| Doping is a powerful and effective way to alter the electronic, magnetic, and optical properties of a semiconductor, however the precise control of the dopant concentration in semiconductor nanocrystals is a major challenge. Previously, our group demonstrated full control of surface loading of first row transition metals on TiO2 nanostructure. Herein is described a method to 'push' the surface metals into the TiO2 framework. The diffusion of metal ions from the surface to the interior of the nanocrystal is limited by two factors, the solubility limit of the dopant in the host lattice and the concentration of metal ions on the nanocrystal surface. Below the solubility limit of dopant ion in the semiconductor, the redistribution of metal ions into the nanocrystal (versus desorption into solution) proceeds at a linear ratio of ~30% with our current method. Post-synthetic treatments ensure full removal of surface adsorbed metal ions. The doping method proceeds with no change in morphology of the nanocrystal. Cobalt-doped TiO2 nanorods with low dopant concentrations are both UV and visible light active for dye degradation. Photocatalytic water splitting study with synthesized cobalt-doped TiO2 nanocrystals shows consistency with theoretical calculation. The synthesized samples were also used to prepare thin films for conductivity measurement for diverse applications. |
