Abstract
Gibbs classical nucleation theory predicts that a supersaturated solution will have transient nuclei that flitter in and out of existence. Only when one of these nuclei becomes larger than a critical size, will the solution crystalize. Recently, nonclassical nucleation theories have invoked the presence of prenuclei possibly associated with a liquid-liquid phase separation. However, there are few experimental observations of such prenuclei. Here, we use ultrafast optical Kerr-effect spectroscopy to measure the temperature-dependent low-frequency (sub-gigahertz to terahertz) anisotropic Raman spectra of supersaturated aqueous sodium thiosulfate solutions. Clear evidence of clusters is obtained in the spectra. However, on the basis of the inferred stability of these clusters, it appears that they frustrate rather than promote the formation of crystals. This would explain the surprising stability of supersaturated sodium thiosulfate and similar solutions.
Highlights
The nucleation of crystals from solutions is critically important in biomineralization, industrial production of pharmaceutical drugs, nanoparticles, and dyes, as well as protein crystallography.[1,2] Gibbs classical nucleation theory describes this process in terms of a process in which single molecules attach or detach from a growing nucleus.[3]
The basis of classical nucleation theory has been called into question by a number of studies that showed the presence of thermodynamically stable prenucleation clusters.[4,5]
These prenucleation clusters might well be related to a hidden liquid−liquid phase separation critical point that leads to metastable dense liquid as a precursor to crystallization[7−11] and that could even be controlled using external forces.[12]
Summary
The nucleation of crystals from solutions is critically important in biomineralization, industrial production of pharmaceutical drugs, nanoparticles, and dyes, as well as protein crystallography.[1,2] Gibbs classical nucleation theory describes this process in terms of a process in which single molecules attach or detach from a growing nucleus.[3]. Nucleation might be driven by (oriented) attachments between subcritical clusters that already exhibit a degree of crystallinity.[13]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
