Surface plasmon mediated optical properties of ZnO/Au/TiO2 nanoheterostructure rod arrays

We report the effect of surface plasmon modes of Au-NPs embedded in ZnO/Au/TiO2 nanoheterostructures on its optical properties. Au NPs of various sizes were coated on ZnO nanrods and then covered by a thin film of TiO2. The ZnO and TiO2 were synthesized in wurtzite and anatase phases, respectively. SEM and TEM images showed that ZnO nanorods were aligned; Au had spherical morphology covered by TiO2. The observed SPR mode was red shifted from 600 nm (2.06 eV) to 633 nm (1.96 eV). The PL spectra showed two bands, UV (3.1 eV) and red (1.8-2.0 eV) bands, which decreased in intensity with the increase in the strength of SPR mode. The ratio of UV to red band integrated intensities followed the SPR intensity attributed to transfer of hot carriers from Au-NPs to TiO2 layer. The present study confirmed the tuning of optical properties through plasmon resonances in nanoheterostructures.