A rapid, green and versatile route to synthesize metal carbonate superstructures via the combination of regenerated silk fibroin and compressed CO2

Abstract

In this work, a series of metal carbonate minerals such as BaCO₃, SrCO₃, MnCO₃, PbCO₃ and CdCO₃ with uniform and well-defined morphology were synthesized via the combination of regenerated silk fibroin (RSF) and compressed CO₂. The as-prepared samples were systemically characterized by means of TEM, SEM, XRD, TGA and FTIR. The results showed the size, morphology, and nanostructure of crystals could be well controlled by altering the RSF concentration and crystallization time. Based on the time-resolved experiments, we found a spherical BaCO₃ superstructure was formed by RSF chains induced stacking of needle-like units, following a “rod-to-dumbbell-to-twined sphere-to-sphere” morphological evolution process. In addition, both amorphous phase and a dissolution–recrystallization process of BaCO₃ were observed in crystallization. Finally, a probable crystallization mechanism for the formation of spherical BaCO₃ aggregates was proposed based on the experiments.