Achieving low-power single-wavelength-pair nanoscopy with NIR-II continuous-wave laser for multi-chromatic probes
Xin Guo, Rui Pu, Zhimin Zhu, Shuqian Qiao, Yusen Liang, Bingru Huang, Haichun Liu, Lucía Labrador‐Páez, Uliana Kostiv, Pu Zhao, Qiusheng Wu, Jerker Widengren, Qiuqiang Zhan
Abstract
Abstract Stimulated emission depletion (STED) microscopy is a powerful diffraction-unlimited technique for fluorescence imaging. Despite its rapid evolution, STED fundamentally suffers from high-intensity light illumination, sophisticated probe-defined laser schemes, and limited photon budget of the probes. Here, we demonstrate a versatile strategy, stimulated-emission induced excitation depletion (STExD), to deplete the emission of multi-chromatic probes using a single pair of low-power, near-infrared (NIR), continuous-wave (CW) lasers with fixed wavelengths. With the effect of cascade amplified depletion in lanthanide upconversion systems, we achieve emission inhibition for a wide range of emitters ( e.g ., Nd 3+ , Yb 3+ , Er 3+ , Ho 3+ , Pr 3+ , Eu 3+ , Tm 3+ , Gd 3+ , and Tb 3+ ) by manipulating their common sensitizer, i.e., Nd 3+ ions, using a 1064-nm laser. With NaYF 4 :Nd nanoparticles, we demonstrate an ultrahigh depletion efficiency of 99.3 ± 0.3% for the 450 nm emission with a low saturation intensity of 23.8 ± 0.4 kW cm −2 . We further demonstrate nanoscopic imaging with a series of multi-chromatic nanoprobes with a lateral resolution down to 34 nm, two-color STExD imaging, and subcellular imaging of the immunolabelled actin filaments. The strategy expounded here promotes single wavelength-pair nanoscopy for multi-chromatic probes and for multi-color imaging under low-intensity-level NIR-II CW laser depletion.