Biogenic synthesis of silver nanoparticles using leaf extracts of <i>Chromolaena odorata, Tithonia diversifolia</i> and <i>Solenostemon monostachyus</i>

Abstract

Silver nanoparticles (AgNPs) are highly valued across various scientific fields for their diverse applications in daily life. Sustainable and eco-friendly methods are essential for their synthesis. This study demostrated an alternative, safe, cost-effective and environmentally-friendly approach by utilising leaf extracts from Chromolaena odorata (CO), Tithonia diversifolia (TD) and Solenostemon monostachyus (SM) to biogenically synthesise AgNPs. The resulting colours indicating AgNP synthesis were brown, yellow and brown, respectively. Characterisation of the AgNPs was conducted using UV-Vis spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM). UV-Vis spectra exhibited strong absorption peaks at 445 nm, 437 nm and 430 nm for AgNPs synthesised with CO, TD and SM leaf extracts, respectively. The synthesised AgNPs displayed predominantly spherical morphology, with some triangular and rod-like shapes observed in CO AgNPs, averaging 27.48 nm, 49.64 nm, and 25.76nm in size for CO, TD and SM, respectively. FTIR analysis revealed absorption bands at specific wavenumbers, indicating the importance of carbonyl stretch of amides and O–H functional group vibrations in the bio-reduction, capping and stabilisation of AgNPs.