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

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.