Assessing the accuracy of soot nanoparticle morphology measurements using three-dimensional electron tomography 2019-01-1188
Morphology plays an important role in determining behaviour and impact of soot nanoparticles, including effect on human health, atmospheric optical properties, contribution to engine wear, and role in marine ecology. However, its nanoscopic size has limited the ability to directly measure useful morphological parameters such as surface area and effective volume. Recently, 3D morphology characterisation of soot nanoparticles via electron tomography has been the subject of several introductory studies. So-called ‘3D-TEM’ has been posited as an improvement over traditional 2D-TEM characterisation due to the elimination of the error-inducing information gap that exists between 3-dimensional soot structures and 2-dimensional TEM projections. Little follow-up work has been performed due to difficulties with developing methodologies into robust high-throughput techniques. Recent work by the authors has exhibited significant improvements in efficiency, though as yet due consideration has not been given to assessing fidelity of the technique. This is vital to confirm significant and tangible improvements in soot-characterisation accuracy that will establish 3D-TEM as a legitimate tool. Synthetic ground-truth data was developed to closely mimic real soot structures and the 3D-TEM volume-reconstruction process. A variety of procedures were tested to assess the magnitude and nuances of deviations from ground-truth values. Results showed average Z-elongation due to the ‘missing-wedge’ at 3.4% for the previously developed optimised procedure. Mean deviations from ground-truth in volume and surface area were 4.4% and 1.7% respectively. Results indicate highly accurate 3D-reconstruction can be achieved with an optimised procedure that can bridge the gap to permit high-throughput 3D morphology characterisation of soot.
Ephraim Haffner-Staton, Antonino La Rocca, Alasdair Cairns, Michael McGhee, Mike Fay