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Hypochlorite is a kind of endogenously produced reactive oxygen species (ROS) in the human immune system and plays a crucial role in many pathophysiological processes. In this work a novel fluorescent probe derived from 6‐methylthio coumarin was designed and synthesised for detection of hypochlorite in acetonitrile/phosphate‐buffered saline (MeCN/PBS) (1:1, v/v, pH 7.4) medium. The probe displayed high specificity toward hypochlorite over other ROS analytes, rapid response to hypochlorite within 30 s, and a broad applicable range of pH 3–8. The detection limit was calculated to be 1.48 μM. Application of this probe for in vitro Hecat cell imaging to detect hypochlorite ions was confirmed. A sensing mechanism based on thioether to sulfoxide oxidation by hypochlorite was proposed and demonstrated. The study presented an effective approach for construction of highly efficient hypochlorite chemosensors from hydrophilic methylthio‐substituted coumarins considering their facile access. [ABSTRACT FROM AUTHOR]

It is particularly important to develop effective and specific detection methods for harmful metal ions such as the silver ion (Ag+) and mercury ion (Hg2+). In this article, a new near‐infrared (NIR) fluorescent probe (N‐FP) based on intramolecular charge transfer (ICT) effect was designed and synthesised, which exhibited the characteristics of large Stokes shift (163 nm) and excellent stability. Addition of Ag+ or Hg2+ to the N‐FP solution in ethanol/water (9:1, v/v) caused remarkable enhancement of fluorescence emission at 661 nm, bathochromic shift of ultraviolet‐visible absorption wavelength, and colour change from orange to red or purple. While adding other metal ions including Li+, Na+, K+, Ag+, Cu2+, Fe2+, Zn2+, Co2+, Ni2+, Mn2+, Sr2+, Ca2+, Mg2+, Al3+, Cr3+ and Fe3+ did not bring about substantial spectral and colour change. The detection limit of the N‐FP for Ag+ and Hg2+ was calculated to be 1.1 and 0.72 μM, respectively. The N‐FP could be used to recognise Ag+ and Hg2+ in a wide pH range of 1–10. The sensing mechanism was proposed and demonstrated by proton nuclear magnetic resonance (1H‐NMR), high‐performance liquid chromatography (HPLC) and mass spectrometry (MS) measurements [ABSTRACT FROM AUTHOR]

A fluorescent probe derived from cyanine‐rhodanine conjugate was developed for dual detection of mercury (Hg2+) ion and pH. Addition of Hg2+ ion to the weakly fluorescent probe solution in dimethyl sulphoxide/water (DMSO/H2O, 7:3, v/v) induced discernible colour change and fluorescence enhancement while other metal cations including Li+, Na+, K+, Ag+, Cu2+, Fe2+, Zn2+, Co2+, Ni2+, Mn2+, Sr2+, Ca2+, Mg2+, Al3+, Cr3+ and Fe3+ did not cause obvious change in colour and fluorescence emission. The detection limit of the probe toward Hg2+ ion is 1.61 × 10−7 M. The probe also exhibited remarkable pH‐responsive effect. It acts as a dual chromogenic and spectroscopic probe for determining different pH scales over a wide range of pH 1.0–14.0: bright yellow with maximum wavelength (λmax) 416 nm for pH 1.0–2.0, orange with λmax 470 nm for pH 3.0–9.0, and pale yellow with λmax below 400 nm for pH 10.0–14.0. Plausible sensing mechanisms of the probe toward Hg2+ ion and pH have been proposed. [ABSTRACT FROM AUTHOR]

A coumarin‐based fluorescent probe containing both acrylate moiety and an allyl substituent was developed for distinguishing cysteine from homocysteine. The maximum absorption wavelength of the probe showed a bathochromic shift upon addition of cysteine and the colour changed from colourless to yellow. The maximum fluorescence emission at 462 nm of the probe was dramatically enhanced upon addition of cysteine in aqueous solution. In HEPES buffer (pH = 7.4, EtOH/H2O = 9:1, v/v), both of the fluorescence emission bands of the probe at ca. 390 and 462 nm were intensely enhanced upon the addition of cysteine, while other amino acids, namely, homocysteine, asparaginic acid, methionine, glycine, phenylalaninase, valine, tryptophan, serine, glutamic acid and glutathione, did not cause a remarkable change. The probe can be used for selectively colorimetric and ratiometric fluorescent detection of cysteine over homocysteine and other common amino acids in both organic media and aqueous solution. The concentration of cysteine can be estimated by titration of the probe in aqueous solution, and the detection limit of the probe towards cysteine was 2 μmol/L. [ABSTRACT FROM AUTHOR]

A fluorescent probe based on a simple coumarin derivative could recognise mercury ions (Hg(ii)) and thiols selectively in aqueous solution. The addition of Hg(ii) induced a blue shift of the fluorescence emission band of the probe while the fluorescence was almost quenched by the addition of p‐toluenethiol or cysteine (Cys). The detection limit of the probe towards Hg(ii) and Cys was 8 µmol/L. The probe could be used for the detection of Hg(ii) and thiols by the naked eye under ultraviolet light irradiation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fluorescent probe with dual recognition sites for Hg2+ was developed. • Addition of Hg2+ induced fluorescence enhancement of the probe by 70 fold. • The probe turned from colorless to blackish brown upon addition of Hg2+ ion. • The probe showed low LOD of 0.12 μM for sensing of Hg2+ ion. • It was used for bioimaging and determination of Hg2+ concentrations in real water samples. A novel thionocarbonate-coumarin-thiourea triad-based probe with dual recognition sites for sensing mercury (Hg2+) ion was developed. The synthesized probe possessed both fluorogenic ("off-on") and chromogenic (from colorless to blackish brown) sensing performance towards Hg2+ ions. The fluorescence intensity was increased by 70 fold after the addition of Hg2+. As expected, the probe exhibited excellent selectivity and sensitivity for Hg2+ compared to other common competitive metal ions. The fluorescence intensity of the probe improved linearly with the increase of the concentration of Hg2+ (0–40 μM). Also, the minimum limit of detection (LOD) of the synthesized probe was 0.12 μM. Considering the importance of test feasibility in the harsh environment, the developed probe was applicable for detecting Hg2+ ions over a broad working pH range of 3–11. It is reliable and qualifies for the quantitative determination of Hg2+ concentrations in actual water samples. Finally, the probe achieved the bioimaging performance of Hg2+ in living cells and plants with good biocompatibility. [ABSTRACT FROM AUTHOR]

Abstract A fluorescent and colorimetric probe L1 based on a simple coumarin derivative for detection of Hg2+ and F− ions was developed. Upon addition of Hg2+ and F− ions, L1 underwent desulfurization and desilylation, respectively, to induce marked increase in the fluorescence intensity and sharp color change from light yellow to dark purple and light brown, respectively. Probe L1 could be used for sensing and for quantitative measurement of Hg2+ and F− ions by both UV–vis and fluorescence spectra. The bifunctional probe exhibited a high selectivity over other competitive cations and anions and could be used in both organic and aqueous media over a wide pH range. Graphical Abstract A novel bifunctional fluorescent and colorimetric probe for detection of Hg2+ and F− ions was synthesized. The probe exhibited a high selectivity over other competitive cations and anions and could be used in both organic and aqueous media over a wide pH range. Unlabelled Image Highlights • A coumarin-based fluorescent and colorimetric probe for Hg2+ and F− was synthesized. • The probe can be used for quantitative measurement of Hg2+ and F− by UV–vis and fluorescence spectra. • The probe exhibited a high selectivity over other competitive cations and anions. • The probe can be used in both organic and aqueous media over a wide pH range. [ABSTRACT FROM AUTHOR]

[Display omitted] • A near-infrared fluorescent probe for sensing Cu2+ and GSH was developed. • The probe responded to Cu2+ and GSH, respectively in different medium. • The detection limit was calculated to be 37 nM for Cu2+ and 20 nM for GSH. • The sensing mechanism was verified by spectral analysis and DFT calculations. • The probe was applicable for detection of real water samples and bioimaging. A novel near-infrared Schiff base fluorescent probe was synthesized. The probe displayed medium-dependent selectivity and could specifically recognize Cu2+ in EtOH/H 2 O (9:1, v/v) while respond to glutathione (GSH) in THF/H 2 O (9:1, v/v). Addition of Cu2+ to the probe solution caused obvious fluorescence quenching and color change. The detection limit was calculated to be 37 nM. The probe could specifically detect GSH through fluorescence turn-on in THF/H 2 O (9:1, v/v) medium based on GSH-induced hydrolysis of the probe, with the detection limit as low as 20 nM. The sensing mechanism of the probe was verified by spectral analysis and density functional theory (DFT) calculations. Application of the probe to real water samples analysis and bioimaging was achieved. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fluorescence turn-on and colorimetric probe for lysine was synthesized. • The probe exhibits high specificity and good anti-interference for Lys sensing. • It emits at near-infrared region with an extremely large Stokes shift of 280 nm. • The detection limit of the probe for lysine is 0.51 μM. • The probe is applicable in a wide range of pH 4.0–10.0. A new near-infrared (NIR) fluorescent probe CL based on coumarin- dicyanoisophorone was synthesized. Addition of Lys to probe CL solution in DMF/H 2 O (9:1, v/v) medium resulted in noticeable enhancement in the intensity of the fluorescence emission at 702 nm, accompanying distinct color change from yellow to pink. While addition of other amino acids and biothiols (Gly, Hcy, GSH, Glu, Val, Tyr, Arg, Trp, Lys, His, Leu, Phe, Asp and Met) did not bring about substantial changes in both fluorescence emission and color. The detection limit was calculated to be 0.51 μM. Job's plot test revealed that probe CL and Lys formed a complex of 1:1 stoichiometry. Probe CL showed high stability and could be used to recognize Lys in a wide pH range of 4.0–10.0. The sensing mechanism was proposed and verified by 1H NMR spectral measurement. The dual-modal fluorescence turn-on and colorimetric NIR probe with an extremely large Stokes shift of 280 nm may be utilized for highly specific and practical sensing of Lys. [ABSTRACT FROM AUTHOR]

• Na-doped carbon dots (Na-CDs) was synthesized from β-CD and sodium acetate. • Na-CDs was stable in a wide pH range of 3–12. • Na-CDs served selective probe for fluorescence turn-off detection of Hg2+. • Na-CDs responded to Hg2+ rapidly within 10 min by ACQ mechanism. • Na-CDs displayed low detection limit of 34.22 nmol/L for Hg2+. Na-doped carbon dots (Na-CDs) was synthesized by hydrothermal method from β-cyclodextrin and sodium acetate. The Na-CDs was stable at pH 3–12 and after storage for a long time. The Na-CDs served fluorescence sensor for highly selective detection of Hg2+ in aqueous medium with a detection limit of 34.22 nM. The sensing mechanism was based on the aggregation caused fluorescence quenching. The Na-CDs displayed high selectivity and sensitivity towards Hg2+, which supplied a new idea for constructing CDs-based stable fluorescent probes and a novel platform for selective Hg2+ detection. [ABSTRACT FROM AUTHOR]

A new NIR probe based on coumarin-dicyanooxanone dyad an extraordinarily large Stokes shift of 316 nm was developed for simultaneous fluorescence turn-on and colorimetric detection of Hg2+ and Ag+ in aqueous solution. Its application for in vitro U87MG cell imaging to detect Hg2+ was confirmed. [Display omitted] • A coumarin-dicyanooxanone dyad-based NIR fluorescent probe was synthesized. • • The probe displayed an extraordinarily large Stokes shift of 316 nm. • • It serves as colorimetric and fluorimetric probe for detection of Hg2+ and Ag+. • • The applicable pH for sensing Hg2+ by the probe is in a range of 2–12. • • Application of the probe for in vitro cell imaging to detect Hg2+ was confirmed. A new near-infrared (NIR) probe based on a coumarinyl ligand (CL) was designed and synthesized. The probe CL can be used for simultaneous fluorescent turn-on and colorimetric detection of Hg2+ and Ag+ in ethanol/water medium. Colorless solution of probe CL changed to light yellow or dark yellow after addition of Hg2+ or Ag+ ions. Meanwhile the maximum absorption band shifted from 379 nm to 404 nm and the intensity increased enormously (for Hg2+) or moderately (for Ag+). Probe CL displayed an extraordinarily large Stokes shift of 316 nm and addition of Hg2+ or Ag+ to probe CL induced enhancement in the intensity of fluorescence emission at 695 nm by 15 or 8 fold. The detection limit of CL for Hg2+ and Ag+ ions is 0.83 and 8.8 μM, respectively. The applicable pH for sensing Hg2+ by probe CL is in a broad range of 2–12. Application of probe CL for in vitro U87MG cell imaging to detect Hg2+ ions was confirmed. [ABSTRACT FROM AUTHOR]

Fluorescence detection of heavy metals is considered to be a very promising method. A novel fluorescent probe NIFP with large Stokes shift (130 nm) was synthesized for the detection of silver (Ⅰ) and mercury (II) ions. The probe NIFP was able to specifically identify silver (Ⅰ) and mercury (II) ions in ethanol by absorption and fluorescence emission spectra. Upon addition of silver (Ⅰ) and mercury (II) ions, the fluorescence intensity of NIFP at 570 nm increases greatly and the absorption and emission wavelengths change significantly. In addition, NIFP has good stability for the recognition of silver (Ⅰ) and mercury (II) ions in the presence of interfering ions (Li+, Na+, K+, Cu2+, Fe2+, Zn2+, Co2+, Ni2+, Mn2+, Sr2+, Ca2+, Mg2+, Al3+, Cr3+, Fe3+). NIFP has low detection limits for the identification of silver (Ⅰ) and mercury (II) ions and is capable of detecting mercury (II) ions over a wide range of pH values. • A novel fluorescent probe with large Stokes shift of 130 nm was synthesized. • The probe can be used to detect silver (I) and mercury (II) ions in ethanol. • The probe shows low detection limits for sensing of silver (I) and mercury (II) ions. • The probe is capable of detecting mercury (II) ions over a wide range of pH values. [ABSTRACT FROM AUTHOR]

A fluorescent sensor based on coumarin-maleimide conjugate was developed for efficient discrimination of Cys from Hcy and GSH in both organic and aqueous solution. Addition of Cys to the non-fluorescent sensor solution in DMF induced bright blue fluorescence and enhanced the fluorescence intensity by 320-fold while other amino acids and biothiols (Gly, Hcy, GSH, Glu, Val, Tyr, Arg, Trp, Lys, His, Leu, Phe, Asp and Met) did not bring about remarked change. The sensor responds to Cys extremely rapidly. If Cys was added to the sensor solution, the fluorescence intensity increased by 170-fold immediately and attained the maximum value in 5 min. A linear relationship was observed between Cys concentration within 2–20 μM and the fluorescence intensity of the sensor solution. The detection limit of the sensor toward Cys is as low as 4.7 nM. The sensor is also effective for specific detection of Cys in aqueous (DMF/H 2 O = 9:1, v/v) solution. Practical application of the sensor to drug analysis and bioimaging of living Hela cells has been verified. Possible sensing mechanism of the sensor toward Cys has been proposed. A coumarin-maleimide conjugate was synthesized for fluorescence turn-on discriminating Cys from Hcy and GSH in both organic and aqueous media. The sensor is superior in respect of its low LOD (4.7 nM), rapid response (several sec‒5 min), extraordinary fluorescence enhancement (320-fold), and facile synthesis and is applicable in drug analysis and bioimaging of living cells. [Display omitted] • A coumarin-maleimide conjugate-based fluorescent sensor was synthesized facilely. • The sensor can discriminate Cys from Hcy and GSH in both organic and aqueous media. • The sensor shows low LOD of 4.7 nM and rapid response (less than 5 min) in DMF. • Addition of Cys induces fluorescence enhancement by 320-fold in DMF. • The sensor is applicable in drug analysis and bioimaging of living cells. [ABSTRACT FROM AUTHOR]