•Imidazole conjugated quinolone bearing a thiol group (IQT) senses Ag+ sensor via turn on-off mechanism without any influence of other metal ions.•In situIQT-Ag+ complex is utilized as a reversible sensor for Proline by a fluorescence enhancement mechanism as relay recognition process.•The practical applications for sensor IQT is also demonstrated via electrochemical desalination techniques.•A colorimetric kit has been developed and bioimaging studies was carried out by utilizing IQT for the detection of Ag+.A new highly selective fluorescent chemosensor for Ag+ was developed based on an imidazole conjugated quinolone bearing a thiol group (IQT). The Chemosensor serves as fluorescence quencher for Ag+ in solution in the presence of other competing metal ions. Further, the in situ formed IQT-Ag+ complex is utilized as a reversible sensor for the amino acid, Proline with high selectivity over other amino acids by a fluorescence enhancement mechanism as relay recognition process. The practical applications for sensor IQT is also demonstrated by the complete removal of Ag+ ions from the environmental water samples via electrochemical desalination techniques and its bioimaging in cellular micro-organisms.

•A new 2-(2′-hydroxyphenyl)quinazolin-4(3H)-one derived acylhydrazone QP has been developed.•QP exhibits high selectivity to Al3 + through reversible binding.•Al3 + detection by QP displays significant blue-shift and enhanced emission.•QP is applicable to Al3 + detection in real water samples.A new 2-(2′-hydroxyphenyl)quinazolin-4(3H)-one derived acylhydrazone (QP) was designed and synthesized as a fluorescent sensor. In Tris ∙ HCl buffer (10 mM, pH 7.4)/ethanol (1/9, v/v) solution, QP exhibits a highly selective fluorescence response to Al3 + over other metal ions with a significant blue-shifted and enhanced emission at 473 nm. QP interacts with Al3 + reversibly through a 1:2 binding ratio with a detection limit of 4.79 × 10− 8 M. Potential applicability of QP for Al3 + detection in tap and lake water samples were also examined by ‘proof-of-concept’ experiments.A new 2-(2′-hydroxyphenyl)quinazolin-4(3H)-one derived fluorescent sensor for highly selective recognition of Al3 + has been developed.

•A new quinazolin-4(3H)-one derivatized fluorescent probe QBDA was synthesized.•QBDA displays high selectivity to Hg2+ over other metal ions in water solution.•The fluorescence “turn on” response of QBDA to Hg2+ ions is very fast.•QBDA is cell permeable and can detect Hg2+ ions in living cells.A new fluorescence “turn on” Hg2+ probe 3,3′-(((2-hydroxy-5-methyl-3-(4-oxo-3,4-dihydroquinazolin-2-yl)phenyl)methylene)bis(sulfanediyl))dipropionic acid (QBDA) based on Hg2+-triggered transformation of dithioacetal to aldehyde has been developed. Probe QBDA exhibits high selectivity and sensitivity to Hg2+ over other metal ions in PBS buffered (20 mM, pH = 7.4) solution, the detection limit of QBDA for Hg2+ was estimated to be 2.04 × 10−8 M and the potential interference from Ag+ can be suppressed in PBS buffered normal saline solution. Living cell imaging investigations show that QBDA possesses good cell permeability, and can act as a light-up imaging probe for Hg2+ ions in MCF-7 cell.A new fluorescence ‘turn on’ probe QBDA for Hg2+ recognition in water solution with fast response and high sensitivity has been developed.Download high-res image (174KB)Download full-size image

•A new benzothiazole derived NIR emissive fluorescent probe DBT was synthesized.•DBT displays high selectivity and sensitivity to HSO3− in an aqueous solution.•DBT responses to HSO3− through distinct color change and ratiometric fluorescence variations.•DBT is mitochondria targetable and applicable for SO2 detection in living cells.A fluorescent probe (DBT) based on conjugation of 2,3-dimethylbenzo[d]thiazol-3-ium iodide to 3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methylbenzaldehyde for the detection of sulfur dioxide derivatives (HSO3−/SO32−) has been developed. DBT exhibits highly selective colorimetric and ratiometric fluorescence dual response to HSO3− with a fluorescence detection limit of 3.50 × 10−7 M. The HSO3− sensing mechanism was confirmed to undergo nucleophilic addition of HSO3− to alkene double bond of DBT as evidenced by 1H NMR and HRMS analysis. The probe is MCF-7 cell permeable and applicable for fluorescence imaging of exogenous and intrinsically generated intracellular SO2 derivatives in the living cells. Fluorescence co-localization studies reveal that DBT is a mitochondria-targetable fluorescent probe. Thus, DBT has potential application for exploring the role played by SO2 derivatives in biology.Download high-res image (130KB)Download full-size imageA mitochondria-targetable fluorescent probe that display colorimetric and ratiometric fluorescent detection of SO2 derivatives in an aqueous media has been developed.

A novel benzothiazole derived enaminone BTP as a fluorescent probe for CN− recognition has been developed. In DMSO/H2O (95/5, v/v, HEPES 10 mM, pH = 7.4) solution, BTP exhibits high selectivity toward CN− among various anions through colorimetric and fluorescence dual channel changes. On treatment with CN−, BTP displays a blue shifted fluorescence enhancement and a naked eye observable color change from orange to yellow green. Moreover, the CN− sensing event possesses an excellent anti-interference ability over other anions. Sensing mechanism investigations prove that the CN− recognition process undergoes a typical nucleophilic addition of CN− to the enaminone formed BTP. Simple test paper experiments evidenced the practicability of BTP for CN− detection.

•A new 2-(2′-hydroxyphenyl)benzimidazole-based fluorescent probe BIHM has been developed.•BIHM exhibits high selectivity to Hcy over Cys and GSH.•Highly selective recognition of Hcy was achieved through modulating ESIPT.•BIHM is applicable to Hcy detection in living cells.Development of an excited-state intramolecular proton transfer (ESIPT)-based fluorescent probe (BIHM) for selective recognition to homocysteine (Hcy) over glutathione (GSH), cysteine (Cys) and other amino acids is described. The distinctive fluorescence response of BIHM to Hcy over Cys is interpreted by density functional theory calculations. Bioimaging experiments of intracellular Hcy detection manifest the great potential utility of the probe.A simple but effective fluorescent probe for selective detection of homocysteine has been developed through modulating ESIPT.

A new 2,5-diaryl-1,3,4-oxadiazole derived ratiometric fluorescent probe (OXDNP) for hydrogen sulfide recognition has been developed. Probe OXDNP displays highly selective and sensitive detection to HS− over other anions and thiol-containing amino acids in DMSO solution with fast response and a large Stokes shift. Through HS− induced thiolysis of the dinitrophenyl ether, the excited state intramolecular proton transfer (ESIPT) featured precursor was released, which led to dual fluorescence emission ‘turn on’ and ratiometric emission behavior of the sensing system. The pseudo-first-order reaction rate constant was calculated to be 1.234 s−1. The HS− recognition mechanism was proved by HPLC–MS and 1H NMR comparison investigations.A new 2,5-diaryl-1,3,4-oxadiazole-based ratiometric fluorescent probe (OXDNP) for rapid and highly selective recognition of hydrogen sulfide has been developed.

•A 2-(2′-hydroxyphenyl)quinazolin-4(3H)-one derived enaminone QA has been synthesized.•QA displays high selectivity to Pd2 + over other metal ions in water solution.•QA binds Pd2 + through 1:1 binding mode with a low detection limit.•QA is applicable to detect Pd2 + in real water samples and living cells.A 2-(2′-hydroxyphenyl)quinazolin-4(3H)-one derived enaminone (QA) has been developed as a fluorescent probe. In PBS buffered (10 mM, pH = 7.4) water solution, QA displays high selectivity to Pd2 + over other metal ions with a complete fluorescence quenching at 538 nm. Probe QA interacts with Pd2 + through a 1:1 binding stoichiometry with a detection limit of 4.85 × 10− 7 M. Potential applications of QA for Pd2 + detection in real water samples and living cell imaging were also investigated.A 2-(2′-hydroxyphenyl)quinazolin-4(3H)-one derived enaminone (QA) as fluorescent probe for Pd2 + in water solution (PBS 10 mM, pH = 7.4) has been developed.

To develop an effective fluorescent chemosensor for relay recognition of Zn2+ and oxalate, a new fluorescent sensor based on binaphthol-quinoline Schiff base L1 was designed and synthesized. In DMSO-H2O (1/1, v/v, HEPES 10 mM, pH = 7.4) solution, L1 exhibits highly selective fluorescence turn on response to Zn2+ over other metal ions. The Zn2+ recognition event is barely interfered by other coexisting metal ions except Cu 2+, Co 2+ and Ni 2+. The in situ generated L1-Zn\(^{\mathrm {2+}}_{\mathrm {}}\)complex was further used as a chemosensing ensemble for oxalate detection. The complex L1-Zn2+ displays high selectivity to oxalate with significant fluorescence quenching through Zn2+ ion displacement approach. In addition, application of L1 for imaging of Zn2+ and oxalate in living HeLa cells was also examined.

•A new hydroxynaphthyl benzothiazole derived fluorescent probe BTNP has been developed.•BTNP exhibits high selectivity to Cu2 + through Cu2 + catalyzed hydrolysis.•Cu2 + detection by BTNP displays two wavelength enhancements with ratiometric behavior.•BTNP is applicable to Cu2 + detection in living cells and real water samples.A new reactive probe, 1-(benzo[d]thiazol-2-yl)naphthalen-2-yl-picolinate (BTNP), was designed and synthesized. BTNP acts as a highly selective probe to Cu2 + in DMSO/H2O (7/3, v/v, Tris-HCl 10 mM, pH = 7.4) solution based on Cu2 + catalyzed hydrolysis of the picolinate ester moiety in BTNP, which leads to the formation of an ESIPT active product with dual wavelength emission enhancement. The probe also possesses the advantages of simple synthesis, rapid response and high sensitivity. The pseudo-first-order reaction rate constant was calculated to be 0.205 min− 1. Moreover, application of BTNP to Cu2 + detection in living cells and real water samples was also explored.A new fluorescent probe BTNP that exhibits highly selective recognition to Cu2 + in DMSO/H2O (7/3, v/v, Tris-HCl 10 mM, pH = 7.4) solution has been developed.

Selective fluorescence turn on Zn2+ sensor with long-wavelength emission and a large Stokes shift is highly desirable in Zn2+ sensing area. We reported herein the synthesis and Zn2+ recognition properties of a new thiosemicarbazone-based fluorescent sensor L. L displays high selectivity and sensitivity toward Zn2+ over other metal ions in DMSO-H2O (1:1, v/v, HEPES 10 mM, pH = 7.4) solution with a long-wavelength emission at 572 nm and a large Stokes shift of 222 nm. Confocal fluorescence microscopy experiments demonstrate that L is cell-permeable and capable of monitoring intracellular Zn2+.

•A new phenylbenzimidazole derivatized fluorescent sensor L was synthesized.•Sensor L displays high selectivity to Zn2+ ion in water solution with ratiometric fluorescence changes.•The in situ generated L–Zn2+ complex exhibits highly selective recognition to S2−via Zn2+ displacement approach.•Relay recognition of Zn2+ and S2− was achieved through modulating ESIPT.A new phenylbenzimidazole derivatized fluorescent sensor (L) with 2-picolylamine as Zn2+ chaltor was designed and prepared. In buffered water solution (HEPES 10 mM, pH 7.4), sensor L displays highly selective, sensitive and ratiometric fluorescent recognition to Zn2+ based on inhibition of excited-state intramolecular proton transfer (ESIPT). In addition, the resultant L–Zn2+ complex exhibits ratiometric responses to S2− with excellent selectivity via S2− induced Zn2+ displacement approach. The results demonstrate that L can serve as a ratiometric fluorescent sensor for relay recognition of Zn2+ and S2− in water at physiological pH.

•A new phenylbenzimidazole derivatized sensor L has been designed and synthesized.•Sensor L displays relay recognition of Cu2+ and S2− in 100% water solution by fluorescence “on–off–on” functionality.•Sensor L exhibits excited-state intramolecular proton transfer behavior.•The Cu2+ and S2− recognition are highly selective and sensitive.A new 2-(2′-aminophenyl)benzimidazole (2-APBI) derivatized fluorescent sensor (L) that behaves relay recognition of Cu2+ and S2− in water solution (pH 7.4) has been developed. Sensor L displays excited-state intramolecular proton transfer (ESIPT) featured two emission bands and performs highly selective and sensitive recognition to Cu2+ through two emissions simultaneous quenching. The on-site formed L-Cu2+ complex exhibits excellent selectivity to S2− with fluorescence “off–on” response via Cu2+ displacement approach, which exerts ESIPT recovery. Thus, through modulation the ESIPT state of sensor L, relay recognition of Cu2+ and S2− in water has been achieved.The first phenylbenzimidazole based sensor L that exhibits highly selective relay recognition of Cu2+ and S2− in water (HEPES 10 mM, pH = 7.4) has been developed.

A highly selective and sensitive fluorescent Zn2+ sensor N-(2-(benzo[d]thiazol-2-yl)phenyl)-2-((pyridin-2-ylmethyl)amino)acetamide (1) that derived from 2-(2′-aminophenyl)benzothiazole has been developed. In aqueous solution (HEPES/CH3CN=4/6, v/v, HEPES 20 mM, pH = 7.4), sensor 1 displays highly selective recognition to Zn2+ over other metal ions with a distinct longer-wavelength emission enhancement. Sensor 1 binds Zn2+ through its amide form with a 1:1 binding stoichiometry, which switched on the excited-state intramolecular proton transfer (ESIPT).

A new fluorescent 2-(2′-aminophenyl)benzimidazole derivatized sensor BMD was designed and synthesized. In CH3CN/H2O (2:8, v/v, HEPES 10 mM, pH 7.4) solution, sensor BMD displays two emission bands and exhibits a highly selective and ratiometric response to Zn2+ ions with a distinctly longer-wavelength emission blue shifted through the inhibition of the excited-state intramolecular proton transfer (ESIPT) process. BMD can clearly discriminate Zn2+ from Cd2+ and other metal ions. Moreover, the in situ generated BMD-Zn2+ solution exhibits a highly selective and ratiometric response to S2− among various anions and thiol-containing amino acids via Zn2+ displacement approach, which results in a revival of the ESIPT phenomenon of free BMD. These results demonstrate that BMD can serve as a ratiometric sensor for sequential recognition of Zn2+ and S2− in aqueous solution through inhibition and turn-on of ESIPT process.

•A new quinoline derivatized thiosemicarbazone (1) was used as a Cu2 + sensor.•The sensor responses to Cu2 + through fluorescence and color changes.•The in situ formed 1-Cu2 + complex displays high selectivity and sensitivity to S2 −.•Relay recognition of Cu2 + and S2 − through fluorescence ‘on-off-on’ functionality.A new quinoline derivatized thiosemicarbazone (1) was designed and synthesized as a colorimetric and fluorescent sensor. Sensor 1 displays highly selective and sensitive recognition to Cu2 + in aqueous solution (1‰ DMSO, HEPES 20 mM, pH = 7.4) via significant color and fluorescence changes. The on-site generated 1-Cu2 + complex exhibits high selectivity toward S2 − over other anions and thiol-containing amino acids. The Cu2 + and S2 − recognition processes are quick and reversible. Thus, rapid and highly selective relay recognition of Cu2 + and S2 − by sensor 1 in aqueous solution has been achieved.A new quinoline derivatized thiosemicarbazone (1) that displays highly selective and sensitive relay recognition to Cu2 + and S2 − in aqueous solution (1‰ DMSO, HEPES 20 mM, pH = 7.4) has been achieved.

A new bis(8-carboxamidoquinoline) dangled binaphthol derivatized fluorescent sensor (L) was designed and synthesized. L behaves ratiometric response to Zn2+ with high selectivity accompanied by remarkable emission enhancement and red shift. The resultant L–Zn2+ complex can act as a Cu2+ sensing probe with fluorescence quenching behavior through direct Zn2+ ion replacement. Furthermore, the binding modes of Zn2+ and Cu2+ with L are elucidated by X-ray crystallographic analysis, respectively.A new fluorescent sensor (L) that behaves relay recognition toward Zn2+ and Cu2+ through fluorescence ‘off–on–off’ functionality has been described.

A click generated quinoline derivative (1) has been synthesized and used as a fluorescent probe for sequential recognition of Cu2+ and pyrophosphate (PPi) in DMSO/H2O (1:1, v/v, HEPES 20 mM, pH = 7.4) solution. Probe 1 displays high selectivity to Cu2+ ions, and the in-situ prepared probe 1-Cu2+ exhibits high selectivity toward pyrophosphate (PPi) with emission recovery of probe 1. Therefore, 1-Cu2+ complex can be applied as a fluorescence turn-on probe for PPi with high selectivity and sensitivity.A new click generated fluorescent probe for sequential recognition of Cu2+ and pyrophosphate in aqueous media has been developed.

To realize highly selective relay recognition of Cu2+ and sulfide ions, a simple benzimidazole-based fluorescent chemosensor (1) was designed and synthesized. Sensor 1 displays rapid, highly selective and sensitive recognition to Cu2+ in 100% water solution at pH 6.0. The in situ generated 1-Cu2+ complex solution exhibit a fast response and high selectivity toward sulfide anion via Cu2+ displacement approach. The detection limits of sensor 1 to Cu2+ and 1-Cu2+ complex to sulfide anion were estimated to be 3.5 × 10−7 M and 1.35 × 10−6 M, respectively. Proof-of-concept experiment results demonstrate that sensor 1 has potential utilities for Cu2+ and sulfide ion concentration evaluation in real water samples. This successive recognition feature of sensor 1 makes it has a potential utility for Cu2+ and sulfide anion detection in water.We report a simple but effective benzimidazole derivative 1 for rapid, highly selective and sensitive successive recognition of Cu2+ and S2− in 100% water solution at pH 6.0.

A simple carbazole hydrozone derivative(1) was synthesized and used as an optical probe for fluoride recognition in CH3CN. Receptor 1 exhibited colorimetric and fluorescent dual-channel response to fluoride anions. Addition of fluoride to a receptor 1 solution in CH3CN induced a distinct color change from yellow to magenta, the solution also displayed significant fluorescence blue shift. Thus receptor 1 exhibited dual-channel responses to fluoride with a high selectivity and sensitivity.

•Naphthalene based symmetric fluorescent probes sensing Ag+ ion via turn on-off mechanism without any interference of other metal ions.•Sensing behaviours of the probes were explained by heavy atom effect, CN isomerisation and DFT studies.•Colorimetric kits have been developed by utilizing probes 1, 2 and 3 for the detection of Ag+.Naphthalene based salen type fluorescent chemosensors have been designed and synthesized for the highly selective detection of silver ions by fluorimetry. These probes 1, 2 and 3 sense Ag+ over other cations as fluorescence ‘on-off’ behaviour. A possible mechanism is proposed, where the heavy atom effect of silver ion overcomes the effect of CN isomerization and intramolecular restricted torsional rotation through the CC single bond between the naphathalene and the benzene moieties. These chemosensors are further utilized to detect Ag+ as strip tests and solid supported silica gel material. These results are further supported by the theoretical calculations.Download high-res image (154KB)Download full-size image