The quenching of the trapped emission is expected via the new non

The quenching of the trapped emission is expected via the new nonradiative pathways created by the proximity of the metal, possibly resulting from electron transfer from ZnO to Ag [37]. Figure 5 PL emission spectra (λ ex = 325 nm) of the Ag/ZnO heterostructures

(a) and blank ZnO nestlike structures (b). In order to further detect the interface buy PCI-32765 between ZnO and Ag, surface-enhanced Raman scattering (SERS) spectrum was measured for Ag-ZnO nestlike heterostructures with blank nestlike ZnO as comparison (Figure  6). As is evident find more from the curve b, blank nestlike ZnO has weaker Raman signal. However, for the Ag-ZnO nestlike heterostructures (curve a), a strong Raman scattering line is observed at 578, 1,153, and 1,726 cm−1 which is assigned to the ZnO 1LO, 2LO, and 3LO modes [38]. The 1LO photo mode of the Ag-ZnO nestlike heterostructures shows threefold enhancement

compared to that of blank nestlike ZnO. In addition the 4LO (2,318 cm−1), 5LO (2,932 cm−1), and 6LO (3,506 cm−1) [39] can be observed distinctly when Ag nanoparticles were deposited in the center of ZnO nests. In the range of larger wavelength, the baseline of the Raman intensity has declined. This phenomenon might be associated with the quenching fluorescence of ZnO in the Ag-ZnO nestlike heterostructures. Theoretical and experimental studies on BMS-907351 molecular weight SERS mechanisms have revealed that the SERS signals are primarily attributed to the electromagnetic excitation of strongly localized surface plasmon

of noble metals [40]. In the Ag-ZnO nestlike heterostructures, we also count the localized electromagnetic effect of the Ag surface plasmon as mostly responsible for the enhancement of multiphonon Raman scattering. In addition, based on the fact that surface plasmon energy of metal Ag matches well with the emitted visible photon energy from the ZnO, the surface plasmon of the Ag nanoparticles might be resonantly Nintedanib (BIBF 1120) excited through energy transfer in the near field and create a stronger local electromagnetic field [41]. The incident light field coupling to the local surface plasmon field might induce stronger localized electromagnetic field in the interface between ZnO and Ag, which further enhances the multiphonon Raman scattering of ZnO, demonstrating the formation of Ag-ZnO heterostructures. Figure 6 Enhanced Raman scattering of Ag-ZnO nestlike heterostructures. (a) relative to blank ZnO nestlike structures (b) using a He-Ne laser (λ = 325 nm). Conclusions In summary, a convenient approach based on sodium citrate as capping reagent has been developed for the shape-selective synthesis of ZnO with controllable morphologies at room temperature by electrochemical deposition.

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