Dr Sean Collins

Profile

I joined the University of Leeds in December 2019 as a University Academic Fellow associated with the Bragg Centre for Materials Research. I work jointly across the School of Chemical and Process Engineering and the School Chemistry.

I completed my undergraduate degrees at the University of Michigan, Ann Arbor in the USA, pursuing degrees in chemistry and piano performance in parallel in the Department of Chemistry and the School of Music. I then moved to the UK for my PhD at the University of Cambridge in the Department of Materials Science and Metallurgy. During my PhD, I developed two-dimensional (imaging) and three-dimensional (tomographic) approaches for the study of light-matter interactions with gold and silver nanoparticles, known as surface plasmons. Prior to moving to the University of Leeds, I held the Henslow Research Fellowship at Girton College, Cambridge, carrying out research at the University of Cambridge into advanced electron beam techniques for physico-chemical insights into heterogeneous catalysis and metal-organic framework glasses and composites.

I am committed to making research and teaching environments more inclusive, to working on improving representation and visibility of underrepresented and excluded groups, and to working to remove structural inequalities. I have particular experience working within LGBT+ organisations.

Research interests

Two- and three-dimensional chemical imaging at the nanoscale using electron microscopy.

Defects and interfaces in molecular materials

Materials used in products from pharmaceuticals to light emitting diodes (LEDs) are built from molecular crystals or crystalline phases that contain molecules or molecular ions as a subunit (in the case of hybrid and metal-organic solids). In these materials, the performance is strongly affected by the atomic structure as well as the electronic structure (molecular orbitals, bands) at locations in the material where the periodicity of the crystal changes. These locations are most often at interfaces and grain boundaries or at defects in the crystal structure. My research uses probes that are well-matched to the length scale of these key features. By using electron beams, which can be focused to <1 Å, measurements of the atomic structure are possible through direct imaging of the crystal as well as through using diffraction techniques. These electron beams also record electronic structure information in the form of spectroscopy. My reseach focuses on achieving spectroscopic measurements at UV, visible, and infrared energies to examine electronic excitations through to bond vibrations in tandem with atomic structure analysis. This research uncovers the crucial origins of limitations in performance and functional properties, information that will inform improvements in next-generation designs for advanced materials technologies.

Transport mechanisms at the nanoscale in microporous materials

I am interested in using direct nanoscale observation to understand the movement of gases and liquids through microporous materials (pore sizes < 2nm). Microporous materials include zeolites, metal-organic frameworks, and covalent organic frameworks (among others) and form the basis of many separations, membrane, catalysis, and gas storage technologies already in use in industry in several cases. Unravelling the three-dimensional paths available to molecules or ions in a microporous material requires development of imaging modalities for structure and composition across the the micron, nanometre, and atomic length scales. Microporous materials are conventionally considered challenging for characterization at the highest spatial resolution due to their fragility under electron beam irradiation. My research leverages advances in detectors and data processing approaches to minimise electron beam induced damage while observing signatures of coordination environment and bonding at the nanoscale and atomic resolution structural information. Together, these tools are used to map the network of paths in microporous solids and to trace chemical changes over the course of materials processing.

Advanced tomography

I am involved with several interdisciplinary collaborations developing core capabilities in eletron tomography. This research area serves to bridge the underpinning mathematics through to applications in ‘hard’ materials and biological systems. I use compressed sensing techniques, machine learning and artificial intelligence (AI) approaches, and correlative microscopies with the aim of improved quantification in three-dimensional imaging or lowering the quantity of input data required so as to reduce the dose, damage, or experiment time (depending on the objectives for a particular system).

Qualifications

• PhD (Materials Science)
• B. S. Chemistry
• B. Music (Piano performance)

Professional memberships

• Member of the Electron Microscopy and Analysis Group, Institute of Physics
• Member of the Microanalysis Society

Current postgraduate researchers

• Jess Snelson
• Callum Brennan