Facile fabrication of silver nanoparticle embedded CaCO3 microspheres via microalgae-templated CO2 biomineralization: application in antimicrobial paint development

Abstract

We describe an efficient and environment-friendly approach to synthesizing porous calcium carbonate (CaCO₃) microspheres via carbon dioxide (CO₂) mineralization using naturally occurring microalgae as a bio-template. The CaCO₃ microspheres showed a surface area of 39.1 m² g⁻¹ with pore diameters ranging between 12 and 30 nm. Exploiting its highly porous trait, this bio-mimetically manufactured particle was used as an inert support for silver nanoparticles (nAg). The characteristics of the composite Ag-embedded CaCO₃ microspheres were examined by FE-SEM, TEM, XRD, BET surface area analysis, XPS and TG-DTA, confirming that the nAg particles were compatible with and uniformly distributed on the CaCO₃ microspheres. This novel composite, when added in some commercial paints, showed a rather expected yet potent antimicrobial activity against model bacteria such as Escherichia coli, Psychrobacter alimenterius and Staphylococcus euroum. The minimum bactericidal concentration to kill 99% of bacteria was found to be 0.1 mg mL⁻¹. Moreover, this potency was not accompanied by any quality degradation of the paint color. In view of all this, it is believed that the proposed “green” way of making CaCO₃ microspheres has great potential for commercialization.