An effective surface-enhanced Raman scattering (SERS) template based on a 3D hybrid Ag nanocluster (NC)-decorated ZnO nanowire array was fabricated through a simple process of depositing Ag NCs on ZnO nanowire arrays. The effects of particle size and excitation energy on the Raman scattering in these hybrid systems have been investigated using rhodamine 6G as a standard analyte. The results indicate that the hybrid nanosystem with 150 nm Ag NCs produces a larger SERS enhancement factor of 3.2 x 10(8), which is much higher than that of 10 nm Ag NCs (6.0 x 10(6)) under 532 nm excitation energy. The hybrid nanowire arrays were further applied to obtain SERS spectra of the two-photon absorption (TPA) chromophore T7. Finite-difference time-domain simulations reveal the presence of an enhanced field associated with inter-wire plasmon coupling of the 150 nm Ag NCs on adjacent ZnO nanowires; such a field was absent in the case of the 10 nm Ag NC-coated ZnO nanowire. Such hybrid nanosystems could be used as SERS substrates more effectively than assembled Ag NC film due to the enhanced light-scattering local field and the inter-wire plasmon-enhanced electromagnetic field.
"When the Ag-ZnO nanostructures are exposed to visible light, charge carriers are formed in the noble metal by the absorption of visible light, and are directly injected from the optically excited plasmonic-metal nanostructures into the semiconductor [24,25]. This unique property, in addition to its optical and electrical characteristics , makes Ag-ZnO nanostructures a potential candidate for photocatalysis and special applications that require antibacterial properties  , surface-enhanced Raman scattering  , and gas-sensing abilities  . "
[Show abstract][Hide abstract] ABSTRACT: In this study, the synthesis of silver-zinc oxide (Ag-ZnO) nanostructures with a plant-extract-mediated hydrothermal method was investigated. The eco-friendly plant extract Azadirachta indica (Neem) was used as a reducing agent. The X-ray diffraction patterns showed the formation of face-centered cubic (fcc) Ag nanoparticles (NPs) and a wurtzite ZnO structure. An optical study of these nanostructures revealed two absorption edges: one at 393 nm corresponding to ZnO and the other at approximately 440 nm corresponding to Ag. A morphology study showed that hierarchical ZnO nanostructures were decorated with 10–50-nm-diameter Ag NPs. The formation and growth mechanism were also examined. A photoelectrochemical study was performed to investigate the electronic interactions between the ZnO and Ag NPs in the photoanode upon exposure to light. The Ag NPs act as electron acceptors, inhibiting electron–hole recombination. The photocatalytic activity of the Ag-ZnO nanostructures was examined by observing the degradation of aqueous methylene blue (MB) dye under natural sunlight. The apparent rate constant determined for the photocatalytic degradation of MB by the Ag-ZnO nano-structures was 5.9668 × 10 −2 min −1 , which was faster than that of the untreated ZnO nanostructures (2.527 × 10 −2 min −1). This plant-extract-mediated synthetic route could also be applied to the synthesis of other Ag-semiconductor oxide nanostructures.
"Representative cross-section TEM images of specimens 30_A and 30_T are shown in Fig. 3a and b, respectively. At variance with powdered ZnO (zincite), c-oriented zinc oxide systems with (001) preferential orientation were obtained, as often observed for ZnO nanostructures      . In the present case, this  growth, leading to columns perpendicular to the substrate surface, was further enhanced by the Fig. 1 e Plane-view FE-SEM micrographs of as-prepared and annealed Ag/ZnO nanocomposites. "
[Show abstract][Hide abstract] ABSTRACT: Ag/ZnO nanocomposites were developed by a plasma-assisted approach. The adopted strategy exploits the advantages of Plasma Enhanced-Chemical Vapor Deposition (PE-CVD) for the growth of columnar ZnO arrays on Si(100) and Al2O3 substrates, in synergy with the infiltration power of the Radio Frequency (RF)-sputtering technique for the subsequent dispersion of different amounts of Ag nanoparticles (NPs). The resulting composites, both as-prepared and after annealing in air, were thoroughly characterized with particular attention on their morphological organization, structure and composition. For the first time, the above systems have been used as catalysts in the production of hydrogen by photo-reforming of alcoholic solutions, yielding a stable H-2 evolution even by the sole use of simulated solar radiation. In addition, Ag/ZnO nanocomposites presented an excellent response in the gas-phase detection of H-2, opening attractive perspectives for advanced technological applications. Copyright
International Journal of Hydrogen Energy 12/2011; 36:15527. DOI:10.1016/j.ijhydene.2011.09.045 · 3.31 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ag nanoparticle/ZnO nanorods (Ag NP/ZnO NRs) nanocomposites with a core/shell structure were prepared by a seed-mediated method, which contains a polyol synthesis of Ag NPs and an overgrowth process of ZnO NRs on the surface of Ag NPs. Compared with the previously reported Ag/ZnO nanocomposites which were mostly constructed by a ZnO core and a Ag shell, the nanocomposites reported in this article showed a novel structure that contained a Ag NP core and ZnO NRs shell, resulting a hedgehog-like morphology. Electron microscope images reveal that the volume content ratio of Ag NPs colloids and the ZnO precursory solution is crucial for the morphology of the resulted samples and a well-constructed Ag NP/ZnO NRs core/shell nanocomposite can be easily obtained when their volume content ratio is set at a proper value. X-ray diffraction analysis shows a good crystalline property of both Ag NPs and ZnO NRs. The relationship between the growing temperature and the morphology of the resulted samples was investigated and a possible growing mechanism of the Ag NP/ZnO NRs nanocomposites was also proposed and discussed. Furthermore, photocatalytic activities of the resulting samples with different morphologies were also studied.
Journal of Alloys and Compounds 05/2012; 524:13–21. DOI:10.1016/j.jallcom.2012.02.052 · 3.00 Impact Factor
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