Combining Submicron Spectroscopy Techniques (AFM-IR and O-PTIR) To Detect and Quantify Microplastics and Nanoplastics...

Atomic force microscopy-based infrared spectroscopy (AFM-IR) and optical photothermal infrared (O-PTIR) spectroscopy are cutting-edge techniques used for precise nanoscale chemical analysis, capable of detecting and characterizing particles smaller than 1 μm. In this study, we applied both techniques to analyze snow subsamples collected from Beaver Mountain, Utah. Quantification by AFM-IR identified a concentration of 1.50 × 10^-1 μg/mL of poly(3-hydroxybutyrate-co-4-hydroxybutyrate), a copolyester known for its biodegradability and biocompatibility and that was the only polymer detected. Notably, 96% of particles had thicknesses below 1 μm, with the smallest particle recorded at 14 nm in height, demonstrating the advantage of the paired AFM-IR and O-PTIR techniques to detect and identify the chemical composition of a single nanoparticle. By integrating AFM-IR and O-PTIR, we combined the spatial resolution of AFM with the chemical specificity of O-PTIR, overcoming the limitations of each technique. This dual approach enabled high-sensitivity detection of nanoplastics in complex environmental samples with no preprocessing required. This approach provides valuable insights into the dimensions and concentrations of nanoplastics in environmental samples, with broader implications for understanding their prevalence and impact.