| 1. |
- Bergstrand, Jan, et al.
(author)
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On the decay time of upconversion luminescence
- 2019
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In: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 11:11, s. 4959-4969
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Journal article (peer-reviewed)abstract
- In this study, we systematically investigate the decay characteristics of upconversion luminescence (UCL) under anti-Stokes excitation through numerical simulations based on rate-equation models. We find that a UCL decay profile generally involves contributions from the sensitizer's excited-state lifetime, energy transfer and cross-relaxation processes. It should thus be regarded as the overall temporal response of the whole upconversion system to the excitation function rather than the intrinsic lifetime of the luminescence emitting state. Only under certain conditions, such as when the effective lifetime of the sensitizer's excited state is significantly shorter than that of the UCL emitting state and of the absence of cross-relaxation processes involving the emitting energy level, the UCL decay time approaches the intrinsic lifetime of the emitting state. Subsequently, Stokes excitation is generally preferred in order to accurately quantify the intrinsic lifetime of the emitting state. However, possible cross-relaxation between doped ions at high doping levels can complicate the decay characteristics of the luminescence and even make the Stokes-excitation approach fail. A strong cross-relaxation process can also account for the power dependence of the decay characteristics of UCL.
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| 2. |
- Guo, Xin, et al.
(author)
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Achieving low-power single-wavelength-pair nanoscopy with NIR-II continuous-wave laser for multi-chromatic probes
- 2022
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In: Nature Communications. - : Springer Nature. - 2041-1723. ; 13:1
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Journal article (peer-reviewed)abstract
- The authors introduce stimulated-emission induced excitation depletion (STExD) nanoscopy using a single pair of low-power, near-infrared, continue-wave lasers. Emission of multichromatic probes is inhibited by cascade amplified depletion in lanthanide upconversion systems induced by manipulating their common sensitizer. 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., Nd3+, Yb3+, Er3+, Ho3+, Pr3+, Eu3+, Tm3+, Gd3+, and Tb3+) by manipulating their common sensitizer, i.e., Nd3+ ions, using a 1064-nm laser. With NaYF4: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.
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| 3. |
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| 4. |
- Peng, Xingyun, et al.
(author)
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Fast upconversion super-resolution microscopy with 10 μs per pixel dwell times
- 2019
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In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 11:4, s. 1563-1569
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Journal article (peer-reviewed)abstract
- A facile strategy is proposed to simultaneously enhance the intensity (10 times) and accelerate the transients (one fifth) of the 455 nm emission of Yb3+/Tm3+ co-doped NaYF4 nanocrystals via highly-doped sensitizers and a sandwich structure.
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| 5. |
- Wu, Qiusheng, et al.
(author)
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Non-bleaching fluorescence emission difference microscopy using single 808-nm laser excited red upconversion emission
- 2017
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In: Optics Express. - : Optical Society of America. - 1094-4087. ; 25:25, s. 30885-30894
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Journal article (peer-reviewed)abstract
- Optical super-resolution microscopy has become a powerful technique to help scientists to monitor the sample of interest at nanoscale. Fluorescence emission difference (FED) microscopy, a very facile super-resolution method, does not require high depleting laser intensity and is independent on the species of agents, which makes FED microscopy possess great potential. However, to date, the biomarkers applied in FED microscopy usually suffer from a photo-bleaching problem. In this work, by introducing Er3+ activated upconverting nanoparticles with red-color emission and non-photobleaching properties, we demonstrate nonbleaching super-resolution imaging with FED microscopy. The dopant neodymium ions (Nd3+) can work as highly efficient sensitizing ions and enable near infrared 808-nm CW laser excitation of relatively low power, which would potentially reduce high intensity/short-wavelength light induced tissue damage. Both simulations and experiments on monodispersed NaYF4:Nd3+/Yb3+/Er3+@NaYF4:Nd3+ UCNPs also indicate that the easy saturation of the multiphoton properties of these UCNPs is beneficial to resolution enhancement in FED microscopy.
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| 6. |
- Zhan, Qiuqiang, et al.
(author)
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Achieving high-efficiency emission depletion nanoscopy by employing cross relaxation in upconversion nanoparticles
- 2017
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In: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 8:1
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Journal article (peer-reviewed)abstract
- Stimulated emission depletion microscopy provides a powerful sub-diffraction imaging modality for life science studies. Conventionally, stimulated emission depletion requires a relatively high light intensity to obtain an adequate depletion efficiency through only light–matter interaction. Here we show efficient emission depletion for a class of lanthanide-doped upconversion nanoparticles with the assistance of interionic cross relaxation, which significantly lowers the laser intensity requirements of optical depletion. We demonstrate two-color super-resolution imaging using upconversion nanoparticles (resolution ~ 66 nm) with a single pair of excitation/depletion beams. In addition, we show super-resolution imaging of immunostained cytoskeleton structures of fixed cells (resolution ~ 82 nm) using upconversion nanoparticles. These achievements provide a new perspective for the development of photoswitchable luminescent probes and will broaden the applications of lanthanide-doped nanoparticles for sub-diffraction microscopic imaging.
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