Green Synthesis of Eosin-Y Coated Silver Nanoparticles for Sensitive and Selective Fluorometric Detection of L-Dopa

This study is to produce biogenic silver nanoparticles (AgNPs) by utilizing aqueous extracts derived from Turnera Sublata (TS) leaves under visible light. Subsequently, these nanoparticles are coated with eosin-yellow (EY) to enhance sensitivity and selectivity in L-3,4-dihydroxyphenylalanine (L-dopa) detection. This method encompasses the deposition of metal onto the Ag NPs, resulting in the formation of EY-AgNPs. The crystalline, spherical nanoparticles, prepared as described, exhibit a particle size of 20 nm. Different instruments were used to characterize them, including UV-Vis spectroscopy, fluorescence spectroscopy, FTIR spectroscopy, selected area electron diffraction (SAED), transmission electron microscopy (TEM), and X-ray diffraction (XRD) analysis. The spherical structured morphology and size of the EY-AgNPs has been confirmed through SAED and TEM studies. This study pioneered the integration of characteristic hydroxyl-Ag chemistry and specialized steric interference of organic pigment in luminescent AgNPs to develop a simple method for detecting dopa. The sensor's dynamic range and limit of detection were assessed. Experimental results revealed that green-emitting AgNPs shielded by interference from biogenic AgNPs and the strong affinity of hydroxyl-silver provided a high-sensitivity detection limit of 1.84 nM. Furthermore, a new green approach for sensor development using human serum albumin (HSA) assay demonstrated that organic dye on the surface of nanomaterials further enhances sensing properties.