The crystalline properties of silica biomorphs vary within and between morphologies

TL;DR

This study uses advanced 3D imaging techniques to reveal how the crystalline properties of silica biomorphs vary within and between different morphologies, providing insights into their formation and growth mechanisms.

Contribution

It introduces a detailed 3D analysis of crystalline texture in silica biomorphs, linking local properties with growth models and synthesis parameters.

Findings

Crystalline properties vary significantly within single biomorph structures.

Different growth motifs are observed across various morphologies.

A systematic change in crystalline properties correlates with morphology.

Abstract

Silica-carbonate biomorphs are a class of emergent materials, i.e. composite microstructures made of nanometric carbonate crystallites surrounded by amorphous silica. They form via a co-precipitation process in an interplay between alkaline earth metal carbonate and siliceous species, and self-organize into a multitude of shapes with a distinct long-range order of the carbonate nanocrystals. As model systems silica-carbonate biomorphs are frequently studied to examine the self-organization of life-like structures under extreme geochemical conditions. Further, due to their optical properties they lend themselves as a platform for optical, electronic or magnetic functionalization. A big hurdle in this task is our incomplete understanding of the underlying formation process and how the interplay between synthesis parameters affects important nanoscale properties such as crystalline structure and texture, as well as the shape on the microscale. Here, we use X-ray texture and diffraction tomography to unveil the local crystalline texture in 3D of silica-witherite biomorphs. We find surprisingly different growth motifs across different morphologies, but also that the crystalline properties vary significantly within a single structure. We distinguish different growth regimes which we discuss, connecting experimental findings with present literature on biomorphs as well as with silicate chemistry. We observe a systematic change of crystalline properties across and within the different morphologies. On this basis, we provide a detailed unified scheme that links the measured spatially resolved crystalline properties of the distinct complex morphologies with the existing literature models on their growth, underlining the importance of silicate oligomerization for the formation of biomorphs.