Distinguished Seminar Series: Professor Sarah Haigh скачать в хорошем качестве

Distinguished Seminar Series: Professor Sarah Haigh

Atomic Imaging in Liquid Environments using 2D material heterostructures Nanomaterials have driven huge scientific innovation in computing, communications, energy, transportation and healthcare. This rapid progress has only been possible due to innovative characterisation methods, which allow visualisation, control and optimisation of structure at the nanoscale. Transmission electron microscopy (TEM) is an essential characterisation technique enabling nanomaterials development, yet most TEM is performed with the sample exposed to high vacuum, an environment that is not compatible with most chemical reaction conditions, physical processes or biological structures. Commercial in-situ liquid cell TEM imaging holders often prevent atomic resolution imaging and chemical analysis. We have pioneered a new approach to in-situ imaging that does not compromise the TEM’s atomic resolution or analytical capabilities by using 2D materials to encapsulate the controlled reaction environment [1]. This approach builds on work in Manchester studying the flow of liquids and gases within confined nanochannels (Fig. 1b)[2], as well as our previous work studying chemical degradation of 2D materials with promising performance but which are sensitive to air and moisture (e.g. CrBr3, GaSe, black phosphorus) (Fig. 1c)[3]. The in-situ 2D heterostructure liquid cell approach we have developed makes it possible to study the earliest stage of chemical synthesis at the atomic scale; something that was not previously possible by any technique. Our experimental set-up contains two pockets of liquid separated by an atomically thin membrane and mixing is induced by nanofracture of the separation membrane with the electron beam (Fig. 1a). We exemplify this new experimental platform by studying time evolution of calcium carbonate synthesis, a process that is key for many marine organisms and in the construction industry, but where growth details remain the subject of intense debate. Our observations provide the first direct visual evidence for the recently developed liquid-liquid phase separation theory, essential knowledge to understand the synthesis behaviour and hence to optimise the materials produced [4]. Furthermore, our platform enables the first studies of adatom dynamics at solid liquid interfaces (Fig. 1aii)[5] and provides a route to understanding the enormous changes in atom/ion motion at interfaces where the 2D materials are twisted with respect to each other.[6] [1] Nanometer resolution elemental mapping in graphene-based TEM liquid cells, Kelly et al Nano Letters (2018) 18 (2), 1168-1174 (58 citations) [2] Capillary condensation under atomic-scale confinement, Q Yang et al, Nature 588 (7837), 250-253 (2020); Ballistic molecular transport through two-dimensional channels, A Keerthi et al, Nature 558 (7710), 420-424 (2018); Molecular transport through capillaries made with atomic-scale precision, B Radha et al, Nature, (2016) 538 (7624), 222-225 [3] Atomic Resolution Imaging of CrBr3 Using Adhesion-Enhanced Grids, Hamer et al Nano Letters (2021) (9), 6582-6589; Enhanced Superconductivity in Few-Layer TaS2 due to Healing by Oxygenation, Bekaert, et al, Nano Letters, (2020), 20 (5), 3808-3818; Formation and Healing of Defects in Atomically Thin GaSe and InSe, Hopkinson, et al. ACS Nano, (2019), 13, 5, 5112–5123; Scalable patterning of encapsulated black phosphorus, Clark et al, Nano Letters (2018) 18 (9), 5373-5381 [4] In situ TEM imaging of solution-phase chemical reactions using 2D-heterostructure mixing cells Kelly et al, Advanced Materials, (2021) [5] Tracking single atoms in a liquid environment Clark et al. https://arxiv.org/abs/2203.04906 [6] Ion exchange in atomically thin clays and micas. Zou et al, Nature Materials (2021), 20, (12) 1677–1682,; Atomic reconstruction in twisted bilayers of transition metal dichalcogenides, Weston et al, Nature Nanotechnology (2020), 15 (7), 592-597;