Biodirected synthesis of palladium nanoparticles using Phoenix dactylifera leaves extract and their size dependent biomedical and catalytic applications

The emerging microbial resistance and increased water pollution are of serious concern around the globe. In order to cope with these problems, new strategies are needed to develop less toxic and more effective nanomaterials that could arrest the microbial growth and eliminate unwanted organic pollutants from water samples. In the present contribution, we report the green synthesis of palladium nanoparticles using the aqueous extract of Phoenix dactylifera leaves. The appearance of a characteristic surface plasmon resonance peak at 278 nm confirmed the synthesis of palladium nanoparticles (UV-vis spectroscopy). The formation of the PdNPs was optimized at different temperatures (30 degrees C, 60 degrees C and 90 degrees C) and varying amounts of leaf extract (5 mL, 10 mL and 20 mL) in order to control their size, shape and dispersion. Average particle sizes of 13, 5, and 21 nm were observed by using the leaf concentrations of 5, 10, and 20 mL, respectively (HRTEM, DLS), with a fixed amount of PdCl2 (0.003 M) at 60 degrees C. The PdNPs synthesized under the optimized conditions (10 mL extract + 60 degrees C + 0.003 M PdCl2) were spherical in shape, small sized and uniformly distributed (HRTEM). The biologically synthesized nanoparticles were tested for their size dependent biomedical and catalytic applications. The PdNPs synthesized under optimized conditions exhibited strong catalytic activity with a complete reduction of 4-nitrophenol to 4-aminophenol in only 2 min. These nanoparticles were highly active in scavenging DPPH free radicals. The optimized palladium nanoparticles also exhibited strong antibacterial efficiency against Pseudomonas aeruginosa 26 (+/- 0.8 mm). This high activity of PdNPs may be due to their small size, high dispersion and surface capping phytochemicals.