High resolution, cryogenic analytical and transfer scanning electron microscope (HR-CAT-SEM)

Lead Research Organisation: University of Nottingham
Department Name: Sch of Chemistry

Abstract

Natural and man-made molecular materials are at the heart of many modern day technologies, from energy conversion and storage devices, to propulsion systems to construction materials, whilst being also at the core of everyday life, from foodstuffs, healthcare products and cosmetics, to electronic devices and textiles. Thanks to recent advances in the analytical sciences, now we know what molecules are present within "molecular materials", however, due to the fact that most molecular materials (including living matter) exhibit highly complex, heterogeneous compositions, with a lack of long-range order, combined with highly dynamic/metastable properties, often we have only a vague idea where these molecules are located. Considering that all the important functional properties of materials, including electronic, photonic, magnetic, catalytic gas-sorption and transport, emerge at the nanoscale, and the biological function of living cells relies on the molecular machinery operating at the nanoscale, it is critically important to develop new methodologies capable of providing full structural information on any material of any complexity, from single molecule to nanoscale supramolecular assembly to 3D microscale architectures.

Currently, amongst the analytical techniques, electron microscopy (EM) is in a unique position to offer morphological information content, in 3D, across the pico-, nano- and micro-length scales. However, in the context of molecular materials, EM methodologies suffer from two significant drawbacks, related to the invasive nature of the electron beam that can rapidly damage delicate molecules within materials, whilst they are imaged. Also, EM operates in vacuum conditions, being incompatible with most hydrated materials, including biological samples, the native structures of which are simply lost when water is removed. The proposed new HR-CAT-SEM platform - comprising a uniquely configured High Resolution, Cryogenic Analytical and Transfer Scanning Electron Microscope, is designed to solve these challenges, through the use of low energy electron beams (down to 1keV), whilst delivering 1.6nm of spatial resolution necessary for effective nanoscale analyses (enabled by the use of a field emission gun (FEG), combined with modern high contrast, multi-mode detectors); and by stabilising the material, either thermally or through hydrated sample vitrification, and sectioning using a focused ion beam (FIB), all under cryogenic conditions, thereby enabling the investigation of previously intractable materials science problems, through 3D multiscale analysis.

Importantly, the cryo-FIB sectioning and cryo-transfer protocols developed at Nottingham, to be implemented within the HR-CAT-SEM, will allow a journey across the length scales; starting from the microscale, enabled by optical microscopy and scanning electron microscopy (SEM), to the nanoscale (FEG-SEM), and picoscale (transfer to high resolution transmission electron microscopy HR-TEM), delivering the most complete structural understanding of complex molecular materials to date. In addition, the unique cryo-transfer capability of the HR-CAT-SEM will open up new horizons in correlative analysis, where structural information obtained by EM methods will be complemented by secondary ion mass spectrometry (OrbiSIMS) and X-ray photoelectron spectroscopy (XPS), providing correlated information on chemical molecular composition and molecular bonding, from the same volume of material. A project of such scale and ambition is made possible due to the rich expertise in this area available at Nottingham, and the uniquely configured Nanoscale & Microscale Research Centre laboratories www.nottingham.ac.uk/nmrc, where the HR-CAT-SEM will be housed, that already hosts all the instruments necessary for correlative analysis (HRTEM, XPS, OrbiSIMS), under one roof, along with the necessary sample handling infrastructure, required for full, effective implementation of this project.

Planned Impact

By its very nature, HR-CAT-SEM will contribute to advancements across a broad spectrum of disciplines: Chemistry, Pharmacy, Materials Science, Food Science and Biology. In addition, this instrument will continue to facilitate on-going investigations across a wide range of more traditional inorganic materials science problems, at high spatial resolution, e.g. metal oxide nanocomposites for the aerospace industry (Engineering) and semiconductor device structures for the optoelectronics industry (Physics/E&EE); soft organic materials, biological cell interactions with porous scaffolds and orthopaedic implant materials (Engineering/Pharmacy); and nanostructured materials for hydrogen storage applications and nanocatalysis (Engineering/Chemistry); reaching the widest cross-section of the UK economy. Hence, HR-CAT-SEM will open up pathways to impact across a wide range of challenging material systems, of immediate importance to the Oil & Gas / Geochemical, Polymer, Food & Pharmaceutical industries. Each of the team of 14 investigators on this proposal have established active industrial collaborations with UK companies covering these sectors, which will ensure immediate impact of HR-CAT-SEM on the UK economy.

The Steering Group of the nmRC, consisting of representatives of all five Faculties of UoN, will work closely with UoN's Research and Innovation group (R&I) to manage collaborations with industrial partners, knowledge exchange, and the commercialisation of future research. A representative from R&I will sit on the nmRC Steering Group, to ensure that industrial collaborations are managed efficiently and that research outcomes are maximised. R&I have staff dedicated to the energy, aerospace and pharmaceutical sectors and both the management and users of the nmRC will work closely with these experts. For example, the development of innovative techniques in the cryogenic sectioning and transfer of materials across FIBSEM, TEM and SIMS platforms creates potential for future collaborations with companies in the Judges Group (11 scientific and engineering companies all based in the UK). Currently, the nmRC runs active partnerships with > 40 companies that require FIB, SEM and TEM analyses (methods at the core of HR-CAT-SEM), such that HR-CAT-SEM can be applied immediately to a range of industrial challenges, building on existing services-rendered work carried out at the nmRC for precision engineering, aerospace, energy, food science, and the medical and geological sectors, e.g. Rolls-Royce, EoN, Smith & Nephew and Juniper Pharmaceuticals, that require HR-CAT-SEM capabilities.

Publications

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