Enhanced Dye Fluorescence in Novel Dye-ZnO Nanocomposites

New fluorescein isothiocyanate/fluorescein/rhodamine B-doped ZnO composite nanostructures including tripods, tubes, and rods with tuned sizes have been designed and synthesized to greatly enhance the dye fluorescence up to ∼90 fold. The great fluorescence enhancement mainly arises from the interaction between Zn²⁺ ions in the ZnO matrix and the dye carbonyl group. The refraction index difference between ZnO and the dyes used here and the segregation of the dye molecules by the ZnO matrix only slightly contribute to the fluorescence enhancement. The control pure ZnO sample has no emission in the dye fluorescence range (500-650 nm) and excludes the possible contribution of the ZnO emission and the relevant energy transfer between the dye and ZnO to the fluorescence enhancement. These composites with the new fluorescence enhancement mechanism not only facilitate dye applications such as medical diagnostics and biotechnology, but also supply a novel and general approach to improve the fluorescence of organic dyes with carbonyl group by doping them into metal oxides. New dye-ZnO composite nanotripods, nanotubes, and nanorods with greatly enhanced dye fluorescence (see figure) have been designed and synthesized, by exploiting the interaction of Zn²⁺-dye carbonyl group. This development not only facilitates dye applications in medical diagnostics and bio-nanotechnology, but also supplies a novel and general approach to improve the fluorescence of organic dyes by doping them into metal oxides.