# Quantum Well-Enhanced Plasmonic Substrate to Enhance Spontaneously Blinking Fluorescence for Single-Molecule Localization Microscopy

## TL;DR

A new plasmonic substrate with quantum wells boosts fluorescence blinking, improving single-molecule microscopy resolution and reducing required excitation power.

## Contribution

A QW-enhanced plasmonic substrate is introduced to enhance spontaneous blinking and SMLM performance.

## Key findings

- The substrate increases blinking intensity and event frequency, improving SMLM resolution.
- It enables imaging of phosphorylated EGFRs in A549 cells to study kinase inhibition.
- The design reduces the excitation power needed for high-resolution SMLM imaging.

## Abstract

Quantum well (QW)-enhanced plasmonic substrates have
been demonstrated
to improve the blinking fluorescence of spontaneously blinking fluorophores,
which enhances the localization precision and density for single-molecule
localization microscopy (SMLM). The QW-enhanced plasmonic substrate
consists of a three-repeat InGaN QW structure covered by Al nanoparticles.
In addition to the localized surface plasmon enhancement produced
by Al nanoparticles, InGaN QWs with tunable discrete energy levels
and a high-density surface charge distribution can facilitate additional
charge transfer resonances. This effect further enhances the local
surface plasmon resonance around the Al nanoparticles. Moreover, the
interaction between the high-density surface charges of the InGaN
QWs and the oscillating electrons of the Al nanoparticles can lead
to another type of surface plasmon enhancement effect. Therefore,
the blinking intensity and event frequency are significantly increased,
resulting in improved SMLM image resolution under the wide-field fluorescence
excitation. With multiple fluorescence enhancement effects, the QW-enhanced
plasmonic substrate enables SMLM imaging of phosphorylated epidermal
growth factor receptors (EGFRs) in A549 lung cancer cells to quantitatively
investigate the inhibition of EGFR tyrosine kinase. Furthermore, this
QW-enhanced plasmonic substrate can reduce the excitation power needed
for SMLM imaging at an acceptable resolution.