Green synthesis of polymer stabilized polyhedral Au, Au-Ag and Au-Cu nanoparticles and their catalytic activity for the reduction of 2-nitrophenol

The green synthesis of metallic nanoparticles is essential to a broad range of environmental applications. In this work, one-step green synthesis of colloidal Au, Au-Ag and Au-Cu nanoparticles with polyhedral shape and their use as catalysts for the reduction of 2-nitrophenol are reported. In our method, poly(p-acryloylaminophenylarsonic acid) (poly(p-AAPHA) was used as reducing and stabilizing agent for the synthesis of metal nanoparticles in aqueous solutions at room temperature and without using hazardous chemicals. Polyhedral nanoparticles were characterized by ultraviolet-visible (UV-Vis) spectroscopy and transmission electron microscopy (TEM). UV-Vis results revealed that the reduction process of metallic ions by poly(p-AAPHA) occurs slowly, and the formation of nanoparticles take place after several days. The nanoparticles were stabilized in the colloidal solutions by the combination of steric and electrostatic effects provided by poly(p-AAPHA). TEM images confirmed the polyhedral shape of the Au, Au-Ag and Au-Cu nanoparticles with an average size of 18.2, 18.4 and 22 nm, respectively. Also, the Au-Ag and Au-Cu particles showed a structure homogeneous alloy type. The study of the reduction of 2-nitrophenol in aqueous solution in presence of sodium borohydride using the poly(p-AAPHA)-stabilized polyhedral nanoparticles as catalyst revealed that their catalytic activity is dependent on the composition and particle size. Polyhedral Au nanoparticles showed the highest reaction rate constant 0.188 min(-1) followed by Au-Ag (0.0729 min(-1)) and Au-Cu (0.016 min(-1)).{GRAPHICAL ABSTRACT}