# Generating Tagged Micro‐ and Nanoparticles of Poly(ethylene furanoate) and Poly(ethylene terephthalate) as Reference Materials

## TL;DR

Researchers created fluorescently tagged nanoparticles from PET and PEF polymers to help detect and study nanoplastics in the environment and biological systems.

## Contribution

A novel method for producing fluorescently labeled PET and PEF nanoparticles with long-term stability and small sizes for environmental and biological monitoring.

## Key findings

- Fluorescently tagged PET and PEF nanoparticles (200–700 nm) were successfully produced using mechanical and solvent-based methods.
- The nanoparticles showed long-term stability in water (up to 57 days) and were characterized with minimal changes in polymer properties.
- s-SNOM imaging confirmed the ability to detect individual PEF particles as small as 200 nm.

## Abstract

Detecting nanoplastic particles in environmental samples and biological tissues remains a significant challenge, especially in view of newly emerging polymers, not yet commercially exploited. Fluorescent labeling provides a tagging strategy to overcome this limitation by reducing the detection limit of individual particles, especially for small‐sized particles. We present a method for producing labeled nanoparticles (NP/MP) of poly(ethylene terephthalate) (PET) and poly(ethylene furanoate) (PEF), tagged with Alexa Fluor 633 or Alexa Fluor 647. Our preparations used mechanical grinding or solvent‐based approaches (confined impinging jet mixing, ((CIJ, precipitation), generating particles with hydrodynamic diameters of 200–700 nm, displaying long‐term stability in water of up to 57 days. Stable suspensions with concentrations of the particles ranging from 10 µg/mL (surfactant‐free, by solvent mixing) to 5.88 mg/mL (precipitation, containing surfactant) were generated with zeta‐potentials from −5 to −50 mV. Characterization of the nanoparticles by SEC, DSC, and XRD showed no significant changes in molecular weight, thermal behavior, or crystallinity via the solvent‐based methods, compared to the pristine polymer, highlighting their suitability for producing standardized nanoparticle dispersions. Fluorescence spectroscopy of the Alexa‐dye‐labeled particles confirmed the successful incorporation of the Alexa dyes, so improving monitoring of their biological profiles of the PEF‐MP/NPs. s‐SNOM (near field imaging) could identify individual PEF‐particles sized ∼200 nm by direct imaging.

We successfully developed poly(ethylene terephthalate) (PET) and poly(ethylene furanoate) (PEF) nanoparticles and microparticles, covalently tagged with Alexa Fluor 633 or Alexa Fluor 647, using both mechanical and solvent‐based approaches. The particles displaying hydrodynamic diameters between 200 and 700 nm, exhibited long‐term colloidal stability in aqueous suspension.