TiO2 nanotube layers with metallic nanoparticles

Abstract

The present work reports the deposition behavior of Pd or Ag particles on TiO2 nanotube layers with an average diameter of 100 nm and length of 500 nm. The deposition of Pd or Ag particles is carried out by photo-induced reduction of metal ions. TiO2 nanotube layers are exposed to UV irradiation in an electrolyte containing Pd ions. Pd deposition behavior strongly depends on the crystal structure of TiO2 nantoube layers. As-anodized nanotube layers are in the amorphous state and can be converted to anatase without any changes in structural integrity. On as-formed amorphous nanotube layer, no Pd particles are deposited whereas in the case of anatase nanotube layer many Pd particles are formed by UV irradiation in PdCl2 electrolyte. However, the size of Pd particles is larger than the diameter of nanotubes and increases with irradiation time. In order to circumvent this problem, TiO2 nanotube layer is immersed in an electrolyte, then rinsed with deionized water, followed by exposure to UV irradiation. This results in the deposition of Ag nanoparticles with the size of 10 nm on and inside nanotubes. Photocurrent measurements reveal that the presence of Ag nanoparticles on TiO2 nanotube layer enhances the absorption efficiency of dye, leading to higher photocurrent.