Time-gated Raman spectroscopy for characterizing recovered plastics

Raman spectroscopy is a powerful non-destructive tool for the identifying and characterizing polymers, but a major limitation of Raman spectroscopy using continuous wave excitation is that environmental weathering, dyes, and additives in the material can generate a strong fluorescence background that overwhelms the Raman signal. Here, we employ time-gated Raman spectroscopy to successfully reduce the fluorescence signal and measure Raman spectra of recovered plastics. Time-gating removes a significant amount of background signal from the Raman spectra such that the polymers and color additives can be identified using similar measurement times compared to continuous-wave Raman spectroscopy. Examples of this are shown for a small subset of samples recovered from Hawaiian marine environments and e-waste materials. Time-gated Raman spectroscopy can also be used to characterize samples that are black in color due to carbon-based additives that are challenging or impossible to characterize using conventional techniques.