Fig. 7: Rare-earth based materials for monitoring the neural activity.

a UCNPs-mediated visualization of retrograde axonal transport. Reprinted with permission from ref. 22. Copyright 2019 Wiley-VCH GmbH. b The schematic diagram of the NIR-excited optical voltage sensor to real-time monitor the subthreshold activities in mouse cortical neurons. Reprinted with permission from ref. 93. Copyright 2020 American Chemical Society