Surface Plasmon Enhanced Luminescence from Ag covered Anatase Titania Nanotubes

Abstract

We show that coating of titania nanotubes by Ag layers with thickness of 5 – 20 nm leads to the increase of the near-bandgap photoluminescence intensity by one order of magnitude, while the effect of Au coatings is insignificant. Titania nanotibes with average outer diameter of 250 nm and wall thickness of 70 nm with anatase structure were produced by anodization of Ti foils in an ethylene glycol based electrolyte containing a mixture of HF and H3PO4 followed by annealing at 300 oC. The enhancement of the band-edge emission is believed to be due to the effect of surface plasmons in Ag coatings. This suggestion is supported by calculations of dispersion relations of surface plasmons at the Ag/TiO2 interface and by the measurement of the transmission spectra of uncoated and metal coated titania nanotubes.