Fig. 3.

Average SERS spectra (a), PCA scores (b), and loadings (c) of three L. monocytogenes control strains (02/07, 2082/03, 475/05), all sensitive to BC and Cd²⁺, from three different genoserogroups, filtered from saline solution and recorded on Ag:Au SERS platforms. For all spectra the excitation wavelength was at 785 nm, laser power at 0.5 mW, and acquisition time 45 s. Each SERS spectrum was averaged from at least 25 measurements at different points of the SERS platform