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[Display omitted] • Hydrazone based dual mode fluorescence sensor for Zn2+ ("turn-on") and Hg2+ ("turn off"). • Probe C1 selectively sense Zn2+and Hg2+ ions with their lowest detection limits 0.042 μM and 0.081 μM respectively. • The designed probe C1 was studied latent fingerprint analysis in various surfaces. • Live cell imaging studies was performed for probe C1 in presence and absence of Zn2+, Hg2+ ions. A facile Schiff base probe C1 has been developed and evaluated using 1H, 13C NMR, and mass spectroscopy. Fluorescence investigations were conducted to determine probe-sensing behavior. Probe C1 demonstrated sensitive, and selective recognition of Zn2+ and Hg2+ ions by using two distinct processes (i.e., chelation enhanced fluorescence effect and fluorescence quenching) over other cations in ACN-H 2 O (8:2, v/v). The Zn2+ and Hg2+ detection limits of 0.042 and 0.081 μM are achieved with the probe C1. C1 has a binding constant of 3.33 × 103 M−1 for Zn2+ and an emission quenching constant of 1.22 × 104 M−1 for Hg2+. A Jobs plot was used to determine the binding stoichiometry of C1 and Zn2+/Hg2+ ions ratio is 1:1. By using Zn2+/Hg2+ and EDTA additions alternately, the probe's reusability was investigated. Moreover, the probe was found to be highly cytocompatibility using an MTT assay in a mouse fibroblast cell line (NIH3T3). Further, the probe was found to visualize Zn2+ and Hg2+ ions inside the cells, indicating the potential application of the probe as an intracellular probe to detect Zn2+ and Hg2+ ions. The probe shows very good solid-state emission behavior, this motivates us to develop latent fingerprint detection and anticounterfeiting applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • An azo-Schiff base (ASB) chemosensor was synthesized from salicylaldehyde and N, N-dimethyl-4,4′-azodianiline. • ASB exhibits turn-on fluorescence toward Al3+ due to the Al3+-promoted hydrolysis of imine bonds. • ASB can be used for qualitative and quantitative Al3+ sensing in three antacid tablets. • ASB can be applied to cell imaging of Al3+ in breast cancer cell MCF-7. The azo-Schiff base (ASB) chemosensor was designed and synthesized by the reaction of salicylaldehyde and N, N-dimethyl-4,4′-azodianiline. The ASB sensor can be used to detect Al3+ in antacid tablets and cell imaging applications. After adding Al3+ ions, the ASB sensor exhibits turn-on fluorescence performance because of the Al3+-promoted hydrolysis of the imine bond. The Al3+-promoted hydrolysis of the imine bond has been evidenced by FTIR, 1H NMR, and 13C NMR spectra analysis. The ASB sensor displayed a selective and sensitive recognition of Al3+ by turn-on fluorescence with the detection limit of 1.53 × 10−7 M, and a binding constant of 2.36 × 104 M−1 in an aqueous HEPES buffer/DMSO solution (2/8 v/v). The ASB sensor can be applied to the qualitative and quantitative detection of Al3+ in three antacid tablets (Gelusil, Macgel, Swellin). Besides, the ASB sensor shows low cell toxicity and good cell permeability. The cell-imaging test indicates that the ASB probe can detect Al3+ ions in breast cancer cell MCF-7 under optical fluorescence microscopy. [ABSTRACT FROM AUTHOR]

Mercury (Hg) is one of the most widespread pollutants that pose serious threats to public health and the environment. People are inevitably exposed to Hg via different routes, such as respiration, dermal contact, drinking or diet. Hg poisoning could cause gingivitis, inflammation, vomiting and diarrhea, respiratory distress or even death. Especially during the developmental stage, there is considerable harm to the brain development of young children, causing serious symptoms such as intellectual disability and motor impairments, and delayed neural development. Therefore, it's of great significance to develop a specific, quick, practical and labor-saving assay for monitoring Hg2+. Herein, a mitochondria-targeted dual (excitation 700 nm and emission 728 nm) near-infrared (NIR) fluorescent probe JZ-1 was synthesized to detect Hg2+, which is a turn-on fluorescent probe designed based on the rhodamine fluorophore thiolactone, with advantages of swift response, great selectivity, and robust anti-interference capability. Cell fluorescence imaging results showed that JZ-1 could selectively target mitochondria in HeLa cells and monitor exogenous Hg2+. More importantly, JZ-1 has been successfully used to monitor gastrointestinal damage of acute mercury poisoning in a drug-induced mouse model, which provided a great method for sensing Hg species in living subjects, as well as for prenatal diagnosis. [Display omitted] • An activated probe JZ-1 for fluorescent detecion of Hg2+ was devised. • JZ-1 has dual NIR excitation and emission analysis wavelengths (both > 700 nm). • JZ-1 has a rapid response time and outstanding detection limit. • It was successfully used to in a drug-induced mouse of acute mercury poisoning. [ABSTRACT FROM AUTHOR]

• CM exhibit "Turn-On" blue fluorescence response for Ca2+ in solution, which is free from interference of co-existing cations. • "Tyndall Effect" can be observed during chelation, blue emissive nanowires induced by aggregation were investigated. • The molecular docking result reveals CM can bind with receptor 1A of melatonin via hydrogen bond. • CM and its Ca2+ complex shows good cell permeability and low cytotoxicity, their localization in organelle were studied. Due to a physiological significant role of calcium ion, it is essential to develop ways of detecting and monitor the level of Ca2+ ions in living cell. Herein, we rationally designed and synthesized a functional blue fluorescent compound CM based on amide condensation of coumarin and melatonin. Interestingly, it could exhibit an "On-OFF" fluorescence response for Ca2+ in an aqueous environment with 80-fold enhancement in bright blue emission, which is also free from interference of other co-existing cations of high concentration. A detection limit of 0.28 ppm was obtained, and the binding ratio of CM and Ca2+ is further investigated by Job's plot. After coordination of CM with calcium ion, a significant "Tyndall Effect" can be observed, and blue emissive nanowires induced by aggregation of complex of CM and Ca2+ were further investigated by Dynamic Light Scattering, analysis of Zeta potential, and confocal imaging. The molecular docking of CM with melatonin receptor 1A is also conducted. MTT assay reveals that CM ligand and the corresponding Ca2+ complex are non-cytotoxic. Moreover, CM shows good membrane permeability, and the relative cellular uptake mechanism is mainly dominated by an energy-dependent process. CM and its complex of Ca2+ can be further used as intracellular luminescent imaging probes and their localization in cell organelles is also revealed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple single step multicomponent ugi type reaction was carried out to yield N-(tert-butyl)-2-(furan-2-yl)imidazo[1,2- a ]pyridine-3-amine (TBFIPA). • The synthesized TBFIPA was characterized using 1H NMR, 13C NMR and HRMS spectroscopic methods. • The selective & sensitive detection was identified using hypsochromic shift (lab : 335nm → 285nm) & fluorescence quenching. • The proposed mechanism is evident from Job plot, 1H NMR titration, ESI-MS data and theoretical DFT calculation. • The Cr3+ ion-selective TBFIPA was successfully applied in the design of a user-friendly silica-based portable test kits. • Also, the fluorescence quenching ability of TBFIPA in presence of Cr3+ ions are validated by imaging onion epidermal cells. • Real samples contaminated with Cr3+ ions were identified using TBFIPA with an appropriated relative error percentage. A simple single step one pot multicomponent reaction was performed to synthesize N-(tert -butyl)-2-(furan-2-yl)imidazo[1,2- a ]pyridine-3-amine (TBFIPA). The synthesized TBFIPA was subjected to library of cations to study its ability for selective and sensitive detection of specific metal ions. Selective detection of chromium ions by TBFIPA were found from the significant hypsochromic shift (335 nm → 285 nm) in the UV–Visible spectra. The fluorescent TBFIPA displays complete quenching of fluorescence under UV lamp (365 nm) only in the presence of chromium without the interference of common metal ions. Binding constant (k a) obtained from Benesi-Hildebrand plot is 0.21 × 105 M−1, limit of detection (LOD) and limit of quantification (LOQ) of TBFIPA toward Cr3+ ions are 4.70 × 10−7 M and 1.56 × 10−7 M, respectively. The mechanism proposed during complex formation were supported by stoichiometric Job continuous variation plot, 1H NMR titration and ESI-MS spectroscopic data. All the experimental confirmation for complex formation were corroborated with theoretical DFT studies optimized using RB3LYP/6-31G(d) basis set. The selectivity and sensitivity of TBFIPA toward Cr3+ ions are found suitable to design a user-friendly silica based portable test kit. Alongside, TBFIPA was successfully utilized for imaging onion epidermal cells. Furthermore, the results obtained for biological, environmental, and industrial samples provided solid evidence to estimate chromium ions using TBFIPA in these real samples. [ABSTRACT FROM AUTHOR]

Photophysical study of Fluorescent Zn (II) Sensor. [Display omitted] • Fluorescence study of the rhodamine-quinoline type of Al3+sensor. • Absorption spectra of rhodamine-based fluorescent Al3+ chemosensor. • Bioimaging study of FRET-based chromium(III) sensor. • HOMO-LUMO structures of rhodamine-based colorimetric Cu(II) sensors. • Fluorescence emission study of rhodamine-based Fe3+chemosensor. • Live cell imaging of Rhodamine-based Hg2+ chemosensor. Rhodamine-based photoresponsive sensors have emerged as a focal point in the realm of chemical sensing, garnering substantial attention owing to their exceptional sensitivity, straightforward implementation, and real-time detection capabilities across diverse analytes. Within this class, a notable substituent stands out for its well-established reputation, characterized by its electron-donating prowess and customizable coordination cavity, resulting in a heightened sensitivity towards various metal ions. The comprehensive examination of these sensors in the review centers on key parameters such as the detection target, detection limit, detection solution system, and detection method. Notably, the inclusion of an array of metal ions in the discussion contributes to the versatility of these sensors. To enhance the readability and applicability of the review, a detailed exploration of the indirect sensing strategy is presented, showcasing its efficacy in achieving sensitive detection, especially for anions and other species. This strategic approach not only broadens the scope of application but also underscores the versatility of rhodamine-based sensors, making this review a valuable resource for researchers and practitioners in the field of chemical sensing. [ABSTRACT FROM AUTHOR]

[Display omitted] • The probe YX is a near-infrared fluorescent probe. • The probe YX can complete continuous detection Zn2+ and PPi. • The probe YX has a good application prospect in biology. • The probe can detect Zn2+ and PPi in actual samples. As the second most abundant transition metal element in the human body, zinc ions play an important role in the normal growth and development of the human body. We have successfully synthesized a near-infrared fluorescent probe with FRET effect for the detection of Zn2+. Probe DR6G has good selectivity and anti-interference ability for Zn2+. When Zn2+ is added to the probe DR6G solution, it responds completely within seconds, releasing red fluorescence with a detection limit of 2.02 × 10−8 M. As the main product of ATP hydrolysis, PPi is indispensable in various metabolic activities in cells and the human body. Due to the strong binding ability of Zn2+ and PPi, it is easy to form ZnPPi precipitation, so we added PPi to the solution to complete the Zn2+ detection, and realized the continuous detection of PPi, and the detection limit was 2.06 × 10−8 M. Since Zn2+ and PPi play an important role in vivo, it is of great practical significance to design and synthesize a fluorescent probe that can continuously detect Zn2+ and PPi. Biological experiments have shown that the probe DR6G has low cytotoxicity and can complete the detection of exogenous Zn2+ and PPi in cells and living mice in vitro. Bacterial experiments have shown that the DR6G probe also has certain research value in the field of environmental monitoring and microbiology. Due to the constant variation of the fluorescence signals of Zn2+ and PPi during detection, we designed the logic gate program. In practical applications, the probe DR6G can quantitatively detect Zn2+ in zinc-containing oral liquids and qualitatively detect PPi in toothpaste. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new asymmetrical photochromic diarylethene (DTE-HQo) exhibiting multicolour photoswitching behaviors have been successfully synthesized. • DTE-HQo can effectively distinguishes between Zn2+ and Cd2+ through visual observation due their distinct binding mode. • DTE-HQo could be applied in cell imaging. A new asymmetrical photochromic diarylethene DTE-HQo composed of a 2-hydrazinoquinoline moiety as the binding unit for ions and dithenylethene as a photoswitching trigger was reported. DTE-HQo displayed favourable photochromism upon irradiation with UV/vis light. Its fluorescent behaviour could be efficiently modulated by light, Zn2+, Cd2+ and HSO 4 −. The binding of Zn2+ induced a strong fluorescence peak at 510 nm in D TE -HQo due to the formation of a 1:2 complex [Zn2+ + 2 D TE -HQo ], resulting in a notable colour change from dark to intense white emission. Triggered by Cd2+, D TE -HQo formed a 1:1 complex [Cd2+ + D TE -HQo ], leading to an enhanced emission intensity by 21-fold with an emission peak red-shifted from 461 nm to 514 nm. Unexpectedly, [Zn2+ + 2 D TE -HQo ] underwent hydrolysis when stimulated with water, generating a yellow-emitting complex [Zn2+ + D TE -HQo ]. This color change easily distinguishes it from Cd2+ complex. Additionally, DTE-HQo showed high selectivity towards HSO 4 − and exhibited distinct "turn-on" fluorescence with a colour change from dark to bright blue upon stimulation. Moreover, the strong emission complexes of DTE-HQo with Zn2+, Cd2+ and HSO 4 − could be effectively quenched during the photocyclization process. Therefore, DTE-HQo can serve as an unimolecular multicolour photoswitching chemosensor, offering potential applications as a multifunctional probe for detecting Zn2+, Cd2+ and HSO 4 −. [ABSTRACT FROM AUTHOR]

[Display omitted] • Facile synthesis of fluorescent CDs from Schyzium cumini leaves by hydrothermal process. • CDs displayed excitation dependent emission with quantum yield of 15.9 %. • CDs have been used as sensing probe for the detection of Fe3+. • Low limits of detection and >85 % recovery in real water samples. • The synthesized CDs exhibits good biocompatibility and low cytotoxicity. In this study, carbon dots (CDs) derived from Syzygium cumini leaves were synthesized through a hydrothermal process and employed as a sensing probe for the highly sensitive and selective detection of Fe3+. The synthesized CDs underwent comprehensive analysis to discern their functional groups, composition, morphology, nature, and size. The CDs exhibited excitation-dependent emission fluorescence with a quantum yield of 15.9 %. Notably, Fe3+ induced a substantial quenching effect on the fluorescence intensity of the CDs compared to other metal ions. The developed fluorescent probe facilitated the selective detection of Fe3+ within a linear range of 0–300 µM, exhibiting a low detection limit (LOD) of 0.13 µM. Moreover, the applicability of the fluorescent probe was validated in real water samples, with the recovery and Relative Standard Deviation (RSD) values serving as indicators of specificity and selectivity. Additionally, the CDs were assessed for cell imaging in both normal human and cancer cells. The findings indicate that the produced CDs exhibit minimal cytotoxicity and outstanding biocompatibility, underscoring their potential for bioimaging applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A naphthalimide-based fluorescent probe for relay recognition of Cu2+ and S2− has been designed and synthesized. • The sensor has lower detection limit for Cu2+ and S2−. • Fluorescence behavior in the presence of Cu2+ and S2− could be manufactured to IMPLICATION type logic gate. • Intracellular fluorescence imaging in living cells were developed. A fluorescent chemosensor based on naphthalimide derivative (HL) was prepared and characterized. HL exhibited strong fluorescence emission at 528 nm, which was attributed to naphthalimide moiety, while the addition of Cu2+ almost completely quenched the fluorescence emission. However, with the addition of S2−, the fluorescence at 528 nm reoccurred remarkably. The detection limits for Cu2+ and S2− were measured to be 1.72 × 10−7 M and 2.66 × 10−7 M, respectively. As determined, the fluorescence behavior of HL in the presence of Cu2+ and S2− could be manufactured to IMPLICATION type logic gate. Moreover, confocal fluorescence imaging in HepG2 cells indicated that the HL could act as a useful fluorescent probe for intracellular Cu2+ and S2− detection with negligible cytotoxicity. [ABSTRACT FROM AUTHOR]

A new hemicyanine-based near-infrared "off-on" recognition Cu2+ fluorescent probe NRh-NP was designed and successfully synthesized. The structure of NRh-NP was characterized by NMR, ESI-HRMS and single crystal X-ray diffraction analysis. NRh-NP has high sensitivity, selectivity and a low limit of detection (33 nM as fluorescence sensor and 35 nM as UV sensor) to Cu2+. According to Job's plot and ESI-HRMS, the coordination ratio of NRh-NP to Cu2+ was 1:1. DFT theoretical calculations proved that the sensor mechanism was photo-induced electron transfer (PET). More importantly, NRh-NP has excellent membrane permeability and low cytotoxicity, which could be used not only for the detection of Cu2+ in human breast cancer cells (MCF-7), but also for imaging Cu2+ in living mice. [Display omitted] • The structure of NRh-NP was characterized by NMR, ESI-HRMS and single crystal X-ray diffraction analysis. • The responses of NRh-NP toward Cu2+ were fully proved by Job's plot, ESI-HRMS and DFT theoretical calculations. • NRh-NP has high sensitivity and selectivity with detection limit as low as 33 nM. • NRh-NP can be used for Cu2+ imaging in living cells and in vivo. [ABSTRACT FROM AUTHOR]

• Synthesized a unique naphthalimide-rhodamine based chemosensor (NR-HG) for the selective detection of Hg2+ ion. • NR-HG shows an impressive LOD 491 nM and exhibits reversibility. • Synthesized Probe works through PET, CHEF, and FRET leading to the chelation-induced ring opening. • TD-DFT calculation supported the origin of the fluorescence emission maxima. • NR-HG is stable in biological pH and can efficiently image Hg2+ in SiHa cells under the fluorescence microscope. In this work, we are presenting the design and synthesis of an innovative fluorescent chemosensor: NR-HG, established on a naphthalimide-based rhodamine platform for Hg2+ ion sensing. The probe operates via PET, CHEF, and FRET mechanisms. The fluorescent chemosensor shows an immense selectivity and sensitivity towards Hg2+ ion via the enhancement of ring-opening rhodamine spiro-cyclic structure, with a detection limit (LOD) of 491 nM. The DFT analysis strongly validates the experimental observations. The probe senses the Hg2+ ion reversibly upon the addition of potassium iodide (KI). From the analysis of Job's plot, it can be conclusively confirmed that the NR-HG-Hg2+ complex demonstrates a 1:1 stoichiometric ratio. We also conducted an MTT assay and cell imaging experiment to assess both the compatibility of the probe with living cells and its effectiveness in real-life imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • A Zn2+ selective turn-on optical sensor (DIH) with ESIPT process was reported. • DIH showed high selectivity and sensitivity Zn2+ over other metal ions tested. • The detection mechanism was elucidated by ESI–MS, NMR and DFT calculations. • The sensor is suitable for imaging Zn2+ in living cells. Zinc ions (Zn2+) play a significant role in our daily lives and production, which is related to human health and environment protection. Therefore, it is crucial in this field to develop sensors with improved analyte selectivity and sensitivity. We prepared a fluorescent sensor, DIH, through the reaction of 5-(tert -butyl)-2-hydroxyisophthalaldehyde with isonicotinohydrazide. DIH, in free form, can undergo excited state intramolecular proton transfer (ESIPT) process upon excitation. Among a wide range of metal ions tested, only Zn2+ inhibited this ESIPT process, resulting in an increase in fluorescence intensity (13.3-fold) with chelation enhancement fluorescence process (CHEF). The complex (DIH/Zn2+) stoichiometry was determined to be 1:1 and the binding constant of the complex was estimated as 3.18 × 107 M−1. DIH could also be applied to detect zinc ions down to a low concentration level of 11.2 nanomolar with fluorescence spectroscopy. Moreover, the cytotoxicity evaluation of DIH against human colon adenocarcinoma cells lines demonstrated that the sensor was nontoxic and could be used successfully in cellular imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • A colorimetric and fluorometric dual-signals probe Rb-HMD based on rhodamine B and tetrapeptide was firstly synthesized. • Rb-HMD exhibited a fluorescence "turn-on" response and colorimetric analysis to trivalent ions (Fe3+, Al3+ and Cr3+). • Rb-HMD showed low detection limits for sensing of Fe3+ (16.4 nM), Al3+ (0.12 μM) and Cr3+ (0.24 μM). • Rb-HMD was successfully applied for trivalent ions (Fe3+, Al3+ and Cr3+) imaging in living cells. • Smartphone-assisted probe Rb-HMD was used to realize the semi-quantitative detection of Fe3+ ions. In this study, a new dual-signals probe Rb-HMD with colorimetric and fluorescent was designed and synthesized by conjugating tripeptide backbone (His-Met-Asp-NH 2) with a rhodamine B derivative using solid phase peptide synthesis (SPPS) technology. Rb-HMD exhibited highly selective recognition of trivalent ions (Fe3+, Al3+ and Cr3+) by fluorescence enhancement and colorimetric observation in the presence of other competing metal ions. Notably, the limit of detections (LODs) for Fe3+, Al3+, and Cr3+ were 16.4 nM, 0.12 μM and 0.24 μM, respectively, indicating that Rb-HMD has good application prospects for high sensitive detection of Fe3+, Al3+ and Cr3+ in real samples and biological systems. Additionally, cytotoxicity and cells imaging demonstrated that Rb-HMD has very low toxicity in living cells even at concentrations up to 80.0 μM, and was successfully applied to detect Fe3+, Al3+ and Cr3+ in living cells. Moreover, the gradient change of color of Rb-HMD was captured by smartphone under UV light at 365 nm, and then content analysis was carried out by color recognition APP , which makes it possible to detect Fe3+ in rapid and accurate semi-quantitative way without other large valuable instruments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel amino-pyridyl-benzothiazole derivatives were implemented as Zn2+ sensors. • A gradient turn-on luminescence response was observed upon coordination with Zn2+. • Instantaneous and selective determination in the 4.7 to 80 μM range was verified at pH 7.0. • The sensor revealed intracellular Zn2+ levels of some cancer cell lines. • The real-time epifluorescence distribution profiles correlated with the concentration and location of the target within living cells. Novel amino-pyridyl-benzothiazole-derivatives (PBT) were synthesized through cycloaddition/nucleophilic aromatic substitution reactions for the development of a turn-on fluorescence chemosensor that accurately determines Zn2+ in polar media. The selectivity, water-solubility, and overall analytical response were systematically optimized through incorporation of different aliphatic amines as substituents: pyrrolidine (PBT-Pyn), ethylenediamine (PBT-Et) or 1,3-propylenediamine (PBT-Pr). Those ligands presented intense dual radiative emissions in the blue/green region upon activation with a 395 nm LED, which were attributed to the local excitation and internal energy transfer states. Although no variations were observed upon the interaction of Zn2+ with PBT-Pyn, both turn-off and turn-on responses were observed upon its interaction with PBT-Et. These responses depended on the ligand concentration and the associated inner filter effects. Thereby, PBT-Pr was selected for a deeper evaluation towards photoluminescence determination of Zn2+ due to its exclusive turn-on response and major sensibility obtained at pH 7.0, making it very convenient for analysis in physiological media. Under those conditions, the detection limits were 1.9 µM and 4.7 µM for measurements in aqueous or ethanolic solutions, respectively, with linear ranges up to 40 and 80 μM. The selectivity and good biocompatibility of the chemosensor were demonstrated through cell-viability assays with MCF-7, 3T3-L1 and HT-29 cell lines. The probe was then applied for the real-time epifluorescence imaging of Zn2+, observing emission intensities and distribution profiles that correlated with the concentration and location of the target within living cells. [ABSTRACT FROM AUTHOR]

Rhodamine dyes bearing aromatic nitro group has been synthesized for nitroreductase enzyme chemosensing applications. The probe is showing very selective turn-on fluorescent response towards nitroreductase enzymes and in hypoxic conditions. The sensor displays a remarkable fluorescent enhancement at 557 nm (λ ex = 500 nm) without the interference of other biologically relevant species under hypoxic conditions in a physiological medium. The nitro group in the sensor is reduced by the nitroreductase enzyme to the amino group, resulting in the hydrolysis of the probe and subsequent release of highly fluorescent rhodamine 6G dye is observed. This rhodamine based fluorescent probe has been utilized for the imaging of nitroreductase enzymes as well as hypoxia in live cells. Unlabelled Image • Turn-on fluorescence for Nitroreducatase enzymes • Excellent sensors for hypoxic conditions • Excellent fast response for Nitroreducatase by probes • Irreversible nature • Applicable to live cell imaging of NTR/hypoxia in live cells [ABSTRACT FROM AUTHOR]

• A mitochondria-targeted ratiometric fluorescent probe for cyanide was developed. • Mito-CP can detect endogenous cyanide in plant tissues and rat PC12 cells. • Mito-CP can recognize cyanide with dual-channel mode fluorescence imaging. • Mito-CP could detect cyanide in real water samples with quantitative detection. Various fluorescence probes for cyanide anions in water solution have been reported, but the investigation for endogenous cyanide recognition in plant tissues and mammalian cells is still limited. Here, a mitochondria-targeted cyanide fluorescent probe Mito-CP with colorimetric and ratiometric response was developed. The detection for cyanide was performed via the nucleophilic addition of cyanide to carbon-carbon double bond between coumarin moiety and pyridine moiety of the probe, which resulted in a color change from red to colorless and fluorescence change from red to blue. The probe showed high sensitivity (0.17 nM) and selectivity for cyanide over other common anion species and biothiols and could detect cyanide in real water samples with quantitative detection. Probe Mito-CP was successfully applied to detect endogenous cyanide in cassava root plant tissues. In addition, colocalization experiment showed that the probe has the property of targeting mitochondria with overlap coefficient being 0.93. A549 and HeLa living cells imaging experiment demonstrated the practical value of the probe in tracing CN− in biological systems. The probe also can detect endogenous cyanide change in mitochondria of rat pheochromocytoma (PC12) cells. [ABSTRACT FROM AUTHOR]

• A novel fluorescence sensor (TCS) for Pd2+ was designed and synthesized. • TCS exhibited selective sensing abilities for Pd2+ among various metallic ions. • The detection limit for Pd2+ was as low as 4.32 × 10−8 M. • The sensing mechanism of 1:1 stoichiometry ratio was confirmed. • TCS displayed good bioimaging performance on Pd2+ detection in living system. Although some Pd2+ sensors were presented, the in-situ and real-time examination of Pd2+ based on fluorescent sensor is still a challenging task. In this work, a novel thiourea-cyanostilbene derivative (TCS) was designed and synthesized as the effective fluorescent sensor on in-situ and real-time sensing Pd2+ in aqueous media. TCS possessed good AIE fluorescence in THF/H 2 O solution. The fluorescence was selectively quenched by Pd2+ among all kinds of metallic ions. The sensing mechanism of 1:1 stoichiometry ratio for TCS with Pd2+was confirmed by Job's plot, 1H NMR and MS spectra. The detection limit was as low as 4.32 × 10−8 M. TCS exhibited the good sensing application for Pd2+ in tested paper and simulated samples with low errors. TCS had the excellent fluorescence imaging performance in living cells with the fluorescence imaging response on Pd2+. This research not only reported an effective fluorescence sensor for Pd2+, but also suggested the good application prospect on in-situ and real-time sensing Pd2+ in complicated environment. [ABSTRACT FROM AUTHOR]

• A novel benzothiazole derivative BP was prepared for the relay quantification of Fe3+ and PPi. • Chemosensor BP displayed highly selective fluorescence "ON-OFF-ON" response to Fe3+ and PPi. • This chemosensor BP was applied to living cells imaging. A novel on-off-on fluorescence chemosensor BP based on benzothiazole for the relay recognition of Fe3+ and PPi was designed and synthesized. The chemosensor BP exhibited a high affinity to Fe3+ in the presence of other competing cations. The resultant BP -Fe3+ showed excellent recognition ability for PPi via Fe3+ displacement approach. The detection limits of BP for Fe3+ and BP -Fe3+ for PPi were estimated to be 2.59 × 10−8 M and 8.47 × 10−8 M, respectively. The low cytotoxicity and good cell-membrane permeability of BP and BP -Fe3+ complex makes them capable of Fe3+ and PPi imaging in living Hep G2 cells. [ABSTRACT FROM AUTHOR]

Abstract Nowadays, it is of great significance to develop a novel fluorescent chemosensor for Cd(II) ions detection with cost-effective, rapid, facile and applicable to environment and biological milieus. Herein, we report a new peptide-based fluorescent chemosensor DSC (Dan-Ser-Cys-NH 2) based on dipeptide (Ser-Cys-NH 2) conjugated with dansyl group, which was synthesized using solid phase peptide synthesis (SPPS) technology. As designed, DSC exhibited fluorescent "turn-on" response for Cd2+ in 100% aqueous solution over a wide range of pH values based on photoinduced electron transfer (PET). The stoichiometry binding of DSC and Cd2+ was determined to be 2:1 by Job's plot and ESI-MS analysis. Furthermore, DSC showed highly sensitive for Cd2+ and a low detection limit of 13.8 nM. What's more, DSC has cell permeability and low cytotoxicity, and fluorescence imaging experiments demonstrated that DSC was capable of monitoring Cd2+ in living HK2 cells by confocal microscopy. Graphical abstract Unlabelled Image Highlights • A novel peptide-based fluorescent chemosensor DSC was synthesized. • DSC exhibited highly selective fluorescent "turn-on" response toward Cd2+ ions. • DSC displayed highly sensitive, with Cd2+ ions detection limits of 13.8 nM. • DSC could serve as a potential chemosensor to detect Cd2+ ions in living cells. [ABSTRACT FROM AUTHOR]

Abstract In this study, sodium 2-Mercaptobenzimidazole-5-sulfonate (SMBD) was used as both a protecting ligand and a reducing agent to synthesize highly fluorescent gold nanoclusters (SMBD@AuNCs). When 360 nm was used as the excitation wavelength, the resultant AuNCs exhibited orange-yellow fluorescence with the maximum emission at 630 nm. In addition, it was found that the fluorescent SMBD@AuNCs could been significantly quenched by Hg2+ over other ions. The phenomenon was further used to design a SMBD@AuNCs-based fluorescence sensing method for the detection of Hg2+. Under the optimal conditions, the detection limit of the proposed method for Hg2+ was 0.5 nM, with a good linear range from 4.0 nM to 20.0 μM (R2 = 0.999). Then, it could be successfully utilized for determining trace amount of Hg2+ in real water samples. Furthermore, owing to the excellent biocompatibility, the as-prepared fluorescent AuNCs showed a great potential application in bioimaging fields. Cytotoxicity studies showed that the AuNCs exhibited negligible effects in altering cell proliferation or triggering apoptosis. The as-synthesized AuNCs have been successfully applied as a photoluminescent probe for human bladder cancer cellular imaging. Highlights • A facile, rapid "one-pot" synthesis of orange-yellow fluorescent SMBD@AuNCs at room temperature was proposed. • A new fluorescence sensing method for Hg2+ was designed based on the quenching phenomenon of SMBD@AuNCs. • The AuNCs have been successfully applied in human bladder cancer cellular imaging. [ABSTRACT FROM AUTHOR]

Abstract A newly designed 2-(2-Aminophenyl)-1 H -benzimidazole integrated anthracene/pyrene derivatives as efficient chemosensors were synthesized. The probes N-(anthracen-9-ylmethylene)-2-(1 H -benzo[d]imidazol-2-yl)aniline (ANP) and N-(pyren-1-ylmethylene)-2-(1 H -benzo[d]imidazol-2-yl)-aniline (PYP) exhibited high selectivity and sensitivity towards Al3+ ion over other interfering and competing cations in aqueous solution. Job's plot analysis reveals that the interaction of ANP/PYP with Al3+ was 1:1 binding stoichiometry. The detection limit of probes ANP and PYP for Al3+ ions were found to be 1.85 × 10−7 M and 1.08 × 10−7 M, respectively. The DFT/TD-DFT calculations have also been revealed that the ICT mechanism is responsible for the observed photophysical changes. Moreover, the probes ANP and PYP were applicable to image intracellular Al3+ ions in living cells via confocal fluorescence microscopy technique. Graphical abstract Image 1 Highlights • New anthracene and pyrene bearing Schiff base derivatives (ANP and PYP) were designed and synthesized. • The probes ANP and PYP served as an efficient fluorescent chemosensor towards Al3+ with high selectivity. • The 1:1 binding stoichiometry of the sensor ANP/PYP with Al3+ was established. • Reversibility of the chemosensor ANP/PYP was proved by experiments with EDTA. • ANP/PYP was successfully applied to fluorescence imaging of Al3+ in living cells. [ABSTRACT FROM AUTHOR]

Abstract As an efficient turn-on fluorescent chemosensor for Al3+, a new coumarin derivative (CND) has been designed and synthesized by the condensation of 8-formyl-7-hydroxycoumarin with niacin hydrazide. The spectroscopic studies revealed that the sensor CND exhibited a remarkable fluorescence enhancement towards Al3+ with high selectivity and sensitivity in EtOH-HEPES (95:5, v/v, pH = 7.40), which was attributed to the photoinduced electron transfer (PET) and C N isomerization mechanism. Fluorescence titration calculations data showed that the detection limit and the association constants of CND for Al3+ were found to be 2.51 × 10−7 M and 9.64 × 104 M−1, respectively. The results of experiments, including Job's plot, 1H NMR titration and ESI-MS, revealed that the stoichiometric binding between CND and Al3+ was 1:1. The investigations of the pH dependency of CND for Al3+ detection, and the cell imaging suggested the sensor CND could be promisingly applied for the recognition of Al3+ in biological cells. Graphical Abstract Unlabelled Image Highlights • A novel coumarin-based fluorescence sensor for Al3+ was designed and synthesized. • This sensor has good selectivity and sensitivity for Al3+. • This sensor can be applied in live cells. [ABSTRACT FROM AUTHOR]

Abstract An oxadiazole-based chemosensor (sensor 1) for Fe3+/Fe2+ was successfully designed and synthesized. Sensor 1 displayed fluorescence quenching response towards both Fe3+ and Fe2+ in THF:H 2 O (4:1, v/v) solvent with high selectivity and sensitivity over all other competitive metal ions. Job's plot, mass spectra, DFT calculation and fluorescence titration disclosed that fluorescence quenching was caused by forming 1:1 complex between sensor 1 and iron ions. Sensor 1 presented high sensitive fluorescence response at the pH value of human body and its fluorescence intensity showed linear relationship with the concentration of iron ion. Sensor 1 also presented fast fluorescence response towards iron ions and the lower detection limit, 7.78 μM for Fe2+ ion and 6.95 μM for Fe3+ ion, respectively. Sensor 1 can be used as test strips to detect iron ions in water samples. Fluorescence cell imaging also demonstrated sensor 1 can recognize iron ions in living cells. Graphical abstract Unlabelled Image Highlights • A new fluorescent sensor 1 containing oxadiazole and picolinic acid was designed and synthesized. • Sensor 1 displayed selective fluorescence quenching response towards both Fe2+ and Fe3+. • Sensor 1 can recognize iron ions with high selectivity in a wide pH range of 3~10. • Sensor 1 can detect iron ions in water sample and recognize iron ions in the form of test strips. • Fluorescence imaging proved sensor 1 can sense both Fe2+ and Fe3+ in living cell. [ABSTRACT FROM AUTHOR]

Abstract A new 2-hydroxynaphthalen based Schiff base colorimetric and fluorescence chemosensor, H 2 acid}, for selective sensing of Al3+ ions has been synthesized and characterize by different physico-chemical and spectroscopic techniques. The probe shows enhanced fluorescence and significant color change from bright yellow to colorless in the presence of Al3+ ions in methanol-water (9:1 v/v) solution, without interference from other metal ions. The binding mode of H 2 L with Al3+ was studied by UV–vis, fluorescence titration, job's plot analysis, and ESI-MS. The probe acts as a bidentate ligand and interacts with Al3+ ions with a binding constant of K b = 1.546 × 105 M−1. The limit of detection for Al3+ is found to be 6.4 × 10−7 M. The cytotoxicity of the probe has been evaluated by MTT assay on MCF-7 cell line, indicating more than 92% cell viability in the concentration range of 1.25–50 μM with no serious cytotoxicity on cells. Live cell imaging study clearly indicates that the accumulation of Al3+ in living cells can be detected by H 2 L. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Z with benzothiazole fluorophore was synthesized and characterized. • Z exhibits a 9-fold fluorescence enhancement and ratiometric absorption for Al3+. • LOD for Al3+ was determined by fluorescence and absorbance-ratiometric detection. • Z was applied to form paper strip sensor for Al3+ and cell imaging in HSC. Abstract Chemosensor Z including benzothiazole fluorophore was synthesized and characterized with NMR and HRMS spectroscopic techniques. Z exhibited fluorescence turn-on and ratiometric absorbance detection of Al3+ ions based on the combination mechanism of CHEF and ESIPT processes. Moreover, the stiochiometry between Z and Al3+ were determined 2:1 through job's plot and HRMS, and the limit of detection was determined as 8.47 nM which was qualified in the detection of Al3+ in drinking water. Especially, Z was achieved in fast identification the existence of Al3+ by filter paper, and cell imaging in human stromal cell (HSC). [ABSTRACT FROM AUTHOR]

Abstract A novel fluorescent probe, phenolphthalein‑dialdehyde‑(2‑pyridyl) hydrazone (L), for sequentially detecting Al3+ and F− in almost 100% aqueous medium was successfully designed and synthesized. The probe offers two binding pockets for Al3+ to form a 1: 2 ligand/metal complex, leading to a significant fluorescence enhancement at 465 nm. Further, the in-situ formed L-Al complex acts as a secondary fluorescent chemosensor for F− by quenching the fluorescence of the complex with high selectivity. The detection limit for Al3+ and F− sensing is 2.28 nM and 0.13 μM, respectively, which are far below the World Health Organization (WHO) acceptable limits (7.41 μM for Al3+ ion and 79 μM for F−) in drinking water. The probe L was successfully applied to the detection of Al3+ and F− in cells using fluorescence microscopy. Graphical Abstract The new fluorescent probe L can be used for selective detection of Al3+ and F− in almost 100% aqueous medium and live cells. Unlabelled Image Highlights • A new fluorescent probe L was synthesized and characterized • L can be used for selective detection of Al3+ and F−. • L exhibits a fluorescence response in almost 100% aqueous medium and live cells. • The detection limit for Al3+ was as low as nano-molar level. • L was employed for imaging the Al3+ and F− in living biological cells. [ABSTRACT FROM AUTHOR]

Abstract Hydrazino-carbothioamide, 1 , serves as a turn-on fluorescent chemosensor to Zn2+ and the mixture shows green emission (λ em 492) in presence of large number of ions with impressive limit of detection (LOD), 0.59 nM. Intense fluorescence of Zn-complex is selectively turn-off upon adding H 2 PO 4 − only to the limit of detection, 26 μM, while other anions remain silent. The sensing mechanism of 1 is established by suppressing the ESIPT of 1 and complexation with Zn2+ (CHEF) is supported by Job's plot, 1H NMR, and HR-MS data. Turn-on-off sequential detection of Zn2+ and H 2 PO 4 − also have successfully been employed for the engineering of INHIBIT molecular logic gate. The sensor is non-toxic and has been used in identifying Zn2+ in the intracellular region of African green monkey kidney cells (Vero cells). Graphical Abstract Very low detection limit (0.59 nM) is shown by green emission (492 nm) of hydrazino-carbothioamide probe on binding selectively with Zn2+ at pH, 7.2 which is specifically quenched by H 2 PO 4 − with LOD, 26 μM. This probe uses detection of Zn2+ in Vero cells and INHIBIT logic gate is constituted. Unlabelled Image Highlights • Hydrazino-carbothioamide sensor shows green emission with Zn2+. • Highly selective turn-on Zn2+ sensor shows LOD 0.59 nM. • Emission of the complex is quenched specifically upon addition of H 2 PO 4 − and LOD is 26 μM. • The sensor is non-toxic and identifies Zn2+ in the intracellular region of Vero cells. • Emission change at 492 nm with Zn2+ and H 2 PO 4 − can be described to INHIBIT logic gate. [ABSTRACT FROM AUTHOR]

Abstract Herein we pay attention to the design, synthesis and sensor activity of a novel biocompatible perylene-3,4,9,10-tetracarboxylic diimide (PDI) pH-probe in water. The synthesized compound shows selective fluorescence signalling properties as a function of pH (p K a value of 6.35 ± 0.02) which makes the probe suitable for pH determination in the physiological range. Thus prepared water soluble fluorescent system demonstrate low cytotoxicity to L929 cell lines from 330 μM to 1.3 μM and cell permeability in the lower concentration range. That findings show the high potential of the newly prepared PDI probe for monitoring of pH variations in bio-samples. Graphical abstract Image 1 Highlights • Fluorescent water-soluble perylene diimide pH probe is synthesized. • Probe is configured on the " fluorophore-spacer-receptor " model. • Probe operates via photoinduced electron transfer. • Probe shows low cytotoxicity towards L929 cell line. • Nano sized probe is cell-permeable at 0.001 mg/mL concentration. [ABSTRACT FROM AUTHOR]

Abstract We present here the synthesis of a simple and low-cost Schiff base chemosensor (HL) for selective detection of both Zn(II) and Cu(II) ions in HEPES buffer pH = 7.4. The chemosensor HL exhibits quick response through fluorescence and colorimetric changes for both Zn(II) and Cu (II) ions as examined by fluorescence and absorption titrations. Both the metal ions form 1:1L– Zn(II) (complex 1) and 1:1L– Cu(II) (complex 2) complexes, confirmed by Job's Plot. We are successful to elucidate the structure of complex 1 through X-ray diffraction analysis. Reversibility of the chemosensor in its binding with Zn(II) and Cu (II) ions separately is also examined in presence of Na 2 EDTA solution. The enhancement of fluorescence intensity of the chemosensor is based on the chelation-enhanced fluorescence (CHEF) effect of L–Zn(II) with the inhibition of both photoinduced electron transfer (PET) effect and C˭N isomerization in excited state and the quenching effect is due to the paramagnetic nature of Cu(II) to the L–Zn(II) system. Furthermore, the geometry and spectral property of HL and both the metal complexes have been studied by DFT, TD-DFT calculations. The limit of detection (LOD) values of both the ions are 2.29 × 10-9 M and 3.67 × 10-9 M, respectively. These values clearly suggests that HL is a promising chemosensor in monitoring Zn(II) and Cu(II) ions in the biological and environmental study with excellent accuracy and precision. The propensity of the chemosensor to detect intracellular Cu(II) and Zn(II) ions in Candida albicans cell lines by fluorescence imaging is also demonstrated in this study. Furthermore, molecular logic gates have been developed based on the idea where chemically encoded information as the input is converted into fluorescent signals as the output. In this work, the designed fluorescent chemosensor exhibits dual logic gates (XOR, AND) involving Zn(II), Cu(II) and Na 2 EDTA. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Abstract A new naphthalene-quinoline based chemosensor L was prepared and structurally characterized. L exhibited excellent selectivity and sensitivity to Al3+ through distinct fluorescence enhancement (335-fold) and ratiometric detection in DMF/H 2 O (v/v, 1/9) based on the combined mechanisms of ESIPT and CHEF. The recognizing behavior of L toward Al3+ had been investigated in detail through Job's Plot, FT-IR, HNMR, and HRMS analysis. The limit of detection (LOD) for Al3+ was as low as and 3.67 × 10−8 M. L was successfully applied in real sample detection and construction of molecular logic gate. Moreover, L was verified to be of low cytotoxicity and good imaging characteristics for the detection of Al3+ in cells HSC. Graphical abstract Unlabelled Image Highlights • A naphthalene-quinoline based chemosensor L was prepared and structurally characterized. • L exhibited excellent selectivity and sensitivity to Al3+ through fluorescence enhancement (335-fold) and ratiometric detection. • The limit of detection (LOD) for Al3+ was determined as 3.67 × 10−8 M. • L was successfully applied in the detection of Al3+ in cells HSC. [ABSTRACT FROM AUTHOR]

The silver ions (Ag + ) and hydrogen sulfide (H 2 S) play extremely an important role in the organism and the environment, while there lack a novel probe with biodegradability, good water solubility, and good biocompatibility to detect Ag + and H 2 S individually. Herein, a novel fluorescence chemosensor DP (Dansyl-Leu-Leu-Cys-Acp-Asp-OH) based on biomolecular peptide has been designed and synthesized, which can be used in the detection of intracellular and environmental Ag + and H 2 S. The DP exhibited high selectivity and sensitivity, excellent cell permeation, biodegradability, good water solubility, and pH insensitivity over a biologically relevant range, with detection limits of 61.7 nM and 74.0 nM for Ag + and H 2 S, respectively. This work can inspire the design of multi-functional fluorescence sensor based on beacon peptides by modifying lateral and terminal groups for imaging applications in physiological and pathological events. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • RBPTA is used as a chemosensor for selective and quantitative detection of palladium with a quite low limitation as 4.22 nM. • RBPTA is highly selective to palladium without interference from other cations. • RBPTA displays quick response (20 min) toward palladium. • RBPTA can be utilized as a fluorescent probe for the detection of palladium in living cells (HeLa cells). • RBPTA can be made as a test paper to ration detect for palladium. Abstract A colorimetric rhodamine-based fluorescent probe RBPTA has been designed to detect Pd2+ under mild condition (pH > 4) in aquenous solution and living HeLa cells. The probe displays high sensitivity (DL 4.2 nM), selectivity and quick response (20 min) toward Pd2+, driven by a PET process. [ABSTRACT FROM AUTHOR]

A series of naphthalene carbohydrazone based fluorescent chemosensors L 1 -L 4 were developed for the detection of Zn 2+ by significant fluorescence enhancement. The binding ratio of the L 1 -Zn 2+ complex was determined by a Job’s plot to be 1:1 and confirmed by ESI–MS studies. The corresponding of the L 1 -Zn 2+ ensemble was elucidated through X-ray crystallography along with spectroscopic studies. Furthermore, the L X -Zn 2+ (X   =   1–2) complexes can specifically detect pyrophosphate (PP i ) in HEPES buffer solution through fluorescence quenching. The detection limit of L X -Zn 2+ (X   =   1–2) for PP i sensing were calculated to be as low as 2.54 ppb and 0.94 ppb, respectively. In addition, due to their good cell membrane permeability and low cytotoxicity, L 1 -L 4 have been applied to sequentially detect Zn 2+ and PP i in living cells. More importantly, the electronic effect of substitute groups on fluorescence signaling have been studied by substituent properties ranging from electron-donating to electron-withdrawing, which sets up a promising strategy for the rational design of fluorescent sensors. [ABSTRACT FROM AUTHOR]

A rationally designed Schiff base chemosensor (L) could render specific detection of Al 3+ ions with two distinct turn-on emission signals, separated by over 100 nm upon excitation at two different wavelengths. The utility of the probe lies in facilitating sensing in 80% aqueous medium with an emission close to 600 nm via an intramolecular charge transfer (ICT) mechanism. The biocompatible and cell permeable probe could readily sense Al 3+ in live HeLa cells as well. The affinity of the probe for Al 3+ could be leveraged to specifically study DNA- Al 3+ interaction in solution. [ABSTRACT FROM AUTHOR]

A new benzimidazole base turn-on fluorescent and ratiometric absorption chemosensor (L) bearing bidentate ligand for detection of Cu 2+ was designed and synthesized. Fluorescence and UV–vis spectra studies demonstrated that L can detect Cu 2+ ions in aqueous solution using fluorescence enhancement and ratiometric absorption sensing over a wide pH range. Both fluorescent and ratiometric absorption sensing of L for Cu 2+ possessed high selectivity and sensitivity over other competitive metal ions and had low detection limit. Job's plot, mass spectra and DFT calculation indicated the sensing mechanism is the complex formation between L and Cu 2+ with 1:2 stoichiometry. Fluorescence images of HepG2 in the absence and presence of Cu 2+ displayed L had cell permeability and detection ability for Cu 2+ in live cells. [ABSTRACT FROM AUTHOR]

A novel pyrrole fused coumarin based simple and practicable molecular probe has been synthesized under metal free green conditions which can recognize copper (II) in acetonitrile solvent. The synthesized probe displayed fluorescence quenching through selective binding with Cu 2+ over other competitive metal ions. Job’s plot, 1 H NMR titration and Mass spectral study revealed that the most abundant species formed when metal to ligand ratio was 1:1. The limit of detection (LOD) for Cu 2+ was found to be 11.3 nM or 2 ppb which is significantly lower than the maximum contaminant level (1.3 ppm of Cu), according to United State Environmental Protection Agency (USEPA). The fluorescent sensor was highly cell permeable and illustrated fluorescence ‘Turn-Off’ in presence of Cu 2+ ions in fluorescent imaging of human cervical cancer (HeLa) cell. [ABSTRACT FROM AUTHOR]

A rationally designed chemosensor L1 (2-(2-amino-4,5-dihydrothiazol-4-yl)-5,5-dimethylcyclohexane-1,3-dione) is capable for the detection of biologically important Cu 2+ and Fe 3+ ions. The observable change in absorbance and emission in HEPES buffer solution and binding parameters display notable sensing ability of Cu 2+ and Fe 3+ ions. From Job’s plot and ESI-MS spectra, 1:1 stoichiometric complexation with Cu 2+ and Fe 3+ ions have been established. The chemosensor was also utilized to develop logic gate by reversibility cycles for Fe 3+ ion by EDTA. In addition, complex formation between the receptor and Cu 2+ /Fe 3+ ion was investigated by spectroscopically and computational studies. The cell imaging study indicated that L1 is highly efficient for the detection of Fe 3+ ion in live cells. The simple synthetic route, multi-stimuli response, regenerative action and solution visualization of the proposed chemosensor potentially make it as excellent sensor for real samples. [ABSTRACT FROM AUTHOR]

Early and simple detection of aberrant cooper metabolism in diseases with neurological-manifestations and several other conditions, including cancer, becomes an urgent necessity. Instrumental methods used today are limited to high-cost equipment and reagents and demand highly qualified personnel. In this work, we report easy-to-use and cost-effective nano-sized sensors for the selective and quantitative detection of copper ion based on fluorescence quenching. Glutaraldehyde cross-linked albumin nanoparticles with tunable ultraviolet-to-red autofluorescence emissions are developed as dual-agents for sensing and imaging. These albumin nanoparticles show great selectivity towards copper ion when tested against a selection of biochemical components and other metal ions, and a limit of detection as low as 1.9 μM, relevant for sensing in clinical diagnosis, was determined. In addition, a lack of toxicity and good cellular uptake were observed and the ultraviolet-to-red intrinsic fluorescence of the albumin nanoparticles was preserved when tested in vitro on NIH:OVCAR3 cell line. Preliminary studies confirm the albumin nanoparticles' ability to detect Cu2+ in vitro and establishes their potential for future practical use. • Multifunctional nanoparticles with tunable ultraviolet-to-red autofluorescence • Simple and sensitive sensors for cooper ion detection at 5 excitation wavelengths • Label-free fluorescent contrast agents • Investigation of absolute fluorescence quantum yields • In vitro confocal microscopy confirm the preservation of tunable intrinsic emission [ABSTRACT FROM AUTHOR]

[Display omitted] • The near-infrared (NIR) turn-on fluorescence probe (aza-BDP-Pro) based on aza-BODIPY derivative was prepared for detecting Au3+ ions. • Aza-BDP-Pro probe can detect Au3+ with a low detection limit in aqueous solution. • The probe showed a remarkable fluorogenic change under UV light. • Aza-BDP-Pro was acceptable applied as an intracellular Au3+-tracking agent in living human cells. A new near-infrared (NIR) fluorescent probe for the determination of Au3+ ions was synthesized by introducing boron dipyrromethene moiety as a fluorophore and attaching it with propyne groups as a Au3+-specific recognition unit. The photophysical properties revealed that the fluorescent emission of the sensor was observed in the NIR region with a wavelength of 713 nm. Furthermore, the sensor exhibited excellent sensitivity to Au3+ ions with fluorescent enhancement behavior in aqueous media and naked-eye observation through a colorimetric change from green to yellow. The detection limit of aza-BDP-Pro was found to be 0.64 µM (0.126 ppm). The probe was successfully utilized for selectively detecting Au3+ ions against other 18 interfering metal ions and tracking Au3+ ions in vivo for imaging application. [ABSTRACT FROM AUTHOR]

[Display omitted] • A chemosensor probe HL based on pyrimidine was designed and synthesized. • The chemosensory behaviour of HL was determined by fluorescence spectroscopy. • HL was found to selectively recognise Zn+2 ions over other metal ions. • The probe HL showed a low detection limit (LOD) of 0.4 nM for Zn2+. • For cell imaging and sensing Zn2+-induced PrP (106–126) aggregation, HL was used. Zinc is one of the most vital components of the living system and is also involved in promoting various neurodegenerative diseases. Therefore, direct monitoring of Zn2+ in biological systems is essential for human well-being. In this work, a chemosensor probe (HL) based on pyridine was synthesised, characterised, and reported for its highly efficient recognition of the zinc ions. The chemosensing behaviour of HL was determined by fluorescence spectroscopy. The probe was extremely sensitive for Zn2+, with an intensity enhancement of over 80-fold and a low detection limit (LOD) of 4 × 10-10 M (0.4 nM), which is remarkably low. In the presence of Co2+, Cr3+, and Cu2+ metal ions, HL shows fluorescence quenching, probably due to their paramagnetic nature. This chemosensor probe was used for applications in cell imaging and sensing of the Zn2+-induced prion (PrP 106-126) peptide aggregation. [ABSTRACT FROM AUTHOR]

A potential fluorescent probe, N'-acetyl-2-((4-methyl-2-oxo-2H-chromen-7-yl)oxy)acetohydrazide (HMC1) was designed on the basis of photoinduced electron transfer (PET) and synthesized using cheap starting materials. HMC1 was found to be highly efficient as a Cu 2+ ion quencher with a detection limit of 0.64 μM (~ 40 ppb). The binding mode of HMC1 towards Cu 2+ was evaluated by 1 H NMR, LC-MS and FT-IR techniques. In addition, cellular imaging studies further exhibited that HMC1 could be used an intracellular turn-off fluorescent chemosensor for Cu 2+ in living cells. [ABSTRACT FROM AUTHOR]

An effort of a new Schiff base macrocyclic chemosensor, 1 4 ‑methyl‑2,6,8,12,14,18‑hexaaza‑1,7,13(1,2),4,10,16(1,4)‑hexabenzenacyclooctadecaphane‑2,5,8,11,14,17‑hexaene (me1) and 1 4 ,7 4 ‑dimethyl‑2,6,8,12,14,18‑hexaaza‑1,7,13(1,2),4,10,16(1,4)‑hexabenzenacyclooctadecadecaphane‑2,5,8,11,14,17‑hexaene (dm2), which enables selective sensing of Al 3+ in aqueous DMF were synthesized by a simplistic one-step condensation reaction of macrocyclic compounds. The probe me1 and dm2 characterized by elemental analysis, FT-IR, 1 H and 13 C NMR, LC-MS spectral techniques. The compounds as mentioned above subjected to FE-SEM with EDS and elemental color mapping. On addition of Al 3+ , the fluorescent probe me1 and dm2 induces turn-on responses in both absorption and sensing spectra by a PET mechanism. The receptor me1 and dm2 serve highly selective, sensitive and turn-on detection of Al 3+ . Further, they did not interfere with other cations present in biological or environmental samples. The detection limit is found to be 3 μM and 5 μM. From the view of cytotoxic activity, the ability of these compounds me1 and dm2 to inhibit the growth of KB cell lines examined. The chelating functionality of compounds me1 and dm2 examined for their inhibitory properties of KB cell, live cell images. The compounds me1 and dm2 subjected to theoretical studies by DFT-B3LYP invoking the 6-31G level of theory. The energy of the HOMO and LUMO has been established. [ABSTRACT FROM AUTHOR]

A new chemosensor based on coumarin FB has been designed and synthesized for the detection of Fe 3+ and PPi. FB displayed a high affinity to Fe 3+ in the presence of other competing cations. The resulting FB -Fe 3+ complex displayed highly sensitivity to PPi via Fe 3+ displacement approach. The Fe 3+ and PPi recognition processes is rapid and reversible, the detection limits of FB to Fe 3+ and FB -Fe 3+ complex to PPi were estimated to be 8.73 × 10 −8  M and 1.25 × 10 −8  M, respectively. The good biocompatibility of FB enables the investigation of fluorescent response for Fe 3+ and PPi in living cells by confocal microscope. A B3LYP/6-31G(d,p) basis set was employed for optimization of FB and FB -Fe 3+ complex. [ABSTRACT FROM AUTHOR]

A new simple aminohydantoin-based fluorescent chemosensor 1 was designed for sequential detection of Zn 2+ and pyrophosphate in a near-perfect aqueous solution. 1 exhibited significant fluorescence intensity in the presence of Zn 2+ , and the resulting 1 -Zn 2+ complex showed subsequently the fluorescent quenching with pyrophosphate. The detection limit (0.32 μM) of 1 for Zn 2+ was far lower than the guideline of World Health Organization in drinking water. 1 was used to determine Zn 2+ concentration in various water samples. In addition, chemosensor 1 could be applied to sequentially detect Zn 2+ and pyrophosphate in living cells and zebrafish. The sensing mechanism of Zn 2+ by 1 was proposed to be an intramolecular charge transfer with theoretical calculations. [ABSTRACT FROM AUTHOR]

A simple and effective fluorescence “turn on” chemosensor (ZPA) has been synthesized for rapid, sensitive and selective detection of copper ions (Cu 2+ ) in fully aqueous buffer. The binding interaction between ZPA and Cu 2+ was investigated through UV–vis absorption, fluorescence measurement, mass spectroscopy, and IR spectrum analysis. Cu 2+ could specifically bind with the hydroxyl-O and imine-N atom in ZPA with high affinity ( K a  = 6.08 × 10 7  M −1 ). Coordination of Cu 2+ to ZPA restricting the photoinduced electron transfer (PET) process in free ZPA and generating a more rigid ZPA/Cu 2+ complex with an extended π-electron conjugation system, sequentially leading to the fluorescence enhancement of ZPA. The detection limit (calculated to be 1.49 × 10 −8  M) was far below the limit in the World Health Organization (WHO) guidelines for drinking water (30 μM) and the sensing process was fully reversible. Practical applications of ZPA for Cu 2+ detection in real water samples were investigated with satisfactory results. Endowed with attributes like high binding affinity, specificity, relatively long excitation/emission properties and excellent bio-compatibility, ZPA demonstrated outstanding fluorescent imaging of intracellular Cu 2+ in living cells. [ABSTRACT FROM AUTHOR]

A probe, quinoline-2-carboxylic acid (4-oxo-4H-chromen-3-ylmethylene)-hydrazide, (HL), acts as selective and specific fluorogenic sensor to Al +3 in the visible light (435 nm) excitation in presence of biologically available large number of cations and emission appears at (λ em ) 520 nm. The limit of detection (LOD) for Al +3 is 7.6 nM in aqueous medium which is less than 10 −3 times of WHO recommended data (7.41 mM). The Job’s plot and mass spectral data support 1:1 composition of the complex [Al(HL)(OH)H 2 O](NO 3 ) 2 . The strongly emissive complex turns off upon addition of F − and is detected at the level of (LOD) 7.4 nM. Thus, F − , a harmful water pollutant, could be identified at much lower level of WHO recommended toxic limit (3.68 μM). The absorption and emission spectral features of HL and its Al +3 -complex have been explained by DFT computation of optimized geometries and calculation of molecular functions. The devised receptor is non-toxic and has been used in detecting Al +3 in the intracellular region of African green monkey kidney cells (Vero cells) and exhibits an INHIBIT logic gate with Al +3 and F − as chemical inputs by monitoring the emission mode at 520 nm. [ABSTRACT FROM AUTHOR]

Cellular free copper ion is essential yet potentially toxic to living orgasms, thus cells have evolved mechanisms to balance global copper content including the chelation reactions by cysteine. To better understand the delicate counter-balance of free copper(II) ion and cysteine in the living cells, we developed a water-soluble naphthalimide-based derivative NC as a chemosensor for reversible dual detection of copper(II) ion and cysteine. The chemosensor NC exhibits a rapid, sensitive and quantitative response for copper(II) ion in aqueous solution due to the formation of the corresponding complex NC -Cu(II) in the range of 0–5 μM with the detection limit of 7.11 nM. Afterwards, NC is released from NC -Cu(II) complex accompanied with a “turn-on” fluorescence in the presence of cysteine ranging from 0 to 160 μM. It's also worth noting that the linear range of the NC -Cu(II) complex for the cysteine is identical with the intracellular level of cysteine under physiological conditions (30–200 μM). To achieve its practical application, we further demonstrated that the chemosensor NC exhibits good cell permeability and could be employed to monitor free copper(II) ion and cysteine in the living cells. [ABSTRACT FROM AUTHOR]

Herein, a new water soluble Ca 2+ fluorescence chemosensor based on aggregation-induced emission (AIE) characteristics has been developed, combining the AIE effect of tetraphenylethylene (TPE) and the complexation capability of bidentate pyridine carboxylate. The bidentate pyridine carboxylate group provides the chemosensor with good water-solubility which is important for detection in biological systems. This chemosensor L showed high selectivity for Ca 2+ by a turn-on response in almost pure aqueous solution with a detection limit of 51.2 nM. L can be used as a recyclable Ca 2+ fluorescent chemosensor in the presence of EDTA. Moreover, the chemosensor L was successfully applied to imaging detection and real-time monitoring of Ca 2+ in living cells with low toxicity and good membrane permeability. [ABSTRACT FROM AUTHOR]

The development of sensitive chromogenic chemosensors for sensing Cu 2+ has been receiving much attention in recent years because of their potential application in clinical biochemistry and the environment studies. Numerous chemosensors have been developed for selective recognition of different species on the basis of host–guest interactions such as hydrogen-bonding, electrostatic force, metal–ligand coordination, hydrophobic and van der Waals force of interactions. The simple and rapid sensing of Cu 2+ ions in biological and environmental systems is desirable and the development of selective and sensitive imaging tools capable of monitoring Cu 2+ ions rapidly has attracted considerable attention. Fluorescent chemosensors have served as useful tool for detecting metal ions owing to their intrinsic sensitivity, selectivity and capacity for rapid, real-time monitoring. Small-molecule fluorescent probes can make use of selective, bio-orthogonal chemistries to report on specific analytes in cells and in more complex biological specimens. This review presents a survey of strategies for using small-molecule fluorescent probes to detect Cu 2+ ions which cover UV to NIR regions such as anthracene, pyrene, quinoline, quinazoline, dansyl, naphthalimide, rhodamine, fluorescein, BODIPY and cyanine dyes. [ABSTRACT FROM AUTHOR]