Colloidal Ag@Pd core–shell nanoparticles showing fast catalytic eradication of dyes from water and excellent antimicrobial behavior

Abstract

Colloidal Ag@Pd core–shell nanoparticles (NPs) were synthesized in aqueous medium following the citrate method. The progress of formation of the nanoparticles was monitored by ultraviolet–visible (UV–Vis) spectrophotometry. The core–shell nanoparticles were further characterized by Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM), revealing their spherical shaped core–shell structure with particle size of around 9.8 nm. Degradation of Congo Red, Direct Blue 14, and Sunset Yellow dyes were selected as model reactions to demonstrate the high catalytic activity of the Ag@Pd core–shell NPs. The colors of the dyes disappeared within about 12–25 min at room temperature. The degradation efficiency of Direct Blue 14 (94.57 %) was greater than that of Congo Red (90.23 %), which was greater than that of Sunset Yellow (83.56 %). The combination of the dye, NaBH4, and the core–shell nanocatalyst in a one-pot system was a key factor for in situ destruction of the dye in solution. This work provides an applicable route for decontamination of dye-containing wastewater. The antimicrobial activity of the Ag@Pd core–shell NPs was evaluated qualitatively and quantitatively against model microbial organisms by calculating the minimum inhibitory concentration using the disk diffusion method. The inhibitory effect against bacteria and fungi increased with increase in the concentration of the core–shell NPs up to concentration of 25 mg/ml, indicating broad-spectrum activities.