Surface-Enhanced Vibrational Study (SEIR and SERS) of Dithiocarbamate Pesticides on Gold Films

Surface-enhanced infrared (SEIR) and surface-enhanced Raman scattering (SERS) spectroscopies are applied to the study of the adsorption on Au films of the dimethyldithiocarbamate derivative fungicides thiram and ziram. The specificity and sensitivity of both techniques in relation to the detection and surface stability of the above compounds is analyzed comparatively. We have found that both fungicides undergo a breakdown when adsorbed on Au films, although this breakdown takes place to a different extent; thiram seems to be less stable than ziram. The sensitivity of infrared techniques is higher, although a lower enhancement in relation to SERS is observed. Whereas the SEIR technique allows the detection of all the adsorbed fungicide forms, SERS displays a high sensitivity toward only certain adsorbed molecules, those that undergo a strong adsorption induced by the fungicide breakdown.