Hydrogen treatment-improved uniform deposition of Ag nanoparticles on ZnO nanorod arrays and their visible-light photoca
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NANO EXPRESS
Open Access
Hydrogen treatment-improved uniform deposition of Ag nanoparticles on ZnO nanorod arrays and their visible-light photocatalytic and surface-enhanced Raman scattering properties Sio-Le Lin, Kai-Chih Hsu, Chih-Hsiung Hsu and Dong-Hwang Chen*
Abstract ZnO nanorod arrays were synthesized by chemical bath deposition. After heat treatment in hydrogen or air, Ag nanoparticles were deposited on ZnO nanorod arrays by photo-reduction method. The size of Ag nanoparticles as well as the surface morphology, structure, composition, and optical property of ZnO nanorod arrays before and after the deposition of Ag nanoparticles were characterized by SEM, XRD, EDS, and UV/VIS/NIR spectrophotometer. As compared to the samples with heat treatment in air or without heat treatment, the ZnO nanorod arrays after heat treatment in hydrogen allowed Ag nanoparticles to be deposited more uniformly, densely, and numerously. Also, they exhibited higher efficiency for the visible light-driven photocatalytic degradation of Rhodamine 6G (R6G) dye. The effects of the amount of Ag nanoparticles, initial dye concentration, and temperature on the photocatalytic degradation efficiency were investigated. Furthermore, they also exhibited better surface-enhanced Raman scattering property for the detection of R6G dyes. Keywords: ZnO nanorod arrays; Hydrogen treatment; Ag nanoparticles; Photocatalytic; Surface-enhanced raman scattering
Background Nowadays, environmental problems relating to wastewaters are becoming much more serious than ever, and the photocatalytic technique with metal oxide semiconductors has become one of the most promising methods for wastewater treatment [1-6]. Among various metal oxide semiconductors, ZnO has gained pretty much attention with respect to the degradation of various pollutants owning to its high photosensitivity, high catalytic efficiency, low cost, non-toxicity, environmental sustainment stability, and wide band gap [7,8]. However, due to its wide band gap, ZnO can only be activated by ultraviolet light of wavelength below 385 nm, only accounting for less than 5% of the solar energy, which practically limits the use of solar light or visible light. Furthermore, energy saving consideration is now being more regarded. How to extend the photo response of ZnO toward the * Correspondence: [email protected] Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan, Republic of China
visible spectral region is now being an important issue [7]. To solve this tough problem, ZnO modification has been extensively explored, such as combining with other semiconductors, doping and coating with noble metals, and modifying with organic polymers [9-17]. Many researchers have reported the synthesis of Ag/ZnO composites and their applications in various fields, especially in photocatalytic degradation of organic dyes [18-34] and surface-enhanced Raman scattering (SERS) [18,35-37]. Silver metal exhibits plasmon resonances under visible light; moreover, it is stable, non-toxic
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