,含氧化物的脱附峰向正电势移动,氧还原活性显著提高.另外,N i的存在使Pd的抗甲醇性能明显增强,从而有望作为直接甲醇燃料电池的阴极催化剂.     

Effect of colloidal nanocatalysis on the metallic nanoparticle shape: the Suzuki reaction

Dominantly tetrahedral shaped poly(vinylpyrrolidone)-platinum (PVP-Pt) nanoparticles are shown to catalyze the Suzuki reaction between phenylboronic acid and iodobenzene but are not as active as the spherical palladium nanoparticles studied previously. The dominantly tetrahedral PVP-Pt nanoparticles (55 +/- 4% regular tetrahedral, 22 +/- 2% distorted tetrahedral, and 23 +/- 2% spherical nanoparticles) are synthesized by using the hydrogen reduction method. The transmission electron microscopy (TEM) results show that a transformation of shape from tetrahedral to spherical Pt nanoparticles takes place 3 h into the first cycle of the reaction. After the first cycle, the spherical nanoparticles have a similar size distribution to that of the tetrahedral nanoparticles before the reaction and the observed shape distribution is 18 +/-6% regular tetrahedral, 28 +/- 5% distorted tetrahedral, and 54 +/- 5% spherical nanoparticles. After the second cycle of the Suzuki reaction, the shape distribution is 13 +/- 5% regular tetrahedral, 24 +/- 5% distorted tetrahedral, and 63 +/- 7% spherical nanoparticles. After the second cycle, the transformed spherical nanoparticles continue to grow, and this could be due to the strong capping action of the higher molecular weight PVP (M(w) = 360 000), which makes the nanoparticles more resistant to aggregation and precipitation, unlike the Pd nanoparticles capped with the lower molecular weight PVP (M(w) = 40 000) used previously. The transformation in shape also occurs when the nanoparticles are refluxed in the presence of the solvent, sodium acetate, and iodobenzene and results in spherical nanoparticles with a similar size distribution to that of the tetrahedral nanoparticles before any perturbations. However, in the presence of phenylboronic acid, the regular tetrahedral nanoparticles remain dominant (51 +/- 6%) and maintain their size. These results support our previous studies in which we proposed that phenylboronic acid binds to the nanoparticle surface and thus acts as a capping agent for the particle and reacts with the iodobenzene. Recycling the nanoparticles results in a drastic reduction of the catalytic activity, and this must be due to the transformation of shape from the dominantly tetrahedral to the larger dominantly spherical nanoparticles. This also supports results in the literature that show that spherical platinum nanoparticles do not catalyze this reaction.     

One-pot synthesis of large FePt nanoparticles from metal salts and their thermal stability

One-pot synthesis of FePt nanoparticles larger than 5 nm with controlled composition has been developed by the polyol reduction of platinum acetylacetonate and iron acetylacetonate in excess ligands. The obtained large FePt nanoparticles (6.1 +/- 0.6 nm Fe36Pt64, 5.8 +/- 0.7 nm Fe44Pt56, and 5.1 +/- 0.7 nm Fe49Pt51 nanoparticles) were thermally more stable than the small ones and were hard to coalesce in the in-plane direction for their 2D superlattice.     

Nickel nanoparticles obtained by a modified polyol process: synthesis, characterization, and magnetic properties

The synthesis of nickel nanoparticles using poly(N-vinilpyrrolidone) (PVP) as protective agent was studied. The nanoparticles were prepared in air according to a modified polyol route, using nickel chloride as precursor and sodium borohydride as reducing agent. Samples with different nickel/PVP ratio were obtained. The X-ray diffraction and transmission electron microscopy (TEM) measurements indicate the occurrence of face-centered cubic metallic nickel nanoparticles with a medium diameter of 3.8 nm and good size dispersion. Fourier transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) data show an effective interaction between the nickel nanoparticles surface and the carboxyl oxygen atoms of PVP. Magnetic measurements show single-domain nonideal superparamagnetism behavior due to dipolar magnetic coupling between particles.     

Hydrophilic polymer supported nanoparticles prepared from samarium trichloride and lanthanum trichloride in liquid-phase

Nanoparticles were obtained by the reaction of SmCl₃·6H₂O with sodium borohydride (NaBH₄) in the presence of sodium polyacrylate (PAA) with average molecular weight of 5,100 as a capping polymer. The resulting colloidal solution was placed on a Cu grid and characterized by transmission electron microscope (TEM) measurement, which clearly indicated the generation of nanoparticles. The reaction of LaCl₃ with NaBH₄ in the presence of PAA led to preparation of lanthanum nanoparticles, similarly as samarium nanoparticles.     

Ru/ZrO_2催化剂在苯部分加氢反应中的粒径效应

采用多元醇还原法将2.4~5.4 nm范围内粒径均一、尺寸可控的Ru纳米粒子负载在ZrO2上,研究了Ru的粒径对Ru/ZrO2催化剂上苯部分加氢性能的影响.采用紫外-可见吸收光谱(UV-Vis)、N2物理吸附、H2化学吸附、H2-程序升温脱附(H2-TPD)、粉末X射线衍射(XRD)、透射电子显微镜(TEM)和X射线光电子能谱(XPS)等手段对催化剂进行了系统的表征.研究表明,用于还原的醇的种类及添加剂乙酸钠的浓度对Ru粒径有显著影响.在苯部分加氢反应中,Ru/ZrO2催化剂有明显的粒径效应.随着Ru粒径的增大,苯的转换频率(TOF)提高,环己烯初始选择性(S0)则呈火山型变化趋势,选择性最高时的Ru粒径为4.4 nm.1,2-丙二醇还原得到的Ru/ZrO2催化剂上S0及环己烯得率最高,分别可达82%和39%.结合催化剂的表征和加氢结果,讨论了Ru粒径影响苯部分加氢活性和选择性的原因.     

Phosphonioalkylthiosulfate zwitterions--new masked thiol ligands for the formation of cationic functionalised gold nanoparticles

We report the synthesis and structural characterisation of a new family of stable phosphonioalkylthiosulfate zwitterions, R3P+ (CH2)nS2O3- (R = Ph or Bu, n = 3,4,6, 8 or 10) which behave as cationic masked thiolate ligands with applications in the functionalisation of gold nanoparticles, having potential as new diagnostic biorecognition systems. The ligands were prepared by treatment of omega-bromoalkylphosphonium salts with sodium thiosulfate. The crystal and molecular structures of the zwitterions (R = Ph, n = 3) and (R = Bu, n = 3) were determined. A series of phosphonioalkanethiolate-capped gold nanoparticles dispersed in water was prepared by borohydride reduction of potassium tetrachloroaurate in the presence of the zwitterions in a dichloromethane-water system. UV-visible spectroscopy and scanning transmission electron-microscopy indicated that capped nanoparticles of ca. 5 nm diameter were present.     

银纳米微球和银纳米棒自组装膜的制备及SERS研究

采用硼氢化钠还原硝酸银,用振荡器在不同转速下振荡得到单分散的银纳米微球和银纳米棒,再将银纳米微球及银纳米棒自组装于被3-氨丙基-三甲氧基硅烷(APTMS)修饰的玻璃基片上,制得了具有表面增强拉曼(SERS)活性的基底,分别以罗丹明6G(R6G)和罗丹明B(RB)为探针分子对这两种基底进行SERS活性检测,结果发现这两种基底均为较理想的SERS衬底。     

Gel filtration study of mushroom proteins

Summary Proteins from six edible wild mushrooms were extracted by sodium chloride, ethanol or sodium hydroxide and analysed by gel filtration on Sephacryl S-200. Analysis of the whole extracts and the separated proteins of different molecular weight as well as the determination of their amino acid content demonstrated that the soluble mushroom proteins are dimers, trimers and decamers of the simple main protein (polypeptide) with an approximate molecular weight of 15,000. The polymers were stabilized by both covalent and non-covalent forces as demonstrated by gel filtration in acetic acid before and after reduction of the covalent bonds.     

Ultrasound-assisted polyol method for the preparation of SBA-15-supported ruthenium nanoparticles and the study of their catalytic activity on the partial oxidation of methane

Metallic Ru nanoparticles have been successfully produced and incorporated into the pores of SBA-15 in situ employing a simple ultrasound-assisted polyol method. The product has been confirmed by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy, where ultrasound provides both the energy for the reduction of the Ru(III) ion and the driving force for the loading of the Ru(0) nanoparticles into the SBA-15 pores. An ultrasound-assisted insertion mechanism has been proposed based on the microjets and shake-wave effect of the collapsed bubbles. The catalytic properties of the SBA-15-supported Ru nanoparticles have been tested by the partial oxidization of methane and show very high activity and high CO selectivity.     

纳米碳纤维负载钯催化剂在Heck反应中的应用——载体相互作用的影响

使用多元醇还原法制备了均匀分散的钯纳米颗粒.将钯纳米颗粒负载于板式、鱼骨式和管式纳米碳纤维,得到稳定、可重复使用的非均相催化剂.实验结果表明,钯纳米胶粒同载体之间的电位差对钯在载体上的负载量、粒子大小以及Heck反应中钯的溶失量有很大的影响.在制备过程中,增加钯纳米胶粒同纳米碳纤维表面的电位差能够大大降低钯在Heck反应中的流失.催化剂的反应活性随钯粒子的增大而降低.     

Use of Natural Monomer in the Synthesis of Nano- and Microparticles of Polyurethane by Suspension-Polyaddition Technique

Summary: Polyurethane nano- and microparticles were synthesized by suspension-polyaddition technique, using aqueous polymerization medium. Castor oil, a vegetable triglyceride possessing hydroxyl groups was used as natural polyol and methylene diphenyl diisocyanate (MDI) as isocyanate. The levofloxacin, an antibacterial drug was used as model drug to measure the particles encapsulation efficiency. The effect of the addition of a second polyol, the poly(ethylene glycol) (PEG), and the stirring rate on the mean diameter and morphology of particles was also investigated. The poly(ethylene glycol) has an important effect in the reduction of particles size and their porosity. On the other hand, the poly(ethylene glycol) reduced the yield of encapsulation from 70% for the formulation without PEG to 20% for formulations with PEG. FTIR analysis confirmed the polyurethane formation. Dynamic light scattering study, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to determine the nanoparticles size and shape. Spectrofluorimetric analysis was used to detect the levofloxacin.     

Microwave synthesis of core-shell gold/palladium bimetallic nanoparticles

The microwave-assisted polyol reduction method was applied to the synthesis of core-shell gold/palladium bimetallic nanoparticles by the simultaneous reduction of the AuIII and PdII ions. The thickness of the palladium shell was calculated to be approximately 3 nm, and the gold core diameter is 9 nm. The structure and composition of the bimetallic particles were characterized by high-resolution transmission electron microscopy equipped with a nanoarea energy-dispersive X-ray spectroscopy attachment, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy.     

Synthesis and investigation of dual pH‐ and temperature‐responsive behaviour of poly[2‐(dimethylamino)ethyl methacrylate]‐grafted gold nanoparticles

Gold nanoparticles (AuNPs) were synthesized by reduction of chloroauric acid (HAuCl₄) aqueous solution with hydrazine monohydrate. The AuNPs were immediately treated with cysteamine to obtain amine‐functionalized nanoparticles (Au‐NH₂). The reaction of Au‐NH₂ with epichlorohydrin and subsequent treatment with sodium hydroxide gave epoxidized AuNPs (Au‐EP). Then, thiol‐capped AuNPs (Au‐SH) were synthesized by reaction of Au‐EP with cysteamine. A ‘grafting to’ approach was utilized to graft bromine‐terminated poly(N ,N ′‐dimethylaminoethyl methacrylate), synthesized via aqueous atom transfer radical polymerization, with various molecular weights (6280, 25 800, 64 200 and 87 600 g mol⁻¹) onto Au‐SH to obtain Au‐P1, Au‐P2, Au‐P3 and Au‐P4 samples, respectively. All samples were exposed to temperature and pH variations, and Z‐average diameter was monitored using dynamic light scattering. According to the results, polymer‐grafted nanoparticles collapsed at lower temperatures with increasing solution pH for all molecular weight ranges due to deprotonation of tertiary amine groups. However, higher molecular weight polymers were more sensitive to pH variation especially in alkaline media. Also, a high degree of agglomeration was observed for Au‐P4 nanoparticles in alkaline media on increasing the temperature to 55 and 65 °C.     

柠檬酸根辅助多元醇法制备直径和磁性可控的Fe_3O_4亚微球

以柠檬酸三钠作辅助剂,用多元醇溶剂热还原法制备了纳米晶粒和微球直径可控的、单分散的超顺磁Fe3O4亚微球.发现与铁原子有强亲和力的柠檬酸根能有效吸附在还原产生的初始Fe3O4纳米粒子表面,阻碍其晶粒生长和影响其静电排斥力的大小,从而能在较大范围内调控最终产物Fe3O4亚微球的直径和饱和磁化强度.改变柠檬酸根或铁盐浓度不但可以调控初始Fe3O4纳米粒子的粒径,而且可以在220-550nm范围内调控单分散Fe3O4亚微球的直径,从而得到粒径均一的超顺磁Fe3O4亚微球.