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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 new highly selective chemosensor 1 ( E )-5-((2-hydroxybenzylidene)amino)-1H-imidazole-4-carboxamide was designed and synthesized for the sequential recognition of Zn 2+ and S 2− in a near-perfect aqueous media. The sensor 1 exhibited a green color fluorescence in the presence of Zn 2+ . The detection limit (1.18 μM) of 1 for Zn 2+ is much lower than World Health Organization guideline (76 μM) in drinking water. 1 can detect and quantify Zn 2+ in real water samples and the sensing mechanism of Zn 2+ by 1 was explained by DFT calculations. Moreover, resulting 1 -Zn 2+ complex can detect hydrogen sulfide through turn-off fluorescent change, without any anion interference. The detection limit (2.60 μM) of 1 -Zn 2+ complex for S 2− was much lower than EPA guideline (7.8 mM) by odor in drinking water. Furthermore, sensor 1 could detect sequentially Zn 2+ and S 2− in living cells. [ABSTRACT FROM AUTHOR]

A novel aggregation-induced emission (AIE) active linear conjugated bis-Schiff base compound, ( E )- N , N ′-bis(4-( Z )-2-(4-butoxyphenyl)-1-cyanovinylphenyl)-1,4-benzenebismethaneimine ( 4 ) containing α-cyanostilbene unit was designed, synthesized and characterized. The distinct change of color and/or fluorescence emission of 4 + Hg 2+ in tetrahydrofuran (THF) and THF/water solution provided a simple and easy discrimination way for Hg 2+ by “naked eye” or using a UV lamp. The aggregating patterns of 4 were applied to explain the mechanism of sensing. The as-synthesized sample showed comparatively high selectivity and sensitivity to Hg 2+ through fluorescence “turn-on” response with a low detection limit (3.4 × 10 −9 M in THF, 2.4 × 10 −7 M in THF/water). The results implied that the as-made sample could effectively act as Hg 2+ sensor not only in THF and THF/water but in living cells. [ABSTRACT FROM AUTHOR]

A new fluorescent sensor 6-(2,3-dihydroxyphenyl)-5,6-dihydrobenzoimidazo[1,2-c] quinazoline (H 2 L) and the Zn(II) complex [Zn 2 L 1 2 ]∙C 2 H 5 OH (H 2 L 1 = 3-{[2-(1 H -benzoimidazol-2-yl)-phenylimino]-methyl}-benzene-1,2-diol) ( 1 ) were synthesized and characterized by single-crystal X-ray diffraction. H 2 L can be used to recognize Cu 2+ in aqueous media as an on–off fluorescent sensor, forming the Cu(II) Schiff-base complex (CuL 1 ). Furthermore, CuL 1 can serve as an off–on fluorescent sensor to detect histidine (His) via the ligand displacement approach. The sequential detection of Cu(II) and histidine shows on–off–on phenomenon. The crystal structure of the dinuclear Zn(II) complex indicates that the coordination of H 2 L with Zn(II) promotes C N bond breakage, resulting in the quinazoline ring-opening of H 2 L to form the Zn(II) Schiff-base complex ( 1 ). The experimental results proved that H + can also assist the ring-opening of H 2 L to form a Schiff base, H 2 L 1 . H 2 L is stable in neutral and weak basic solutions. This is further confirmed by the theoretical calculations. The cell imaging studies indicated that H 2 L and CuL 1 can be used to detect the intracellular Cu 2+ ion and His under physiological conditions, respectively. CuL 1 can also be used to determine His in urine. [ABSTRACT FROM AUTHOR]

The synthesis and evaluation of new quinoline based fluorescent chemosensor L1 for the detection of Zn 2+ in THF/H 2 O. The absorption and fluorescent spectra change was observed upon addition of Zn 2+ indicate that L1 is highly selective for Zn 2+ over other metal ions. The probe displayed an apparent color change while addition of Zn 2+ , which could be observed by the naked eye under a UV lamp. The experimental results have been verified with DFT and TDDFT calculation. In vitro sensitivity to Zn 2+ was demonstrated in Hela cells with the use of fluorescence confocal microscopy. [ABSTRACT FROM AUTHOR]

A new versatile ‘dual’ chemosensor 1 has been synthesized for Zn 2+ and Co 2+ . The sensor 1 comprises of quinoline as a fluorophore and N 1 , N 1 -dimethylethane-1,2-diamine as a water-soluble functional group. Sensor 1 showed a remarkable fluorescence enhancement in the presence of Zn 2+ in aqueous solution. The sensor 1 also acted as a colorimetric sensor for Co 2+ by changing its color from colorless to yellow. Importantly, the chemosensor 1 could be used to quantify Zn 2+ and Co 2+ in water samples and to image and quantify Zn 2+ in living cells. Moreover, the sensing mechanisms of 1 for Zn 2+ and Co 2+ were supported by theoretical calculations. Therefore, this sensor has the ability to be a practical system for monitoring Zn 2+ and Co 2+ concentrations in biological systems and aqueous samples. [ABSTRACT FROM AUTHOR]

A rhodamine derivative ( 1 ) is developed as a fluorescent chemosensor for trivalent chromium ions (Cr 3+ ). It exhibits a highly sensitive “turn-on” fluorescent response toward Cr 3+ with a 55-fold fluorescence intensity enhancement under 2 equiv. of Cr 3+ added. The chemosensor can be applied to the quantification of Cr 3+ with a linear range covering from 5.0 × 10 −7 to 2.0 × 10 −5 M and a detection limit of 1.7 × 10 −7 M. Most importantly, the fluorescence changes of the chemosensor are remarkably specific for Cr 3+ in the presence of other metal ions, which meet the selective requirements for practical application. Moreover, the response behavior of 1 toward Cr 3+ is pH independent in neutral condition (pH 6.0–8.0). The response of the chemosensor is fast (less than 2 min) and the chemosensor is chemically reversible. Furthermore, the ring-opening mechanism of the rhodamine spirolactam induced by Cr 3+ and the 1:1 stoichiometric structure between 1 and Cr 3+ were supported by Job's plot, NMR, MS and DFT theoretical calculations. In addition, the proposed chemosensor has been used to detect Cr 3+ in real water samples and image Cr 3+ in living cells with satisfying results. [ABSTRACT FROM AUTHOR]

A new turn-on fluorescent quinolone tetrazole based chemosensor (QT-1) is designed and synthesized which shows high sensitivity and selectivity for Zn 2+ ions in aqueous acetonitrile solution. QT-1 probe easily distinguishes Zn 2+ ions from Cd 2+ ions. Job's plot analysis suggested that the binding of QT-1 and Zn 2+ ions is probably a 1:1 stoichiometry. Thus QT-1 can be employed for fluorescent imaging of Zn 2+ ions in living cells. [ABSTRACT FROM AUTHOR]

A phenothiazine–aminothiourea-based open chemosensor ( P1 ) has been designed and synthesized, which exhibits high selectivity toward Hg 2+ by forming a 1:1 complex. In its Hg 2+ ensemble, it is reported as a highly sensitive and selective probe for the detection of iodide based on the displacement approach in aqueous solution. The addition of iodide to a solution of phenothiazine–aminothiourea–Hg 2+ ensemble resulted in a rapid and remarkable fluorescence off–on (emission at 565 nm). The practical use of an ‘ensemble’ was demonstrated by its application to the detection of iodide in the living cells. [ABSTRACT FROM AUTHOR]

A highly sensitive and selective quinoline based reversible chemosensor (HL) for the efficient detection of Zn 2+ has been developed. The synthesized chemosensor HL is highly efficient in detecting Zn 2+ over other metal ions commonly obtained in physiological and environmental samples. HL shows fluorescence ‘turn-on’ response with 53 fold enhancement of emission intensity in presence of Zn 2+ . The limit of detection is 5.0 × 10 −9 M. HL is efficient in detecting Zn 2+ intracellularly and also exhibits an INHIBIT logic gate with Zn 2+ and EDTA as chemical inputs by monitoring the emission mode. Electronic structure and sensing mechanism have been interpreted by DFT and TDDFT calculations. [ABSTRACT FROM AUTHOR]

A chemosensor 3-[(2-hydroxybenzylidene)-amino]-1H-pyridin-2-one (HL) for multi-ions was synthesized and characterized by single-crystal X-ray diffraction. HL is a turn-on fluorescence chemosensor for Al 3+ , F − , and CN − ions in DMSO. F − and CN − anions could be further distinguished by the ratiometric absorption spectrometry method. Job plot and 1 H NMR data showed that the binding stoichiometries of HL with Al 3+ , F − , or CN − all were 1:1. Further observations of 1 H NMR titration and ESI-MS showed that the possible fluorescent species of Al 3+ with HL was [AlL(OH)(DMSO) 2 ] + in DMSO. The spectroscopic observations of the Al(III) complex showed that the two oxygen atoms and one imine nitrogen atom of HL were coordinated to the Al(III) ion. While the crystal structure of the Ni(II)-L complex confirmed the tridentate coordination mode of HL in the complexes. The experimental results revealed that HL and F − ion formed hydrogen bond in DMSO, while CN − attacked the carbon atom at –C N of HL to undergo a nucleophilic addition. The theoretical calculations confirmed that HL showed very weak fluorescence because of the excited-state intramolecular proton transfer (ESIPT). The turn-on sensing of HL to Al 3+ , F − , and CN − ions arose from the inhibition of ESIPT. MTT tests showed that HL was low toxic to cells. Also, HL could probe intracellular Al 3+ and F − ions by bioimaging. [ABSTRACT FROM AUTHOR]

Abstract: A new coumarin derivative (MS1) containing an imine moiety and a hydroxyl moiety exhibits an enhanced fluorescence in the presence of Hg2+ ions. Other metal ions Al3+, Ca2+, Co2+, Cr3+, Cu2+, Fe2+, Fe3+, Hg2+, K+, Mg2+, Mn2+, Ni2+, Pb2+, and Zn2+ produced only minor changes in the fluorescence values of MS1. The binding ratio of MS1–Hg2+ complexes was determined from the Job plot to be 1:1. The binding constant (K a) of Hg2+ binding to MS1 was found to be 6.85×103 M−1. The maximum fluorescence enhancement caused by Hg2+ binding to MS1 was observed in the pH range of 6.5–9.0. Confocal fluorescence microscopy imaging using RAW 264.7 cells showed that MS1 could be used as an effective fluorescent probe for detecting Hg2+ in living cells. [Copyright &y& Elsevier]

• A fluorescence "turn-on" method was developed for MUC1 detection and targeted cancer imaging. • The specific interaction of MUC1 with its aptamer led to the fluorescence swithching. • Successful detecion of MUC1 in aqueous media was achieved with a detection limit of 0.8 nM. • The method allowed to map the spatial expression of MUC1 in cancer cells with excellent sensitivity. Mucin 1 (MUC1) is an important biomarker that has been shown to participate in the metastasis and invasion of various types of cancers. Simple yet sensitive methods for the detection of MUC1 in liquid and in situ imaging of MUC1 at cellular level are crucial for early diagnosis of cancers as well as monitoring their progression. Herein, a polydiacetylene (PDA) liposome-based sensing system functionalized with Cy3-labeled MUC1 binding aptamer (Cy3-Apt) was developed as a fluorescence "turn-on" nanosensor for the detection of MUC1. In the sensing system, the fluorescence of Cy3-Apt could be directly quenched due to the energy transfer between the fluorogen and PDA conjugated backbone. In the presence of MUC1, the recognition of MUC1 with its aptamer induces the structure switching of both PDA liposomes and the aptamer, recovering the red fluorescence. Sensitive and selective analysis of MUC1 in aqueous media could be achieved with a limit of detection around 0.8 nM. The feasibility of the nanosensor was further demonstrated by mapping the spatial expression of MUC1 in cancer cells with excellent sensitivity. [ABSTRACT FROM AUTHOR]