Next, we collected confocal images from these samples (Fig. 4, top panels).
The fluorescence intensities on SIF and SACS substrates are much stronger than on the glass. Also, the fluorescence on SACS is localized in “hot spots” where the enhancement is higher. Figures 5 and 6 show the intensity and lifetime traces across the images as indicated by the lines in Fig. 4, top panels. As expected, the distributions of intensities and lifetimes on glass and SIFs substrates are relatively homogeneous. In contrast, on the SACS substrate, both intensity and lifetime traces are heterogeneous. Also, as expected, the stronger brightness corresponds to the shorter lifetime, see arrows on Fig. 6. This indicates that RDE effect plays an important role in the total enhancement. The lifetime images and distributions from entire 30 ×?30 μm2 areas are shown in Fig. 7. This figure visualizes changes in the lifetime induced by metallic nanoparticles. More precise lifetime measurements are shown on Fig. 8. The amplitude averaged lifetimes are significantly shorter on metallic surfaces than on the glass.
