Probing capping mechanisms and polymer matrix loading of biogenic vaterite CaCO3–Ag hybrid through X-ray photoelectron spectroscopy (XPS)

Abstract

Despite extensive research in the literature, the synthesis of silver nanoparticles (AgNPs) via capping mechanisms remains incompletely understood. This study employs a mechanistic approach to unravel the underlying molecular interactions driving the capping process of biogenic vaterite CaCO₃–Ag and explores their interactions with different polymer matrices. X-ray photoelectron spectroscopy (XPS) was used to reveal the capping mechanisms, surface composition alterations, and vaterite polymorph transitions. The oxidation states of AgNPs exhibited distinct changes under different capping agents. The Ag3d spin–orbit splitting profiles revealed the coexistence of Ag⁺ and Ag⁰ within CaCO₃–Ag, with a significant presence of Ag⁰ when poly(sodium 4-styrene sulfonate) was employed as the capping agent. Conversely, the use of carboxy methyl cellulose as the capping agent resulted in Ag⁺ dominance. XPS analysis illuminated the transformation of CaCO₃ polymorphs from calcite to vaterite structure, which remained stable following embedding within polymer matrices. Integrating CaCO₃–Ag microspheres into polymer matrices and investigating their surface characteristics represents a strategic step toward tailoring material properties for potential applications in active packaging and biomedicine.