Fig. 2. Reproducibility and stability characterization of the chip-based ratiometric SERS method. (a) SERS mapping over a large area (3 × 3 mm2) obtained with the Raman intensity at 882 cm–1. (b) SERS image of the same chip acquired by scanning with the ratio of I882/I998. (c and d) Standard deviation was improved from 20.24% to 8.06%. (e) Relative intensity of the SERS chip after different storage times. (f) SERS intensity at 882 cm–1 determined from gold colloids aggregated by potassium chloride.
