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EDX spectra for a bead underneath the membrane (blue line) and at a control location away form the membrane and on top of the nitride film (red line). Both spectra were integrated over 30 s and the bead-in-liquid spectrum is offset by 300 counts for ease of comparison. Inset (a) secondary electron image of location of bead-in-liquid. Inset (b) secondary electron image of control bead. Both scale bars indicate 500 nm.
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High resolution nanoscale imaging in liquid environments is crucial for
studying molecular interactions in biological and chemical systems. In
particular, electron microscopy is the gold-standard tool for nanoscale
imaging, but its high-vacuum requirements make application to in-liquid samples
extremely challenging. Here we present a new graphene b...
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Citations
... Beam damage is less significant at the liquid surface due to liquid diffusion during the in situ liquid imaging (Yang et al., 2011;Yu et al., 2019). Continuous scanning of a region by the SEM beam will draw particles to that region (Yang et al., 2015). The liquid cells used for this research mitigate these effects by using a large sample channel that allows particles to diffuse in and out of the bulk liquid. ...
A quantitative description on dispersity of boehmite (γ-AlOOH) particles, a key component for waste slurry at Hanford sites, can provide useful knowledge for understanding various physicochemical nature of the waste. In situ liquid scanning electron microscopy (SEM) was used to evaluate the dispersity of particles in aqueous conditions using a microfluidic sample holder, System for Analysis at Liquid Vacuum Interface (SALVI). Secondary electron (SE) images and image analyses were performed to determine particle centroid locations and the distance to the nearest neighbour particle centroid, providing reliable rescaled interparticle distances as a function of ionic strength in acidic and basic conditions. Our finding of the particle dispersity is consistent with physical insights from corresponding particle interactions under physicochem-ical conditions, demonstrating delicate changes in dispersity of boehmite particles based on novel in situ liquid SEM imaging and analysis.
... [172,174,198] Graphene is in principle superior to SiN as a window material in terms of minimum thickness and stability and used for innovative cell designs [199,200] but graphene-based cells are also more challenging to handle. [172,177] Liquid-phase SEM (LP-SEM) approaches [201] as well as spectroscopy modes [202] are also possible and similar considerations hold true as for ex situ EM, namely, that the resolution of LP-SEM (4-10 nm) is lower than that of LP-TEM but larger structures can be measured. A detailed discussion of the different technical approaches and their specific advantages can be found in a recent progress report. ...
Self‐assembly of nanoparticles (NPs) has evolved into a powerful tool for the synthesis of superstructures with tailored properties. The quality, diversity, and complexity of synthesized structures are continuously improving and fascinating new collective properties are demonstrated. At the same time, the rapid development of electron microscopy and synchrotron sources for X‐rays has enabled new exciting experimental approaches to study structure and structure formation in the context of NP self‐assembly. In this review, some recent studies and what can be learned from them are highlighted and discussed. It is started with a general introduction covering important concepts, experimental approaches, commonly obtained structures, the ideas of artificial atoms, and emerging properties are discussed. Recent experimental in situ and ex situ approaches with state‐of‐the‐art electron microscopy and X‐ray diffraction and scattering that helped to obtain a detailed picture of NP self‐assembly processes and resulting structures are then presented.
... The analysis volume in SEM is much higher, and the aperture is not critical as illustrated in our recent 27 and many others' works. 28,29 The dimension of the microchannel is flexible, ranging from 100 to 500 μm wide depending on the instrument and the spot size of the probe beam. 30 The depth of the channel ranges from 50 to 300 μm. ...
... The most significant recent example is the usage of graphene as another promising window material to surpass issues in liquid imaging in vacuum. 28,29 Recently, graphene was also illustrated to provide improved ion imaging of slowly dried neurons and skin cells using ToF-SIMS. 41 Unlike other commercial or research grade liquid cells, our SALVI cell is the only one that can be used with and without a micrometer-sized aperture on the detection window, namely, the SiN membrane [see Figs. ...
This review offers a succinct overview of the development of a vacuum-compatible microfluidic reactor system for analysis at the liquid vacuum interface (SALVI), and its diverse applications in in situ, in vivo, and in operando imaging of liquid surfaces as well as the air-liquid (a-l), liquid-liquid (l-l), and solid-liquid (s-l) interfaces in the past decade. SALVI is one of the first microfluidics-based reactors that has enabled direct analysis of volatile liquids in vacuum surface tools such as scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Its integration into ambient and vacuum spectroscopy and microscopy is illustrated. Several applications are highlighted including (1) imaging nanoparticles in liquid using in situ SEM; (2) mapping the evolving l-l interface using in situ x-ray absorption spectroscopy and ToF-SIMS; (3) following complex a-l interfacial oxidation reaction products using in situ ToF-SIMS; (4) capturing biological interfaces of cells and microbes via in vivo multimodal and correlative imaging; and (5) monitoring the dynamic solid electrode and liquid electrolyte interface using in operando molecular imaging. Finally, outlook and recommendations are presented. Besides showing the holistic information volume obtained by real-time multiplexed imaging, this review intends to convey the importance of tool development in revolutionizing surface and interface analysis using vacuum platforms previously limited to solid surfaces. Microfluidics is manifested to be not limited to ambient conditions in many examples in this review. Moreover, fundamental interfacial phenomena underpinning mass and charge transfer can now be pursued in real time via innovated chemical imaging and spectroscopy.
... The analysis volume in SEM is much higher, and the aperture is not critical as illustrated in our recent 27 and many others' works. 28,29 The dimension of the microchannel is flexible, ranging from 100 to 500 μm wide depending on the instrument and the spot size of the probe beam. 30 The depth of the channel ranges from 50 to 300 μm. ...
... The most significant recent example is the usage of graphene as another promising window material to surpass issues in liquid imaging in vacuum. 28,29 Recently, graphene was also illustrated to provide improved ion imaging of slowly dried neurons and skin cells using ToF-SIMS. 41 Unlike other commercial or research grade liquid cells, our SALVI cell is the only one that can be used with and without a micrometer-sized aperture on the detection window, namely, the SiN membrane [see Figs. ...
In situ, in vivo, and in operando imaging and spectroscopy of liquids using microfluidics in vacuum Cite as: J. Vac. Sci. Technol. A 38, 040804 (2020); https://doi. ABSTRACT This review offers a succinct overview of the development of a vacuum-compatible microfluidic reactor system for analysis at the liquid vacuum interface (SALVI), and its diverse applications in in situ, in vivo, and in operando imaging of liquid surfaces as well as the air-liquid (a-l), liquid-liquid (l-l), and solid-liquid (s-l) interfaces in the past decade. SALVI is one of the first microfluidics-based reactors that has enabled direct analysis of volatile liquids in vacuum surface tools such as scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Its integration into ambient and vacuum spectroscopy and microscopy is illustrated. Several applications are highlighted including (1) imaging nanoparticles in liquid using in situ SEM; (2) mapping the evolving l-l interface using in situ x-ray absorption spectroscopy and ToF-SIMS; (3) following complex a-l interfacial oxidation reaction products using in situ ToF-SIMS; (4) capturing biological interfaces of cells and microbes via in vivo multimodal and correlative imaging; and (5) monitoring the dynamic solid electrode and liquid electrolyte interface using in operando molecular imaging. Finally, outlook and recommendations are presented. Besides showing the holistic information volume obtained by real-time multiplexed imaging, this review intends to convey the importance of tool development in revolutionizing surface and interface analysis using vacuum platforms previously limited to solid surfaces. Microfluidics is manifested to be not limited to ambient conditions in many examples in this review. Moreover, fundamental interfacial phenomena underpinning mass and charge transfer can now be pursued in real time via innovated chemical imaging and spectroscopy.
... Beam damage is less significant at the liquid surface due to liquid diffusion during the in situ liquid imaging (Yang et al., 2011;Yu et al., 2019). Continuous scanning of a region by the SEM beam will draw particles to that region (Yang et al., 2015). The liquid cells used for this research mitigate these effects by using a large sample channel that allows particles to diffuse in and out of the bulk liquid. ...
en A quantitative description on dispersity of boehmite (γ‐AlOOH) particles, a key component for waste slurry at Hanford sites, can provide useful knowledge for understanding various physicochemical nature of the waste. In situ liquid scanning electron microscopy (SEM) was used to evaluate the dispersity of particles in aqueous conditions using a microfluidic sample holder, System for Analysis at Liquid Vacuum Interface (SALVI). Secondary electron (SE) images and image analyses were performed to determine particle centroid locations and the distance to the nearest neighbor particle centroid, providing reliable rescaled interparticle distances as a function of ionic strength in acidic and basic conditions. Our finding of the particle dispersity is consistent with physical insights from corresponding particle interactions under physicochemical conditions, demonstrating delicate changes in dispersity of boehmite particles based on novel in situ liquid SEM imaging and analysis.
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Lay description
fr In situ liquid scanning electron microscopy (SEM) was used to determine the interparticle distance of boehmite (γ‐AlOOH) particles, a key component for waste slurry at Hanford sites. This type of quantitative measurement is important to understand various physicochemical nature of the radiological waste containing boehmite. In situ liquid SEM was enabled by a unique vacuum compatible microfluidic cell, System for Analysis at Liquid Vacuum Interface (SALVI). We collected secondary electron (SE) images and performed image analyses to determine particle centroid locations and the distance to the nearest neighbor particle centroid to arrive at the interparticle distances in acidic and basic conditions. Our results show that delicate changes occur among boehmite particles under different pH conditions using novel in situ SEM imaging.
... Therefore, the measurement limitation is not the same as that of the dry sample, and the dynamic behavior may be one of the sources of image error. In theory, if the membrane thickness can be further reduced, it is possible to measure metal particles below 10 nm [21]. But how to maintain the membrane in a vacuum environment without cracking and having consistency is a difficult point. ...
This work presents in situ imaging of synthesized boehmite (γ‐AlOOH) particles ranging from 20 to 100 nm, suspended in liquid, in a vacuum compatible microfluidic sample holder using a scanning electron microscopy (SEM) under the high vacuum mode and highlights the advantage of in situ liquid imaging of colloids. Nanometer‐sized boehmite particles in high‐level radioactive wastes at the Hanford site are known to be difficult to dissolve and cause rheological problems for processing in the nuclear waste treatment plant. Therefore, it is important to characterize boehmite particles and understand how they form aggregates in the liquid state. Several technical advancements are made to optimize in situ liquid SEM chemical imaging resulting in the improved ability to obtain secondary electron (SE), backscattered electron (BSE) images, and energy dispersive X‐ray spectroscopy (EDX) spectra. Moreover, our results show mixed particles could be studied and identified based on the particle shape and elemental composition using in situ SEM imaging and EDX. Thus, we provide a new and improved approach to observe the evolution of particle dispersion and stability in liquid under conditions similar to those in the waste tank.
A graphene liquid cell for transmission electron microscopy (TEM) uses one or two graphene sheets to separate the liquid from the vacuum in the microscope. In principle, graphene is an excellent material for such an application because it allows the highest possible spatial resolution, provides a flexible covering foil, and effectively protects the liquid from evaporating. Examples in open literature have demonstrated atomic-resolution TEM using small liquid pockets and the coverage of whole biological cells with graphene sheets. A total of three different basic types of liquid cells are discerned: (i) one graphene sheet is used to cover a liquid sample supported by a thin membrane of another material (for example, silicon nitride, SiN), (ii) two graphene sheets pressed together leaving liquid pockets with graphene at both sides, and (iii) a spacer material with liquid pockets covered at both sides by graphene. A total of four different process flows are available for liquid cell assembly, but there is not yet a consensus on the best routes, and a number of variations exist. The key step is the transfer of graphene to a liquid sample, which is complicated by practical issues that arise from imperfections in the graphene sheets, such as cracks. This review provides an overview of these different approaches to assembling graphene liquid cells and discusses the main obstacles and ideas to overcome them with the prospect of developing the nanoscale technology needed for graphene liquid cells so that they become available on a routine basis for electron microscopy in liquid. It also provides guidance in selecting the appropriate type of graphene liquid cell and the best assembly method for a specific experiment.
