are reported by F. C. J. M. van Veggel and co-workers. The emission and excitation spectra have been examined and the luminescence lifetimes of these materials have been determined. High quantum yields and lifetimes in the millisecond region were found. It is furthermore demonstrated that these nanoparticles can easily be incorporated in polymer materials, thus making them of particular interest as the active material in polymer-based telecommunication components, polymer-based lasers, polymer displays, and polymer light-emitting diodes. (F. C. J. M. van Veggel et al., August 16, Adv. Mater. 2002, 14, 1147-1150)