Smart plasmonic Ag/Ag2O/ZnO nanocomposite with promising photothermal and photodynamic antibacterial activity under 600 nm visible light illumination

Photoactivated antibacterial activity is a very promising strategy to fight bacteria without inducing bacterial resistance. This contribution combines the photodynamic and photothermal properties along with plasmonic effect in a single nanocomposite to effectively kill bacteria. Plasmonic Ag/p-Ag2O/n-ZnO heterojunction nano -composites with well-defined morphologies are synthesized via solution combustion using glycine and Thymus vulgaris extract as fuels. Ag/Ag2O/ZnO shows excellent photothermal conversion behavior under 600 nm light illumination. ESR analysis confirms the production of reactive species (ROS) under 600 nm. Ag acts as a plas-monic material enhancing the light absorption in the visible region. FT-IR confirms the presence of Thymus vulgaris-related function groups on the surface of the prepared nanocomposite which also contribute to enhancing the antibacterial activity. Ag/Ag2O/ZnO shows promising antibacterial activity under 600 nm illu-mination against Enterococcus faecalis. Moreover, the nanocomposite shows excellent antibacterial activity against C. albicans and S. epidermidis in the dark. The efficient bacterial killing under 600 nm light illumination is attributed to the synergetic effects among photothermal, photodynamic, and plasmonic effects. The antibacterial activity in the dark is due to the intrinsic antibacterial activity of Ag, ZnO, and Ag2O along with Thymus vulgaris plant extract. Cytotoxicity of Ag/Ag2O/ZnO on Huh-7 human liver cancer cells line is also investigated and the IC50 values calculated are 112.9 and 313 mu g/mL for the Ag/Ag2O/ZnO samples prepared using 3 ml (3AgZn) and 7 ml AgNO3 (7AgZn), respectively.

Automated summary

Photoactivated antibacterial activity is a promising strategy to combat bacteria without inducing resistance. This study combines photodynamic, photothermal, and plasmonic effects in a nanocomposite to effectively kill bacteria. The nanocomposite shows excellent antibacterial activity under 600 nm light illumination and in the dark, attributed to the synergistic effects of photothermal, photodynamic, and plasmonic effects, as well as the intrinsic antibacterial activity of the materials used.