The synchronous fluorescence spectra of BSA–drug systems without and with Au NPs at different Δ<i>λ</i> values (15 and 60 nm).

<p>(A) BSA-SAB system, (B) BSA-RA system, (C) BSA-SAB-Au4 system, (D) BSA-RA-Au4 system, (E) BSA-SAB-Au3 system, (F) BSA-RA-Au3 system, (G) BSA-SAB-Au2 system and (H) BSA-RA-Au2 system. The concentration of BSA was fixed at 5.0 × 10^-6 mol L^-1 and the concentrations of SAB/RA (1–9) were 0, 2.5, 5.0, 7.5, 10.0, 12.5, 15.0, 20.0 and 25.0 × 10^-6 mol L^-1, respectively. The concentration of Au NPs was 10.0 × 10^-11 mol L^-1.