ECO-FRIENDLY SYNTHESIS OF SELENIUM NANOPARTICLES USING RHODODENDRON EXTRACT AND THEIR ANTIMICROBIAL PROPERTIES

Abstract

The biological utility of selenium nanoparticles (SeNPs) rests on a favorable combination of selenium’s nutritional role with the surface chemistry available at nanoscale; nonetheless, their movement into medical applications continues to be hindered by the harsh reagents and high energy requirements typical of solution-phase chemical methods. The work reported here describes an aqueous, phytochemically driven preparation of SeNPs that uses four separately prepared extracts of Rhododendron arboreum — derived from flower, leaf, stem, and root extracts— sampled from a high-altitude population in the Garhwal Himalaya, and benchmarks the resulting batches (designated SeNP-PF, SeNP-PL, SeNP-PR, SeNP-PS) across structural and antimicrobial endpoints. Treatment of 1 mM selenious acid with each extract at 65 °C for 15 min produced a striking transition from pale yellow to ruby pink, a visual signature of Se(IV) reduction. UV–visible spectroscopy located a surface plasmon resonance feature in the 500–550 nm window, with the strongest absorbance under near-neutral conditions; FTIR returned hydroxyl, carbonyl, and C–O bands at ≈3339, 1634, and 1125–1257 cm−1 that are consistent with phenolic-based capping. SEM and TEM observations showed rounded to irregular electron-dense features, with differences in their observed distribution and aggregation among plant-part-derived preparations. In agar-well diffusion screening, stem-derived SeNP-PS produced the largest single inhibition zones against Salmonella sp. (14 mm) and Actinobacteria (13 mm), while flower-derived SeNP-PF was strongest against Pseudomonas sp. (13 mm). We report here a plant-part-resolved evaluation of R. arboreum-mediated SeNP synthesis and biological activity.