Fig. 4. Reproducibility of the SERS signals on AgNPs@CA films. (A) SERS spectra of 1 × 10−6p-ATP recorded from 20 different positions on both side of the AgNPs@CA composite film, respectively. (B) The SERS intensity distribution of the 1388 cm−1 bands. (C) SERS spectra of p-ATP (1 × 10−6 M) recorded from 10 different AgNPs@CA composite films. (D) The corresponding SERS intensity distribution of the 1388 cm−1 bands. The average intensity value is indicated by the red line; intensity variations of ±8% and ±8–15% are indicated by the cross grain and light green zones, respectively.
