Natural Tubule Clay Template Synthesis of Silver Nanorods for Antibacterial Composite Coating

TLDR

Halloysite is a naturally abundant clay mineral with hollow cylindrical tubes that can serve as scalable templates for producing ceramic‑encapsulated metal nanorods for composite materials. Silver nanorods were formed inside halloysite tubes by loading silver acetate into the lumen through vacuum cycling and thermally decomposing it, with their presence confirmed by STEM‑EDX elemental mapping. TEM revealed 15‑nm silver nanorods and nanoparticles; the nanorods were crystalline with a [111] axis oriented ~68° from the tube axis, and when incorporated into a polymer paint the resulting coating exhibited antimicrobial activity and enhanced tensile strength, while a 5 % silver‑loaded halloysite coating remained color‑stable under light exposure. Images of individual components were included.

Abstract

Halloysite is naturally available clay mineral with hollow cylindrical geometry and it is available in thousands of tons. Silver nanorods were synthesized inside the lumen of the halloysite by thermal decomposition of the silver acetate, which was loaded into halloysite from an aqueous solution by vacuum cycling. Images of individual ca. 15 nm diameter silver nanorods and nanoparticles were observed with TEM. The presence of silver inside the tubes was also verified with STEM-EDX elemental mapping. Nanorods had crystalline nature with [111] axis oriented ∼68° from the halloysite tubule main axis. The composite of silver nanorods encased in clay tubes with the polymer paint was prepared, and the coating antimicrobial activity combined with tensile strength increase was demonstrated. Coating containing up 5% silver loaded halloysite did not change color after light exposure contrary to the sample prepared with loading with unshelled silver nanoparticles. Halloysite tube templates have a potential for scalable manufacturing of ceramic encapsulated metal nanorods for composite materials.