OICC Press Journal of Nanostructure in Chemistry 2193-8865 7 2 (June 2017) 2017 02 11 Gold nanoparticles Wells–Dawson heteropolyacid nanocomposite film as an effective nanocatalyst in photocatalytic removal of azo dyes from wastewaters 10.1007/s40097-017-0218-5 EN Neda Rohani Department of Chemistry, Arak Branch, Islamic Azad University, Arak, 38361-1-9131, IR Fatemeh F. Bamoharram Research Center for Animal Development Applied Biology - Department of Nanobiotechnology, Mashhad Branch, Islamic Azad University, Mashhad, 91865-397, IR Azam Marjani Department of Chemistry, Arak Branch, Islamic Azad University, Arak, 38361-1-9131, IR Majid M. Heravi Department of Chemistry, Alzahra University, Tehran, 1993891176, IR Journal Article 2017 02 11 Abstract A novel nanophotochromic film consisting of Au nanoparticles and Wells–Dawson-type heteropolyacid, [H 6 P 2 W 18 O 62 ], was prepared by combination of sol–gel and photoreduction method. This film was characterized by UV–visible spectroscopy, particle size distribution, Field emission scanning electron microscopy, and energy dispersive spectroscopy analysis. For the preparation of Au nanoparticles, heteropolyacid, [H 6 P 2 W 18 O 62 ] was used in form of composite film as a green reductant and stabilizer. Au nanoparticles with particle size in the range of 10–20 nm were synthesized and monodispersed in the nanocomposite using dip coating method. The photocatalytic activity of this composite film was studied in the decolorization of methyl orange (MeO) and methyl red (MR) as carcinogenic pollutant dyes using UV irradiation. The pseudo-first order rate constants was established and calculated for these reactions. Comparison of this composite film with the prepared composite by Preyssler heteropolyacid disclosed that the structure of heteropolyacid can affect loading amount of Au nanoparticles.