Fluorescence signals of core-shell quantum dots enhanced by single crystalline gold caps on silicon nanowires

We use nanoscale (20–300 nm in diameter) single crystalline gold (Au)-caps on silicon nanowires (NWs) grown by the vapor–liquid–solid (VLS) growth mechanism to enhance the fluorescence photoluminescence (PL) signals of highly dilute core/shell CdSeTe/ZnS quantum dots (QDs) in aqueous solution (10−5 M). For NWs without Au-caps, as they appear, for example, after Au etching in aqua regia or buffered KI/I2-solution, essentially no fluorescence signal of the same diluted QDs could be observed. Fluorescence PL signals were measured using excitation with a laser wavelength of 633 nm. The signal enhancement by single crystalline, nanoscale Au-caps is discussed and interpreted based on finite element modeling (FEM).