The calculated position of the surface plasmon peak as displayed in Figure 5 (circles) is in perfect agreement with the
experimental data (triangles in Figure 5) for particle sizes from 25 to 120 nm. For sizes smaller than 25 nm the experimentally observed peak position is somewhat lower than predicted by theory. This may be attributed to the pronounced increase of the ratio of surface atoms to bulk atoms for particle diameters smaller
than 20 nm. However, for sizes larger than 25 nm both the theoretical and the experimental peak positions (λspr) are both
fitted precisely by a simple exponential function (R2 ) 0.99, see the dotted and the dashed lines in Figure 5):