The Formation of Nano Sized Glycine Crystals on Engineered Surfaces

The direct formation of organic molecular crystals of below one micron is generally a difficult problem. Methods which employ high supersaturations often produce amorphous solids or oiling out. In addition, high supersaturations make polymorph control difficult often resulting in less stable solid forms. In this study, patterned gold islands of less than one micron are prepared using lithography. Self Assembled Monolayers (SAMs) are used to prepare bifunctional (hydrophilic and hydrophobic) surfaces upon which the droplets of solution are deposited. As shown previously in our work (Lee at al. 2005) the size of the island will influence the final crystal size obtained and the evaporation rate of solvent will determine the crystal form obtained. Supersaturation is controlled by slightly diffusing anti solvent into confined small solution droplets on bifunctional patterned SAMs. This method allows each island to be created single nano-sized crystals. Glycine crystals under 500nm have been made and characterized by Atomic Force Microscopy (AFM).