Abstract
Ag-N-codoped zinc oxide nanoparticles were synthesized by a one-step impregnation of Ag in N-doped ZnO nanoparticles. The morphologies and structures of the as-synthesized nanomaterials were investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-Vis spectrophotometric techniques. Photocatalytic degradation of methyl red dye using synthesized photocatalysts was studied under solar as well as UV irradiations. Modified zinc oxide photocatalysts showed higher photocatalytic activity compared to pure zinc oxide both under solar as well as UV irradiations. Calcined zinc oxide shows better photocatalytic activity than commercial zinc oxide under both solar and UV irradiations. Highest catalytic activity of Ag-N co-doped zinc oxide (ANZ) among the undoped, Ag-doped and N-doped photocatalysts was attributed to the lower rate of recombination of the photogenerated electrons and holes as well as its lower band gap energy. Photocatalytic degradation of methyl red dye follows pseudo first order kinetics for all the nanoparticles so-obtained. KEY WORDS: Nanoparticles, Photocatalysis, Zinc oxide, Impregnation, Methyl red Bull. Chem. Soc. Ethiop. 2013, 27(2), 221-232DOI: http://dx.doi.org/10.4314/bcse.v27i2.7
Highlights
The uncontrolled release of colored waste water contaminated with dyes from textile, paper, rubber and plastic industries have led to serious environmental contamination [1]
When semiconductors are illuminated with an appropriate radiation source, electron/hole pairs are produced with electrons promoted to the conduction band leaving behind positive holes in the valence band
The generated electron/hole pairs induce a complex series of reactions that can result in the complete degradation of organic pollutants such as dye adsorbed on the semiconductor surface [5]
Summary
The uncontrolled release of colored waste water contaminated with dyes from textile, paper, rubber and plastic industries have led to serious environmental contamination [1]. Doping of such transition metals will reduce the electron-hole recombination Another limitation of ZnO is its wide band gap energy (= 3.2 eV) which limits light absorption only in the UV region. The doped nonmetal in ZnO may cause its band gap narrowing shifting the photoabsorption edge of zinc oxide to visible region. Many methods such as template method [10], chemical-precipitation [11], thermal oxidation process [12], hydrothermal synthesis [13], sol-gel method [14], microwave radiation [15], and laser-induction [6] have been used to successfully synthesize the Ag doped ZnO nanocrystals. Where A0 is absorbance of dye at initial stage, At is absorbance of dye at time “t”
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