Study of the Effect of Temperature on the Size of Silver Nanoparticles Synthesized Using the Green Tollens Method

The work adopts a green chemistry strategy by modifying a widely used traditional route for silver nanoparticles, where Tollens' reagent is conventionally reduced by formaldehyde. In this approach, a safer and more sustainable system is employed.

Tollens' reagent was freshly synthesized in the laboratory and subsequently reduced using an extract derived from black tea leaves. The reaction was carried out at controlled temperatures of 30°C, 50°C, and 70°C. The obtained nanoparticles were analysed through X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), UV-Visible spectroscopy, and Fourier Transform Infrared Spectroscopy (FTIR).

XRD, TEM, and UV-Visible analyses confirmed the formation of high-purity, predominantly spherical silver nanoparticles at all three reaction temperatures, with particle size increasing consistently from 2-35 nm at 30°C to 30-100 nm at 50°C and 30-150 nm at 70°C.

The observed size increase is attributed to accelerated nucleation and growth kinetics, Ostwald ripening, and particle fusion at higher reaction temperatures, indicating that reaction temperature is an effective and controllable parameter for tuning nanoparticle size in this green synthesis route.

The developed eco-friendly synthesis route offers a safe and economical alternative for nanoparticle production.