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.
Owing to their versatile functionality and tunable energy dissipation, aggregation-induced emission luminogens (AIEgens) have emerged as ap otential platform for multimodal theranostics.N evertheless,t he construction of AIEactive phototheranostic agents in the second near-infrared window (NIR-II, 1000-1700 nm), which allows superior resolution and minimized photodamage,i ss till af ormidable challenge.H erein, benzo[c]thiophene serves as an electronrich and bulky donor (D)/p-bridge,w hich can enlarge the conjugation length and distort the backbone of an AIEgen. By precise D/p-bridge engineering,h ighly stable NIR-II AIEgen DPBTA-DPTQ nanoparticles are obtained with acceptable NIR-II fluorescence quantum yield and excellent photothermal conversion efficiency.Inaddition, the spatial conformation of DPBTA-DPTQ is determined for the first time by X-ray single crystal diffraction and theoretical simulations.DPBTA-DPTQ NPs have good biocompatibility and show efficient photothermal therapeutic effects in in vitro tests.F urthermore, DPBTA-DPTQ NPs were used in fluorescence-photoacoustic-photothermal trimodal imaging-guided photothermal eradication of tumors in HepG2 and B16-F10 tumor-xenografted mice.
Support-induced strain engineering is useful for modulating the properties of two-dimensional materials. However, controlling strain of planar molecules is technically challenging due to their sub-2 nm lateral size. Additionally, the effect of strain on molecular properties remains poorly understood. Here we show that carbon nanotubes (CNTs) are ideal substrates for inducing optimum properties through molecular curvature. In a tandem-flow electrolyser with monodispersed cobalt phthalocyanine (CoPc) on single-walled CNTs (CoPc/SWCNTs) for CO2 reduction, we achieve a methanol partial current density of >90 mA cm−2 with >60% selectivity, surpassing wide multiwalled CNTs at 16.6%. We report vibronic and X-ray spectroscopies to unravel the distinct local geometries and electronic structures induced by the strong molecule–support interactions. Grand canonical density functional theory confirms that curved CoPc/SWCNTs improve *CO binding to enable subsequent reduction, whereas wide multiwalled CNTs favour CO desorption. Our results show the important role of SWCNTs beyond catalyst dispersion and electron conduction.
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