The brightness of organic fluorescence materials determines their resolution and sensitivity in fluorescence display and detection. However, strategies to effectively enhance the brightness are still scarce. Conventional planar π-conjugated molecules display excellent photophysical properties as isolated species but suffer from aggregation-caused quenching effect when aggregated owing to the cofacial π–π interactions. In contrast, twisted molecules show high photoluminescence quantum yield (ΦPL) in aggregate while at the cost of absorption due to the breakage in conjugation. Therefore, it is challenging to integrate the strong absorption and high solid-state ΦPL, which are two main indicators of brightness, into one molecule. Herein, we propose a molecular design strategy to boost the brightness through the incorporation of planar blocks into twisted skeletons. As a proof-of-concept, twisted small-molecule TT3-oCB with larger π-conjugated dithieno­[3,2-b:2′,3′-d]­thiophene unit displays superb brightness at the NIR-IIb (1500–1700 nm) than that of TT1-oCB and TT2-oCB with smaller thiophene and thienothiophene unit, respectively. Whole-body angiography using TT3-oCB nanoparticles presents an apparent vessel width of 0.29 mm. Improved NIR-IIb image resolution is achieved for femoral vessels with an apparent width of only 0.04 mm. High-magnification through-skull microscopic NIR-IIb imaging of cerebral vasculature gives an apparent width of ∼3.3 μm. Moreover, the deeply located internal organ such as bladder is identified with high clarity. The present molecular design philosophy embodies a platform for further development of in vivo bioimaging.

Huanglongbing (HLB) is one of the most destructive diseases of citrus, which has posed a serious threat to the global citrus production. This research was aimed to explore the use of chlorophyll fluorescence imaging combined with feature selection to characterize and detect the HLB disease. Chlorophyll fluorescence images of citrus leaf samples were measured by an in-house chlorophyll fluorescence imaging system. The commonly used chlorophyll fluorescence parameters provided the first screening of HLB disease. To further explore the photosynthetic fingerprint of HLB infected leaves, three feature selection methods combined with the supervised classifiers were employed to identify the unique fluorescence signature of HLB and perform the three-class classification (i.e., healthy, HLB infected, and nutrient deficient leaves). Unlike the commonly used fluorescence parameters, this novel data-driven approach by using the combination of the mean fluorescence parameters and image features gave the best classification performance with the accuracy of 97%, and presented a better interpretation for the spatial heterogeneity of photochemical and non-photochemical components in HLB infected citrus leaves. These results imply the potential of the proposed approach for the citrus HLB disease diagnosis, and also provide a valuable insight for the photosynthetic response to the HLB disease.

or completely in the state of aggregation, impeding the progress of some specific applications. [2] In 2001, the uncommon luminogen system noted as aggregationinduced emission (AIE) [3] broke down the captivity of Förster's discovery named aggregation-caused quenching (ACQ), which brought a new wonderland for organic fluorophores. The intrinsic tendency to form aggregates in concentrated solutions or the solid state actively promotes the emission intensity of the fluorophores with AIE characteristics. Years of unremitting exploration has accumulated design experience of diverse AIEgens [4] and shaped plentiful innovated applications for stimuli sensing, [5] optoelectronic systems, [6] molecular detection, [7] bio-imaging, [8,9] and so on. Taking advantages of AIE dots with high resistance to photobleaching and excellent reliability, multifarious specific bio-sensing modes, including bio-imaging, launched on a grand. [8,10] The development of the AIE universe provides potential diagnostic and therapeutic means in clinic. Nowadays, efforts of AIEgens for fluorescence imaging in mice have already been

Lymph node metastasis is a major metastatic route of cancer and significantly influences the prognosis of cancer patients. Radical lymphadenectomy is crucial for a successful surgery. However, iatrogenic normal organ injury during lymphadenectomy is a troublesome complication. Here, this paper reports a kind of organic nanoprobes (IDSe-IC2F nanoparticles (NPs)) with excellent second near-infrared (NIR-II) fluorescence and photothermal properties. IDSe-IC2F NPs can effectively label lymph nodes and helped achieve high-contrast lymphatic imaging. More importantly, by jointly using IDSe-IC2F nanoparticles and other kinds of nanoparticles with different excitation/emission properties, a multichannel NIR-II fluorescence imaging modality and imaging-guided lymphadenectomy is proposed. With the help of this navigation system, the iatrogenic injury can be largely avoided. In addition, NIR-II fluorescence imaging-guided photothermal treatment ("hot" strategy) can ablate those metastatic lymph nodes which are difficult to deal with during resection ("cold" strategy). Nanoprobes-assisted and multichannel NIR-II fluorescence imaging-guided "cold" and "hot" treatment strategy provides a general new basis for the future precision surgery.

No abstract

Three-photon fluorescence microscopic (3PFM) bioimaging is a promising imaging technique for visualizing the brain in its native environment thanks to its advantages of high spatial resolution and large imaging depth. However, developing fluorophores with strong three-photon absorption (3PA) and bright emission that meets the requirements for efficient three-photon fluorescence microscopic (3PFM) bioimaging is still challenging. Herein, four bright fluorophores with aggregation-induced emission features are facilely synthesized, and their powders exhibit high quantum yields of up to 56.4%. The intramolecular engineering of luminogens endows (E)-2-(benzo­[d]­thiazol-2-yl)-3-(7-(diphenylamino)-9-ethyl-9H-carbazol-2-yl)­acrylonitrile (DCBT) molecules with bright near-infrared emission and large 3PA cross sections of up to 1.57 × 10–78 cm6 s2 photon–2 at 1550 nm, which is boosted by 3.6-fold to 5.61 × 10–78 cm6 s2 photon–2 in DCBT dots benefiting from the extensive intermolecular interactions in molecular stacking. DCBT dots are successfully applied for 3PFM imaging of brain vasculature on mice with a removed or intact skull, providing images with high spatial resolution, and even small capillaries can be recognized below the skull. This study will inspire more insights for developing advanced multiphoton absorbing materials for biomedical applications.

As the shortest segment of carbon nanotubes (CNTs), cycloparaphenylenes (CPPs) offer a well‐defined alternative for CNTs as the fluorophores in bioimaging. However, most of CPPs emit blue or yellow light, the bright red‐emitting CPP materials required by bioimaging, particularly in vivo imaging, are still lacking. Here, it is shown that a CPP (TB[9]CPP) with red emission up to 650 nm is successfully synthesized and characterized. The fluorescence quantum yields of TB[9]CPP are measured up to 44% in chloroform and 17% as nanodots in aqueous media. Meanwhile, the water‐soluble nanodots present outstanding three‐photon fluorescence performances, thereby are utilized for in vivo probing of brain vessels by three‐photon fluorescence microscopic imaging technique, exhibiting a high penetration depth, good resolution, and clear image contrast.

Fluorescence imaging performed in the 1500−1700 nm spectral range (labeled near-infrared IIb, NIR-IIb) promises high imaging contrast and spatial resolution for its little photon scattering effect and minimum autofluorescence. Though inorganic and organic probes have been developed for NIR-IIb bioimaging, most are in the preclinical stage, hampering further clinical application. Herein, we showed that indocyanine green (ICG), a US Food and Drug Administration (FDA)-approved agent, exhibited a remarkable amount of NIR-IIb emission when dissolved into different protein solutions, including human serum albumin, rat bile, and fetal bovine serum. We performed fluorescence imaging in the NIR-IIb window to visualize structures of the lymph system, extrahepatic biliary tract, and cerebrovascular. The results demonstrated that proteins promoted NIR-IIb emission of ICG in vivo and that NIR-IIb imaging with ICG preserved a higher signal-to-background ratio and spatial resolution compared with the conventional NIR-II fluorescence imaging. Our findings confirm that NIR-IIb fluorescence imaging can be successfully performed using the clinically approved agent ICG. Further clinical application in the NIR-IIb region would hopefully be carried out with appropriate ICG−protein solutions.