Supersaturation Ostwald ripening

The growth of the nanoparticles could have occurred either by the growth of CdSe on the seeds (growth from supersaturated solution) or by the process of Ostwald ripening whereby larger seed grow at the expense of the smaller ones. 

The dispersion of the precipitate changes with the degree of supersaturation and its evolution during precipitation. Low supersaturation leads to poorly dispersed solids. Highly dispersed solids are thermodynamically unstable and tend to lose dispersion (Ostwald ripening). This takes place during the process of precipitation itself. If the effect is desired, a special maturation (or ageing) step is carried out at the end of the precipitation. 

In our discussions of crystal growth theory and kinetics, we have assumed that the crystal growth rate is not a function of crystal size. While a good first assumption, this is not always true. As we saw in our discussion of Ostwald ripening, there is a difference in solubility between very small particles and larger particles. This differential solubility will result in a difference in supersaturation as a function of particle size. The smaller particles will be at a lower supersatura-... 

S. A. Kukushkin and A, V, Osipov. Crystallization of binary melts and decay of supersaturated solid solutions at the ostwald ripening stage under non-isothermal conditions. J. Phys. 

The phenomenon of ripening in crystallization, frequently denoted as Ostwald ripening, occurs in suspensions of very small crystals. Although the system may remain supersaturated (or supercooled), those with size smaller than the critical one, will dissolve and those with size larger than r will grow further. In time, the crystal size distribution will change, and the average crystal size will increase. 

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