Semiconductor Nanocrystals as Antennae for Luminescent Lanthanide Cations

As biological assays involving fluorophores become more prevalent, due to their high sensitivity, moderate cost and versatility for applications, there is an increasing demand for luminescent reporters with advanced properties for use in bioanalytical applications and biological imaging. The most important properties include the strong resistance to photobleaching and the ability to be discriminated from background fluorescence (biological autofluorescence). We have initiated an innovative strategy to create luminescent reporters possessing the photophysical properties that fulfill these requirements by combining the advantages of semiconductor nanocrystals (tunable emission bands, large epsilon values, and high photostabililty) with those of lanthanide cations (sharp emission bands, long luminescence lifetimes, and resistance to photobleaching). This work is aimed at creating novel antenna for the sensitization of luminescent lanthanide cations emitting in the visible and in the near-infrared. The crystals structure of semiconductor nanocrystals is also used to protect the lanthanides from nonradiative deactivations inducing the increase of the quantum yields. In additions, this synthetic strategy will allow the formation of polymetallic luminescence species, where the high density of lanthanide cations per units of volume will induce an increased number of emitted photons, a desirable condition to increase luminescence detection sensitivity. Photophysical and structural characterization of various lanthanide containing nanocrystal materials have been studied, including CdSe:Ln, ZnS;Ln, ZnSe:Ln and LnS. The coating of the surface of the nanocrystals in order to control their properties is also discussed in this work