Przybylski, Michael

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Growth of organic crystals via attachment and transformation of nanoscopic precursors

2017-06-21, Jiang, Yuan, Kellermeier, Matthias, Gebauer, Denis, Lu, Zihao, Rosenberg, Rose, Moise, Adrian, Przybylski, Michael, Cölfen, Helmut

A key requirement for the understanding of crystal growth is to detect how new layers form and grow at the nanoscale. Multistage crystallization pathways involving liquid-like, amorphous or metastable crystalline precursors have been predicted by theoretical work and have been observed experimentally. Nevertheless, there is no clear evidence that any of these precursors can also be relevant for the growth of crystals of organic compounds. Herein, we present a new growth mode for crystals of DL-glutamic acid monohydrate that proceeds through the attachment of preformed nanoscopic species from solution, their subsequent decrease in height at the surface and final transformation into crystalline 2D nuclei that eventually build new molecular layers by further monomer incorporation. This alternative mechanism provides a direct proof for the existence of multistage pathways in the crystallization of molecular compounds and the relevance of precursor units larger than the monomeric constituents in the actual stage of growth.

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Amino acids form prenucleation clusters : ESI-MS as a fast detection method in comparison to analytical ultracentrifugation

2012, Kellermeier, Matthias, Rosenberg, Rose, Moise, Adrian, Anders, Ulrike, Przybylski, Michael, Cölfen, Helmut

Electrospray ionisation mass spectrometry (ESI-MS) is a fast method which is able to provide molecular mass information with high precision. In this contribution, we show that prenucleation clusters—species recently found to play a pivotal role in crystallisation processes—are detected in addition to monomers by analytical ultracentrifugation (AUC) for the whole range of DL-amino acids, while higher oligomers are simultaneously observed in ESI-MS spectra. This suggests ESI-MS is a fast method to identify systems, which form prenucleation clusters. The occurrence of these clusters as relevant precursors in non-classical nucleation scenarios thus appears to be a more common phenomenon than so far assumed.