Search

A new structurally simple fluorescent CP probe based on chromone was designed and synthesized, and its structure was fully characterized using various analytical techniques. The CP probe displays a high selectivity and sensitivity for sensing Fe3+ with a "turn-off" fluorescence response over other metal ions in a DMSO/H2O (4:1, v/v) solution. The experiment results show that the CP probe is stable over a wide pH range of 2.0–12.0. The detection limit for Fe3+ was calculated to be 0.044 μmol•L−1. The molar ratio method indicated that the binding mode between the CP probe and Fe3+ is a 1:1 complex formation. HR-MS and density functional theory (DFT) calculations were also performed to further confirm the recognition mechanism. Both fluorescence imaging experiments and the MTT assay demonstrated that the CP probe was suitable for detecting intracellular Fe3+ and no significant cytotoxicity in living cells. [ABSTRACT FROM AUTHOR]

Organic fluorophores with dual-state emission (DSE) are rare or difficult to observe because most of them display either aggregation-induced emission (AIE) or aggregation-caused quenching (ACQ). Amazing works have been accomplished, yet most of the DSE compounds were excited by UV light which limits their wide application in bioimaging. In this work, we achieved a visible-light excited DSE fluorophore and realized its imaging in SKOV-3 cells and zebrafish. The naphtho[2',3':4,5]imidazo[1,2-a]pyridine (NIP) core ensures its emission in dilute solution. Meanwhile, the twisted phenyl ring blocks fluorescence quenching induced by the π-π stacking and leads to the emission of the solid. The fluorescence intensity is steady even after 6 h of continuous intense sunlight. More importantly, photostability of NIP in cells is much better than commercial dye (mitochondrial green). [ABSTRACT FROM AUTHOR]

New portable hydrogel sensors for Al3+ and Fe3+ detection were designed based on the aggregation-induced emission (AIE) and color change of N-doped carbon dots (N-CDs). N-CDs with yellow fluorescence were prepared by a one-pot hydrothermal method from 2,5-dihydroxyterephthalic acid and acrylamide. The fluorescence of N-CDs was enhanced by Al3+ about 20 times and quenched by Fe3+. It was interesting that although Fe3+ showed obvious quenching on the fluorescence of N-CDs it did not cause a noticeable change in the fluorescence of N-CDs + Al3+. The colorless solution of N-CDs appeared blue in the presence of Fe3+ without the influence of Al3+. Therefore, the turn-on fluorometry and colorimetry systems based on N-CDs were constructed for the simultaneous detection of Al3+ and Fe3+. Furthermore, the portable sensing of Al3+ and Fe3+ was realized with the assistance of hydrogel, filter paper, cellulose acetate, and cellulose nitrate film. The proposed approach was successfully applied to the detection of Al3+ and Fe3+ in food samples and cell imaging. [ABSTRACT FROM AUTHOR]

Fluorescent probes are intriguing material for ion detection. In this study, 4,4-difluoro-4-bora3a,4a-diaza-s-indacene (BODIPY) containing a dipicolylethylenediamine unit was developed as a colorimetric and fluorescence "turn-off" probe for Cu2+. The probe exhibited higher selectivity for Cu2+ than other common metal ions with a detection limit of 8.49 μM. With increasing Cu2+ concentration, the probe showed a red-shift in the absorption spectrum as well as fluorescence quenching, possibly due to the intramolecular charge transfer effect of the probe–Cu(II) complex. Furthermore, the probe was used for imaging Cu2+ in living cells based on confocal fluorescence imaging. The results show that the probe is an effective tool for detection copper ions. [ABSTRACT FROM AUTHOR]

In this research, DNA-modified carbon dots (CDs) were exploited to construct a fluorescence assay for breast cancer genes (BRCA1, a potential marker for cancer diagnosis) detection. For this purpose, water-soluble synthesized CDs were functionalized with 19 mer-modified oligonucleotides (capture probe). By adding the DNA target, the specific binding between the DNA probe and DNA target causes fluorescence quenching. The assay displayed a fine capability of sensing the BRCA1 gene with a linear range (R2 = 0.9918) of 36 attomolar (aM) to 532 femtomolar (fM) and a detection limit of 2 attomolar. This homogeneous process does not need additional separation and washing steps of un-hybridized DNA. To assess the selectivity, the prepared biosensor responses were evaluated in solutions containing single-base mismatched DNA sequences, three-base mismatched DNA sequences, or non-complementary DNA sequences, separately. To demonstrate the practical application of the designed biosensor, the extracted DNA from blood samples of breast cancer patients was utilized as real samples. When the CDs-DNA bioassay was exploited in the imaging of MCF-7 cancer cells, strong fluorescence emission was observed. After incubation times, both the cells' size and shape remained unchanged. The results validated that the CDs are an extremely great bioimaging candidate in disease diagnosis, biomedicine investigation, and managing cancer diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] Carbon dots (CDs) have been widely used in recent years because of their excellent water solubility and abundant surface functional groups. However, compared with quantum dots or biological probes, the quantum yield of CDs is lower, and the fluorescence mainly concentrated in the blue-green range, which significantly limits the biological applications of CDs. Heteroatoms doping is the most common method to improve the luminescence of CDs. In this work, nitrogen and sulfur co-doped luminescent CDs were successfully synthesized by microwave assisted method using glutathione (GSH) and p-phenylenediamine (PPD) as raw materials. It can emit bright green fluorescence in ethanol solution, and the maximum emission wavelength is 535 nm when excited at 374 nm, and the absolute quantum yield is as high as 63%. Iron ion (Fe3+) can interact with the functional groups on the surface of the CDs to form CDs/Fe3+, which is a non-fluorescence complex, and Fe3+ can be reduced to ferrous ion (Fe2+). In other words, the reaction mechanism of CDs and Fe3+ is a combination of dynamic quenching and static quenching. The fluorescence of CDs quenched by Fe3+ can be restored by thiol, because there is a stronger binding force between sulfhydryl (-SH) on the surface of thiol and Fe3+, which enables CDs to be released. In addition, the CDs has good biocompatibility and stability, indicating that it has excellent potential in bioimaging. This discovery will expand the application of CDs in the fields of biosensing and imaging. [ABSTRACT FROM AUTHOR]

A label-free fluorescence sensor based on near-infrared carbon dots (NIR-CDs) and aptamer is described for the highly sensitive and selective detection of ciprofloxacin (CIP). NIR-CDs were synthesized from polyethyleneimine and reduced glutathione by one-step hydrothermal method. The electrostatic interaction between the positively charged carbon dots and the negatively charged aptamer resulted in fluorescence quenching. After the addition of CIP, the specific binding between CIP aptamer and CIP was stronger, resulting in fluorescence recovery. Under the optimal experimental conditions, the recovered fluorescence intensity has a linear relationship with the concentration of CIP in the range 0.5–800 ng/mL, and the detection limit is 0.167 ng/mL. The prepared carbon dots have excellent optical properties and biocompatibility, and due to their emission characteristics in the near-infrared window, they can be used for biological imaging, which has also been confirmed in the experiment. The feasibility of the label-free fluorescence sensor for the detection of CIP is also proved by confocal fluorescence imaging. The detection results of CIP determination in milk by this sensor are satisfactory, indicating that the developed sensor has great application potential. [ABSTRACT FROM AUTHOR]

In this work, arginine functionalized niobium carbide MXene quantum dots (arginine-Nb 2 C MQDs) were synthesized using Nb 2 AlC, NaOH and arginine as reagents. The as-synthesized probe showed bluish-green fluorescence under UV light at 365 nm. The structural and morphological changes of as-synthesized arginine-Nb 2 C MQDs were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Raman spectroscopy and high-resolution transmittance electron microscopy (HR-TEM). The synthesized fluorescent arginine-Nb 2 C MQDs were stable, with an average size of 1.92 ± 0.52 nm. As-synthesized arginine-Nb 2 C MQDs act as a sensor for detecting superoxide anion (O 2 •−) via a fluorescence "turn-off" mechanism with the detection limit of 31.89 nM. The fluorescence of arginine-Nb 2 C MQDs is quenched by O 2 •− via dynamic fluorescence quenching mechanism. Fascinatingly, the synthesized arginine-Nb 2 C MQDs showed negligible cytotoxicity on HeLa cells and acted as promising candidates for sensing of O 2 •− in Saccharomyces cerevisiae cells. [Display omitted] • HF-free synthetic strategy was used for the fabrication of arginine-Nb 2 C MQDs. • Arginine-Nb 2 C MQDs act as a fluorescent sensor for selective detection of O 2 •−. • The developed approach exhibited an impressive detection limit of 31.89 nM for O 2 •−. • Arginine-Nb 2 C MQDs served as probe for cell imaging with minimal cytotoxicity. • The developed technique was used to determine O 2 •− in environmental samples. [ABSTRACT FROM AUTHOR]

Telomerase (TE) is a promising diagnostic and prognostic biomarker for many cancers. Quantification of TE activity in living cells is of great significance in biomedical and clinical research. Conventional fluorescence-based sensors for quantification of intracellular TE may suffer from problems of fast photobleaching and auto-fluorescence of some endogenous molecules, and hence are liable to produce false negative or positive results. To address this issue, a fluorescence-SERS dual-signal nano-system for real-time imaging of intracellular TE was designed by functionalizing a bimetallic Au@Ag nanostructure with 4- p -mercaptobenzoic acid (internal standard SERS tag) and a DNA hybrid complex consisted of a telomerase primer strand and its partially complimentary strand modified with Rhodamine 6G. The bimetallic Au@Ag nanostructure serves as an excellent SERS-enhancing and fluorescence-quenching substrate. Intracellular TE will trigger the extension of the primer strand and cause the shedding of Rhodamine 6G-modified complimentary strand from the nano-system through intramolecular DNA strand displacement, resulting in the recovery of the fluorescence of Rhodamine 6G and decrease in its SERS signal. Both the fluorescence of R6G and the ratio between the SERS signals of 4- p -mercaptobenzoic acid and Rhodamine 6G can be used for in situ imaging of intracellular TE. Experimental results showed that the proposed nano-system was featured with low background, excellent cell internalization efficiency, good biocompatibility, high sensitivity, good selectivity, and robustness to false positive results. It can be used to distinguish cancer cells from normal ones, identify different types of cancer cells, as well as perform absolute quantification of intracellular TE, which endows it with great potential in clinical diagnosis, target therapy and prognosis of cancer patients. [Display omitted] • A dual-signal nanosensor was developed for imaging of telomerase in living cells. • Au@Ag nanoparticles served as fluorescence quenching and SERS enhancing substrate. • The results of the fluorescence and SERS channels can provide mutual confirmation. • The SERS channel of the nanosensor can help identify false positive results. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) have demonstrated considerable potential for use in sensing and bioimaging applications based on their unique intrinsic properties. However, CDs have typically been used as fluorescence sensors, as opposed to indicators, based on their ultraviolet absorption and discoloration performance. In this study, orange red-emitting CDs with a high quantum yield (QY) of 53% were constructed from 2,3-diaminopyridine via solvothermal synthesis. Different from the fluorescence quenching behavior reported previously, the constructed CDs demonstrated a unique character in their ultraviolet absorption and fluorescence emission in the presence of Fe3+. The color of the CD solution varied from mauve to orange following the addition of Fe3+ at concentrations exceeding 1 μM, which enabled these CDs to be used in the determination of the presence of Fe3+ in lake water. In addition, due to their negligible cytotoxicity, good solubility, and adequate dispersity, an outstanding cellular probe with near-infrared fluorescence was established. Overall, this study presents a unique CD-based sensor, details its fluorescence mechanism, visual colorimetry, and ultraviolet absorption variations, and confirms its applicability in near-infrared cellular imaging and environmental analyses. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel dual-functional probe FAM-SSH was fabricated for fluorescence and colorimetric detection of Cu2+ and S2− ions. • FAM-SSH exhibited a wide linear range and a lower detection limit towards Cu2+ (55.5 nM) and S2− (31.1 nM). • FAM-SSH was successfully used to determine Cu2+ and S2− in real samples with good recovery rate and accuracy. • FAM-SSH was successfully applied for semi-quantitative detection of Cu2+ and S2− with the aid of smartphone APP and test strips. • FAM-SSH was found useful for imaging of Cu2+ and S2− in living cells. A new dual-mode probe FAM-SSH with fluorescence and colorimetric properties was developed by solid-phase peptide synthesis, comprising 5-carboxy fluorescein (5-FAM) as a fluorophore, and tripeptide (Ser-Ser-His) as a recognition group. FAM-SSH not only displayed highly selective detection of Cu2+ based on fluorescence quenching mode, but also achieved colorimetric recognition of Cu2+ in solution, wherein a color change was observable to the naked eye. Additionally, the FAM-SSH -Cu2+ ensemble was highly selective for S2− over a wide pH range (7.0–12.0), characterized by a fluorescence enhanced response and colorimetric recognition, which was caused by the release of FAM-SSH and the precipitation of CuS. Moreover, the limit of detection (LOD) values for Cu2+ and S2− were 55.5 nM and 31.1 nM, respectively. Results of sample analyses and cell imaging experiments indicated that FAM-SSH has exciting field practicability and good cell permeability, and would be further useful for detection and imaging in environmental systems and living cells. Finally, test strips were produced by immersing them in FAM-SSH solution, thereby creating a method for portable visual detection. More importantly, a smartphone-assisted visual sensing platform was also developed for semi-quantitative Cu2+ and S2− detection with LOD values of 0.48 μM and 1.22 μM, respectively. [ABSTRACT FROM AUTHOR]

Synthesis of photoluminescence carbon dots from red beetroot and utilizing its extract for spectrofluorimetric determination of tenoxicam. [Display omitted] • Photoluminescence carbon dots were synthesized for the first time from red beetroot. • The fluorescence intensity of the carbon dots was quenched by adding tenoxicam. • The acetonitrile extract of red beetroot exhibits fluorescence activity. • The fluorescence intensity of the extract was enhanced by adding tenoxicam. • The developed methods were applied to determine tenoxicam in different dosage forms. Tenoxicam (TNX) belongs to non-steroidal drugs that effectively treat many inflammatory disorders. In this study, luminescent carbon dots were synthesized from red beetroot as a green fluorescence probe. The synthesized carbon dots' morphology, size, and spectroscopic features were investigated and characterized by spectrophotometric, FTIR, SEM, spectrofluorimetric, and TEM techniques. The synthesized carbon dots possessed an emission at 430 nm and an excitation at 366.5 nm. Meanwhile, TNX is a yellow-colored compound with a spectrophotometric absorbance peak at 370 nm. Based on the inner filter effect mechanism, the emission fluorescence intensity of the synthesized carbon dots has been markedly quenched upon the addition of TNX. In addition, the quenching in the fluorescence intensity was quantitively related to the concentration of TNX at the linear range of 0.25 - 2.5 µg/mL (r2 = 0.9989) with a LOD of 0.08 µg/mL and LOQ of 0.24 µg/mL. The second side of this study is based on enhancing the fluorescence intensity of the acetonitrile extract of red beetroot upon the addition of TNX solution. This enhancement was recorded at a fluorescence emission of 357 nm with a fluorescence excitation of 305.5 nm. In addition, the enhancement in the fluorescence intensity was quantitively related to the concentration of TNX at the linear range of 0.5 - 8.0 µg/mL (r2 = 0.9995) with a LOD of 0.16 µg/mL and LOQ of 0.49 µg/mL. The analytical conditions were well-optimized, and the developed method was validated according to ICH guidelines. Finally, the proposed spectrofluorimetric approaches were applied to determine TNX in vials, tablets, and capsules with good recovery and accepted statistical results. [ABSTRACT FROM AUTHOR]

Intracellular viscosity is closely related to a series of biological processes and could be a biomarker for various diseases. Herein, we reported a deep-red emission viscosity probe ACI, which showed a turn-on fluorescence effect with excellent selectivity encountering high viscous medium. To assure the practical biological application, ACI demonstrated not only a long wavelength emission at 634 nm but also a long wavelength excitation at 566 nm, which were crucial to afford deeper penetration depth and higher sensitivity in bioimaging. The photophysical properties and viscosity recognition mechanism of the probe were carefully discussed here. Theoretical calculations furtherly confirmed that high viscous medium could inhibit the twisted intramolecular charge transfer (TICT) process of the probe which quenched the fluorescence in low viscous media, and restore the emission. More importantly, it was successfully applied to visualize the viscosity in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] Two new heptamethine cyanine dye–fullerene C 60 covalently- linked dyads, which absorb in far-red and NIR spectral regions, have been synthesized by esterification click reaction and characterized by physicochemical methods. No significant fluorescence quenching was found due to weak electronic coupling between heptamethine moiety and fullerene core, which was confirmed by photophysical and electrochemical methods. Such dyads can be useful for cell imaging and fluorescence diagnostics of various fullerene derivatives. [ABSTRACT FROM AUTHOR]

Nitro groups with a strong electron-withdrawing effect can powerfully influence the fluorescence of fluorophores. In this work, through adjusting the nitro group at the HBT fluorophore to construct a phenylhydrazone structure, two probes (HBTN and HBTH) were synthesized to detect OCl−. Consequently, HBTN with the nitro group quenched the fluorescence of HBT and HBTH without the nitro group causing a redshift of the fluorescence, which resulted in enhanced and ratiometric fluorescence signal changes during the detection process. Among them, HBTN shows good ability to selectively detect OCl− in the concentration range of 0–14 μM with the detection limit of 2.06 nM. Based on HBTN, a portable test strip for detecting OCl− was made for the convenient quantification of the OCl− concentration with a spectrophotometer, and exogenous and endogenous OCl− was successfully imaged in cells. [ABSTRACT FROM AUTHOR]

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]

[Display omitted] • The sensor is highly sensitive and selective to Hg2+ with low detection limit. • The sensor provides five cycles–reversibility for Hg2+ detection. • The sensor offers a very large Stokes shift of 192 nm. • The sensor enables for quick screening of Hg2+ in water and cosmetic samples. • Application in the potential Hg2+–accumulated human cells is demonstrated. Mercury pollution and its toxicity pose a grave threat to health. Therefore, developing new approaches for detecting mercury ions (Hg2+) in environmental and biological samples is crucial. Herein, a novel [5]helicene-based fluorescence sensor (M201NHP) was designed and synthesized for rapid, sensitive and specific detection of Hg2+. The sensor exhibits fluorescence quenching with a very large Stokes shift (192 nm) towards Hg2+ in aqueous acetonitrile media. The detection limit of the sensor is estimated to be 1.94 ppb, which is lower than the U.S. EPA specification for the maximum Hg2+ level in drinking water. Moreover, M201NHP offers five cycles of reversibility upon competitive chelation of cysteine. The sensor can also screen for Hg2+ contamination in real water samples and skincare products. Additionally, it can track Hg2+ in potential mercury-accumulated human cell lines derived from brain tumours, embryonic kidneys, skin and liver cancers with low cytotoxicity. These results indicate that M201NHP is a promising Hg2+ sensor that can prevent health risks and environmental impacts caused by mercury pollution. [ABSTRACT FROM AUTHOR]

An acid‐treated, oxidized graphitic carbon nitride nanosheets (g‐C3N4 NSs) was successfully synthesized and applied as a fluorescence probe for the detection of hemin based on the inner filter effect (IFE). The results indicated that the fluorescence quenching of g‐C3N4 NSs caused by hemin was attributed to the overlap between absorption spectrum of hemin and emission spectrum of g‐C3N4 NSs. It is confirmed that the g‐C3N4 NSs exhibited a highly sensitive and selective for detection of hemin. Under the optical condition, the fluorescence changing of g‐C3N4 NSs is related to the concentration of hemin ranging from 0.5 – 25 μM with a detection limit of 0.15 μM. Moreover, the fluorescence probe has been successfully applied to detect hemin in human blood. Overall, a novel and efficient fluorescence‐based method was developed supported by g‐C3N4 NSs, which is a promising material for application in sensing and cell imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • Blue emissive pyridinic- N -rich carbon dots (NCDs) were synthesized from l -malic acid and urea. • Selective and sensitive detection of diethyl chlorophosphate (DCP), a nerve agent mimic. • Inner filter effect (IFE) mediated fluorescence quenching. • Multicolor cell imaging. Fluorometric sensors for the detection of nerve agent mimics have received a lot of interest nowadays due to their high sensitivity and selectivity, ease of operation, and real-time monitoring. Pyridinic- N -rich carbon dots (NCDs) prepared through microwave-assisted pyrolysis of l -Malic acid and urea have been explored first time in this work as a novel turn-off fluorescent probe for the sensitive and selective detection of diethyl chlorophosphate (DCP), a nerve agent mimic. The as-prepared carbon dots contained a large amount of pyridinic nitrogen on their surface, which can modulate the photoluminescence properties of the NCDs. The blue emissive NCDs possessed both excitation wavelength-dependent and independent emission behavior. The detection of DCP was premised on quenching of the fluorescence emission intensity of NCDs in the presence of similar chemical reagents (e.g., trimethyl phosphate, triethyl phosphate, triethyl phosphonoacetate, triphenyl phosphate, diphenyl phosphate, tributyl phosphate). Fluorescence quenching of the NCDs in the presence of DCP has been attributed to the inner filter effect (IFE). From the linear Stern-Volmer plot (R2 = 0.9992), the limit of detection (LOD) was found to be 84 μM for sensing DCP for the concentration ranging between 3 and 15 mM. The biocompatibility of NCDs was assessed through cytotoxicity assay on MDA-MB-231 breast cancer cells. Fluorescence imaging demonstrated that NCDs have low cytotoxicity and can be employed successfully in cell imaging. [ABSTRACT FROM AUTHOR]

A novel coumarin chemosensor, 7-hydroxy-2-oxo-N-(pyridin-2-ylmethyl)chromene-3-carboxamide (Probe 1) , demonstrated significant selectivity towards Fe 3+ ions. Probe 1 exhibited high fluorescence emission profile at 447 nm, excellent selectivity towards Fe 3+ over other biologically important metal ions (Al 3+ , Ba 2+ , Co 2+ , Cu 2+ , Zn 2+ , Cd 2+ , Hg 2+ , Pb 2+ and Sn 2+ ). Interestingly, there was ~ 30-fold decrease in fluorescence intensity upon Fe 3+ binding. The limit of detection of Fe 3+ was found to be 0.76 μM (~ 40 ppb). Probe 1 also exhibited high potential as an intracellular chemosensor for Fe 3+ . [ABSTRACT FROM AUTHOR]

In this paper, a novel fluorescent probe HBT-H based on benzothiazole has been designed and synthesized. The probe has excellent selectivity and can be used for specific detection of Cu2+. Under 360 nm UV excitation, the probe HBT-H itself has a fluorescence emission peak at 487 nm, emitting cyan blue fluorescence, fluorescence quenching after added Cu2+. The detection limit of Cu2+ recognition by HBT-H probe was calculated as 3.08 × 10−7 M. According to Job's plot and high resolution mass spectrometry, the complexation ratio of HBT-H to Cu2+ was 2:1. The sensor mechanism was confirmed as excited intramolecular proton transfer (ESIPT). Surprisingly, the probe HBT-H system responded well to pH, showing green fluorescence under acidic conditions and cyan blue fluorescence under alkaline conditions. In addition, the probe HBT-H has excellent membrane permeability and low cytotoxicity, which could not only detect Cu2+ in actual water samples, but also recognize Cu2+ in human breast cancer cells (MCF-7). [Display omitted] • The probe could selectively detect Cu2+ from solutions or water samples. • The detection limit of Cu2+ with this probe was as low as 3.08 × 10−7 M. • The probe could be used to judge the acid-base properties colorimetrically. • The probe was successfully applied to the imaging of human breast cancer cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • TPA-alk is a simple, fluorescent, and biocompatible probe which could synthesized in couple of steps using triphenylamine. • The sensing of Hg2+ using TPA-alk is via oxymercuration-demercuration. • TPA-alk displayed high selectivity, distinctive fluorescence quenching, and spectral changes against mercury (II) ions over fifteen different competitive metal ions. • TPA-alk could penetrate through the cell membrane and is capable of detecting Hg2+ in a biological environment at the micromolar level. Here, we report vinyl substituted triphenylamine (TPA-alk) fluorescent probe for the rapid and efficient detection of mercury ion (Hg2+) in water and biological environment. TPA-alk detects Hg2+ selectively over a wide range of competitive metal ions with a blue shift of 43 nm in the UV absorbance spectrum. The detection limit is found to be 0.146 µM (29.2 ppb) with high selectivity over a wide range of competitive metal ions. DFT study explains the blue shift in the UV–vis absorption band of the optical probe upon the addition of Hg2+. Cell viability assay illustrates that the probe is biocompatible and it has low cytotoxicity even at its higher concentration. Cell imaging studies demonstrate the efficiency of the TPA-alk probe for the micromolar detection of mercury (II) in live BMG1 cells. [ABSTRACT FROM AUTHOR]

Realizing highly efficient emission of organic fluorophores in both solution and solid state still represents a challenging task, due to either aggregation-caused quenching (ACQ, requiring relatively low working concentration) or aggregation-induced emission (AIE, requiring relatively high working concentration). Herein, we report a highly efficient fluorophore consisting of a pyrido [1,2- a ]benzimidazole core and a simple twisted phenyl substituent. The planarity of pyrido [1,2- a ]benzimidazole ensures the conjugation thus achieving strong emission in dilute solution (quantum yield: 94.4%). Meanwhile, the π-π stacking induced fluorescence quenching is blocked by the twisted phenyl ring, which leads to efficient emission in the solid state (quantum yield: 95.2%). The compound exhibits high photostability as evidenced by minimal loss of the fluorescence even after 6 h of continuous irradiation in air. More importantly, SKOV-3 cell imaging and anti-counterfeiting application have been realized by using this fluorophore at very different concentrations. Such "twisted structure" design would open new possibilities for development of high-efficiency robust organic fluorophores that can function under a wide range of conditions. [Display omitted] • A highly efficient and photostable organic fluorophore was developed using a simple "twisted structure" design. • The fluorophore shows bright emission in both solution (QY = 94.4%) and solid state (QY = 95.2%). • SKOV-3 cell imaging and anti-counterfeiting application have been realized by at very different concentrations. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel aggregation-induced emission active chemosensor has been developed. • The sensor could detect Cu2+ and S2− with low detection limit (34.6 nM and 1.15 μM, respectively) in an almost neat aqueous solution. • The sensor has been successfully applied to imaging of Cu2+ and S2− in living cells and zebrafish. A simple reversible fluorescent chemosensor 1 was constructed using a coumarin backbone, which displayed notable aggregation-induced emission. Particularly, Cu2+ could selectively and sensitively induce fluorescence quenching of sensor 1 in an almost neat aqueous solution. Furthermore, addition of S2− to 1 -Cu2+ system could specifically restore the fluorescence emission of 1 by snatching Cu2+ ion from its complex. The detection limits of sensor 1 towards Cu2+ and S2− were 34.6 nM and 1.15 μM, respectively. Notably, sensor 1 was successfully applied to detect Cu2+ and S2− in living cells and zebrafish owing to its remarkable fluorescence behavior and low cytotoxicity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Most recent development of fluorescence sensing for biochemical molecules are presented. • Biochemical assays based on fluorescence technique are classified to "turn-off" and "turn-on". • Probable mechanisms of fluorescence are summarized and discussed how to differentiate the quenching/enhancement mechanisms. Fluorescence materials have received much attention in scientific studies because of their potential uses in cell imaging, photonic devices, and sensors. Sensors based on the combination of fluorescence techniques with various luminescent nanomaterials have recently been developed for the selective and sensitive sensing of biochemical molecules with these nanoparticles. This review provides a summary of the most recent applications of fluorescence-based analytical techniques. Downshifting and upconversion procedures are discussed to briefly introduce the principles underlying the luminescence of a material. Following that, the most recent findings (2019–2022) on the applications of fluorescence techniques for analytical assays are presented, along with a classification of "turn-off" and "turn-on" approaches. In addition, we discussed how to differentiate the fluorescence quenching/enhancement mechanisms using unique spectroscopy techniques. [ABSTRACT FROM AUTHOR]

Copper (II) is one of the most important metal ions for the human body that act as a catalytic cofactor for many metalloenzymes and proteins, and its homeostasis disruption could lead to many neurological diseases. The reported probes for Cu (II) determination are mostly based on fluorescence quenching mechanism, which provides low precision and reliability. In the present work, a turn-on fluorescence probe, (Z)-1-[2-oxo-2-[2-[1-oxoaceanthrylen-2 (1 H)-ylidene]hydrazinyl]ethyl]-pyridinium (OAHP), for highly selective detection of Cu2+ was developed. Hydrazide moiety of OAHP quenches probe fluorescence; however, upon its reaction with Cu, oxidative cleavage of the hydrazide moiety and intramolecular cyclization occurs, forming oxadiazole derivative with strong fluorescent properties. In this context, OAHP displayed significant fluorescence enhancement with increasing levels of Cu2+. OAHP could detect Cu2+ selectively with a detection limit of 18 nM (1.1 ppb). This is the first report for a probe that uses the ability of Cu2+ to induce oxidative decomposition of hydrazide with intramolecular cyclization, and it showed exceptional selective performance and exquisite sensitivity. Next, the method was applied successfully for monitoring Cu2+ in tap water samples with good accuracy (found% of 95.8–101.5%) and precisions (RSD<10%). Finally, OAHP was successfully applied for imaging Cu2+ in living cells, and this result indicates the potential of OAHP for selective detection of Cu2+ in complicated matrices. [Display omitted] • OAHP, a hydrazide derivative of phenanthrenequinone, was successfully used as a turn-on fluorescence probe for Cu2+. • Cu2+ induces oxidative cleavage of the hydrazide moiety and intramolecular cyclization forming oxadiazole derivative. • OAHP showed excellent selectivity to Cu2+ even vs. Cu+. • The new probe could detect Cu2+ selectively with sensitivity down to 1.1 ppb in tap water. • OAHP was successfully applied for imaging Cu2+ in Hep G2 cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel colorimetric and fluorescent chemosensor based on diaminopyrimidine (DAPCS) was designed and synthesized. • DAPCS was applied for the highly selective and ultra-sensitive detection of Cu2+ ion in aqueous media and living cell. • The probe DAPCS for Cu2+ showed a linear correlation, and LOD was calculated as 0.014 µM. • DAPCS-based test strips were fabricated and applied to the detection of Cu2+ ions in solutions. In this paper, a new and effective diaminopyrimidine-based chemosensor (DAPCS) was developed for the highly selective and ultra-sensitive detection of Cu2+ ion in aqueous media and living cell. Characterization and structure determining of DAPCS was determined by UV–Vis, FTIR and NMR analyses. It is observed that DAPCS and Cu (II) forms a ligand to metal charge transfer (LMCT) complex which produces distinguishable red color. The results also indicate that the DAPCS easily interacts with Cu2+ ion to form a 1:1 stoichiometry complex (DAPCS -Cu2+), resulting in a bathochromic shift in absorption maximum (429 nm to 449 nm) and remarkable quenching fluorescence intensity at the wavelength of 501 nm in DMSO-H 2 O solution. Furthermore, the detection limit of DAPCS towards Cu2+ was calculated to be 3.19 µM. Meanwhile, DAPCS was applied as fluorescent probe for detection of Cu2+ ions with the detection limit of 0.014 µM. The optimal pH range of probe DAPCS for quantitative analysis of Cu2+ ions was 9–11, which renders it suitable for detection of Cu2+ under physiological conditions. Additionally, the DAPCS could be applied to detect Cu2+ in real water samples and in HeLa cells, indicating the practical uses of DAPCS in real analyses. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new BODIPY derivative 1 behaves as an “on–off” fluorescent sensor of Cu2+. [•] Complex 1·Cu 2+ displays “off–on” fluorescent spectral response to biothiols and S2−. [•] 1·Cu 2+ complex can better recognize glutathione compared with cysteine and homocysteine. [•] 1 exhibits high sensitivity for Cu2+ under physiological conditions and in living cells. [•] 1 can locates in lysosome used as fluorescent dye in cell imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • The probe was designed and synthesized based on a rhodol derivate anchored with the 2,4-dinitrophenyl group. • The fluorescent response was fast within 12 min and a dramatic color change (from colorless to pink) could be observed by naked eyes. • The detection limit of the probe was 0.097 μM. • The probe was successfully applied to detecting H 2 S in real water samples and HeLa cells. In this work, a reaction-based fluorescence turn-on probe RCHO, a rhodol derivate anchored with the 2,4-dinitrophenyl moiety, was designed and synthesized for H 2 S detection. The 2,4-dinitrophenyl moiety, as an electron-withdrawing group, was used for quenching the fluorescence of the fluorophore. The probe RCHO could quantitively detect H 2 S with high selectivity and fast response by introducing aldehyde groups in the ortho position of 2,4-dinitrobenzene. After addition of H 2 S, H 2 S was quickly added to the aldehyde group through a nucleophilic addition reaction, and then the dinitrophenyl ether underwent effective intramolecular thiolysis, which resulting in the release of the fluorophore and a rapid fluorescence turn-on response. The detect limit was calculated to be 0.097 μM. Furthermore, in the presence of H 2 S, a remarkable color change from colorless to pink was observed, indicating that the probe RCHO could monitor H 2 S by the naked eyes. More importantly, the probe could be used as a highly efficient tool for H 2 S detection in living cells and environmental water. [ABSTRACT FROM AUTHOR]

[Display omitted] • A newly developed Chemosensor HL for effective detection of Zn(II) with the formation of complex 1 in presence of azide. • The fluorescence microscopic images of normal HEK cell assures the biomedical application of HL towards Zn(II) • Complex 1 haven been further utilized for easy detection of Al(III) ion with the formation of Zn-Al bimetal complex • An INHIBIT logic circuit is formed with two step sensing phenomena along with the formation of a molecular memory A schiff base chemosensor HL [4-chloro-(((2-(piperidine-1-yl)imino)methyl)phenol], constructed by one step condensation of 2-aminoethyl piperidine and 5- Chloro Salicylaldehyde is illustrated to have its usefulness for selective and sensitive detection of Zn(II) among other metal ions in aqueous solution (HEPES buffer) displaying the colour changes from light blue to turquoise under UV light. The specific detection phenomena of Zn (II) is monitored by the remarkable fluorescence enhancement and notable change in NMR spectral data of fluorescence active HL after addition of Zn(II) to it. The impressive high binding constant in 106 orders, determined by electronic spectral titration after introduction of Zn(II) to HL assure the formation of a Zinc complex during sensing phenomena. In order to check whether the nuclearity of the constructed complex can be increased or not fluorescence enhancement phenomenon is further monitored in presence of different bridging ligands and the results display that only in presence of azide a significant enhancement of Zn(II)- HL domain is exposed where as for other bridging ligand the spectra remain unaltered. This observation insists to conduct the reaction between HL and ZnCl 2 in presence of sodium azide which lead the formation of a Zn complex [Zn 2 (HL) 2 (N 3) 4 (complex 1) employing azide as the secondary anionic residue instead of bridging. The single crystal structure of the complex unveils the unique protonation of the piperidine N during the crystallization of the dinuclear motif of the complex 1. Furthermore the Zn complex due to the presence of remarkable luminescence property have been effectively used for selective sensing of Al(III) ion as metalloreceptor in HEPES buffer solution via turn of fluorescence with remarkable fluorescence quenching constant. In aqueous solution, complex 1 induces a 1:2 complex formation with Al(III) ion indicated by Job's plot analysis. The DFT study suggests the formation of bimetal complex during sensing of Al(III) with complex 1 as metalloreceptor. The in vitro cell imaging study gives a authentic hints for in vivo biomedical application of HL as a selective and easy Zn(II) sensor. The two step sensing phenomena of HL and complex 1 is further established by advanced molecular logic gate formation. [ABSTRACT FROM AUTHOR]

Herein, a novel coumarin-based fluorescent probe (FS3) was designed, synthesized, and characterized. It exhibited significant fluorescence quenching in the presence of Zn2+ ions. Just a minor alteration occurred in the fluorescence intensity of FS3 in the presence of other metals studied. The limit of detection for the determination of Zn2+ by FS3 was calculated to be 3.43 × 10−9 M. Since the Job's graph of 1/(F 0 –F) and 1/[Zn2+] had a linear fit, it was determined that the binding stoichiometry between the FS3 and Zn2+ was 1:1. The association constant of the system was found to be 2.39 × 104 M−1 and confirmed by ESI-MS and FT-IR. It was demonstrated that the developed highly reversible sensor system works by performing real sample analysis. Moreover, the FS3 which has shown no toxicity and displayed a strong fluorescence image will act as an efficient and non-destructive sensor for the determination of Zn2+ in living organisms. [Display omitted] • A novel coumarin-based fluorescent probe (FS3) was designed, synthesized, and characterized. • Significant fluorescence quenching was observed in the presence of Zn2+ ions. • Stoichiometry between the FS3 and Zn2+ was 1:1. • The association constant for Zn2+ binding with FS3 was found to be 2.39 × 104 M−1 according to the Benesi-Hildebrand method. [ABSTRACT FROM AUTHOR]

Amlodipine, a unique long-lasting calcium channel antagonist and antihypertensive drug, has weak fluorescence in aqueous solutions. In the current paper, we show that direct visualization of amlodipine in live cells is possible due to the enhanced emission in cellular environment. We examined the impact of pH, polarity and viscosity of the environment as well as protein binding on the spectral properties of amlodipine in vitro, and used quantum chemical calculations for assessing the mechanism of fluorescence quenching in aqueous solutions. The confocal fluorescence microscopy shows that the drug readily penetrates the plasma membrane and accumulates in the intracellular vesicles. Visible emission and photostability of amlodipine allow confocal time-lapse imaging and the drug uptake monitoring. [ABSTRACT FROM AUTHOR]

Nanomaterial-based on-off-on fluorescence sensing strategies are significant particularly in intracellular nucleic acids imaging assay. There still remains challenge to rationally balance fluorescence quenching efficiency and recovery dynamics. We assume that the performance of on-off-on fluorescence sensing strategy can be fundamentally improved on small zero-dimensional (0D) nanomaterial with precisely modulated surface charge. For a proof-of-concept demonstration, silicon nanoparticle (SiNP) with ~4 nm was synthesized and used as the quencher model, of which the surface charge density was modulated by modification of triphenylphosphonium (TPP). The influence of particle size, surface charge and charge density of the nanomaterials on sensing performance was systematically investigated. The strategy showed a low limit of detection (LOD) as 26 pM for target model miR-494, which is one of the lowest in nanomaterial-based on-off-on sensing platforms. And the LOD is even comparable to amplification-based methods in a greatly shortened assay time (2.5 h). The miR-494 expresses in cancerous and normal living cells of human cervical carcinoma (HeLa), human lung carcinoma (A549), human breast cancer (MCF-7), and normal human mammary epithelial (MCF-10A) cells were imaged and localized with significantly improved sensitivity and specificity. These excellent performances insure it a promising candidate as convenient and non-enzymatic sensing platform for miRNA-associated disease detection and early diagnosis. Image 1 • The on-off-on sensing platform was improved by rationally optimized smaller size and precisely modulated surface charge. • The developed fluorescence sensing strategy is sensitive and fast. • The analytical performance of sensor had been applied to image and localize in living cells, as well as distinguish cancerous and normal cells. • The proposed protocol is simple, environment friendly and cost-efficient. [ABSTRACT FROM AUTHOR]

[Display omitted] • First report on N-Ti 3 C 2 QDs/Fe3+ fluorescent probe for detection of glutathione. • The fluorescent nanoprobe displays a high sensitivity for glutathione. • The nanoprobe may provide a way for imaging-guided precision cancer diagnosis. MXene quantum dots have attracted much attention due to their great optical performance and excellent water solubility. Glutathione (GSH) plays a key role in living cells. In this study, a biocompatibility nanoprobe was prepared for detecting intracellular GSH based on MXene N-Ti 3 C 2 quantum dots (N-Ti 3 C 2 QDs). The N-Ti 3 C 2 QDs act as the fluorescence reporters and the ferric iron (Fe3+) as the quenchers based on nonradiative electron-hole annihilation. When Fe3+ encounters the amino group of N-Ti 3 C 2 QDs, the electrons of N-Ti 3 C 2 QDs in the excited state will transfer to the half-filled 3d orbitals of Fe3+, leading to the fluorescence quenching of N-Ti 3 C 2 QDs. When the N-Ti 3 C 2 QDs/Fe3+ nanoprobe acts on the cancer cell MCF-7, the abundant GSH in the cancer cells can reduce Fe3+ to Fe2+, which will restore the fluorescence of N-Ti 3 C 2 QDs. The N-Ti 3 C 2 QDs/Fe3+ nanoprobe displays a high sensitivity for GSH with a detection limit of 0.17 μM in range of 0.5−100 μM. It becomes a promising probe for detecting and showing cellular imaging of GSH in MCF-7 cells. The N-Ti 3 C 2 QDs/Fe3+ nanoprobe might provide a new way for imaging-guided precision cancer diagnosis. [ABSTRACT FROM AUTHOR]

A novel effective chemosensor HPHN , (E)-6-hydroxy-N′-((2-hydroxynaphthalen-1-yl)methylene) picolinohydrazide, was synthesized. HPHN sensed Fe3+/2+ with the changes of color from yellow to orange without obvious inhibition from other cations. In addition, HPHN could detect ClO− by both the color change from yellow to colorless and the fluorescence quenching. The binding modes of HPHN with Fe3+/2+ and ClO− were determined to be 1:1 with Job plot and ESI-mass analysis. HPHN displayed low detection limits of 0.29 μM for Fe3+ and 0.77 μM for Fe2+. For ClO−, the detection limit was 6.20 μM by colorimetric method and 3.99 μM by fluorescent one, respectively. Moreover, HPHN can be employed to quantify Fe3+ and ClO− in environmental samples and apply to cell imaging for ClO−. Unlabelled Image • A picolinohydrazide-based fluorescent and colorimetric sensor HPHN for Fe2+, Fe3+ and ClO− was developed. • Fe2+/3+ and ClO− resulted in an instant color change of HPHN from yellow to orange and colorless, respectively. • HPHN could be used to detect ClO− as a "turn-off" fluorescence sensor. • Chemosensor HPHN can be used to bio-image ClO− in cells. [ABSTRACT FROM AUTHOR]

Adenine-stabilized carbon dots (A-CDs) are shown to be a viable fluorescent probe for highly sensitive detection and imaging of Cu2+. The probe has a linear fluorometric response in the 1–700 nM concentration range and a 0.3 nM detection limit. The probe, with excitation/emission maxima at 380/435 nm, is highly selective for Cu2+ over other metal ions, anions, amino acids, and biomolecules. The fluorescence quenching mechanism of the A-CDs by Cu2+ is investigated using transmission electron microscopy images coupled with elemental mapping, X-ray photoelectron spectroscopy, X-ray-excited Auger electron spectroscopy, fluorescence lifetime, UV–visible spectroscopy, and cyclic voltammetry. The experimental results show that the fluorescence quenching is caused by the combination of Cu2+-coordination-induced aggregation of the A-CDs, the reduction of Cu2+ by the A-CDs, and the nonradiative photoinduced electron transfer process from the A-CDs to Cu2+ or metallic Cu. The high sensitivity and high selectivity of the sensor are ascribed to the chemical interactions between the A-CDs and Cu2+, the photophysical process between the A-CDs and Cu2+, and the high fluorescence quantum yield of the A-CDs (44.6%). The A-CDs have excellent water solubility, good stability to variation of pH values, high photostability, fast response time, and low cytotoxicity. They are successfully employed for intracellular imaging of Cu2+ in HepG2 cells and Cu2+ detection in the tap water samples. A facile and low-cost fluorescence sensor is developed for highly sensitive and selective detection of Cu2+ using adenine-stabilized carbon dots (A-CDs) as fluorescent receptors. Unlabelled Image • The A-CDs are used as fluorescence receptors for Cu2+ detection. • The A-CDs-based sensor shows high sensitivity and selectivity toward Cu2+. • The fluorescence quenching mechanism of the A-CDs by Cu2+ is reasonably explained. • The A-CDs show excellent water-solubility, high photostability, and low cytotoxicity. • The A-CDs are used for intracellular Cu2+ imaging. [ABSTRACT FROM AUTHOR]

Protein-encapsulated gold nanoclusters (Au NCs) have recently gained much attention in biosensing and bioimaging applications owing to their remarkable fluorescence properties, nontoxicity and good biocompatibility. In this work, the mannose was grafted onto the bovine serum albumin (BSA) encapsulated Au NCs (BSA-Au NCs) to produce a mannose functionalized BSA-Au NCs (Man-BSA-Au NCs) as a new fluorescence probe for Concanavalin A (Con A) detection and human breast cancer cell imaging. A new strategy with mannose-BSA conjugates as template was firstly applied for the synthesis of Man-BSA-Au NCs, leading to a high loading of mannose (767.6 ± 7.2 mg/L) onto BSA-Au NCs. The as-prepared Man-BSA-Au NCs showed advantages of facile preparation, good monodispersity and strong red-emission. Notably, aggregation-induced fluorescence quenching of Man-BSA-Au NCs was triggered by Con A due to the multivalent cooperative interactions between mannose and Con A, which was subsequently confirmed by MALDI-TOF MS. Hence highly selective and sensitive fluorescence detection of Con A was achieved by using Man-BSA-Au NCs as a fluorescence sensor. A good linear relationship was obtained over the range of 0.01–1 μM (R2 = 0.994) with a detection limit of 0.62 nM (S/N = 3). The developed sensor was then applied to determine Con A in human serum with acceptable recoveries of 93.70–104.8%. Moreover, based on the specific recognition between mannose and overexpressed mannose receptors on human breast cancer cells, the Man-BSA-Au NCs were successfully utilized for cancer cell imaging with good specificity. Image 1 • Man-BSA-Au NCs with high mannose loading were facilely prepared with new strategy. • Con A triggered an aggregation-induced "fluorescence quenching" of Man-BSA-Au NCs. • Man-BSA-Au NCs showed good sensitivity and selectivity for Con A sensing. • Man-BSA-Au NCs showed good specificity for human breast cancer cell imaging. [ABSTRACT FROM AUTHOR]

In this paper, a simple, economical, and green strategy is developed for producing nitrogen doped graphene quantum dots (N-GQDs) with multicolor light emission by hydrothermal treatment of Passiflora edulia Sims. The synthesized N-GQDs exhibit ideal ionic stability, hydrophilicity and anti-photobcleaching properties, and the quantum yield reaches up to about 29%. Because of with the fluorescence quenching effect, the achieved N-GQDs allow to detect Ag+ in a linear range of 10 nM–160 μM, and the limit of detection is calculated to be 1.2 nM according to the S/N of 3. Noteworthy, N-GQDs with blue, green and yellow light emissions are demonstrated via regulating the reaction time and temperature, implying a promising fluorescence adjustability. Furthermore, the N-GQDs-based fluorescent probe exhibits low cytotoxicity and favorable biocompatibility. Depending on the superior properties, our N-GQDs are applied in fluorescent ink and multicolor cell imaging. Eventually, the developed sensor is highly selective and accurate for Ag+ analysis in real water, which demonstrates the promising practical use in environmental determination and/or biomedical engineering. [ABSTRACT FROM AUTHOR]

Although all kinds of sensors with unique detecting ability for one guest were reported, the fluorescence sensor with multiple detecting abilities was seldom presented. This work designed and synthesized a novel AIE fluorescence probe bearing double detecting for ATP based on Cu2+ and Zn2+ response of hydrazono-bis-tetraphenylethylene (Bis-TPE). Bis-TPE was prepared in 82% yield with simple procedure. It exhibited strong red AIE fluorescence based on the large conjugated electron effect in aqueous media. It showed outstanding selective sensing abilities for Cu2+ by strong fluorescence quenching and for Zn2+ by red-orange fluorescence change. The sensing mechanism of 1:1 stoichiometric ratios was confirmed by 1H NMR and MS study. The strong red fluorescence of Bis-TPE + Cu2+ system could be recovered by adding ATP. The orange fluorescence of Bis-TPE + Zn2+ system could be quenched by adding Cu2+ and then was recovered by adding ATP. These double detecting abilities for ATP with the "off-on" red fluorescence in Bis-TPE + Cu2+ system and "allochroic-off-on" orange fluorescence in Bis-TPE + Zn2++Cu2+ system were successfully applied to test Cu2+, Zn2+ and ATP in test paper and living cell imaging, displaying the good application prospects for sensing Cu2+, Zn2+ and double detecting ATP in the complicated environment. Image 1 • Hydrazono-bridged bis-tetraphenylethylene (Bis-TPE) was prepared in 82% yield. • The first double-detecting Fluorescent Sensor for ATP was observed by Bis-TPE. • Bis-TPE showed selective sensing abilities for Cu2+ with fluorescence quenching. • Bis-TPE exhibited sensing abilities for Zn2+ by red-orange fluorescence change. • Bis-TPE was applied to test Cu2+, Zn2+ and ATP in test paper and living cell imaging. [ABSTRACT FROM AUTHOR]

• Water-soluble fluorescence chemosensors (sensor 1 and sensor 2) based on benzothiazole were synthesized and characterized. • Sensor 1 and sensor 2 displayed high selective and sensitive "on-off" fluorescence sensing for Fe3+ ion. • The job's plots, mass spectrometry, 1H NMR titration and DFT calculations demonstrated that sensors formed 1:1 complexes with Fe3+. • Sensors with low toxicity and good cell permeability can detect Fe3+ ions in living cells. Two new benzothiazole-based fluorescence sensors (sensor 1 and sensor 2) have been successfully synthesized and their structures have been well characterized by 1H NMR, 13C NMR and mass spectrometry. Sensor 1 and sensor 2 displayed a selective fluorescence quenching response towards Fe3+ ions in aqueous solutions with good anti-interference ability. Sensor 1 and sensor 2 exhibited lower detection limits for Fe3+, 8.43 μM for sensor 1 and 5.86 μM for sensor 2, respectively. The Job's plot, mass spectrometry, 1H NMR titration and DFT calculations proved that sensors formed 1:1 complexes with Fe3+ ions. In addition, sensor 1 and Sensor 2 had low cell toxicity and could be used to monitor the existence of Fe3+ ions in living cells. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Ag+ and SCN− play extremely important roles in the fields of the physiology and environment. In this work, on the basis of phenanthro[9,10- d ]imidazole derivative (DIPIP) which can exhibit the aggregation-induced emission (AIE) properties in aqueous solution, we achieved a sequential on-off-on switch for Ag+ and SCN− with high selectivity and sensitivity. A remarkable fluorescence quenching effect of Ag+ on the probe DIPIP was observed with 1:2 stoichiometry, Subsequently, the fluorescence intensity of in situ generated DIPIP -Ag+ ensemble was easily switched on after the interaction between Ag+ and SCN−, which was attributed to the stronger affinity of SCN− to capture Ag+. In particular, the extreme limits of detection (LOD) for Ag+ and SCN− in standard solutions were as low as to be 74.5 nM and 7.8 nM, respectively. Furthermore, the probe DIPIP and the DIPIP -Ag+ ensemble could be used to detect Ag+ in the real water and SCN− in smoker saliva samples, respectively. In addition, the sequential "on-off-on" fluorescence mode of DIPIP to Ag+ and SCN− were also successfully applied in living HeLa cells. Unlabelled Image • Fluorescent probe DIPIP was designed and prepared; • DIPIP had obvious AIE activity; • A "on-off-on" sequential detection for Ag+ and SCN– with the extreme lower LOD was studied; • The responses of DIPIP to Ag+/AgNPs and of Ag+ to SCN− were applied in water and saliva samples. • Mode of the sequential sensing was realized in cells imaging. [ABSTRACT FROM AUTHOR]

Red emissive B,N co-doped carbon dots (BN-CDs) were hydrothermally synthesized from cresyl violet and boric acid. The BN-CDs exhibited excellent photostability, low cytotoxicity, excitation/emission maxima at 520/616 nm, and a relatively high quantum yield of 18%. The BN-CDs can binded to mercury(II), and this results in quenching of the red-colored fluorescence. However, on subsequent addition of the biothiol (such as cysteine, homocysteine or glutathione), fluorescence recovers. Therefore, the BN-CDs can be used as a multifunctional probe based on "on-off-on" fluorescence response for the detection of Hg(II) and biothiols. The following detection limits were accomplished: (a) Hg(II): 2.8 μM; (b) glutathione: 1.7 μM; (c) cysteine: 2.3 μM; (d) homocysteine: 3.0 μM. The BN-CDs also have been successfully applied for the imaging of Hg(II) and biothiols in HepG2 cells with excellent bio-compatibility. [ABSTRACT FROM AUTHOR]

• A simple anthracene-based fluorescent "on-off" probe was developed for Fe3+. • The transformation from anthraldehyde dimethyl acetal to anthraldehyde was achieved. • The probe displayed good performance on living cell imaging. A simple fluorescent probe L for Fe3+ was easily synthesized based on anthracene. Among the various metal ions including Fe2+, this probe exhibited high sensitivity and good selectivity toward Fe3+ with turn-off fluorescence mode in DMSO-HEPES buffer solution (20 mM, pH = 7.0, 1:1 (v/v)). When adequate Fe3+ ion was added into the solution of probe L , its molecular structure transferred from anthraldehyde dimethyl acetal to anthraldehyde, resulting in fluorescence quenching with a low detection limit of 3.08 μM. 1H NMR spectra and TLC analysis further supported this concept. Finally, this probe was successfully applied in bioimaging. [ABSTRACT FROM AUTHOR]