Spectroscopic study of silver halides in montmorillonite and their antibacterial activity

- The AgX (X = Cl, Br, I)-MMT nanocomposites were synthesized by dispersion method.
- There are low data about comparing the antibacterial activity of silver halides in matrices.
- The produced Ag NPs and Ksp had an important role in antibacterial activity of AgX-MMT.
- AgI-MMT did not produce Ag nanoparticles due to small band gap.
- The stability of AgI in MMT was more than AgCl and AgBr.

In this study silver halides (AgX, X = Cl, Br, I) in montmorillonite (MMT) were prepared by dispersion method in dark. AgNO3 was used as a silver precursor. The nanocomposites (NCs) (AgX-MMT) were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and ultraviolet-visible diffuse reflectance spectroscopy (DRS). The powder X-ray diffraction showed intercalation of AgCl and AgBr nanoparticles (NPs) into the clay interlayer space. The diffuse reflectance spectra indicated a broad surface plasmon resonance (SPR) absorption band in the visible region for AgCl-MMT and AgBr-MMT NCs, resulting of metallic Ag nanoparticles (Ag NPs). But the results were opposite in case of AgI-MMT NC. The antibacterial activity of NCs was investigated against Gram-positive bacteria, i.e., Staphylococcus aureus and Micrococcus luteus and Gram-negative bacteria, i.e., Escherichia coli, Pseudomonas aeruginosa, by the well diffusion method. The antibacterial effects on Staphylococcus aureus, Micrococcus luteus and Escherichia coli decrease in the order: AgCl-MMT > AgBr-MMT > AgI-MMT. No antibacterial activity was detected for Pseudomonas aeruginosa.

Graphical Abstract