In-situ Synthesis of Palladium Nanoparticles Immobilized on Ethylenediamine Functionalized Polypropylene Fabric via Gamma Irradiation

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Introduction

From an industrial applications perspective, the use of palladium nanoparticles (PdNPs) as a catalyst is still challenging. Owing to its nano size, its separation in the reaction mixture remains problematic making them incorporated in the product, which can pose potential problem in its quality. Immobilizing nanoparticles in solid matrices such as metal oxides, graphenes, carbon nanotubes, polymers, and zeolites [1-4] have been developed as a novel technique to address these problems to ensure practical reusability and to facilitate easy separation from the reaction mixture. In the present study, radiationinduced grafting and reduction techniques were used to synthesize the Pd nanoparticles (PdNPs) on a ligand functionalized fabric matrix and the effects of synthesis parameters were studied.

Materials and Methods

The ethylenediamine-functionalized polypropylene non-woven fabric (PP-NWF) was synthesized using electron beam grafting technique and used as a support for the growth of PdNPs. The in-situ reduction and the immobilization of Pd⁺² was achieved via radiolytic route using a ⁶⁰Co gamma source. Different concentrations of Pd⁺² in H₂O -isopropanol solvent (2.0, 4.0, and 6.0 mM) were prepared and the solution was irradiated at different absorbed doses (25, 50 and 75 kGy) but at a constant dose rate of 2.7 kGy/hr.

Results and Discussion

The resulting Pd⁰ was simultaneously immobilized and stabilized through the diamino ligands present on the fabric support as confirmed by XPS and FTIR. Curve fitting of the XPS spectra obtained three characteristic Pd components identified as the surface Pd⁰, bulk Pd⁰, and Pd⁺². The Pd nanoparticle (PdNP) yield was found to increase with the absorbed dose and the precursor concentration. PdNPs with average diameter sizes of 18±5.4 nm, 28±11 nm, and 74±38 nm using 2.0 mM, 4.0 mM, and 6.0 mM initial metal ion concentrations, respectively, were observed using FE-SEM. Large PdNP clusters and broad size distribution of the synthesized PdNPs was noted at high absorbed dose. TGA analysis showed that the synthesized PdEDA-f-PP-g-PGMA has good thermal stability. The synthesized catalyst showed to be efficient in the hydrogenation of 4-nitrophenol.

Conclusions

The size and the amount of nanometal can be conveniently controlled by varying the reaction parameters such as, absorbed dose and initial metal concentrations. The use of ionizing radiation in the in-situ reduction and immobilization of PdNPs in a grafted PP fabric is a promising technique that offers environmentally benign and economical process for the synthesis of a supported nanoparticles for potential catalytic applications.