22 research outputs found
Cryogenic electron ptychographic single particle analysis with wide bandwidth information transfer
Advances in cryogenic transmission electron microscopy have revolutionised the determination of many macromolecular structures at atomic or near-atomic resolution. This method is based on conventional defocused phase contrast imaging. However, it has limitations of weaker contrast for small biological molecules embedded in vitreous ice, in comparison with cryo-ptychography, which shows increased contrast. Here we report a single-particle analysis based on the use of ptychographic reconstruction data, demonstrating that three dimensional reconstructions with a wide information transfer bandwidth can be recovered by Fourier domain synthesis. Our work suggests future applications in otherwise challenging single particle analyses, including small macromolecules and heterogeneous or flexible particles. In addition structure determination in situ within cells without the requirement for protein purification and expression may be possible
2020 roadmap on solid-state batteries
Li-ion batteries have revolutionized the portable electronics industry and empowered the electric vehicle (EV) revolution. Unfortunately, traditional Li-ion chemistry is approaching its physicochemical limit. The demand for higher density (longer range), high power (fast charging), and safer EVs has recently created a resurgence of interest in solid state batteries (SSB). Historically, research has focused on improving the ionic conductivity of solid electrolytes, yet ceramic solids now deliver sufficient ionic conductivity. The barriers lie within the interfaces between the electrolyte and the two electrodes, in the mechanical properties throughout the device, and in processing scalability. In 2017 the Faraday Institution, the UK's independent institute for electrochemical energy storage research, launched the SOLBAT (solid-state lithium metal anode battery) project, aimed at understanding the fundamental science underpinning the problems of SSBs, and recognising that the paucity of such understanding is the major barrier to progress. The purpose of this Roadmap is to present an overview of the fundamental challenges impeding the development of SSBs, the advances in science and technology necessary to understand the underlying science, and the multidisciplinary approach being taken by SOLBAT researchers in facing these challenges. It is our hope that this Roadmap will guide academia, industry, and funding agencies towards the further development of these batteries in the future
Transmission electron microscopy of titanium dioxide nanoplatelets and nanorods
As the size of the bulk crystal reduces to the nanometre scale, anatase titania
exhibits enhanced photocatalytic properties. Nanostructuring of TiO2
involves engineering the crystal facets in a way that speci c types of surfaces
dominate the 3D shape. The atomic structure of the surfaces and 3D morphology
of the crystal determine the electronic properties of the material, and
should be characterized with atomic precision. Due to its high spatial resolution
(0.1 nm), aberration-corrected transmission electron microscopy was
used to obtain morphological and structural information on anatase nanoplatelets
and nanorods. TEM morphological analysis showed that the main
3D shape of the platelets is that of a truncated tetragonal bipyramid, where
f001g facets dominate. This 3D shape is accessible via 2D projections of the
crystal structure. In the nanorod specimens, the types of edge morphology
found link to intermediate or nal stages of growth, occurred via oriented
attachment of primary nanocrystals and classical monomer addition. The
structural characterization of the nanocrystals was carried out by examining
the exit plane wave of the specimen, which was reconstructed from a
serial acquisition of aberration-corrected TEM images of di erent defocus.
The phase of the reconstructed wave reproduces the atomic potential of the
specimen, and provides information with the maximum resolution of the microscope.
The optical properties of the platelets and rods were also analysed
using a combination of STEM imaging and EELS. Due to the high surface
to volume ratio of the platelets, the EELS spectrum is dominated by strong
surface features that arise from the polarization of the surface electrons induced
by the electron beam. The in
uence of the surface excitations on the
EELS spectrum is strongly determined by the thickness of the platelets: by
modifying the crystal thickness below 20 nm, the frequency of the surface
excitations changes, enabling the optical properties of titania to be tuned in
the visible and UV range. Finally, preliminary EELS investigations on the
nanorods suggest that, unlike metallic nanoparticles, the surface excitations
are not in
uenced by the morphology of the crystal, but strongly depend on
its thickness.Open Acces
Phase Retrieval Quantitative Comparison Between Tilt-series Imaging in TEM and Position-resolved Coherent Diffractive Imaging in STEM
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Role of the Deep Eutectic Solvent Reline in the Synthesis of Gold Nanoparticles.
This work presents a mechanistic understanding of the synthesis of small (<3 nm) gold nanoparticles in a nontoxic, eco-friendly, and biodegradable eutectic mixture of choline chloride and urea (reline) without the addition of external reducing or stabilization agents. Reline acts as a reducing agent by releasing ammonia (via urea hydrolysis), forming gold nanoparticles even at trace ammonia concentration levels. Reline also affects the speciation of the gold precursor forming gold chloro-complexes, stabilizing Au+ species, leading to an easier reduction and avoiding the otherwise fast disproportionation reaction. Such a capability is however lost in the presence of large amounts of water, where water replaces the chloride ligands in the precursor speciation. In addition, reline acts as a weak stabilizing agent, leading to small particles (<3 nm) and narrow distributions although agglomerates quickly form. Such properties are maintained in the presence of water, indicating that it is linked to the urea stabilization rather than the hydrogen-bonding network. This work has important implications in the field of green synthesis of nanoparticles with small sizes, especially for biomedical and health care applications, due to the nontoxic nature of the components of deep eutectic solvents in contrast to the conventional routes
Three-dimensional Electron Ptychography of Catalyst Nanoparticles using Combined HAADF STEM and Atom Counting
Characterization of grain boundary disconnections in SrTiO3 Part II: the influence of superimposed disconnections on image analysis
Disconnections were recently shown to play a role in the mechanism of grain boundary motion in general grain boundaries in SrTiO3. In this work, we demonstrate the existence of disconnections in the viewing direction along the projected thickness of transmission electron microscopy samples and characterize possible aspects of the structure of these disconnections. We show that the presence of steps along the viewing direction may result in the appearance of a disordered region at the boundary, while it is actually composed of ordered crystalline material. We discuss the subsequent complications in analysis of transmission electron microscopy data and strict meaning of the term “edge-on” for grain boundaries