Au and Ag nanoparticle-embedded calcium alginate fibers with laminated structure fabricated by molecule-directed self-assembly and cation exchange

Abstract

Hyperbranched poly(amideamine) (HBPAA)-capped Au and Ag nanoparticles (NPs) were synthesized by hydrothermal reduction and then embedded into calcium alginate fibers (CAFs) by HBPAA-directed self-assembly and cation exchange between Ca2+ and HBPAA in aqueous solution to produce an Ag/Au-embedded coating inside the fiber surface. Transmission electron microscopy tests showed that as-prepared Au and Ag NPs possessed positive zeta potential (+34 and +13.5 mV) and had a regular spherical structure with an average particle size of 11.1 and 10.8 nm, respectively. Dual-coated CAFs were fabricated by successive or one-step impregnation of fibers with solutions of HBPAA-capped Au and Ag NPs, respectively, or with their mixed solution. As-prepared dual-coated CAFs have a Ca2+ outer coating and an Ag/Au internal coating. Upon strong electrostatic and hydrogen bonding interactions between HBPAA and alginate and the cation exchange interaction between amino-terminated HBPAAs and Ca2+ in CAFs, HBPAA-capped NPs were nearly completely exchanged to CAF surfaces at room temperature. It was noted that the dissociative Ca2+ can resorb to HBPAA, thereby forming a Ca2+ outer layer on NPs. This interesting structure may serve as a protective layer, avoiding direct contact with the human body and re-dissolution of NPs.