Guest-host doped strategy for constructing ultralong-lifetime near-infrared organic phosphorescence materials for bioimaging

Abstract

Organic near-infrared room temperature phosphorescence materials have unparalleled advantages in bioimaging due to their excellent penetrability. However, limited by the energy gap law, the near-infrared phosphorescence materials (>650 nm) are very rare, moreover, the phosphorescence lifetimes of these materials are very short. In this work, we have obtained organic room temperature phosphorescence materials with long wavelengths (600/657–681/732 nm) and long lifetimes (102–324 ms) for the first time through the guest-host doped strategy. The guest molecule has sufficient conjugation to reduce the lowest triplet energy level and the host assists the guest in exciton transfer and inhibits the non-radiative transition of guest excitons. These materials exhibit good tissue penetration in bioimaging. Thanks to the characteristic of long lifetime and long wavelength emissive phosphorescence materials, the tumor imaging in living mice with a signal to background ratio value as high as 43 is successfully realized. This work provides a practical solution for the construction of organic phosphorescence materials with both long wavelengths and long lifetimes.

Manipulation of Triplet Excited States in Two‐Component Systems for High‐Performance Organic Afterglow Materials

“…Many organic molecules possess singlet‐triplet splitting energy ( Δ E ST ) of around 0.5 eV or even larger and consequently show small rate constants of intersystem crossing. To address this issue, Dong, Cai and Lei proposed that organic matrices with T 1 levels sandwiched between S 1 and T 1 levels of organic dopants can mediate intersystem crossing of the organic dopants [34,56,71] . In the reported studies where triphenylphosphine and triphenylarsenic were used as organic matrices, luminescent dopants such as triphenylamine derivatives have been found to show wide‐range color‐tunable RTP properties which can serve as printable and writable security inks (Figure 6).…”

“…Tremendous development of novel chemical structures, new design strategies and intriguing applications have been achieved in the field of RTP and organic afterglow materials. In particular, the past several years have witnessed the exciting advancements of high‐performance organic afterglow materials based on two‐component design strategies [13,15,38,51–57] …”

Ultraviolet phosphorescent carbon nanodots

“…However, the ISC of the 1 (n, π * ) → 3 (n, π * ) or 1 (π, π * ) → 3 (π, π * ) with similar electronic configurations is not effective due to the spin-forbidden transition, which leads to the low efficiency of SOC 27 . Therefore, for the recombination rate of triplet excitons, the 3 (π, π * ) triplet has a slow recombination rate compared to 3 (n, π * ) due to the spin-forbidden transition 28 , 29 . In this system, the n orbit is one of the sp 2 orbits of the N atom, and the electron transition from the sp 2 to the p x orbit or the p x to the sp 2 orbit of the N atom will produce a one-unit change in the orbital angular momentum, meeting the required angular momentum of the electron spin-flip (from −1/2 to 1/2; or 1/2 to −1/2) 30 , 31 , which is necessary for the triplet exciton population of the CNDs.…”

Near‐Infrared Room‐Temperature Phosphorescence in Arylselanyl BODIPY‐Doped Materials

“…To the best of our knowledge, NIR emissive RTP systems using host-guest doping strategies have rarely been reported. [19] Our research group previously proposed selenium-containing BODIPYs as triplet photosensitizers for application in triplettriplet annihilation upconversion. [20] Although the introduction of a phenylselanyl group into the BODIPY core results in an efficient ISC channel to the excited triplet state, as shown by high singlet oxygen production (Φ = 86 %) in solution, the RTP properties were undetectable.…”

“…However, the preparation of NIR RTP is still in its infancy. To the best of our knowledge, NIR emissive RTP systems using host‐guest doping strategies have rarely been reported [19] …”