Single-Particle Mid-Infrared Photothermal Imaging Reveals Hidden Heterogeneity in Real-World Micro- and Nanoplastics

Area of Science:

• Environmental Science
• Materials Science
• Analytical Chemistry

Background:

• Microplastics and nanoplastics are prevalent in human tissues, but characterization methods are limited.
• Bottled water is a significant route for nanoplastic ingestion, making it a key matrix for study.
• Existing methods struggle to capture the full physicochemical diversity of environmental plastic particles.

Purpose of the Study:

• To develop and apply quantitative methods for characterizing micro- and nanoplastic heterogeneity.
• To investigate the chemical and morphological diversity of nanoplastics in bottled water.
• To link particle properties to potential functional consequences and exposure risks.

Main Methods:

• Utilized mid-infrared photothermal (MIP) microscopy for single-particle chemical and morphological analysis.
• Performed multidimensional spectral analysis on polyethylene terephthalate (PET) particles.
• Conducted population-level spectral measurements and morphological profiling.

Main Results:

• Revealed substantial microstructural and particle-scale heterogeneity in nanoplastics from bottled water.
• Observed distinct physicochemical features in PET particles compared to laboratory standards, with enhanced intra-particle uniformity.
• Demonstrated continuous variations in PET crystallinity and resolved discrete size/shape distributions across polymer types.
• Showed that particles of similar size and composition can exist in divergent physicochemical states.

Conclusions:

• Single-particle characterization using MIP microscopy provides essential property-resolved insights into nanoplastic contamination.
• Understanding particle heterogeneity is vital for accurate human exposure assessment.
• These findings can guide predictive models, mitigation strategies, and regulatory standards for micro- and nanoplastic monitoring.