Fabrication and study on the structural and photocatalytic characterization of Ag doped ZnO nanostructure materials

Abstract

ZnO and 10% Ag doped ZnO (10%Ag-ZnO) nanopowders have been researched and fabricated with using extracts from red peony leaves. These materials have been preparated by route of a simple wet chemical method and calcined at a low temperature of about 400oC for 2 hours. Ag+ ions was doped into the ZnO material compared to Zn2+ ions at a molar ratio of 1: 10. Methods to study the characteristics of nanopowders have been used such as XRD, SEM/EDX and reflection spectroscopy. The Kubelka–Munk method based on the reflectance spectrum of the sample was exploited to determine the optical gap energy (Eg) of ZnO and 10% Ag doped ZnO nanopowder samples. The results show that the Ag doped ZnO nanopowder has a smaller average crystal size than undoped ZnO (these value are 22.6 and 32.27 nm, respectively). With doping into transition metal oxide semiconductor material by ions with a radius much larger than the radius of the host ions of the transition metal oxide crystal lattice (the radius of the Ag+ ion (1.22 Å) is higher than the radius of the Zn2+ ion (0.74 Å)), it is likely that the Ag element will be doped into the ZnO crystal lattice in an interstitial form. The Eg value of 10%Ag-ZnO nanopowder is also reduced compared to undoped ZnO, reaching a value of Eg 3.16 eV (the ZnO sample reaches a value of Eg 3.28 eV). The Ag doped ZnO sample has improved the material's optical application range, achieving high photocatalytic efficiency (97.8%) for decomposing methylene blue (MB) dye solution under 40 minutes of visible light irradiation. The 10%Ag-ZnO nanopowder is prepared from using red peony leaf extract -this is one of the "green" manufacturing methods. This prepared material has achieved outstanding advantages compared to undoped ZnO material such as reducing the average crystal size, reducing the optical band gap energy, and achieving photocatalytic decomposition reaction for MB dye solution under visible light with high efficiency.