A tetraphenylethene-based Schiff base AIEgen with a large Stokes shift as probe for highly sensitive and selective detection of aqueous Cu2+ ions and its application in cell imaging

Synthesis of biscarbazole derivative, detection of the "on-off" sensor property of Cu2+ by fluorimetry, and anti-cancer evaluation

Biscarbazole derivative probe (6) (Z)-2-(3-(((9-heptyl-9H-carbazol-3-yl)methylene)amino)-9H-carbazol-9-yl)ethan-1-ol containing an imine group, which is a sensitive and selective fluorescence chemosensor, was designed and synthesized for the effective evaluation of Cu2+ metal ion levels. The synthesized compounds were characterized using 1H NMR, 13C NMR, FT-IR, and MALDI-TOF MS (for compound 6) spectroscopic data. The interaction model between probe 6 and Cu2+ was determined by combining fluorescence methods, 1H NMR titration, Job's plot, and theoretical calculations. For probe 6, the fluorogenic recognition of Cu2+ was investigated by fluorescence spectroscopy, and the optical changes caused by Cu2+ ions were carried out in ACN/H2O (50:50) solution at pH 7.0. Fluorescence probe 6 was found to "turn-off" its fluorescence in the presence of paramagnetic Cu2+ ions. Probe 6 was determined to have a rapid response within 40s and showed a fluorescence response to Cu2+ with a low detection limit of 0.16 μM. Additionally, in vitro anticancer activity and cell imaging studies of probe 6 against the prostate cell line (PC-3) were performed.

Rational design of peptide-based fluorescent probe for sequential recognitions of Cu(II) ions and glyphosate: Smartphone, test strip, real sample and living cells applications

A new peptide-based fluorescent probe named DMDH with easy-to-synthesize, excellent stability, good water solubility and large Stokes shift (225 nm) was synthesized for highly selective sequential detections of copper ions (Cu2+) and glyphosate (Glyp). DMDH demonstrated great detection performance towards Cu2+via strong fluorescence quenching, and forming non-fluorescence DMDH-Cu2+ ensemble. As a new promising cascade probe, the fluorescence of DMDH-Cu2+ ensemble was significantly recovered based on displacement approach after glyphosate was added. Interestingly, the limit of detections (LODs) for Cu2+ and glyphosate were 40.6 nM and 10.6 nM, respectively, which were far lower than those recommended by the WHO guidelines for drinking water. More importantly, DMDH was utilized to evaluate Cu2+ and glyphosate content in three real water samples, demonstrating that its effectiveness in water quality monitoring. Additionally, it is worth noting that DMDH was also applied to analyze Cu2+ and glyphosate in living cells in view of significant cells permeability and low cytotoxicity. Moreover, DMDH soaked in filter paper was used to create qualitative test strips and visually identify Cu2+ and glyphosate through significant color changes. Furthermore, smartphone RGB color recognition provided a new method for semi-quantitative testing of Cu2+ and glyphosate in the absence of expensive instruments.

Solvent-directed multiple correspondence fluorescent probe for highly selective and sensitive detection of Cu2+ and Mg2

A solvent-directed, new Schiff base multiple correspondence fluorescent probe, (E)-2-(2-hydroxybenzylidene) hydrazine-1-carboxamid (L), was synthesized for selective sensing of Cu2+ and Mg2+ ions. L showed excellent selectivity and high sensitivity toward Cu2+ in "turn off" mode with a detection limit of 40.5 nM in 10 mM, pH = 7.0 PBS buffer. Contrary to that, when acetonitrile was used as the solvent, L exhibited highly selective and sensitive fluorescence sensing ability for Mg2+ in "turn on" mode with a detection limit of 9.5 nM. L can coordinate to Cu2+ and Mg2+ in a 1:1 molar ratio, respectively, evidenced by Job's plot analysis. Their binding modes were investigated by NMR, IR and XPS spectroscopies. Moreover, the satisfied results were obtained when L was used to detect Cu2+ and Mg2+ in real water samples.

Natural protoberberine alkaloid-montmorillonite nanocomposite powders with AIE features for visualizing high-resolution latent fingerprints

Real-time and in-situ fluorescence visualization technologies have attention to in the forensic analysis of latent fingerprints (LFPs). The fingerprint powders with high performance and biocompatibility are essential for imaging LFPs with high definition and safety. In this work, five quaternary protoberberine alkaloid (QPA) derivatives were analyzed with reorganization energy and four-point calculations to explain the relationship between the substituent effect and luminescent properties and further resolve the luminous behaviors of four QPA-based natural products in solution. Thanks to the restriction of the intramolecular motions mechanism, aggregation-induced emission (AIE) active BBC nanoaggregates could sensitively detect explosive analog, 2,4,6-trinitrophenol, at a nanomolar level (9.8 nM of detection limit). Combined with natural montmorillonite (MMT) mineral powders, three levels of details for fingerprints were successfully imaged with solid-luminous BBC/MMT nanocomposites. The insight into the substituted effect of alkoxy groups on the QPA framework not only provides a new concept to design rotor-free AIE luminogens but also expands natural products and their nanocomposites into LFP and detection applications.