Spectral properties of Tm3+ doped NaYF4 up-converting nanoparticles under single and double photoexcitation wavelengths

Frequency Encoding of Upconversion Nanoparticle Emission for Multiplexed Imaging of Spectrally and Spatially Overlapping Lanthanide Ions

We present frequency encoded upconversion (FE-UPCON) widefield microscopy, an imaging approach that allows for multiplexed signal recovery based on frequency encoding of selected upconverted lanthanide ion emission rather than separation based on energy or time. FE-UPCON allows for the separation of luminescence from spectrally and spatially overlapping trivalent lanthanide ions (Ln³⁺) in upconversion nanoparticles (UCNPs). Utilizing the numerous electronic energy levels of Ln³⁺, one can generate a frequency encoded signal by periodic coexcitation with a secondary light source (modulated at a chosen frequency) that, for a particular wavelength, enhances the luminescence of the Ln³⁺ of interest. We demonstrate that it is possible to selectively image spectrally overlapping UCNPs co-doped with Yb³⁺/Ho³⁺ or Yb³⁺/Er³⁺ by FE-UPCON in cells up to 10 frames per second on a conventional widefield microscope with the simple extension of an additional secondary light source and a chopper wheel for modulation. Additionally, we show that FE-UPCON does not compromise sensitivity and that single UCNP detection is obtainable. FE-UPCON adds a new dimension (frequency space) for multiplexed imaging with UCNPs.

A new forum for upconversion research: the UPCON conference

The Conference and Spring School on Properties, Design and Applications of Upconversion Nanomaterials (UPCON) provides a new forum for all experts and newcomers in the field of upconversion research. On the occasion of the second UPCON 2018 in Valencia (Spain), we are pleased to present a collection of 12 reviews and research articles that reflect recent advances in upconversion materials, their unique luminescent properties and many applications spanning from nanoscale thermometry to biomedicine.