Fig. 7
SERS intensity response to the variation of pH. a Experimental calibration curve of ratio R = IA+B/IC as a function of pH (error bars show the standard deviation from the mean of n = 8 measurements). Source data are provided as a Source Data file. In b and c are reported two typical spectra collected from AuNP in solutions at pH 6.0 and 7.4. Positions of the intensities related to bands A, B, and E are indicated by arrows and labels. The deconvoluted band C was used to normalize the A + B intensity. In acidic environments, the intensity of COO− symmetric stretching (A + B) decreases, reflecting the reduction of deprotonated carboxylic acid concentration. In alkaline solutions, the intensity of this vibration mode increases, especially sub-band B. Compared to band A + B, band E due to C = O stretching vibration in COOH is less intense and it has an opposite trend of intensity as a function of pH. Source data
