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基于锗衬底在石墨烯生长方面的自限制生长和表面催化特性,以甲烷(CH4)和氢气(H2)为前驱体,采用化学气相沉积(CVD)法分别在锗硅碳(SixGe1-xC0.02)(x=0.15,0.25,0.73)衬底和外延锗上直接生长石墨烯.研究了不同Si组分、H2与CH4体积流量比和生长温度对石墨烯质量的影响.利用光学显微镜(OM)、扫描电子显微镜(SEM)以及喇曼光谱对衬底和生长的石墨烯进行了表征分析.喇曼光谱结果表明,Si0.5Ge0.85C0.02衬底在750℃下可以生长出石墨烯,调节气体H2与CH4的体积流量比为50∶0.5时,生长出的石墨烯是双层的.OM和SEM结果表明,锗硅碳衬底具有比锗更好的热稳定性,高温下不会升华. 相似文献
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通过高温热解法和化学气相沉积(CVD)法在SiC(0001)衬底外延石墨烯。采用光学显微镜、原子力显微镜、扫描电子显微镜、喇曼光谱、X射线光电子能谱和霍尔测试系统对样品进行表征,并对比了两种不同生长方法对石墨烯材料的影响以及不同的成核机理。结果表明,高温热解法制备的石墨烯材料有明显的台阶形貌,台阶区域平坦均匀,褶皱少,晶体质量取决于SiC衬底表面原子层,电学特性受衬底影响大,迁移率较低。CVD法制备的石墨烯材料整体均匀,褶皱较多,晶体质量更好。该方法制备的石墨烯薄膜悬浮在SiC衬底表面,与衬底之间为范德华力连接,电学特性受衬底影响小,迁移率较高。 相似文献
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《电子元件与材料》2017,(1):33-37
基于等离子体增强化学气相沉积法、干法刻蚀技术、化学气相沉积法及腐蚀基底法,制备了一种新型石墨烯与多孔氮化硅复合材料;该结构的氮化硅衬底具有不同的形貌结构(孔阵列及沟道阵列)。利用扫描电子显微镜、原子力显微镜、拉曼光谱仪对石墨烯/多孔氮化硅复合材料进行表征和表面应力特性研究。结果表明:不同形貌结构的氮化硅与石墨烯复合后的表面应力不同。表面粗糙度、表面形貌及表面面积是影响复合材料表面应力的主要因素。其中,氮化硅多孔形貌结构(应变0.1%~0.12%)与氮化硅沟道形貌结构(应变0.16%~0.27%)相比,更有利于缓解石墨烯/多孔氮化硅复合材料的表面应力集中问题。 相似文献
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采用化学气相沉积(CVD)法,以铜箔为衬底,以甲烷为碳源,制备了石墨烯薄膜和单晶畴,并利用扫描电子显微镜、光学显微镜、喇曼光谱仪、紫外-可见透过光谱仪等手段对石墨烯进行了系统表征。结果表明,质量分数为10%的稀硝酸对铜箔表面进行腐蚀处理20 s可以有效去除铜箔表面析出的杂质颗粒,从而提高石墨烯的质量。在此基础上,研究了氢气和甲烷体积流量比对石墨烯生长的影响,当氢气和甲烷体积流量比从0∶1变化到5∶1时,石墨烯薄膜从单层生长变化到多层生长。此外,氢气和甲烷体积流量比也会显著影响晶畴的形状,随着氢气和甲烷体积流量比的增加,石墨烯晶畴从无规则形状逐渐变化到六边形。 相似文献
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Ultrastructure and behavior of actin cytoskeleton during cell wall formation in the fission yeast Schizosaccharomyces pombe 总被引:1,自引:0,他引:1
Fluorescence microscopy has shown that F-actin of the fission yeast Schizosaccharomyces pombe forms patch, cable and ring structures. To study the relationship between cell wall formation and the actin cytoskeleton, the process of cell wall regeneration from the protoplast was investigated by transmission electron microscopy (TEM), immunoelectron microscopy (IEM) and three-dimensional reconstruction analysis. During cell wall regeneration from the protoplast, localization of F-actin patches was similar to that of the newly synthesized cell wall materials, as shown by confocal laser scanning microscopy (CLSM). In serial sectioned TEM images, filasomes were spherical, 100-300 nm in diameter and consisted of a single microvesicle (35-70 nm diameter) surrounded by fine filaments. Filasomes were adjacent to the newly formed glucan fibrils in single, cluster or rosary forms. By IEM analysis, we found that colloidal gold particles indicating actin molecules were present in the filamentous area of filasomes. Three-dimensional reconstruction images of serial sections clarified that the distribution of filasomes corresponded to the distribution of F-actin patches revealed by CLSM. Thus, a filasome is one of the F-actin patch structures appearing in the cytoplasm at the site of the initial formation of the cell wall and it may play an important role in this action. 相似文献
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Fujiwara T Shimizu D Kon K Isshiki N Tsunokuni H Aoyagi S 《Journal of electron microscopy》2000,49(4):551-558
Cell marking is widely used to examine cell development and differentiation in developmental biology. We developed a new method for localizing cell markers in a semi-thin epoxy section with scanning electron microscopy. Cultured fibroblasts ingesting carbon particles were autologously transplanted into a rabbit transparent ear chamber, 6 mm in diameter and 100 microm in depth. Eight days after the transplantation, tissues in the chamber were fixed and embedded in epoxy resin. Semi-thin sections were cut and stained with toluidine blue. Fibroblasts in connective tissues which contained black spots were observed with a light microscope. These sections were subsequently ion-etched with an ion-coater and coated with platinum. The same fibroblasts were then visualized by secondary electron imaging using a scanning electron microscope. A nucleus with nuclear envelope, nuclear pores, a nucleolus and heterochromatin, mitochondria with cristae and rough endoplasmic reticulum were observed in the fibroblasts. The black spots in the fibroblasts were identified as bright bodies with the scanning electron microscope. The bright bodies were found to be a lump of tiny particles less than 100 nm in diameter. In order to analyse such particles with energy dispersive X-ray microanalysis, ion-etched sections were coated with carbon. X-ray energy spectrometry clearly demonstrated that these were carbon particles, which had been endocytosed by the fibroblast. This suggests that scanning electron microscopy combined with energy dispersive X-ray microanalysis is useful for detecting carbon particles in the cytoplasm at an ultrastructural level in semi-thin epoxy sections subsequent to ion etching and that this method may be applicable to other cell markers, such as gold particles to track cells in the field of cell development and cell differentiation. 相似文献
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Cristina Martín Amalia Ruiz Sandeep Keshavan Giacomo Reina Diane Murera Yuta Nishina Bengt Fadeel Alberto Bianco 《Advanced functional materials》2019,29(39)
The design of multifunctional materials able to both selectively deliver a drug into cells in a targeted manner and display an enhanced propensity for biodegradation is an important goal. Here, graphene oxide (GO) is functionalized with the chemotactic peptide N‐formyl‐methionyl‐leucyl‐phenylalanine (fMLP) known to interact with the formyl peptide receptor, which is expressed in different cancer cells, including cervical carcinoma cells. This study highlights the ability of GOfMLP for targeted drug delivery and cancer cell killing and the subsequent degradation capacity of the hybrid. Biodegradation is assessed via Raman spectroscopy and transmission electron microscopy. The results show that GOfMLP is susceptible to faster myeloperoxidase‐mediated degradation. The hybrid material, but not GO, is capable of inducing neutrophil degranulation with subsequent degradation, being the first study showing inducible neutrophil degradation by the nanomaterial itself with no prior activation of the cells. In addition, confocal imaging and flow cytometry using HeLa cells demonstrate that GOfMLP is able to deliver the chemotherapeutic agent doxorubicin faster into cells, inducing higher levels of apoptosis, when compared to nonfunctionalized GO. The results reveal that GOfMLP is a promising carrier able to efficiently deliver anticancer drugs, being endowed with the ability to induce its own biodegradation. 相似文献
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Virendra V. Singh Garima Gupta Anirudh Batra Anil K. Nigam Mannan Boopathi Pranav K. Gutch Brajesh K. Tripathi Anchal Srivastava Merwyn Samuel Gauri S. Agarwal Beer Singh Rajagopalan Vijayaraghavan 《Advanced functional materials》2012,22(11):2352-2362
A green, simple, and cost effective electrochemical method to synthesize pure graphene oxide (GO) and graphene nanosheets (GNs) using pencil in ionic liquid medium is reported. The morphology and microstructure of prepared GNs and GO are examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X‐ray diffraction (XRD), and Raman spectroscopy; the experiments confirm the formation of high quality graphene. The synthesized GO is used for the real‐time and label‐free surface plasmon resonance (SPR) sensing of the biological warfare agent Salmonella typhi. 相似文献
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Matteo Di Giosia Iryna Polishchuk Eva Weber Simona Fermani Luca Pasquini Nicola M. Pugno Francesco Zerbetto Marco Montalti Matteo Calvaresi Giuseppe Falini Boaz Pokroy 《Advanced functional materials》2016,26(30):5569-5575
Composites, materials composed of two or more materials—metallic, organic, or inorganic—usually exhibit the combined physical properties of their component materials. The result is a material that is superior to conventional monolithic materials. Advanced composites are used in a variety of industrial applications and therefore attract much scientific interest. Here the formation of novel carbon‐based nanocomposites is described via incorporation of graphene oxide (GO) into the crystal lattice of single crystals of calcite. Incorporation of a 2D organic material into single‐crystal lattices has never before been reported. To characterize the resulting nanocomposites, high‐resolution synchrotron powder X‐ray diffraction, electron microscopy, transmission electron microscopy, fluorescence microscopy and nanoindentation tests are employed. A detailed analysis reveals a layered distribution of GO sheets incorporated within the calcite host. Moreover, the optical and mechanical properties of the calcite host are altered when a carbon‐based nanomaterial is introduced into its lattice. Compared to pure calcite, the composite GO/calcite crystals exhibits lower elastic modulus and higher hardness. The results of this study show that the incorporation of a 2D material within a 3D crystal lattice is not only feasible but also can lead to the formation of hybrid crystals exhibiting new properties. 相似文献
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电子显微镜(以下简称电镜)在生命科学研究中起到了非常重要的作用。随着电镜使用需求的日益扩大,对仪器管理也提出了新的要求。本文利用北京大学生命科学学院仪器中心电镜平台2010年及2017年安装的两台透射电镜的使用数据,详细分析每台电镜的使用时间、使用时长以及相应的用户,并通过描述统计的方法,对这些数据进行分析与整合,包括电镜使用的日内分布、周内分布以及用户群体的变化等。统计得出北京大学生命科学学院电镜平台用户更倾向于在工作时间使用电镜,同时电镜使用的寡头垄断及用户偏好粘性现象明显。建议通过鼓励培训独立用户、合理设计管理者工作时间以及设置设备使用费梯度等方式提高电镜的使用率。 相似文献
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Interactions between an Aryl Thioacetate‐Functionalized Zn(II) Porphyrin and Graphene Oxide
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Boyang Mao David G. Calatayud Vincenzo Mirabello Benjamin J. Hodges José Alberto Ribeiro Martins Stanley W. Botchway John M. Mitchels Sofia I. Pascu 《Advanced functional materials》2016,26(5):687-697
The surface modification of graphene oxide (GO) is carried out via the supramolecular functionalization route using a Zn(II)‐porphyrin which is soluble in common organic solvents on basis of long alkyl chains present at the exocyclic positions. This acts as a dispersing agent and decorates the surface of the graphene oxide uniformly, giving rise to a new nanohybrid denoted Zn(II)‐porphyrin@GO. The resulting Zn(II)‐porphyrin@GO nanohybrid forms a stable dispersion in ethanol (as characterized by several different spectroscopic techniques such as UV–vis, Fourier transform infrared, Raman). The morphology of Zn(II)‐porphyrin@GO nanohybrid is investigated by atomic force microscopy (AFM) and transmission electron microscope (TEM)/selected area electron diffraction. Both TEM and AFM measurements indicate that the Zn(II)‐porphyrin self‐assemble onto the surface of graphene oxide sheets. Steady‐state and time‐resolved fluorescence emission studies in the dispersed phase, and as a thin film, point toward the strongly quenched fluorescence emission and lifetime decay, suggesting that energy transfer occurs from the singlet excited state of Zn(II)‐porphyrin unit to GO sheets. 相似文献
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纳米金棒(AuNRs)具有众多独特的属性,已广泛运用于生物医学领域,但其是否具有潜在的生物危害尚有争议.作者运用了激光扫描共聚焦显微镜技术、western blotting技术和其他分子生物学方法从细胞氧化应激的角度探讨了AuNRs诱导A549细胞产生自噬的分子机制.研究结果表明,4μg·mL-1的AuNRs处理6 h能够诱导A549细胞自噬标志蛋白LC3-Ⅱ表达增加,LC3蛋白从细胞核转移至细胞质并形成自噬小泡.进一步研究发现,AuNRs能够降低A549细胞线粒体膜电位、ATP含量、UCP2蛋白表达水平以及细胞抗氧化能力并导致活性氧蓄积,后者可能最终引起细胞产生自噬.而10 mmol·L-1抗氧化剂NAC能够逆转上述线粒体及细胞功能的改变,并抑制自噬的发生.这一研究为深入认识其生物危害及可能机制提供了有力的实验证据. 相似文献
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Majczak A Karbowski M Kamiński M Masaoka M Kurono C Niemczyk E Kedzior J Soji T Knap D Hallmann A Wakabayashi T 《Journal of electron microscopy》2004,53(6):635-647
Effects of jasplakinolide (JSP), a stabilizer of F-actin, and latrunculin A (LTA), a destabilizer of F-actin, on a series of events occurring in the execution phase of staurosporine (STS)-induced apoptotic processes were studied using human osteosarcoma 143B cells. Time-dependent apparent increases of the population of cells with collapsed membrane potential of mitochondria (Delta Psi(m)) caused by STS treatment were not due to actual decreases in the Delta Psi(m) per cell, but due to the fragmentation of cells resulting in decreases in the number of active mitochondria per cell. Decreases in the Delta Psi(m) in fragmented cells occurred late in the execution phase. Both JSP and LAT failed to prevent STS-induced release of cytochrome c from mitochondria followed by the activation of caspases 3 and 9, the cleavage of poly (ADP-ribose) polymerase (PARP) and apoptotic nuclear fragmentation. However, both drugs prevented STS-induced apoptotic cell fragmentation and decreases in the Delta Psi(m). These results indicate that physicochemical states of actin filaments play a certain role in the execution phase of STS-induced apoptotic processes. 相似文献