Fig. 4

Optimization of antibody concentration for conjugation. (a) Color changes of the AuNPs with different antibody concentrations (0.4, 0.6, 0.8, 1, 2, 4, 6, 8 μg/mL) in the presence of NaClchanges were observed by the naked eye to determination optimal pH). (b) UV–Vis spectra of AuNPs with various antibody concentrations in presence of NaCl