Increasing depth penetration in biological tissue imaging using 808-nm excited Nd3+/Yb3+/Er3+-doped upconverting...

Ytterbium (Yb 3+ )-sensitized upconverting nanoparticles (UCNPs) are excited at 975 nm causing relatively high absorption in tissue. A new type of UCNPs with neodymium (Nd 3+ ) and Yb 3+ codoping is excitable at a 808-nm wavelength. At this wavelength, the tissue absorption is lower. Here we quantify, both experimentally and theoretically, to what extent Nd 3+ -doped UCNPs will provide an increased signal at larger depths in tissue compared to conventional 975-nm excited UCNPs.