Evaluation of Aqueous and Ethanolic Extracts for the Green Synthesis of SnO<sub>2</sub> Nanoparticles from Fresh <i>Senna alata</i> Leaves

Abstract

Fresh leaves provided active phytochemicals that acted as reducing, capping, and stabilizing agents, while the solvent dictated their extraction and interaction with growing nanoparticles. Controlling the size, morphology, and optical properties of SnO₂ nanoparticles remains challenging due to limited understanding of how solvent selection influences phytochemical-mediated nanoparticle formation. This study addresses this problem by employing a green synthesis approach using a 1.0 M solution of tin (II) chloride dihydrate (SnCl₂·2H₂O) as a precursor and fresh Senna alata leaf extracts as an environmentally friendly reducing, stabilizing and capping agent prepared in water and ethanol. Structural, morphological, and optical properties of the synthesized nanoparticles were studied. X-ray diffraction confirmed phase-pure tetragonal rutile SnO₂, with ethanolic extracts producing larger crystallites (9.06 nm) and higher crystallinity than aqueous extracts (3.70 nm). FTIR revealed stronger surface coordination in ethanolic samples, and SEM/TEM showed smaller, more uniformly dispersed nanoparticles (8.73 nm) versus moderately agglomerated aqueous-derived particles (9.79 nm). Optical studies indicated enhanced UV absorption, higher transparency, and a lower band gap (3.05 eV) for ethanolic extract-mediated nanoparticles. These findings demonstrate that solvent choice critically influences nanoparticle properties, and fresh Senna alata extracts in ethanol offer a potential green route to SnO₂ nanoparticles with tunable structural, morphological, and optical characteristics for optoelectronic, photocatalytic, gas sensing, and solar energy applications.