Ag/AgCI nanoparticle decorated layered double hydroxides: synthesis, characterization and antimicrobial properties

摘要

A layered double hydroxide (LDH) surface was employed as a substrate for growing silver nanopartides (NPs), An efficient method to produce stable silver/silver chloride nanopartides supported on the ZnAI-LDH surface was developed. NPs of AgCI were grown on the ZnAI-LDH surface by using AgNO3 as the silver source. The ZnAI-LDH in chloride form acts as a nucleating agent, and depending on the pH of the LDH dispersion, AgCINPs with different dimensions were obtained. In particular AgCINPs with a diameter of 60 nm were formed at pH 5. The AgCINPs supported on LDH sheets were partially reduced by different reducing agents (NaBH4 and formaldehyde) resulting in a Ag/AgCI-LDH nanocornposite. The silver chloride and silver NP dimensions were evaluated by X-ray powder diffraction, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). UV-Vis spectra of the samples upon reduction showed a band centred at 415 nm due to the surface plasmon resonance of silver nanopartides with a diameter of about 10 nm, in agreement with the TEM analysis. The AgCI-LDH and Ag/AgCI-LDH nanocomposites, subjected to antimicrobial tests, exhibited good antimicrobial activity against both Gram-negative (Pseudomonas aeruginosa) and Gram-positive (Staphylococcus epidermidis and S. aureus) bacteria and yeast (Candida albicans). The nanocomposites were also studied for their ability to release silver by obtaining release curves, under conditions of antibacterial assays. Finally, the nanocomposites antibacterial behavior, as a function of time, was investigated by performing time-kill experiments using S. aureus and Candida albicans.