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[Display omitted] • Highly fluorescent N, B-doped CNDs discerning interactions with Fe(II) and Fe(III). • The "urn-Off" optical probe relies on a concentration-dependent fluorescence decrease. • The N, B-doped CNDs are selective towards Fe(II) ions in the presence of other metals. • The CNDs can monitor Fe(II) presence in living cells by fluorescent imaging. The interactions between metal ions and fluorescent probes are fundamentals for discerning the metal ions. Co-doped carbon nanodots (CNDs) have demonstrated the capacity to optically detect a wide variety of targets, including metal ions. In this work, the quenching of highly fluorescent, nitrogen (N) and boron (B) co-doped CNDs by Fe(II) ions was discovered and employed to differentiate Fe2+ in water samples and live cells. The fluorescence of the N,B-CNDs was quenched in a concentration-dependent manner with a need of very short reaction time (30 s), and the CNDs show good selectivity towards Fe(II) ions relative to other metal ions including Fe(III). The limit of detection (LOD) was calculated as 1.8 nM and the linear response range was 7 nM to 1 μM. The recovery percentage was determined to be 97%, 101%, and 103% for spiked Fe(II) concentrations of 31, 125, and 1000 nM, respectively, in tap water. The N,B-CNDs were able to monitor the presence of Fe(II) in living cells using the optical imaging of Fe(II) ions, and the quenching in cells was completed within one hour. Regarding the quenching mechanism, the photoinduced electron transfer (PET) procedure is proposed with support of cyclic voltammetry study on the CNDs upon addition of Fe(II). Overall, the N,B-CNDs promise as optical probes for the detection of Fe2+ in water and living cells, and demonstrated a satisfactory level of sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

A simple julolidine based chemosensor (JT) was designed and synthesized by single condensation step. JT displayed excellent selectivity and sensitivity with on-off responses towards Zn2+ and Cu2+ over other biologically relevant metal ions in aqueous media. Upon addition of Zn2+ ions, JT exhibited a significant blue shift in emission followed by turn- on enhancement while with Cu2+, the fluorescence intensity of JT was completely vanished. The 1:1 binding affinity between JT and Zn2+/Cu2+ was proposed by Job's plot analysis. The detection limit for Zn2+ and Cu2+ ions reached at 3.5 × 10−8 M and 1.46 × 10−6 M, respectively. The sensing mechanism of JT with Zn2+/Cu2+ was supported by DFT calculations. Based on photophysical studies and its reversibility environment with EDTA, molecular logic gates were fabricated. Furthermore, JT was successfully established to detect intracellular Zn2+ ions in live cells by turn-on response. A bifunctional chemosensor JT was synthesized to distinguish Zn2+ and Cu2+ ions based on emission on-off response. Unlabelled Image • New julolidine based Schiff base derivative (JT) was designed and synthesized and JT served as a selective emission on-off response towards Zn2+ and Cu2+ ions. • The sensor shows excellent sensitivity for Zn2+ and Cu2+ ions with an LOD at 3.5 × 10 -8 M and 1.46 × 10 -6 M, respectively. • The 1:1 binding model of the sensor JT with Zn2+/Cu2+ was established and reversibility of the chemosensor JT was proved by experiments with EDTA. • JT was successfully established to track intracellular Zn2+ ions in HeLa cells. [ABSTRACT FROM AUTHOR]

A new easily available “off-on-off” colorimetric and fluorescent probe ( L ) was synthesized and it displayed the selective detection towards Hg 2+ in aqueous solution over other competing metal ions. In presence of Hg 2+ , L showed the incredible color and fluorescent response. More interestingly, the color and fluorescence could be recovered upon the addition of EDTA into the L-Hg 2+ solution. Moreover, this compound can be efficiently applied to molecular logic functions of OR, AND, NOR and NOT gates through the procured spectral results. Based on the reversible and reproducible switching process, we designed a molecular-scale sequential memory unit exhibits the “Writing-Reading-Erasing-Reading” and “Multi-write” activities in the form of binary logic. Density Functional Theory (DFT) calculations were theoretically supported the photo physical changes. Furthermore, the probe efficacy was studied by monitoring changes in intracellular Hg 2+ ions in HeLa cells. [ABSTRACT FROM AUTHOR]

In this communication, we have developed an optical chemosensor 2-amino N-(6-bromo-1,3-dioxo-1H-benzo[ de ]isoquinolin-2(3H)-yl)benzamide ( NAPH ) for selective detection of Al 3+ by reacting 4-bromo-1,8-naphthalic anhydride with 2-aminobenzohydrazide. In (DMSO:H 2 O, 1:1, v/v) medium, the selective and specific nature of NAPH towards Al 3+ was observed by the quenching along with a blue-shift in the absorption of NAPH at 465 nm that resulted in the distinct colour change from light brown to colourless. The selective complexation that occurred between NAPH and Al 3+ was investigated by 1 H NMR and DFT methods. Under similar conditions, the weakly fluorescent receptor NAPH showed a distinct fluorescence enhancement at 555 nm in the presence of Al 3+ among the other tested metal ions and anions. The NAPH ·Al 3+ complex formation is reversible upon addition of strong chelating agent EDTA. The receptor NAPH can be applied to detect Al 3+ down to 2.9 μM without any interference from other tested metal ions. In addition, the receptor NAPH was successfully applied to detect Al 3+ in live HeLa cells. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Naphthalene dianhydride based novel probe R1 useful for the detection of Fe+3. • The performance of probe R1 over the other di/trivalent ions. • The PET mechanism on fluorescent turn-on cell permeable probe. • The efficacy of R1 towards live-cells. Abstract A green emissive PET operating fluorescent turn-on cell permeable novel probe R1 has been successfully developed and utilized for the detection of Fe+3 in the pure aqueous system at sub-nanomolar level. Moreover, probe R1 demonstrate highly sensitive and selective towards Fe+3 over the other divalent and trivalent metal ions and was established by using fluorescence spectroscopy. The efficiency and aid of R1 was demonstrated by the fluorescence imaging of captured Fe+3 within Pollen grains by using fluorescence microscopy. These results indicate that, this is the first fluorescent turn-on PET probe to detect sub-nanomolar Fe+3 in the pure aqueous system and in cellular level. [ABSTRACT FROM AUTHOR]

A fluorescein based organic nanoparticles were prepared by using synthesized N -(3′,6′-dihydroxy-3-oxospiro[isoindoline-1,9′-xanthene]-2-yl)-2-hydroxybenzamide(FB). The interaction of series of metal ions with the FB nanoparticles (FBNPs) was investigated by means of fluorescence measurement. The selective and sensitive fluorescence enhancement was observed to FBNPs by the addition of Zn 2+ ion in an aqueous medium. The interaction of FBNPs and Zn 2+ introduced chelation enhanced fluorescence that was unaltered even addition of other metal ion. The formation of excited state complexation of FBNPs-Zn 2+ was supported by UV–vis absorption titration, fluorescence lifetime and zeta particle size of FBNPs with and without addition of Zn 2+ . The mode of binding and interaction was confirmed by results procured through NMR and IR spectroscopy. The stoichiometry and binding constant estimated by Job’s plot and Benesi-Hildebrand plot. The limit of detection (LOD) for Zn 2+ was 0.0011 μg/mL. The fascinating feature of present nano probe (FBNPs) is that outstanding intracellular Zn 2+ sensor in MDA-MB-231 living cells with nominal toxicity. The exceptional photo physical and biocompatible nature of FBNPs signifying on site application of prepared fluorescent organic nanoparticles in environmental as well as biomedical field. [ABSTRACT FROM AUTHOR]

A new, easily accessible “off-on-off” colorimetric and fluorescent probes are designed and synthesized. It displayed highly selective and sensitive detection towards Cu 2+ ion without having any interference from other competitive metal ions. The examined UV–vis and fluorescence spectral changes are caused by the operation if the ligand to metal charge transfer (LMCT) and chelation enhanced fluorescence effect (CHEF) in the presence of Cu 2+ to the present probes. Besides, the density functional theory (DFT) calculations have been theoretically supported the photophysical changes. These probes are potentially applied in an analytical application for detecting the trace amount of Cu 2+ ions in real water samples. Furthermore, these probes are successfully applied for fluorescence imaging of Cu 2+ in HeLa cells. Finally, the use of test strips based on these probes is fabricated, which could act as a convenient and efficient Cu 2+ test kit in solution medium and supported on solid medium (silica). [ABSTRACT FROM AUTHOR]

A novel coumarin based azo-phenol ligand (H 2 L) has been synthesized and characterized by several spectroscopic techniques. An almost 16 fold enhancement of emission intensity has been observed upon gradual addition of Mg 2+ to H 2 L in DMSO:H 2 O (1:5 v/v) medium while it has no significant effect in emission intensity even in presence of other metal ions. The emission intensity of L-Mg 2+ complex has almost quenched on gradual addition of F − to it. The limit of detection for both Mg 2+ and F − are of 10 −8 M order, hence the newly developed chemosensor is highly efficient in detecting Mg 2+ and F − in very minute levels. The chemosensor can even detect Mg 2+ in the intracellular region of human lung cancer cells (A549 cells). [ABSTRACT FROM AUTHOR]

A highly sensitive and selective coumarin based chemosensor H 2 L for the efficient detection of Al 3+ has been developed. The synthesized chemosensor H 2 L is efficient in detecting Al 3+ over other metal ions which are commonly obtained in various physiological and environmental samples. H 2 L shows fluorescence ‘turn-on’ response at 610 nm in presence of Al 3+ , without the interference of other metal ions. The resulting H 2 L-Al 3+ complex behave as a sequential chemosensor for F − , by showing quenching of emission intensity upon addition of F − to it. This quenching of emission intensity is only specific for F − and is not hampered due to the presence of other anions that commonly coexist with F − in various environmental solutions. Theoretical calculations using DFT/B3LYP method has been used to get insight into the sensing mechanism as well as electronic structure of the synthesized chemosensor H 2 L. H 2 L is efficient in detecting Al 3+ in the intracellular region of human A549 cell and also exhibits an INHIBIT logic gate with Al 3+ and F − as chemical inputs by monitoring the emission mode at 610 nm. [ABSTRACT FROM AUTHOR]

A novel fluorescent BODIPY-rhodamine dyad probe that operates based on through bond energy transfer (TBET) phenomenon has been synthesized and its application in the detection of biologically relevant metal ions is explored. Among several metal ions, the probe selectively responds to the addition of trivalent metal ions (Al 3+ , Cr 3+ and Fe 3+ ) through its signature absorbance and fluorescence characteristics and permits their ratiometric detection. The trivalent metal ion detection ability of the probe is unaffected with the presence of other commonly coexistent ions. The probe is highly sensitive and it can detect the trivalent metal ions even at ppb level concentrations. The probe is nontoxic under the experimental conditions, cell permeable and useful for the imaging of Al 3+ , Cr 3+ and Fe 3+ ions present in W138 (normal lung fibroblast) cells. [ABSTRACT FROM AUTHOR]

In this study, we developed organelle-specific blue-emitting two-photon (TP) probes for Ca2+ (BCa-1 , BCa-2 mito , and BCa-3 mem), with absorption maxima (λ max) at 350–358 nm, emission maxima (λ fl) at 464–466 nm, and TP action cross-section (Φδ max) values of 55–70 × 10−50 cm4s/photon, in the presence of excess Ca2+ at 750 nm. Moreover, the probes had dissociation constants of 0.18, 2.7, and 100 μM, respectively, which are appropriate values for sensing Ca2+ in the cytoplasm, mitochondria, and plasma membrane, respectively. The measurements were conducted using a calcium calibration buffer (10 mM 3-[ N -morpholino]propanesulfonic acid and 100 mM KCl) at pH 7.2. The TP microscopy results revealed that the probes could facilitate the real-time detection of Ca2+ in the cytoplasm, mitochondria, and plasma membranes of live cells and tissues. Additionally, we developed a green-emitting TP probe for H+ (FHEt-1 lyso) with λ max = 359 nm, λ fl = 571 nm, and Φδ max = 70 × 10−50 cm4s/photon at pH 4.3 in a universal buffer (0.1 M citric acid, 0.1 M KH 2 PO 4 , 0.1 M Na 2 B 4 O 7 , 0.1 M tris[hydroxymethyl]aminomethane, and 0.1 M KCl); this probe could detect H+ in the lysosomes. Using BCa-1 and FHEt-1 lyso , it was possible to simultaneously monitor the changes in cytosolic Ca2+ and lysosomal H+ concentrations in live cells and tissues using dual-color TP microscopy in real time. When used with TP probes emitting wavelengths of green light or longer, these blue-emitting Ca2+ probes can be used to investigate the physiological role of Ca2+ in cellular organelles as well as the crosstalk between Ca2+ and other metal ions in specific organelles. [Display omitted] • We developed organelle-specific blue-emitting two-photon Ca2+ probes. • They can detect Ca2+ in organelles of living cells and tissues in real-time. • They have appropriate K d values for Ca2+ for each organelle. • They show high sensitivity, low pH dependency, and negligible cytotoxicity. • They can monitor the crosstalk among metal ions using multicolor TPM imaging. [ABSTRACT FROM AUTHOR]

A novel fluorescein-rhodamine dyad probe has been synthesized and its chemosensory applications are explored. Anion and cation specific responses of the probe permit ratiometric detection of Hg 2+ and fluoride ions, individually and collectively, with different fluorescence outputs. The presence of other commonly coexistent ions does not affect the Hg 2+ and fluoride ion detection ability of the probe. The probe is highly sensitive to Hg 2+ and fluoride ions and it can detect Hg 2+ and fluoride ions even at ppb level concentrations. The probe is non-toxic under the experimental conditions, cell permeable and useful for the imaging of intracellular Hg 2+ and fluoride ions. [ABSTRACT FROM AUTHOR]

A rhodamine-based optical sensor Rh–3S has been developed for selective detection of Hg 2+ in aqueous solution as well as in living cells. UV–vis and fluorescence spectroscopic studies reveal that Rh–3S shows marked sensitivity and selectivity to Hg 2+ with a chelation-induced “off–on” response in acetonitrile (ACN)/MOPS buffer (10 mM, pH 7.3, v/v, 1:1). The Rh–3S sensor binds Hg 2+ in a 1:1 stoichiometry with an apparent binding constant 3.71 × 10 6 M − 1 (log K = 6.57) and displays a distinct change in color and fluorescence upon the alteration of free Hg 2+ levels in solution with a reversible response and little interference with other biological relevant metal ions. Live cell confocal imaging studies demonstrate that the sensor is also capable of imaging the presence of Hg 2+ ions as well as its dynamic changes in live cells. [ABSTRACT FROM AUTHOR]

Two hitherto unknown coordination complexes have been synthesized and studied using binucleating Schiff base ligand H 3 L. The ligand can selectively detect Mg2+ ions by change in fluorescence behavior. H 3 L is also useful for live cell imaging and in vivo detection of Mg2+ ions. [Display omitted] • One dinuclear CdII and one polynuclear ZnII complexes supported by H 3 L ligand. • Coordination induced formation of bis-oxazoline based macrocyclic ligand. • Chemo-sensing of Mg2+ ion by H 3 L. • Cytotoxicity study of H 3 L and the complexes. • In vivo sensing of Mg2+ by H 3 L through live cell imaging. In the present work, a discrete dinuclear cadmium(II) complex Cd 2 (μ−H 2 L)(μ−OH)Cl 2 ⋅H 2 O (1) and a dinuclear zinc(II) based 1D chain complex ({Zn 2 (L')(O 2 CCH 3)}ClO 4 ⋅3H 2 O) n (2) (where H 3 L = 2,6-bis{2-(2-hydroxyethylamino)ethylimino}methyl-4-methylphenol and H 2 L′ = bis-oxazoline (BOX) ligand), have been synthesized and characterized by single-crystal X-ray crystallography. The Cd2+ ions in the first case showed straight cut incorporation of metal ions within the ligand pockets. In case of zinc(II), the coordination induced oxazolidine ring formation resulted in macrocyclic ligand formation having two adjacent coordination pockets. In complex 2, the acetate ion acts as an O,O linker and joins the Zn 2 nodes bound within the newly formed macrocyclic ligand bearing bis-oxazolidine rings to form 1D polymeric chain at the end. The H 3 L was next screened for its efficacy as selective fluorescence sensor for Mg2+ ions in aqueous MeOH medium. Steady state absorption and emission behaviour of H 3 L, 1 and 2 have been investigated. Time resolved fluorescence properties of H 3 L and the complexes 1 and 2 have been examined, and their lifetimes have been determined in 0.038–0.257 ns range. The cell viability in presence of H 3 L makes it a suitable candidate for application in live cell imaging studies. [ABSTRACT FROM AUTHOR]

A bisphenol based fluorescence "turn-on" chemosensor 4,4′-(propane-2,2-diyl)bis(2-((E)-(2-(benzo[d]thiazol-2-yl)hydrazineyldene)methyl)phenol) (BHMP) has been synthesized and its sensing behavior was tested towards various ionic species. The chemo-sensing behavior of BHMP has been established through absorption, fluorescence, NMR, and mass spectroscopic techniques. The probe BHMP selectively detects zinc ions over other metal ions and the resulting BHMP + Zn2+ ensemble serves as a secondary probe for the detection of pyrophosphate (PPi) anion specifically over other anions. The spectroscopic studies reveal the fluorescence enhancement of BHMP in association with Zn2+ ions was quenched in the presence of pyrophosphate (PPi) anions. A probable mechanism of this selective sensing behavior was described on the basis of "OFF-ON-OFF" strategy for detection of both cations and anions. Moreover, the biological applicability of the chemosensor BHMP was examined via cell imaging studies. A bisphenol based fluorescence "turn-on" chemosensor (BHMP) has been synthesized and its sensing behavior was tested towards various ionic species. The probe BHMP selectively detects zinc ions over other metal ions and the resulting Zn2+-BHMP ensemble serves as a secondary probe for the detection of PPi anion. The biological applicability of the chemosensor BHMP was examined via cell imaging studies. Unlabelled Image • The probe BHMP selectively detects zinc ions and the resulting Zn2+- BHMP ensemble is applied for the detection of PPi ions. • The probe detects Zn2+ and PPi ions with low detection limit of 0.28 and 0.87 nM respectively. • The probe was successfully applied to detect Zn2+ and PPi ions in live cells. [ABSTRACT FROM AUTHOR]

Sensing heavy metal ions particularly for the most toxic Hg2+ is a long-term pursuit for chemists because of its obvious and extreme harmfulness to both the environment and human health. Herein, a novel 'turn-on' perylenebisimide-thiourea fluorescent probe PBI-BTB is achieved for rapid detection of Hg2+ in a DMSO/H 2 O (5/1, v /v) solution through a typical Hg2+-promoting desulfurization reaction, which has been investigated through Job's plot titration, FT-IR, 1H NMR and HRMS analysis. A remarkable fluorescence emission enhancement at 540 and 580 nm is observed in the presence of Hg2+, which is visible to the naked eye with high selectivity and sensitivity. Moreover, probe PBI-BTB combined strong anti-interference recognition with short response time (< 1 min). The rapid fluorescence response with low limit of detection (0.35 μM) in a wide pH range of 3.0–11.0 makes PBI-BTB a promising candidate for detection of Hg2+ without any buffer system. Furthermore, the practicability of probe PBI-BTB upon the Hg2+ recognition in human liver cancer cells (HepG-2) has been studied through fluorescent live cell imaging which reveals the probe's low toxicity to organism as well as the favorable cell permeability of PBI-BTB for detecting Hg2+ in biological systems. Unlabelled Image • A novel fluorescent "turn-on" chemosensor for Hg2+ is developed based on perylenebisimide and thiourea. • The probe exhibited high selectivity and low detection limit for Hg2+ in a wide range of pH without any buffer system. • The probe was suitable for imaging Hg2+ ions in living cells. [ABSTRACT FROM AUTHOR]

An effective morpholine-type naphthalimide chemsensor, N- p -chlorophenyl-4-(2-aminoethyl)morpholine-1,8-naphthalimide (CMN) has been developed as a lysosome-targeted fluorometric sensor for trivalent metal ions (Fe3+, Al3+ and Cr3+). Upon the addition of Fe3+, Al3+ or Cr3+ ions, the probe CMN showed an evident naked-eye color changes which pale yellow solution of CMN turned deepened and it displayed turn-on fluorescence response in methanol. CMN showed a significant selective and sensitive toward Fe3+, Al3+ or Cr3+ ions, while there was no obvious behavior to other monovalent or divalent metal ions from the UV–vis and fluorescence spectrum. Based on the Job's plot analyses the 1:1 coordination mode of CMN with Fe3+, Al3+ or Cr3+ was proposed. The limit of detection (LOD) observed were 0.65, 0.69 and 0.68 μM for Fe3+, Al3+ and Cr3+ ions, respectively. The N-atom of morpholine directly involved in complex formation, CMN emitted fluorescence through inhibition of photoinduced electron transfer (PET). This probe exhibited excellent imaging ability for Fe3+, Al3+and Cr3+ ions in living cells with low cytotoxicity. Significantly, the cellular confocal microscopic research indicated that the lysosome-targeted group of morpholine moiety was introduced which realized the capability of imaging lysosomal trivalent metal ions in living cells for the first time. Unlabelled Image • A "turn–on" chemosensor for trivalent cations was developed. • The probe showed naked-eye color changes for trivalent cations detection. • The logic gate at molecular level was anticipated. • The probe was suitable for imaging lysosomal trivalent cations in living cells. [ABSTRACT FROM AUTHOR]