Fig. 3. (a) The absorbance ratio of 640/520 (nm/nm) for different concentrations of 26.5 nm AuNPs over the wide concentration range of Cys. The photographs of the AuNPs corresponding to different concentrations of Cys: 0 μM, 0.1 μM, 0.2 μM, 0.4 μM, 1 μM, 10 μM, 100 μM, 200 μM, 500 μM, 1000 μM, 10 000 μM, 20 000 μM, (b) 1010 particles per mL of AuNPs, (c) 1011 particles per mL of AuNPs, (d) 3 × 1011 particles per mL of AuNPs.
