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European Microscopy Congress 2016: Proceedings || In-situ E(S)TEM Observations of Single Atom Dynamics in Catalytic Reactions
摘要： In heterogeneous catalysis, single-atom catalysts (SACs) take place at the atomic level at elevated temperatures. Understanding and control of complex catalytic reactions on the atomic scale are crucial for the rational development of improved catalysts and processes. The development of the first atomic-scale resolution environmental transmission electron microscopy (ETEM) is described (1-5), opening up new opportunities for studying gas-solid reactions in real time (6-9). The in-situ observations in ETEM have revealed the direct visualization of reaction intermediates and processes on the atomic scale in real time (1-5), offering insights into the dynamic behavior of catalysts and processes. The development of the ETEM (2) is now used globally. Benefits of the in-situ studies include new knowledge, improved and more environmentally beneficial catalytic technology as well as better or replacement mainstrain technologies in chemical and energy industries. Examples of the in-situ studies include new gold, improved and more environmentally beneficial catalytic technology as well as better or replacement mainstrain technologies in chemical and energy industries. The new insights have important implications for the application of nanomaterials in chemical process technologies including for transportation fuels, transformation fuels and in ammonia manufacture (6). Recently supported noble metal catalysts are examined for low temperature water-gas shift (WGS) catalysts (Fig. 1) and compared with reaction data and modeling. The in-situ observations in WGS have revealed the formation of clusters of only a few atoms from single-atom catalysts and the catalytic effect of low coordination sites. The new insights have important implications for the application of nanomaterials in chemical process technologies.
关键词： gas-solid reactions,environmental transmission electron microscopy,catalysis,single-atom catalysts,in-situ observations
更新于2025-09-23 15:22:29
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Yellow-emissive carbon dots with a large Stokes shift are viable fluorescent probes for detection and cellular imaging of?silver ions and glutathione
摘要： Yellow-emissive carbon dots (Y-CDs) were prepared by a solvothermal method using anhydrous citric acid and 2,3-phenazinediamine as the starting materials. The Y-CDs display a 24% fluorescence quantum yield, a 188-nm Stokes’ shift and excellent stability. They are shown here to be excellent fluorescent probes for the determination of Ag(I) ion and glutathione (GSH). If exposed to Ag(I) ions, they are bound by the carboxy groups of the Y-CDs, and this causes quenching of fluorescence (with excitation/emission maxima at 380/568 nm) via a static quenching mechanism. This effect was used to design a fluorometric assay for Ag(I). The quenched fluorescence of the Y-CDs can be restored by adding GSH due to the high affinity of GSH for Ag(I). The calibration plot for Ag(I) is linear in the 1–4 μM Ag(I) concentration range, and the limit of detection is 31 nM. The respective values for GSH are 5–32 μM, and 76 nM, respectively. The method was applied to the detection of Ag(I) in spiked environmental water samples and gave recoveries ranging from 93 to 107%. It was also applied to the determination of GSH in tomatoes and purple grapes and gave satisfactory recoveries. The Y-CDs display low cytotoxicity and were successfully used to image Ag(I) and GSH in H1299 cells.
关键词： Fluorescence microscopy,Applications,Stern-Volmer plot,Fluorescence imaging,Fluorescence detection
更新于2025-09-23 15:22:29
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Image charge effect on the light emission of rutile TiO <sub/>2</sub> (110) induced by a scanning tunneling microscope
摘要： The plasmon-enhanced light emission of rutile TiO2(110) surface has been investigated by a low-temperature scanning tunneling microscope (STM). We found that the photon emission arises from the inelastic electron tunneling between the STM tip and the conduction band or defect states of TiO2(110). In contrast to the Au(111) surface, the maximum photon energy as a function of the bias voltage clearly deviates from the linear scaling behavior, suggesting the non-negligible effect of the STM tip on the band structure of TiO2. By performing differential conductance (dI/dV) measurements, it was revealed that such a deviation is not related to the tip-induced band bending, but is attributed to the image charge effect of the metal tip, which significantly shifts the band edges of the TiO2(110) towards the Femi level (EF) during the tunneling process. This work not only sheds new lights onto the understanding of plasmon-enhanced light emission of semiconductor surfaces, but also opens up a new avenue for engineering the plasmon-mediated interfacial charge transfer in molecular and semiconducting materials.
关键词： TiO2,scanning tunneling microscopy,light emission,plasmon
更新于2025-09-23 15:22:29
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A Review on Optical Imaging of DNA Nanostructures and Dynamic Processes
摘要： This article reviews recent advances in optical imaging methods for characterizing self-assembled DNA nanosystems, with particular emphasis on super-resolved fluorescence microscopy. Several advanced strategies are developed to obtain accurate and detailed images of intricate DNA nanogeometries and to perform precise tracking of molecular motions in dynamic processes. We present state-of-the-art instruments and imaging strategies including localization microscopy and spectral imaging. We discuss how they are used in biological studies and biomedical applications, and also provide current challenges and future outlook. Overall, this review serves as a practical guide in optical microscopy for the field of DNA nanotechnology.
关键词： super-resolution microscopy,fluorescence microscopy,optical imaging,DNA nanostructures,DNA nanotechnology
更新于2025-09-23 15:21:21
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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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Template-driven dense packing of pentagonal molecules in monolayer films
摘要： The integration of molecules with irregular shape into a long-range, dense and periodic lattice represents a unique challenge for the fabrication of engineered molecular scale architectures. The tiling of pentagonal molecules on a 2D plane can be used as a proof-of-principle investigation to overcome this problem since basic geometry dictates that a two-dimensional (2D) surface cannot be filled with a periodic arrangement of pentagons, a fundamental limitation that suggests that pentagonal molecules may not be suitable as building blocks for dense films. However, here we show that the 2D covalent organic framework (COF) known as COF-1 can direct the growth of pentagonal guest molecules as dense crystalline films at the solution/solid interface. We find that the pentagonal molecule corannulene adsorbs at two different sites on the COF-1 lattice, and that multiple molecules can adsorb into well-defined clusters patterned by the COF. Two types of these dense periodic packing motifs lead to a five-fold symmetry reduction compatible with translational symmetry, one of which gives an unprecedented high molecular density of 2.12 molecules/nm2.
关键词： host-guest system,fivefold symmetry,scanning probe microscopy,pentagonal molecules
更新于2025-09-23 15:21:21
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Sb <sub/>2</sub> Te <sub/>3</sub> growth study reveals: Formation of Nanoscale Charge Carrier Domains Is an Intrinsic Feature Relevant for Electronic Applications
摘要： Sb2Te3 exhibits a plethora of fundamentally relevant electronic phenomena enabling electronic phase change memory cells, thermoelectric devices and three-dimensional topological insulator structures. Thus, the controlled growth of nanostructures and thin films with well-defined electronic properties is of uttermost importance. Previously, our group observed symmetric infrared domains in hexagonal Sb2Te3 nanoplatelets from a solvothermal chemical synthesis. The relative optical contrast observed was indirectly linked to the formation of regions with different defect densities (charge carrier concentrations). This raises two major questions, which we answer in this study: Is the domain formation restricted to the specific platelet growth process? No! Do the infrared spectra of both domains really follow a ‘Drude-like’ free charge carrier response? Yes! By controlling the initial water concentration, we promote the growth of the nanoplatelets in c-direction and tune the morphology from platelet-like to octahedra-like. Although the growth mode changes from spiral growth to layer-by-layer, similar infrared domains are identified using scattering-type scanning near-field optical microscopy (s-SNOM). Furthermore, we also reproduced the formation of symmetric infrared domains in thin, high quality crystalline films grown using molecular beam epitaxy (MBE). Normalized infrared near-field spectra of smaller Sb2Te3 nanoparticles reveal a relative shift of the plasma frequency in both domains. These findings demonstrate that the formation of domains with different charge carrier properties is an intrinsic material property of Sb2Te3 and might strongly influence all of its electronic applications.
关键词： infrared near-field microscopy,Antimony telluride,domain formation,van der Waals materials,transition metal dichalcogenides,epitaxial growth
更新于2025-09-23 15:21:21
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Ecofriendly synthesis of monodispersed silver nanoparticles using Andean Morti?o berry as reductant and its photocatalytic activity
摘要： Morti?o (Vaccinium floribundum Kunth) berry is an endemic fruit from the Andes region and rich in vitamins, polyphenolic and anthocyanin compounds. The present report describes the Morti?o berry extract mediated biosynthesis of silver nanoparticles and their photocatalytic evaluations. The conditions for the synthesis of silver nanoparticles were optimised by adjusting amount of berry extract, pH, and time. Biosynthesis of silver nanoparticles was primarily identified by the appearance of yellow colour and confirmed by measurements of UV-visible spectroscopy. Particle size distribution, morphology and crystalline nature of silver nanoparticles were characterised by transmission electron microscopy, dynamic light scattering, and X-ray diffraction techniques. All characterisation technique reveals that the generated silver nanoparticles were stable, non-aggregated, monodispersed, spherical shape with an average size of 20.5 ± 1.5 nm and face centred cubic in nature. In order to evaluate photocatalytic activity, degradation of methylene blue dye by silver nanoparticles under sunlight was used as model system. It showed photocatalytic activity against methylene blue dye (5 mg/L, k= 0.00707788 min-1), efficiently. This ecofriendly approach highlighted the importance of Morti?o berry in green nanotechnology and generates a new scope of other Andean fruits in engineering applications.
关键词： Photocatalysis,Ecofriendly,Phytochemicals,Morti?o berry,Transmission Electron Microscopy,Silver nanoparticles
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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Light-microscopy methods in C. elegans research
摘要： Ever since Caenorhabditis elegans was introduced as a model system it has been tightly linked to microscopy, which has led to significant advances in understanding biology over the last decades. Developing new technologies therefore is an essential part in the endeavor to gain further mechanistic insights into developmental biology. This review will discuss state-of-the-art developments in quantitative light microscopy in the context of C. elegans research as well as the impact these technologies have on the field. We will highlight future developments that currently promise to revolutionize biological research by combining sequencing-based single-cell technologies with high-resolution quantitative imaging.
关键词： quantitative imaging,light microscopy,developmental biology,single-cell technologies,C. elegans
更新于2025-09-23 15:21:21