The wet chemical synthesis of surfactant-capped quasi-spherical silver nanoparticles with enhanced antibacterial activity

Abstract

Capped silver nanoparticles (AgNPs) are used in many applications in the biomedical field because of their unique structural flexibility. Herein, a viable chemical reduction synthesis method for AgNPs is described employing ionic surfactants as stabilizing as well as capping agents. Stabilized AgNPs of a quasi-spherical shape were obtained using silver nitrate (AgNO₃) as a precursor and sodium borohydride (NaBH₄) as a reducing agent under multiple ionic micellar hierarchical approaches. UV-Visible spectroscopy studies showed characteristic single and sharp absorbance peaks in the range 400 to 420 nm, which indicates the absence of the self-aggregation of AgNPs, whereas the FTIR results indicated the surfactant functionalities responsible for the stability of the AgNPs. Micrographs of the as-obtained AgNPs, obtained via electron microscopy (SEM, STEM), demonstrated a fine monomodal collection of spherical nanoparticles of <15 nm, which was further confirmed by dynamic light scattering (DLS) measurements. Moreover, the stability of the as-synthesized AgNPs was evaluated by determining the charge present on the surface, i.e., positive or negative, indicating the stability of the monodispersed AgNPs against flocculation. The bactericidal ability of the surfactant capped AgNPs was checked by measuring the zone of inhibition using the agar-well diffusion method. The results indicated that CTAB-AgNPs and SDS-AgNPs showed enhanced bactericidal effects, whereas DDAB-AgNPs, DOSS-AgNPs, and MES-AgNPs showed no significant activity against multidrug-resistant strains of bacteria.