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Carbon nanodots modified with triethylenetetramine (referred to as TCDs) are shown to be viable fluorescent probes for relay recognition of Cu(II) ion and glutathione (GSH). The assay is based on an 'on-off-on' mechanism where the 'on-off' effect, i.e. quenching by Cu(II) by up to 67%, is exploited to quantify it in concentrations as low as 3.4 nM. The unique quenching of fluorescence (measured at excitation/emission wavelengths of 380/470 nm; quantum yield 16%) is attributed to the fairly selective capture of Cu(II) by the amino and amide groups on the surface of the TCDs. On addition of GSH to the quenched TCD/Cu(II) complex, fluorescence is restored. This effect enables GSH to be quantified in the 0.2 to 175 μM concentration range, with a 0.11 μM detection limit. The turn-on response to GSH is highly selective over other natural amino acids and common anions. Furthermore, the TCDs were successfully applied to image Cu(II) and GSH in living yeast cells. [ABSTRACT FROM AUTHOR]

A new ratiometric fluorescent sensor (DQO) based on N,N′-Di(quinolin-8-yl) oxalamide has been designed and synthesized for selective detection of Zn. The fluorescence ratio ( I / I ) of DQO was enhanced 10-fold when Zn was present in a buffer aqueous solution at pH 8.66. The sensor showed linear response toward Zn in the concentration range 0-15 μM, and the detection limit was calculated to be 2.4 μM. A Job's plot implied the formation of a DQO/Zn complex with 1:1 stoichiometry, and the apparent association constant of DQO/Zn complex was computed to be 1.5 × 10 M. [ABSTRACT FROM AUTHOR]

A new OFF-ON fluorescent chemosensor (H1) composed of a naphthalimide fluorophore and a 6-[(quinolin-8-yloxy)methyl]pyridin-2-ylmethanamine receptor has been synthesized and characterized by infra-red, H NMR, C NMR and mass spectrometry. The developed chemosensor H1 exhibited good turn-on and reversible responses toward Hg, with excellent selectivity and sensitivity, in a neutral buffered aqueous solution. Other common metal ions did not interfere with the fluorescence-enhancement response to Hg. Furthermore, the chemosensor H1, at a concentration of 10 μM, showed a rapid and linear response toward Hg in the concentration range 0-10 μM. On addition of 10 μM Hg, the fluorescence intensity of H1 was enhanced about 4-fold. The detection limit was calculated to be 63 nM. The association constant was 1.11 × 10 M. The fluorescence quantum yield and lifetime of H1/Hg were 0.42 and 3.83 ns, respectively. [ABSTRACT FROM AUTHOR]

Two novel fluorosensors of 4,5-disubstituted-N-alkyl-l,8-naphthalimide derivatives (H1, H2, H3) with double ethylenediamino receptors, double propylenediamino receptors, or one methylpiperazine receptor were synthesized, respectively. Their fluorescence and absorption in the presence or absence of nine metal ions were studied. In the presence of Ag+, H1''s absorption moved to long wavelength with color change from yellow-green to red, its quenching and red shift in fluorescence were also remarkable. Similarly, H1''s fluorescence was also strongly quenched in the presence of Cu2+. In addition, H1 and H2 show high pH sensitively. There was 139-folds fluorescence enhancement for H1, 22-folds for H2, and 4-folds for H3 when pH was changed from 8 to 3, respectively. [Copyright &y& Elsevier]

A novel bicarboxamidoquinoline-based fluorescent sensor 1 was designed and synthesized, which performed ratiometric recognition for Zn 2+ without interference from Cd 2+ . The sensor 1 bound Zn 2+ in 1:1 stoichiometry, with the binding constant of 2.07 × 10 3 M −1 . Moreover, the in situ generated 1 –Zn 2+ complex could serve as an excellent ratiometric citrate sensor via a Zn 2+ displacement and discriminated citrate from a series of common carboxylates in neutral aqueous solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • A highly sensitive Zn2+ and PPi sensor LP was synthesized based on bicarboxaminoquinoline. • LP showed well water solubility, the low LOD, fast response time, and wide linear range for sensing Zn2+ and PPi. • The INHIBIT logic gate was constructed by using the reversibility of LP. • LP was applied for the detection of Zn2+ and PPi in two real water samples and cells imaging. A new ratiometric fluorescent sensor (LP) based on bicarboxaminoquinoline was designed and synthesized for sequentially recognizing Zn2+ and PPi. In aqueous solution, LP exhibited the ratiometric fluorescence response towards Zn2+, along with the about 4-folds enhancement of fluorescence quantum yield. Subsequently, the LP -Zn2+ complex displayed the fluorescence recovery upon adding PPi through the displacement strategy. And the LODs of LP and its Zn2+ complex for sensing Zn2+ and PPi were found to be 15 nM and 5.5 nM, respectively. Notably, the reversibility of LP for sequentially sensing Zn2+ and PPi had been employed to construct the INHIBIT logic gate. Moreover, LP and its Zn2+ complex had been successfully utilized for the detection of Zn2+ and PPi in two real water samples and cells imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • A highly selective Hg2+ sensor QPE was developed based on quinolimide. • QPE had high sensitivity, low LOD and LOQ, wide pH range, and rapid response. • QPE -loaded test strips were fabricated for the visual detection of Hg2+. • QPE had been used for tracing Hg2+ in real water and soil samples and living cells. Herein, a novel fluorescent sensor QPE based on quinolimide was developed, which displayed the highly selective response to Hg2+ through the turn-on signal in aqueous media. The corresponding recognition mechanism of QPE for Hg2+ was investigated by the titration experiments, Job's plots, HRMS, and DFT calculations analysis. QPE could detect Hg2+ in a broad pH range (pH = 4–9) with the LOD of 20 nM and the LOQ of 66 nM. Meanwhile, QPE -loaded test strips were demonstrated in the visual detection of Hg2+. Importantly, QPE exhibited the reliable capability to track Hg2+ in real water and soil samples and yeast cells, indicating that QPE could be used as a prospective tool for monitoring Hg2+ in wide fields. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple FA sensor H2 was developed based on quinolimide for the first time. • H2 had highly selective and sensitive to FA by the pseudo -first-order reaction. • H2 -loaded test strips were fabricated for the visual detection of FA. • H2 had been successfully applied to detect FA in living cells. A simple fluorescent sensor H2 containing quinolimide as a fluorophore and hydrazine as a reaction site was designed and synthesized for the detection of formaldehyde (FA). H2 had the high selectivity and sensitivity to FA through the pseudo -first-order reaction (k = 0.048 min−1), exhibiting the significantly enhanced fluorescence signal. The quantitative determination range of H2 for FA was 0–180 μM, and the LOD of FA is 1.7 μM. Moreover, H2 -loaded test strips were demonstrated in the visualization of sensing FA. And H2 was successfully applied for imaging FA in living cells. [ABSTRACT FROM AUTHOR]

A novel red-emission sulfonamidoquinoline-based derivative ( 2-PyTSQ ) with visible excitation was synthesized as an off-on type fluorescent sensor for distinguishing group IIB cations from common metal ions. When excited at 422 nm, 2-PyTSQ displayed the longer wavelength emission (>600 nm) with a remarkable fluorescence enhancement upon Zn 2+ , Cd 2+ , or Hg 2+ coordination in aqueous solution, respectively. A 2:1 stoichiometry was found for the complexes formed by 2-PyTSQ and these cations. And the binding constants (log Ks ) gradually decreased from 9.45 to 8.96 as ionic radius of group IIB cations increased. Moreover, fluorescence imaging studies revealed that 2-PyTSQ was a cell-permeable and Cd 2+ -responsive reagent in yeast cells. [ABSTRACT FROM AUTHOR]

A novel fluorescent sensor for Zn 2+ based on 8-oxalamidoquinoline (OAQ) was designed and synthesized. OAQ behaves high selectivity to Zn 2+ accompanied by remarkable emission enhancement (32 folds) at 490 nm upon binding Zn 2+ in buffer aqueous solution at pH 7.2. The results show that a 1:1 complex was formed and the apparent association constant of OAQ/Zn 2+ complex was calculated to be 2.5 × 10 5 M −1 . The detection limit was gained to be 2.0 × 10 −8 M. Furthermore, the fluorescent signals of OAQ are utilized to construct an INHIBIT logic gate at the molecular level. Additionally OAQ was successfully used for fluorescence imaging in living yeast cells. [ABSTRACT FROM AUTHOR]

A novel dual fluorophore-based ratiometric Cu 2+ sensor CPC was synthesized via integrating carboxamidoquinoline and coumarin fluorophores. CPC showed high selectivity for Cu 2+ over other metal ions at pH 7.24 in acetonitrile–water solution. The emission produced by carboxamidoquinoline was obviously quenched upon binding Cu 2+ , while the emission produced by coumarin remained almost intact during the whole titration, thus acting as a stable internal standard and validating CPC as a ratiometric sensor. A Job's plot and the MS analysis implied that there was only the formation of a CPC /Cu 2+ complex with 1:1 stoichiometry. [ABSTRACT FROM AUTHOR]

A novel sensor T2 was synthesized through the introduction of N,N -di (pyridin-2-ylmethyl)ethane-1,2-diamine into the quinolimide fluorophore. T2 could detect Cd2+ and Zn2+ via fluorescence enhanced signals, and Cd2+ was distinguished from Zn2+ through the visible color change and the addition of S2−. The T2 -Cd2+ complex exhibited the exceptional selectivity to S2− through the restored fluorescence. Moreover, the combinational logic gate with OR and INHIBIT functions was constructed by using the controlled fluorescence "off-on" states of T2. The recoveries of Cd2+ and Zn2+ in water samples with T2 were in range of 95.6%–106.5%. And T2 was used for the visualization of Cd2+, Zn2+, and S2− in yeast cells. [Display omitted] • The quinolimide-based sensor T2 was developed for sensing Cd2+, Zn2+, and S2−. • T2 could distinguish Cd2+ from Zn2+ through the visible color change and the addition of S2−. • The T2-Cd2+ complex exhibited the exceptional selectivity to S2−. • The combinational logic gate with OR and INHIBIT functions was constructed. • T2 was applied to detect Cd2+, Zn2+, and S2− in water samples as well as in yeast cells. [ABSTRACT FROM AUTHOR]