Fig. 4
a SERS spectra of R6G adsorbed with different pH values. b EFs of R6G on Ag@PAH NPs as a function of pH values at 1509 cm−1. c SERS spectra of R6G with different concentrations adsorbed on Ag@PAH NPs. d Relationship of peak intensities at 1509 cm−1 and concentrations of R6G (The inset is the linear relationship between the logarithmic intensities and concentrations of R6G.)