On the Ostwald ripening of crystalline and amorphous nanoparticles

Ostwald ripening of crystalline and amorphous nanoparticle dispersions of a model organic compound are compared. While amorphous nanoparticles show a rapid ripening on the timescale of minutes, the crystalline nanoparticles do not ripen within the timescale of weeks. A metastable zone for crystal growth, presumably involving a free energy barrier, is identified, and we propose that this explains the absence of Ostwald ripening in the nanocrystal dispersion. As Ostwald ripening is a process typically occurring near equilibrium, even a small barrier may prevent ripening.