Rational Design of NIR-II AIEgens with Ultrahigh Quantum Yields for Photo- and Chemiluminescence Imaging

Abstract

Fluorescence imaging in the second near-infrared window (NIR-II, 1000–1700 nm) using small-molecule dyes has high potential for clinical use. However, many NIR-II dyes suffer from the emission quenching effect and extremely low quantum yields (QYs) in the practical usage forms. The AIE strategy has been successfully utilized to develop NIR-II dyes with donor–acceptor (D–A) structures with acceptable QYs in the aggregate state, but there is still large room for QY improvement. Here, we rationally designed a NIR-II emissive dye named TPE-BBT and its derivative (TPEO-BBT) by changing the electron-donating triphenylamine unit to tetraphenylethylene (TPE). Their nanoparticles exhibited ultrahigh relative QYs of 31.5% and 23.9% in water, respectively. By using an integrating sphere, the absolute QY of TPE-BBT nanoparticles was measured to be 1.8% in water. Its crystals showed an absolute QY of 10.4%, which is the highest value among organic small molecules reported so far. The optimized D–A interaction and the higher rigidity of TPE-BBT in the aggregate state are believed to be the two key factors for its ultrahigh QY. Finally, we utilized TPE-BBT for NIR-II photoluminescence (PL) and chemiluminescence (CL) bioimaging through successive CL resonance energy transfer and Förster resonance energy transfer processes. The ultrahigh QY of TPE-BBT realized an excellent PL imaging quality in mouse blood vessels and an excellent CL imaging quality in the local arthrosis inflammation in mice with a high signal-to-background ratio of 130. Thus, the design strategy presented here brings new possibilities for the development of bright NIR-II dyes and NIR-II bioimaging technologies.

Highly efficient dual-state emission and two-photon absorption of novel naphthalimide functionalized cyanostilbene derivatives with finely tuned terminal alkoxyl groups

“…8–10 Since then, OLs with AIE properties have attracted many research interests. 11–18 However, both conventional and AIE OLs mainly emit in a single state, namely either in solution or in the aggregated state. OLs that are capable of yielding strong fluorescence in both solution and the aggregated state, referred to as dual-state emission (DSE), have been less explored.…”

Structures and Applications of NIR‐II AIEgens Containing Benzobisthiadiazole Derivatives

“…Secondly, the interesting phenomenon of QY greatly increased after tetraphenylethylene (TPE) group replaced triphenylamine (TPA) group (Figure 10A) was explained strictly and systematically by using single crystal analysis and computational studies. The QY of TPE‐BBT photoluminescent nanoparticles was the highest value of organic small molecules reported so far [79] . TPE‐BBT PLNPs, TPEO‐BBT PLNPs and TPA‐BBT PLNPs were formed by encapsulating TPE‐BBT, TPEO‐BBT and TPA‐BBT respectively with F127 (Figure 1A).…”

“…The QY of TPE-BBT photoluminescent nanoparticles was the highest value of organic small molecules reported so far. [79] TPE-BBT PLNPs, TPEO-BBT PLNPs and TPA-BBT PLNPs were formed by encapsulating TPE-BBT, TPEO-BBT and TPA-BBT respectively with F127 (Figure 1A). Among them, TPE-BBT PLNPs had a nano particle diameter of less than 30 nm and strong light stability.…”

Coordination Polymerization-Induced Emission Based on a Salicylaldehyde Hydrazone AIEgen toward Zn2+ Detection

“…When f w was above 40%, the aggregates became even smaller (Figure c) and the fluorescence intensity decreased. − This is probably due to the reduction in the size of aggregates, leading to more free molecules on their surface. These free molecules will exhibit an active molecular motion behavior due to the lack of spacial restriction, causing an enhanced nonradiative decay and a relatively lower fluorescence. , …”