Micro- and nano-plastics (MNPs) are an emerging contaminant classification formed by the direct release from or breakdown of polymer consumer products. A key challenge for MNPs is being able to characterize their chemical properties and quantify them in complex environmental samples. Currently, spectroscopy techniques like Fourier transform infrared (FTIR) spectroscopy can provide chemical specificity and size characterization, but it has an inherent size limitation of approximately 5 mm. Another analytical limitation is the ability to measure the degradation of MNPs under environmentally relevant conditions. Here, we introduce a new, super-resolution infrared absorption technique for characterizing MNPs, called infrared photothermal heterodyne imaging (IR-PHI). IR-PHI can determine the chemical identity, morphology, and quantity of MNPs in a single analysis with a spatial resolution of approximately 300 nm. It can also be set up to measure the degradation behavior of MNPs in-situ and in real-time. In this study, we demonstrate the use of IR-PHI to characterize MNPs that have undergone either thermal or ultraviolet degradation. MNP examples include nylon teabags, dryer lint, vacuum dust, road dust, and PMMA and polystyrene microspheres.

Characterizing the degradation of micro- and nano-plastics in the environment using infrared photothermal heterodyne imaging and spectroscopy (IR-PHI)

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ACS Fall 2022

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