Polar plot for (A) fluorescence enhancement factor, i.e., the ratio of emission intensity of FITC-HSA at 517 nm on silver films and the emission intensity of FITC-HSA on glass slides, typical angular-dependent fluorescence spectrum of FITC-HSA on SiFs (bottom), (B) Photostability of FITC-HSA from SiFs. Emission intensity (p-polarized) was measured at 517 nm and collected at 225° and 340°, Excitation: 473 nm, at 90°.