Simple, geochemically feasible reactions such as the co-precipitation of silica and barium carbonate can form inorganic microstructures with biomimetic morphologies. Known as biomorphs, these intriguing materials consist of thousands of co-aligned nanorods that assemble twisted helices, cardioid sheets, and worm-like shapes. Because of their "life-like" form, biomorphs have challenged the use of morphology as an indicator of biogenicity, particularly in the case of early pre-cambrian fossils. However, silica-carbonate biomorphs have to date been grown exclusively in controlled lab environments. We report the synthesis of biomorphs using natural water samples obtained from the Aqua de Ney Springs, California. These springs are known for their unusually high pH (11.9) and silica content (&gt;4000 ppm) which present an ideal chemical environment for biomorph growth. Using the gas-diffusion method, we successfully synthesize hierarchical polycrystalline materials simply by adding calcium or barium ions to the natural water samples. In the case of barium carbonate, the structures consist of co-aligned nanorods and show non-crystallographic, curved morphologies. Image correlation analyses on the SEM micrographs reveal the smoothly changing orientation of the nanorods. In addition, PXRD and ATR-IR measurements confirm the presence of predominantly witherite crystals and amorphous silica. The deviation from the typical biomorph shapes is ascribed to the high ionic strength and the inclusion of dopant species such as calcium and sodium. For the calcium-based experiments, we observe the formation of classical calcite rhombohedra and spherical polycrystalline materials. These results present an exciting example of biomimetic crystallization in natural environments that, in the broader context, is highly relevant to the overlap between fossil sciences and geochemistry.

Geochemically feasible reactions assemble biomimetic microstructures from natural spring water

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.