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Two kinds of carbon dots (CDs) with different solubility, aqueous soluble CDs (ACDs) and organic soluble CDs (OCDs), were produced at the same time by one step hydrothermal synthesis method using sorbic acid and proline as carbon precursor and nitrogen dopant, respectively. The synthesized CDs were characterized by means of UV, fluorescence, TEM, elemental analysis, IR and XPS et al. Based on the effective and proportional fluorescence quenching by Cr(VI), ACDs were successfully used as a high sensitive and selective probe for Cr(VI) detection. Internal filtration effect (IFE) played an important role in the quenching process. Under the optimal conditions, linear response for Cr(Ⅵ) was observed in the range of 0.5–100 μmol/L, and the calculated detection limit was 34 nmol/L. The method has been satisfactorily applied to detect Cr(VI) ions in real water samples of our campus. Then, the ACDs were further applied for cell imaging in B16F10 cells. Furthermore, OCDs were well dispersed into PMMA to fabricate OCDs/PMMA composites as fluorescent films. ACDs and OCDs were produced at the same time and their multi-functional applications were explored like Cr(Ⅵ) detection, bioimaging, and OCDs/PMMA films. Image 1 • Two kinds of CDs were simply synthesized by one-step hydrothermal method directly. • The fluorescence of ACDs can be selectively quenched by Cr(VI) and applied to detect Cr(VI) in real water samples. • The ACDs are successfully applied for cell imaging in B16F10 Cells. • The OCDs/PMMA composites have been fabricated as fluorescent films. [ABSTRACT FROM AUTHOR]

Hypochloric acid (HOCl) plays vital roles in cell signaling and homeostasis which involved in many related diseases. Therefore, the accurate detected level of OCl− for discussing the complex contributions of OCl− to human health is of great significance. In this study, a novel mitochondrion-targeting fluorescent probe DMI bearing a carbon-carbon double bond as an OCl−-responsive site has been developed. Probe DMI exhibited specific fluorescence response toward OCl− with fast response (within 4 s) and high sensitivity (detection limit is 0.05 μM), where the obvious color changes could be observed by the naked eye. More importantly, DMI could be applied in the bioimaging of OCl− in living A549 cells successfully benefited from its good sensing properties and low toxicity. Fluorescence co-localization test was further carried out and confirmed mitochondria-targetable ability of DMI which can be used for investigating physiological function of HOCl at organelle levels. Image 1 • Probe DMI is a mitochondria-targeting visual fluorescence probe. • DMI could highly sensitive and selective detected of hypochlorite. • The mechanism of DMI has been proved to be via oxidation fracture of C C. • DMI can be used to imaging of OCl− in living A549 cells. [ABSTRACT FROM AUTHOR]

Abstract Hydrogen sulfide (H 2 S) has been considered to be involved in cytoprotective processes and redox signaling. It is very meaningful to track and analyze it in mitochondria. Herein, we report a novel "turn-on" mitochondria-targeting near-infrared fluorescent probe (Mito-NIR-SH) for detection of H 2 S in living cells, which was designed and synthesized by introducing 2,4-dinitrophenyl as fluorescence quenching group and H 2 S response moiety into Changsha near-infrared fluorophore (CS-OH). The structure of the fluorophore and the probe were characterized by 1H NMR, 13C NMR and mass spectrometry. Meanwhile, Mito-NIR-SH could quantitatively detect H 2 S at concentrations ranging from 0 to 30 μM with a detection limit as low as 89.3 nM, showing good chemical stability, fast "turn-on" response, selectively mitochondrial location, as well as high sensitivity and selectivity toward H 2 S. Based on this, it was successfully applied to imaging exogenous and endogenous H 2 S in living HeLa cells via confocal fluorescence microscopy. Graphical abstract fx1 Highlights • A novel chemically stable mitochondrial-targeting NIR probe has been synthesized. • Fast response to H 2 S with a large turn-on NIR fluorescence signal. • Located in mitochondria with high colocalization coefficient. • Image endogenous and exogenous H 2 S in live cells. [ABSTRACT FROM AUTHOR]

Abstract A new simple and facile fluorescent ratiometric probe (probe 1) has been designed for the detection of cysteine (Cys). Probe 1 as the fluorophore contains a typical excited-state intramolecular proton transfer (ESIPT) dye. In probe 1 to restore the ESIPT process, the group of acrylate which acts as the recognition unit can block the ESIPT process and can be selectively achieved by Cys, which makes the probe as the ratiometric fluorescent detection for Cys in aqueous solution. This probe shows highly selectivity towards Cys over other biothiols including glutathione (GSH) and homocysteine (Hcy) because of specific cyclization between Cys and acrylate group, and having a detection limit of 42.3 nM. In addition, the experiment of cell imaging shows that probe 1 possesses low cytotoxicity and excellent cell permeability towards the living cells, and has been successfully applied to the ratiometric imaging not only for the endogenous but also for the exogenous cysteine in the living cells effectively. Graphical abstract A new simple and facile ratiometric fluorescent probe (probe 1) has been designed for detecting cysteine (Cys). Probe 1 can be synthesized by 2-(5-bromothiophen-2-yl)-3-hydroxy-chromen-4-one (compound 2) and acryloyl chloride. Probe 1 shows high selectively towards Cys due to the acrylate moiety as the recognized unit can distinguish Cys from Hcy and GSH by different reaction kinetics during the conjugate addition–cyclization reaction. The ratiometric fluorescent measurement can be achieved based on ESIPT process. To demonstrate the application of the probe 1 , in this manuscript, the probe 1 has been successfully applied to the ratiometric imaging for the intracellular and exogenous cysteine in living Hela cells. fx1 Highlights • Probe 1 synthesized by excited-state intramolecular proton transfer (ESIPT) dye. • Probe 1 shows remarkable properties including the ratio of dual emission, high selectivety and sensitivity for cys. • Probe 1 can be used not only detecting and imaging exogenous Cys but also endogenous Cys. [ABSTRACT FROM AUTHOR]

A turn-on fluorescent probe (Naphsulf-O) for hydrazine was developed by protecting the hydroxy group of the fluorophore 6-acetyl-2-hydroxynaphthalene via O-4-nitrobenzenesulfonylation, where 4-nitrobenzene was used as a fluorescence quenching moiety as well as an electrophile. Upon nucleophilic aromatic substitution (NAS) reaction of hydrazine toward the probe, the protecting group was removed and fluorophore was released. The probe exhibits a large Stokes shift, excellent selectivity and high sensitivity for hydrazine detection in aqueous solution with a detection limit of 0.716 ppb (22 nM), which is of great importance in both environmental and biological system. Furthermore, it was successfully applied to imaging of hydrazine in living cells. [ABSTRACT FROM AUTHOR]

Recently, carbon nanomaterials have received considerable attention as fluorescent probes owing to their low toxicity, water solubility and stable photochemical properties. However, the development of graphene quantum dots (GQDs) is still on its early stage. In this work, GQDs were successfully synthesized by one-step microwave assisted pyrolysis of aspartic acid (Asp) and NH 4 HCO 3 mixture. The as-prepared GQDs exhibited strongly blue fluorescence with high quantum yield up to 14%. Strong fluorescence quenching effect of Fe 3+ on GQDs can be used for its high selectivity detection among of general metal ions. The probe exhibited a wide linear response concentration range (0–50 μM) to Fe 3+ and the limit of detection (LOD) was calculated to be 0.26 μM. In addition, GQDs are also sensitive to the pH value in the range from 2 to 12 indicating a great potential as optical pH sensors. More importantly, the GQDs possess lower cellular toxicity and high photostability and can be directly used as fluorescent probes for cell imaging. [ABSTRACT FROM AUTHOR]

Precise detection of intracellular Cys will be helpful to accurately assess the physiological functions in the physiological and pathological processes. Herein, a new probe Meoeth-Cy-OBz-oCl capable of Cys sensing with high selectivity over other mercaptoamino-acid molecules including Hcy and GSH was developed. The studies on sensing mechanism supported thiols-induced SNAr substitution-rearrangement cascade reaction which allowed discriminating Cys from Hcy/GSH. And its preferential fluorescence response of Meoeth-Cy-OBz-oCl to intracellular Cys was also achieved by means of fluorescence imaging in HeLa cells. Besides, Meoeth-Cy-OBz-oCl was confirmed possessing mitochondria-targeting ability in living cells. In addition, fluorescence imaging in BALB/c mice revealed that Meoeth-Cy-OBz-oCl could visually monitor the variation of Cys in vivo. Image 1 • A novel cascade reaction-based fluorescent cyanine chemosensor for Cys-specific detection was designed and synthesized. • The probe exhibited favourable selectivity for Cys over other mercaptoamino-acid such as Hcy and GSH. • The probe was preferentially accumulated in mitochondria organelle. • The chemosensor could visually monitor the variation of Cys in BALB/c mice. [ABSTRACT FROM AUTHOR]

A facile strategy for the preparation of nitrogen and phosphorus co-doped carbon dots (N, P-CDs) with long-wavelength emission is attractively proposed in one-pot hydrothermal strategy. The resulting N, P-CDs hold exceptional optical features and display excitation wavelength-independent properties with the emission wavelength at 590 nm, which enable it with the satisfactory relative quantum yield (QY) of 15.6% in long-wavelength region. In addition, the proposed N, P-CDs demonstrates specific selectivity towards ClO− over other competitive reactive oxygen species and exhibits rapid fluorescence response time to ClO−. Moreover, the N, P-CDs exhibits low-cytotoxicity and excellent cell membrane permeability for recognizing ClO− in SMMC-7721 cells, which demonstrates their enormous potential in biological system. Image 1 • The N, P-CDs takes dye of safranine T as the precursor, which overcomes the shortcomings of high toxicity for dye molecules. • The N, P-CDs displays the satisfactory relative quantum yield (QY) in long-wavelength region. • As-prepared N, P-CDs exhibits specific selectivity towards ClO− with lower limit of detection. • Outstanding performance of N, P-CDs with superior water-solubility, high photostability and favorable biocompatibility. [ABSTRACT FROM AUTHOR]

Two probes based on tetrahydroxanthylium unit (probe 1a) and methyltetrahydroxanthylium unit (probe 1b) were designed and synthesized for the detection of hydrazine. Probes 1a–b exhibited turn-on red emission signal and high selectivity toward NH 2 NH 2. The response time of probe 1a to NH 2 NH 2 was more than 60 min, while that of probe 1b was less than 30 min. The detection limits of probes 1a–b were calculated as 210 nM and 110 nM respectively. What's more, the tolerance experiments showed that methyltetrahydroxanthylium unit possessed higher tolerance toward nucleophiles. Moreover, cells imaging experiments demonstrated that probe 1b could detect exogenous NH 2 NH 2 in living HeLa cells. Image 1 • Fluorophores based on tetrahydroxanthylium with and without methyl at the C-7 position weredesigned and synthesized for reducing the impact of nucleophiles, and they were designed as the corresponding NH 2 NH 2 probes (1a-b). • Probe 1b with red emission showed faster response time (within 30 min) and lower detection limit (110.0 nM). • Probe 1b could detect exogenous hydrazine in living HeLa cells. [ABSTRACT FROM AUTHOR]

In this study, a mitochondria-specific fluorescent probe for efficient ratiometric detection of Cys was designed and investigated. Probe 1 is composed of a xanthylene skeleton and a benzyl group containing an acryloyl moiety. The probe showed excellent water solubility, good selectivity and sensitivity toward Cys over other analytes, and afforded an extremely low detection limit of 33.7 nM. The possible detection mechanism was ascertained by HRMS analysis. Moreover, probe 1 had excellent mitochondrial-targeting ability (the Pearson's correlation coefficient was 0.96), and was capable of monitoring endogenous Cys in living HeLa cells by dual channel ratiometric bioimaging, demonstrating its significant potential in biological applications. Image 1 • A novel ratiometric and mitochondria-targetability fluorescent probe 1 with a xanthylene skeleton for Cys was developed. • Probe 1 showed excellent water solubility, high selectivity and sensitivity (detection limit of 33.7 nM) towards Cys. • Probe 1 could be successfully used for imaging cellular exogenous and endogenous Cys. [ABSTRACT FROM AUTHOR]