Tm³⁺ heavily doped NIR-III bioprobe with 1 µm Stokes shift towards deep-tissue applications

Abstract

Recently developed rare earth ions doped NIR-NIR bioprobes, with excitation and emission both falling in the NIR region, have attracted wide attention due to their deep-tissue penetration, high signal-to-noise ratio, and high imaging resolution. The current NIR-NIR bioprobes focused mainly on the 1.5 µm emission of Er3+. Here, we developed a novel bioprobe utilizing the 1.8 µm emission of Tm3+ upon 0.8 µm excitation. After an inert shell effectively suppressing the surface quenching effect, the strong cross relaxation 3H4 + 3H6 → 3F4 + 3F4 between heavily doped Tm3+ greatly improves the luminescence intensity at 1.8 µm. As a result, the formed Tm3+ based NIR-III bioprobe exhibits better penetration ability of the state-of-the-art Er3+ based NIR-III bioprobe, and holding an even larger Stokes shift beneficial for the multiplexed bioimaging and labeling applications.

Tailored NIR‐II Lanthanide Luminescent Nanocrystals for Improved Biomedical Application

“…Similarly, the NIR‐II emissions of Tm 3+ at 1210 nm and 1470 nm are unusually weak as well. For example, the typical 1470 nm emission from 3 H 4 to 3 F 4 transition [ 102 ] in a 980 nm excited Yb 3+ /Tm 3+ system is a two‐photon upconversion process, which intrinsically has lower QY and brightness than downshifting luminescence. Recently, scientists have demonstrated that probes with bright 1460 nm emission can enable high‐contrast in vivo imaging because of the reduced photon‐scattering caused by water absorption.…”