Photosensitized synthesis of silver nanoparticles using Withania somnifera leaf powder and silver nitrate

• Synthesis at ambient conditions by environment friendly method.
• Photosensitized accelerated reaction rate reduces reaction time up to 5 min.
• Use of optical filters show possible involvement of blue photosensory proteins in the reduction process.
• Small and stable monodispersed particles, no surfactant for stabilization.
• Move towards the elucidation of bioreduction mechanism.

The metal nanoparticle synthesis is highly explored field of nanotechnology. The biological methods seem to be more effective; however, due to slow reduction rate and polydispersity of the resulting products, they are less preferred. In the present study, we report rapid and facile synthesis of silver nanoparticles at room temperature. The exposure of reaction mixtures containing silver nitrate and dried leaf powder of Withania somnifera Linn to direct sunlight resulted in reduction of metal ions within five minutes whereas, the dark exposure took almost 12 h. Further studies using different light filters reveal the role of blue light in reduction of silver ions. The synthesized silver nanoparticles were characterized by UV–Vis, Infrared spectroscopy (IR), Transmission Electron Microscopy (TEM), X-ray Diffraction studies (XRD), Nanoparticle Tracking Analysis (NTA), Energy Dispersive Spectroscopy (EDS), and Cyclic Voltammetry (CV). The Antibacterial and antifungal studies showed significant activity as compared to their respective standards.

Blue light photosensory proteins respond to the visible radiation and undergo reduction. The universal electron carriers act as electron source. The relaxation of excited state proteins is accompanied by the reduction of silver ions.Figure optionsDownload as PowerPoint slide