Light-emitting diode excitation for upconversion microscopy: a quantitative assessment

Yueying Cao, Xianlin Zheng, Simone De Camillis, Bingyang Shi, James A. Piper, Nicolle H. Packer, Yiqing Lu*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


Lanthanide-based upconversion nanoparticles (UCNPs) generally require high power laser excitation. Here we report wide-field upconversion microscopy at single-nanoparticle sensitivity using incoherent excitation of a 970-nm light-emitting diode (LED). We show that due to its broad emission spectrum, LED excitation is about 3 times less effective for UCNPs and generates high background compared to laser illumination. To counter this, we use time-gated luminescence detection to eliminate the residual background from the LED source, so that individual UCNPs with high sensitizer (Yb3+) doping and inert shell protection become clearly identified under LED excitation at 1.18 W cm-2, as confirmed by correlated electron microscopy images. Hydrophilic UCNPs are obtained by polysaccharide coating via a facile ligand exchange protocol to demonstrate imaging of cellular uptake using LED excitation. These results suggest a viable approach to bypassing the limitations associated with high-power lasers when applying UCNPs and upconversion microscopy to life science research.

Original languageEnglish
Pages (from-to)8487-8492
Number of pages6
JournalNano Letters
Issue number12
Early online date16 Sept 2020
Publication statusPublished - 9 Dec 2020


  • upconversion nanoparticle
  • light-emitting diode
  • single-nanoparticle detection
  • time-gated luminescence
  • hydrophilic functionalization


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