Fig. 4

Bi-analyte single-molecule detection base on MPCA. a 2D Raman mapping of the peak intensity at a 613 cm⁻¹ corresponding to R6G. The scale bar represents 5 µm. b 2D Raman mapping of the peak intensity at a 414 cm⁻¹ corresponding to CV. The scale bar represents 5 µm. c Typical spectra for bi-analyte analysis. The details of all the spectra can be found in the Supplementary Note 10. d Histogram of occurrences of pure R6G, pure CV and mixed events. e Coefficient (α,β) plot of the spectra based on the eigenvectors from MPCA. The axes represent two principle eigenvectors that corresponds to the R6G (red) and CV (green) events. The points in between and near the origin corresponds to the mixed events (blue) and null events (black) respectively. f Single-molecule probability histogram derived from MPCA, providing a clear sign for sensitivity at single-molecule level