Morphology controlled synthesis of Sm doped ZnO nanostructures for photodegradation studies of Acid Blue 113 under UV-A light

Abstract

In this report, photocatalytic degradation of Acid Blue 113 (AB 113) has been investigated in aqueous heterogeneous media containing pure and Sm 3? doped ZnO nanostructures. A simple low frequency (42 kHz) ultrasound was employed to synthesize the nanostructures. X-ray diffraction, UV-Vis-NIR and Photoluminescence analyses revealed that Sm 3? ion was successfully doped into ZnO lattice. The organic solvents and dopant highly influenced the particle morphology which was identified through transmission electron microscopy. The photocatalytic efficiency was highly depended on the native defects and dopant. Sm 3? doped ZnO nanostructures demonstrated better photocatalytic degradation of the AB 113 due to the involvement of more oxygen vacancy defects, oxygen interstitials and Sm 3? ions in the charge recombination process and enhanced the better catalytic reaction under a UV-A lamp.

Effect of Gd3+ doping on structural and photocatalytic properties of ZnO obtained by facile microwave-hydrothermal method

“…The introduction of Gd 3+ ions can generates an increase in the number of structural defects in the crystalline ZnO lattice, as oxygen vacancies. The oxygen vacancies act as electron acceptors during photocatalytic process, which trap the photogenerated electrons temporally to reduce the recombination of electrons and holes, providing an alternative path [43,85]. If the amount of rare earth ions exceeds the dopant acts as recombination center for electrons and holes, so the photocatalytic activity decreases, also observed in literature [48,86].…”

“…The increase for dopant promotes an increase in the number of defects in the crystalline lattice of the ZnO, thus leading to an increase in the lattice parameters. The cell parameters (Table 1) indicate that doping with rare earth ions generates distortions in the crystalline lattice of ZnO and increases the amount of structural defects, such as oxygen and interstitial oxygen vacancies [43,58,60], since a slight increase was observed in the values of the cell parameters and consequently in an expansion of the unit cell when compared with the pure sample. This effect is consistent because the ions Gd 3+ coordinate at (2) Photonic efficiency ( ) = r × 100 I octahedral positions preferentially in the crystalline lattice, occupying the interstitial sites [6].…”

“…New intermediate energy levels located between the valence band and the conduction band of ZnO are generated by the Gd 3+ doping. The photoinduced holes react with adsorbed H 2 O generating the oxygen radical species, responsible for the degradation of organic contaminants [7,32,43].…”

“…To enrich the photocatalytic, optical and magnetic properties of pure ZnO, many efforts have been made, as morphologies tuning, homogenous particles obtention and modification by doping with non-metals, alkali metals, transition metals (TM) as well as rare-earth (RE) metals [38][39][40][41][42]. Rare-earth metals doped ZnO nanostructures it's a good alternative, which produced impurity energy levels in band gap and traps for photogenerated charges carriers accelerating the interfacial charge transfer and decreasing the recombination of electron-hole pairs [43,44]. Gadolinium with half-filled f orbital has a mainly positive effect on the optical, electronic and magnetic properties when is used as a dopant for ZnO [42,45].…”