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The sensor MH-4 has a high sensitivity and selectivity to Cu2+ over a wide range of other metal ions in acetonitrile (ACN)/water (v/v 1:1). The fluorescence imaging studies demonstrated the permeability of MH-4 in L929 living cells and the sensing of Cu2+ in the cells. [Display omitted] • A diformyl phenol based optical sensor (MH-4) was developed for the detection of Cu2+. • MH-4 showed high selectivity and sensitivity Cu2+ over other metal ions/anions tested. • MH-4 can detect Cu2+ at nanomolar level. • Mh-4 is suitable for imaging Cu2+ in living cells. Given the critical role of trace copper ion in human health, its sensitive detection in environmental and biological samples is crucial. We, herein, designed and synthesized a diformyl phenol-based turn-off fluorescent sensor ((5-(tert -butyl)-2-hydroxy-1,3-phenylene)bis (methanylylidene)) bis (azanylylidene)) bis(4-hydroxy-2H-chromen-2-one) (MH-4)) for the spectrofluorometric detection of Cu2+ ion, which has sensitive and selective fluorescence quenching over other competitive metal ions. The efficiency and fast response of the sensor were confirmed by UV–Visible, fluorescence spectral changes, which may be due to the formation of coordination bond between MH-4 and Cu2+ ions. The binding stoichiometry of MH-4 with Cu2+ was examined with the help of UV–Vis and fluorescence titrations, and Job's plot, which gives a 1:1 coordination stoichiometry; this is further confirmed through MS studies. The binding constant of the complex was found to be 9.4 x 107 M−1. Then, the absorbance and fluorescence-based detection limits were calculated to define the sensitivity range of the proposed sensor and were found to be 69.30 nM and 37.40 nM, respectively. Finally, a live cell image study of MH-4 in L929 (murine aneuploid fibrosarcoma) cells was also performed to test the cell permeability of MH-4 and its effectiveness for selective detection of Cu2+ in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • LD-VP emits fluorescence at 520 nm in dioxane and 600 nm in viscous media without any interference from biological entities. • The LD-VP probe is pH-independent. • The quantum yield of probe LD-VP has changed from 0.5 % to 30% as the viscosity rises from 0.9 cP to 953 cP. • Probe LD-VP has provided green images in nonpolar intracellular milieu detection and red images for high viscosity. • Probe LD-VP concurrently labeled mitochondria, lysosomes, and lipid droplets in red and green channels based on intracellular viscosity and polarity. The viscosity and polarity of cells are inherent physical parameters, and changes to these attributes are frequently linked to malfunctioning conditions or different diseases. Cancer cells often harbor elevated nonpolar lipid droplets (LDs), acting as energy reserves. The rise in lipid droplets (LDs) and viscosity, distinctive traits of cancer cells, has motivated us to develop a fluorescent probe based on naphthalimide. The fluorescent marker LD-VP exhibits fluorescence signals at 520 nm in nonpolar dioxane and 600 nm in highly viscous glycerol. This implies that probe LD-VP can furnish details regarding cellular microviscosity and lipid droplets within live cells by providing dual-channel images. The probe LD-VP is chemically inert and harmless, enabling its safe utilization in live cell imaging. We conducted fluorescence imaging based on viscosity using probe LD-VP in the red channel, which is found to be co-localized in both mitochondria and lysosomes. Moreover, the probe effectively marks lipid droplets in the green channel. The probe LD-VP represents a distinctive fluorescent tool capable of monitoring both viscosity and lipid droplet expression in live cells. This tool holds the potential for visualizing physiological abnormalities or pathological conditions. [ABSTRACT FROM AUTHOR]

A novel NIR probe based on oxazolonaphthoimidazo[1,2- a ]pyridine-malononitrile (ONIM) conjugate linked by vinyl linkage was designed and synthesized for the detection of cyanide ion. [Display omitted] • An orange emitting sensor ONIM (712 nm) with D-π-A framework is synthesized. • The ONIM emission is retained in the solid state. • ONIM could sense cyanide ion without interference of other anions. • Sensing mechanism of cyanide sensing was confirmed by 1H NMR and DFT calculations. • Live cell imaging in human breast cancer cell MDA-MB 231 and as solid state sensor was achieved. Cyanide is undoubtedly dangerous and fast acting chemical employed in various industrial applications with toxic side effects, which raises urgent need for its monitoring. In this context, oxazolonaphthoimidazo[1,2- a ]pyridine-malononitrile (ONIM) conjugate linked by vinyl linkage was designed, synthesized and characterised by FT-IR, NMR and mass spectrometry. The developed probe has been evaluated for the colorimetric and fluorometric detection of cyanide ion. An obvious color change with unique rapid " turn-off " fluorometric response was observed within 5 s upon addition of CN– thus reflecting its better acuteness and sensitivity over other competing anions. The developed probe exhibits a detection limit of 9.54 nM which is very low in comparison to maximum permitable amount of cyanide in drinking water (1.9 µM). The probe is stable within the p H range of 2–9 and suitable for the recognition of CN– in the p H range of 7 to 10, specially at neutral p H conditions. The chemodosimetric approach based detection mechanism was authenticated by 1H NMR titration and DFT calculations. The solid state applications were established by utilising ONIM impregnated TLC plates and filter paper in cyanide recognition. The solid state emissive behaviour of ONIM offers on-spot detection of the cyanide anion. Additionally, the practicability of ONIM has been extended in live cell imaging of CN– in human breast cancer cell (MDA-MB-231), which revealed a " turn-off " fluorescence response for the probe in the presence of CN– ion. [ABSTRACT FROM AUTHOR]

[Display omitted] • NIR sensor for high-sensitive and selective detection and removal Cu2+ in living cells and environment. • Phthalocyanine based dual fluorescence and colorimetric sensor. • NIR fluorescence and colorimetric changes through cis- / trans interconversion. • Binding mechanism towards Cu2+were systematically revealed. Cu2+ sensing and removal are of great significance for environment protection and human health. Herein, multifunctional Cu2+ sensor system for both detection and removal of intracellular and environmental Cu2+ based on trans/cis interconversion of silicon phthalocyanine (SiPc) was developed. This phthalocyanine based Cu2+ sensor shows remarkably dual-mode NIR fluorescence and colorimetric responses for recognition of Cu2+, resulting in insoluble chelate for Cu2+ removal as well as the extremely high anti-interference in the presence of various anions and cations. The binding mechanism and stoichiometry ratio were systematically revealed. Intracellular fluorescence imaging in MCF-7 cells demonstrated that Cu2+ could be efficiently detected in living cells and form insoluble chelate for clearance. As the result, this novel phthalocyanine based multifunctional sensor can be used for dual-mode NIR fluorescence/colorimetric detection and removal of Cu2+ in either complicated environment or biological systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • PET based Probe 7 showed selectivity for Hg2+ and H+ ion in phosphate buffer (10 % DMSO). • Probe 7 displayed "turn – On - Off" emission in acidic and alkaline medium • Probe 7 exhibited sensitivity to visualize lysosomes and Hg2+ ion in live cells. • Probe 7 on test paper strips, showed naked-eye sensitive green color with Hg2+. A 1,5–bis(1,4-piperazinyl–naphthalimide– N –ethylmorpholine) pyridine based flexible fluorescence probe 7 is designed, synthesized, and its photophysical behavior has been examined in different media. The photophysical behavior of probe 7 in phosphate (PBS) buffer (10 % DMSO) showed pH sensitivity and selectivity for Hg2+ ion in solution and live cell with a change in naked-eye sensitive visible color. In acidic medium (pH ≤ 6) probe 7 showed enhanced (∼21 fold) "turn–On" emission, while at pH ≥ 7.4 probe 7 remained in the "turn–Off" state. The observed fluorescence "turn–On" response is attributed to inhibition in photoinduced electron transfer (PET) process. Jobs plot analysis revealed a 1:2 stoichiometry for an interaction between probe 7 and Hg2+ ion with good limit of detect (LOD) 5.78 × 10−8 M (57 nM). The reversibility in complexation and the mode of interaction were confirmed by EDTA and through NMR and HRMS spectroscopic data. MTT assay and cell imaging studies showed biocompatibility of the probe 7 to detect lysosomes and Hg2+ ion in A549 cells. For analytical application paper strip test was performed to detect Hg2+ ion with naked-eye sensitive visible color change. [ABSTRACT FROM AUTHOR]

[Display omitted] • Development and spectroscopic identification of a Schiff base HL. • Via turning on fluorescence, HL can be used as a chemosensor to recognize Zn(II) from a variety of competing cations. • Complex 1, synthesized by a simple reaction of HL and Zn(II) shows AIE active behavior in 7:3 water-DMSO medium, confirmed by DLS, SEM, UV, and fluorescence study. • AIE active behavior of complex 1 is utilized to recognize picric acid via turn-off fluorescence in 3:7 DMSO-water medium. • The live cell imaging investigation supports HL and Complex 1′s biosensing behaviours. The present work highlights the development and spectroscopic identification of a Schiff base chemosensor, (Z)-4-bromo-2-(((1-methoxybutan-2-yl)imino)methyl)phenol, (HL), for selective detection Zn(II) via turn-on fluorescence among a number of competing cations in a 9:1 DMSO-water media. The high binding constant value, measured during titration of HL and Zn(II), boosts to conduct a straightforward condensation reaction between HL and Zn(II) which results in solid crystals of Zn(II) complex (complex 1). In 7:3 DMSO-water media, complex 1 display Aggregation Induced Emission (AIE) behavior, as a result of which, with increasing the water percentage, under UV light optically the cyan color complex 1 solution converts to green color with the enhancement of fluorescence intensity. The UV, fluorescence, DLS, and SEM studies, fully approve the probe's AIE active behavior. The AIE active property of complex 1 is implemented to detect picric via turn-off fluorescence. The chelation-induced enhanced fluorescence (CHEF) on and Excited state internal proton transfer (ESIPT) off are the key factors in showing the luminescence property of complex 1 and the distortion of aggregation behavior of complex 1 in the presence of picric acid leads to the turn-off fluorescence of the complex 1 solution. The mass spectral and IR spectral analysis supports the 1:1 stoichiometric addition of the probe and analyte and the structure of the probe-analyte complexes is optimized using density Functional Theory (DFT) study. Finally, the live cell imaging study enables us to independently verify the biosensing behavior of complex 1 and HL towards Zn(II) and picric acid respectively. [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]

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]

[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]

Graphical abstract Highlights • Benzoxazole appended based probe (BS) was designed and synthesized. • BS showed good selectivity towards Zn2+ion with 'turnon' fluorescence emission. • BS-Zn2+ ensemble showed selective sensing towards PPi− ion. • BS and BS-Zn2+ ensemble could detect Zn2+ & PPi ions in live cells. Abstract A novel benzoxazole appended dipodal Schiff base (BS) was synthesized and its sensing property was investigated. The receptor BS detected Zn2+ ions selectively by turn-on fluorescence among the wide range of metal ions in DMSO-H 2 O (1:9 v/v, 50 mM HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) at pH 7.4. The different physicochemical parameters of BS-Zn2+ complex were investigated by UV–vis, photoluminescence, 1H NMR titration and ESI-MS techniques. The limit of detection (LOD) and binding constant (K b) of BS-Zn2+ complex have been determined by fluorescence titrations and found to be 4.53 × 104 M−1 and 0.52 μM. Moreover, binding ratio of BS and Zn2+ was found to be 1:1 by Job's method. Further, the BS–Zn2+ complex was used to sense pyrophosphate (PPi) ions as a secondary sensor in HEPES buffer solution. Overall, the sensitive fluorescence behavior of the receptor BS has been utilized as a powerful tracker for zinc ion and pyrophosphate ion in biological systems. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel fluorescent probe for biothiols detection. • Red fluorescence with emission maxima at 640 nm and a large Stokes shift of 160 nm. • High sensitivity and selectivity. • The sensing mechanism was studied by MS and HPLC. • Endogenous biothiols imaging in living MCF-7 cells. Abstract Small molecule biothiols, including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), play important roles in physiological and pathological processes, which are related to many diseases. Hence the detection of cellular biothiols is of great significance. Here we reported a new probe DNT that was constructed by a donor-acceptor type dye NT-OH and a recognition site DNBS group. DNBS group also acted as a fluorescence quencher in this molecule. While in the presence of biothiols, the DNBS group reacted with the sulfydryl group of thiols by nucleophilic aromatic substitution reaction and then eliminated from the probe, turning on the red fluorescence of the probe with emission maxima at 640 nm and a large Stokes shift of 160 nm. Solution experiments revealed that DNT showed high sensitivity and selectivity to biothiols. Besides, it was further utilized to map endogenous biothiols in MCF-7 cells successfully. [ABSTRACT FROM AUTHOR]

Graphical abstract Nano-molar level optical detection of Zn2+ is established by spectroscopic techniques and confirmed by single crystal X-ray structures of resulting Zn2+ complexes. Intra-celullar Zn2+ imaging in HeLa and MDA-MB-468 cells have been achieved. DFT studies unveil the energy parameters involved in probe- Zn2+ interaction. Highlights • Single crystal X-ray structural evidence of Zn2+ binding. • Nano-molar level optical detection of Zn2+ in aqueous medium. • Intra-celullar imaging of Zn2+ in HeLa and MDA-MB-468 cells. • DFT studies unveil the energy parameters involved in probe- Zn2+ interaction. Abstract Two simple probes, derived by condensation of ethylenediamine with 3-ethoxysalicylaldehyde (L) and salicylaldehyde (L1) have been exploited for selective recognition of Zn2+. The interaction between probes and Zn2+ has been established by spectroscopic techniques and confirmed by single crystal X-ray structures of the resulting Zn2+ complexes. It is proposed that Zn2+ inhibits the PET process, originally responsible for non-emissive nature of free ligand and turns the fluorescence ON through CHEF process. The L and L1 probes respectively detect as low as 1.8 nM and 1.16 nM Zn2+, while corresponding binding constants are 2.9 × 106 M−1 and 4.57 × 105 M−1. L1 is very effective for intra-celullar imaging of Zn2+ in HeLa and MDA-MB-468 cells. The density functional theoretical studies unveil the energy parameters involved in the probe-Zn2+ interaction process. [ABSTRACT FROM AUTHOR]

A novel photochromic diarylethene 1O composed of a N'-(quinolin-8-ylmethylene)benzohydrazide group as the binding unit for metal ions and perfluorodiarylethene as a photoswitching trigger has been designed and synthesized. 1O exhibited sensitivity to light irradiation and Zn 2+ . Stimulated by UV/Vis light and Zn 2+ , distinct changes were observed in the UV–vis and fluorescence spectra. The binding of Zn 2+ caused the open-ring absorption band of 1O to display an intense absorption band at 412 nm with a notable color change from colorless to yellow. Furthermore, Zn 2+ induced a fluorescence “turn-on” of 1400-fold and a fluorescence color change form dark to bright green due to the chelation-enhanced fluorescence effect. A Job’s plot established the 1:1 stoichiometry of the complex formation between 1O and Zn 2+ , and the limit of detection for Zn 2+ is as low as 3.2 × 10 –8 mol L –1 . Therefore, the compound could be used as a selective and sensitive fluorescence ratiometric sensor for the detection of Zn 2+ . Finally, we demonstrated that the sensor can penetrate into HeLa cells and could be used for the determination of intracellular Zn 2+ . [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]

Taking advantage of the special Hg 2+ -promoted deprotection reaction of dithioacetals and the well-known coumarin chromophore, novel reactive fluorescent probes ( C3 and C4 ) towards mercury ions were designed and synthesized. Upon the addition of mercury ions, probe C3 displayed remarkable fluorescence quenching, which was beneficial to the production of a high signal output during sensing process. Differently, compound C4 displayed dramatic red-shift in both fluorescence (60 nm) and absorption (60 nm) spectra, with the detection limit of 90 nM. By virtue of this unique chemical reaction, compound C4 had selective response towards Hg 2+ over other metal ions and only the addition of Hg 2+ could lead to apparent emission and absorption spectra changes. Moreover, C4 was successfully applied to microscopic imaging for the detection of Hg 2+ in HeLa cells with ratiometric fluorescent methods. [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] • The probe APDA exhibited sensitivity for Cu2+ ion in 80% aqueous acetonitrile medium. • Probe APDA shows dual emission due to TICT and ICT states. • The hydrolysis of imine bond of probe APDA in the presence of Cu2+ ion, rejuvenate aldehyde derivative. • The probe APDA has been applied on test paper strip to detect Cu2+ ion with naked-eye sensitive response. The work reported herein describes photophysical behavior of a new fluorescent probe APDA. The probe exhibited sensitivity for Cu2+ ion in 80% aqueous acetonitrile medium. Probe shows dual emission due to TICT and ICT states and upon interaction with different metal ions Cu2+ induces hydrolysis of imine bond to rejuvenate aldehyde derivative with ratiometric "turn–On" fluorescence response, through ICT state while emission due to TICT state get diminished. Similarly, the synthesized model compound ADA under similar experimental condition supported hydrolysis of imine bond in the presence of copper. Jobs plot analysis, based on emission titration data suggested a 1:1 binding stoichiometry between probe APDA and Cu2+ ion. The limit of detection (LOD) was found to be 4.4 × 10-8 M (44 nM). The probe has been applied on test paper strip to detect Cu2+ ion with naked-eye sensitive response. Also, the cell imaging studies revealed the potential applicability of probe to detect Cu2+ ion in live cells. The mechanism of sensing was confirmed by 1H, 13C NMR, FTIR and mass spectrometry data analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Np-N 3 could act as "off–on" photoactivatable probe under visible light irradiation. • The strategy of ICT-PET dual-mechanism was used to reduce background fluorescence and improve sensitivity. • The synergistic effect of ICT-PET was demonstrated by TD-DFT calculation. • The Np-N 3 was successfully used for spatiotemporal-controlled live cell imaging and intracellular H 2 S detection. The organic small molecule fluorescent probes are very effective tool for accurately analyzing target molecules and super-resolution microscopy biological imaging. Generally, reducing the interference of background fluorescence is one of the effective strategies to improve the resolution and signal-to-noise ratio of biological imaging. Herein, in this work, using the synergistic effect of the ICT-PET dual quenching mechanism to reduce background fluorescence, the fluorescent probe Np-N 3 with naphthalimide and small size azide as photocage and the recognition site of H 2 S was designed and synthesized. The synergistic mechanism of ICT-PET was computationally demonstrated by TD-DFT. The Np-N 3 showed low background fluorescence, high sensitivity and high selectivity for visible light and H 2 S, respectively. Meanwhile, under visible light irradiation (465 nm), the azide was easily reduced to amino in situ without complicated separation steps, restoring strong emission in a short time (<3 min). Importantly, the spatiotemporal-controlled imaging of live HeLa cells was successfully achieved. In addition, the probe was also applied to detect and image H 2 S in solution and living HeLa cells. [ABSTRACT FROM AUTHOR]

A Rhodamine B- quinoline conjugate ( RSQ ) functions as a colorimetric and fluorescence probe for selective recognition of Bi 3+ ion based on CHEF assisted FRET process. RSQ visibly changes its colour and fluorescence profile upon addition of Bi 3+ ion. The distinctive colour change allows facile discrimination of Bi 3+ over other common cations. Lowest concentration of Bi 3+ detected by RSQ is 0.05 μM. RSQ efficiently images intracellular Bi 3+ in live SiHa cells. [ABSTRACT FROM AUTHOR]

An efficient and simple photoinduced electron transfer (PET) based fluorescence turn– On probe 7 has been designed and synthesized by bridging naphthalimide and thiophene moieties through a piperazine unit. The photophysical behavior of probe and its affinity toward different metal ions have been investigated in partial aqueous medium, protein medium and live cells. The probe exhibited fluorescence “ turn-On ” response for Fe 3+ ion with high sensitivity (limit of detection 0.373 μM) and selectively along with naked-eye sensitive visible green color in the medium. The significant change in photophysical behavior of the probe, upon a complexation between probe and Fe 3+ is attributed to restriction in PET process. The probe 7 showed excellent biocompatibility and has been utilized in cellular imaging experiment to detect Fe 3+ in MCF-7 live cells. Also, at molecular level probe 7 mimics the functions of a sequential logic circuit, corresponding to a memory device in which the two inputs (Fe 3+ and AcO − ) based sequential logic operations mimic the function of a memory element. [ABSTRACT FROM AUTHOR]

A new 2-phenyl-benzothiazole (PBT) based fluorescent probe (AcO-PBT-CHO) was designed and synthesized for the detection of hydrazine. The aldehyde and acetyl ester groups were used as the recognition units. Upon the treatment of the probe with hydrazine, the emission at 505 nm decreased while the emission at 430 nm increased. Accordingly, the fluorescent color changed from green to blue. The aldehyde and acetyl ester groups exerted additive effect on the fluorescence spectrum changes of the probe. The probe could selectively identify hydrazine over other related interfering species. The probe could detect hydrazine quantitatively in the range of 20–40 μM with the detection limit of 2.80 ppb. Furthermore, the probe was successfully applied to detect hydrazine in living cells. [ABSTRACT FROM AUTHOR]

Conjugated polymer nanoparticles have been regarded as promising fluorescent materials for biological application, due to their high emission efficiency, good photostability and low cytotoxicity. In this contribution, we synthesized a conjugated polymer which integrates blue-, green- and red-emitting components into the backbone in an appropriate molar ratio. After being transferred from solution to nanoparticles, its fluorescence color turns from blue to pink with enhanced fluorescence quantum yield. After incorporation of an amphiphilic polymer as matrix, white-emissive polymer nanoparticles are obtained as a result of optimized energy transfer degree among the three components. Finally, their good performance on cell imaging are demonstrated by incubation with HeLa cells, after being proved to be safe for biological application. [ABSTRACT FROM AUTHOR]

A new rhodamine based fluorescent turn on sensor L has been reported as a highly selective and sensitive chemosensor for the Cr 3+ ion in a CH 3 CN-H 2 O solution. In presence of Cr 3+ ion, the strong fluorescence enhancement is attributed due to the interaction of Cr 3+ with L, leading to opening of the spirolactam ring of rhodamine B to the amide form. The Cr 3+ sensing mechanism is also supported by the Job’s plot, ESI-MS, 1 H NMR titration experiments. Importantly, this probe shows high selectivity over other biologically relevant metal ions. Also, anions do not show any effect. In addition, the detection limit is found to be up to 7.5 nM which is acceptable within the EPA (US) limit. The probe is also able to function within a broad biological pH range of 4–8. Furthermore, the probe L shows cellular penetrability for its potential use in confocal cell imaging studies. [ABSTRACT FROM AUTHOR]

• Naphthalene based fluorescent chemosensors OHN and OHHN was synthesized, characterized and metal selectivity studies were performed. • The sensor OHHN exhibited an excellent selectivity and high sensitivity toward Al3+ ions over competing cations. • "Switch OFF-ON" fluorometric response was established for the probe OHNN towards the Al3+ ions through a probable PET, CHEF and C N isomerization mechanisms. • The binding mechanisms were arrived based on the Fluorescence studies, supported by the DFT studies. • The chemosensor OHNN applications in real sample analysis such as water, soil, food products like tomato sauce including the live bacterial cell imaging were demonstrated. Simple naphthalene based fluorescent chemosensors OHN & OHHN were prepared by single step procedures and utilized to detect Al3+ ion by absorption and emission spectroscopy. These studies confirmed that receptor OHHN showed significant selectivity and sensitivity towards Al3+ ion compared to other metal ions whereas there was no notable selectivity in the case of the receptor OHN. A significant enhancement in the fluorescence intensity was observed during the addition of Al3+ ions to the chemosensor OHHN. According to the emission studies, a plausible mechanism was proposed based on three reasons, i.e i) arrest of the Photoinduced Electron Transfer (PET), ii) C N isomerization and iii) Chelation Enhanced Fluorescence Effect (CHEF). The 1H NMR and IR studies further confirmed the binding mechanism of the chemosensor OHHN with Al3+ ions. The fluorescence intensity changes in the Job's plot predicts that the Al3+ ions bind with the receptor OHHN leading to the formation of a 1:2 stoichiometric ratio binding mode. The association constant and the limit of detection of the receptor OHHN with Al3+ ions were found to be 6.6×10−2M−1 and 0.176×10−5 M respectively. To test its real level effectiveness, the receptor OHHN has been tested with water, soil, food samples and live bacterial cell imaging. [ABSTRACT FROM AUTHOR]

Based on Cu 2+ - promoted hydrolysis reaction a rhodamine B derivative L containing a napthalene moiety has been synthesized as a fluorescence turn-on chemodosimetric probe for Cu 2+ in EtOH:H 2 O (3:1, v/v, 10 mM HEPES Buffer, pH ≈ 7). The Cu 2+ promoted ring opening and hydrolysis reaction of L leads to formation of the 2:1 ligand metal intermediate complex which rapidly converts to rhodamine-B and bis-Cu 2+ complex of 1, 8 diaminonaphthalene. The proposed sensing mechanism has been supported by ESI–MS, 1 H NMR, 13 C NMR, IR analysis and DFT calculations. The dye L exhibits high selectivity toward Cu 2+ over other relevant metal ions and anions in the physiological pH range 5–8 with a low detection limit of 60 nM. Application in confocal cell imaging in HeLa cells is also demonstrated in the current work. Additionally, L has been shown to be non-toxic and biocompatible for mammalian cells. [ABSTRACT FROM AUTHOR]

Although a variety of fluorescence based chemosensors have been utilized for selective detection of Zn 2+ , pyridoxal containing simple Schiff bases still remained less explored. Here, we combine pyridoxal hydrochloride and 1,2-diaminocyclohexane to generate a new sensor molecule, H 4 PydChda [5-Hydroxymethyl-4-({2-[5-hydroxymethyl-2-methylpyridin-3-hydroxy-4-ylethylene)-amino]-cyclohexylimino}-methyl-2-methylpyridin-3-ol]. Chemosensor H 4 PydChda exhibits selective turn-on type response in presence of Zn 2+ in ethanol-water mixture at physiological pH. Appreciable fluorescence enhancement occurs upon addition of Zn 2+ to H 4 PydChda as a result of inhibited C N isomerisation and excited state intramolecular proton transfer (ESIPT) leading to efficient chelation enhanced fluorescence (CHEF). The relevant properties, including reversibility, life time measurements and detection limit have been determined for the sensor system. The experimental and theoretical supports in terms of 1 H and 13 C NMR spectroscopy and DFT/TDDFT study are provided to establish the binding mode of H 4 PydChda to Zn 2+ . H 4 PydChda was employed as a sensor for detection of Zn 2+ in Human gastric adenocarcinoma (AGS) cells. Moreover, the resulting probe-Zn 2 + complex shows convincing phosphatase activity (k cat = 21.59 s −1 ), opening a promising avenue for further research. [ABSTRACT FROM AUTHOR]

[Display omitted] • A highly selective and sensitive chemosensor (L) for detection of Hg2+ ion in semi-aqueous medium. • The chemosensor can detect Hg2+ ions as low as 11.8 nM by spectrofluorometric by turn-off mechanism. • The practical utility of probe L was studied on the test strip, real water analysis and live cell imagaing. We have developed a new chromogenic and fluorogenic chemosensor (L) based on benzothiazole conjugated with quinolinyl acrylate for the detection of Hg2+ ions with excellent selectivity and sensitivity. In the presence of Hg2+, the fluorescence of L was quenched from light blue to colorless. The L could work in the wide pH range of 5.0–8.0 without considerable interference from other tested ions. UV–Visible and fluorometric investigations revealed that the limit of detection (LOD) for Hg2+ was 1.0 μM (202 ppb) and 11.8 nM (2.38 ppb), respectively. Further, the applicability of probe L in the determination of Hg2+ in various water samples and biological samples were tested. Human Bone Osteosarcoma cell lines (HOS) were utilized for this study and satisfying results were obtained. These cell line results also further support the 'on-off' properties of probe L. Based on the colorimetric and fluorescent results we have designed a Boolean logic gate for futuristic applications. [ABSTRACT FROM AUTHOR]

A new rhodamine 6G derived chemosensor L has been synthesized that selectively detects the presence of Cu 2+ ion over a host of other biologically important and environmentally relevant metal ions in aqueous alcoholic medium under physiological pH (ethanol: water, 1:1, v/v, pH 7.2). The significant enhancement of fluorescence intensity of L is caused by Cu 2+ ion induced cleavage of spirolactum bond in the rhodamine moiety. This mechanism is well supported by the crystal structure of the L-Cu 2+ complex that depicts two ligand units are bonded to two Cu 2+ ions. Color of the solution changes from light orange to dark pink upon metal binding which allows naked eye detection ion as well. Confocal microscopic experiments validate that the dye is potentially useful for the selective detection of Cu 2+ ion in living cells. Therefore the dye is an excellent fluorogenic and chromogenic chemosensor for the Cu 2+ ion in aqueous ethanolic medium and the living cell as well. [ABSTRACT FROM AUTHOR]

A new rhodamine hydrazone obtained by the condensation of rhodamine hydrazide with 5-iodo-3-methoxy salicylaldehyde (NLAC) is synthesized and characterized using spectroscopic (IR, UV–vis, 1 H, 13 CNMR, ESI-MS) and X-ray diffraction techniques. It binds selectively with Al 3+ ions and a strong fluorescence signal is displayed from [ NLAC − Al 3+ ] ensemble and has also been supported by DFT calculation. The color change of NLAC in presence of Al 3+ ions is further corroborated by UV-visible and fluorescence spectral titrations. The spectral changes are significant in the visible region of the spectrum and enable the detection of Al 3+ ions with naked eye. The 1:1 stoichiometry of NLAC:Al 3+ is supported by Job’s plot and ESI-MS data. The fluorescence signal displayed from [ NLAC − Al 3+ ] is quenched on the addition of N 3 − ions as an aqueous solution of NaN 3 salt which reverts back further on the addition of Al 3+ ions. This recognition process is also displayed in a human cervical cancer cell lines (SiHa cells) in an aqueous-acetonitrile medium. The process is repeated several times showing that the system is robust and reversible in the recognition process. A strip tests supports its feasibility for the laboratory demonstration. [ABSTRACT FROM AUTHOR]

A new simple Schiff-base ligand 2-Hydroxy-1-naphthaldehyde-(2-pyridyl) hydrazone (HL) was synthesized and characterized as a fluorescent probe. In aqueous solution containing 10% ethanol (Hexamethylenetetramine-HCl buffer, pH5.3), HL selectively binds Al 3+ to form a 1:1 ligand/metal complex, resulting in a color change from colorless to yellow–green and a significant fluorescence enhancement at 454 nm. The addition of EDTA quenches fluorescence of the HL·Al 3+ complex, indicating that HL serves as a reversible chemosensor for Al 3+ . Under the optimum conditions, the dynamic range of the system was found to be linear up to 4.0 × 10 −6 M Al 3+ ions with a limit of detection of 36.6 nM. The probe is very effective for detection of intracellular Al 3+ through fluorescence microscopic imaging. [ABSTRACT FROM AUTHOR]

A new quinoline functionalized Schiff base ( L ) was synthesized which displayed selective fluorescence response to trivalent metal cations (Al 3+ , Fe 3+ and Cr 3+ ) over a variety of divalent and monovalent metal cations in ∼100% aqueous medium. The specific sensing of trivalent cations by a switch-ON fluorescence response is based on selective acid catalyzed imine bond hydrolysis of L facilitated by the higher valence metal ions in aqueous medium and this mechanism was corroborated by mass spectrometry and density functional theory (DFT) calculations. The developed probe was biocompatible and rendered sensing of trivalent metal ions (Al 3+ , Fe 3+ and Cr 3+ ) in live HeLa cells through imaging. [ABSTRACT FROM AUTHOR]

A dual-site fluorescent probe based on naphthalimide and rhodamine was synthesized, which could rapidly and sensitively respond to H 2 S and Cu2+ with different fluorescence signals. [Display omitted] • The dual-responsive fluorescent probe (DTR-1) for detection of H 2 S and Cu2+ was developed. • DTR-1 could detect H 2 S and Cu2+ within 1 min. • The LOD for H 2 S and Cu2+ were calculated to be 0.035 μM and 0.16 μM, respectively. • DTR-1 was successfully applied to detect intracellular H 2 S and Cu2+. A highly selective and sensitive fluorescence probe (DTR-1) for simultaneously detecting H 2 S and Cu2+ with different fluorescence signals was synthesized. DTR-1 displayed remarkable fluorescence enhancement (560 nm, 34-fold) when H 2 S was added under excitation of 410 nm with the solution's color change from dark to green. The limit of detection (LOD) for H 2 S was calculated to be 0.035 µM. By contrast, the addition of Cu2+ enhanced obviously the emission intensity of DTR-1 with the maximal peak at 630 nm and color change from colorless to orange. LOD for Cu2+ was determined to be 0.16 µM. The sensing mechanism for H 2 S and Cu2+ in DMF/PBS (9/1, v/v, pH = 7.4) was studied by 1H NMR and ESI-MS. Furthermore, the potential application of DTR-1 in biological systems had been demonstrated through imaging of living cells. [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] • New "turn on" fluorescence sensor for Cd2+ was developed based on tetrahydro-[5]helicene derivative. • Sensor provided a rapid fluorescence sensing recognition for Cd2+ with a remarkable large Stokes shift. • Sensor exhibited a high selectivity toward Cd2+ over other interfering metal ions such as Zn2+. • The detection limit was similar to the Cd2+ levels in drinking water specified by U.S. EPA. • Sensor had potential for intracellular labeling as an efficient Cd2+-tracking agent in biological sample. A new tetrahydro-[5]helicene-based fluorescence sensor (PM) was conveniently synthesized for rapid detection of cadmium ion (Cd2+). PM , which has a tetrahydro-[5]helicene derivative, provided a highly sensitive "turn on" fluorescence sensing recognition for Cd2+, with a remarkable large Stokes shift of 163 nm (1.01 eV). The sensor exhibited a fluorescence enhancement toward Cd2+ via photo-induced electron transfer (PET) quenching, a process related to Cd2+-sensor complexation. PM permitted a high selective response to Cd2+ over other interfering metal ions, such as Zn2+. The application of sensor for detection of Cd2+ in commercial food products, including drinking water and rice, were performed and acceptable results were obtained. In addition, this fluorescence sensor could be efficiently applied as a fluorogenic label for tracking Cd2+ in living cells. The potential Cd2+ determination of PM ensures that this sensor can be utilized as fluorescence materials or devices for the real-time monitoring and control of Cd2+ contamination outbreak. [ABSTRACT FROM AUTHOR]

[Display omitted] • A Schiff base molecule (L) having pyrene and coumarin moieties was synthesized. • L is highly selective colorimetric and fluorometric probe for Al(III), Cr(III) and Fe(III) with very low detection limit. • Fluorescence response is an "OFF-ON" mechanism through inhibition of PET and operation CHEF processes. • Cell imaging and cytotoxicity studies performed using MDA-MB-231 and HDF cells indicate that L is biologically safe. A Schiff base (L) containing coumarin and pyrene moieties was synthesized and characterized. It showed excellent selective recognition of M(III) ions (M = Al, Cr and Fe) in presence of monovalent, divalent and other trivalent metal ions. Sensor L itself is non-fluorescent upon excitation with 353 nm light (λ ex = 353) but a very large enhancement in fluorescence intensity was observed during the addition of these three trivalent metal ions into a CH 3 OH/aqueous HEPES buffer (5 mM, pH = 7.4, 6:4, v/v) solution of L. This prominent "OFF-ON" fluorescence switching can be observed with naked eye, in which "OFF" is due to operation of PET process in free L but PET is inhibited upon complexation thereby allowing CHEF (chelation enhanced fluorescence) process to operate. Detection limits of Al3+, Cr3+ and Fe3+ using L have been found to be 0.79 nM, 1.15 μM, and 1.28 μM respectively in the pH range of 6‒10. Additionally, "OFF-ON" fluorescence can be reversed by sequestering M(III) ions using [EDTA]4– solutions. Analysis of mass spectra and Job's plot revealed a binding ratio of 1:1 for all three metal ions with L. The imine nitrogen and carbonyl oxygen atoms of L are involved in binding with Al3+, Cr3+ and Fe3+ ions, as revealed by NMR titration and IR spectroscopic analysis. Results of quantum yield (Φ), time resolved photoluminescence (TRPL) and computational studies (DFT/TDDFT) studies were also reported. Fluorescence intensity of these M(III) bound L complexes is quenched by fluoride ions. From cytotoxicity analysis, 7.5 μM of probe L was selected to analyze its fluorescence attributes in cellular imaging. Using human breast cancer cell line (MDA-MB-231) and primary human dermal fibroblasts (HDF), the potentiality of the probe L was confirmed through fluorescence cell imaging experiments. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel series of quinoline-pyridine conjugated compounds were synthesized. • The effects of amino protons and denticity to metal were studied. • The absence of amino proton increases the Cd2+/Zn2+ selectivity. • The increase of N atoms increases the binding to Cd2+ greater than Zn2+. • The compounds were applicable for detecting Cd2+ in aqueous media and cell imaging. Zn2+ and Cd2+ are d10 metal ions with very different toxicity level but similar binding properties to most organic ligands. Herein, a series of quinoline-pyridine conjugates are synthesized and evaluated for binding properties on both metal ions. The effects of amino protons and number of N-donor atoms on the ligands binding to Cd2+ and Zn2+ were studied by UV–vis titration in aqueous solution. The association constant for Cd2+ is affected by amino protons and denticity of the ligands greater than that of Zn2+. As the results, the Cd2+/Zn2+ binding ratio can be tuned by the ligand design. L6, the ligand with 6 N atoms without the proton, exhibits the highest Cd2+/Zn2+ binding ratio with fluorescence enhancement at 480 nm. The ligand can be used for detecting Cd2+ with the detection limit of 69 nM in aqueous solution and monitoring Cd2+ within cells at the concentration range of 0.1−10 μM. [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]

[Display omitted] • A rational design of probe Chol-6RN strives to minimize the interference between recognition moiety and functional moiety. • The probe Chol-6RN is better than the control probe Chol-RN in the linearity and the detection limit. • The cell imaging experiments show that Chol-6RN has good biocompatibility and membrane permeability. To improve the sensitivity and detection limit of probe, we made good use of the advantage of 6-carboxyrhodamine to design a new cholesterol-conjugated fluorescent probe Chol-6RN for Cu2+ detection. The probe Chol-6RN exhibits a sensitive response towards Cu2+ by fluorescence spectrum in aqueous solution. The linearity of Chol-6RN is from 5 μM to 40 μM of Cu2+ with an excellent linear correlation (R2 = 0.99110) and the detection limit for Cu2+ is 1.12 μM, they are better than the control probe Chol-RN. The MTT assay indicates that Chol-6RN is negligible cytotoxicity to HeLa cells after 24 h at a concentration less than 30 μM. The cell imaging displays that Chol-6RN is capable of detecting Cu2+ in live cells and the sensibility of Chol-6RN is better than Chol-RN. [ABSTRACT FROM AUTHOR]

• Hydrazide based fluorescence probe for detection of Al3+ ions. • Therotical calculations (DFT) were carried out for probe (SCH) and Al3+-SCH. • Life time decay were carried out. • SCH and Al3+-SCH used for cellular imaging sensor in MCF-7 cells Development of highly specific and susceptible sensors for aluminium (Al3+ ions) determination in water medium is still a remarkable task. Herein, a fluorescence probe (SCH) is derived from the condensation of salicyaldehyde and carbohydrazide in 2:1 M ratio and promising chemical sensing of Al3+ ions is investigated. Examinations of the emission features of SCH in CH 3 OH:H 2 O (1:2, v/v) solution showed excellent turn on behaviour of Al3+ ions, which is due to 1:1 complex formation between SCH and the Al3+ ions at ambient conditions. The lowest limit of detection was estimated by emission titration experiments and found to be 32 nM which is much more 1000-fold lower than that WHO suggested maximum tolerable concentration. The present probe SCH was highly specific for the detection of Al3+ ions over other potential interfering metal cations. Based on the reversible emission behaviour, an INHIBIT logic gate was assembled with EDTA and Al3+ ions as two inputs. In addition, prospective application of SCH as cellular imaging sensor of Al3+ ions in MCF-7 cells was monitored using optical fluorescence microscopic images and real water samples. [ABSTRACT FROM AUTHOR]

• BHMBH with benzothiazole fluorophore was synthesized and characterized. • BHMBH exhibits highly sensitivity fluorescence enhancement to Al3+ along with color change. • Limit of detection (LOD) for Al3+ was reached the level of 10−7 M. • BHMBH was successfully applied in the detection of Al3+ on test paper and imaging in HSC. An easy prepared benzothiazole-based probe (E)-5-(benzo[d]thiazol-2-yl)-2-hydroxy-3- methoxybenzaldehyde benzoyl hydrazone (BHMBH) was designed and synthesized, which displayed a significant fluorescence enhancement (over 500-fold) and obvious color changes in the recognition of Al3+. The binding ratio of probe BHMBH to Al3+ was determined as 1:1 according to Job's plot. The binding mechanism was fully clarified by the experiments such as FT-IR spectrum, ESI-MS analysis, and 1H NMR titration. The limit of detection (LOD) for Al3+ was determined as low as 0.232 μM based on the fluorescence titration of BHMBH. Moreover, the results of real sample experiments including real water sample, test papers, and cell image were all well demonstrated that BHMBH was capable of sensing Al3+ in environmental and biological system as well. [ABSTRACT FROM AUTHOR]

Reduction pathway inspired tuning of fluorescence properties of carbon dots. • CNBF were reduced to rCNBF by reducing agent NaBH 4. Three different sets of carbon dots were prepared, i.e. rCNBF1, rCNBF2, and rCNBF3. • rCNBF3 having maximum concentration of NaBH 4 showed maximum quantum yield and fluorescence lifetime w.r.to CNBF. • The significant change in quantum yield and lifetime values pertained with energy bandgap values as with rCNBF3 the band gap gets increased to 1.78 eV from 1.08 eV for CNBF. • Present work provides conclusive evidence related to functional group modifications, suppression in non-radiative decaying process for enhanced fluorescence in rCNBF. Carbon dots are shown to have potential applications in the areas ranging from catalysis, bioimaging, drug delivery, energy and electronics etc. Owing to its excellent fluorescence property, facile synthesis method and robust chemical inertness, it has become one of the most studied materials for this decade. In present work, hetero-atom doped carbon dots and its reduced forms were studied in detail for their optical properties. A heteroatom (nitrogen, boron, and fluorine) co-doped carbon dots (CNBF) was synthesized (using citric acid as a primitive carbon source). Further, CNBF was reduced with different concentrations of sodium borohydride (NaBH 4) leading to the synthesis of rCNBF1, rCNBF2, and rCNBF3. The distinct optical characteristics of CNBF, rCNBF1, rCNBF2 and rCNBF3 were studied using different spectroscopic techniques. The quantum yield and fluorescence lifetime of the reduced forms rCNBF1, 2 and 3 were 39.14%; 41.73%; 44.61 and 13.30 nS, 13.52 nS, 14.21 nS, respectively which was higher than CNBF having a quantum yield of 35.73% and 11.98 nS. It was observed the energy bandgap of rCNBF was higher than CNBF suggesting the functional group modification due to reduction which tuned the optical behaviour. Afterward using transmission electron microscope (TEM) morphologies of CNBF and rCNBF were studied. This study opens a new avenue in designing fluorescent materials using functional group modifications having potential emerging applications. [ABSTRACT FROM AUTHOR]

Two new asymmetric 9, 10-dithienylanthracene derivatives (DTA-BO and DTA-BT) with aggregation-induced enhanced emission (AIEE) property have been synthesized. Their properties, including AIEE properties, mechanofluorochromic (MFC) and cell imaging were investigated in detail. • Two new DTA derivatives with good AIEE behavior had been designed and synthesized. • All these compounds exhibited high luminous efficiency in the aggregate states. • These AIEEgens showed reversible mechanofluorochromic performance by grinding-fuming. • These AIEEgens could be applied in cell imaging as fluorochrome. Two asymmetric 9, 10-dithienylanthracene compounds (DTA s), [9-thienyl-10-(5-vinylbenzoxazolyl-2-thienyl)]anthracene (DTA-BO) and [9-thienyl-10-(5-vinylbenzothiazolyl)-2-thienyl]anthracene (DTA-BT), have been designed, synthesized and characterized. The DTA s exhibit aggregation-induced emission enhancement (AIEE) behaviors and high fluorescence quantum yields in the states of aggregation, as well as reversible mechanofluorochromic (MFC) behaviors upon grinding-CH 2 Cl 2 fuming. Intriguingly, DTA-BO and DTA-BT show great application potentials in cell imaging with good cell membrane penetration and strong luminescent emission performances. Our work is helpful for the design and development functional AIEE dyes based on DTA -skeleton. [ABSTRACT FROM AUTHOR]

• Fluorescent organic nanoparticles FONs-RSB prepared by reprecipitation method. • FONs-RSB showed Chelation enhanced fluorescence only in the presence of Hg2+. • Interference-free detection of Hg2+ ions using a proposed sensing method. • The extremely low detection limit of 1.729 ng/mL for Hg2+ ions in an aqueous medium. • Feasibilities are analysis of environmental samples and intracellular cell imaging. A simple, quick and useful reprecipitation method was used to prepare rhodamine based fluorescent nanoparticles. The characterization techniques such as zeta-particle sizer and scanning electron microscopy were studied to investigate the formation of desired nanoparticles FONs-RSB along with its aqueous stability, surface charge, particle size, and morphological features. The comparative optical properties between parent molecule RSB and FONs-RSB were examined using absorption and fluorescence studies. The sphere morphology of FONs-RSB having 82 nm particle size and negative zeta potential (−33.5 mV) showed selective and sensitive interaction with only Hg2+ amongst the series of metal ion studied which was revealed by florescence titration results. The interaction between FONs-RSB and Hg2+ leads to enhance the fluorescence of FONs-RSB is because of chelation enhanced fluorescence (CHEF) phenomenon. The interference of foreign metal ions was found to be unaffected to the fluorescence enhancement induced by Hg2+. The binding stoichiometry and binding constant were evaluated using Job's and modified Benesi-Hildebrand plot. The mechanism of binding interaction and nature of complexation were analyzed using Infrared (IR), Nuclear Magnetic Resonance (NMR), absorption and fluorescence lifetime titrations in the absence and presence of a variable amount of Hg2+ to FONs-RSB. Further, the reaction product of the sensing process in the present investigation was examined using mass analysis. The detection limits calculated using the present method were found to be 1.729 ng/mL (8.619 nM) and 1.68 ng/mL when linear concentration of Hg2+ additions were 0−2 μg/mL and 0−100 ng/mL, respectively. The practical application of the present method involves the quantitative determination of Hg2+ in environmental samples collected from the local campus and intracellular cell imaging of Hg2+ using A375 living cells with non-toxic behavior. [ABSTRACT FROM AUTHOR]

• A colorimetric and fluorescent probe QLB-CF for Hydrogen polysuldes was reported. • The probe achieved the fast naked-eye detection to H 2 S n and the detection limit as low as 0.03μM. • The QLB-CF was successfully applicable to exogenous H 2 S n detection and imaging in living cells. A colorimeric and fluorescent probe QLB-CF has been developed for the highly sensitive and specific imaging of hydrogen polysuldes (H 2 S n , n> 1). Its selective fluorometric/colorimetric sensing of H 2 S n was demonstrated in detail. Upon addition of H 2 S n , the probe exhibited fast response to H 2 S n along with a remarkable color change from colorless to yellow which could be easily observed by the naked eye. Similarly, the probe exhibited fluorescence response to H 2 S n with approximately 7-fold fluorescence enhancement and the fluorescence color change from none to cyan. In addition, the probe displayed high selectivity towards H 2 S n among various analytes. What's more, the probe has been successfully applied to exogenous H 2 S n detection and imaging in living cells, allowing us to visualize its sensing potential application in living cells. [ABSTRACT FROM AUTHOR]

• Probe FL can display selectivity toward Cu+2 over other ions in DMSO/water (2/8, v/v) and showed an obvious color change. • Probe FL can operate in a wide range of pH. • The living cell image experiments demonstrate probe FL could be used to detect intracellular Cu2+ in living cells. A novel fluorescent and colorimetric probe FL was designed and synthesized for selective Cu2+ detection in aqueous solutions. The detection limit of probe FL for Cu2+ was determined to be 1.09 μM. Furthermore, probe FL was successfully used to recognize Cu2+ in living cells, indicating its high potential in biological imaging applications. [ABSTRACT FROM AUTHOR]

• A "turn-on" fluorescent probe ol -PIP selectively responded to Hg2+ with large Stokes shift of 180 nm. • Subsequently, strong emission of ol -PIP–Hg2+ was quenched followed by S2–. • The process of the sequential sensing was realized in cells imaging. An excited state intramolecular proton transfer (ESIPT) characteristic "turn-on" fluorescence sensor for Hg2+ with large Stokes shift was fabricated and then it had ability to sequentially detect S2– by the "turn-off" fluorescent signal in aqueous media. On account of it, a simple fluorescence probe ol -PIP based on the phenanthro[9,10- d imidazole moiety bearing two phenol fragments was synthesized. Probe ol -PIP showed gradually the fluorescence enhancement with the increasing of water fraction due to the aggregation affect. Sequentially, the moderate fluorescence emission of ol -PIP in aqueous media was continuously and selectively illumined by the successive addition of Hg2+ with about 180 nm Stokes shift. Furthermore, the persistent "turn-on" fluorescence intensity could be quenched to the original state of ol -PIP in presence of S2–. This on–off sensing process was sustained for five times with the alternative addition of Hg2+ and S2–. The limits of detection for Hg2+ and S2– were 6.45 × 10–7 and 3.46 × 10–7 M, respectively. In addition, ol -PIP was successfully applied in Hg2+ detection in real water samples; simultaneously, ol -PIP with low cytotoxicity was also successfully used as a bioimaging reagent to detect Hg2+ and S2– in living cells. [ABSTRACT FROM AUTHOR]

• Novel phenothiazine-based colorimetric and ratiometric fluorescent sensor PPM for Hg2+ is synthesized. • PPM shows high selectivity and low detection limit of 12.5 nM in a wide pH range. • The response time of PPM for Hg2+ is within 1 min and suitable for ultrafast detection of Hg2+. • PPM for Hg2+ shows good applicability for paper/TLC-based "naked-eye" colorimetric assay. • PPM was used for fluorescence imaging of Hg2+ in living cells. A new phenothiazine-based sensor PPM was successfully designed and synthesized, which shows highly selective, ultrafast, naked-eye colorimetric and turn-on ratiometric fluorescence sensing of Hg2+ on the basis of the ICT from phenothiazine to aldehyde. Upon addition of Hg2+, obvious blue fluorescence at 455 nm decreased while green fluorescence at 528 nm enhanced, which exhibits ratiometric fluorescent turn-on response along with a "naked-eye" color change from pale-blue to bright-green. The PPM for highly sensing of Hg2+ with a quite low detection limit (12.5 nM) and a wide pH application range. The sensing mechanism proved to be the Hg2+-triggered thioacetal deprotection reaction was confirmed. Importantly, PPM was successfully employed for highly selective detecting and imaging of Hg2+ in living cells, as well as on paper/TLC-based "naked-eye" colorimetric assay. [ABSTRACT FROM AUTHOR]