磁性钴纳米晶的二维自组装

在两种表面活性剂存在下，采用高温醇还原，合成出单分散、平均颗粒尺寸为14±19nm，直径标准偏差小(～18%)的磁性金属Co纳米晶.利用x射线衍射、紫外吸收光谱、x射线光电子能谱及透射电子显微镜对其结构和表面价态进行了分析.并将磁性金属Co纳米晶自组织形成有序的二维(2D)六方紧密堆积结构. 关键词： Co纳米晶 单分散 自组装     

Monodispersive CoPt Nanoparticles Synthesized Using Chemical Reduction Method

Monodispersive CoPt nanopaxticles in sizes of about 2.2 nm axe synthesized by superhydride reduction of COCl2 and PtCl2 in diphenyl ether. The as-prepared nanoparticles show a chemically disordered Al structure and axe superpaxamagnetic. Thermal annealing transforms the Al structure into chemically ordered Llo structure and the particles are ferromagnetic at room temperature.     

Organic molecules modified palladium nanowires arrays prepared by high temperature liquid phase reduction

This paper reports high temperature liquid phase synthesis of Pd nanowires using chemically modified porous anodic aluminium oxide as template. In this synthesis process, oleic acid is used to modify the inner wall of the pores and Pd^2＋ complex with oleylamine is filled into the channel of the template. The complex is then reduced to give oleylamine-capped Pd nanowires. This paper suggests that oleic acid can improve the environment of inner wall of the pores, leading to the formation of uniform Pd nanowires. The synthetic process can be extended to make other types of nanowires.     

Cathodoluminescent and electrical properties of an individual ZnO nanowire with oxygen vacancies

A single ZnO nanowire with intrinsic oxygen vacancies is utilized to fabricate four-contact device with focus ion beam lithography technique. Cathodoluminescent spectra indicate strong near-UV and green emission at both room temperature and low temperatures. Experimental measurement shows the temperature-dependent conductivity of the ZnO nanowire at low temperatures （below 100 K）. The further theoretical analysis confirms that weak localization plays an important role in the electrical transport, which is attributed to the surface states induced by plenty of oxygen vacancies in ZnO nanowire.     

Preparation of few-layer graphene-capped boron nanowires and their field emission properties

Large-area boron nanowire(BNW) films were fabricated on the Si(111) substrate by chemical vapor deposition(CVD). The average diameter of the BNWs is about 20 nm, with lengths of 5–10 μm. Then, graphene-capped boron nanowires(GC-BNWs) were obtained by microwave plasma chemical vapor deposition(MPCVD). Characterization by scanning electron microscopy indicates that few-layer graphene covers the surface of the boron nanowires. Field emission measurements of the BNWs and GC-BNW films show that the GC-BNW films have a lower turn-on electric field than the BNW films.     

高温液相还原法制备钴纳米晶及其二维有序阵列

由于小尺寸效应,纳米晶具有独特的电、磁、光学和结构性质,因而在材料领域具有广阔的应用前景,例如,利用磁性金属和半导体纳米晶对尺寸敏感的特性进行超高密度信息磁存储及微电子技术的应用研究．但表面原子的巨大剩余成键能力使其倾向于相互团聚并长大,只有实现纳     

Controlled growth of large＇scale silver nanowires

Large-scale silver nanowires with controlled aspect ratio were synthesized via reducing silver nitrate with 1, 2- propanediol in the presence of poly （vinyl pyrrolidone） （PVP）. Scanning electron microscopy, transmission electron microscopy and x-ray powder diffraction were employed to characterize these silver nanowires. The diameter of the silver nanowires can be readily controlled in the range of 100 to 400 nm by varying the experimental conditions. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy results show that there exists no chemical bond between the silver and the nitrogen atoms. The interaction between PVP and silver nanowires is mainly through the oxygen atom in the carbonyl group.     

Anomalous aggregation growth of palladium nanosphere with SPR band in visible range

The morphology and properties of nanostructures are significantly influenced by the chemical coordination during their growth procedure. Using small molecule N-vinyl pyrolidone as stabilizer, this paper introduces a new strategy for synthesis of palladium nanospheres, which has a novel surface plasmon resonance band in the visible range. An aggregation growth mode was observed in the growth process. More specifically, the growth rate increases with increasing concentration of stabilizer. The absorption in visible region suggests new optical applications for these Pd nanospheres, such as photocatalysis, photothermal heating and surface enhanced Raman scattering.     

Formation and photoluminescence properties of boron nanocones

This paper reports that a simple chemical vapour deposition method has been adopted to fabricate large scale, high density boron nanocones with thermal evaporation of B/B2O3 powders precursors in an Ar/H2 gas mixture at the synthesis temperature of 1000-1200℃. The lengths of boron nanocones are several micrometres, and the diameters of nanocone tops are in a range of 50-100 nm. transmission electron microscopy and selected area electron diffraction indicate that the nanocones are single crystalline α-tetragonal boron. The vapour liquid solid mechanism is the main formation mechanism of boron nanocones. One broad photolumineseence emission peak at the central wavelength of about 650 nm is observed under the 532 nm light excitation. Boron nanocones with good photoluminescence properties are promising candidates for applications in optical emitting devices.     

新型机械解理方法在二维材料研究中的应用

自从石墨烯被发现以来,机械解理技术已经成为制备高质量二维材料的重要方法之一,在二维材料本征物性的研究方面展现出了独特的优势.然而传统机械解理方法存在明显的不足,如制备效率低、样品尺寸小等,阻碍了二维材料领域的研究进展.近些年我们在机械解理技术方面取得了一系列的突破,独立发展了一套具有普适性的新型机械解理方法.这种新型机械解理方法的核心在于通过改变解理过程中的多个参数,增强层状材料与基底之间的范德瓦耳斯相互作用,从而提高单层样品的产率和面积.本文着重以石墨烯为例,介绍了该技术的过程和机理.相比于传统机械解理方法,石墨烯的尺寸从微米量级提高到毫米量级,面积提高了十万倍以上,产率大于95%,同时石墨烯依然保持着非常高的质量.这种新型机械解理方法具有良好的普适性,目前已经在包括MoS₂,WSe₂,MoTe₂,Bi2212等几十种材料体系中得到了毫米量级以上的高质量单层样品.更重要的是,在解理过程中,通过调控不同的参数,可以在层状材料中实现一些特殊结构的制备,如气泡、褶皱结构等,为研究这些特殊材料体系提供了重要的物质保障.未来机械解理技术还有很多值得深入研究的科学问题,该技术的突破将会极大地推动二维材料领域的研究进展.