Facile Green Synthesis of Silver Nanoparticles Using Euphorbia neriifolia Leaf Extract: A multi-spectroscopic, Calorimetric, Molecular Docking Interaction Studies with Human Serum Albumin.

A sustainable, efficient, and eco-friendly approach was developed to synthesize silver nanoparticles using Euphorbia neriifolia leaf extract. The biosynthesized Euphorbia neriifolia silver nanoparticles (ENSNPs) were comprehensively characterized using several techniques, including absorbance spectroscopy, Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, and dynamic light scattering. ENSNPs quenched the intrinsic fluorescence of human serum albumin (HSA) with a quenching constant of 1.10 ± 0.004 × 10⁸ M^- 1 at 298.15 K, and the Time-correlated single-photon counting experiment clearly indicated that the quenching mechanism is static. Moreover, synchronous spectroscopy, 3D fluorescence spectroscopy, and circular dichroism spectra further revealed that the microenvironment of amino acid residues in HSA was slightly changed after interaction with ENSNPs. The thermodynamic investigation and docking analysis collectively showed that HSA-ENSNPs complexation was driven by hydrogen bonding, pi-alkyl interactions, and Van der Waals forces, providing insight into the nature of the binding interactions and the stability of the complex.