Biogenic synthesis of gold–palladium bimetallic nanoparticles using Passiflora edulis fruit peel extract for catalytic reduction of rhodamine B and methyl orange dyes
摘要
This study reports a green synthesis of bimetallic gold–palladium nanoparticles (Au–Pd BNPs) using Passiflora edulis fruit peel extract as a sustainable reducing and stabilizing agent. Transmission electron microscopy revealed uniformly dispersed spherical nanoparticles with a core–shell structure, comprising a dense Au core and a thinner Pd shell, and an average diameter of 15.9 ± 2.4 nm. The core–shell architecture was further confirmed by X-ray diffraction (XRD), while Fourier-transform infrared spectroscopy (FTIR) indicated the involvement of hydroxyl and carbonyl-containing phytochemicals in nanoparticle formation. X-ray photoelectron spectroscopy (XPS) verified the presence of elemental Au and Pd in Au–Pd BNPs. The catalytic activity of monometallic (AuNPs, PdNPs) and bimetallic (Au3Pd1, Au1Pd1, Au1Pd3) nanoparticles was assessed in the NaBH4-assisted reduction of rhodamine B (RhB) and methyl orange (MO). Among all catalysts, Au1Pd3 BNPs exhibited superior performance, achieving > 99% reduction of both dyes within 5 min. The reactions followed pseudo-first order kinetics, with apparent rate constants of 14.7 ± 0.6 × 10−3 s−1 for RhB and 16.1 ± 0.5 × 10−3 s−1 for MO, obtained from the nonlinear exponential fitting. These findings highlight the effectiveness of green-synthesized Au–Pd BNPs as promising catalysts for rapid and efficient dye degradation.