UV-Induced Autofluorescence Enhancement Improves Imaging of Single Polystyrene Nanoparticles

Detecting polymer nanoparticles remains a significant challenge due to their weak optical contrast. In this work, we demonstrate a counterintuitive phenomenon: UV illumination enhances rather than bleaches the intrinsic autofluorescence of polystyrene (PS) nanoparticles. This enhancement enables the autofluorescence detection of individual PS nanoparticles down to 100 nm in diameter using a simple, cost-effective UV microscope setup.

Key Discoveries:
- Unexpected Behavior: Contrary to conventional photobleaching, the autofluorescence intensity of PS nanoparticles increases during UV exposure.
- Mechanism: The enhancement arises from reactive oxygen species (ROS)-mediated surface photodecomposition, which exposes fresh emissive domains of the nanoparticle.
- Performance: A 15× signal improvement pushes the limit of detection to 100 nm, enabling reliable single-particle imaging.
- Versatility: The phenomenon is preserved across various sizes and polymer materials (e.g., PMMA, melamine resin) and allows direct discrimination between polymer and metal nanoparticles.

By leveraging a simple UV microscope, this method offers a cost-effective and accessible alternative to more complex techniques like Raman spectroscopy or interferometric scattering microscopy. This approach unlocks new possibilities for high-sensitivity detection of polymer-based nanoparticles in fields such as analytical chemistry, biosensing and/or environmental monitoring.

Read the full paper on free repository: HAL-05686837