Utilization of Human Hair as a Synergistic Support for Ag, Au, Cu, Ni, and Ru Nanoparticles: Application in Catalysis

Human hair powder (HHP) after chemical treatment (e-HHP) has been successfully utilized as a unique catalyst support for immobilization of metal nanoparticles (MNPs). Ag, Au, Cu, Ni, and Ru NPs were used to prepare five different nanocatalysts (MNPs/e-HHP). High-resolution transmission electron microscopy results confirmed the excellent attachment of ultrafine MNPs on the surface of e-HHP. Actual loading of metal in MNPs/e-HHP was determined by energy-dispersive spectroscopy and X-ray photoelectron spectroscopy analyses. The zero-valent state of MNPs in MNPs/e-HHP and a very strong interaction between MNPs and e-HHP were also proven. The obtained AgNPs/e-HHP, AuNPs/e-HHP, CuNPs/e-HHP, NiNPs/e-HHP, and RuNPs/e-HHP catalysts were employed for the self-coupling of amines, N-oxidation of tertiary amines, aza-Michael reaction, imines synthesis, and oxidation of alcohols, respectively. Reaction conditions were optimized, and the scope of the catalytic systems was extended. The merit of the MNPs/e-HHP materials is shown to be the superior catalytic activity. Advantages, shortcomings, and future scope of the MNPs/e-HHP system are also highlighted.