Exploiting dynamic nonlinearity in upconversion nanoparticles for super-resolution imaging

TL;DR

This paper introduces a method to improve super-resolution microscopy by dynamically modulating excitation intensity to induce nonlinear responses in upconversion nanoparticles, enabling resolution beyond traditional limits.

Contribution

The study demonstrates a novel approach to enhance spatial resolution in superlinear microscopy through excitation modulation and a new image processing algorithm.

Findings

Achieved 130 nm resolution in nanoparticle imaging

Enhanced spatial-frequency information extraction

Demonstrated potential for dynamic nonlinear probes

Abstract

Single-beam super-resolution microscopy, also known as superlinear microscopy, exploits the nonlinear response of fluorescent probes in confocal microscopy. The technique requires no complex purpose-built system, light field modulation, or beam shaping. Here, we present a strategy to enhance spatial resolution of superlinear microscopy by modulating excitation intensity during image acquisition. This modulation induces dynamic optical nonlinearity in upconversion nanoparticles (UCNPs), resulting in variations of higher spatial-frequency information in the obtained images. The high-order information can be extracted with a proposed weighted finite difference imaging algorithm from raw fluorescence images, to generate an image with a higher resolution than superlinear microscopy images. We apply this approach to resolve two adjacent nanoparticles within a diffraction-limited area, improving the resolution to 130 nm. This work suggests a new scope for developing dynamic nonlinear fluorescent probes in super-resolution nanoscopy.