Water-Processable Intercalated Graphitic Pyroproteins and Electromechanic Properties for Smart Structural Bricks

This study introduces a novel method for synthesizing phosphate-intercalated graphitic pyroprotein (P-GPy) using the regeneration process of silk fibroin (SF). SF was prepared by mixing degummed silk fibers and calcium chloride (CaCl₂) in formic acid, resulting in a silk I-like conformation, which was then converted into silk II by being redissolved in phosphate buffer (PBS). We find that the β-sheet structure of silk II is transformed to an sp²-hybridized carbon structure by simple heating. Techniques such as Raman, XRD, and SEM with EDS mapping demonstrate successful creation of P-GPy characterized by a uniform phosphate distribution. We demonstrate the exfoliation in water of P-GPy in layered graphene sheets. SF dissolved in PBS was added to clay, and the thermal treatment required for firing the refractory bricks is used to obtain P-GPy. Electrical impedance spectroscopy was employed to investigate the piezo-impedance and piezoresistive behaviors of clay-based P-GPy composites, demonstrating the potential of the fabricated bricks to function as smart strain sensors for structural health monitoring.