FIGURE 4.

SAF intensity as a function of dipole distance z from the metal/water (metal) or glass/water interface (glass). Constants are identical to those in Fig. 3 and collection is from the glass medium over a surface area that covers the solid cone of fluorescence emitted from the dipole and transmitting the interface with polar angle 105° ≤ θ_em ≤ 116° measured from the z axis in Fig. 2. SAF z-profiles are indicated for dipole components parallel (μ_‖) or perpendicular (μ_⊥) to the interface. Also depicted for comparison is the exponential function e^−z/100. SAF intensity for μ_‖ at the metal film has a peak height ∼20-fold smaller than the other intensities as indicated in the legend. All emission intensities fall off rapidly in z, implying SAF selectively detects probes near the interface.