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The weakly alkaline microenvironment (pH ~8.0) in mitochondria plays a vital role in maintaining its morphology and function. Thus monitoring mitochondrial pH (pH mito) is of great significance. Herein, a ratiometric fluorescent probe (ENBT) for pHmito imaging in mitochondria of living cells is reported. pH variation closely correlates to intramolecular charge transfer (ICT) from naphthol to β-naphthothiazolium. ENBT exhibits a remarkable decrease on ratiometric fluorescence at λ em1 /λ em2 = F 595 / F 700 in response to pH variation within 6.30–9.29. In addition, ENBT has an ideal p K a value of 7.94 ± 0.08, which is advantageous in accurate sensing of pH mito. Moreover, ENBT has a Stokes shift of >150 nm, which effectively eliminates the potential interference from the excitation irradiation. ENBT shows excellent capability for specific staining of mitochondria with low cytotoxicity, which is most suitable for pH mito imaging in live cells. The probe was applied for monitoring pH mito variation in mitochondria of live cells caused by H 2 O 2 , NAC (N-Acetyl- l -cysteine), NH 4 Cl, carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and lactate/pyruvate. The morphological alterations of mitochondria in living cells after treatment by CCCP were further evaluated. [Display omitted] • A ratiometric fluorescent probe (ENBT) is developed for pH imaging based on ICT. • ENBT exhibits near infrared as well as ratiometric emission at F 595 / F 700. • ENBT shows an ideal p K a of 7.94 ± 0.08 to match the mitochondrial pH (~8.0). • ENBT exhibits large Stokes shifts (167/197 nm at pH 4.42/11.40). [ABSTRACT FROM AUTHOR]

Fluorescent probes containing 1,8-naphthalimide dyes have been used to detect biomolecules in the environmental and biological fields. However, most of the probes only exhibit single fluorescent output to one analyte, making them insufficient for detection of more analytes. Herein, we developed a novel 1,8-naphthalimide-based lysosome-targeting dual-analyte sensitive fluorescent probe (DPPP) for the detection of pH and palladium (Pd0) using two different emissive channels. The probe showed high selectivity, large Stokes shifts (Δλ ≥ 100 nm) and enhanced response to pH, with blue emission at 485 nm via a morpholine group, and responsive to Pd0 concentration, with yellow emission at 545 nm via an allylcarbamate group. The effect of DPPP was successfully observed for sensitive visualizing pH and Pd0 concentration in the lysosome of HeLa cells and zebrafish using fluorescence microscopy. This work provides guidance for the design of dual-analyte fluorescent probes. [Display omitted] • First-ever dual-analyte fluorescent probe (DPPP) for the detection of pH and palladium (Pd0) has been developed. • DPPP was successfully used to detect dual analytes via the synergistic effects of PET and ICT. • DPPP could be successfully applied to cellular and in vivo imaging of pH and Pd0. • Co-localization experiments indicated that DPPP mainly located in the lysosomal organelle. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel coumarin-based fluorescent probe with large Stokes shift (216 nm) is designed and synthesized. • The probe exhibits fast-response (<4s), high sensitivity and low detection limit (8.82 × 10−8 M) towards Cys. • The probe is successfully applied in living cells. A new fluorescence probe L , which featured with a large Stokes shift (216 nm), was designed for sensitive detection of cysteine (Cys) and a potential sensing mechanism derived from excited state intramolecular proton transfer (ESIPT) was proposed. More importantly, probe L exhibits higher selective to Cys than other amino acid due to its specific cyclization between acrylate group and Cys. Meanwhile, the probe L shows a low detection limit of 8.82 × 10−8 M, which is enough for detecting Cys in organisms. Furthermore, this probe displays high biocompatibility and can image Cys in living cells. [ABSTRACT FROM AUTHOR]

• It is convenient to detect UO 2 2+: acidity, high water ratio and large Stokes shift. • A mechanism was proposed how the different water ratios affected the fluorescence. • The recognition mechanism and combination model of USC-001 with UO 2 2+ were proposed. • A new method for detecting UO 2 2+ in water samples and cells was set up. Uranium mining, refining and spent fuel reprocessing are mostly carried out in an acidity and high water ratio environment. But there are currently fewer fluorescent probes that can meet this requirement. For this purpose, it is a urgent problem to design and synthesis fluorescent sensor for detection of uranium in these conditions. A novel triphenylamine-based fluorescent sensor (USC-001) has been design and prepared for the detection of uranyl ions in acidic and high water ratio environments and biologic samples. And even though the concentration of other metal ions is 5 times higher than that of uranyl ions, the probe is still have good selectivity to UO 2 2+. In addition, a large number of auxiliary simulation calculations and experiment not only reveal the mechanism of the influence of water ratio on the change of the fluorescence spectrum, but also propose the mechanism and coordination mode of USC-001 for identifying UO 2 2+. Furthermore, USC-001 has been successfully used to detect uranyl ions in actual water samples and biological cells. [ABSTRACT FROM AUTHOR]