Nanoplastic fluorescence heterogeneity.

Colloidal nanoparticles are at the vanguard of commercial nanotechnology, while environmental contaminants ranging from nanoparticle products to nanoplastic byproducts are of grave concern. Quantifying the heterogeneous structures and properties of nanoparticles is fundamental both to optimizing product quality and to understanding byproduct dangers, but such measurements remain impractical. To address this issue, we develop a novel analogue of a lateral flow assay which advances and integrates complex nanofluidic replicas, super-resolution optical microscopy, and Bayesian statistical analysis. Our system enables dimensional and optical metrology of single nanoparticles with new precision, accuracy, and throughput. We apply our system to measure polystyrene nanoparticles which sorb and carry fluorophores, quantifying the particle size distribution with nanometer resolution, and revealing that fluorescence intensity scales with particle size to nearly the fourth power and is intrinsically heterogeneous. Our study elucidates the fundamental structure-property relationship of unofficial standards for fluorescence microscopy and model nanoplastics as sorbents and carriers of toxic chemicals, resetting expectations for basic concepts of sorption and common practices of ensemble analysis and inference.