Mechanochemistry of Gaseous Reactants

In recent years, the application of mechanical energy to chemical systems has repeatedly proven beneficial to facilitate chemical transformations in various areas in chemistry. Today, a systematic body of evidence indicates that mechanochemistry holds great promise to become a game‐changer in chemical synthesis. Not only does mechanochemistry permit access to products that are inaccessible by established means (e.g. purely thermal activation), mechanochemical reactions often outperform their solution‐based counterparts in terms of sustainability. Most mechanochemical reactions carried out by ball milling techniques involve transformations of solids and liquids, but the number of mechanochemical reactions with gaseous reactants is increasing. The aim of this Minireview is to provide an overview of recent chemical reactions involving gaseous samples by ball milling techniques and to highlight advances in ball milling technology for the safe handling of gaseous reagents. Examples of reactions proceeding at the interface of solid–/liquid–/gas–gas systems that led to significant improvements in reactivity or selectivity will also be highlighted.     

Basic Physicochemical Properties of Polyethylene Glycol Coated Gold Nanoparticles that Determine Their Interaction with Cells

A homologous nanoparticle library was synthesized in which gold nanoparticles were coated with polyethylene glycol, whereby the diameter of the gold cores, as well as the thickness of the shell of polyethylene glycol, was varied. Basic physicochemical parameters of this two‐dimensional nanoparticle library, such as size, ζ‐potential, hydrophilicity, elasticity, and catalytic activity ,were determined. Cell uptake of selected nanoparticles with equal size yet varying thickness of the polymer shell and their effect on basic structural and functional cell parameters was determined. Data indicates that thinner, more hydrophilic coatings, combined with the partial functionalization with quaternary ammonium cations, result in a more efficient uptake, which relates to significant effects on structural and functional cell parameters.     

Graphene Supported Platinum Nanoparticles as Catalyst for Oxygen Reduction Reaction

Graphene supported Pt nanoparticles were fabricated via electrochemical reduction method and the application of them in oxygen reduction reaction was also investigated. The results of field emission scanning electron microscope(SEM), X-ray photoelectron spectroscopy(XPS) and Raman spectroscopy reveal that the interaction between Pt nanoparticles and graphene sheets can prevent graphene from agglomeration and improve the electronic conductivity of the composite. And the graphene supported Pt nanoparticles exhibit excellent electrocatalytic activity toward oxygen reduction reaction.     

Coating Platinum Nanoparticles with Methyl Radicals: Effects on Properties and Catalytic Implications

It was recently reported that the reaction of methyl radicals with Pt⁰ nanoparticles (NPs), prepared by the reduction of Pt(SO₄)₂ with NaBH₄, is fast and yields as the major product stable (Pt⁰‐NPs)?(CH₃)_n and as side products, in low yields, C₂H₆, C₂H₄, and some oligomers. We decided to study the effect of this coating on the properties of the Pt⁰‐NPs. The results show that the coating can cover up to 75 % of the surface Pt⁰ atoms. The rate constant of the reaction, k( ^. CH₃+Pt⁰‐NPs), decreases with the increase in the surface coverage, leading to competing reaction paths in the solution, which gradually become dominant, affecting the composition of the products. The methyl coating also affects the zeta potential, the UV spectra, and the electrocatalytic reduction of water in the presence of the NPs. Thus, the results suggest that binding alkyl radicals to Pt⁰ surfaces might poison the NPs catalytic activity. When the Pt⁰‐NPs are prepared by the reduction of a different precursor salt, PtCl₆^2?, nearly no C₂H₄ and oligomers are formed and the methyl coating covers a larger percentage of the surface Pt⁰ atoms. The difference is attributed to the morphology of the Pt⁰‐NPs: those prepared from Pt(SO₄)₂ are twinned nanocrystals, whereas those prepared from PtCl₆^2? consist mostly of single crystals. Thus, the results indicate that the side products, or most of them at least, are formed on the twinned Pt⁰ nanocrystal edges created between (111) facets. In addition, the results show that Pt⁰‐NPs react very differently compared with other noble metals, for example, Au⁰ and Ag⁰; this difference is attributed in part to the difference in the bond strength, (M⁰‐NP)?CH₃, and should be considered in heterogeneous catalytic processes involving alkyl radicals as intermediates.     

碳纳米管负载高分散Pt纳米颗粒的制备及表征

近年来,碳纳米管(CNTs)[1]作为新型催化剂载体方面的研究[2～11]受到了广泛关注。由于碳纳米管具有纳米级卷曲的表面,与石墨烯相比其表面π键发生变化,从而导致新的电子结构[12],因此碳纳米管负载的催化剂在涉及电子传输过程的催化过程中具有特别的吸引力。燃料电池电极催化剂就是其中典型的一类[13～15]。已有研究者选用碳纳米管作为载体,将Pt[16～19]、PtRu[20,21]等具有催化活性的贵金属或其合金负载到碳纳米管上,展现出了很好的电催化氧化活性。然而,到目前为止,制备用于燃料电池的具有均匀尺寸和分散性的负载型纳米催化剂仍然是一项…     

介孔碳负载铂催化剂的分散性和电催化活性

以介孔硅SBA-15为模板, 糠醇为碳源制备了高度有序的介孔碳(CMK-5), 并用微波法合成碳负载的铂纳米粒子的催化剂. 为改善铂微粒的分散性能, 在微波碳载过程中添加了适量的阳离子表面活性剂(CTAB). XRD和TEM测试结果表明, CTAB的加入改善了铂催化剂的分散性, 且使铂微粒的平均粒径降至2.9 nm左右. 循环伏安测试结果显示, 加入CTAB后所得Pt/CMK-5催化剂的电化学活性面积大于未加CTAB的以及商业Johnson Matthey公司的Pt/C催化剂的活性面积.     

Pt纳米颗粒在氮掺杂空心碳微球上的高分散负载及其氧还原性能

通过热解自聚合多巴胺法制备了氮掺杂空心碳微球(N-HCMS), 并采用微波辅助乙二醇还原方法把Pt纳米粒子负载于N-HCMS上制得了Pt/N-HCMS催化剂. 催化剂的表面形貌、晶体结构及其比表面积和孔径分布等分别采用扫描电子显微镜、透射电子显微镜、X射线衍射仪及比表面分析仪等进行表征. 采用循环伏安法和线性扫描伏安法研究了Pt/N-HCMS 催化剂在酸性条件下的电催化氧还原性能. Pt/N-HCMS 催化剂由于Pt纳米粒子的均匀分散、N-HCMS载体的快速电子传递及其独特的微孔和中空结构而具有很高的电催化氧还原活性, 其质量比活性是E-TEK Pt/C 催化剂的近两倍. Pt/N-HCMS 催化剂还具有优良的稳定性. 本工作对于开发高性能的燃料电池阴极催化剂具有重要意义.     

Interaction of Polystyrene Nanoparticles with Supported Lipid Bilayers: Impact of Nanoparticle Size and Protein Corona

Polystyrene is one of the most widely used plastics. This article reports on the interaction of 50 and 210 nm polystyrene nanoparticles (PSNPs) with human serum albumin (HSA) and transferrin (Tf), as well as their effect on supported lipid bilayers (SLBs), using experimental and theoretical approaches. Dynamic light scattering (DLS) and atomic force microscopy (AFM) measurements show that the increase in diameter for the PSNP-protein bioconjugates depends on nanoparticle size and type of proteins. The circular dichroism (CD) spectroscopy results demonstrate that the proteins preserve their structures when they interact with PSNPs at physiological temperatures. The quartz crystal microbalance (QCM) technique reveals that PSNPs and their bioconjugates show no strong interactions with SLBs. On the contrary, the molecular dynamics simulations (MDS) show that both proteins bind strongly to the lipid bilayer (SLBs) when compared to their binding to a polystyrene surface model. The interaction is strongly dependent on the protein and lipid bilayer composition. Both the PSNPs and their bioconjugates show no toxicity in human umbilical vein endothelial (HUVEC) cells; however, bare 210 nm PSNPs and 50 nm PSNP-Tf bioconjugates show an increase in reactive oxygen species production. This study may be relevant for assessing the impact of plastics on health.     

Facile Fabrication of Platinum Nanoparticles Supported on Nitrogen-doped Carbon Nanotubes and Their Catalytic Activity

A facile impregnation method under mild condition is designed for synthesis of highly dispersed Pt nanoparticles with a narrow size of 4-7 nm on nitrogen-doped carbon nanotubes （CNx）. CNx do not need any pre-surface modification due to the inherent chemical activity. The structure and nature of Pt/CNx were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy spectrum. All the experimental results revealed that the large amount of doped nitrogen atoms in CNx was virtually effective for capturing the Pt（IV） ions. The improved surface nitrogen functionalities and hydrophilicity contributed to the good dispersion and immobi- lization of Pt nanoparticles on the CNx surface. The Pt/CNx served as active and reusable catalysts in the hydrogenation of allyl alcohol. This could be attributed to high dispersion of Pt nanoparticles and stronger interaction between Pt and the supports, which prevented the Pt nanoparticles from aggregating into less active Pt black and from leaching as well.     

Magnetic Nanoparticles Supported Ionic Liquids Improve Firefly Luciferase Properties

Ionic liquids as neoteric solvents, microwave irradiation, and alternative energy source are becoming as a solvent for many enzymatic reactions. We recently showed that the incubation of firefly luciferase from Photinus pyralis with various ionic liquids increased the activity and stability of luciferase. Magnetic nanoparticles supported ionic liquids have been obtained by covalent bonding of ionic liquids-silane on magnetic silica nanoparticles. In the present study, the effects of [γ-Fe₂O₃@SiO₂][BMImCl] and [γ-Fe₂O₃@SiO₂][BMImI] were investigated on the structural properties and function of luciferase using circular dichroism, fluorescence spectroscopy, and bioluminescence assay. Enzyme activity and structural stability increased in the presence of magnetic nanoparticles supported ionic liquids. Furthermore, the effect of ingredients which were used was not considerable on K _m value of luciferase for adenosine-5′-triphosphate and also K _m value for luciferin.     

Platinum Nanoparticles Supported on Graphite Nanofibers Prepared by Microwave Irradiation and Its Electrocatalytic Activity

Platinum nanoparticles supported on graphite nanofibers (GNFs) were prepared by microwave assistant heating polyol process. TEM images showed that microwave prepared Pt nanoparticles supported on GNFs were small and uniform, and the average diameter was about 3.4 nm. Cyclic voltammetric test showed that Pt/GNFs exhibited very high electrocatalytic activity for methanol oxidation.     

担载型纳米金的制备参数优化及电催化性能探索

纳米尺度的金由于常表现出有趣的尺寸效应和物理化学特性而被大量应用于催化反应中,但是其在电催化反应中的应用却十分有限. 本文以水为溶剂、HAuCl₄为前驱体、十二烷基聚乙二醇醚（Brij 35）等为软模板剂、NaBH₄为还原剂、活性炭或石墨烯为载体,在温和反应条件下获得担载型金纳米电催化剂. 本文考察并优化了关键制备参数和样品纯化方法,最终确定NaBH₄的最佳浓度区间为5 ~ 10mmol•L^-1,Brij 35的最佳浓度约为1 mmol•L^-1,在3 ~ 16 ^oC下金纳米颗粒的尺寸容易控制,石墨烯和活性炭（EC600）是金纳米颗粒的良好载体. 在优化的反应条件下,金纳米颗粒的粒径可以被控制在1 ~ 4 nm. 热处理法可以有效去除表面活性剂,纯化后的担载型纳米金电催化剂在醇类小分子的氧化反应中表现出良好的性能.     

Selectivity Control on Hydrogenation of Substituted Nitroarenes through End‐On Adsorption of Reactants in Zeolite‐Encapsulated Platinum Nanoparticles

Platinum nanoparticles encapsulated into zeolite Y (Pt@Y catalyst) exhibit excellent catalytic selectivity in the hydrogenation of substituted nitroarenes to form the corresponding aromatic amines, even after complete conversion. With the hydrogenation of p‐chloronitrobenzene as a model, the role of zeolite encapsulation toward perfect selectivity can be attributed to constraint of the substrate adsorbed on the platinum surface in an end‐on conformation. This conformation results in the activation of only one adsorbed group, with little influence on the other one in the molecule. Owing to a much lower apparent activation energy of Pt@Y for the hydrogenation of a separately adsorbed nitro group than that of the adsorbed chloro group, the Pt@Y catalyst can prevent hydrodechlorination of p‐chloronitrobenzene under mild conditions. Moreover, such a conformation results in a reduced adsorption energy of target p‐chloroaniline on the platinum surface; thus suppressing the reactivity of hydrodechlorination of p‐chloroaniline to circumvent further C−Cl bond breakage.     

纳米碳纤维载铂作为质子交换膜燃料电池阳极催化剂

采用化学还原法合成了微结构不同的纳米碳纤维(板式、鱼骨式、管式)载铂催化剂(分别记为Pt/p-CNF、Pt/f-CNF、Pt/t-CNF). 通过高分辨透射电镜(HRTEM)和X射线衍射(XRD)等分析技术对催化剂的微观结构进行了表征, 并利用循环伏安(CV)法分析了催化剂的电化学比表面积(ESA). 在此基础上, 制备了膜电极(MEA), 通过单电池测试了催化剂的电催化性能. 结果表明: 铂纳米粒子在不同的纳米碳载体上表现出不同的粒径, 在板式、鱼骨式和管式纳米碳纤维上的铂纳米粒子平均粒径分别为2.4、2.7和2.8 nm. 板式纳米碳纤维载铂催化剂作单电池阳极时表现出良好的电催化性能, 其对应的最高功率密度可达0.569 W·cm^-2, 高于鱼骨式纳米碳纤维载铂催化剂和管式纳米碳纤维载铂催化剂对应的最高功率密度(分别为0.550和0.496 W·cm^-2). 同时, 也制备了碳黑(Pt/XC-72)载铂催化剂. 相比于Pt/XC-72, 纳米碳纤维载体上的铂纳米颗粒有较小的粒径、较好的分散和较高的催化活性, 说明纳米碳纤维是质子交换膜燃料电池(PEMFCs)催化剂的良好载体.     

交联聚苯乙烯-铂铬合物的合成及其催化的硅氢加成反应

首次合成了巯甲基化交联聚苯乙烯-铂络合物,将其用于催化不同结构的碳碳不饱和化合物与甲基二氯硅烷的加成反应,结果表明,该催化剂对乙炔、苯乙烯、苯乙炔、三烷基乙烯基硅烷等化合物具有很高的催化活性,对丙烯酸丁酯的催化活性显著降低,对甲基丙烯酸甲酯则无催化活性,该催化剂用于苯乙烯的硅氢加成反应,可重复使用20次,而且回收再用非常方便。     

纳米铂颗粒的控制生长

Different size platinum nanoparticles, ranging in size from 1.8-14.1 nm, were prepared by multi-step reduction of H2PtCl6 by hydrogen adsorbed on platinum atoms. Transmission electronic microscopy and X-ray diffraction were used to characterize the nanoparticles. After thirty-two iterations of the reaction, the diameter of platinum nanoparticles increased from 1.8 nm to 14.1 nm. The average iterative increase was approximately 0.4 nm. The size distribution of the nanoparticles was narrow. Synthesis procedures which allow for control of platinum nanoparticle size offer the possibility for the further research into how the sizes of nano-catalysts effect catalytic activity.     

在杂多酸催化剂上苯和1-十二烯烷基化合成十二烷基苯

对不同ＳｉＯ２负载磷钨酸（ＰＷ）催化剂的表面性质、热稳定性、酸性、以及对苯与丙烯和１－十二烯的烷基化反应的催化活性进行了对比研究,结果表明,ＰＷ在ＳｉＯ２上的分散状况与ＳｉＯ２的比表面积和孔径大小有关,ＰＷ与载体表面作用的强弱会直接影响负载型催化剂的热性和酸性,采用不同的ＳｉＯ２可以制得比表面积、孔结构和酸强度不同的负载型ＰＷ催化剂,以满足不同催化反应的要求。     

Influence of the Preparation Method on the Physicochemical and Catalytic Properties of Platinum Catalysts Supported on Bayerite Alumina for the Partial Oxidation Reactions of Hydrocarbons

Kinetics and Catalysis - Platinum catalysts supported onto bayerite alumina were synthesized and studied. Alumina of the θ-Al2O3 type, which was prepared from metallic aluminum by an aluminate...