Fig. 4
a Raman spectra of 10-4 M 4-MBT on a SERS substrate with NDs prepared under the optimized conditions. b 10 Raman spectra of 10-4 M 4-MBT collected on a SERS substrate by randomly moving the substrate on the stage of the Raman instrument. c Raman spectra of 5 × 10-7 M R6G on a prepared SERS substrate. d Raman spectra of R6G with concentrations of 5 × 10-12, 5 × 10-11, 5 × 10-10, 5 × 10-9, 5 × 10-8, and 5 × 10-7 M on SERS substrates. The reference substrate was prepared by depositing 77 nm Ag on a bare ITO (25 nm) film.