Microwave assisted green synthesis of palladium nanoparticles using dragon fruit peel extract for catalytic reduction of 4-nitrophenol and methylene blue

This study investigated the use of waste dragon fruit peel extract (DF) as a reducing and stabilizing agent for preparing palladium nanoparticles (PdNPs) using a microwave-assisted technique. The effects of various synthetic parameters including pH, PdCl₂ concentration, and DF concentration on PdNPs production were examined in detail. Several techniques were employed to characterize the morphology, microstructure, functional groups, and crystallinity of as obtained nanoparticles (DF@PdNPs). The formation of PdNPs in the reaction solution was confirmed by a visible black color and broad surface plasmon absorption in the UV–vis spectrum. FTIR studies revealed the role of phytochemicals in nanoparticle reduction and stability. The produced PdNPs were spherical/oval in shape, evenly polydisperse, had an average size of 9±1.5 nm, and were well stabilized (zeta potential =  − 36.3 mV) by the extract phytochemicals. They also had a face-centered cubic crystal structure. The catalytic performance of DF@PdNPs was assessed by the NaBH₄ assisted reduction of 4-nitrophenol to 4-aminophenol, with a kinetic constant value of 0.155±0.029 min⁻¹. Furthermore, the catalyst successfully reduced methylene blue dye within 6 min, with a rate constant of 0.422±0.021 min⁻¹