(31d) Rare Earth Element Doped Nanocrystals for Correlative Cathodoluminescence Electron Microscopy Bioimaging (CCLEM)

Correlative imaging has enabled some of the biggest scientific discoveries in the past. It has become a powerful analytical tool for unravelling structure-function relationships. However, correlating optical and electron microscopy is often challenging due to the resolution mismatch and different sample preparation requirements.¹ Interestingly, accelerated electrons can also generate luminescence signal, creating an effect called cathodoluminescence (CL)^{2, 3}. Correlative cathodoluminescence electron microscopy (CCLEM) bioimaging correlates cathodoluminescence and electron microscopy images⁴. Although luminescence excitation by an electron beam enables sub-diffraction imaging, structural damage to the sample by high energy electrons has been identified as a potential obstacle.

Here, we present rare earth (RE) element doped nanocrystals as bright and stable probes for high-quality CCLEM. We report on the performance of RE-doped nanocrystals in CCLEM compared to fluorophores and quantum dots commonly used as molecular labels in biology. The influence of the electron beam parameters on image quality and resolution will be presented along with the first experimental demonstration of correlative cathodoluminescence back-scattering electron microscopy on focused ion beam (FIB)-sectioned biological samples⁴. We also demonstrate how exogenous nanoparticles can be easily distinguished from naturally occurring cellular features based on the characteristic optical emission. Taken together, we demonstrate the potential of the CCLEM approach for the acquisition of high-quality luminescence and electron microscopy images with nanometric resolution of biological samples.

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2. Mahfoud, Z.; Dijksman, A. T.; Javaux, C.; Bassoul, P.; Baudrion, A.-L.; Plain, J.; Dubertret, B.; Kociak, M. The Journal of Physical Chemistry Letters 2013, 4, (23), 4090-4094.
3. Atre, A. C.; Brenny, B. J. M.; Coenen, T.; García-Etxarri, A.; Polman, A.; Dionne, J. A. Nature Nanotechnology 2015, 10, 429.
4. Keevend, K.; Stiefel, M.; Neuer, A. L.; Matter, M. T.; Neels, A.; Bertazzo, S.; Herrmann, I. K. Nanoscale 2017, 9, (13), 4383-4387.