Abstract
A new synergetic hybrid Ag/ZnO nanostructure was fabricated which is able to cause photocatalytic degradation (in high yields) of methylene blue under visible light as well as in the dark. In this nanostructure, ZnO was synthesized using the arc discharge method in water and was coupled with Ag via a chemical reduction method. X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy results confirmed the existence of defects in ZnO in the hybrid nanostructures; these defects act as electron traps and inhibit the recombination of electron-hole pairs. The absorption edge of the hybrid nanostructure shifts toward the visible region of the spectrum due to a combination of the Ag plasmonic effect and the defects in ZnO. Band-edge tuning causes effective visible light absorption and enhances the dye degradation efficiency of Ag/ZnO nanostructures. Silver oxidation in the hetero-structure changed the metal-semiconductor interface and suppressed the plasmonic enhancement. Nevertheless, the synthesized Ag/ZnO decomposed methylene blue in visible light, and the silver oxidation only affected the catalytic activity in the dark. This work provides insight into the design of a new and durable plasmonic-metal oxide nanocomposite with efficient dye degradation even without light illumination.
Highlights
Organic dyes from industries such as textiles, paper, leather, printing inks and cosmetics release non bio-degradable contaminants into water
It is believed that the combination of surface defects in ZnO together with the presence of Ag nanoparticles leads to the visible light photocatalytic activity of Ag/ZnO hybrid nanostructure (HNS)[19,20,21]
In this research, aged Ag/ZnO HNS refers to the sample after being applied in photocatalytic degradation process, which there is AgO phase
Summary
Organic dyes from industries such as textiles, paper, leather, printing inks and cosmetics release non bio-degradable contaminants into water. The formation of this metal-semiconductor hetero-junction is an effective way to enhance charge carrier separation and improve the photocatalytic efficiency[3,4,5] In this regard, decoration of TiO2/ZnO with noble metal nanoparticles is a promising method to reduce the recombination of the photogenerated electrons and enhance the photo-degradation activity[6,7,8,9,10]. Defects introduce states below the conduction band minimum of ZnO, and these states act as electron traps, inhibiting electron recombination and enhancing both carrier separation and photocatalytic activity[20,21] In this regard, Ag/ZnO heterostructures have been extensively used to enhance the photo-degradation of different organic dyes under UV and visible light[15,19,22,23,24,25]. These results could be useful with regard to developing a nanostructure with high dye degradation properties even in the dark
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