Self-assembled nanocrystals of barium carbonate in biomineral-like structures

Growth Behavior and Kinetics of Self‐Assembled Silica–Carbonate Biomorphs

“…[10,15] Other work provided evidence that significant amounts of silica also occur in the core and are intertwined with the carbonate phase, possibly sheathing individual crystallites. [8,11] Our data provide direct information on the role of silica and the degree of incorporation into the aggregates during growth (cf. Figure 4 a).…”

The epitaxial role of silica groups in promoting the formation of silica/carbonate biomorphs: A first hypothesis

“…As a matter of fact, the precipitation of orthorhombic alkaline earth carbonates such as the witherite (BaCO 3 ) and the strontianite (SrCO 3 ) in basic silica-rich environment results in the formation of poly-nano-crystalline aggregates exhibiting non-crystallographic shapes like helicoidal filaments or very thin sheets describable by the equation of a cardioid. These objects, named ''silica biomorphs'' [12][13] because their morphology resembles that of primitive organisms, originate from carbonate precipitation in Na-MTS gels and/or stagnant aqueous solutions [14].…”

“…In the first part of the present work we will focus the role of silicate species (as derived from Na-MTS hydrolysis) on the crystallization medium, being already known that the observed morphologies vary according to other variables such as pH, temperature and fluiddynamic conditions [14][15][16][17][18][19][20]. From literature [9] and our recent investigation [14] it comes out that the mean size of BaCO 3 crystals changes significantly with the concentration of silicate species either in gel or in aqueous mother solution; this was proved through SEM and TEM observations and clearly confirmed by X-ray powder diffraction (XRPD) patterns. Further, we will use the information resulting from the observed witherite/a-quartz 3D-epitaxy [21] to justify the inverse and not yet observed aquartz/witherite 2D-epitaxy; this to quantitatively explain how the nucleation rate of witherite dramatically increases, from pure aqueous solutions to the doped ones, with the increasing MTS concentration.…”

Morphological Biosignatures in Early Terrestrial and Extraterrestrial Materials

“…However, these controversies have been useful in spurring new developments in the understanding of bona fide biosignatures. For instance, examples of advances that have been made include a better understanding of the size limits of cellular life (NRC 1999, on Size Limits of Very Small Microorganisms), mixed carbonaceous/mineral abiogenic bacteriomorphs (Garcia-Ruiz et al 2003;Bittarello and Aquilino 2007), abiogenic production of carbon having isotopic signatures similar to those of microorganisms (van Zuilen et al 2002).…”