Two novel solvatochromic AIEE probes, BDM and BDBM have been successfully developed, which can be utilized as fluorescent sensors for the qualitative and quantitative low-level water content in THF or dioxane and cyanide in aqueous media.
This paper discusses the use of N,N'-disubstituted-dihydrodibenzo[a,c]phenazines with typical Vibration-Induced-Emission (VIE) properties for imaging amyloid β (Aβ) fibrils, which are a signature of neurological disorders such as Alzheimer's disease. A water-soluble VIEgen with a red fluorescence emission shows a pronounced, blue-shifted emission with Aβ peptide monomers and fibrils. The enhancement in blue fluorescence can be ascribed to the restriction of the molecular vibration by selectively binding to Aβ. We determine an increasing blue-to-red emission ratio of the VIEgen with both the concentration and fibrogenesis time of Aβ, thereby enabling a ratiometric detection of Aβ in its different morphological forms. Importantly, the VIEgen was proven to be suitable for the fluorescence imaging of small Aβ plaques in the hippocampus of a transgenic mouse brain (five months old), with the blue and red emissions well overlapped on the Aβ. This research offers a new rationale to design molecular VIE probes for biological applications.
Two novel ratiometric fluorometric probes 6 a and 6 b have been designed and synthesized for the detection of Hg and Ag , respectively. Each of these probes is comprised of a 9,14-diphenyl-9,14-dihydrodibenzo[a,c]phenazine (DPAC) skeleton, a tetraphenylethylene (TPE) unit, and two thymine/adenine groups. In this proof-of-concept work, the DPAC unit featuring vibration-induced emission (VIE) characteristics serves as a dual-emission chromogen, whereas the TPE moiety, which is noted for its aggregation-induced emission (AIE) properties, functions mainly as a signal amplifier. The coordination between the thymine/adenine groups and Hg /Ag leads to the formation of aggregates, which restricts the intramolecular vibrations of DPAC and the intramolecular rotations of TPE, activating the AIE effect of TPE and resulting in the bent form of DPAC. Accordingly, the overall fluorescence changed from moderate orange-red (I ) to intense blue light (I ) passing through the white-light region, concurrently with an enhancement of fluorescence at 475 nm and a dramatic increase in the ratio of I /I . Furthermore, the superb sensitivity of 6 a/6 b towards Hg /Ag has been demonstrated by the detection limit, which is as low as 6.1 nm and 0.1 μm, respectively. Both of these values are below the maximum concentration in drinking water permitted by the U.S. Environmental Protection Agency, demonstrating their great potential to be applied for real-world metal-ion sensing.
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