Metal-doped TiO2 colloidal nanocrystals with broadly tunable plasmon resonance absorption

We report here the discovery of metal-doped colloidal TiO2 nanocrystals (NCs) with broadly tunable plasmon resonance absorption; and their synthesis by a facile and scalable one-pot method. A strong localized surface plasmon resonance (LSPR) absorption peak occurs in the as-synthesized Mo, W, and Nb-doped TiO2 NCs in the visible, near-infrared (NIR) and mid-infrared regions respectively. Density functional theory calculations indicate a dopant perturbation of the TiO2 electronic structure and the resultant increase in the electron density at the Fermi level as the likely cause for the strong LSPR absorption. The W-doped TiO2 NCs are the most versatile since their LSPR absorption in the NIR region can be varied from 980 to 1700 nm by tailoring the dopant concentration and the NC morphology. The method of synthesis can also be scaled up to gram-level production in batch reactors. Tunable LSPR properties and the ease and scalability of synthesis are the strong features of these metal-doped TiO2 NCs for plasmonic applications.