Metal Nanoparticle Loaded Magnetic-Chitosan Microsphere: Water Dispersible and Easily Separable Hybrid Metal Nano-biomaterial for Catalytic Applications

We report a green synthesis of magnetically separable hybrid metal nanobiomaterial as water dispersible and recyclable catalysts. The hybrid nanobiomaterial was prepared in a three-step process. The magnetic nanoparticles were initially synthesized by biomineralization process and coated with chitosan followed by binding and reduction of metal ions, which led to the formation of a magnetically separable hybrid nanobiomaterial (Fe3O4@Ch-MNPs, M = Au, Pd). The chemical composition, morphology, thermal stability, and magnetic behavior of the hybrid nanobiomaterial were characterized with zeta potential, Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and field emission scanning electron microscopy (FESEM) analysis. The FESEM measurement demonstrated formation of highly dispersed Au and PdNPs on the surface of nanobiomaterial, while thermogravimetric and VSM analyses indicated high thermal stability and superparamagnetic behavior of the hybrid nanobiomaterial. The X-ray photoelectron spectroscopy studies revealed formation of pure metallic nanoparticles on the surface of the hybrid nanobiomaterial. The as-synthesized hybrid nanobiomaterial were tested for several model reactions such as photocatalytic reduction of dye, hydrogenation of p-nitrophenol, and Suzuki coupling reaction at ambient temperature and in aqueous solution. The catalytic efficiencies varied with the type of MNPs, and Fe3O4@Ch-PdNPs exhibited superior catalytic activities in all chemical reactions. In addition the hybrid nanobiomaterial demonstrated excellent recyclability and reusability without significant loss of catalytic activities. Furthermore, the leaching of metal ions was not detected during catalytic reaction confirming high stability and low environmental impact of the as-synthesized hybrid nanobiomaterial. We believe that our result will help to synthesize easily separable hybrid nanobiomaterial as a heterogeneous catalyst through a cost-effective and eco-benign synthetic route for the development of environmental sustainable nanotechnology.