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Simultaneous scanning ion conductance and atomic force microscopy with a nanopore: Effect of the aperture edge on the ion current images
摘要： Scanning ion conductance microscopy (SICM) is a technique for high-resolution non-contact imaging, particularly powerful for live cell studies. Despite debates on its lateral resolution, consensus is that a probe presenting a tip with small opening aperture, large opening angle, and large outer-to-inner radius ratio will offer a SICM current signal more sensitive to tip-sample separation, ultimately impacting the image resolution. We report here the design of such a probe, integrating a nano-opening (<20 nm opening diameter) with increased outer-to-inner radius ratio and a wide opening angle through microfabrication and ion milling. The probe consists of a microfluidic atomic force microscopy (AFM) cantilever offered by the Fluid Force Microscope (FluidFM) technology, able to act as an SICM and AFM probe. Such a combination allows investigating the implications of the new probe geometry on the SICM imaging process by simultaneously recording currents and forces. We demonstrate through experiments on well-defined samples as well as corresponding simulations that by integrating a nanopore onto the FluidFM, nanoscale features could be successfully imaged, but the increased sensitivity of the probe current to sample distance comes with higher sensitivity to an inherent SICM wall artefact.
关键词： nanopore,ion current images,Scanning ion conductance microscopy,FluidFM,atomic force microscopy
更新于2025-09-23 15:21:21
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CoGe surface oxidation studied using X-ray photoelectron spectroscopy
摘要： Cobalt germanides have been widely studied as semiconductor contact materials, but recent theoretical studies suggest that they may also be excellent catalysts for methane steam reforming with stabilities and activities comparable to more expensive noble metal catalysts. We have sputter deposited CoGe alloy films and characterized their structure and morphology after post-deposition annealing in high vacuum up to 1000 °C. We used X-ray photoelectron spectroscopy to study the initial oxidation of amorphous and crystalline CoGe alloy surfaces under low pressures of O2 and H2O. The oxidation rate in O2 was found to be faster for an amorphous CoGe surface compared to a crystalline surface. We also found that there was little difference in the oxidation rate in H2O for either amorphous or crystalline surfaces. During O2 oxidation, the crystalline surface preferentially forms GeO and the amorphous surface preferentially forms GeO2. We have also observed preferential oxidation of Ge in the CoGe thin films. During temperature programmed desorption studies, we found that GeO desorption begins near 350 °C and that GeO2 decomposes to GeO and desorbs near 700 °C. More studies of CoGe catalysts are warranted, however GeO desorption may be a concern under reaction conditions when the film is subjected to an oxidizing environment.
关键词： Oxidation,Cobalt germanium,Temperature programmed desorption,Atomic force microscopy,X-ray photoelectron spectroscopy,X-ray diffraction
更新于2025-09-23 15:21:21
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Structural identification of silicene on the Ag(111) surface by atomic force microscopy
摘要： Silicene is a two-dimensional atomic layer material with buckled honeycomb arrangements of Si atoms. The diversity of those arrangements, which expands its potential applications, makes it dif?cult to determine its structure in any particular case. In this paper, we show that atomic force microscopy (AFM) has the capability of structural determination of unknown phases of silicene. We carried out an AFM observation of (√13×√13)R13.9? silicene of unknown structures on Ag(111). Remarkably, it was shown that all constituent Si atoms forming a honeycomb lattice can be resolved by AFM whereas scanning tunneling microscopy (STM) can image only the topmost Si atoms. High-resolution AFM imaging allowed us to identify two types of buckled structure of (√13×√13)R13.9? silicene on Ag(111), which had not been previously discriminated. The structure models obtained by theoretical simulation reproduced AFM images as well as previous STM images. In addition, the mechanism of high-resolution AFM imaging was elucidated by force spectroscopy combined with ?rst-principles calculations. Namely, attractive interaction with the tip pulls up buckled down Si atoms, causing local ?ips of the buckled structures.
关键词： structural determination,buckled structures,Ag(111) surface,silicene,atomic force microscopy
更新于2025-09-23 15:21:21
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Preferred orientation of 2,7-dioctyl[1]benzothieno[3,2- <i>b</i> ][1]benzothiophene molecules on inorganic single-crystal substrates with various orientations
摘要： The organic molecule 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) was deposited on quartz glass, e11 (cid:2)20T A-, (0001) C-, and e1 (cid:2)102T R-single-crystal Al2O3 (sapphire), and (100)-, and (111)-single-crystal MgO substrates by vacuum thermal evaporation, and structural characterizations were carried out by X-ray di?raction analysis and atomic force microscopy (AFM) observation. The (001) out-of-plane orientation with a similar in-plane orientation was obtained irrespective of the substrate material and orientation, and its formation was governed by π–π-stacking-induced molecular ordering. The degree of orientation was re?ected by the grain structure related to the substrate material. The growth model of the oriented C8-BTBT layer was speculated on the basis of experimental results.
关键词： π–π-stacking,vacuum thermal evaporation,X-ray diffraction,C8-BTBT,atomic force microscopy
更新于2025-09-23 15:21:21
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Atomic Force Microscopy in Molecular and Cell Biology || Assessment of Pathological or Drug-Dependent Changes in Cell Membrane Morphology and Cell Biomechanical Properties by Atomic Force Microscopy
摘要： Identification of the nanoscale changes that take place in cell membrane (CM) morphology or cell biomechanical properties (CBPs) in disease states or in response to drug treatment enable for a better understanding of the effects of the drugs on disease pathogenesis and recovery. CM proteins and CBPs have a crucial role in the regulation of many physiological and pathological processes. Direct assessment of the CM and CBPs is therefore useful not only for a better appreciation of cell structure but also for a better understanding of cell pathophysiology. Atomic force microscopy (AFM) is a technique that can be employed to assess CM structure and CBPs at the nanometer scale. In the first part of this chapter, we describe the principles of AFM and appraise its value in the assessment of CM morphology and CBPs. In the second part, we review examples of disease- or drug- dependent changes in CM morphology and CBPs that have been elucidated using AFM.
关键词： Nanoscale,Atomic force microscopy,Cell membrane
更新于2025-09-23 15:21:21
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Frictional Characteristics of Suspended MoS <sub/>2</sub>
摘要： Molybdenum disulfide (MoS2), a booming layered two-dimensional (2D) nanomaterial, has gain intensive interests for its remarkable physical properties. In this work, the friction characteristics of suspended MoS2 are systematically investigated with atomic force microscopy (AFM). The friction on the suspended MoS2 is much larger than that on the supported MoS2 because of the softening bending rigidity and easier formation of puckering at the AFM tip-MoS2 contact interface, and the difference would increases with the applied load. Similar to the supported MoS2, the friction on the suspended MoS2 also decreases with the increasing layers because of the enhanced bending rigidity. The friction on the suspended MoS2 is relatively insensitive to the shapes of holes below but sensitive to the dimensions. This work can provide beneficial guidance for the diverse design requirements of MoS2-based nanoelectromechanical devices.
关键词： friction,suspended,Molybdenum disulfide,puckering effect,bending rigidity,AFM,atomic force microscopy,MoS2,supported
更新于2025-09-23 15:21:21
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Atomic Force Microscopy in Molecular and Cell Biology || AFM Imaging-Force Spectroscopy Combination for Molecular Recognition at the Single-Cell Level
摘要： Molecular recognition at the single-cell level is an increasingly important issue in Biomedical Sciences. With atomic force microscopy, cell surface receptors may be recognized through the interaction with their ligands, inclusively for the identification of cell-cell adhesion proteins. The spatial location of a specific interaction can be determined by adhesion force mapping, which combines topographic images with local force spectroscopy measurements. Another valuable possibility is to simultaneously record topographic and recognition images (TREC imaging) of cells, enabling the mapping of specific binding events on cells in real time. This review is focused on recent developments on these molecular recognition approaches, presenting examples of different biological and biomedical applications.
关键词： Molecular recognition,TREC imaging,Atomic force microscopy,Adhesion force mapping,Biomedical applications
更新于2025-09-23 15:21:01
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Role of microstructure and structural disorder on tribological properties of polycrystalline diamond films
摘要： Polycrystalline diamond films with systematic change in microstructure that varies from microcrystalline to nanocrystalline structure are synthesized on Si by hot filament chemical vapor deposition. The morphology and structural properties of the grown diamond films are analyzed using field emission scanning electron microscope (FESEM), atomic force microscope (AFM), X-ray diffraction and Raman spectroscopy. The average roughness and grain size of the diamond films decrease with increase in CH4 to H2 ratio from 0.5 to 3%. Also, structural disorder in these diamond films increases with decrease in grain size as evidenced from Raman spectroscopy. The coefficient of friction (CoF) is found to be very low for all the films. However, the average CoF is found to increase from 0.011 ± 0.005 to 0.03 ± 0.015 as the grain size decrease from ～1 μm down to ～20 nm. Post analysis of wear track by FESEM, AFM based nanoscale friction and Raman spectroscopy reveal that microcrystalline diamond undergoes shear induced amorphization with negligible wear rate while nanocrystalline diamond films undergo shear induced plastic deformation without amorphization. A comprehensive mechanism for the observed CoF is discussed in the framework of microstructure, structural disorder and shear induced tribo-chemical reactions at the sliding interface.
关键词： Raman spectroscopy,Tribology,Diamond,Scanning electron microscopy,Hot filament CVD,Atomic force microscopy
更新于2025-09-23 15:21:01
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Imaging Dye Aggregation in MK-2, N3, N749, and SQ-2 dye?·?·?·TiO <sub/>2</sub> Interfaces That Represent Dye-Sensitized Solar Cell Working Electrodes
摘要： Dye-sensitized solar cells (DSSCs) are a strong contender for next-generation photovoltaic technology with niche applications as solar-powered windows. The performance of a DSSC is particularly susceptible to the dye sensitizer, which is adsorbed onto the surface of a wide-band-gap semiconductor such as TiO2, to form the working electrode. The nature by which such surfaces are sensitized stands to influence the resulting dye···TiO2 interfacial structure and thence the operational performance of the DSSC working electrode. In particular, a nanoscopic understanding of the sensitization process would ultimately help to improve DSSC device function. In this study, atomic force microscopy (AFM) is used to image the nanoscopic formation of dye···TiO2 interfacial structures. This employs, as case studies, four well-known DSSC dyes adsorbed onto amorphous TiO2 substrates: two ruthenium-based dyes, N3 and the Black Dye (N749); and two organic dyes, the thiophenylcarbazole, MK-2, and the zwitterionic squaraine, SQ-2. We discover that all four dyes present some form of aggregation upon sensitization of TiO2, whose spatial distributions show distinct nanoaggregate particle characteristics. These particle clusters of N749, N3, and MK-2 are found to assemble in lines of nanoaggregates, while clusters of SQ-2 dye chromophores distribute themselves randomly on the amorphous TiO2 substrates. This nanoparticle structural assembly persists even when these dye···TiO2 interfaces are fabricated using hundred-fold diluted dye sensitization concentrations. The formation of dye aggregates in N749 is further studied as a function of dye sensitization time. This tracks the pattern formation of aggregates of N749 and reveals that dye aggregation begins within the first hour and has completed within a 5 h period. The large expanse of dye nanoaggregates observed shows that dye···dye interactions are much more important than previously envisaged, while the nature of their spatial distribution can be related to different aggregation modes of the dye molecules. These nanostructural features will undoubtedly impact the performance of DSSCs.
关键词： aggregation,N749,dye-sensitized solar cell,atomic force microscopy,N3,SQ-2,MK-2
更新于2025-09-23 15:21:01
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Diversity of physical properties of bacterial extracellular membrane vesicles revealed through atomic force microscopy phase imaging
摘要： Bacteria release nanometer-scale extracellular membrane vesicles (MVs) to mediate a variety of biological processes. We analyzed individual MVs under physiological conditions by phase imaging of high-speed atomic force microscopy to assess the physiological heterogeneity of MVs isolated from bacterial cultures. Phase imaging makes it possible to map the physical properties of an individual, fragile MV in an isolated MV population containing a broad variety of vesicle diameters, from 20 to 150 nm. We also developed a method for quantitatively comparing the physical properties of MVs among samples. This allowed for the comparison of the physical properties of MVs isolated from different bacterial species. We compared bacterial MVs isolated from four bacterial species and artificially synthesized liposomes. We demonstrate that each bacterial species generates physically heterogeneous types of MVs, unlike the physical homogeneity displayed by liposomes. These results indicate that the physical heterogeneity of bacterial MVs is mainly caused by compositional differences mediated through biological phenomena and could be unique to each species. We provide a new methodology using phase imaging that would pave the way for single-vesicle analysis of extracellular vesicles of a broad size range.
关键词： heterogeneity,atomic force microscopy,physical properties,phase imaging,bacterial extracellular membrane vesicles
更新于2025-09-23 15:21:01