Oriented crystallization of CuSO4·5H2O under a monolayer of a novel amphiphilic ligand, 8-hexadecyloxyquinaldic acid

Abstract

A new amphiphilic ligand, 8-hexadecyloxyquinaldic acid (HQA), has been synthesized and the characteristics of its monolayer on pure water and on CuSO ₄ aqueous solution have been examined. The HQA monolayer can interact with copper ions in the subphase, and crystallization of CuSO ₄ ·5H ₂ O is induced under the monolayer. In order to understand the relationship between the different states of the monolayer and the induced inorganic crystallization, several typical states of the monolayer were chosen in our experiment. The results show that, when the monolayer is in the gas or liquid phase, its ability to control the oriented crystallization is poor. However, rather than the most dense phase, the most favorable state for oriented crystallization is the one with an area per molecule A = 17.0 Å ² , which could be considered as a liquid solid phase. This is attributed to a coordination effect and lattice matching at the inorganic/organic interface. Our research suggests that the state of the monolayer is a very important factor during the process of induced oriented crystallization.