A New Correlative Approach for Structure Determination & Imaging of Molecular Materials

Electron microscopy (EM) is now an indispensable tool for nanoscale imaging and analysis, enabling many important discoveries across the engineering, physical and life sciences. It is widely accepted that the level of structural, chemical and dynamic information currently accessible by EM is limited by material stability under the electron beam and/or the temporal resolution of the data capture system, rather than by microscope resolution. Recently developed fast-pixelated electron cameras (EC) have created a new paradigm for the investigation of challenging molecular and e-beam sensitive materials that are generally incompatible with conventional EM environments (vacuum, ionising radiation etc.). Their stabilisation and effective analysis necessitate combinations of low-dose, high-sensitivity and ultra-fast data acquisition approaches, often combined with cryogenic stabilisation. Here, we seek to install a complementary pair of high-performance & direct-detection electron cameras (HP-EC & DD-EC) on two transmission electron microscopes (TEM: Jeol 2100Plus and 2100F), housed in the interdisciplinary Nanoscale & Microscale Research Centre (nmRC), with associated high-tilt, cryo-transfer TEM holder (HT-CTH) and scanning TEM (STEM) diffraction system control, to create a new research capability in the UK for correlated morphological & molecular dynamic investigations.

Low-dose and/or cryogenically stabilised imaging will be used for the rapid acquisition of tilt-series for the tomographic reconstruction of materials, with greatly improved information content, for investigations of hydrogels to cell/scaffold interactions. Ultra-fast, dynamic imaging will be used to observe chemical reactions in real-time, towards the development of catalysts & energy materials. This EC capability will provide also for microcrystal electron diffraction (microED) for structure determination of sub-micron sized supramolecular crystals, for energy efficient separation reactions & drug-delivery strategies; whilst removing the requirement to grow large molecular crystals to facilitate structure determination. Correlated in operando approaches will be used to investigate functionalised framework materials, with unprecedented spatial & temporal resolution, targeting gas storage and separation reactions, cell / hydrogel interactions, and next generation electronics. This equipment will also underscore recent advances in correlative, cryogenic imaging across the length scales (CLSM to FIBSEM, to OrbiSIMS & TEM), using protocols pioneered at UoN (EP/S021434/1).

In recent years, development of ultra-fast / sensitive CMOS chips has revolutionised EM, where rapid acquisition of images from beam-sensitive samples under low fluence conditions is required. Indeed, cryo-EM (2017 Nobel Prize for Chemistry) is underpinned by such ECs, enabling rapid acquisition & summation of large, low-contrast image datasets. In simple terms, a state-of-the-art HP-EC will provide for an x16 improvement in field of view (with same level of resolution), combined with x10 increase in data acquisition rate, compared to our existing detector capability (2100Plus), ideal for cryogenic, low-dose, tomographic investigations; with acquisition of data-sets for reconstruction becoming facile (a minute rather than an hour), improving productivity. The DD-EC will provide for an x4 improvement in field of view combined with x100 increase in data acquisition rate, compared to our existing detector capability (2100F), appropriate for following chemical reactions in real-time (1500 fps). When combined with automatic alignment and real-time drift-correction, this capability will accelerate the development of functionalised framework materials, characterised using microED. Accordingly, we seek to sustain and elevate a broad range of interdisciplinary materials science research programmes, benefiting EPS research communities at the UoN, the wider East Midlands and across the UK.