A scalable exfoliating approach to achieve high-quality shell nanosheets with large lateral size and surface functionalization

With rapid development of global marine aquaculture, large amounts of waste shellfish as an aquaculture by-product are generated after consumption. At present, waste seashell powder (WSP) as fillers mixed with polymers is a potentially efficient method to add-value recycle WSP, but the poorly compatibility and seriously agglomeration of WSP results in the low mechanical properties and then reduces the value of recycled shell-based products. In this study, a facile ball-milling exfoliation method with the assistance of polyethyleneimine (PEI) to exfoliate shell materials into high-quality shell nanosheets (SNs) is present. In this case, PEI macromolecular had dual function: it not only acted as a buffer between milling balls and WSP to prevent excessive breaking of the WSP, but also interacted with active bonds on the surface to functionalize the SNs. As a demonstration, the high quality SNs achieve an average lateral size of 414 nm and thickness of 5 nm. Furthermore, the grafting of hydroxyl and amine functional groups onto the SNs, along with the low surface energy of the resulting SNs, has the potential to enhance interfacial interactions with the polymer matrix, thus promoting the overall performance of shell-based composites. This work presents a green and scalable approach for the value-added recycling of waste seashells, offering a sustainable solution to address the environmental impact of aquaculture by-products.