Fig. 5: Digital mapping and quantification of dye modified PS beads using SERS.

a Schematic of the digital counting process using SERS intensity maps. Membrane scanning generates intensity maps where thresholds are assigned to distinguish positive (“1”) from negative (“0”) Raman signals. Data transformation converts the intensity map into a binary matrix for digital counting. Linear regression is then applied to correlate Raman counts with concentrations, allowing for the differentiation between high and low concentrations of analytes. b SERS intensity maps of methyl red-PS beads at various concentrations, ranging from blank to 10⁻⁸ M. The number of positive counts (yellow) increases with higher concentrations, illustrating the sensitivity of the detection method. c Calibration curves for different molecule-modified PS beads: Methyl red-PS, Rhodamine 6G-PS, Fluorescein-PS, L-arginine-PS, and L-ascorbic acid-PS. Each plot shows the correlation between Raman counts and bead concentrations. An inset graph plotted using a logarithmic scale to cover the entire concentration range. Data represent mean ± s.d.; n = 3 digital counting batches