各向异性金纳米粒子的制备及其在催化中的应用（英文）

尽管有关金纳米粒子催化的研究工作很多,但其中大多数都是采用传统的浸渍法将金盐负载到载体上、共沉淀或沉积-沉淀法制得负载的纳米粒子,但这些方法并未吸收最新的纳米技术.最近,金催化剂的研究者开发了在胶态悬浮液中制取金属纳米粒子,然后进行固载,从而使得单金属和双金属催化剂的催化活性和形貌控制取得较大进展.另一方面,最近十年出现了金纳米粒子合成的高级控制技术,得到了许多各向异性的金纳米粒子,且很容易制得新的形貌,可以控制纳米粒子的表面原子配位数和光学特性(可调的等离子体带),这些都与催化密切相关.这些形貌包括纳米棒、纳米星、纳米花、树枝状纳米结构或多面体纳米粒子等.除了高度关注各向异性金纳米粒子的最新开发的制备方法和性质,本综述也清楚地总结了这些纳米粒子独特的催化性能,以及通过提供更高催化性能的金催化剂、控制暴露的活性位,以及热、电和光催化的鲁棒性和可调性,从而给多相催化领域带来令人惊奇的潜在变革.     

无电沉积法AuNPs-MWCNTs的制备及其对黄酮类化合物的电化学催化性能研究

利用多壁碳纳米管具有较低的还原电位,以多壁碳纳米管作为还原剂和负载基底,通过无电沉积法制备了负载纳米金粒子的碳纳米管催化剂。此种材料具有更多的活性位点,避免了纳米金粒子表面保护剂的存在造成其催化活性降低的缺陷,发现其对典型黄酮类化合物-芦丁和黄芩苷具有良好的电化学催化性能和较高的灵敏度,并将其应用于电化学分析检测黄酮类化合物。     

聚合物负载金属纳米粒子型核壳结构催化剂的研究

核壳结构聚合物负载型催化剂因其载体材料独特的结构、形貌和性质而具有优异的催化活性,成为了催化化学领域研究的热点。本文综述了聚合物负载金属纳米粒子型核壳结构催化剂,包括球形聚合物刷负载金属纳米粒子、聚合物中空微球负载金属纳米粒子、聚合物实心微球表面包覆金属纳米粒子等类型催化剂的制备及其相应的催化性能,强调了各类载体的组成和结构特点对催化活性及其稳定性的影响。最后总结了该类催化材料的优势和不足,并对其性能和应用进行了展望。     

分子印迹聚合物负载纳米金催化剂的制备及其底物识别性能

以4-硝基苯甲醇与氯金酸的络合物为模板,利用聚合物空腔内胺基捕获NaBH4还原的纳米粒子,设计和制备了一种具有底物识别性能的分子印迹聚合物负载纳米Au催化剂(Au/MIP).运用红外光谱、紫外-可见光谱和扫描电镜等方法对催化剂进行了表征.同时以水为溶剂,过氧化氢为氧化剂,考察了催化剂在取代苯甲醇氧化反应中的催化性能.结...     

载金微孔分子筛催化剂研究进展

长期以来金被认为是化学惰性的,虽然早期对它的催化活性有所研究,但直到20世纪80年代中期,才相继出现了两个突破性的进展:1985年,英国威尔士大学的Hutchings教授,发现Au-Pd催化剂能够催化乙炔氢氯化反应~([1]);日本首都东京大学的Haruta教授发现,负载型纳米金催化剂具有优异的低温催化CO氧化活性~([2]).之后纳米金催化剂吸引了众多学者的目光,它的应用范围也越来越广泛.研究表明,影响纳米金催化剂催化性能的因素主要有载体的种类和性质、纳米金粒子的尺寸(常小于10 nm)形貌、氧化状态等,如何制备较小纳米金颗粒以及控制其粒径长大是获得高活性高稳定性金催化剂的关键~([3～5]).     

金属氧化物纳米催化的形貌效应

纳米结构催化剂的设计与制备是多相催化的核心问题之一．提高催化活性的传统方法是减小催化剂粒子的尺寸以暴露更多的表面活性位,即纳米催化中的尺寸效应,但这种方法往往带有一定程度的经验性和随机性．近年来,随着纳米材料科学的快速发展,在溶液体系中通过自下而上的合成技术已经可以在纳米尺度上有效调变固体催化剂粒子的形貌．通过纳米催化材料的形貌可控合成,可选择性地暴露高活性或特定能量晶面,从而大幅度提升催化反应活性、选择性和稳定性,也就是纳米催化中的形貌效应,这也是当前纳米催化研究的热点之一．本文以作者近年来研究的C0304、CeO2和Fe2O3为重点,总结了纳米结构金属氧化物在多相催化反应中的形貌效应,分析了氧化物暴露品面的化学性质对催化性能的作用机制．这种基于形貌效应的纳米催化不仅加深了在纳米尺度甚至原子层次上对催化剂构一效关系的认知,而且对设计和开发实用高效催化剂也具有重要的理论价值．     

聚酰胺酸盐稳定的金纳米催化剂用于羧酸的绿色合成

使用一锅法成功制备了水溶性聚酰胺酸盐稳定的金纳米催化剂(AuNPs-PAAS),将该催化剂用于伯醇的催化氧化.利用紫外-可见分光光度计,X射线衍射仪(XRD),透射电子显微镜(TEM)等表征方法对催化剂进行了表征.结果表明,金纳米粒子在聚酰胺酸溶液中处于均匀分散状态,金纳米尺寸约为5 nm.将制备的纳米金催化剂用于伯醇的氧化,评价了其在伯醇氧化成羧酸反应中的催化性能,结果显示,在空气为氧化剂,水为溶剂的条件下,AuNPs-PAAS对伯醇的催化氧化为高效的准均相催化过程,高选择性得到羧酸产物,通过调节溶液的pH值,可以很容易的实现产物与反应体系分离和催化剂的回收和循环利用.     

单分子层保护纳米 Au 粒子表面配位催化剂的制备及其应用

 贵金属纳米粒子由于其小尺寸效应而表现出特殊的催化性能. 综述了纳米 Au 粒子表面配位催化剂的制备方法及其在催化中的应用. 由于 Au 可与硫化物形成配位键, 所以硫化物可在 Au 表面形成有序单分子膜. 单分子膜保护的 Au 纳米粒子具有非常好的溶解性、分散性、稳定性, 以及由不同的表面功能团而导致的不同的催化性能. 该催化体系兼具均相催化剂和多相催化剂的特点, 这对开发新型催化剂具有重要的理论和实际意义.     

负载型Pt模型催化剂中Pt纳米粒子的形貌对CO氧化活性的影响

采用简单的化学还原法制备了具有不同形貌特征的Pt纳米粒子,并利用浸渍法将其负载到SiO2上,得到了粒子分散均一的负载型Pt催化剂,考察了其催化CO氧化反应性能.X射线荧光分析、X射线光电子能谱、红外光谱和透射电镜结果表明,Pt/SiO2模型催化剂上CO氧化活性的不同来源于Pt纳米粒子不同晶面的贡献,即Pt纳米粒子的晶型...     

组装在贵金属基底上的金纳米粒子对CO的电化学催化氧化

研究了组装在Au, Pt电极表面的金纳米粒子对CO的电化学催化氧化行为, 首次在实验上观察到较大粒径金纳米粒子(粒径＞10 nm)对CO的电催化氧化活性. 考察了金粒子表面金氧化物对粒子电催化活性的影响, 发现表面金氧化物的形成是金纳米粒子对CO具有电催化氧化活性的前提. 对于相同粒径的金纳米粒子, 随着粒子表面金氧化物量的增加，催化活性增大.     

Gold Decorated Graphene by Laser Ablation for Efficient Electrocatalytic Oxidation of Methanol and Ethanol

A well‐known limitation in the fabrication of metal‐graphene composite has been the use of surfactants that strongly adsorb on the surface and reduce the performance of the catalyst. We demonstrate here a novel one‐pot synthesis of gold nanoparticles by laser ablation of gold strip and in‐situ decoration on graphene substrate. Not only the impregnation of nanoparticles was linker free, but also the synthesis by itself was surfactant‐free. The composite materials were well characterized morphologically and functionally using electron microscopy, X‐ray and electron diffraction, Raman spectroscopy, Zeta potential, electrochemical measurements and UV‐Visible spectroscopic techniques. This linker‐free gold‐graphene based composite has been employed for catalytic applications pertaining to electrooxidation. We have explored the use of this composite as a binder‐free electrode in electrocatalytic oxidation of methanol and ethanol in alkaline medium. Additionally, the onset potential for ethanol oxidation was found to be more negative, ?100 mV, an indication of its promising application in direct ethanol fuel cells.     

Titania‐Coated Metal Nanostructures

The synergistic effect between metal and TiO₂ nanoparticles brings about new, enhanced functionalities for a myriad of applications, ranging from labeling and sensing to catalysis and surface‐enhanced Raman scattering. Although extensive work has been done in the preparation of concentric TiO₂‐coated metal nanostructures, current methods for the synthesis of noncentrosymmetric morphologies are still very limited. This Focus review summarizes the various methods used to prepare TiO₂‐coated metal nanostructures, with a particular emphasis on noncentrosymmetric morphologies, their novel plasmonic properties, and their promising applications in the fields of catalysis and photocatalysis.     

金纳米颗粒制备及应用研究进展

金纳米颗粒是近年研究的一种热门材料。介绍了金纳米颗粒主要的制备方法,包括化学还原法,两相法,晶种生长法以及模板法,并总结了金纳米粒子在生物医学、传感器、催化剂、电化学等领域的应用进展。     

Metal–Support Cooperative Catalysts for Environmentally Benign Molecular Transformations

Metal–support cooperative catalysts have been developed for sustainable and environmentally benign molecular transformations. The active metal centers and supports in these catalysts could cooperatively activate substrates, resulting in high catalytic performance for liquid‐phase reactions under mild conditions. These catalysts involved hydrotalcite‐supported gold and silver nanoparticles with high catalytic activity for organic reactions such as aerobic oxidation, oxidative carbonylation, and chemoselective reduction of epoxides to alkenes and nitrostyrenes to aminostyrenes using alcohols and CO/H₂O as reducing reagents. This high catalytic performance was due to cooperative catalysis between the metal nanoparticles and basic sites of the hydrotalcite support. To increase the metal–support cooperative effect, core–shell nanostructured catalysts consisting of gold or silver nanoparticles in the core and ceria supports in the shell were designed. These core–shell nanocomposite catalysts were effective for the chemoselective hydrogenation of nitrostyrenes to aminostyrenes, unsaturated aldehydes to allyl alcohols, and alkynes to alkenes using H₂ as a clean reductant. In addition, these solid catalysts could be recovered easily from the reaction mixture by simple filtration, and were reusable with high catalytic activity.     

Oxygen dissociation on palladium and gold core/shell nanoparticles

Oxygen dissociation reaction on gold, palladium, and gold‐palladium core/shell nanoparticles was investigated with plane wave basis set, density functional theory. Bader population analysis of charge and electron distribution was employed to understand the change of catalytic activity as a function of the nanopaticle composition. The nanoparticles’ electronic properties were investigated and the degree of core/shell charge polarization was estimated for each composition. It was found that surface polarization plays an important role in the catalysis of the initial step of electrophile reactions such as oxygen dissociation. We have investigated the O₂ adsorption energy on each nanoparticle and the activation barrier for the oxygen dissociation reaction as a function of the nanoparticle structure. Furthermore, we have investigated the influence of surface geometry, that is., surface bond lengths on the catalytic activity. We have compared the electronic and the geometry effects on the oxygen activation and dissociation. Our design rules for core/shell nanoparticles offer an effective method for control of the surface catalytic activity. Palladium and gold are often used as catalysts in synthetic chemistry. First‐principles calculations elucidate the mechanisms that control the surface reactivity of gold, palladium, and gold‐palladium core shell nanoparticles in oxygen dissociation reactions. Oxygen dissociation is promoted on the gold surface of gold/palladium core‐shell nanoparticles by favorable electron transfer from the core to the shell. Such core‐shell electronic effects can be used for fine‐tuning the nanoparticles catalytic activity.     

金/钯双金属纳米颗粒协同催化酰胺和醇间氢自转移反应中路易斯酸驱动反应路径

金属纳米颗粒,特别是金和它的双金属纳米颗粒作为强大的绿色催化剂广泛用于有机合成反应中。在一个反应体系中使用2个不同催化剂(如协同催化),在均相催化中是一个很好的策略。然而,这种方法仍在发展中。最近我们发现,金/钯双金属纳米颗粒与路易斯酸的协同催化体系可用于伯胺的N-烷基化：即酰胺与醇之间的氢自转移反应。我们详细报道了路易斯酸对该氢自转移反应的影响。结果表明,所选的路易斯酸不仅影响生成目标产物的反应路径,而且影响生成多个中间体和副产物的反应路径。弱的路易斯酸,如三氟甲磺酸碱土金属盐,非常适合酰胺的N-烷基化反应。     

Understanding plasmonic catalysis with controlled nanomaterials based on catalytic and plasmonic metals

Recently, it has been established that the localized surface plasmon resonance (LSPR) excitation in plasmonic nanoparticles can be put toward the acceleration and control of molecular transformations. This field, named plasmonic catalysis, has emerged as a new frontier in nanocatalysis. For metals such as silver (Ag), gold (Au), and copper (Cu), the LSPR excitation can take place in the visible and near-infrared ranges, opening possibilities for the conversion of solar to chemical energy and new/alternative reaction pathways not accessible via conventional, thermally activated catalytic processes. As both catalytic and optical properties can be tuned by controlling several physical and chemical parameters at the nanoscale, design-controlled nanomaterials open the door to unlock the potential of plasmonic catalysis both in terms of fundamental understanding and optimization of performances. In this context, after introducing the fundamentals of plasmonic catalysis, we provide an overview on the current understanding of this field enabled by the utilization of designed-controlled nanostructures based on plasmonic and catalytic metals as model systems. We start by discussing trends in plasmonic catalytic performances and their correlation with nanoparticle size, shape, composition, and structure. Then, we highlight how multimetallic compositions and morphologies containing both catalytic and plasmonic components enables one to extend the use of plasmonic catalysis to metals that are important in catalysis but do not support LSPR excitation in the visible range. Finally, we focus on key challenges and perspectives that are critically important to assist us in designing future energy-efficient plasmonic-catalytic materials.     

Catalytically Active Gold Nanomaterials Stabilized by N-heterocyclic Carbenes

Solid supported or ligand capped gold nanomaterials (AuNMs) emerged as versatile and recyclable heterogeneous catalysts for a broad variety of conversions in the ongoing catalytic ′gold rush′. Existing at the border of homogeneous and heterogeneous catalysis, AuNMs offer the potential to merge high catalytic activity with significant substrate selectivity. Owing to their strong binding towards the surface atoms of AuMNs, NHCs offer tunable activation of surface atoms while maintaining selectivity and stability of the NM even under challenging conditions. This work summarizes well-defined catalytically active NHC capped AuNMs including spherical nanoparticles and atom-precise nanoclusters as well as the important NHC design choices towards activity and (stereo-)selectivity enhancements.     

Tunable Catalytic Performance and Selectivity of a Nanoparticle–Graphene Composite through Finely Controlled Nanoparticle Loading

Graphene‐based composites offer enhanced catalytic performance of metal and semiconductor nanoparticles, but their development is challenging because catalytic performance strongly depends on the structure and composition of the composite. Herein we show that the catalytic performance of a nanoparticle–graphene composite is very dependent on catalyst loading, which can be optimized for simultaneous enhancement of activity and selectivity. A glassy carbon working electrode has been modified with a gold nanoparticle–graphene (Au–G) composite with a varied number of gold nanoparticles per graphene, so that the conducting property of graphene and the electrocatalytic property of the metal were effectively coupled to give the best catalytic activity and selectivity. The modified electrode was used for simultaneous electrochemical detection of a mixture of electroactive species with high sensitivity. This result shows that the catalytic performance of a graphene‐based composite is sensitive to the catalyst loading and should be optimized for the best performance.     

Self-assembly of core-satellite gold nanoparticles for colorimetric detection of copper ions

Molecule-coated nanoparticles are hybrid materials which can be engineered with novel properties. The molecular coating of metal nanoparticles can provide chemical functionality, enabling assembly of the nanoparticles that are important for applications, such as biosensing devices. Herein, we report a new self-assembly of core-satellite gold nanoparticles linked by a simple amino acid l-Cysteine for biosensing of Cu²⁺. The plasmonic properties of core-satellite nano-assemblies were investigated, a new red shifted absorbance peak from about 600 to 800 nm was found, with specific wavelength depending on ratios with assembly of large and small gold nanoparticles. The spectral features obtained using surface-enhanced Raman spectroscopy (SERS) provided strong evidence for the assembly of the Cu²⁺ ions to the L-Cysteine molecules leading to the successful formation of the core-satellite Cu(l-Cysteine) complex on the gold surfaces. In addition, a linear relationship between the concentration of mediating Cu²⁺ and absorbance of self-assembled gold nanoparticles (GNPs) at 680 nm was obtained. These results strongly address the potential strategy for applying the functionalized GNPs as novel biosensing tools in trace detections of certain metal ions.