Abstract
There is mounting evidence that crystal nucleation from supersaturated solution involves the formation and reor-ganisation of pre-nucleation clusters contradicting classical nucleation theory. Here, a wide range of amino acids and peptides is investigated using light scattering, mass spectrometry, and in-situ terahertz Raman spectroscopy to demonstrate that the presence of amorphous aggregates with a wide range of sizes is a general phenomenon in supersaturated solutions. Additionally, these amorphous aggregates act as intermediates for laser-induced crystal nucleation. These observations are inconsistent not only with classical nucleation theory, but also non-classical theories involving liquid-liquid phase separation, requiring a new approach.
Supplementary materials
Title
aggregate-assisted laser-induced nucleation of alanine
Description
laser-induced nucleation of alanine from supersaturated aqueous solution that has been aged for 2 days. Once laser-induced nucleation takes place (t = 4 s), a burst of emission is observed. This effect is likely due to crystalloluminescence in which dopant metal cations trapped in the growing crystal lattice relax through light emission.
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Title
aggregate-assisted laser-induced nucleation of Gly-Gly
Description
Another example of laser-induced nucleation of a supersaturated Gly-Gly solution. When brought into the laser focus, nucleation from the aggregate starts almost immediately with a sizable crystal forming within seconds. Similar to the case of alanine, blocking the laser would cause the formed crystal to dissolve again.
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Title
aggregate-assisted laser-induced nucleation of Gly-Gly-Gly
Description
laser-induced nucleation in a supersaturated solution of Gly-Gly-Gly, where again crystalloluminescence is observed.
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