Polymorphism control of nanosized glycine crystals on engineered surfaces

Abstract

Crystallization in a constrained environment was used to prepare organic molecular nanocrystals of glycine. Bifunctional patterned surfaces, with hydrophilic islands as small as 1 µm surrounded by hydrophobic regions, were prepared by photolithography. Individual nanosized glycine crystals were formed from the confined solution droplets on each hydrophilic island. Supersaturation was controlled by slow cooling or by slow evaporation. Individual crystals were characterized with AFM and Raman spectroscopy. Slow cooling produced the least stable β-form except for the slowest cooling rate (0.001 °C min−1) which produced both α- and β-form. Slow evaporation (100 hours) resulted in the concomitant nucleation of all three glycine forms.