Upconverting Nanoparticles: The Active‐Core/Active‐Shell Approach: A Strategy to Enhance the Upconversion Luminescence in Lanthanide‐Doped Nanoparticles (Adv. Funct. Mater. 18/2009)

Lanthanide-doped nanoparticles capable of (up)converting near-infrared (NIR) light to higher energies via an anti-Stokes process known as upconversion have demonstrated extraordinary potential in biological applications on the virtue that background fluorescence is near-zero. To maximize the intensity of the upconverted luminescence in lanthanide-doped nanoparticles, Vetrone et al. utilize a core/active-shell architecture where the active-shell readily absorbs NIR light and transfers it to the active luminescent core, thereby increasing the upconversion emission, as described on page 2924.