Doping is a powerful and effective way to alter the electronic 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. Our present work demonstrates a method to ‘push’ the surface metals into the TiO2 structure. 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 ~38% with our current method. Although the process appears to consume all of the adsorbed metal ions, we can perform post-synthetic treatments to ensure any surface adsorbed metal ions are fully removed. The dopant method proceeds with no change in morphology of the nanocrystal, and since we utilize the large-scale preparation of TiO2 nanocrystals reported by Hyeon the method yields multi-gram quantities of doped nanocrystals with precise control.

Quantitative control of metal doping in TiO2 nanocrystals

253rd National Meeting (2017)

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