BIOMIMIC GROWTH OF NANO-STRUCTURED MINERALS IN ORGANIC-BEARING SOLUTIONS

Proteins and certain organic molecules can control mineral structures and shapes. The interactions between the functional molecules and the minerals are best represented in diatoms, sea shells, bone tissue and bacterial produced magnetic particles. These natural minerals and biominerals not only have remarkable structural ordering on multiple length scales, but also have well-controlled morphologies. High-pressure polymorph minerals (e.g., aragonite) and high-temperature polymorph minerals (e.g., wurtzite ZnS) can be precipitated with assistance of certain organic molecules at low pressure and low temperature environments. In order to simplify the mechanism of mineral growth in organic-bearing solutions, we used lipid-like surfactants and simple organic molecules with –COOH and –NH2 functional groups to study the effect of organics on mineral growth. Silica precipitates with diatom-like shapes were synthesized through self-assembly of organics and inorganic silica in surfactant-bearing solutions. The shape of precipitated silica changes as surfactant concentration, ratio of two surfactants, or trace metals (e.g., Al) changes is solutions. An organic acid with –COOH functional group can control crystal shape and even seashell-like texture of zincite. Fish-bone like nanostructured zincite can be synthesized in a solution containing an organic with –NH2 functional group. Organic molecules with –NH2 functional group result in the growth of ZnS with wurtzite structure and intergrowth of sphalerite and wurtzite domains, although sphalerite is a thermodynamically stable phase at low-temperature. This study will enhance our understanding of solution—organic—mineral interactions that are critical in mineral formation. Our results will also provide useful information about bacterial origin of minerals in terrestrial samples and open new opportunities for studying possible microbial activities in extraterrestrial samples.