Particle Design of Organic Molecular Crystals on Nanoengineered Surfaces

摘要

Functionalized nanoengineered surfaces, specifically self-assembled monolayers (SAMs) of aromatic thiolates have been used as templates for the heterogeneous nucleation and growth of organic molecular crystals. These molecularly well-defined substrates are used as an interface on which they serve as nucleation promoters as the activation barrier for nucleation is lowered through a reduction in the surface excess energy via favorable interaction between the clusters of the crystallizing phase and the monolayer film. In three different amino acids, glycine, L-alanine and DL-valine, it is observed that surfactant monolayer acts as catalyst for nucleation and modifications in the surface chemistry of the thin film at the molecular level can lead to dramatic variation in the crystal orientation as well as the shape of the crystals. This is primarily due to changes in the interfacial interactions at the crystal surface-monolayer interface. The use of supramolecular templates with different motifs resulted in enhanced nucleation and controlled crystal growth, in turn, enabling one to engineer or design specific crystals.