Lipophilic lignocellulose -supported Palladium nanoparticles: A green efficient and recyclable heterogeneous catalyst for the aerobic oxidation of alcohols

In the recent years, bio-based economy and use of renewable biomass as the raw material have been considered as sustainable options to tackle the problems associated with local and global pollutions [1]. Along this line, lignocellulosic agricultural waste as one of the most abundantly available agricultural wastes has been advocated as a choice for the production of fine chemicals such as nanomaterials [2]. On the other hand, due to cheapness and safety of water, performing organic reactions in this medium is now of great interest. In this work we have presented a new green, simple and inexpensive method of making palladium nanoparticle (PdNP) catalyst supported on lipophilic walnut shell as an abundantly available lignocellulose-rich agricultural waste. Lipophilization of walnut shell has been performed by Zycosil. Zycosil is low-cost and industrially available organosilicon-based material and the only water soluble product in the world that is used waterproofing of masonry building material, concrete, limestone, marble, stone, stucco, clay tile, plaster, sand, soil, and aggregates. TEM image of Lipophilic walnut shell -supported PdNPs (PdNP@LWS) indicates the formation of 10 nm sized palladium nanoparticles. The catalyst is quite effective for the oxidation of benzylic and aliphatic alcohols under atmospheric pressure of air in aqueous phase. More importantly, we tested the cytotoxic potential of PdNP@LWS on the erythroleukemia K562 cancer cell lines and peripheral blood mononuclear cells (PBMCs) as normal cells. The K562 cells or PBMCs (1×105 cells/100 µL/well) were incubated for 24 h with serial dilution of PdNP@LWS (0, 50,100,200 and 400 µM). After incubation, the survivability of present cells was determined by MTT method. Obtained data showed that PdNP@LWS had cytotoxic effects against K562 cell-line in a dose-dependent manner. Fortunately, the inhibitory concentration (IC50) value of PdNP@LWS against K562 cell line was significantly smaller than an IC50 value of PdNP@LWS against PBMCs (150.54±5.1 µM vs. 275 ±9 µM). In conclusion, PdNP@LWS may provide a selective favorable cytotoxicity against K562 cancer cell-line.