Method Based on Continuous Artificial Dry and Humid UV Treatments to Reduce the Luminescence Background in the Raman Spectra of Plastics

ABSTRACT The applicability of short continuous artificial UV treatments has been studied to reduce the luminescence background in Raman spectra of plastics. Our method applies to two groups of polyethylene plastics, in which luminescence arises either from pigments or from surface contaminations such as biofilm or from a combination of both. Increasing the duration of continuous UV exposure resulted in decreased luminescence due to photobleaching. The evolution of surface morphology and chemical composition was monitored using optical spectromicroscopy. With progressive photobleaching, the signal‐to‐noise ratio of first‐order Raman signatures improved, facilitating spectral analysis. In particular, we achieved a correlation rate exceeding 90% in the identification of polymers and their additives after treatment, which is mainly limited by the availability of reference databases. While the procedure allows for the rapid and non‐destructive identification of polymeric species, it induces only minor chemical modifications at the surface, including the oxidation of functional groups.