Figure 3.

Plot of emission intensity vs wavelength for potential encoding fluorophores shows that lanthanide emission peaks (purple line) are much narrower than emission peaks from organic dyes or quantum dots. These narrow lanthanide emission peaks, which display less spectral overlap than any other fluorophore, allow their relative emission intensities to be measured more accurately thereby giving rise to more resolvable and numerous optical codes. Unlike the organic dyes and quantum dots, which are susceptible to code-altering photo-oxidation, the lanthanide material cannot be photochemically altered. The inset shows that nucleic acids and proteins are not excited at the lanthanide excitation wavelength used and any autofluorescence is eliminated. The 315 nm excitation also does not overlap with the absorption of the visible-light-excited, colored reporter dyes and, conversely, the colorless lanthanide materials are not excited by visible light eliminating any optical crosstalk between encoding and reporter fluorophores.