Special CPM Seminar

Resolving Nanoscale heterogeneity with single Particle Imaging

Duane Loh

Department of Physics & Department of Biological Sciences
National University of Singapore

The nanoscale world is violent and disordered. To make sense of this world we have to selectively remove, “freeze out, and restrain their components just to resolve their confusing and transient heterogeneities. Otherwise, such details will just appear blurred.

Over the past decade, significant leaps in high-resolution imaging have allowed us a better view of such in-situ heterogeneity using a class of techniques known as single-particle imaging. Here, instead of averaging over a quasi-homogenous ensemble of objects (or particles), we measure a very large dataset comprising noisy and incomplete views of individual objects. Using statistical methods, one can then robustly tease out the nature and degree of heterogeneity hidden within the ensemble.

In this talk, I will discuss popular single particle imaging techniques with x-ray free-electron lasers [1,2], and liquid-cell electron microscopy [3], and how they can help us resolve transient structural states in non-equilibrium processes such as aggregation, nucleation and polymerization.

References:
[1] Loh, N. D. et al. Fractal morphology, imaging and mass spectrometry of single aerosol particles in flight. Nature 486, 513-517 (2012).
[2] Sellberg, J. A. et al. Ultrafast X-ray probing of water structure below the homogeneous ice nucleation temperature. Nature 510, 381-384 (2014).
[3] Loh, N.D. et al. Multistep nucleation of nanocrystals in aqueous solution. Nature Chemistry advance online publication (2016).