Related Experiments and Their Analysis for Synthesizing of Several Representative Composite Nanowires

近年来,复合纳米线的制备成为低维纳米结构研究的一个热点。综述了几种典型复合纳米线的生长方法,分析了它们的生长机制,以及影响它们生长的各种因素。希望通过这几个制备复合纳米线的实验的分析与研究能对相关实验研究工作提供一些参考。In recent years, synthesis of composite nanowires has been a hot topic in field of low dimension nanostructure.Considerable efforts have been devoted to the synthesis of composite nanowires via different methods.There is,however,few found to systematially and critically review on the growth of composite nanowires.In this paper, it presents a systematical and critical review on growth methods,corresponding growth mechanism and the parameters that affects the nanowires,with an aim of providing some critical referenes for the related future experiment research.国家自然科学基金专项研究课题(90406024);; 国家自然科学基金(90401022);; 教育部科学技术研究重点项目(105099);; 厦门大学启动经费(XK0016);; 福建省科技计划项目(2005HZ1019

Fractal growth of deposited carbon on the unirradiated surface of SiO_x nanowires induced by focused electron beam

电子束诱导沉积技术已被证实可以实现各种材料的分形生长,但是目前尚未发现聚焦电子束辐照下低维纳米结构表面未受辐照位置的分形生长现象,造成了聚焦电子束诱导分形生长机理研究的空白与片面性.以透射电子显微镜中残留的有机气体分子为前驱体,室温下利用高能聚焦电子束辐照,研究了一维非晶SIOX纳米线表面未受辐照位置碳沉积的分形生长.利用高分辨透射电子显微镜对SIOX纳米线表面非晶碳的沉积过程进行原位观察,发现了SIOX纳米线表面未受辐照位置非晶碳的不均匀沉积及分形生长,并捕捉到了碳沉积分形生长过程的细节.同时对聚焦电子束诱导SIOX纳米线表面未受辐照位置非晶碳的不均匀沉积及分形生长机理进行了深入的探索.It has been proven that electron beam induced deposition technique can lead to fractal growth of some materials,while there is no report on the fractal growth on the unirradiated surface of low dimensional nanostructures as induced by focused electron beam irradiation.In this paper,the fractal growth on the unirradiated surface of amorphous SiOx nanowire was designedly investigated via focused electron beam irradiation at room temperature,and the deposition details of amorphous carbon on the surface of SiOx nanowire was in-situ observed by a high resolution transmission electron microscope.It was found that a series of intriguing phenomena such as nonuniform deposition and fractal growth of amorphous carbon occured on the unirradiated surface of SiOx nanowire.More importantly,details of the fractal growth process of deposited carbon were also in-situ observed.Furthermore,the nonuniform deposition and fractal growth mechanisms of amorphous carbon occurred on the unirradiated surface of SiOx nanowire under focused electron beam irradiation were proposed and discussed.国家科技计划国际科技合作与交流专项(2008DFA51230);国家重点基础研究发展计划(2007CB936603);国家自然科学基金(90401022;60776007);中澳科技合作特别基金(20050222);教育部科技研究重点项目(105099)资

Controllable surface modification of nanowires by focused-electron-beam-induced deposition of carbon

作为一种典型的准一维纳米材料,纳米线具有纳米材料所特有的小尺寸效应或纳米曲率效应,经表面修饰的纳米线一般具有不同于普通纳米线的特殊性质.利用实验室发展成熟的透射电子显微镜原位辐照技术,以透射电子显微镜中残留的有机气体分子为前驱体,成功地在纳米线表面可控沉积了非晶碳纳米颗粒和碳纳米棒,以及局域凸起的非晶碳膜并形成局域肿大的同轴结构.实验结果表明,该方法能够方便地通过控制聚焦电子束的束斑尺寸、辐照方式、辐照时间以及辐照位置等参数,在纳米线表面精确可控地沉积各种非晶碳纳米结构,从而实现纳米线的表面可控修饰.对聚焦电子束辐照下基于纳米线的各种碳纳米结构的可能沉积机理作了进一步地探索,并针对透射电子显微镜中如何减少因电子束辐照诱导非晶碳沉积造成的样品污染提出了几点建议.Surface-modified nanowires generally own some additional properties,and thus in this paper,the authors particularly studied the surface modification of nanowires via irradiation of focused electron beam in a Tecnai F-30 field emission transmission electron microscope (TEM).It was observed that controllable deposition of all kinds of amorphous carbon nanostructures,such as carbon particles,carbon rods and carbon films with local bulging,could be got on the surface of nanowires after intentional irradiation.In details,the controllable deposition of carbon nanostructures could be easily and precisely controlled by changing of some irradiation parameters such as beam spot diameter,irradiation manner,irradiation time and irradiation position.The possible deposition mechanisms of carbon nanostructures on the wire surface as induced by irradiation of focused electron beam in TEM were further discussed.In addition,some suggestions were also proposed on reducing of specimen pollution caused by undesired deposition of amorphous carbon materials during the irradiation.国家科技计划国际科技合作与交流专项(编号:2008DFA51230);国家重点基础研究发展计划(编号:2007CB936603);国家自然科学基金(批准号:90401022;60776007);中澳科技合作特别基金(编号:20050222);教育部科技研究重点项目(编号:105099)资

人民币套息交易:市场基础和收益风险特征

在全球经济金融虚拟化背景下,利率与汇率的波动性增强。以跨国公司为代表的经济主体为实现利润最大化目标,在全球进行资源优化配置,频繁进出利率与汇率市场,进行套息交易。相应交易的长期性和广泛性表明,利率平价理论提出的利率与汇率间的平价均衡关系并不成立,套息交易对金融系统安全性具有负面影响。在资本账户未完全放开的条件下,关于人民币套息交易机理机制的实证研究表明,人民币套息交易有多种途径,大宗商品交易是较突出的渠道。因此,在人民币国际化过程中须健全金融监管,协调好资本账户开放的步骤与速度,防范套息交易危害实体经济发展。国家自然科学基金项目“资金流、交易者异质性与股市波动”(71373225)阶段性成

Direct experimental evidence for detailed growth of SiO_x nanowire during CVD

在纳米线的制备中,气-液-固(VlS)生长机制得到了人们的广泛认可,但该机制的很多细节还停留在模型阶段.依托实验室自行设计的一台生长条件高度可控的高温化学气相沉积(CVd)系统,采用较为简便的方法,直接在SI片衬底上制备出了SIOX纳米线.通过严格控制实验参数,用离位观测捕捉到了纳米线的催化、形核和长大的一系列过程及其相关细节,并发现纳米线从细到粗的气-液-固(VlS)生长机制.讨论了气-液-固(VlS)机制中气态SI原子的来源以及纳米线的催化、形核和长大过程中的纳米曲率效应和“纳米熟化“现象,取得了对SIOX纳米线VlS催化生长机制的理解的突破.Among the mechanisms for nanowire growths, the vapor-liquid-solid (VLS) mechanism is the most widely accepted.Nevertheless, the growth process and relevant details for the VLS mechanism are not yet fully understood for the complicated nano processes involved.In the present article, with a precise control of temperature, gas flow, pressure, and reaction periods in a home- built high-temperature chemical vapor deposition (CVD) system, detailed processes of catalyzing, nucleation, and growth of the SiOx nanowires and a stepwise non uniformity in diameter of nano- wire were successfully traced.With analysis of these experimental results via nanocurvature and nano ripening effects, a further understanding of the vapor-liquid-solid mechanism, especially the mechanism for formation of the stepwise non uniformity in diameter of nanowires, was achieved for the first time.国家科技计划国际科技合作与交流专项(编号:2008DFA51230);国家重点基础研究发展计划(编号:2007CB936603);国家自然科学基金(批准号:60776007、90401022);中澳科技合作特别基金(编号:20050222);教育部科技重点项目(编号:105099)资

Construction of eukaryotic vector pcDNA3.1-flag-pygo2 and expression in C6 cell

目的构建pcDNA3.1-flag-pygo2真核表达载体并在C6细胞中进行表达。方法从小鼠脑胶质细胞中提取总RNA,RT-PCR法反转录合成c DNA,设计引物,调取目的片段,与pcDNA3.1-flag载体连接后转化大肠杆菌DH5α,LB平板筛选菌落,提取质粒。重组质粒pcDNA 3.1-flag-pygo2经过酶切鉴定及测序后,阳离子脂质体法转染C6细胞并经免疫细胞化学染色及蛋白印迹检测重组体的表达。结果重构质粒pcDNA 3.1-flag-pygo2经限制性核酸内切酶EcoRⅠ,HindⅢ酶切分析及测序检查,表明真核表达载体构建正确;瞬时转染C6细胞后,免疫细胞荧光染色及蛋白印迹检测表明转染细胞能够表达外源Pygo2基因。结论成功构建了pcDNA3.1-flag-pygo2真核表达载体并能够在真核细胞中进行表达,这为今后研究pygo2基因在胶质瘤中的作用机制奠定了基础。Objective To construct the eukaryotic expression vector pcDNA3.1-flag-pygo2 and express the combined protein in C6 cell line.Methods To extract total RNA from primary glial cell of mouse and to synthesize c DNA by RT-PCR,then design primer and clone whole segment of pygo2 gene.After the targeted gene was inserted into vector pcDNA3.1-flag,the recombined plamid was transformed into E coli DH5α for LB agar plate screening and the recombined plasmid were extracted and purified.After verification by double enzyme digestion and sequencing.,the constructed eukaryotic expression plamid was transfected to C6 cell line by lipofectamin method,finally the protein expression was detected by immunocytochemical staining as well as western blot.Results The new constructed vector was confirmed by restricted enzyme Eco R I,HindIII digestion assay and correct Pygo2 was verified by sequenceing.finally,pcDNA3.1-flag-hpygo2 can express exogenous pygo2 gene in glioma C6 cell line after transient transfection by the determination of immunocytofluorescent staining and western blot.Conclusion The new plamid pcDNA3.1-flag-pygo2 was constructed successfully,and can express fused protein in eukaryotic cell,which establish the foundation for future research on pygo2 gene function in human glioma

Over-expression of Pygo2 Promotes C6 Cells Proliferation of Glioma

目的通过构建过表达PygO2的重组体上调PygO2表达,探讨其在大鼠胶质瘤C6细胞增殖中的作用及机制。方法重组体经ECOr I和HIndⅢ双酶切鉴定和dnA测序后,用脂质体2000将其转染大鼠胶质瘤C6细胞,采用WESTErn blOT检测外源PygO2蛋白表达,应用克隆形成实验和MTT法检测细胞增殖,流式细胞术检测细胞周期,采用WESTErn blOT检测过表达PygO2对C6细胞中CyClInd1、β-CATEnIn水平的影响,并采用细胞免疫荧光法检测其对C6细胞中CyClInd1、β-CATEnIn亚细胞定位的影响。结果双酶切和测序鉴定结果证实插入序列正确,重组体能有效上调PygO2表达。将重组体转染C6细胞上调PygO2表达后,细胞的生长增殖被显著促进,克隆形成显著增多,细胞周期进程从g1期至S期转变显著增强;且CyClInd1水平随之增高,亚定位无改变,β-CATEnIn水平和亚细胞定位无明显改变。结论成功构建了过表达PygO2的重组体,过表达PygO2通过增高CyClInd1水平,促进细胞从g1期进入S期,从而促进大鼠胶质瘤C6细胞增殖。Objective To up-regulate expression of Pygopus2(Pygo2) by construction of the recombinant vectors of over-expression of Pygo2 protein,and to explore the role and mechanism of over-expression of Pygo2 in C6 cells proliferation of glioma.Methods The recombinant plasmids were digested with EcoRⅠ and Hind Ⅲ to execute the restriction endonuclease identification,then the sequence analysis was assayed by DNA sequencing.The recombinant plasmids were transfected into cultured glioblastoma C6 cells using lipofectamineTM 2000.The exogenous Pygo2 protein level of C6 cells was detected by Western blot analysis.Colony forming assay and MTT assay were used to detect the cell proliferation,and cell cycle analysis was performed by flow cytometry analysis.The effect of Pygo2 over-expression on the level of cyclinD1 and β-catenin of C6 cells was detected by Western blot analysis,and the expression and subcellular location of cyclinD1 and β-catenin of C6 cells were further quantified by immunofluorescent staining.Results The recombinant plasmids were completely coincided with the designs by the restriction map and the sequence analysis,which up-regulated Pygo2 expression of C6 cells efficiently.After Pygo2 expression were up-regulated by transfected C6 cells with the recombinant plasmids,cells proliferation was promoted and colony forming was increased significantly,cell cycle progression from G1 to S transition was enhanced notably.Furthermore,the expression level of cyclinD1 was significantly increased without change of subcellular location,and the expression level and subcellular location of β-catenin were not changed obviously.Conclusion The recombinant vectors of Pygo2 over-expression were constructed successfully.Over-expression of Pygo2 promotes the growth of glioma cells by an increased expression of cyclinD1 to improve G1/S transition.重庆市自然科学基金资助项目(cstc2011jjA10110);重庆市教委科技基金资助项目(KJ100504);福建省自然科学基金资助项目(2009D002

Structural instabilities of single-walled carbon nanotubes under electron beam irradiation

利用透射电镜(TEM)原位观察了一端固定一端自由和两端固定的单壁碳纳米管(SWNT(s))在电子束辐照下的结构不稳定性。研究发现,一端固定一端自由的SWNT优先轴向和径向收缩后颈缩,最后形成一个个碳笼紧密相连的收缩结构("碳笼-碳笼"结构);两端固定的SWNT仅径向收缩后颈缩,最后形成许多碳笼相连的类似结构。此外,后者在电子束辐照下断开后又会重新粘合起来,表现出很强的表面塑性流变或湿润效应。这些电子束辐照诱导SWNTs非热激活结构不稳定性现象可以用我们最近提出的表面纳米曲率效应和能量束超快诱导软模和点阵失稳进行全新、全面、正确的解释。Structural instabilities of single-walled carbon nanotubes(SWNTs) of two typical settings,which are respectively fixed at only one end and at both ends,were investigated under electron beam irradiation by our developed in-situ transmission electron microscopy observation technique.It was observed that the tube fixed only at one end preferentially shrunk in axis direction first,then shrunk and necked in diameter,and finally formed a carbon cagelike strand structure at the tube free end whereas the tube fixed at both ends merely shrunk and necked in diameter with the similar formation of carbon cage-like strand structure.It is especially intriguing that the necked carbon cage-like strand structure in the latter case was able to re-fuse after breaking and thus demonstrated a strong wetting ability and an amazing athermal plastic flow on the surface of the SWNT fixed at both ends under the electron beam irradiation at room temperature.The above athermal structural instabilities of SWNTs as induced by electron beam irradiation can be well accounted for by the completely new concepts of the surface nanocurvature and ultrafast energetic beam-induced soft mode and lattice instability as we recently proposed.国家自然科学基金资助项目(No.90401022No.90406024);; 国家教育部科技重点资助项目(No.105099);; 中澳科技合作特别基金资助项目(No.20050222);; 福建省科技项目(No.2005HZ1019);; 厦门市科技局资助项目(No.3502Z20055010

半导体材料研究的新进展

首先对作为现代信息社会的核心和基础的半导体材料在国民经济建设、社会可持续发展以及国家安全中的战略地位和作用进行了分析，进而介绍几种重要半导体材料如，硅材料、GaAs和InP单晶材料、半导体超晶格和量子阱材料、一维量子线、零维量子点半导体微材料、宽带隙半导体材料、光学微腔和光子晶体材料、量子比特构造和量子计算机用材料等目前达到的水平和器件应用概况及其发展趋势作了概述。最后，提出了发展我国半导体材料的建议。本文未涉及II－VI族宽禁带 与II－VI族窄禁带红外半导体材料、高效太阳电池材料Cu(In,Ga)Se_2、CuIn(Se,S)等以及发展迅速的有机半导体材料等

半导体材料研究的新进展（续）

光学微腔是指具有高品质因子而尺寸与谐振光波长（1）相比拟的光学微型谐振器。随着MBE、MOCVD生长技术和现代微细加工技术发展，设计、制造有实用价值的光学微腔已成为可能，关在低（无）阈值激光器研制方面取得了很大进展。大家知道，当光腔尺度与光波长可比拟时，腔内真空场的光学模式数则大大减小（1个光学模式占有相当于(λ／2n)~3大小体积，n为介质有效折射率)。在理想情况下，若用一个边长为半波长，周界为全反射壁的立方微腔，有可能将一个单模光场分离出来，这为实现低（无）阈值激光器的研制提供了科学依据