Absorption and photoluminescence spectra were characterized for verifying the formation of same nanoclusters as reported (Figure ). The molar concentration was estimated by the concentration of protein before synthesis reaction, based on an assumption that all added protein participated the formation of nanoclusters (concentration of BSA-AuNCs mother solution is 376 μM, concentration of BSA-AgNCs is 351 μM, and concentration of Lysoyme-AuNCs is 150 μM). For UV-vis absorption spectra, the samples were diluted with water to a final concentration of 10 µM and then were measured on an Avantes AvaSpec-2048 spectrophotometer with an AvaLight DH-S deuterium lamp with water as reference. Fluorescence emission and excitation spectra were recorded with a Horiba FluoroMax-4 spectrophotometer at excitation and emission slits of 5 nm bandpass. The samples were diluted with water to a final concentration of 20 µM.