贵金属纳米颗粒的微生物合成

金属纳米颗粒在材料、催化、医学、环境等众多领域应用广泛,其中,金、银、铂、钯等贵金属的纳米颗粒作为良好的催化剂可提高反应的速率,因此,贵金属纳米颗粒的合成吸引了众多研究者的关注。传统的物理化学法虽能高效、可控地合成贵金属纳米颗粒,但是合成条件苛刻、成本昂贵、且会产生对环境有害的化学物质。因此,探索节能、环保、可持续的绿色合成方法成为纳米合成研究的热点之一。贵金属纳米颗粒的微生物合成法具备绿色合成技术的诸多要素,研究表明某些微生物能将金属盐转化成纳米材料,且微生物繁殖速度快、培养成本低、生长条件温和,从而得到了研究者们的广泛关注。本文归纳总结了目前微生物合成贵金属纳米颗粒的主要研究进展,包括贵金属纳米颗粒可能的合成机制以及尺寸与形貌控制方法,探讨了其在医学、催化、生物传感、环境方面的具体应用,并对贵金属纳米颗粒微生物合成的未来发展进行了展望。     

Engineering Polar Oxynitrides: Hexagonal Perovskite BaWON2

Non-centrosymmetric polar compounds have important technological properties. Reported perovskite oxynitrides show centrosymmetric structures, and for some of them high permittivities have been observed and ascribed to local dipoles induced by partial order of nitride and oxide. Reported here is the first hexagonal perovskite oxynitride BaWON₂, which shows a polar 6H polytype. Synchrotron X-ray and neutron powder diffraction, and annular bright-field in scanning transmission electron microscopy indicate that it crystalizes in the non-centrosymmetric space group P6₃mc, with a total order of nitride and oxide at two distinct coordination environments in cubic and hexagonal packed BaX₃ layers. A synergetic second-order Jahn–Teller effect, supported by first principle calculations, anion order, and electrostatic repulsions between W⁶⁺ cations, induce large distortions at two inequivalent face-sharing octahedra that lead to long-range ordered dipoles and spontaneous polarization along the c axis. The new oxynitride is a semiconductor with a band gap of 1.1 eV and a large permittivity.     

Subsurface Space‐Charge Dopant Segregation to Compensate Surface Excess Charge in a Perovskite Oxide

Since the first prediction by Frenkel, many follow‐up studies have been carried out to show the presence of subsurface space‐charge layers having the opposite sign to that of the excess charge at the surface, producing overall neutrality in ionic crystals. However, no precise experimental evidence demonstrating how the aliovalent solutes segregate in the space‐charge region beneath the surface has been provided over the past several decades. By utilizing atomic‐scale imaging and chemical probing in a perovskite oxide, the origin of the surface excess charge at the topmost surface and the position of segregated dopants in the space‐charge region is precisely determined. The impact of the space‐charge contribution to the dopant distribution near the surface in oxide crystals is explored.     

钙钛矿型固体氧化物燃料电池阳极材料

固体氧化物燃料电池(SOFCs)作为一种高效、洁净的化学电源已经受到各国的重视.钙钛矿型复合氧化物由于其较高的混合导电性和对燃料气较好的催化活性及超强抗积碳能力而越来越被广泛地应用于直接烃类SOFCs的阳极材料中.本文对钙钛矿型固体氧化物燃料电池阳极材料的最新研究进展进行了较为全面的综述,从阳极的设计要求出发,着重比较了LaCrO3系列、SrTiO3系列和双钙钛矿等阳极材料的稳定性、电导率以及电催化活性,指出了其不足,并对其应用前景进行了展望.     

Noble Metal Nanoparticles Stabilized by Hyper-Cross-Linked Polystyrene as Effective Catalysts in Hydrogenation of Arenes

This work is addressing the arenes’ hydrogenation—the processes of high importance for petrochemical, chemical and pharmaceutical industries. Noble metal (Pd, Pt, Ru) nanoparticles (NPs) stabilized in hyper-cross-linked polystyrene (HPS) were shown to be active and selective catalysts in hydrogenation of a wide range of arenes (monocyclic, condensed, substituted, etc.) in a batch mode. HPS effectively stabilized metal NPs during hydrogenation in different medium (water, organic solvents) and allowed multiple catalyst reuses.     

Integrating Perovskite Solar Cells into a Flexible Fiber

Perovskite solar cells have triggered a rapid development of new photovoltaic devices because of high energy conversion efficiencies and their all‐solid‐state structures. To this end, they are particularly useful for various wearable and portable electronic devices. Perovskite solar cells with a flexible fiber structure were now prepared for the first time by continuously winding an aligned multiwalled carbon nanotube sheet electrode onto a fiber electrode; photoactive perovskite materials were incorporated in between them through a solution process. The fiber‐shaped perovskite solar cell exhibits an energy conversion efficiency of 3.3 %, which remained stable on bending. The perovskite solar cell fibers may be woven into electronic textiles for large‐scale application by well‐developed textile technologies.     

双钙钛矿型电极材料在中低温固体氧化物燃料电池中的应用

近年来固体氧化物燃料电池(SOFCs)由于高效率(高达80%)、环境友好和燃料适用广泛等优点得到了人们的广泛关注。但是,由于其通常需要1000 ℃以上的工作温度才能达到所需的性能,其商业化及产业化应用受到了严重制约。中低温固体氧化物燃料电池(IT-SOFCs)的研发是固体氧化物燃料电池进一步商业化的必然趋势。降低工作温度(从高温1000 ℃以上降低至中低温500~800 ℃)可提高燃料电池的稳定性、降低电池运行成本、增加系统材料可选性,而研发出中低温下性能优异的燃料电池电极材料是实现固体氧化物燃料电池中低温化的关键。作为混合离子-电子导体材料之一,双钙钛矿型氧化物材料可以成功地将燃料反应活性区域从传统的电极-电解质-反应气体三相界面扩展到整个电极的表面, 进而降低材料的极化电阻并大大提高电极在中低温条件下对氧的催化活性。由于双钙钛矿结构材料良好的氧离子传输能力、较低的热膨胀系数、优异的催化活性、较强的抗硫中毒和抗碳沉积能力,近年来成为非常有发展潜力的SOFCs电极材料。本文综述双钙钛矿型氧化物材料作为SOFCs电极材料的最新研究进展,指出目前双钙钛矿电极材料存在的主要问题,并提出SOFCs未来的主要研究发展方向。     

Oxidative Mechanochemistry: Direct,Room‐Temperature,Solvent‐Free Conversion of Palladium and Gold Metals into Soluble Salts and Coordination Complexes

Noble metals are valued, critical elements whose chemical activation or recycling is challenging, and traditionally requires high temperatures, strong acids or bases, or aggressive complexation agents. By using elementary palladium and gold, demonstrated here is the use of mechanochemistry for noble‐metal activation and recycling by mild, clean, solvent‐free, and room‐temperature chemistry. The process leads to direct, efficient, one‐pot conversion of the metals, including spent catalysts, into either simple water‐soluble salts or metal–organic catalysts.     

基于蛋白和多肽为模板的贵金属纳米簇合成研究

贵金属(Au, Ag, Pt等)纳米簇通常指的是由几个到约一百个原子组成的分子聚集体, 具有生物相容性好、超小尺寸(<2 nm)以及优异的物理化学性质, 尤其是能发出较强荧光等特点引起了人们的广泛关注. 目前多种贵金属纳米簇的合成方法已相继被报道, 且已应用于生物荧光成像、电化学发光、生物传感器以及细胞标记等多个领域. 本文共分为五部分, 首先重点介绍近几年兴起的以蛋白和多肽为模板来合成纳米簇的方法及优点, 并随后总结列举了文献中所采用的蛋白以及自主设计的多肽组分序列的类别, 随后探索了蛋白和多肽中的特定氨基酸与合成的贵金属纳米簇的荧光波长、量子产率、粒径之间的联系. 本文最后总结阐述了蛋白和多肽为模板成功合成贵金属纳米簇的先决条件并对其生物医学应用前景进行了展望.     

Cobalt‐Doped Perovskite‐Type Oxide LaMnO3 as Bifunctional Oxygen Catalysts for Hybrid Lithium–Oxygen Batteries

Perovskite‐type oxides based on rare‐earth metals containing lanthanum manganate are promising catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline electrolyte. Perovskite‐type LaMnO₃ shows excellent ORR performance, but poor OER activity. To improve the OER performance of LaMnO₃, the element cobalt is doped into perovskite‐type LaMnO₃ through a sol–gel method followed by a calcination process. To assess electrocatalytic activities for the ORR and OER, a series of LaMn_1?xCo_xO₃ (x=0, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5) perovskite oxides were synthesized. The results indicate that the amount of doped cobalt has a significant effect on the catalytic performance of LaMn_1?xCo_xO₃. If x=0.3, LaMn_0.7Co_0.3O₃ not only shows a tolerable electrocatalytic activity for the ORR, but also exhibits a great improvement (>200 mV) on the catalytic activity for the OER; this indicates that the doping of cobalt is an effective approach to improve the OER performance of LaMnO₃. Furthermore, the results demonstrate that LaMn_0.7Co_0.3O₃ is a promising cost‐effective bifunctional catalyst with high performance in the ORR and OER for application in hybrid Li?O₂ batteries.     

Novel Push-Pull Benzodithiophene-Containing Polymers as Hole-Transport Materials for Efficient Perovskite Solar Cells

Donor-acceptor conjugated polymers are considered advanced semiconductor materials for the development of thin-film electronics. One of the most attractive families of polymeric semiconductors in terms of photovoltaic applications are benzodithiophene-based polymers owing to their highly tunable electronic and physicochemical properties, and readily scalable production. In this work, we report the synthesis of three novel push–pull benzodithiophene-based polymers with different side chains and their investigation as hole transport materials (HTM) in perovskite solar cells (PSCs). It is shown that polymer P3 that contains triisopropylsilyl side groups exhibits better film-forming ability that, along with high hole mobilities, results in increased characteristics of PSCs. Encouraging a power conversion efficiency (PCE) of 17.4% was achieved for P3-based PSCs that outperformed the efficiency of devices based on P1, P2, and benchmark PTAA polymer. These findings feature the great potential of benzodithiophene-based conjugated polymers as dopant-free HTMs for the fabrication of efficient perovskite solar cells.     

Hexaazatrinaphthylene Derivatives: Efficient Electron‐Transporting Materials with Tunable Energy Levels for Inverted Perovskite Solar Cells

Hexaazatrinaphthylene (HATNA) derivatives have been successfully shown to function as efficient electron‐transporting materials (ETMs) for perovskite solar cells (PVSCs). The cells demonstrate a superior power conversion efficiency (PCE) of 17.6 % with negligible hysteresis. This study provides one of the first nonfullerene small‐molecule‐based ETMs for high‐performance p–i–n PVSCs.     

Electronic and Magnetic Properties of Encapsulated MoS2 Quantum Dots: The Case of Noble Metal Nanoparticle Dopants

With the rise of 2D materials, such as graphene and transition metal dichalcogenides, as viable materials for numerous experimental applications, it becomes more necessary to maintain fine control of their properties. One expedient and efficacious technique to regulate their properties is surface functionalization. In this study, DFT calculations are performed on triangular MoS₂ quantum dots (QDs) either partially or completely doped with nanoparticles (NPs) of the noble metals Au, Ag, and Pt. The effects of these dopants on the geometry, electronic properties, magnetic properties, and chemical bonding of the QDs are investigated. The calculations show that the structural stability of the QDs is reduced by Au or Ag dopants, whereas Pt dopants have a contrasting effect. The NPs diminish the metallicity of the QD, the extent of which is contingent on the number of NPs adsorbed on the QD. However, these NPs exert distinctly disparate charge transfer effects—Ag NPs n‐dope the QDs, whereas Au and Pt NPs either n‐ or p‐dope. The molecular electrostatic potential maps of the occupied states show that metallic states are removed from the doping sites. Notwithstanding the decrease of magnetization in all three types of hybrid QD, the distribution of spin density in the Pt‐doped QD is inherently different from that in the other QDs. Bond analyses using the quantum theory of atoms in molecules and the crystal orbital Hamilton population suggest that bonds between the Pt NPs and the QDs are the most covalent and the strongest, followed by the Au?QD bonds, and then Ag?QD bonds. The versatility of these hybrid QDs is further examined by applying an external electric field in the three orthogonal orientations, and comparing their properties with those in the absence of the electric field. There are two primary observations: 1) dopants at the tail, head and tail, and in the fully encased configuration are most effective in modifying the distribution of metallic states if the electric field is absent, and 2) the metallic states in these aforementioned QDs are generally insensitive to the electric field. Conversely, the asymmetric electric effects on the charge transfer in these QDs have to be carefully monitored to allow finer control of their structural stability. This study aptly demonstrates the value of noble metal dopants for manipulating the properties of MoS₂ QDs, and shows the versatility of these hybrid QDs as tunable nanodevices. This notably extends the functionality of these nanostructures for applications such as catalysis and nanoelectronics.     

Development of a General Non‐Noble Metal Catalyst for the Benign Amination of Alcohols with Amines and Ammonia

The N‐alkylation of amines or ammonia with alcohols is a valuable route for the synthesis of N‐alkyl amines. However, as a potentially clean and economic choice for N‐alkyl amine synthesis, non‐noble metal catalysts with high activity and good selectivity are rarely reported. Normally, they are severely limited due to low activity and poor generality. Herein, a simple NiCuFeO_x catalyst was designed and prepared for the N‐alkylation of ammonia or amines with alcohol or primary amines. N‐alkyl amines with various structures were successfully synthesized in moderate to excellent yields in the absence of organic ligands and bases. Typically, primary amines could be efficiently transformed into secondary amines and N‐heterocyclic compounds, and secondary amines could be N‐alkylated to synthesize tertiary amines. Note that primary and secondary amines could be produced through a one‐pot reaction of ammonia and alcohols. In addition to excellent catalytic performance, the catalyst itself possesses outstanding superiority, that is, it is air and moisture stable. Moreover, the magnetic property of this catalyst makes it easily separable from the reaction mixture and it could be recovered and reused for several runs without obvious deactivation.     

Metal Oxide Nanosheets as 2D Building Blocks for the Design of Novel Materials

Research into 2-dimensional materials has soared during the last couple of years. Next to van der Waals type 2D materials such as graphene and h-BN, less well-known oxidic 2D equivalents also exist. Most 2D oxide nanosheets are derived from layered metal oxide phases, although few 2D oxide phases can be also made by bottom-up solution syntheses. Owing to the strong electrostatic interactions within layered metal oxide crystals, a chemical process is usually needed to delaminate them into their 2D constituents. This Review article provides an overview of the synthesis of oxide nanosheets, and methods to assemble them into nanocomposites, mono- or multilayer films. In particular, the use of Langmuir–Blodgett methods to form monolayer films over large surface areas, and the emerging use of ink jet printing to form patterned functional films is emphasized. The utilization of nanosheets in various areas of technology, for example, electronics, energy storage and tribology, is illustrated, with special focus on their use as seed layers for epitaxial growth of thin films, and as electrochemically active electrodes for supercapacitors and Li ion batteries.     

Two Dimensional Materials Beyond MoS2: Noble‐Transition‐Metal Dichalcogenides

The structure and electronic structure of layered noble‐transition‐metal dichalcogenides MX₂ (M=Pt and Pd, and chalcogenides X=S, Se, and Te) have been investigated by periodic density functional theory (DFT) calculations. The MS₂ monolayers are indirect band‐gap semiconductors whereas the MSe₂ and MTe₂ analogues show significantly smaller band gap and can even become semimetallic or metallic materials. Under mechanical strain these MX₂ materials become quasi‐direct band‐gap semiconductors. The mechanical‐deformation and electron‐transport properties of these materials indicate their potential application in flexible nanoelectronics.     

Size‐Controlled Formation of Noble‐Metal Nanoparticles in Aqueous Solution with a Thiol‐Free Tripeptide

A combinatorial screening revealed the peptide H‐His‐d ‐Leu‐d ‐Asp‐NH₂ ( 1 ) as an additive for the generation of monodisperse, water‐soluble palladium nanoparticles with average diameters of 3 nm and stabilities of over 9 months. The tripeptide proved to be also applicable for the size‐controlled formation of other noble‐metal nanoparticles (Pt and Au). Studies with close analogues of peptide 1 revealed a specific role of each of the three amino acids for the formation and stabilization of the nanoparticles. These data combined with microscopic and spectroscopic analyses provided insight into the structure of the self‐assembled peptidic monolayer around the metal core. The results open interesting prospects for the development of functionalized metal nanoparticles.