Synthesis, characterization, optical and antimicrobial studies of polyvinyl alcohol–silver nanocomposites

•Silver nanoparticles were synthesized by chemical reduction method.•TEM studies showed that the average particle size of Ag NPs was about 19 nm.•Optical band gap of PVA was reduced under addition of Ag NPs.•The antimicrobial activity of PVA was enhanced under addition of Ag NPs.

Silver nanoparticles (Ag NPs) were synthesized by chemical reduction of silver salt (AgNO3) through sodium borohydride. The characteristic surface plasmon resonance band located at around 400 nm in the UV–Visible absorption spectrum confirmed the formation of Ag nanoparticles. Polyvinyl alcohol–silver (PVA–Ag) nanocomposite films were prepared by the casting technique. The morphology and interaction of PVA with Ag NPs were examined by transmission electron microscopy and FTIR spectroscopy. Optical studies show that PVA exhibited indirect allowed optical transition with optical energy gap of 4.8 eV, which reduced to 4.45 eV under addition of Ag NPs. Optical parameters such as refractive index, complex dielectric constant and their dispersions have been analyzed using Wemple and DiDomenco model. Color properties of the nanocomposites are discussed in the framework of CIE L∗u∗v∗ color space. The antimicrobial activity of the nanocomposite samples was tested against Gram positive bacteria (Staphylococcus aureus NCTC 7447 & Bacillus subtillis NCIB 3610), Gram negative bacteria (Escherichia coli, NTC10416 & Pseudomonas aeruginosa NCIB 9016) and fungi (Aspergillus niger Ferm – BAM C-21) using the agar diffusion technique. The antimicrobial study showed that PVA has moderate antibacterial activity against B. subtillis and the 0.04 wt% Ag NPs composite sample effect was strong against S. aureus.

Graphical abstractTEM image of the Ag colloids.Figure optionsDownload full-size imageDownload as PowerPoint slide