Facile synthesis of ZnO and transition metal doped ZnO nanoparticles for the photocatalytic degradation of Methyl Orange

ZnO and transition metal doped ZnO nanoparticles (Zn0.99M0.01O; Mdouble bond; length as m-dashMn, Co, Ni and Cu) have been successfully synthesized by thermally decomposing their oxalate precursor. The synthesized nanoparticles have been characterized using XRD, FT-IR and WD-XRF. The samples were found to possess hexagonal wurtzite phase of ZnO suggesting efficient doping of transition metal ions into ZnO lattice. The particle size of ZnO was found to be in the range 25–30 nm from Transmission electron microscopy technique. The photocatalytic behavior of synthesized nanoparticles has been scrutinized using Methyl Orange (MO) as probe molecule. Undoped ZnO was found to be better photocatalyst than doped ZnO. Also, the degradation of dye followed first order kinetics. The generation of hydroxyl radicals on the surface of UV-irradiated ZnO has been detected by the Terephthalic acid Photoluminescence probing technique. Furthermore, 11 intermediates have been identified during the photodegradation process using LC-MS technique. Based on the identified intermediates, a pathway has been proposed for the degradation of MO over ZnO. The reusability of ZnO catalyst has also been studied and its photocatalytic efficiency was found to be unaltered ever after 5 cycles of use.