Living organisms have evolved effective mechanisms to control the growth of inorganic crystalline materials as structural elements. Previous research has shown that proteins rich in aspartic acid play a pivotal role in driving crystalline orientation, structure, and morphology of calcium carbonate biominerals in the formation of shells in marine bivalves (mussels, clams, abalone). In our research, we examine the effect of aspartic acid on the growth of calcium carbonate by a novel vapor diffusion-based growth technique. The vapor diffusion approach uses a gas-permeable membrane as a barrier to control the physical location of crystal growth. In this way, we are able to directly observe the crystal nucleation and growth using optical microscopy and record changes in growth rates and crystal orientation as we add peptide or polyelectrolyte-based modifiers to the growing crystals. Raman spectroscopy was employed to characterize the resulting crystals and provide insight into the actions of the growth modifiers. Our work is directed towards understanding how molecular modifiers interact with inorganic materials. Developing controls for the growth of calcium carbonate materials could have impacts in many industries which rely on the materials (including pharmaceutical development, household products, and paper, rubber, and paint manufacturing)
