Figure 3.

Differentiation of Gal1 and Gal 3 by the comparison of their SERS spectra and PLS-DA analysis. (A) Overlap of normalized Savitzky–Golay SERS spectra of Gal1 (red) and Gal3 (blue) at 5 μg mL⁻¹. (B–D) Cross-validated PLS-DA Y-prediction plots for Gal1 and Gal3 samples based on SERS spectra for each spectral class. The green asterisks and blue plus signs represent sample spectra of Gal1 and Gal3, respectively, at 100 μg mL⁻¹ (B); 5 μg mL⁻¹ (C); and 1 μg mL⁻¹ (D). SERS signal assignments for Gal1 and Gal3 and the PLS-DA cross-validated results are shown in Tables S5 and S6 in the Supporting Information, respectively.