原子力显微镜观察脂胞囊形貌结构及稳定性

用原子力显微镜(AFM)观察了液晶态脂胞囊形貌结构和稳定性.实验结果显示,对于1,2-二油酸甘油-3-磷脂酰乙醇胺(DOPE)超分子聚集体,在扫描区域内,可观察到一些大小不同球形颗粒;对于1,2-二油酸甘油-3-磷脂酸乙醇胺(DOPE)和1,2-二油酸甘油-3-磷脂酰胆碱(DOPC)混合的超分子聚集体,则不仅观察到类似脂胞囊的球形颗粒,而且也观察到了双层膜结构,其厚度约为5～6 nm.     

磁控溅射Al膜的AFM性能分析及其制备工艺研究

用原子力显微镜(AFM)对直流溅射和射频溅射制备铝膜的表面粗糙度及颗粒大小进行了分析比较.实验结果表明:溅射功率和溅射时间对铝膜表面粗糙度有影响,通过延长溅射时间或提高溅射功率可使膜的平均颗粒直径增大.     

萘酞菁LB膜取向液晶研究

利用二(3-叔丁基硅氧基)萘酞菁硅 (SiNc) Langmuir-Blodgett (LB) 膜对丝状液晶的定向进行了研究,发现在不同膜压下沉积的SiNc LB膜具有不同的定向效果.在15mN/m低膜压下沉积的LB膜上丝状液晶主要呈沿膜面水平排列,而30mN/m高膜压下沉积的LB膜则取垂直膜面取向.原子力显微镜(AFM)对相应的LB单层膜和多层膜进行的分子尺度上的形貌研究发现,高膜压条件下SiNc分子以分离的单体或聚集体形式非连续地在基片上呈线性堆积排列,形成一定的分子“纳米线”,并且大环平面垂直于基片 关键词：     

过渡金属表面γ-氨丙基三甲氧基硅烷膜的研究

本文对在过渡金属铁、镍电极表面制备得到的γ-氨丙基三甲氧基硅烷(γ-APS)膜进行了研究。实验中对硅烷膜用X-射线光电子能谱(XPS)、现场表面增强拉曼散射光谱(SERS)和原子力显微镜(AFM)进行了表征。X-射线光电子能谱(XPS)的结果发现存在两个N1s峰,表明γ-APS膜中的氨基有两种存在方式:自由氨基和质子化氨基。实验中还发现现场表面增强拉曼散射光谱(SERS)是研究金属/γ-APS体系中界面层结构非常有效的手段,SERS结果表明硅醇羟基和氨基发生了竞争吸附,且γ-APS分子在外加电位等条件的影响下吸附状态会发生一定变化。原子力显微镜(AFM)的表征结果在微观上显示电极表面的γ-APS膜上形成了一种较规则的微孔结构,这种结构可能与基底的性质有关。     

神经节苷脂的红外、紫外光谱分析及其多聚体结构的原子力显微镜观测

神经节苷脂(gangliosides, Gls)是一类含有唾液酸的酸性鞘糖脂,是神经细胞膜的重要组成成分,在生物膜中起着非常重要的生理作用。文章用红外光谱(IR)、紫外光谱(UV)、原子力显微镜(AFM)分别对以牛脑为原料,采用Folch萃取法、硅胶吸附柱层析和DEAE-SephadexA-25离子交换柱层析得到的神经节苷脂的分子官能团和多聚体结构进行了研究。实验结果表明,从100 g湿组织中获得产品为55.2 mg,纯度达62.84%,其紫外光谱吸收在195 nm处。通过红外光谱研究证明在提纯的产品结构中含有唾液酸分子的结构片段。利用原子力显微镜对其在水中的聚集体微观形貌进行了观察研究,发现神经节苷脂在水中呈清晰的纳米级球状或椭球状结构,经测定：神经节苷脂多聚体的大小在55～380 nm之间,平均大小为(148.9±66.7) nm;高度在1.0～5.0 nm之间,平均高度为(3.25±1.01) nm。该实验结果为神经节苷脂的生物活性研究以及作为神经类药物的开发利用提供了理论和实验依据。     

液晶态油酸脂质体与生物膜相互作用的理化特性

用小角Ｘ射线散射用法和 ^３１Ｐ核磁共振技术，对抗癌新药——液晶态油酸多相脂质体的结构进行了研究。实验结果表明：胆固醇、油酸、非离子表面活性剂均对ＰＥ脂质体液晶态的结构有显著的影响。在含有高效分散剂的磷酸盐缓冲溶液中制成的液晶态油酸多相脂质体由片层六角相和片层立方相组成。电子自旋共振研究表明，这种结构的脂质体与Ｅ_ｃ腹水肝癌细胞相互作用的结果使Ｗ／Ｓ值增加。 关键词：     

扫描探针显微学在材料表面纳米级结构研究中的新进展

应用扫描探针显微技术（ＳＰＭ）「包括扫描隧道显微镜（ＳＴＭ）、原子力显微镜（ＡＦＭ）、磁力显微镜（ＭＦＭ）等」,比较系统地研究了一些无机、有机和生物材料的表面精细结构;在极高分辨率的水平上,解释了如Ｃ６０Ｌａｎｇｍｕｉｒ－Ｂｌｏｄｇｅｔｔ膜、有机磁性薄膜的样品制备、形成条件的关系;研究并揭示了碱金属与半志体表面吸附相互作用,红细胞表面结构等;拓宽了扫描探针显微技术的范围,在实验方法和研究成果上具有     

原子力显微镜研究DPPC磷脂多层膜结构与力学性能

应用原子力显微镜(AFM)首先研究了在蔗糖溶液中二棕榈酰磷脂酰胆碱(DPPC)磷脂双层膜的结构,分析了其力学性能;其次,研究了在纯水中、CaCl2溶液中的DPPC磷脂多层膜的结构特性和杨氏模量.实验结果表明,在CaCl2溶液中DPPC多层膜的水层厚度大于在纯水中厚度,在CaCl2溶液中多层膜的杨氏模量变小.     

用液流操纵单个DNA分子形成纳米悬链线图形

首先用液流拉伸单分子DNA,使其吸附在修饰过的云母基片上.然后让二次液流沿着垂直于已拉伸的DNA的方向流过云母片,用原子力显微镜(AFM)观测,可见DNA单分子片段在基片上形成了一些纳米尺度的悬链线.提出一种“S悬桥”模型能定量地解释这一现象.该研究工作揭示,在DNA的单分子操作中,经典的弹性力学理论足以描述和控制DNA分子二维图形的形成 关键词： DNA 单分子DNA操纵 原子力显微镜(AFM) 纳米悬链线     

氮对类金刚石薄膜的微观结构内应力与附着力的影响

采用原子力显微镜(AFM)、俄歇电子能谱(AES)和显微压痕分析等手段对射频等离子体增强化学气相沉积法制备的掺氮类金刚石(DLC：N)薄膜的微观结构和力学性能进行了研究.结果表明,随着含氮量的增加,DLC薄膜的AFM表面形貌中出现了几十纳米的颗粒,原子侧向力显微镜和AES分析表明这种纳米颗粒是x大于0.126的非晶氮化碳CN_x结构.这种非晶DLC/CN_x的纳米复合结构,减小了薄膜的内应力,从而提高了薄膜与衬底的附着力. 关键词： 类金刚石碳膜 微观结构 附着特性     

Lipid membrane: inelastic deformation of surface structure by an atomic force microscope

The stability of the 1,2-Dioleoyl-sn-Glycero-3-[phospho-rac-1-Glycerol-Na] liposome in the liquid crystalline state have been investigated using an atomic force microscope (AFM). We have observed the inelastic deformation of the sample surface. The AFM tip causes persistent deformation of the surface of the lipid membrane, in which some of the lipid molecules are eventually pushed or dragged by the AFM tip. The experiment shows how the surface structure of the lipid membrane can be created by the interaction between the AFM tip and lipid membrane. When the operating force exceeds 10^-8 N, it leads to large deformations of the surface. A square region of about 1×1μm² is created by the scanning probe on the surface. When the operating force is between 10^-11N and 10^-8N, it can image the topography of the surface of the lipid membrane. The stability of the sample is related to the concentration of the medium in which the sample is prepared.     

Quantitative atomic force microscopy with carbon monoxide terminated tips

Noncontact atomic force microscopy (AFM) has recently progressed tremendously in achieving atomic resolution imaging through the use of small oscillation amplitudes and well-defined modification of the tip apex. In particular, it has been shown that picking up simple inorganic molecules (such as CO) by the AFM tip leads to a well-defined tip apex and to enhanced image resolution. Here, we use the same approach to study the three-dimensional intermolecular interaction potential between two molecules and focus on the implications of using molecule-modified AFM tips for microscopy and force spectroscopy experiments. The flexibility of the CO at the tip apex complicates the measurement of the intermolecular interaction energy between two CO molecules. Our work establishes the physical limits of measuring intermolecular interactions with scanning probes.     

Theoretical Study on the Capillary Force between an Atomic Force Microscope Tip and a Nanoparticle

Considering that capillary force is one of the most important forces between nanoparticles and atomic force microscope （AFM） tips in ambient atmosphere, we develop an analytic approach on the capillary force between an AFM tip and a nanoparticle. The results show that the capillary forces are considerably affected by the geometry of the AFM tip, the humidity of the environment, the vertical distance between the AFM tip and the nanoparticle, as well as the contact angles of the meniscus with an AFM tip and a nanoparticle. It is found that the sharper the AFM tip, the smaller the capillary force. The analyses and results are expected to be helpful for the quantitative imaging and manipulating of nanoparticles by AFMs.     

AFM针尖-测试面接触分子动力学研究

针对AFM针尖-测试面的接触问题,利用分子动力学模拟针尖同测试面间的"跳跃粘附"和"颈缩分离"过程;分析接触力同接触间隙的关系及测试面压力分布;发现分离过程滞后粘附过程;得到接触力大小只与接触区域附近少数原子层有关,且接触区域近处原子受压力、远处受拉力的结论;讨论测试面位错半径同接触力和接触间隙的关系.     

新型原子力显微镜的研制及其应用

研制了一种新型卧式原子力显微镜(AFM)系统.本文介绍卧式AFM的工作原理及其简要结构,讨论反馈控制电路系统的优化设计,阐述Windows/Dos兼容的图象扫描、处理和显示软件.基于原子力曲线的测定,利用AFM对纳米金刚石薄膜和多孔氧化铝进行了扫描检测.实验表明,该AFM系统具有十分良好的图象重复性、稳定性和衬比(度),仪器的横向分辨率优于3nm,纵向分辨率可达1nm,最大扫描范围达到5μm×5μm.这些性能为卧式AFM在更广泛的纳米技术领域的应用奠定了基础.     

Tip cleaning and sharpening processes for noncontact atomic force microscope in ultrahigh vacuum

Tip cleaning and sharpening processes for noncontact atomic force microscope (AFM) operated in ultrahigh vacuum (UHV) were carried out and evaluated by a scanning Auger microscope (SAM) with a field emission electron gun and a noncontact AFM in UHV combined with a scanning tunneling microscope and a field emission microscope. The cantilever used in this study was piezoresistive, which can be heated by passing a current through the resistive legs of the cantilever. As a pretreatment, the tip was irradiated with ultraviolet light in oxygen to remove carbon contaminants. It was heated at about 750°C to form a clean oxide layer in oxygen of 5×10⁻⁵ Torr in an SAM chamber. The desorption of the layer can make a remained tip apex sharper by heating under electron beam irradiation. A thermally oxidized layer was also eliminated by HF etching to sharpen the tip apex. The procedures are useful to obtain a well-defined Si tip suitable for a noncontact AFM.     

Hard disk magnetic domain nano-spatial resolution imaging by using a near-field scanning microwave microscope with an AFM probe tip

A near-field scanning microwave microscope (NSMM) incorporating an atomic force microscope (AFM) probe tip was used for the direct imaging of magnetic domains of a hard disk under an external magnetic field. We directly imaged the magnetic domain changes by measuring the change of reflection coefficient S₁₁ of the NSMM at an operating frequency near 4.4 GHz. Comparison was made to the magnetic force microscope (MFM) image. Using the AFM probe tip coupled to the tuning fork distance control system enabled nano-spatial resolution. The NSMM incorporating an AFM tip offers a reliable means for quantitative measurement of magnetic domains with nano-scale resolution and high sensitivity.     

Modification of AFM Tips for Facilitating Picking-up of Nanoparticles

The radius of atomic force microscope (AFM) tip is a key factor that influences nonspecific interactions between AFM tip and nanoparticles. Generally, a tip with larger radius contributes to a higher efficiency of picking up nanoparticles. We provide two methods for modifying the AFM tip: one is to wear a tip apex on a solid substrate and the other is to coat a tip with poly (dimethylsiloxane) (PDMS). Both the approaches can enhance the adhesion force between the tip and nanoparticles by increasing tip radius. The experimental results show that a modified tip, compared to an unmodified one, achieves six-fold efficiency improvement in the capture of targeted colloidal gold nanoparticles.     

Theory of higher harmonics imaging in tapping-mode atomic force microscopy

The periodic impact force induced by tip-sample contact in tapping mode atomic force microscope (AFM) gives rise to non-harmonic response of a micro-cantilever. These non-harmonic signals contain the full characteristics of tip-sample interaction. A complete theoretical model describing the dynamical behaviour of tip--sample system was developed in this paper. An analytic formula was introduced to describe the relationship between time-varying tip--sample impact force and tip motion. The theoretical analysis and numerical results both show that the time-varying tip--sample impact force can be reconstructed by recording tip motion. This allows for the reconstruction of the characteristics of the tip--sample force, like contact time and maximum contact force. It can also explain the ability of AFM higher harmonics imaging in mapping stiffness and surface energy variations.     

Imitation of non-contact mode while scanning in the presence of an electric double layer?

Non-contact atomic force microscopy (NCAFM) minimizes the physical interaction between the AFM tip and the surface of interest. Several recent studies have reported observation of single atom defects using this technique. The repulsive force is presumably the primary interatomic force (cf. our paper on pseudo-non-contact mode in this issue) responsible for the reported atomic resolution in these studies. The combination of these factors, minimal tip–sample deformation and repulsive force interaction, are responsible for the observation of the single atom defects. In the present study, we show that similar resolution can be achieved utilizing the same two factors but which employs scanning in a surfactant. The method decreases the tip–sample interaction by eliminating the attractive forces between the tip and sample. The surfactant solution induces an electrical double-layer (EDL) on the surface of the tip and sample. This EDL creates additional repulsion that is distributed over a large area, and hence does not contribute noticeably to the image contrast during scanning. However, it does compensate for the high pressures normally experienced by the tip in the absence of surfactant. In addition, the presence of the EDL enhances tip stability during the image scan. This method has been tested on surfaces of such minerals as mica, chlorite, and anhydrite.